RANZCO Ophthalmic Sciences cheat sheet

Corneal layers (anterior to posterior): epithelium, Bowman layer, stroma, Descemet membrane, endothelium; endothelium is non-regenerating and its pump maintains stromal deturgescence.

Aqueous humour is secreted by the ciliary epithelium via active Na+/K+-ATPase and carbonic anhydrase; flow passes trabecular meshwork, Schlemm canal, collector channels, episcleral veins.

Lens protein transparency depends on crystallin order; oxidative damage and calcium-activated proteases (calpains) drive cataractogenesis.

Phototransduction: light isomerises 11-cis-retinal to all-trans-retinal, activating rhodopsin and transducin, lowering cGMP and closing cGMP-gated cation channels, hyperpolarising the photoreceptor.

Snell's law n1 sin i = n2 sin r; refractive power of a spherical surface F = (n2 - n1)/r, and thin lens power in dioptres F = 1/f (metres).

Apoptosis is ATP-dependent, caspase-mediated, and non-inflammatory; necrosis is characterised by membrane rupture and inflammation.

Pharmacokinetics: topical drop bioavailability is roughly 1-5%; punctal occlusion and nasolacrimal occlusion reduce systemic absorption.

Genetics: autosomal dominant disease often shows vertical transmission and variable expressivity; X-linked recessive disorders affect males and are transmitted by carrier females.

Sudden painless monocular visual loss with a swollen pale optic disc suggests anterior ischaemic optic neuropathy; sudden loss with a normal disc suggests retrobulbar optic neuritis or central retinal artery occlusion.

Central retinal artery occlusion produces a cherry-red spot, retinal pallor, boxcarring, and a relative afferent pupillary defect; it is an ocular emergency.

Acute angle-closure glaucoma: mid-dilated fixed pupil, corneal oedema, hazy view, raised intraocular pressure; treat with pressure-lowering agents and definitive laser peripheral iridotomy.

Endophthalmitis after intraocular surgery presents with pain, hypopyon, and vitritis; vitreous tap with intravitreal antibiotics is the mainstay.

Giant cell arteritis should be suspected in patients over 50 with headache, jaw claudication, scalp tenderness, or visual loss; urgent high-dose corticosteroids and temporal artery biopsy are indicated.

Diabetic retinopathy screening: annual dilated fundoscopy; refer for proliferative changes or clinically significant macular oedema.

Retinal detachment: flashes, floaters, and a curtain-like field defect; a relative afferent pupillary defect and macular involvement alter urgency.

Relative afferent pupillary defect indicates asymmetric optic nerve or severe retinal disease; it is detected with the swinging flashlight test.

Optic neuritis: painful subacute monocular visual loss, reduced colour vision, relative afferent pupillary defect, and often a swollen disc; multiple sclerosis association is common.

Third nerve palsy with a dilated pupil suggests a compressive lesion such as posterior communicating artery aneurysm; pupil-sparing palsy is more often microvascular.

Horner syndrome: ptosis, miosis, and anhidrosis; a postganglionic lesion may show ipsilateral facial flushing and is associated with carotid dissection.

Bitemporal hemianopia localises to the optic chiasm; homonymous hemianopia localises retrochiasmally, often to the occipital lobe.

Papilloedema is bilateral optic disc swelling from raised intracranial pressure; it is usually painless and may be accompanied by transient visual obscurations.

Leber hereditary optic neuropathy: painless sequential central visual loss in young males, maternally inherited mitochondrial DNA mutations, and a relative afferent pupillary defect.

Extraocular muscles: medial rectus, inferior rectus, superior rectus, inferior oblique are supplied by the oculomotor nerve; superior oblique by the trochlear nerve; lateral rectus by the abducens nerve.

Ductions are monocular movements; versions are binocular conjugate movements; vergences are disjunctive movements.

Esotropia is inward deviation; exotropia is outward deviation; hypertropia is upward deviation of one eye.

The cover-uncover test detects heterotropia; the alternate cover test detects heterophoria and total deviation.

Amblyopia results from visual deprivation, strabismus, or anisometropia during the critical period; treatment includes refractive correction, occlusion, and atropine penalisation.

Congenital esotropia presents before 6 months with a large-angle constant deviation and requires early surgery to preserve binocular potential.

Paralytic strabismus produces incomitance: the deviation varies with direction of gaze and is greatest in the field of the paretic muscle.

Bacterial keratitis: risk factors include contact lens wear and trauma; hypopyon and stromal infiltrate warrant urgent corneal scrapings and fortified topical antibiotics.

Fungal keratitis is suggested by feathery infiltrates, satellite lesions, and a history of vegetative trauma; diagnosis requires corneal scraping with stains and culture.

Acanthamoeba keratitis: contact lens wear with water exposure, severe pain out of proportion to signs, and ring infiltrate; culture on non-nutrient agar with Escherichia coli.

Herpes simplex keratitis: dendritic ulcer with terminal bulbs; topical corticosteroids are contraindicated in epithelial disease.

Dry eye disease: tear film instability and hyperosmolarity; treatment includes artificial tears, punctal plugs, and lid hygiene.

Keratoconus: progressive corneal thinning and ectasia with irregular astigmatism; management includes rigid gas-permeable lenses and corneal collagen cross-linking.

Corneal ulceration with hypopyon requires urgent ophthalmology review; do not patch a suspected microbial keratitis.

Open-angle glaucoma is a chronic optic neuropathy with characteristic disc cupping and field loss; intraocular pressure is the major modifiable risk factor.

Acute angle-closure glaucoma presents with severe pain, halos, nausea, and a mid-dilated fixed pupil; treat with topical and systemic pressure-lowering agents, then laser peripheral iridotomy.

Target intraocular pressure should be individualised, often 20-30% below baseline in moderate disease.

Trabeculectomy creates a guarded fistula; complications include hypotony, bleb leak, and endophthalmitis.

Primary open-angle glaucoma risk factors: age, African ancestry, family history, elevated intraocular pressure, myopia, and thin central corneal thickness.

Optic disc cupping: increased cup-to-disc ratio, neuroretinal rim thinning, and disc haemorrhage are suggestive of glaucomatous damage.

Prostaglandin analogues increase uveoscleral outflow and are first-line for open-angle glaucoma; side effects include iris darkening and eyelash lengthening.

Retinal layers (inner to outer): nerve fibre, ganglion cell, inner plexiform, inner nuclear, outer plexiform, outer nuclear, photoreceptor, retinal pigment epithelium.

Central retinal artery occlusion causes sudden painless visual loss with a cherry-red spot and retinal pallor; it is an emergency.

Central retinal vein occlusion presents with a blood-and-thunder fundus: scattered haemorrhages, venous engorgement, and disc oedema.

Diabetic retinopathy: non-proliferative changes include microaneurysms, dot-blot haemorrhages, hard exudates, and cotton-wool spots; proliferative disease shows neovascularisation.

Retinal detachment: rhegmatogenous detachment is caused by a retinal break with vitreous fluid; treat with laser, cryotherapy, or vitrectomy.

Age-related macular degeneration: dry type shows drusen and geographic atrophy; wet type shows choroidal neovascularisation and requires anti-VEGF therapy.

Vitreous haemorrhage: sudden floaters and visual loss; causes include proliferative diabetic retinopathy, retinal tear, and trauma.

Orbital cellulitis presents with proptosis, pain, restricted eye movement, and fever; it is an emergency requiring intravenous antibiotics and imaging.

Preseptal cellulitis is confined anterior to the orbital septum and does not cause proptosis or restricted motility.

Thyroid eye disease: lid retraction, proptosis, restrictive myopathy, and optic neuropathy; smoking worsens the disease.

Dacryocystorhinostomy relieves nasolacrimal duct obstruction by creating a fistula between the lacrimal sac and nasal cavity.

Basal cell carcinoma is the most common eyelid malignancy; it is locally invasive and rarely metastasises.

Orbital compartment syndrome: acute proptosis with raised orbital pressure threatens vision; urgent lateral canthotomy and cantholysis may be required.

Ptosis in the elderly is commonly aponeurotic; congenital ptosis may cause amblyopia and requires early assessment.

Leukocoria (white pupillary reflex) requires urgent evaluation for retinoblastoma, congenital cataract, and other causes.

Retinopathy of prematurity screening is indicated for premature infants with birth weight under 1500 g or gestational age under 32 weeks.

Congenital glaucoma presents with tearing, photophobia, corneal enlargement (buphthalmos), and elevated intraocular pressure.

Amblyopia treatment is most effective during the critical period, roughly the first 6-8 years of life.

Strabismus in children requires prompt assessment to prevent amblyopia and to detect underlying pathology.

Congenital cataract requires early surgery to prevent dense amblyopia; postoperative refractive correction and occlusion therapy are important.

Retinoblastoma: leukocoria and strabismus are common presentations; management depends on tumour size and laterality and may include chemotherapy, laser, or enucleation.