Kuwait Board Ophthalmology cheat sheet

Corneal layers (anterior to posterior): epithelium, Bowman layer, stroma, Descemet membrane, endothelium; corneal transparency depends on stromal collagen lattice spacing (~30 nm) and relative deturgescence.

Aqueous production ~2.5 µL/min, mostly by ciliary epithelium via carbonic anhydrase and Na+/K+-ATPase; outflow splits ~80-90% trabecular (pressure-dependent) and ~10-20% uveoscleral (pressure-independent).

Tear film: lipid (meibomian), aqueous (lacrimal and accessory glands), mucin (goblet cells, MUC5AC); precorneal film thickness ~3-7 µm; normal tear breakup time >10 s.

Retinal layers from inner to outer: nerve fiber, ganglion cell, inner plexiform, inner nuclear, outer plexiform, outer nuclear, external limiting membrane, photoreceptor inner/outer segments, RPE.

Rod phototransduction: rhodopsin absorbs photon, activates transducin, activates phosphodiesterase, lowers cGMP, closes cGMP-gated Na+ channels, hyperpolarizes the cell.

Optic nerve has ~1.0-1.2 million axons; fovea lies ~3.5 mm temporal to disc; optic disc ~1.5 mm diameter; foveola is ~0.35 mm and has no rods.

Pupillary light reflex: afferent via optic nerve and pretectal nucleus, efferent via Edinger-Westphal nucleus and ciliary ganglion; near response adds convergence and accommodation.

Extraocular muscles: four recti and two obliques; superior oblique is intorter, depressor, and abductor; inferior oblique is extorter, elevator, and abductor; superior rectus and inferior rectus are adductors.

Snell law: n1 sin θ1 = n2 sin θ2; critical angle θc = arcsin(n2/n1) when n1 > n2; total internal reflection occurs beyond θc.

Thin lens equation: 1/f = 1/u + 1/v; lens power in diopters D = 1/f (meters); two thin lenses in contact add powers; separated lenses use D = D1 + D2 − d·D1·D2.

Gullstrand reduced eye: power ~60 D, axial length ~22.2 mm; total refractive power cornea ~43 D, crystalline lens ~19-20 D.

Prism: 1 prism diopter deviates a ray 1 cm at 1 m; total deviation of stacked prisms adds approximately; Prentice rule P = c × D for decentration in cm.

Aberrations: spherical aberration, coma, astigmatism, distortion, field curvature (Seidel); chromatic aberration follows Abbe number; higher-order aberrations described by Zernike polynomials.

Diffraction limit: Rayleigh criterion θ = 1.22 λ/d; smaller pupil improves blur from defocus but worsens diffraction below ~2 mm.

Laser safety: Nd:YAG 1064 nm, argon 488/514 nm, frequency-doubled YAG 532 nm; protective eyewear must match wavelength and optical density.

Myopia: concave (minus) lenses; hyperopia: convex (plus) lenses; astigmatism corrected by cylindrical lens with axis 90° from the meridian of greatest power.

Spherical equivalent = sphere + ½ cylinder; vertex distance conversion matters above ~±4 D: Fnew = F / (1 − d·F).

Retinoscopy: neutralization with plus lenses in hyperopia; with-minus technique; working distance 50 cm adds +2.00 D, 67 cm adds +1.50 D.

Keratometry measures anterior corneal curvature; contact lens base curve is typically fitted 0.6-1.0 mm flatter than K; steeper than K gives apical bearing.

Rigid gas-permeable lens fit: central alignment, 0.5-1.0 mm edge clearance, 1-2 mm movement; orthokeratology flattens central cornea and steepens mid-periphery.

Soft lens complications: giant papillary conjunctivitis, microbial keratitis, hypoxia-induced neovascularization, superior epithelial arcuate lesions; extended wear increases risk.

Amblyopia treatment uses refractive correction first, then patching or atropine penalization; compliance drives outcome and occlusion amblyopia must be monitored.

Bacterial keratitis: risk factors include contact lens wear and trauma; hypopyon, stromal infiltrate, and overlying epithelial defect; corneal scrape for culture before treatment.

Fungal keratitis: feathery margins, satellite lesions, endothelial plaque; common after vegetative trauma; treated with topical natamycin or voriconazole; confocal microscopy aids diagnosis.

Acanthamoeba keratitis: severe pain out of proportion, radial keratoneuritis, ring infiltrate; associated with contact lens and tap water; treated with biguanides (PHMB, chlorhexidine).

Herpes simplex keratitis: dendritic ulcer with terminal bulbs, rose bengal or fluorescein staining; topical steroid alone is contraindicated; stromal disease may need steroid with antiviral cover.

Dry eye: Schirmer test I <5 mm/5 min suggests aqueous deficiency; TBUT <10 s suggests evaporative; meibomian gland dysfunction is the leading cause of evaporative dry eye.

Pterygium: fibrovascular growth onto cornea, usually nasal; excision with conjunctival autograft lowers recurrence; topical mitomycin C is an adjunct.

Keratoconus: inferior steepening, Vogt striae, Fleischer ring, Munson sign; management includes rigid lenses, corneal cross-linking, and keratoplasty.

Phacoemulsification: divide-and-conquer or chop techniques; maintain anterior chamber stability; capsulorhexis diameter ~5-5.5 mm for adequate overlap of intraocular lens optic.

Intraocular lens power calculation: SRK/T or Barrett for standard eyes; Hoffer Q or Holladay for short eyes; Haigis or Barrett for long eyes; measure axial length and keratometry.

Posterior capsule opacification: most common late complication; treated with Nd:YAG laser posterior capsulotomy; risk of retinal detachment and intraocular lens pitting.

Endophthalmitis after cataract surgery: presents within days with pain, hypopyon, and decreased vision; intravitreal antibiotics (vancomycin plus ceftazidime) are the standard treatment.

LASIK: flap creation, excimer laser ablation; contraindications include thin cornea, keratoconus, severe dry eye; PRK avoids flap and is preferred for thin corneas or trauma risk.

Refractive surgery complications: dry eye, flap striae, diffuse lamellar keratitis, ectasia, undercorrection or overcorrection; enhancement may be needed.

Open-angle glaucoma: optic disc cupping, retinal nerve fiber layer thinning, visual field defects; elevated intraocular pressure is a major risk factor but not required for diagnosis.

Acute angle-closure glaucoma: severe eye pain, headache, nausea, mid-dilated fixed pupil, corneal edema, shallow anterior chamber; treat with topical and systemic pressure-lowering agents, then laser peripheral iridotomy.

Primary open-angle glaucoma treatment: prostaglandin analogs first-line, then beta-blockers, alpha-2 agonists, carbonic anhydrase inhibitors; laser trabeculoplasty and surgery for uncontrolled cases.

Normal-tension glaucoma: glaucomatous optic neuropathy with intraocular pressure within normal range; consider vascular, systemic, and sleep apnea associations.

Visual field defects in glaucoma: nasal step, arcuate scotoma, paracentral scotoma, altitudinal defect; pattern deviation plot helps identify localized loss.

Optic disc assessment: cup-to-disc ratio, neuroretinal rim thinning, disc hemorrhage, bayoneting; asymmetry between eyes is significant.

Diabetic retinopathy: nonproliferative with microaneurysms, dot-blot hemorrhages, hard exudates, cotton wool spots; proliferative with neovascularization; treat with panretinal photocoagulation or anti-VEGF.

Diabetic macular edema: leading cause of vision loss in diabetes; treat with anti-VEGF injections or focal/grid laser; assess with optical coherence tomography.

Retinal detachment: rhegmatogenous with a tear and subretinal fluid; symptoms include flashes, floaters, and a curtain; treat with scleral buckle, vitrectomy, or pneumatic retinopexy.

Central retinal artery occlusion: sudden painless vision loss, cherry-red spot, pale retina; associated with carotid disease, atrial fibrillation, and giant cell arteritis in older patients.

Central retinal vein occlusion: blood and thunder fundus, flame hemorrhages, cotton wool spots, macular edema; risk factors include hypertension, diabetes, and glaucoma.

Age-related macular degeneration: dry type with drusen and geographic atrophy; wet type with choroidal neovascularization; anti-VEGF is the main treatment for wet AMD.

Retinopathy of prematurity: occurs in premature infants; staging by zone, stage, and plus disease; treatment with laser or anti-VEGF for type 1 disease.

Anterior uveitis: cells and flare in the anterior chamber, ciliary flush, photophobia; common causes include HLA-B27 spondyloarthropathy, sarcoidosis, herpes, and trauma.

Posterior uveitis: vitritis, retinitis, choroiditis; consider toxoplasmosis, tuberculosis, syphilis, sarcoidosis, and Behçet disease.

Behçet disease: recurrent oral and genital ulcers, hypopyon uveitis, retinal vasculitis; treated with systemic immunosuppression.

Sympathetic ophthalmia: bilateral granulomatous uveitis after penetrating trauma or surgery in one eye; treated with systemic steroids and immunosuppression.

Herpes zoster ophthalmicus: vesicles in V1 distribution, Hutchinson sign, keratitis, uveitis; treat with systemic antivirals and monitor for neurotrophic keratopathy.

Uveitis workup: targeted by history and examination; consider HLA-B27, chest imaging, syphilis serology, tuberculosis testing, and ACE level.

Optic neuritis: painful vision loss, afferent pupillary defect, dyschromatopsia, swollen disc; associated with multiple sclerosis; treat with intravenous steroids for recovery.

Papilledema: bilateral optic disc swelling from raised intracranial pressure; preserve visual acuity until late; evaluate with neuroimaging and lumbar puncture.

Third nerve palsy: ptosis, down-and-out eye, dilated pupil if compressive; pupil-sparing suggests microvascular ischemia; urgent imaging for pupil-involving cases.

Fourth nerve palsy: vertical diplopia, head tilt, hypertropia; congenital or traumatic; Parks-Bielschowsky three-step test localizes the lesion.

Sixth nerve palsy: esotropia, limited abduction; consider raised intracranial pressure, diabetes, and microvascular disease.

Horner syndrome: ptosis, miosis, anhidrosis; localize with cocaine or apraclonidine testing and hydroxyamphetamine; postganglionic lesions do not cause anhidrosis.

Visual field defects: bitemporal hemianopia from chiasmal lesion, homonymous hemianopia from retrochiasmal lesion, quadrantanopia from temporal or parietal lobe lesion.

Eyelid anatomy: skin, orbicularis oculi, orbital septum, levator aponeurosis, Müller muscle, tarsus, conjunctiva; ptosis surgery depends on levator function.

Chalazion: chronic lipogranuloma of meibomian gland; treated with warm compresses, incision and curettage, or intralesional steroid; hordeolum is acute infection.

Orbital cellulitis: fever, proptosis, pain, restricted motility; urgent imaging and intravenous antibiotics; distinguish from preseptal cellulitis.

Thyroid eye disease: proptosis, lid retraction, diplopia, optic neuropathy; manage with lubricants, steroids, orbital decompression, or radiation.

Orbital fracture: blowout fracture with restricted upward gaze and enophthalmos; assess with computed tomography; repair for entrapment or significant defect.

Dacryocystorhinostomy: treatment for nasolacrimal duct obstruction; creates a fistula between lacrimal sac and nasal cavity.

Amblyopia: reduced vision from abnormal visual experience; types include strabismic, refractive, anisometropic, and deprivation; treat with correction, patching, or atropine.

Esotropia: inward deviation; infantile esotropia presents before 6 months; accommodative esotropia associated with hyperopia; treat with glasses, patching, or surgery.

Exotropia: outward deviation; intermittent exotropia common; surgery for poorly controlled cases.

Leukocoria: white pupillary reflex; differential includes retinoblastoma, congenital cataract, retinopathy of prematurity, and persistent fetal vasculature; urgent evaluation.

Congenital nasolacrimal duct obstruction: tearing and discharge in infants; usually resolves by 12 months; massage and probing if persistent.

Strabismus examination: cover test, alternate cover test, Hirschberg, Krimsky, and prism bar; assess binocular vision and stereopsis.

Retinoblastoma: most common intraocular malignancy in children; leukocoria and strabismus; treat with chemotherapy, laser, cryotherapy, or enucleation depending on stage.

Uveal melanoma: most common primary intraocular malignancy in adults; pigmented choroidal mass; treat with plaque brachytherapy, proton beam, or enucleation.

Squamous cell carcinoma of conjunctiva: associated with ultraviolet exposure and human papillomavirus; treat with excision, cryotherapy, or topical chemotherapy.

Basal cell carcinoma: most common eyelid malignancy; pearly nodule with telangiectasia; treated with excision with margin control.

Sebaceous carcinoma: aggressive eyelid tumor; may mimic chalazion; treat with wide excision and frozen section control.

Ocular pathology: melanoma shows spindle or epithelioid cells; retinoblastoma shows Flexner-Wintersteiner rosettes; lymphoma shows monoclonal lymphoid infiltrate.

Chemical burn: immediate copious irrigation with saline or water for at least 30 minutes; check pH; assess for limbal ischemia and treat with topical steroids and antibiotics.

Central retinal artery occlusion: sudden painless vision loss; treat with ocular massage, anterior chamber paracentesis, and systemic evaluation; time-critical.

Acute angle-closure glaucoma: severe pain, nausea, mid-dilated pupil, corneal edema; treat with topical and systemic agents, then laser iridotomy.

Open globe injury: do not manipulate the eye; shield, avoid pressure, give antibiotics and tetanus prophylaxis; urgent surgical repair.

Orbital compartment syndrome: proptosis, pain, decreased vision, afferent pupillary defect; emergency lateral canthotomy and cantholysis.

Endophthalmitis: post-surgical or post-traumatic; presents with pain, hypopyon, and vision loss; treat with intravitreal antibiotics and vitrectomy if severe.

Trauma evaluation: assess visual acuity, pupillary response, extraocular movements, and globe integrity; avoid pressure on suspected open globe.

Traumatic hyphema: blood in anterior chamber; treat with rest, topical steroids, cycloplegics, and intraocular pressure monitoring; avoid aspirin and nonsteroidal anti-inflammatory drugs.

Corneal foreign body: remove with slit-lamp guidance; treat with topical antibiotics; monitor for infection and rust ring.

Community eye health: vision screening, diabetic retinopathy screening, glaucoma awareness, and cataract surgery programs reduce avoidable blindness.

Trachoma: caused by Chlamydia trachomatis; follicular conjunctivitis, trichiasis, corneal opacity; SAFE strategy (surgery, antibiotics, facial cleanliness, environmental improvement).

Vitamin A deficiency: causes night blindness, xerophthalmia, Bitot spots, and keratomalacia; supplementation prevents blindness in children.

Retinoblastoma: most common intraocular malignancy in children; leukocoria and strabismus; treat with chemotherapy, laser, cryotherapy, or enucleation depending on stage.

Uveal melanoma: most common primary intraocular malignancy in adults; pigmented choroidal mass; treat with plaque brachytherapy, proton beam, or enucleation.

Squamous cell carcinoma of conjunctiva: associated with ultraviolet exposure and human papillomavirus; treat with excision, cryotherapy, or topical chemotherapy.

Basal cell carcinoma: most common eyelid malignancy; pearly nodule with telangiectasia; treated with excision with margin control.

Sebaceous carcinoma: aggressive eyelid tumor; may mimic chalazion; treat with wide excision and frozen section control.

Ocular pathology: melanoma shows spindle or epithelioid cells; retinoblastoma shows Flexner-Wintersteiner rosettes; lymphoma shows monoclonal lymphoid infiltrate.

Chemical burn: immediate copious irrigation with saline or water for at least 30 minutes; check pH; assess for limbal ischemia and treat with topical steroids and antibiotics.

Central retinal artery occlusion: sudden painless vision loss; treat with ocular massage, anterior chamber paracentesis, and systemic evaluation; time-critical.

Acute angle-closure glaucoma: severe pain, nausea, mid-dilated pupil, corneal edema; treat with topical and systemic agents, then laser iridotomy.

Open globe injury: do not manipulate the eye; shield, avoid pressure, give antibiotics and tetanus prophylaxis; urgent surgical repair.

Orbital compartment syndrome: proptosis, pain, decreased vision, afferent pupillary defect; emergency lateral canthotomy and cantholysis.

Endophthalmitis: post-surgical or post-traumatic; presents with pain, hypopyon, and vision loss; treat with intravitreal antibiotics and vitrectomy if severe.

Trauma evaluation: assess visual acuity, pupillary response, extraocular movements, and globe integrity; avoid pressure on suspected open globe.

Traumatic hyphema: blood in anterior chamber; treat with rest, topical steroids, cycloplegics, and intraocular pressure monitoring; avoid aspirin and nonsteroidal anti-inflammatory drugs.

Corneal foreign body: remove with slit-lamp guidance; treat with topical antibiotics; monitor for infection and rust ring.

Community eye health: vision screening, diabetic retinopathy screening, glaucoma awareness, and cataract surgery programs reduce avoidable blindness.

Trachoma: caused by Chlamydia trachomatis; follicular conjunctivitis, trichiasis, corneal opacity; SAFE strategy (surgery, antibiotics, facial cleanliness, environmental improvement).

Vitamin A deficiency: causes night blindness, xerophthalmia, Bitot spots, and keratomalacia; supplementation prevents blindness in children.