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Comprehensive Ophthalmology Guide

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1. CATARACT

Definition

Classification

A. Age-Related (Acquired) Cataract - most common

B. Congenital Cataract

• Lamellar (zonular): Most common type - white opacities surrounding nucleus with alternating clear and white cortical lamella ("onion skin")
• Polar: Small anterior or posterior polar opacities; anterior polar usually small and visually insignificant
• Causes: Rubella, Down syndrome, galactosaemia, Lowe syndrome, trauma

C. Secondary/Complicated Cataract

• Metabolic: Diabetes (osmotic swelling; "snowflake" cortical in juvenile DM), galactosaemia, hypocalcaemia (polychromatic lamellar)
• Drug-induced: Systemic corticosteroids (posterior subcapsular), chlorpromazine, amiodarone, busulphan, gold (anterior capsular)
• Radiation: Posterior subcapsular; posterior pole accumulates non-translucent damaged cells
• Ocular disease: Uveitis (PSC), angle-closure glaucoma, high myopia, retinitis pigmentosa
• Trauma: "Rosette" cataract after blunt trauma; Vossius ring (iris pigment on lens after impact)
• Post-vitrectomy: Nuclear sclerosis, especially in patients >50 years
• Silicone oil: Feathering of posterior subcapsular lens; virtually all phakic eyes with silicone oil eventually develop cataract
• Myotonic dystrophy: Fine iridescent "Christmas tree" cortical opacities in 3rd decade → visually disabling by 5th decade

Symptoms

• Reduced visual acuity (initially correctable with spectacles)
• Loss of contrast sensitivity
• Change in colour perception (blue colours particularly affected)
• Glare - difficulty with night driving
• Monocular diplopia
• Difficulty in low-light situations

Investigations

• Slit-lamp biomicroscopy (oblique beam for nuclear, retroillumination for PSC and cortical)
• Red reflex assessment
• Visual acuity and contrast sensitivity testing
• B-scan ultrasound if fundus not visible

Management

• Phacoemulsification (standard): Ultrasound probe fragments and aspirates nucleus through a small incision (~2.4 mm); IOL inserted into capsular bag. Results equivalent to femtosecond laser-assisted surgery.
• ECCE (extracapsular cataract extraction): Used when nucleus too hard for phaco; larger incision
• ICCE (intracapsular): Entire lens including capsule removed; now rarely performed
• IOL (intraocular lens) implantation: Synthetic lens replaces natural lens; standard = posterior chamber IOL in capsular bag
• Femtosecond laser-assisted: Capsulotomy and lens fragmentation prior to phaco; outcomes similar to standard phaco

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2. PTERYGIUM

Definition

Pathogenesis

• UV exposure (main risk factor; occurs in sunny countries)
• Chronic surface dryness
• Familial tendency
• Invades Bowman's layer of the cornea (distinguishing it from pinguicula which does not cross the limbus)

Anatomy of a Pterygium

1. Cap - avascular halo-like zone at the advancing edge
2. Head - apex on the cornea
3. Body - vascularized conjunctival part on the sclera

• Stocker line: linear iron deposition in corneal epithelium anterior to the head
• Fuchs islets: small discrete whitish flecks of pterygial epithelial cells at the advancing edge

Symptoms

• Small lesions: asymptomatic
• Irritation and grittiness (dellen effect at advancing edge - localized drying due to disruption of precorneal tear film)
• Contact lens intolerance
• Visual disturbance (obscuring visual axis, inducing astigmatism)
• Intermittent inflammation (pterygitis)
• Cosmetic concern
• Extensive/recurrent lesions: subconjunctival fibrosis extending to fornices → restricted ocular excursion

Pseudopterygium vs True Pterygium

Treatment

• Lubricating drops/artificial tears
• Topical NSAIDs or mild steroids for inflammation
• UV-blocking sunglasses (advice for all patients)

• Bare sclera excision: Simple excision - high recurrence rate (~80%); not recommended alone
• Conjunctival autografting: Donor conjunctiva from superior/upper-temporal para-limbal region; sutured or glued (fibrin glue, e.g., TISSEEL) into defect - significantly reduces recurrence
• Adjuvant treatment: Mitomycin C (anti-metabolite) or beta-irradiation to reduce recurrence
• Peripheral lamellar keratoplasty: For deep lesions involving stroma

TIP: Recurrence risk is reduced by using conjunctival autograft or applying mitomycin C to the operation site. - Kanski's Clinical Ophthalmology

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3. APHAKIA

Definition

• Primary aphakia: Failure of lens development during embryogenesis (failure of lens placode to form in week 4, or failure of lens induction by optic vesicle). Usually associated with microphthalmia and severe intraocular dysgenesis (retinal dysplasia, corneal opacity). High risk of glaucoma. - The Wills Eye Manual
• Acquired aphakia: Most commonly results from cataract surgery (ICCE - intracapsular cataract extraction) or from traumatic lens dislocation/expulsion

Optical Consequences

• Loss of approximately +10 to +12 dioptres of refracting power
• Severe hypermetropia
• Loss of accommodation (no lens)
• Increased depth of field
• Enlarged retinal image
• Altered colour perception (increased UV transmission without lens filtering)
• Aphakic bullous keratopathy: corneal oedema and blistering

Visual Rehabilitation in Aphakia

1. Aphakic spectacles: +10 to +12D lenses; magnify image ~30% → ring scotoma, jack-in-the-box phenomenon; useful for older children with bilateral aphakia
2. Contact lenses: Superior optical solution for unilateral or bilateral aphakia; preferred in children (compliance worsens after ~age 2)
3. IOL implantation: Now standard; secondary IOL can be implanted even years later if aphakia results from ICCE or trauma

Aphakia as a Risk Factor

• Predisposing condition for retinal detachment (along with high myopia, pseudophakia, lattice degeneration) - The Wills Eye Manual

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4. PSEUDOPHAKIA

Definition

IOL Types

Special IOL Designs

• Monofocal: Corrects for one focal distance; most common
• Multifocal/trifocal: Splits light to correct near, intermediate, and distance
• Extended depth of focus (EDOF): Elongated focal point
• Toric: Corrects astigmatism
• Phakic IOL: Implanted without removing the natural lens (for high refractive errors)

Complications of Pseudophakia

• Posterior capsular opacification (PCO): Most common; "after-cataract"; treated with Nd:YAG laser posterior capsulotomy
• Cystoid macular oedema (Irvine-Gass syndrome)
• Pseudophakic bullous keratopathy: corneal decompensation
• Glare and halos: Particularly with multifocal IOLs; also a cause of glare/halos in the Wills Eye differential
• IOL dislocation/decentration
• Endophthalmitis (infection)
• Retinal detachment: Pseudophakia is a predisposing factor alongside aphakia

Pseudophakia vs Aphakia vs Phakia

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5. CHRONIC DACRYOCYSTITIS

Anatomy Recap

Definition

Pathogenesis

Clinical Features

• Chronic epiphora (watering eye) - the cardinal symptom
• Chronic or recurrent unilateral conjunctivitis
• Mucocoele: painless swelling at the inner canthus (below medial canthal tendon) - the hallmark sign
• If swelling is absent, pressure over the sac produces mucopurulent canalicular reflux (regurgitation test positive)
• Usually painless (contrast with acute dacryocystitis which is painful)

Diagnosis

• Regurgitation test (syringing): reflux of mucopurulent material confirms obstruction
• Dacryocystography (DCG) or dacryoscintigraphy to locate the obstruction
• CT/MRI if neoplasm or dacryolithiasis suspected

Treatment

• Definitive: Dacryocystorhinostomy (DCR) - creation of an anastomosis between the lacrimal sac and nasal mucosa to bypass the obstruction. Can be performed externally (standard) or endonasally (endoscopic).
• Topical/systemic antibiotics: temporary suppression only; do not cure
• Important warning: Postpone any intraocular surgery if there are signs of lacrimal drainage infection - risk of endophthalmitis - Kanski's Clinical Ophthalmology

Complications

• Mucocoele (distended, mucus-filled sac)
• Acute on chronic dacryocystitis
• Sac-skin fistula
• Orbital cellulitis (rare)

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6. CHALAZION

Definition

Pathogenesis

Clinical Features

• Usually painless or mildly tender lid lump
• Located within the tarsal plate (deep to skin), felt as a firm nodule
• May point on the inner (conjunctival) surface of the eyelid
• Subacute to chronic onset (distinguishes from hordeolum)
• Occasionally mild erythema overlying
• Can grow large enough to indent the cornea and cause astigmatism
• Recurrent chalazia in an elderly patient: consider sebaceous gland carcinoma (masquerade lesion)

Chalazion vs Internal Hordeolum

Treatment

• Warm compresses + gentle lid massage: first-line; promotes drainage
• Topical antibiotics (e.g., erythromycin): for secondary infection
• Intralesional corticosteroid injection: triamcinolone; effective for persistent chalazia (caution near medial canthus due to depigmentation risk)
• Incision and curettage (I&C): Under local anaesthetic; lid everted; vertical incision on conjunctival surface; contents curetted; preferred for large or chronic lesions
• Referral: To ophthalmologist at 1-2 weeks if not resolving

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7. CORNEAL OPACITY

Definition

Grades of Corneal Opacity (by density)

Causes

• Sclerocornea (cornea resembles sclera)
• Peter's anomaly (central corneal leucoma with posterior defects)
• Birth trauma (forceps injury)
• Primary aphakia with corneal dysgenesis

• Infective: Bacterial keratitis (Pseudomonas, Staphylococcus, Streptococcus), fungal keratitis, herpetic keratitis (HSV, HZV), Acanthamoeba
• Trachoma: Most common infectious cause of corneal blindness worldwide (Chlamydia trachomatis)
• Vitamin A deficiency: Xerophthalmia → keratomalacia → corneal melting → opacity
• Trauma: Chemical burns, perforating injury
• Exposure keratopathy: Lagophthalmos → drying → secondary infection → scarring
• Interstitial keratitis: Stromal vascularization and scarring (congenital syphilis - "salmon patches" with ghost vessels)
• Corneal dystrophies: Granular, lattice, macular, Fuchs endothelial
• Bullous keratopathy: Aphakic or pseudophakic; repeated epithelial bullae → scarring
• Band keratopathy: Calcium deposition in Bowman's layer (horizontal band); seen with hypercalcaemia, chronic uveitis, extended silicone oil tamponade

Clinical Assessment

• Slit-lamp biomicroscopy
• Corneal topography (assess regularity and induced astigmatism)
• Specular microscopy (endothelial cell count in bullous keratopathy)
• Anterior segment OCT

Treatment

• Spectacles or contact lenses for irregular astigmatism
• Low vision aids

• Penetrating keratoplasty (PK): Full-thickness corneal transplant; for deep/total stromal opacities
• Lamellar keratoplasty (DALK): For stromal opacities with healthy endothelium; preserves host endothelium
• DSAEK/DMEK: For endothelial failure (bullous keratopathy)
• PTK (phototherapeutic keratectomy): Excimer laser ablation; for superficial opacities/anterior stromal scars
• EDTA chelation: For band keratopathy (removes calcium)
• Amniotic membrane transplant: For acute chemical burns to reduce scarring

Complications of Corneal Opacity

• Amblyopia (especially in children with opacities involving visual axis)
• Irregular astigmatism
• Secondary glaucoma (if adhesions involve the angle)
• Nystagmus (if bilateral and early onset)

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8. STYE (HORDEOLUM EXTERNUM)

Definition

Pathogenesis

• Staphylococcal (usually S. aureus) infection of lash follicle
• Spreads to adjacent Zeis (sebaceous) or Moll (sweat) glands
• Forms a localized abscess at the lash line

Clinical Features

• Small pustule at the eyelid margin (at the lash line)
• Pain, swelling, and erythema of the eyelid - usually localized
• Tender nodule at lid margin
• May discharge spontaneously with relief
• Associated with blepharitis (chronic staphylococcal lid margin disease)
• Recurrent styes → investigate for diabetes mellitus

Comparison: External vs Internal Hordeolum vs Chalazion

Treatment

1. Warm compresses: 4-5 times/day, 10-15 minutes each; promotes localization and spontaneous drainage
2. Topical antibiotic ointment: Erythromycin ophthalmic ointment twice daily for 7-10 days
3. Removal of offending eyelash: Can be considered to aid drainage
4. Systemic antibiotics: If significant surrounding cellulitis (preseptal or orbital)
5. Incision and drainage: Refer to ophthalmologist if spontaneous drainage does not occur or if abscess is large
6. Avoid squeezing: May spread infection

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Quick Reference Summary Table

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