ABPS Ophthalmology cheat sheet

Corneal epithelium regenerates from limbal stem cells; total turnover is roughly 7-14 days.

Endothelial cells do not regenerate; normal density is about 2500 cells/mm2 and falls ~0.5%/year in adults.

Corneal transparency depends on uniform collagen spacing and relative deturgescence maintained by the endothelial pump.

Fluorescein staining is enhanced by cobalt blue light; rose bengal and lissamine green stain devitalized epithelium.

Keratoconus shows inferior steepening, against-the-rule astigmatism, and scissoring of the retinoscopic reflex.

Fleischer ring is iron deposition at the cone base; Vogt striae are deep stromal stress lines that disappear with pressure.

A positive Seidel test indicates full-thickness corneal or scleral wound leak with aqueous egress.

Anterior chamber depth assessment: shallow AC with iris bombé suggests pupillary block; focal synechiae suggest PAS.

Herpetic dendritic ulcer stains with fluorescein and has terminal bulbs; geographic ulcers occur with steroid use.

Nuclear sclerosis causes index myopia ("second sight"); posterior subcapsular opacity degrades near vision and glare most.

Phacoemulsification power rises with harder nuclei; effective phaco time correlates with endothelial cell loss.

Biometry: optical (IOLMaster) is preferred; immersion A-scan is acceptable when optical fails.

SRK/T and Holladay formulas are best for average eyes; Hoffer Q and Hill-RAR are preferred for short eyes (<22 mm).

Barrett Universal II uses anterior chamber depth and lens thickness and performs well across axial lengths.

Post-LASIK/PRK IOL power: use historical refraction, keratometric, and no-history methods; avoid standard K-based formulas.

Myopic LASIK flattens central cornea; hyperopic LASIK steepens it; both alter the effective keratometric power.

Refractive surgery candidates require stable refraction for at least 1 year and adequate corneal thickness (>450-500 microns residual bed).

Pseudophakic bullous keratopathy risk rises with low endothelial counts, hard nuclei, and prolonged phaco time.

Normal IOP is 10-21 mmHg; IOP is the only modifiable major risk factor for glaucoma progression.

Open-angle glaucoma shows optic disc cupping, RNFL thinning, and arcuate visual field defects respecting the horizontal midline.

Goldmann applanation tonometry is affected by central corneal thickness; thin corneas underestimate IOP.

Angle closure: gonioscopy is the gold standard; Van Herick grading estimates angle width at the slit lamp.

Laser peripheral iridotomy relieves pupillary block; it does not treat plateau iris or lens-induced mechanisms.

Prostaglandin analogs lower IOP most (25-33%) by increasing uveoscleral outflow; side effects include iris darkening and periorbital fat atrophy.

Beta-blockers are contraindicated in asthma and heart block; alpha-agonists can cause allergic conjunctivitis.

Acute angle-closure glaucoma presents with mid-dilated fixed pupil, corneal edema, and IOP often >40 mmHg.

Visual field progression: three consecutive points with p<5% on the same hemifield, or a cluster of points with p<1%.

Diabetic retinopathy: microaneurysms, dot-blot hemorrhages, hard exudates; proliferative disease shows neovascularization.

Diabetic macular edema is treated with anti-VEGF injections; focal laser is an alternative for non-center-involving edema.

CRVO shows diffuse retinal hemorrhages in all quadrants; BRVO shows hemorrhages in one quadrant respecting the horizontal raphe.

Central retinal artery occlusion shows a cherry-red spot, pale retina, and boxcarring; visual loss is sudden and painless.

Retinal detachment: posterior vitreous detachment causes flashes and floaters; a shadow or curtain indicates detachment.

Macular hole presents with central scotoma and metamorphopsia; OCT shows a full-thickness defect with cystic edges.

Wet AMD: choroidal neovascularization treated with anti-VEGF; dry AMD shows drusen and geographic atrophy.

Retinal tears with symptoms require urgent evaluation; laser retinopexy or cryotherapy reduces detachment risk.

Vitreous hemorrhage obscures fundus view; B-scan ultrasound is used to evaluate for retinal detachment.

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

Afferent pupillary defect (Marcus Gunn) indicates asymmetric optic nerve or severe retinal disease.

Papilledema is bilateral optic disc swelling from raised intracranial pressure; it spares visual acuity early.

Aneurysmal third nerve palsy: pupil-involving, painful, and requires urgent imaging.

Horner syndrome: ptosis, miosis, and anhidrosis; a painful Horner suggests carotid dissection.

Bitemporal hemianopia suggests chiasmal lesion (pituitary adenoma); homonymous hemianopia suggests retrochiasmal lesion.

Internuclear ophthalmoplegia: impaired adduction on the affected side with nystagmus of the abducting eye; suggests MLF lesion.

Cortical blindness may present with normal pupils and normal fundi; visual field defects respect the vertical meridian.

Giant cell arteritis: older patient with headache, jaw claudication, elevated ESR/CRP; risk of arteritic anterior ischemic optic neuropathy.

Orbital cellulitis: fever, proptosis, pain with eye movement, and restricted motility; requires urgent antibiotics and imaging.

Preseptal cellulitis spares eye movement and vision; it does not cause proptosis.

Dacryocystitis presents with medial canthal swelling and epiphora; treat with antibiotics and dacryocystorhinostomy if recurrent.

Chalazion is a lipogranuloma of the meibomian gland; hordeolum is an acute infectious eyelid gland inflammation.

Thyroid eye disease: lid retraction, proptosis, restrictive strabismus; orbital decompression for compressive optic neuropathy.

Basal cell carcinoma is the most common eyelid malignancy; it is locally invasive but rarely metastasizes.

Orbital blowout fracture: restricted upgaze, enophthalmos, and diplopia; CT shows floor fracture with herniation.

Ptosis with a normal pupil and no fatigability suggests aponeurotic dehiscence; fatigability suggests myasthenia gravis.

Amblyopia is reduced vision from abnormal visual experience; treatment is occlusion or penalization of the better eye.

Esotropia in a child: accommodative esotropia is corrected with hyperopic glasses; infantile esotropia presents before 6 months.

Strabismus surgery: recession weakens a muscle; resection strengthens it.

Leukocoria in a child requires urgent evaluation for retinoblastoma; red reflex screening is essential.

Congenital glaucoma: buphthalmos, corneal edema, photophobia, and tearing; treat surgically.

Nasolacrimal duct obstruction: epiphora and discharge in infants; resolves spontaneously in most within 12 months.

Strabismic amblyopia risk is highest with constant, unilateral deviation; alternate fixation suggests equal vision.

Retinopathy of prematurity screening begins at 4-6 weeks postnatal age or 31-32 weeks postmenstrual age.

Anterior uveitis presents with pain, photophobia, ciliary flush, and cells/flare in the anterior chamber.

HLA-B27-associated uveitis is typically acute, unilateral, and recurrent anterior uveitis.

Juvenile idiopathic arthritis uveitis is chronic, asymptomatic, and often bilateral; requires regular screening.

Posterior synechiae form between iris and lens; treat with cycloplegia and topical steroids.

Hypopyon indicates severe anterior chamber inflammation; consider infectious endophthalmitis or Behçet disease.

Toxoplasmosis retinochoroiditis: focal necrotizing lesion with adjacent scar; treat with pyrimethamine and sulfadiazine when vision-threatening.

Cytomegalovirus retinitis: hemorrhagic retinitis with "pizza-pie" appearance in immunocompromised patients.

Sympathetic ophthalmia: bilateral granulomatous uveitis after penetrating trauma; prevent with enucleation of blind injured eye early.

Retinoblastoma: leukocoria, strabismus, and calcification on imaging; treat with systemic chemotherapy and focal therapy.

Uveal melanoma: most common primary intraocular malignancy in adults; presents with pigmented choroidal mass.

Choroidal nevus risk factors for transformation: thickness >2 mm, subretinal fluid, orange pigment, and proximity to optic disc.

Squamous cell carcinoma of the conjunctiva: gelatinous or nodular lesion; treat with excision and cryotherapy.

Lymphoma of the eye: masquerade uveitis; vitreous cells and subretinal infiltrates; diagnosis by biopsy.

Orbital rhabdomyosarcoma: rapid proptosis in a child; treat with chemotherapy and radiation.

Primary acquired melanosis with atypia is a precursor to conjunctival melanoma.

Metastatic carcinoma to the choroid: most common intraocular malignancy overall; breast and lung primaries.

Snellen 20/20 means a letter subtends 5 arcminutes at 20 feet; the 20/200 letter subtends 5 arcminutes at 200 feet.

Myopia is corrected with a diverging (minus) lens; hyperopia with a converging (plus) lens.

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

Spherical equivalent = sphere + (cylinder/2).

Prism diopter = 100 × tan(deviation angle); it measures the deviation of a light ray in centimeters per meter.

Prentice rule: prism power = decentration (cm) × lens power (D).

Low vision magnification: M = F/4 where F is the add power in diopters; equivalently M = D/4.

Kestenbaum rule estimates magnification needed: add power = 4 / (best-corrected acuity as a fraction).

Anisometropia >2 D may cause aniseikonia; contact lenses reduce aniseikonia compared with spectacles.