Ocular Oncology, Pathology and General/Community Ophthalmology
Ocular Oncology
Concept anchors
Intraocular tumors divide into those in children and adults. Retinoblastoma presents with leukocoria or strabismus, is caused by biallelic RB1 mutation, and about 40% of cases are heritable with germline mutation, risk of bilateral disease and secondary tumors. Management is by specialist centres using chemoreduction, focal therapy, brachytherapy or enucleation; enucleation specimens show Flexner-Wintersteiner rosettes. Screening of at-risk children and genetic counselling are essential.
Adult tumors
Uveal melanoma arises from choroidal melanocytes; features suggesting malignancy over nevus include thickness over 2 mm, subretinal fluid, orange pigment, acoustic hollowness and symptoms. Diagnosis is clinical with ultrasound and photography; biopsy is reserved for uncertain cases because of seeding risk. Treatment options include plaque brachytherapy, proton beam and enucleation, with surveillance for liver metastasis. Choroidal hemangioma is orange and treated with photodynamic therapy. Metastasis is the commonest intraocular malignancy overall.
Surface disease
Conjunctival melanoma, ocular surface squamous neoplasia and lymphoma (often MALT type) require biopsy. Basal cell carcinoma of the eyelid is commonest, with pearly margins and ulceration; squamous cell carcinoma and sebaceous carcinoma (pagetoid spread, high mortality) also occur.
Traps
Do not confuse retinoblastoma with persistent fetal vasculature or Coats disease. Trilateral retinoblastoma involves midline intracranial tumor. Iris melanoma versus naevus hinges on seeding, vascularity and growth.
Rule of thumb
Any suspected intraocular tumor should be referred without fine-needle biopsy, and any child with leukocoria needs urgent fundoscopy under anesthesia.
Pathology
Concept anchors
Correlate histology with clinical appearance. Corneal specimens show epithelium, Bowman layer, stroma, Descemet membrane and endothelium; Fuchs dystrophy shows thickened Descemet with guttae, and keratoconus shows stromal thinning and breaks in Bowman layer. Lens pathology shows cortical clefts, Morgagnian change and capsule thickening. Retinal histology includes photoreceptor loss in dystrophies and neovascular fronds in proliferative disease.
Inflammation and tumors
Granulomas with epithelioid histiocytes and giant cells suggest sarcoidosis, tuberculosis or fungal infection. Amyloid stains with Congo red and shows apple-green birefringence under polarized light; periodic acid-Schiff highlights basement membrane and fungi; Ziehl-Neelsen for acid-fast bacilli; Giemsa for chlamydia inclusions and cytology. Uveal melanoma is classified as spindle, epithelioid or mixed, with epithelioid cells and high mitotic activity carrying a worse prognosis. Retinoblastoma shows Flexner-Wintersteiner rosettes and necrosis with calcification.
Specimens and technique
Aqueous tap, vitreous biopsy and fine-needle aspiration have low cellular yield; cytology and flow cytometry help diagnose lymphoma. Frozen sections guide margins in eyelid tumor excision, particularly for basal cell carcinoma.
Traps
Distinguish inflammatory pseudotumor from lymphoma, and reactive lymphoid hyperplasia from MALT lymphoma. Do not interpret crush artefact as malignancy. Phthisis bulbi shows disorganised intraocular structure with ossification.
Worked rule of thumb
In orbital disease, a specimen that is heavily fibrous and paucicellular often indicates sclerosing pseudotumor; a monomorphic lymphoid infiltrate suggests lymphoma and needs immunophenotyping.
General/Community Ophthalmology
Concept anchors
Population health questions test screening, epidemiology and study design. Know the commonest causes of blindness globally (cataract, glaucoma, macular degeneration, diabetic retinopathy, trachoma) and the WHO versus legal definitions of blindness, which differ in acuity and field thresholds. Screening programmes must satisfy Wilson criteria: important disease, accepted test, adequate sensitivity and specificity, effective treatment and acceptable cost. Diabetic retinopathy screening, retinopathy of prematurity screening and amblyopia screening are the standard examples.
Prevention
Trachoma control uses the SAFE strategy (surgery for trichiasis, antibiotics, facial cleanliness, environmental improvement). Vitamin A supplementation reduces childhood mortality and xerophthalmia; measles vaccination prevents keratopathy; ivermectin controls onchocerciasis. Glaucoma screening is not cost-effective at population level because of low prevalence and test limitations.
Statistics and governance
Understand sensitivity, specificity, positive predictive value (which depends on prevalence), likelihood ratios, number needed to treat and confidence intervals. Recognise study designs - randomised controlled trial, cohort, case-control, cross-sectional - and sources of bias. Clinical governance covers audit versus research, consent, confidentiality and duty of candour. Telemedicine and artificial intelligence grading are expanding access but require validation in local populations.
Traps
Questions often test that a highly sensitive test is best for ruling out disease, and that a common disease yields a higher positive predictive value than a rare one at the same test accuracy.
Rule of thumb
Screening is only justified when early detection changes outcome - this is why diabetic retinopathy screening is endorsed and general population glaucoma screening is not.