ICO Advanced cheat sheet

Corneal thickness: central corneal thickness (CCT) averages about 540 µm; thinner corneas (e.g., <500 µm) raise measured intraocular pressure (IOP) by applanation and are a risk factor for glaucoma progression.

IOP measurement: Goldmann applanation tonometry is the reference standard; it is affected by CCT, corneal curvature, and astigmatism. Normal-tension glaucoma occurs with optic nerve damage despite IOP in the normal range (roughly 10–21 mmHg).

Angle assessment: gonioscopy is the reference standard for grading the anterior chamber angle; van Herick slit-lamp estimation (peripheral anterior chamber depth vs corneal thickness) is a screening surrogate.

Acute angle-closure glaucoma: presents with severe ocular pain, headache, nausea, halos, mid-dilated fixed pupil, and corneal edema; IOP is markedly elevated and the angle is closed on gonioscopy. It is an ophthalmic emergency.

Optic disc cupping: cup-to-disc ratio >0.5, asymmetry >0.2 between eyes, disc hemorrhage, and retinal nerve fiber layer thinning suggest glaucomatous damage; visual field defects respect the vertical midline.

Cataract: age-related nuclear sclerosis causes gradual painless blurring and glare; cortical and posterior subcapsular opacities cause glare and reduced contrast, especially in bright light. Surgery is indicated when vision limits function.

Diabetic retinopathy: nonproliferative stages show microaneurysms, dot-blot hemorrhages, hard exudates, and cotton-wool spots; proliferative disease shows neovascularization, which risks vitreous hemorrhage and tractional retinal detachment.

Macular degeneration: dry (atrophic) form shows drusen and geographic atrophy; wet (neovascular) form shows choroidal neovascular membranes with subretinal fluid or hemorrhage. Sudden metamorphopsia (Amsler grid distortion) suggests the wet form.

Retinal detachment: painless flashes, floaters, and a curtain-like visual field defect suggest rhegmatogenous detachment; it is an emergency requiring prompt ophthalmology referral.

Red eye triage: pain, photophobia, decreased vision, ciliary flush, and a fixed pupil point to serious disease (keratitis, uveitis, acute angle closure) rather than simple conjunctivitis.

Bacterial conjunctivitis: purulent discharge, glued lashes, and papillary reaction; viral conjunctivitis: watery discharge, follicular reaction, often bilateral and preceded by an upper respiratory infection.

Keratitis: contact lens wear is a major risk factor, especially for Pseudomonas; a corneal epithelial defect with an infiltrate and photophobia requires urgent ophthalmology review and lens removal.

Uveitis (iritis): presents with pain, photophobia, consensual photophobia, ciliary flush, and cells/flare in the anterior chamber on slit lamp. It is associated with HLA-B27 spondyloarthritis and sarcoidosis.

Scleritis: severe boring pain, often worse at night, with a violaceous scleral hue and globe tenderness; it may be associated with rheumatoid arthritis and can threaten vision.

Orbital cellulitis: proptosis, ophthalmoplegia, pain with eye movement, and fever; it is an emergency because of risk of cavernous sinus thrombosis and intracranial extension.

Papilledema: bilateral optic disc swelling from raised intracranial pressure; it typically spares visual acuity early but enlarges the blind spot and may cause transient visual obscurations.

Optic neuritis: unilateral painful vision loss, worse with eye movement, with a relative afferent pupillary defect (RAPD) and dyschromatopsia; it is associated with multiple sclerosis.

Horner syndrome: ptosis, miosis, and anhidrosis from sympathetic pathway disruption; a painful Horner syndrome suggests carotid dissection and requires urgent evaluation.

Pupil testing: a relative afferent pupillary defect (RAPD) indicates asymmetric optic nerve or extensive retinal disease; it is tested with the swinging flashlight test.

Visual acuity: Snellen or logMAR charts; pinhole testing distinguishes refractive error from media or retinal causes of reduced acuity.

Confrontation visual field testing: a screening method for gross field defects; formal perimetry (Humphrey 24-2 or 30-2) quantifies defects and is used to monitor glaucoma.

Amsler grid: detects central and paracentral metamorphopsia and scotomas, used to screen for macular disease and to monitor the wet form of macular degeneration.

Slit-lamp examination: evaluates the cornea, anterior chamber, iris, and lens; fluorescein staining with cobalt blue light identifies corneal epithelial defects and ulcers.

Dilated fundoscopy: mydriatic drops allow evaluation of the optic disc, macula, and peripheral retina; caution is needed in suspected angle closure and in patients with head injury requiring serial neurologic checks.

Ocular ultrasound: useful when the view of the fundus is obscured (e.g., dense cataract or vitreous hemorrhage) to assess for retinal detachment or intraocular mass.

Optical coherence tomography (OCT): cross-sectional retinal imaging that detects macular edema, subretinal fluid, and retinal nerve fiber layer thinning in glaucoma.

Fluorescein angiography: identifies retinal vascular leakage, neovascularization, and areas of nonperfusion; it requires intravenous fluorescein and carries a small risk of anaphylaxis.

Ocular trauma: a chemical burn requires immediate copious irrigation with saline or water before any further examination; alkali burns are more damaging than acid burns because they penetrate more deeply.

Open globe injury: signs include a peaked or irregular pupil, shallow anterior chamber, hypotony, uveal prolapse, and a positive Seidel test (fluorescein streaming from a wound). Do not apply pressure; shield the eye and refer urgently.

Retinal artery occlusion: sudden painless monocular vision loss with a pale retina and a cherry-red macula; it is a stroke equivalent requiring urgent stroke workup.

Retinal vein occlusion: painless vision loss with a blood-and-thunder fundus appearance; it is associated with hypertension, diabetes, and hyperviscosity states.

Giant cell arteritis: in a patient over 50 with headache, jaw claudication, scalp tenderness, and visual symptoms, start high-dose corticosteroids immediately and arrange temporal artery biopsy; do not delay treatment for the biopsy.

Amaurosis fugax: transient monocular vision loss, often described as a curtain descending, suggests ipsilateral carotid or retinal embolic disease and predicts stroke risk.

Endophthalmitis: acute pain, redness, and vision loss after intraocular surgery or injection, with hypopyon; it is an emergency requiring intravitreal antibiotics.

Central retinal artery occlusion and anterior ischemic optic neuropathy both cause sudden painless vision loss; the latter shows a swollen disc with an altitudinal field defect and is associated with giant cell arteritis in older adults.

Traumatic hyphema: blood in the anterior chamber after blunt trauma; it requires ophthalmology review, avoidance of aspirin and NSAIDs, and monitoring for rebleeding and elevated IOP.