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Ophthalmology Workshop - All 10 Topics: Detailed Descriptions

This workshop covers the following topics from an Ophthalmology Workshop at a medical college. Here is a detailed description of each, with references to standard textbooks.

1. Know the Glasses (Optics & Spectacle Correction)

Spectacle lenses correct refractive errors by bending light to focus it precisely on the retina. The four major categories are:

Convex (plus) lenses - converge light rays; used for hypermetropia (farsightedness) and presbyopia
Concave (minus) lenses - diverge light rays; used for myopia (nearsightedness)
Cylindrical lenses - correct astigmatism (unequal curvature of the cornea)
Bifocal/Progressive lenses - provide correction at multiple distances, used in presbyopia

Key parameters on a prescription:

SPH (Sphere): degree of myopia/hyperopia in diopters
CYL (Cylinder): astigmatism correction
AXIS: orientation of the cylinder in degrees (0-180)
ADD: additional power for near vision (presbyopia)

A prismatic lens is added to correct diplopia or strabismus. The power of a lens in diopters = 1 / focal length in metres.

Reference: Kanski's Clinical Ophthalmology, 10th Ed. - Chapter on Refraction and Optics

2. Anterior Segment Examination

The anterior segment includes the cornea, iris, lens, anterior chamber, and drainage angle. The primary tool is the slit lamp biomicroscope.

Systematic slit-lamp examination covers:

Structure	What to look for
Eyelids/Lashes	Blepharitis, entropion, ectropion
Conjunctiva	Injection, follicles, papillae, discharge
Cornea	Clarity, vascularization, ulcers, fluorescein staining
Anterior Chamber	Depth, Tyndall effect (flare/cells indicating uveitis)
Iris	Pupil shape, synechiae, rubeosis
Lens	Clarity, nuclear sclerosis, cortical/posterior subcapsular cataract

Additional techniques:

Fluorescein staining - highlights epithelial defects (stains green under cobalt blue light)
Van Herick method - estimates anterior chamber angle width
Gonioscopy - direct visualisation of the drainage angle
Pachymetry - corneal thickness measurement

Reference: Kanski's Clinical Ophthalmology, 10th Ed., Chapter 1; The Wills Eye Manual, 7th Ed.

3. Cataract Surgery on Goat Eye

Cataract surgery is the most commonly performed elective surgery worldwide. The goat eye is an ideal model for practice due to its similarity to the human eye in size and lens structure.

Modern technique - Phacoemulsification ("Phaco"): This is the standard method in high-income countries. Key steps:

Clear corneal incision (~2.2-2.8 mm) or scleral tunnel incision
Viscoelastic injection - to maintain the anterior chamber and protect the endothelium
Capsulorhexis - continuous circular tear of the anterior lens capsule (the most technically demanding step)
Hydrodissection - fluid wave separates cortex from capsule
Phacoemulsification - ultrasonic probe emulsifies and aspirates the lens nucleus
Cortex aspiration - removes remaining soft cortical material
IOL implantation - foldable intraocular lens placed into the capsular bag

Older technique - ECCE (Extracapsular Cataract Extraction): A large limbal incision (8-10 mm) is made and the nucleus is expressed whole. Manual small-incision cataract surgery (MSICS) is a variant used in high-volume, resource-limited settings.

The donor button in keratoplasty vs. IOL placement:

IOL power is calculated using biometry (A-scan ultrasound or optical coherence biometry) using the SRK/T formula for standard eyes

Reference: Kanski's Clinical Ophthalmology, 10th Ed., pp. 396-420 (Chapter 10 - Cataract); Miller's Anesthesia, 10th Ed. - Preoperative Evaluation for Cataract Surgery

4. Posterior Segment Examination

The posterior segment comprises the vitreous, retina, choroid, and optic nerve. Examination techniques include:

Direct Ophthalmoscopy:

Provides a magnified (15x), upright, monocular image
Good for optic disc and macula assessment in primary care

Indirect Ophthalmoscopy:

Uses a condensing lens (20D, 28D) held in front of a light source worn on the head
Gives a wide-field, inverted, stereoscopic view
Essential for peripheral retina examination and in children

Slit-lamp with fundus lens (78D / 90D lens):

Best for detailed examination of the optic disc, macula, and posterior pole
Higher magnification than indirect

Fundus Fluorescein Angiography (FFA):

Intravenous fluorescein dye maps retinal and choroidal vasculature
Detects leakage (macular oedema), ischaemia (non-perfusion), and neovascularization

OCT (Optical Coherence Tomography):

Cross-sectional imaging of retinal layers at micron resolution
Gold standard for macular disease (AMD, diabetic macular oedema, macular hole)

Reference: Kanski's Clinical Ophthalmology, 10th Ed., Chapter 13 (Medical Retina); The Wills Eye Manual, 7th Ed.

5. Glaucoma Evaluation

Glaucoma is a collection of diseases characterized by optic neuropathy, usually associated with elevated intraocular pressure (IOP). It is the leading cause of irreversible blindness worldwide.

Pathophysiology (from Robbins & Kumar Basic Pathology): Aqueous humor is produced by the ciliary body, flows from the posterior chamber through the pupil into the anterior chamber, and drains primarily through the trabecular meshwork into Schlemm's canal. Impaired drainage raises IOP, causing mechanical and ischaemic optic nerve damage.

Classification:

Primary Open-Angle Glaucoma (POAG) - most common; open angle, gradual painless vision loss, normal-looking angle on gonioscopy
Primary Angle-Closure Glaucoma (PACG) - iris blocks aqueous outflow; can present acutely with pain, redness, and haloes around lights
Normal-Tension Glaucoma - optic nerve damage with IOP within statistical normal range
Secondary Glaucomas - neovascular (from DR, CRVO), pigment dispersion, pseudoexfoliation

Complete glaucoma evaluation includes:

Test	Purpose
Goldmann Applanation Tonometry	Gold standard IOP measurement
Pachymetry	Central corneal thickness (corrects IOP values)
Gonioscopy	Angle assessment - open vs. closed
Optic disc assessment (slit lamp + 78D)	Cup-to-disc ratio, RNFL defects, disc haemorrhages
Visual Field Testing (Humphrey/Goldmann perimetry)	Detect characteristic arcuate scotomas
OCT - Retinal Nerve Fibre Layer (RNFL)	Earliest structural glaucoma changes

Reference: Robbins & Kumar Basic Pathology, p. 868-870; Goldman-Cecil Medicine International Edition; Kanski's Clinical Ophthalmology, 10th Ed., Chapter 11

6. Diabetic Retinopathy Evaluation

Diabetic retinopathy (DR) is the commonest cause of new blindness in most industrialised countries. Prevalence in type 2 DM is ~67% at 10 years after diagnosis; 10% will have proliferative disease.

Classification (ETDRS-based):

Non-Proliferative DR (NPDR):

Mild: microaneurysms only
Moderate: microaneurysms, dot-blot haemorrhages, hard exudates, cotton-wool spots
Severe: "4-2-1 rule" - haemorrhages in 4 quadrants, or venous beading in 2 quadrants, or intraretinal microvascular abnormalities (IRMA) in 1 quadrant

Proliferative DR (PDR):

New vessels on disc (NVD) or elsewhere on retina (NVE)
Vitreous haemorrhage, tractional retinal detachment

Diabetic Maculopathy:

Clinically significant macular oedema (CSMO) - the main cause of visual impairment in type 2 DM
Detected by OCT and FFA

Evaluation protocol:

Best-corrected visual acuity (BCVA)
Dilated fundoscopy (slit lamp + 78D or indirect ophthalmoscope)
OCT macula - quantify oedema
FFA - map ischaemia, guide laser treatment
Systemic assessment: HbA1c, BP, renal function, lipids

Treatment milestones: ETDRS showed panretinal photocoagulation (PRP) reduces severe visual loss in PDR by 50%. Anti-VEGF therapy (ranibizumab, aflibercept, bevacizumab) is first-line for diabetic macular oedema.

Reference: Kanski's Clinical Ophthalmology, 10th Ed., pp. 506-523 (Chapter 13 - Diabetic Retinopathy); Harrison's Principles of Internal Medicine, 22nd Ed.

7. Colour Vision

Colour vision depends on three types of cone photoreceptors (L, M, S - long, medium, short wavelength) in the fovea, mediated by the opponent-colour processing system.

Physiology:

Cones are concentrated in the fovea (central 5 degrees)
L-cones (red/long ~560 nm), M-cones (green/medium ~530 nm), S-cones (blue/short ~430 nm)
Colour perception relies on the relative stimulation of these three cone types

Colour Vision Defects:

Type	Description	Prevalence
Deuteranopia	Green-blindness (M-cone absent)	~1% males
Protanopia	Red-blindness (L-cone absent)	~1% males
Tritanopia	Blue-blindness (S-cone absent)	Very rare
Deuteranomaly	Most common; reduced green sensitivity	~5% males
Achromatopsia	Total colour blindness	Very rare

X-linked inheritance explains male predominance (8% males vs 0.5% females affected).

Testing Methods:

Ishihara Plates - most widely used; screens for red-green defects (as seen in the workshop poster image)
Hardy-Rand-Rittler (HRR) plates - detects blue-yellow defects too
Farnsworth-Munsell 100-Hue test - precise quantification and classification
Farnsworth D-15 test - quick dichotomous test for severity
Anomaloscope - gold standard for diagnosis and classification

Clinical importance:

Congenital: usually X-linked red-green deficiency
Acquired: optic nerve disease (blue-yellow deficiency common), macular disease, drug toxicity (chloroquine, digoxin)

Reference: Kanski's Clinical Ophthalmology, 10th Ed., Chapter 1 (Visual Function Testing)

8. Computer Vision Syndrome (CVS) / Dry Eye Examination

Computer Vision Syndrome (CVS) is a complex of eye and vision problems resulting from prolonged digital screen use. It is now also termed Digital Eye Strain.

Pathophysiology: Prolonged screen use leads to:

Reduced blink rate (from ~15 blinks/min to ~5 blinks/min), causing tear film instability
Increased upward gaze (larger palpebral aperture, more ocular surface exposed)
Uncorrected or under-corrected refractive error causing asthenopia
Blue light (400-450 nm) emission causing photochemical stress

Symptoms of CVS:

Eyestrain, headache, blurred vision (near and/or distance)
Dry, irritated, red eyes
Neck and shoulder pain

Dry Eye Disease (DED) - The Wills Eye Manual classification:

Severity	Features	Treatment
Mild	Mild symptoms, minimal signs	Artificial tears q.i.d. (preservative-free preferred)
Moderate	Symptoms affect daily activities	Preservative-free tears q1-2h; cyclosporine 0.05-0.09% b.i.d.; lifitegrast 5% b.i.d.; punctal plugs
Severe	Severe symptoms, corneal involvement	All of above + moisture chamber, autologous serum tears, scleral lens, tarsorrhaphy

Dry Eye Examination Protocol (DEWS II):

Symptom questionnaires (OSDI, SPEED)
Non-invasive tear break-up time (NIBUT) - normal >10 seconds
Tear meniscus height (TMH) by OCT
Fluorescein corneal staining
Lissamine green conjunctival staining
Schirmer's test (strip placed in lower fornix) - measures aqueous production:
- Without anaesthesia (Schirmer I): normal >10 mm at 5 min
- With anaesthesia (basic secretion test): normal >5 mm

Management of CVS:

20-20-20 rule: every 20 minutes, look at an object 20 feet away for 20 seconds
Reduce screen brightness, use blue-light filter glasses
Optimize screen distance (~50-70 cm) and angle (slightly below eye level)

Reference: The Wills Eye Manual, 7th Ed., pp. 174-176; Goldman-Cecil Medicine, Dry Eye section

9. Keratoplasty (Corneal Transplantation)

Keratoplasty is the surgical replacement of diseased corneal tissue with donor cornea. It is the most commonly performed tissue transplantation worldwide.

Types of Keratoplasty:

Type	Indication	Technique
Penetrating Keratoplasty (PK)	Full-thickness corneal disease (e.g., post-herpetic scarring, keratoconus with hydrops)	Full-thickness 7-8 mm trephination; replaced with donor button ~0.25 mm larger
Deep Anterior Lamellar Keratoplasty (DALK)	Stromal disease with healthy endothelium (keratoconus, stromal scars)	Replaces stroma + epithelium, preserves host endothelium; avoids rejection risk to endothelium
Descemet Stripping Automated Endothelial Keratoplasty (DSAEK)	Endothelial disease (Fuchs endothelial dystrophy, pseudophakic bullous keratopathy)	Posterior lamellar graft; faster recovery than PK
Descemet Membrane Endothelial Keratoplasty (DMEK)	Same as DSAEK; thinner graft, better visual outcome	Descemet membrane + endothelium only

Penetrating Keratoplasty - Key surgical points (Kanski's):

Common graft size: 7.5 mm; smaller grafts cause high astigmatism
Donor button prepared before host trephination (safety principle)
Secured with continuous or interrupted suture techniques

Postoperative management:

Topical steroids (prednisolone acetate 1%) tapered over months-years to prevent rejection
Cyclosporine/azathioprine for high-risk cases
Oral acyclovir if pre-existing herpes simplex keratitis
Suture removal at 12-18 months (when junction healed)
IOP monitoring by non-applanation method initially

Rejection:

Immune-mediated attack on donor endothelium is the main threat to long-term graft survival
Prophylactic oral aciclovir (400 mg twice daily) improves graft survival in herpetic eye disease

Reference: Kanski's Clinical Ophthalmology, 10th Ed., pp. 280-295 (Chapter 8 - Cornea)

10. Eye Donation

Eye donation is the voluntary donation of eyes after death for use in corneal transplantation, research, and education. It is the only source of donor tissue for keratoplasty.

Key facts:

One donor can restore sight to two corneal blindness patients
Corneas can be retrieved up to 6 hours after death (extended to 12 hours with body refrigeration)
Corneas are stored in McCarey-Kaufman (MK) medium (short-term, ~4 days) or organ culture medium (long-term, up to 28 days)
India is among countries with the highest burden of corneal blindness (~6.8 million people)

Contraindications to corneal donation:

Absolute: HIV, hepatitis B/C, rabies, Creutzfeldt-Jakob disease (CJD), septicemia, unknown cause of death
Relative: previous refractive surgery (PRK, LASIK) - tissue unsuitable for PK but can be used for research

Who can donate:

Any age (even neonates and very elderly can donate)
Spectacle wearers, diabetics, hypertensives are all eligible
Consent from next of kin is required (in most countries)

Process:

Death certification
Notification of eye bank within 6 hours
Enucleation or in situ corneoscleral disc excision
Storage and quality testing (specular microscopy for endothelial cell count - minimum ~2000 cells/mm²)
Allocation to waiting recipient (FIFO or match-based)
Transplantation within preservation period

Legal framework (India): The Transplantation of Human Organs and Tissues Act (THOTA), 1994 (amended 2011) governs eye donation. The National Eye Bank and state-level eye banks coordinate procurement.

Reference: Kanski's Clinical Ophthalmology, 10th Ed. - Corneal chapter; WHO Guidelines on Tissue Banking

Summary Reference Table

Topic	Primary Standard Reference
Know the Glasses	Kanski's Clinical Ophthalmology, 10th Ed.
Anterior Segment Examination	Kanski's; Wills Eye Manual, 7th Ed.
Cataract Surgery	Kanski's Clinical Ophthalmology, 10th Ed.
Posterior Segment Examination	Kanski's; Wills Eye Manual, 7th Ed.
Glaucoma Evaluation	Robbins & Kumar Basic Pathology; Goldman-Cecil Medicine; Kanski's
Diabetic Retinopathy	Kanski's; Harrison's Principles of Internal Medicine, 22nd Ed.
Colour Vision	Kanski's Clinical Ophthalmology, 10th Ed.
CVS / Dry Eye	Wills Eye Manual, 7th Ed.; DEWS II Guidelines
Keratoplasty	Kanski's Clinical Ophthalmology, 10th Ed.
Eye Donation	WHO Guidelines; National Eye Bank India

All topics are well covered in Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition (Salmon & Bowling) - the single most recommended textbook for this workshop. For clinical management specifics, The Wills Eye Manual, 7th Edition is the best quick-reference companion.

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