PERIMETRY - Comprehensive Guide for MS Ophthalmology

from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.units import cm, mm
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    HRFlowable, PageBreak, KeepTogether
)
from reportlab.lib.enums import TA_CENTER, TA_LEFT, TA_JUSTIFY
from reportlab.platypus import ListFlowable, ListItem
import urllib.request
import os

OUTPUT = "/tmp/workspace/perimetry-pdf/Perimetry_MS_Ophthalmology.pdf"

# ── colour palette ──────────────────────────────────────────────────
NAVY      = colors.HexColor("#1a3a5c")
TEAL      = colors.HexColor("#0d7377")
LIGHT_TEAL= colors.HexColor("#e8f7f8")
GOLD      = colors.HexColor("#c8860a")
LIGHT_GOLD= colors.HexColor("#fdf6e3")
LIGHT_GREY= colors.HexColor("#f5f5f5")
MED_GREY  = colors.HexColor("#888888")
RED_ACCENT= colors.HexColor("#c0392b")
WHITE     = colors.white
BLACK     = colors.black

# ── styles ───────────────────────────────────────────────────────────
base = getSampleStyleSheet()

def S(name, **kw):
    """Helper: clone base Normal and apply kwargs."""
    s = ParagraphStyle(name, parent=base["Normal"], **kw)
    return s

# Main title
TITLE_STYLE = S("DocTitle",
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SUBTITLE_STYLE = S("DocSubtitle",
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# Part header (PART 1 / PART 2)
PART_STYLE = S("PartHeader",
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# Section heading (##)
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# Sub-section heading (###)
H2 = S("H2",
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# Sub-sub heading (####)
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# Body text
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# Bullet body
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    leftIndent=14, bulletIndent=4)

# Pearl box text
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# Caption
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# Source line at bottom of page
SOURCE = S("Source",
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    alignment=TA_CENTER)

# ── helper flowables ─────────────────────────────────────────────────

def h1_block(text):
    """Full-width dark navy banner for section headings."""
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    return tbl

def h2_block(text):
    return Paragraph(text, H2)

def h3_block(text):
    return Paragraph(text, H3)

def body(text):
    return Paragraph(text, BODY)

def bullet_list(items):
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    for item in items:
        paras.append(Paragraph(f"• {item}", BULLET))
    return paras

def pearl_box(text):
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def tip_box(text):
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    return tbl

def warn_box(text):
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        ("RIGHTPADDING",  (0,0), (-1,-1), 10),
        ("BOX",           (0,0), (-1,-1), 1, colors.HexColor("#f5c6cb")),
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    return tbl

def divider():
    return HRFlowable(width="100%", thickness=1, color=colors.HexColor("#dddddd"),
                      spaceAfter=6, spaceBefore=4)

def part_banner(text):
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        ("LEFTPADDING",   (0,0), (-1,-1), 10),
        ("RIGHTPADDING",  (0,0), (-1,-1), 10),
    ]))
    return tbl

def make_table(headers, rows, col_widths=None, alt_rows=True):
    """Build a styled table."""
    head_style = S("TH", parent=base["Normal"],
                   fontSize=9.5, textColor=WHITE, fontName="Helvetica-Bold",
                   alignment=TA_CENTER)
    cell_style = S("TD", parent=base["Normal"],
                   fontSize=9, textColor=BLACK, fontName="Helvetica",
                   alignment=TA_LEFT, leading=13)

    data = [[Paragraph(h, head_style) for h in headers]]
    for row in rows:
        data.append([Paragraph(str(c), cell_style) for c in row])

    if col_widths is None:
        col_widths = [17*cm / len(headers)] * len(headers)

    tbl = Table(data, colWidths=col_widths, repeatRows=1)
    style = [
        ("BACKGROUND",    (0,0), (-1,0), NAVY),
        ("ROWBACKGROUNDS", (0,1), (-1,-1), [LIGHT_GREY, WHITE] if alt_rows else [WHITE]),
        ("GRID",          (0,0), (-1,-1), 0.4, colors.HexColor("#cccccc")),
        ("TOPPADDING",    (0,0), (-1,-1), 5),
        ("BOTTOMPADDING", (0,0), (-1,-1), 5),
        ("LEFTPADDING",   (0,0), (-1,-1), 6),
        ("RIGHTPADDING",  (0,0), (-1,-1), 6),
        ("VALIGN",        (0,0), (-1,-1), "TOP"),
    ]
    tbl.setStyle(TableStyle(style))
    return tbl

# ── cover page ────────────────────────────────────────────────────────

def cover_page():
    elems = []
    # Big title block
    title_data = [[
        Paragraph("PERIMETRY", TITLE_STYLE),
    ]]
    title_tbl = Table(title_data, colWidths=[17*cm])
    title_tbl.setStyle(TableStyle([
        ("BACKGROUND",    (0,0), (-1,-1), NAVY),
        ("TOPPADDING",    (0,0), (-1,-1), 30),
        ("BOTTOMPADDING", (0,0), (-1,-1), 10),
        ("LEFTPADDING",   (0,0), (-1,-1), 20),
        ("RIGHTPADDING",  (0,0), (-1,-1), 20),
    ]))
    elems.append(Spacer(1, 2.5*cm))
    elems.append(title_tbl)

    subtitle_data = [[Paragraph(
        "Comprehensive Guide for MS Ophthalmology<br/>Theory &amp; Practical Examination",
        SUBTITLE_STYLE)]]
    sub_tbl = Table(subtitle_data, colWidths=[17*cm])
    sub_tbl.setStyle(TableStyle([
        ("BACKGROUND",    (0,0), (-1,-1), TEAL),
        ("TOPPADDING",    (0,0), (-1,-1), 14),
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        ("LEFTPADDING",   (0,0), (-1,-1), 20),
        ("RIGHTPADDING",  (0,0), (-1,-1), 20),
    ]))
    elems.append(sub_tbl)
    elems.append(Spacer(1, 1*cm))

    # Quick-reference index
    toc_items = [
        ("PART 1 — THEORY", [
            "1. Definition & Basic Concepts",
            "2. Key Definitions",
            "3. Classification of Perimetry",
            "4. Goldmann Perimetry",
            "5. Standard Automated Perimetry (HFA)",
            "6. HFA Printout Analysis",
            "7. Sources of Error",
            "8. Special Tests",
            "9. Visual Field Defects & Localisation",
            "10. Glaucomatous Field Defects",
            "11. Progression Analysis",
        ]),
        ("PART 2 — PRACTICAL", [
            "12. Confrontation Visual Fields",
            "13. Goldmann Perimetry — Technique",
            "14. HFA Automated Perimetry — Technique",
            "15. Common Exam Scenarios",
            "16. Practical Tips & Viva Pearls",
            "17. Quick Revision Summary",
        ]),
    ]

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            fontSize=11, textColor=NAVY, fontName="Helvetica-Bold",
            spaceBefore=8, spaceAfter=3))
        elems.append(part_p)
        for item in items:
            elems.append(Paragraph(f"&nbsp;&nbsp;&nbsp;• {item}",
                S("TOCItem", parent=base["Normal"],
                  fontSize=10, fontName="Helvetica",
                  spaceBefore=1, spaceAfter=1, textColor=BLACK)))

    elems.append(Spacer(1, 1*cm))
    elems.append(Paragraph(
        "Sources: Kanski's Clinical Ophthalmology 10th Ed | Bradley &amp; Daroff's Neurology in Clinical Practice | Guyton &amp; Hall Physiology",
        SOURCE))
    elems.append(PageBreak())
    return elems

# ── PART 1 CONTENT ────────────────────────────────────────────────────

def part1():
    E = []

    E.append(part_banner("PART 1 — THEORY (Written Examination)"))
    E.append(Spacer(1, 6))

    # ── Section 1
    E.append(h1_block("1. DEFINITION AND BASIC CONCEPTS"))
    E.append(Spacer(1, 4))
    E.append(body(
        "<b>Perimetry</b> is the systematic measurement of <b>differential light sensitivity</b> throughout the "
        "visual field. It maps the 'island of vision' — the three-dimensional representation of visual "
        "sensitivity across the entire visual field."))
    E.append(Spacer(1, 4))
    E.append(h3_block("Extent of the Normal Visual Field"))
    E.append(make_table(
        ["Direction", "Extent"],
        [["Superior", "~50°"], ["Nasal", "~60°"], ["Inferior", "~70°"], ["Temporal", "~90°"]],
        col_widths=[8.5*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 4))
    E.append(body(
        "The peak of the hill corresponds to the <b>fovea</b> (highest sensitivity). "
        "The <b>physiological blind spot</b> ('bottomless pit') lies temporally between 10° and 20°, "
        "slightly below the horizontal meridian, corresponding to the optic disc (no photoreceptors)."))
    E.append(Spacer(1, 4))
    E.append(pearl_box(
        "The nasal slope of the hill of vision is steeper than the temporal slope — reflecting the "
        "asymmetric distribution of retinal ganglion cells."))
    E.append(Spacer(1, 8))

    # ── Section 2
    E.append(h1_block("2. KEY DEFINITIONS"))
    E.append(Spacer(1, 4))
    E.append(make_table(
        ["Term", "Definition"],
        [
            ["Isopter", "A line connecting points of equal sensitivity; encloses an area within which a stimulus of a given strength is visible. Resembles contour lines on a topographic map."],
            ["Scotoma", "An area of reduced ('relative') or total ('absolute') loss of vision surrounded by a seeing area."],
            ["Threshold", "The luminance of a stimulus at a given location which is perceived on 50% of presentations."],
            ["Differential Light Sensitivity (DLS)", "The degree by which luminance of a target must exceed background luminance to be perceived."],
            ["Luminance", "Intensity/brightness of a light stimulus, measured in apostilbs (asb). Higher asb = brighter."],
            ["Decibels (dB)", "Logarithmic unit. 10 dB = 1 log unit. Higher dB = higher retinal sensitivity (INVERSE to stimulus intensity)."],
            ["Mean Sensitivity (MS)", "Average sensitivity across all tested points."],
            ["Suprathreshold", "A stimulus intensity above threshold — definitely visible."],
            ["Background luminance", "Sets retinal adaptation state. HFA uses 31.5 asb (photopic). Goldmann uses 1000 asb."],
        ],
        col_widths=[5*cm, 12*cm]
    ))
    E.append(Spacer(1, 4))
    E.append(h3_block("Decibel Scale — Critical Concept"))
    E.extend(bullet_list([
        "Sensitivity (dB) is INVERSELY related to stimulus intensity (asb)",
        "Higher dB = lower stimulus needed = better retinal sensitivity",
        "Blind spot = 0 dB | Normal fovea ≈ 35 dB | Normal periphery 15–30 dB",
        "Sensitivity decreases by ~1 dB per 10 years after age 20",
        "HFA uses photopic background (31.5 asb) — predominantly cone-mediated",
    ]))
    E.append(Spacer(1, 8))

    # ── Section 3
    E.append(h1_block("3. CLASSIFICATION OF PERIMETRY"))
    E.append(Spacer(1, 4))
    E.append(h2_block("A. By Stimulus Movement"))
    E.append(h3_block("1. Kinetic (Dynamic) Perimetry"))
    E.extend(bullet_list([
        "A stimulus of <b>constant intensity</b> is moved from a non-seeing to a seeing area",
        "The point of first perception is recorded for multiple meridians",
        "Multiple stimulus intensities are used to plot successive <b>isopters</b>",
        "Standard instrument: <b>Goldmann perimeter</b> (manual); also possible with automated perimeters",
        "Best for: full peripheral field, neuro-ophthalmology, non-cooperative patients",
    ]))
    E.append(Spacer(1, 4))
    E.append(h3_block("2. Static Perimetry"))
    E.extend(bullet_list([
        "Stimulus <b>location is fixed</b>; intensity is varied until threshold is reached",
        "More sensitive than kinetic for detecting subtle defects",
        "Usually automated (HFA, Octopus)",
        "<b>Threshold static:</b> determines exact dB threshold at each point — most accurate",
        "<b>Suprathreshold static:</b> tests with a set luminance — faster, screening only",
    ]))
    E.append(Spacer(1, 6))
    E.append(h2_block("B. By Method of Administration"))
    E.append(make_table(
        ["Type", "Details", "Current Use"],
        [
            ["Manual", "Perimetrist presents stimuli by hand; patient gives verbal/motor response", "Limited — cognitively impaired patients, peripheral field assessment"],
            ["Automated (SAP)", "Computer-driven; reproducible, standardized stimuli; statistical analysis", "Routine clinical standard"],
        ],
        col_widths=[3.5*cm, 8*cm, 5.5*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 4
    E.append(h1_block("4. GOLDMANN PERIMETRY (Manual Kinetic)"))
    E.append(Spacer(1, 4))
    E.append(h2_block("Design & Specifications"))
    E.extend(bullet_list([
        "Hemispherical white bowl — background illumination: <b>1000 asb</b> (mesopic)",
        "Examiner operates the instrument and records patient responses manually",
        "Invented by Hans Goldmann in <b>1945</b>",
    ]))
    E.append(Spacer(1, 6))
    E.append(h2_block("Stimulus Notation (Must Memorise)"))
    E.append(make_table(
        ["Component", "Notation", "Description"],
        [
            ["Target Size", "Roman numeral I–V", "I = smallest (1/16 mm²); V = largest (64 mm²)"],
            ["Luminance Filter", "Arabic numeral 1–4", "4 = brightest (no filter)"],
            ["Additional Filter", "Lowercase letter a–e", "e = no additional attenuation (brightest); a = most attenuated"],
            ["Example: V4e", "Largest size, highest luminance, no filter", "Used for full peripheral field mapping"],
            ["Example: I2e", "Smallest size, medium luminance", "Used for central field, small scotomas"],
            ["Example: I4e", "Smallest size, maximum luminance", "Standard central field isopter"],
        ],
        col_widths=[3.5*cm, 5.5*cm, 8*cm]
    ))
    E.append(Spacer(1, 6))
    E.append(h2_block("Advantages vs Disadvantages"))
    E.append(make_table(
        ["Advantages", "Disadvantages"],
        [
            ["Maps FULL visual field (up to 90° temporal)", "Requires skilled, trained perimetrist"],
            ["Excellent for patients with poor central vision", "Time-intensive (~20–30 min/eye)"],
            ["Interactive — perimetrist can adapt to patient", "Operator-dependent variability"],
            ["Superior for peripheral & neurological assessment", "Not easily compared statistically over time"],
            ["Best for suspected non-organic visual loss", "Being replaced by automated methods in many centres"],
        ],
        col_widths=[8.5*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 5
    E.append(h1_block("5. STANDARD AUTOMATED PERIMETRY (HFA)"))
    E.append(Spacer(1, 4))
    E.append(body(
        "<b>Standard Automated Perimetry (SAP)</b> is the routine clinical method. "
        "The <b>Humphrey Field Analyzer (HFA; Carl Zeiss)</b> and <b>Octopus (Haag-Streit)</b> are the most widely used. "
        "Background luminance: 31.5 asb (photopic). Maximum stimulus: 10,000 asb. "
        "Standard target: <b>Goldmann size III</b> (0.43°)."))
    E.append(Spacer(1, 6))
    E.append(h2_block("Testing Patterns"))
    E.append(make_table(
        ["Pattern", "Points Tested", "Field Extent", "Clinical Use"],
        [
            ["24-2", "54 points", "Central 24°", "Standard for glaucoma, neurological"],
            ["30-2", "76 points", "Central 30°", "Neurological, neuro-ophthalmology"],
            ["10-2", "68 points", "Central 10°", "Advanced glaucoma, macular disease"],
            ["Macula", "Dense grid", "Central 4.2°", "Macular pathology"],
            ["Esterman", "Binocular", "Full binocular", "Driving assessment"],
        ],
        col_widths=[2.5*cm, 3*cm, 3*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 6))
    E.append(h2_block("Testing Strategies"))
    E.append(make_table(
        ["Strategy", "Method", "Duration", "Notes"],
        [
            ["Full Threshold (FT)", "4 dB then 2 dB staircase to bracket threshold", "~15 min/eye", "Most accurate; gold standard"],
            ["SITA Standard", "Statistical modelling; adaptive algorithm", "~7 min/eye", "Clinical standard; accuracy ≈ FT"],
            ["SITA Fast", "Faster variant of SITA", "~3–4 min/eye", "Less accurate; for unreliable/elderly"],
            ["SITA SWAP", "Blue stimulus on yellow background", "~8 min/eye", "Tests koniocellular path; detects early glaucoma"],
            ["Suprathreshold", "Fixed suprathreshold stimulus at each point", "~3 min/eye", "Screening only; misses subtle defects"],
        ],
        col_widths=[3*cm, 5*cm, 3*cm, 6*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 6
    E.append(h1_block("6. HFA PRINTOUT ANALYSIS"))
    E.append(Spacer(1, 4))
    E.append(pearl_box(
        "In ALL exams — check RELIABILITY INDICES first before interpreting any HFA printout. "
        "An unreliable test cannot be meaningfully interpreted."))
    E.append(Spacer(1, 6))

    E.append(h2_block("Step 1: Patient & Test Information"))
    E.extend(bullet_list([
        "Confirm: patient name, age, date, eye (OD = right, OS = left)",
        "Test type (e.g. SITA Standard 24-2), corrective lens used, pupil size (must be ≥3 mm)",
        "Time taken, fixation target, background luminance",
    ]))

    E.append(h2_block("Step 2: Reliability Indices"))
    E.append(make_table(
        ["Index", "SITA Limit", "Full Threshold Limit", "Interpretation"],
        [
            ["Fixation Losses (FL)", "<20%", "<20%", "Stimuli projected to blind spot; response = patient moved eye. High FL = poor fixation"],
            ["False Positives (FP)", "<15%", "<33%", "Response without stimulus. High FP = unreliable; grey scale appears PALE"],
            ["False Negatives (FN)", "<15%", "<33%", "No response to supra-threshold stimulus. High FN = fatigue/inattention; grey scale shows CLOVER-LEAF pattern"],
        ],
        col_widths=[3*cm, 2.5*cm, 3*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 4))
    E.append(make_table(
        ["Pattern on Printout", "Reliability Issue"],
        [
            ["Abnormally PALE grey scale", "High False Positives (trigger-happy patient)"],
            ["CLOVER-LEAF grey scale", "High False Negatives (fatigued/inattentive patient)"],
            ["Scattered, random defects", "Poor fixation OR genuinely unreliable responses"],
        ],
        col_widths=[8.5*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 6))

    E.append(h2_block("Step 3: Numerical Display (Sensitivity Values)"))
    E.extend(bullet_list([
        "Each location shows measured/estimated threshold in <b>dB</b>",
        "Numbers in <b>brackets</b> = threshold was re-checked (unexpected >5 dB result)",
        "Values <20 dB = moderate depression; <10 dB = severe; '0' or '<0' = absolute scotoma",
        "Normal foveal sensitivity ≈ 35 dB; decreases with eccentricity",
    ]))

    E.append(h2_block("Step 4: Grey Scale"))
    E.extend(bullet_list([
        "Graphical representation: <b>darker = lower sensitivity</b>",
        "Each shade change ≈ 5 dB",
        "Physiological blind spot = dark area ~15° temporal to fixation, slightly below horizontal",
        "Easy for large defects; can be misleading in unreliable tests — always cross-reference with numbers",
    ]))

    E.append(h2_block("Step 5: Total Deviation (TD) Map"))
    E.extend(bullet_list([
        "Difference between patient's threshold and the <b>age-corrected normal</b> at each point",
        "Negative values = worse than normal; positive = better than normal",
        "<b>Not</b> corrected for diffuse depression (e.g. from cataract)",
        "Shows BOTH focal and diffuse loss",
    ]))

    E.append(h2_block("Step 6: Pattern Deviation (PD) Map"))
    E.extend(bullet_list([
        "TD values corrected for any <b>generalised depression</b> in the overall field",
        "Subtracts the ~85th percentile point — reveals FOCAL/LOCALISED defects",
        "Most useful for detecting early glaucomatous loss",
        "If TD is depressed but PD is clean → likely <b>media opacity (cataract) or miosis</b>",
        "Less useful when there is severe diffuse loss",
    ]))

    E.append(h2_block("Step 7: Probability Plots (TD and PD)"))
    E.append(make_table(
        ["Symbol", "Probability of Abnormality"],
        [
            ["No symbol (blank)", "P > 5% — within normal range"],
            ["Light grey / small square", "P < 5%"],
            ["Medium square", "P < 2%"],
            ["Large square", "P < 1%"],
            ["Solid black square", "P < 0.5% — highly significant"],
        ],
        col_widths=[8.5*cm, 8.5*cm]
    ))

    E.append(h2_block("Step 8: Global Summary Indices"))
    E.append(make_table(
        ["Index", "Definition", "Normal", "Clinical Use"],
        [
            ["Mean Deviation (MD)", "Weighted average deviation from age-matched normal across all points", "0 to –2 dB", "Overall severity; staging glaucoma; monitoring"],
            ["Pattern Standard Deviation (PSD)", "Measure of variability/irregularity relative to normal field shape", "<2 dB", "Elevated = focal loss; suppressed in severe diffuse loss"],
            ["Glaucoma Hemifield Test (GHT)", "Compares mirror-image zones above and below horizontal midline", "Within Normal Limits", "Reports: Within NL / Borderline / Outside NL / Generalised Reduction / Abnormally High Sensitivity"],
            ["Visual Field Index (VFI)", "% of normal visual field remaining; 100% = normal; 0% = total loss", "100%", "Progression monitoring; less affected by cataract than MD"],
        ],
        col_widths=[3*cm, 5.5*cm, 2.5*cm, 6*cm]
    ))
    E.append(Spacer(1, 4))
    E.append(h3_block("Octopus Equivalents"))
    E.append(make_table(
        ["HFA Term", "Octopus Equivalent"],
        [
            ["Mean Deviation (MD)", "Mean Defect (MD)"],
            ["Pattern Standard Deviation (PSD)", "Square Root of Loss Variance (SLV)"],
            ["Mean Sensitivity", "Mean Sensitivity (MS) — average threshold, not deviation"],
        ],
        col_widths=[8.5*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 7
    E.append(h1_block("7. SOURCES OF ERROR IN PERIMETRY"))
    E.append(Spacer(1, 4))
    E.append(h2_block("Patient-Related Errors"))
    E.append(make_table(
        ["Error Source", "Effect on Printout", "Solution"],
        [
            ["Poor fixation", "Generalised scattered loss; high FL", "Remind patient; use gaze tracker; switch to kinetic"],
            ["Ptosis / Dermatochalasis", "Superior field depression (artefact)", "Tape lid up; repeat test"],
            ["Miosis (<2 mm pupil)", "Generalised sensitivity depression", "Dilate with tropicamide; record pupil size"],
            ["Uncorrected refractive error", "Central/paracentral blur artefact", "Correct with trial lens"],
            ["Lens rim artefact", "Peripheral ring scotoma", "Reposition trial lens"],
            ["Cataract / Media opacity", "Generalised TD depression; PD relatively clear", "Note on report; VFI preferred over MD"],
            ["Learning effect", "First test worse than subsequent", "Establish baseline with 2 fields before monitoring"],
            ["Fatigue", "High false negatives; clover-leaf pattern", "Use SITA Fast or suprathreshold; shorter test"],
            ["Inadequate adaptation", "Falsely depressed sensitivity", "Allow 5 min adaptation before testing"],
        ],
        col_widths=[3.5*cm, 6.5*cm, 7*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 8
    E.append(h1_block("8. SPECIAL TESTS IN PERIMETRY"))
    E.append(Spacer(1, 4))
    E.append(make_table(
        ["Test", "Stimulus", "Pathway Tested", "Clinical Use"],
        [
            ["Frequency Doubling Technology (FDT)", "Low spatial frequency grating with high-frequency counter-phase flicker", "Magnocellular (M-cell) pathway", "Early glaucoma screening; quick and portable"],
            ["SWAP (Short Wavelength Automated Perimetry)", "Blue stimulus on bright yellow background", "Koniocellular (K-cell) pathway — small bistratified ganglion cells", "Detects glaucoma 3–5 years before conventional SAP; affected by lens opacity"],
            ["High Pass Resolution Perimetry", "Ring targets based on spatial resolution", "Midget ganglion cells (P-cell)", "Early glaucomatous damage"],
            ["Flicker / Temporal Modulation Perimetry", "Flickering stimuli", "Temporal contrast sensitivity (M-cell)", "Early optic nerve disease, glaucoma"],
            ["Multifocal VEP (mfVEP)", "Flickering dartboard pattern; VEP recording", "Objective — no patient response required", "Non-organic visual loss, medicolegal, paediatric"],
            ["Microperimetry (MP-1, MAIA)", "Static stimuli on fundus image", "Focal macular sensitivity mapped to anatomy", "Macular degeneration, epiretinal membrane, myopic maculopathy"],
        ],
        col_widths=[3.5*cm, 4*cm, 4.5*cm, 5*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 9
    E.append(PageBreak())
    E.append(part_banner("VISUAL FIELD DEFECTS & LOCALISATION"))
    E.append(Spacer(1, 6))
    E.append(h1_block("9. VISUAL FIELD DEFECTS AND THEIR LOCALISATION"))
    E.append(Spacer(1, 4))
    E.append(h2_block("A. Pre-chiasmal Lesions (Retina / Optic Nerve)"))
    E.append(make_table(
        ["Defect", "Lesion Site", "Example Disease"],
        [
            ["Altitudinal defect (horizontal step)", "Optic nerve / retinal artery", "AION, BRAO, glaucoma (inferior arcuate)"],
            ["Centrocecal scotoma", "Optic nerve — papillomacular bundle", "Optic neuritis, toxic optic neuropathy, Leber's LHON"],
            ["Central scotoma", "Macula OR optic nerve", "Macular degeneration, optic neuritis"],
            ["Enlarged blind spot", "Optic disc / peripapillary region", "Papilloedema, myopic optic disc, optic disc drusen"],
            ["Arcuate defect (Bjerrum scotoma)", "Arcuate RNFL fibres at optic nerve head", "Glaucoma (most common)"],
            ["Nasal step (Rönne step)", "Superior or inferior nasal RNFL fibres", "Glaucoma"],
            ["Ring scotoma", "Mid-peripheral retina", "Retinitis pigmentosa"],
            ["Peripheral constriction", "Entire peripheral retina", "Advanced RP, advanced glaucoma"],
            ["Cecocentral scotoma", "Papillomacular bundle connecting disc to macula", "Toxic/nutritional optic neuropathy, LHON, optic neuritis"],
        ],
        col_widths=[5*cm, 5.5*cm, 6.5*cm]
    ))
    E.append(Spacer(1, 6))

    E.append(h2_block("B. Chiasmal Lesions"))
    E.append(make_table(
        ["Defect", "Mechanism", "Example Lesion"],
        [
            ["Bitemporal hemianopia", "Compression of CROSSING nasal fibres at chiasm", "Pituitary adenoma (most common), craniopharyngioma"],
            ["Superior bitemporal defect first", "Inferior chiasmal fibres cross first; pressure from BELOW (adenoma)", "Pituitary macroadenoma"],
            ["Inferior bitemporal defect first", "Superior chiasmal fibres compressed first; pressure from ABOVE", "Craniopharyngioma, suprasellar meningioma"],
            ["Junctional scotoma (Traquair)", "Compression at junction of optic nerve & chiasm: ipsilateral central scotoma + contralateral superior temporal defect", "Pituitary adenoma, meningioma"],
            ["Binasal hemianopia (rare)", "Lateral chiasmal compression of non-crossing temporal fibres", "Bilateral carotid aneurysms, bilateral optic disc disease"],
        ],
        col_widths=[4.5*cm, 7*cm, 5.5*cm]
    ))
    E.append(Spacer(1, 6))

    E.append(h2_block("C. Post-chiasmal Lesions"))
    E.append(make_table(
        ["Defect", "Lesion Site", "Key Features"],
        [
            ["Homonymous hemianopia", "Optic tract, LGN, optic radiation, or occipital cortex", "Affects same side in BOTH eyes"],
            ["Superior quadrantanopia ('pie in the sky')", "Temporal lobe — Meyer's loop (inferior fibres of optic radiation)", "Temporal lobe lesion; usually incongruous"],
            ["Inferior quadrantanopia ('pie on the floor')", "Parietal lobe (superior fibres of optic radiation)", "Parietal lobe lesion"],
            ["Macular-sparing homonymous hemianopia", "Occipital cortex (posterior cerebral artery territory)", "Macular cortex at tip of occipital lobe has dual blood supply; also patient scans toward hemianopic side"],
            ["Congruous homonymous defect", "More posterior (occipital cortex)", "Identical pattern in both eyes — more posterior lesion"],
            ["Incongruous homonymous defect", "More anterior (optic tract)", "Different size/shape in the two eyes — more anterior lesion"],
            ["Homonymous scotoma / quadrantanopia with macular sparing", "Occipital lobe with sparing of macular cortex", "Small cortical lesion; patient may be unaware"],
        ],
        col_widths=[5*cm, 5*cm, 7*cm]
    ))
    E.append(Spacer(1, 4))
    E.append(pearl_box(
        "Key Rule: The more POSTERIOR the post-chiasmal lesion, the more CONGRUOUS the defect "
        "and the more likely it is to show MACULAR SPARING. "
        "Optic tract lesions = incongruous; Occipital lesions = congruous with macular sparing."))
    E.append(Spacer(1, 8))

    # ── Section 10
    E.append(h1_block("10. GLAUCOMATOUS VISUAL FIELD DEFECTS"))
    E.append(Spacer(1, 4))
    E.append(h2_block("Sequence of Glaucomatous Field Loss"))
    E.append(make_table(
        ["Stage", "Field Finding", "Notes"],
        [
            ["1 — Earliest", "Increased variability of threshold responses", "No visible defect yet; statistical measure only"],
            ["2 — Early", "Paracentral scotomas within 10–20° of fixation, often superonasally", "More common in Normal Tension Glaucoma (NTG)"],
            ["3 — Early-Moderate", "Nasal step (Rönne step): asymmetry above/below horizontal midline in nasal field", "Bounded by the horizontal raphe"],
            ["4 — Moderate", "Temporal wedge (less common)", "Similar significance to nasal step"],
            ["5 — Moderate", "Arcuate defect (Bjerrum scotoma): extends from blind spot around fixation", "Between 10–20° of fixation; follows arcuate RNFL bundle"],
            ["6 — Advanced", "Double arcuate / ring scotoma: superior + inferior arcuate defects merge", "Annular scotoma surrounding fixation"],
            ["7 — End-stage", "Small central island + temporal island", "Use 10-2 pattern; monitor VFI carefully"],
        ],
        col_widths=[2.5*cm, 6*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 6))

    E.append(h2_block("Hodapp-Parrish-Anderson (HPA) Criteria for Glaucomatous Damage on SAP"))
    E.append(body("At least ONE of the following on TWO consecutive fields:"))
    E.extend(bullet_list([
        "GHT outside normal limits",
        "A cluster of ≥3 non-edge points, all depressed on PD at P <5%, with at least one at P <1%",
        "Corrected PSD occurring in <5% of normal individuals",
    ]))
    E.append(Spacer(1, 4))

    E.append(h2_block("Staging by Mean Deviation (MD)"))
    E.append(make_table(
        ["Stage", "MD Value", "Clinical Features"],
        [
            ["Early", "MD < –6 dB", "Subtle arcuate defects, nasal step; good central vision"],
            ["Moderate", "MD –6 to –12 dB", "Definite arcuate/ring scotoma; some central involvement"],
            ["Advanced", "MD > –12 dB", "Ring scotoma, small central island; significant disability"],
            ["End-stage", "MD > –20 dB", "Residual central and/or temporal island only"],
        ],
        col_widths=[3*cm, 4*cm, 10*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 11
    E.append(h1_block("11. PROGRESSION ANALYSIS"))
    E.append(Spacer(1, 4))
    E.append(h2_block("Methods of Progression Detection"))
    E.append(make_table(
        ["Method", "Description", "Tool"],
        [
            ["Trend-based (linear regression)", "Linear regression of MD over time; rate = dB/year", "HFA Overview printout; manual calculation"],
            ["Event-based (GPA)", "Compares each field to two baseline fields; flags 'possible' and 'likely' progression", "Guided Progression Analysis (GPA) software on HFA"],
            ["Point-wise linear regression", "Regression at each test point individually; identifies locally progressing points", "PROGRESSOR software; Statpac on HFA"],
        ],
        col_widths=[4*cm, 8*cm, 5*cm]
    ))
    E.append(Spacer(1, 4))
    E.extend(bullet_list([
        "Annual deterioration in untreated glaucoma ≈ just over <b>1 dB MD/year</b> (wide individual variation)",
        "'Likely progression' on GPA requires consistent change on <b>≥3 consecutive fields</b>",
        "At least <b>2 baseline fields</b> should be obtained before monitoring begins",
        "<b>VFI</b> is preferred over MD for progression monitoring as it is less affected by cataract",
        "Rate of progression determines urgency of treatment escalation",
    ]))
    E.append(Spacer(1, 8))

    return E

# ── PART 2 CONTENT ────────────────────────────────────────────────────

def part2():
    E = []
    E.append(PageBreak())
    E.append(part_banner("PART 2 — PRACTICAL EXAMINATION"))
    E.append(Spacer(1, 6))

    # ── Section 12
    E.append(h1_block("12. CONFRONTATION VISUAL FIELDS (Bedside / OSCE)"))
    E.append(Spacer(1, 4))
    E.append(h2_block("Equipment"))
    E.extend(bullet_list([
        "No special equipment required for basic finger confrontation",
        "Ideal: <b>5 mm red target (hat pin)</b> for central field, colour comparison, and scotoma testing",
        "Amsler grid (10×10 cm, held at 33 cm) for central 10° assessment",
    ]))
    E.append(Spacer(1, 6))

    E.append(h2_block("Finger Confrontation — Step by Step"))
    steps = [
        "Sit directly opposite the patient at <b>arm's length (~1 metre)</b>",
        "Ask the patient to cover ONE eye; you cover your OPPOSITE eye (mirror image) — you serve as the normal control",
        "Instruct patient to maintain fixation on your NOSE throughout the test",
        "Bring a waggling finger from the periphery inward in <b>each of the four quadrants</b>",
        "Ask: 'Can you see my finger moving? Tell me when it appears'",
        "Compare your field with the patient's (you are the control)",
        "Repeat for the other eye",
    ]
    for i, s in enumerate(steps):
        E.append(Paragraph(f"{i+1}. {s}", BULLET))
    E.append(Spacer(1, 6))

    E.append(h2_block("Red Hat Pin Testing"))
    E.extend(bullet_list([
        "Hold the 5 mm red target at arm's length; ask if patient can see the red colour",
        "Ask: '<i>Does the red appear the same in both eyes? In all parts of the field?</i>'",
        "Compare colour intensity across the <b>vertical midline</b> (nasal vs temporal halves)",
        "Test for central scotoma: bring from periphery toward centre — does it disappear?",
        "Test for enlarged blind spot: move target outward from the blind spot region",
        "Colour desaturation ('dull red') on one side of the vertical midline suggests a CHIASMAL lesion",
    ]))
    E.append(Spacer(1, 6))

    E.append(h2_block("Specific Confrontation Tests"))
    E.append(make_table(
        ["Test", "Method", "Detects"],
        [
            ["Finger counting", "Hold up different numbers of fingers per quadrant; ask patient to count", "Gross quadrantic defects"],
            ["Simultaneous (double) confrontation", "Present stimuli simultaneously in both hemifields", "Visual inattention / extinction (parietal lobe lesion)"],
            ["Amsler grid", "Patient fixates central dot at 33 cm; examines 10×10 grid", "Central 10°: scotoma, metamorphopsia, line distortion"],
            ["Red desaturation", "Compare intensity of red target across the vertical midline or between eyes", "Relative afferent defect, chiasmal compression, optic neuropathy"],
        ],
        col_widths=[4*cm, 8.5*cm, 4.5*cm]
    ))
    E.append(Spacer(1, 4))
    E.append(h3_block("Amsler Grid — How to Use"))
    E.extend(bullet_list([
        "Hold grid at <b>33 cm</b>; patient wears reading glasses",
        "Ask patient to fix on the central dot with one eye covered",
        "'Can you see all four corners?', 'Are any lines wavy, bent or missing?', 'Is there any area that looks blurred?'",
        "Assess the <b>central 10° (20° arc)</b> in detail",
        "Positive: metamorphopsia → macular disease; scotoma → optic nerve or macular disease",
        "Modified Amsler grids (different patterns) can improve sensitivity",
    ]))
    E.append(Spacer(1, 8))

    # ── Section 13
    E.append(h1_block("13. GOLDMANN PERIMETRY — TECHNIQUE"))
    E.append(Spacer(1, 4))
    E.append(h2_block("Pre-Test Preparation"))
    pre_steps = [
        "Record patient details; confirm eye to be tested",
        "Explain the procedure clearly; demonstrate",
        "<b>Correct refractive error</b> using a trial frame (especially for >5D sphere or >3D cylinder)",
        "<b>Cover the fellow eye</b> with an opaque occluder",
        "Adjust chin rest — pupil should be centred in the aperture",
        "Check <b>pupil size ≥3 mm</b>; dilate with tropicamide 0.5% if necessary",
        "Confirm correct <b>background illumination (1000 asb)</b>",
        "Allow <b>5 minutes of adaptation</b> in the perimetry room",
    ]
    for i, s in enumerate(pre_steps):
        E.append(Paragraph(f"{i+1}. {s}", BULLET))
    E.append(Spacer(1, 6))

    E.append(h2_block("Procedure"))
    proc_steps = [
        "Instruct patient to fixate on the central target and respond immediately when a light is seen",
        "<b>Map the blind spot first</b> using the I4e stimulus — bring it in from different meridians to define its boundaries",
        "Begin with the <b>large bright stimulus (V4e or I4e)</b> for peripheral field",
        "Move to <b>smaller, dimmer stimuli (I2e, I1e)</b> for central field",
        "Move the stimulus at a speed of <b>~2–3°/second</b> from the non-seeing periphery inward",
        "Mark the point where the patient first responds on the chart",
        "Test at least <b>12–15 meridians per isopter</b> (every 15–30°)",
        "Join plotted points to draw the isopter",
        "Repeat for all required stimuli (V4e, I4e, I2e, I1e as indicated)",
        "Map any scotomas by presenting the stimulus within the seeing area and noting where it disappears",
    ]
    for i, s in enumerate(proc_steps):
        E.append(Paragraph(f"{i+1}. {s}", BULLET))
    E.append(Spacer(1, 6))

    E.append(h2_block("Interpreting the Goldmann Chart"))
    E.append(make_table(
        ["Finding", "Interpretation"],
        [
            ["Uniform, well-spaced isopters", "Normal field; each isopter successively smaller and more central"],
            ["Constricted isopters — all stimuli", "Peripheral field loss (RP, advanced glaucoma, non-organic)"],
            ["Flattening / notching of an isopter", "Localised defect in that meridian — note direction and degree"],
            ["No isopter closure around fixation (large scotoma)", "Central scotoma — isopters present peripherally, absent centrally"],
            ["Defect connecting blind spot to fixation area", "Cecocentral scotoma — optic nerve, papillomacular bundle"],
            ["Spiral / star-shaped fields (inconsistent across meridians)", "Non-organic / functional visual loss"],
            ["Fields do not enlarge when testing distance increases", "Non-organic visual loss (normal fields are proportional to distance)"],
        ],
        col_widths=[5.5*cm, 11.5*cm]
    ))
    E.append(Spacer(1, 8))

    # ── Section 14
    E.append(h1_block("14. HFA AUTOMATED PERIMETRY — TECHNIQUE"))
    E.append(Spacer(1, 4))
    E.append(h2_block("Patient Preparation"))
    prep = [
        "Record: name, date of birth, refraction, pupil size",
        "Place appropriate <b>trial lens</b>: add +1.00 D for patients >40 years (presbyopia for 33 cm test distance); use actual near Rx if available",
        "Occlude the fellow eye with an opaque patch",
        "Adjust chin rest height — pupil must be centred in the aperture",
        "Run a <b>practice test</b> first for all new patients",
        "Remind patient: 'Fix on the yellow light in the centre; press the button every time you see a flash of light, even if faint or uncertain'",
    ]
    for i, s in enumerate(prep):
        E.append(Paragraph(f"{i+1}. {s}", BULLET))
    E.append(Spacer(1, 6))

    E.append(h2_block("During the Test"))
    E.extend(bullet_list([
        "Monitor fixation via the <b>Heijl-Krakau method</b> (stimuli projected to blind spot) or <b>gaze tracker</b>",
        "Watch for excessive head movement or eye closure",
        "Stop if patient is clearly exhausted; reschedule — a poor-quality field is worse than no field",
        "Average test time: SITA Standard 24-2 ≈ 6–8 min/eye",
    ]))
    E.append(Spacer(1, 6))

    E.append(h2_block("Printout Interpretation — Systematic Protocol for OSCE/Viva"))
    protocol = [
        "<b>Identify:</b> Patient name, age, date, eye (OD/OS), lens correction, pupil size",
        "<b>Reliability first:</b> FL <20%? FP <15%? FN <15%? — state whether the test is reliable",
        "<b>Grey scale:</b> Identify overall pattern — central, arcuate, altitudinal, hemianopic, diffuse",
        "<b>Numerical display:</b> Note severely depressed points (<10 dB); locate absolute scotomas",
        "<b>Total Deviation:</b> Assess pattern and extent — focal vs diffuse",
        "<b>Pattern Deviation:</b> Identify focal loss after correcting for diffuse depression",
        "<b>Global indices:</b> Report MD, PSD, GHT, VFI — state significance of each",
        "<b>Clinical conclusion:</b> State the type of defect, likely diagnosis, and comparison to previous fields",
    ]
    for i, s in enumerate(protocol):
        E.append(Paragraph(f"{i+1}. {s}", BULLET))
    E.append(Spacer(1, 4))
    E.append(pearl_box(
        "Model OSCE answer: 'This is a reliable right eye HFA SITA Standard 24-2 field. "
        "FL 2/14, FP 1%, FN 4% — all within limits. The grey scale shows a superior arcuate defect. "
        "The pattern deviation confirms this as focal loss. GHT is outside normal limits. "
        "MD is –8.5 dB, PSD is 6.2 dB. Findings are consistent with moderate glaucomatous field loss.'"))
    E.append(Spacer(1, 8))

    # ── Section 15
    E.append(PageBreak())
    E.append(h1_block("15. COMMON EXAM SCENARIOS"))
    E.append(Spacer(1, 4))

    cases = [
        ("Pituitary Adenoma",
         "Bitemporal hemianopia — worse SUPERIORLY initially (inferior chiasmal fibres cross first; upward pressure from below)",
         "Temporal field loss in both eyes respecting the vertical midline",
         "Isopters cut off at/near the vertical midline temporally in BOTH eyes"),
        ("Glaucoma",
         "Arcuate scotoma → nasal step → double arcuate → ring scotoma (late); paracentral scotomas in NTG",
         "Focal PD loss, elevated PSD, abnormal GHT; MD reflects stage",
         "Gradually constricting isopters; nasal step; arcuate defects"),
        ("Retinitis Pigmentosa",
         "Ring scotoma in mid periphery → progressive peripheral constriction; central island preserved until late",
         "Shows central 24–30° only; cannot map full peripheral loss adequately",
         "Severely contracted peripheral isopters; ring scotoma; small residual central field"),
        ("Optic Neuritis",
         "Central scotoma, centrocecal scotoma, or diffuse depression; improves after steroid treatment",
         "Central cluster of depressed points; MD markedly depressed; usually recovers",
         "Central scotoma to all stimuli; isopters may be normal peripherally"),
        ("AION (Arteritic)",
         "Inferior altitudinal defect (superior disc ischaemia most common in GCA); sharp horizontal boundary",
         "Inferior altitudinal loss; abrupt horizontal cut-off",
         "Inferior field absent to all stimuli below the horizontal midline"),
        ("Non-organic Visual Loss",
         "Spiral/star-shaped fields; fields do NOT enlarge with increasing test distance",
         "Scattered unreliable responses; high FP and/or FN; inconsistent patterns across sessions",
         "Spiral fields; marked constriction inconsistent with acuity; fields do not project proportionally"),
    ]

    for name, bedside, hfa, goldmann in cases:
        tbl = Table([
            [Paragraph(f"CASE: {name}", S("CaseName",
                parent=base["Normal"], fontSize=11,
                textColor=WHITE, fontName="Helvetica-Bold", leading=15))],
            [make_table(
                ["Bedside / Confrontation", "On HFA", "On Goldmann"],
                [[bedside, hfa, goldmann]],
                col_widths=[5.5*cm, 5.75*cm, 5.75*cm]
            )],
        ], colWidths=[17*cm])
        tbl.setStyle(TableStyle([
            ("BACKGROUND", (0,0), (0,0), TEAL),
            ("TOPPADDING",    (0,0), (-1,-1), 6),
            ("BOTTOMPADDING", (0,0), (-1,-1), 6),
            ("LEFTPADDING",   (0,0), (-1,-1), 8),
            ("RIGHTPADDING",  (0,0), (-1,-1), 8),
            ("BOX", (0,0), (-1,-1), 1, colors.HexColor("#cccccc")),
        ]))
        E.append(KeepTogether([tbl, Spacer(1, 8)]))

    # ── Section 16
    E.append(h1_block("16. PRACTICAL TIPS & VIVA PEARLS"))
    E.append(Spacer(1, 4))

    pearls = [
        ("Always check reliability FIRST", "State FL, FP, FN values aloud before interpreting any HFA field. An unreliable test should not be reported as showing disease."),
        ("Goldmann stimulus notation", "Roman numeral = size (I–V); Arabic numeral = luminance filter (1–4); letter = additional filter (a–e). V4e = largest, brightest; I1e = smallest, dimmest."),
        ("Physiological blind spot location", "15° temporal to fixation, slightly BELOW the horizontal meridian. Corresponds to the optic disc (no photoreceptors = 0 dB)."),
        ("Pattern Deviation vs Total Deviation", "TD shows ALL depression including diffuse. PD corrects for diffuse, revealing FOCAL loss. In cataract: TD depressed, PD relatively clear."),
        ("GHT significance", "'Outside Normal Limits' on GHT is one of the three HPA criteria for glaucomatous damage."),
        ("VFI vs MD for progression", "VFI is preferred for monitoring glaucoma progression — less affected by cataract than MD."),
        ("When to choose Goldmann over HFA", "Far peripheral field (>30°), poor central vision, cognitive impairment, children, suspected non-organic loss."),
        ("SITA Standard vs SITA Fast", "SITA Standard is more accurate and is the clinical standard. SITA Fast is for elderly, unreliable, or fatigued patients."),
        ("Learning effect", "First HFA field is often worse — always establish baseline with 2 fields before using them for comparison."),
        ("Ptosis artefact", "Tape the lid up and repeat if superior field depression is noted — it may be artefactual, not real."),
        ("Non-organic visual loss fields", "Look for spiral fields on Goldmann, inconsistency between visits on HFA, and fields that don't expand with distance. mfVEP is objective confirmation."),
        ("Macular sparing in hemianopia", "Preserved central vision in occipital lobe infarction due to dual blood supply of the macular cortex (MCA + PCA). Also aided by patient scanning toward the hemianopic field."),
        ("Congruity rule", "Optic TRACT lesions = INCONGRUOUS hemianopia. Occipital CORTEX lesions = CONGRUOUS hemianopia ± macular sparing."),
        ("Junctional scotoma", "Ipsilateral central scotoma + contralateral superior temporal defect. Lesion at junction of optic nerve and chiasm."),
        ("Nasal step mechanism", "Due to the horizontal raphe separating superior and inferior arcuate bundles. Defect is bounded by the horizontal midline in the nasal field."),
    ]

    for i, (title, detail) in enumerate(pearls):
        tbl = Table([
            [Paragraph(f"{i+1}. {title}", S("PearlTitle",
                parent=base["Normal"], fontSize=10,
                textColor=NAVY, fontName="Helvetica-Bold", leading=14)),
             Paragraph(detail, BODY)],
        ], colWidths=[5*cm, 12*cm])
        tbl.setStyle(TableStyle([
            ("BACKGROUND", (0,0), (0,0), LIGHT_TEAL),
            ("TOPPADDING",    (0,0), (-1,-1), 5),
            ("BOTTOMPADDING", (0,0), (-1,-1), 5),
            ("LEFTPADDING",   (0,0), (-1,-1), 6),
            ("RIGHTPADDING",  (0,0), (-1,-1), 6),
            ("VALIGN",        (0,0), (-1,-1), "TOP"),
            ("BOX",           (0,0), (-1,-1), 0.5, colors.HexColor("#cccccc")),
        ]))
        E.append(tbl)
        E.append(Spacer(1, 3))

    E.append(Spacer(1, 8))

    # ── Section 17
    E.append(PageBreak())
    E.append(h1_block("17. QUICK REVISION SUMMARY"))
    E.append(Spacer(1, 4))

    E.append(h2_block("Goldmann vs HFA — Comparison"))
    E.append(make_table(
        ["Feature", "Goldmann Perimetry", "HFA (SAP)"],
        [
            ["Stimulus type", "Kinetic — moving, constant intensity", "Static — fixed location, varying intensity"],
            ["Field extent", "Full field (up to 90° temporal)", "Central 24–30° (standard)"],
            ["Background luminance", "1000 asb (mesopic)", "31.5 asb (photopic)"],
            ["Operator", "Skilled perimetrist required", "Automated; minimal supervision"],
            ["Reproducibility", "Lower; operator-dependent", "High; computer-controlled"],
            ["Statistical comparison", "Difficult", "Excellent (GPA, VFI, trend analysis)"],
            ["Best for", "Full peripheral, neuro, non-cooperative", "Glaucoma monitoring, neurological fields"],
            ["Duration", "20–30 min/eye", "6–8 min/eye (SITA Standard)"],
        ],
        col_widths=[4*cm, 6.5*cm, 6.5*cm]
    ))
    E.append(Spacer(1, 6))

    E.append(h2_block("HFA Indices Quick Reference"))
    E.append(make_table(
        ["Index", "What it Measures", "Abnormal Value", "Interpretation"],
        [
            ["MD", "Mean deviation from age-matched normal", "< –2 dB", "Overall severity; negative = worse"],
            ["PSD", "Field irregularity / focal loss", "> 2 dB", "High = focal defect; low in diffuse/advanced loss"],
            ["GHT", "Superior vs inferior hemifield asymmetry", "Outside Normal Limits", "Asymmetry = glaucoma suspect"],
            ["VFI", "% of normal field remaining", "< 100%", "Used for progression rate; less affected by cataract"],
            ["FL", "Fixation steadiness", "> 20%", "Unreliable test"],
            ["FP", "Trigger-happy responses", "> 15% (SITA)", "Unreliable; pale grey scale"],
            ["FN", "Missed supra-threshold stimuli", "> 15% (SITA)", "Fatigue/inattention; clover-leaf grey scale"],
        ],
        col_widths=[1.8*cm, 4.5*cm, 3.5*cm, 7.2*cm]
    ))
    E.append(Spacer(1, 6))

    E.append(h2_block("Visual Field Defects — Localisation at a Glance"))
    E.append(make_table(
        ["Defect", "Site of Lesion"],
        [
            ["Central scotoma", "Macula OR optic nerve (papillomacular bundle)"],
            ["Altitudinal defect", "Optic nerve (AION) or retinal artery (BRAO)"],
            ["Arcuate (Bjerrum) scotoma + nasal step", "Optic nerve head — glaucoma"],
            ["Ring scotoma / peripheral constriction", "Peripheral retina — retinitis pigmentosa"],
            ["Bitemporal hemianopia", "Optic chiasm (pituitary adenoma / craniopharyngioma)"],
            ["Junctional scotoma", "Junction of optic nerve and chiasm"],
            ["Homonymous hemianopia — INCONGRUOUS", "Optic tract (anterior post-chiasmal)"],
            ["Superior quadrantanopia ('pie in sky')", "Temporal lobe (Meyer's loop)"],
            ["Inferior quadrantanopia ('pie on floor')", "Parietal lobe"],
            ["Homonymous hemianopia — CONGRUOUS + macular sparing", "Occipital cortex (posterior cerebral artery)"],
        ],
        col_widths=[8.5*cm, 8.5*cm]
    ))
    E.append(Spacer(1, 8))

    E.append(Paragraph(
        "Sources: Kanski's Clinical Ophthalmology 10th Ed (Chs 1 &amp; 11) | "
        "Bradley &amp; Daroff's Neurology in Clinical Practice (Chs 16 &amp; 43) | "
        "Guyton &amp; Hall Textbook of Medical Physiology",
        SOURCE))

    return E

# ── Build the PDF ──────────────────────────────────────────────────────

def header_footer(canvas, doc):
    canvas.saveState()
    w, h = A4
    # Header
    canvas.setFillColor(NAVY)
    canvas.rect(0, h - 28, w, 28, fill=1, stroke=0)
    canvas.setFont("Helvetica-Bold", 9)
    canvas.setFillColor(WHITE)
    canvas.drawString(1.5*cm, h - 19, "PERIMETRY — MS Ophthalmology Guide")
    canvas.drawRightString(w - 1.5*cm, h - 19, "Theory & Practical")
    # Footer
    canvas.setFillColor(NAVY)
    canvas.rect(0, 0, w, 22, fill=1, stroke=0)
    canvas.setFont("Helvetica", 8)
    canvas.setFillColor(WHITE)
    canvas.drawString(1.5*cm, 7, "Kanski's Clinical Ophthalmology 10th Ed | Bradley & Daroff's Neurology | Guyton & Hall Physiology")
    canvas.drawRightString(w - 1.5*cm, 7, f"Page {doc.page}")
    canvas.restoreState()

def build():
    doc = SimpleDocTemplate(
        OUTPUT,
        pagesize=A4,
        topMargin=1.6*cm,
        bottomMargin=1.5*cm,
        leftMargin=2*cm,
        rightMargin=2*cm,
        title="Perimetry — MS Ophthalmology",
        author="Orris Medical AI",
        subject="Perimetry: Theory & Practical Guide",
    )

    story = []
    story.extend(cover_page())
    story.extend(part1())
    story.extend(part2())

    doc.build(story, onFirstPage=header_footer, onLaterPages=header_footer)
    print(f"PDF created: {OUTPUT}")

build()

Successfully replaced 1 instance(s) of the string in '/tmp/workspace/perimetry-pdf/generate_pdf.py'