Arab Board Ophthalmology Part 1 cheat sheet

Corneal epithelium derives from surface ectoderm; corneal stroma and endothelium derive from neural crest.

Lens develops from surface ectoderm; the lens vesicle forms after invagination of the lens placode.

Aqueous humor is produced by the ciliary epithelium (active secretion) at ~2.5 µL/min; flows through trabecular meshwork and Schlemm's canal.

Optic nerve fibers are myelinated by oligodendrocytes; retinal nerve fiber layer is unmyelinated.

The fovea has the highest concentration of cones and no rods; the optic disc has no photoreceptors (blind spot).

Tear film has three layers: lipid (meibomian glands), aqueous (lacrimal and accessory glands), and mucin (goblet cells).

The extraocular muscles are supplied by CN III (superior, inferior, medial recti and inferior oblique), CN IV (superior oblique), and CN VI (lateral rectus).

Corneal transparency depends on uniform collagen fibril spacing and relative dehydration maintained by the endothelium.

Pilocarpine is a direct muscarinic agonist that causes miosis and ciliary muscle contraction, increasing trabecular outflow.

Timolol is a nonselective beta-blocker that reduces aqueous production; contraindicated in asthma and heart block.

Latanoprost is a prostaglandin F2α analog that increases uveoscleral outflow; adverse effects include iris darkening and eyelash lengthening.

Atropine is a nonselective muscarinic antagonist causing cycloplegia and mydriasis; duration of action is up to 2 weeks.

Phenylephrine is an alpha-1 agonist used for mydriasis without cycloplegia; it can cause systemic hypertension.

Acetazolamide is a carbonic anhydrase inhibitor that reduces aqueous production; can cause paresthesias and metabolic acidosis.

Corticosteroids reduce inflammation by inhibiting phospholipase A2 and decreasing prostaglandin synthesis.

Fluoroquinolones inhibit bacterial DNA gyrase (topoisomerase II) and are used for corneal ulcers.

Snell's law: n1 sin θ1 = n2 sin θ2; total internal reflection occurs when light travels from a denser to a less dense medium at an angle greater than the critical angle.

Thin lens formula: 1/f = 1/v - 1/u (with sign convention); power in diopters = 1/f in meters.

Myopia is corrected with a concave (minus) lens; hyperopia with a convex (plus) lens.

Astigmatism is corrected with a cylindrical lens; the axis indicates the meridian of no power.

The far point of a myopic eye is the farthest point that can be seen clearly without accommodation.

Prism diopter (Δ) = 100 × tan(deviation angle); used to measure strabismus.

Keratometry measures corneal curvature; average corneal power is about 43 diopters.

The reduced eye has a single refractive surface with a power of about 60 diopters and an axial length of 22.22 mm.

Gram-positive bacteria (Staphylococcus aureus, Streptococcus pneumoniae) are common causes of corneal ulcers; Gram-negative (Pseudomonas) are associated with contact lens use.

Fungal keratitis (Fusarium, Aspergillus) shows feathery borders and satellite lesions; treated with natamycin or amphotericin B.

Acanthamoeba keratitis is associated with contact lens use and presents with severe pain and ring infiltrate.

Retinoblastoma is caused by a mutation in the RB1 tumor suppressor gene on chromosome 13q14.

Uveal melanoma is the most common primary intraocular malignancy in adults; arises from melanocytes.

Apoptosis is programmed cell death; necrosis is characterized by cell swelling and inflammation.

Herpes simplex virus keratitis presents with dendritic ulcers; herpes zoster ophthalmicus follows the V1 dermatome.

Cataract is characterized by accumulation of aggregated proteins and loss of lens transparency.

The eye is an immune-privileged site due to blood-ocular barrier, absence of lymphatic drainage, and immunosuppressive factors (TGF-β, Fas ligand).

HLA-B27 is associated with anterior uveitis, ankylosing spondylitis, and reactive arthritis.

HLA-DR4 is associated with Vogt-Koyanagi-Harada disease and birdshot chorioretinopathy (HLA-A29).

Type I hypersensitivity is IgE-mediated (allergic conjunctivitis); Type IV is T-cell mediated (contact dermatitis).

Sympathetic ophthalmia is a bilateral granulomatous uveitis following penetrating trauma to one eye.

Phacoanaphylactic uveitis is a granulomatous inflammation against lens proteins after lens capsule rupture.

Cicatricial pemphigoid and Stevens-Johnson syndrome are causes of conjunctival cicatrization.

Tumor necrosis factor inhibitors (infliximab, adalimumab) are used for refractory uveitis.

Keratoconus is characterized by corneal thinning and ectasia, often inferior steepening on topography.

Fuchs' endothelial dystrophy shows guttae (excrescences of Descemet's membrane) and corneal edema.

Bacterial keratitis is treated with fortified topical antibiotics (e.g., cefazolin and tobramycin).

Dry eye disease is diagnosed with Schirmer test, tear break-up time, and ocular surface staining.

Herpes simplex keratitis is treated with topical antivirals (e.g., ganciclovir gel) or oral acyclovir.

Corneal abrasion is managed with topical antibiotics and sometimes a bandage contact lens.

Pterygium is a fibrovascular growth from conjunctiva onto cornea; risk factors include UV exposure.

Corneal transplant rejection is mediated by T cells; signs include graft edema and keratic precipitates.

Age-related cataract is the most common cause of reversible blindness worldwide.

Nuclear sclerotic cataract causes index myopia (second sight).

Phacoemulsification uses ultrasound to emulsify the lens; complications include posterior capsule rupture and endophthalmitis.

Posterior capsule opacification is treated with Nd:YAG laser capsulotomy.

Congenital cataract may be associated with rubella, galactosemia, and trisomy 21.

Intraocular lens power calculation uses keratometry, axial length, and A-constant.

Pseudoexfoliation syndrome increases risk of zonular weakness and capsular rupture during surgery.

Traumatic cataract may result from blunt or penetrating injury; a rosette-shaped opacity is typical.

Primary open-angle glaucoma is characterized by optic disc cupping and visual field loss; IOP may be normal.

Acute angle-closure glaucoma presents with severe pain, halos, mid-dilated pupil, and corneal edema.

Trabeculectomy is a filtering surgery that creates a fistula for aqueous drainage.

Normal-tension glaucoma may be associated with nocturnal hypotension or vasospasm.

Gonioscopy is essential to differentiate open-angle from angle-closure glaucoma.

Beta-blockers reduce aqueous production; prostaglandins increase uveoscleral outflow.

Optic disc hemorrhages (Drance hemorrhages) are a sign of glaucoma progression.

Neovascular glaucoma is associated with VEGF-driven angle neovascularization; treat with anti-VEGF and panretinal photocoagulation.

Diabetic retinopathy is classified as non-proliferative (microaneurysms, hemorrhages, hard exudates) and proliferative (neovascularization).

Panretinal photocoagulation is used for proliferative diabetic retinopathy to reduce VEGF drive.

Central retinal artery occlusion presents with sudden painless vision loss and a cherry-red spot.

Central retinal vein occlusion shows blood-and-thunder fundus with diffuse hemorrhages.

Rhegmatogenous retinal detachment is caused by a retinal tear; treated with scleral buckle or vitrectomy.

Age-related macular degeneration: dry type shows drusen; wet type shows choroidal neovascularization treated with anti-VEGF.

Retinitis pigmentosa presents with night blindness, bone-spicule pigmentation, and ring scotoma.

Vitreous hemorrhage may result from diabetic retinopathy, trauma, or retinal tear.

Anterior uveitis presents with cells and flare in the anterior chamber; treated with topical steroids and cycloplegics.

Intermediate uveitis involves the vitreous and pars plana; often idiopathic or associated with sarcoidosis.

Posterior uveitis includes retinitis and choroiditis; infectious causes include toxoplasmosis and CMV.

Retinoblastoma presents with leukocoria and strabismus; calcification on imaging is typical.

Uveal melanoma is the most common primary intraocular tumor in adults; treated with plaque brachytherapy or enucleation.

Choroidal hemangioma is a benign vascular tumor associated with Sturge-Weber syndrome.

Toxoplasmosis retinochoroiditis shows a focal necrotizing lesion adjacent to a scar.

Intraocular lymphoma often masquerades as chronic uveitis and is a diffuse large B-cell lymphoma.

Optic neuritis presents with painful vision loss, afferent pupillary defect, and dyschromatopsia; associated with multiple sclerosis.

Papilledema is bilateral optic disc swelling due to raised intracranial pressure.

Third nerve palsy causes ptosis, mydriasis, and eye down and out; pupil involvement suggests compression.

Internuclear ophthalmoplegia is caused by a lesion in the medial longitudinal fasciculus; shows impaired adduction and nystagmus.

Horner's syndrome presents with ptosis, miosis, and anhidrosis due to sympathetic pathway lesion.

Strabismus is misalignment of the eyes; esotropia is inward deviation, exotropia is outward.

Amblyopia is reduced vision due to abnormal visual development; treated with occlusion therapy.

Argyll Robertson pupil is small, irregular, and reacts to accommodation but not light; associated with neurosyphilis.

Thyroid eye disease presents with exophthalmos, lid retraction, and restrictive myopathy; associated with Graves' disease.

Orbital cellulitis is an infection of orbital tissues; signs include proptosis, pain, and fever; treated with IV antibiotics.

Basal cell carcinoma is the most common eyelid malignancy; presents as a pearly nodule with telangiectasia.

Dacryocystitis is inflammation of the lacrimal sac; treated with antibiotics and dacryocystorhinostomy (DCR).

Ptosis can be congenital (levator dysgenesis) or acquired (aponeurotic, neurogenic, myogenic).

Orbital floor fracture may cause diplopia and enophthalmos; inferior rectus entrapment is common.

Chalazion is a lipogranuloma of the meibomian gland; treated with warm compresses or incision and curettage.

Orbital lymphoma often presents as a painless, progressive mass; biopsy is required for diagnosis.