Retinal Disorders

Embolic/ischemic (CRAO, BRAO, amaurosis fugax)

• Carotid atherosclerotic plaque: the most common embolic source in older adults; cholesterol emboli (Hollenhorst plaques) lodge at arteriolar bifurcations
• Cardiac emboli: atrial fibrillation, valvular disease, endocarditis, and left ventricular thrombus; in patients under 50 consider patent foramen ovale, hypercoagulable states, sickle cell disease, and injected particulate matter in IV drug use
• Giant cell arteritis: arteritic occlusion from granulomatous inflammation of the ophthalmic/posterior ciliary arteries — always the exception to "embolic" thinking in patients over 50

Venous stasis/thrombotic (CRVO, BRVO)

• Hypertension: the dominant systemic association; arteriolar sclerosis compresses the vein at the shared adventitial sheath of the arteriovenous crossing (mechanism of BRVO)
• Open-angle glaucoma: a local, modifiable risk factor via elevated intraocular pressure at the lamina cribrosa
• Hyperviscosity/hypercoagulability: myeloproliferative disease, paraproteinemia, oral contraceptives, antiphospholipid syndrome — the pathway examiners choose in a young patient

Metabolic/microvascular

• Diabetic retinopathy: duration of diabetes is the single strongest predictor; modifiable contributors are hyperglycemia, hypertension, dyslipidemia, and diabetic kidney disease. The ADA Standards of Care flags pregnancy as a period of accelerated progression requiring an eye exam before or early in pregnancy

Degenerative/structural

• AMD: non-modifiable — advancing age (strongest), White race, family history, CFH and ARMS2 polymorphisms; modifiable — cigarette smoking (strongest modifiable factor), hypertension, obesity, low dietary carotenoid intake
• Rhegmatogenous detachment: axial myopia, prior cataract surgery (pseudophakia), lattice degeneration, blunt/penetrating trauma, posterior vitreous detachment, and connective tissue disease (Marfan, Stickler)

Iatrogenic and infectious

• Drug toxicity: hydroxychloroquine (dose- and duration-dependent bull's-eye maculopathy; AAO screening guidance), thioridazine
• Retinopathy of prematurity: low gestational age, low birth weight, supplemental oxygen (AAP/AAO joint screening statement)
• CMV retinitis: CD4 count below 50 cells/µL

Vascular Retinal Disorders

• Central retinal artery occlusion (CRAO): Thromboembolism or vasculitis causes acute cessation of blood flow to the inner retina; results in ischemic necrosis of inner retinal layers within minutes to hours
• Central retinal vein occlusion (CRVO): Thrombosis of the central retinal vein leads to venous stasis, retinal edema, and hemorrhage; may occur from hypercoagulability, compression, or vasculitis
• Branch vessel occlusions: Localized thrombosis affects sectoral retinal territory; pathophysiology identical to central occlusions but with limited impact zone
• Diabetic retinopathy: Chronic hyperglycemia causes pericyte loss, increased vascular permeability, endothelial cell dysfunction, and formation of acellular capillaries; progresses from nonproliferative (microaneurysms, hemorrhages) to proliferative stage (neovascularization)

Degenerative/Structural Disorders

• Age-related macular degeneration (AMD): Accumulation of lipofuscin and drusen in Bruch's membrane with RPE dysfunction; dry (atrophic) form involves geographic atrophy, while wet (exudative) form involves choroidal neovascularization with retinal fluid and hemorrhage
• Retinal detachment: Separation of neurosensory retina from RPE; rhegmatogenous detachment occurs through retinal breaks, tractional detachment results from fibroproliferative membranes (severe diabetic retinopathy, proliferative vitreoretinopathy), and exudative detachment involves subretinal fluid without retinal break
• Retinitis pigmentosa: Progressive photoreceptor degeneration (rod-predominant initially) due to mutations in photoreceptor genes; characterized by progressive loss of peripheral vision followed by central vision loss

Inflammatory/Infectious

• Retinitis: Viral (CMV, ARN) or parasitic infection causes direct inflammation and necrosis of retinal tissue with associated hemorrhage and edema
• Acute retinal necrosis (ARN): Varicella-zoster virus or herpes simplex virus causes fulminant retinal inflammation and hemorrhagic necrosis, particularly in immunocompromised patients

Acute Vascular Events

• CRAO: Sudden, painless, unilateral vision loss (often described as "shade coming down"); may be preceded by amaurosis fugax (transient monocular vision loss); fundoscopy shows pale, whitened retina with cherry-red spot at macula (choroidal circulation preserved)
• CRVO: Sudden vision loss with "blood and thunder" fundus appearance—extensive retinal hemorrhages, cotton-wool spots, venous dilation and tortuosity; less dramatic vision loss than CRAO depending on ischemic severity
• Branch retinal artery/vein occlusion: Sectoral vision loss corresponding to vascular distribution; altitudinal (superior or inferior half) field defects common

Diabetic Retinopathy

• Nonproliferative stage: Often asymptomatic; microaneurysms, dot-blot hemorrhages, hard exudates, cotton-wool spots on examination
• Proliferative stage: Symptoms include floaters (vitreous hemorrhage), flashing lights, sudden vision loss; fundoscopy reveals neovascularization at disc or elsewhere, preretinal hemorrhage
• Diabetic macular edema: Blurred central vision, metamorphopsia; OCT shows retinal thickening at macula

AMD

• Dry AMD: Gradual, progressive central vision loss; drusen visible on fundoscopy; geographic atrophy appears as well-demarcated areas of RPE loss
• Wet AMD: Sudden or rapid central vision loss; metamorphopsia (wavy lines), scotoma; subretinal fluid, hemorrhage, lipid exudates visible; may progress rapidly if untreated

Retinal Detachment

• Classic triad: Flashing lights (photopsia from vitreous traction), floaters (vitreous blood or debris), and visual field defect (shadow or curtain moving across visual field)
• Macula-involving detachment is a retinal emergency requiring urgent intervention
• Rhegmatogenous detachment more common; risk factors include myopia, prior ocular surgery, lattice degeneration, family history

Retinitis Pigmentosa

• Night blindness (nyctalopia) is typically first symptom, followed by progressive peripheral visual field loss (tunnel vision)
• Fundoscopy reveals bone-spicule pigmentation in periphery, waxy optic disc pallor, attenuated vessels
• Often associated with systemic features: Kearns-Sayre syndrome (cardiac conduction abnormalities), Refsum disease (peripheral neuropathy)

Retinitis (Infectious)

• CMV retinitis (immunocompromised, typically CD4 <50): Floaters, photopsia, visual field defects; hemorrhagic or granular appearance; "cottage cheese and ketchup" pattern with hemorrhage and granular infiltrates
• ARN: Severe vitritis, pain, rapid progressive retinal whitening, hemorrhagic necrosis; high risk of rhegmatogenous detachment

Clinical Examination

• Dilated fundoscopy: Essential; identify lesions, hemorrhage patterns, neovascularization, optic disc pallor, retinal breaks
• Visual acuity and visual fields: Quantify functional loss; CRAO classically presents with light perception or counting fingers vision
• Afferent pupillary defect (APD): Present in CRAO and other optic nerve/retinal pathology affecting large retinal areas

Imaging

• Optical coherence tomography (OCT): Gold standard for retinal thickness, macular edema detection, drusen quantification in AMD; shows layer-by-layer retinal architecture
• Fundus photography and fluorescein angiography (FA): FA shows perfusion defects in vascular occlusions, neovascularization leakage in diabetic retinopathy and wet AMD; identifies ischemic vs nonischemic CRVO
• Indocyanine green (ICG) angiography: Better visualization of choroidal neovascularization, particularly in AMD
• B-scan ultrasonography: Essential when fundus view obscured (vitreous hemorrhage); shows retinal detachment, posterior segment masses

Laboratory/Systemic Workup

• CRAO/CRVO: Evaluate for embolic source (carotid ultrasound, echocardiography, EKG), hypercoagulability (thrombophilia panel), vasculitis (ESR, CRP, ANA)
• Diabetic retinopathy: Glycemic control markers (HbA1c), blood pressure; Early Treatment Diabetic Retinopathy Study (ETDRS) classification
• AMD: Optical coherence tomography angiography (OCTA) increasingly used; no specific labs but cardiovascular risk factor assessment

Specific Diagnostic Criteria

• Retinal detachment: Clinical diagnosis by dilated exam and ultrasonography; location characterized as macula-on vs macula-off
• Retinitis pigmentosa: Combination of night blindness, progressive peripheral field loss, bone-spicule pigmentation, and electroretinography (ERG) showing reduced amplitudes
• CMV retinitis: Clinical diagnosis in immunocompromised patients; rapid progression distinguishes from other retinitis

Acute Vascular Occlusions (Retinal Emergencies)

CRAO

• Acute phase (within hours): Ocular massage, anterior chamber paracentesis to lower intraocular pressure and dislodge embolus

• Neovascular glaucoma: rubeosis iridis with fibrovascular membrane obstructing the trabecular meshwork; classically follows ischemic CRVO (the "90-day glaucoma") and proliferative diabetic retinopathy. Signals: pain, corneal edema, markedly elevated intraocular pressure, iris vessels on undilated slit-lamp exam. Emergency — requires urgent anti-VEGF and panretinal photocoagulation
• Vitreous hemorrhage: fragile neovascular fronds bleed into the vitreous; sudden floaters or dense painless vision loss with loss of the red reflex. B-scan ultrasound when the fundus cannot be seen
• Tractional retinal detachment: fibrovascular membranes contract on the retinal surface in proliferative diabetic retinopathy; a concave, taut detachment without a break

Disease-specific

• Macula-off retinal detachment: photoreceptors separated from the RPE lose their choroidal nutrient supply; central acuity often does not fully recover even after successful repair — emergency, hence the urgency of macula-on cases
• Proliferative vitreoretinopathy: RPE cells migrate and form contractile membranes; the leading cause of redetachment after repair
• CRAO as a stroke equivalent: the AHA/ASA classifies retinal artery occlusion within the acute cerebral ischemia spectrum — emergent evaluation for carotid and cardiac sources is mandatory
• Giant cell arteritis with contralateral blindness: if untreated; ACR/EULAR guidance is immediate high-dose glucocorticoids before biopsy results — emergency
• Geographic atrophy and choroidal neovascularization: dry AMD may convert to wet AMD — new metamorphopsia on home Amsler grid is the alarm sign

Treatment-related

• Intravitreal anti-VEGF injection: acute endophthalmitis (pain, hypopyon, worsening vision days after injection — emergency), transient IOP spike, rarely retinal detachment
• Panretinal photocoagulation: ablates peripheral retina — permanent peripheral field constriction, impaired night vision, transient worsening of macular edema
• Vitrectomy: near-universal progressive nuclear cataract; scleral buckle can induce myopic shift and diplopia

• Sudden painless monocular vision loss is the stem's fork in the road: pale retina with a cherry-red spot = CRAO; blood and thunder fundus = CRVO; curtain/shade with flashes and floaters = rhegmatogenous detachment; dense floaters with lost red reflex in a diabetic = vitreous hemorrhage.
• CRAO is a stroke, not just an eye problem: the single best next step is emergent evaluation on an acute stroke pathway per AHA/ASA (neuroimaging, carotid imaging, cardiac rhythm assessment), plus immediate ESR/CRP in anyone over 50 to exclude giant cell arteritis. If GCA is suspected, start high-dose glucocorticoids before the temporal artery biopsy (ACR/Vasculitis Foundation) — do not wait for pathology.
• The cherry-red spot distractor: it also appears in Tay-Sachs and Niemann-Pick, but those are bilateral in infants with neurodegeneration. In an older adult with acute unilateral loss, it is CRAO.
• New flashes and floaters demand a dilated fundus exam the same day, not reassurance — you are looking for a retinal break behind a posterior vitreous detachment before it progresses to detachment.
• Metamorphopsia = wet AMD until proven otherwise: straight lines appearing wavy on an Amsler grid points to choroidal neovascularization; the treatment is intravitreal anti-VEGF, not laser or supplements.
• AREDS2 supplements (vitamin C, vitamin E, zinc, copper, lutein/zeaxanthin) slow progression in intermediate or advanced dry AMD only — they do not prevent AMD, do not help early disease, and beta-carotene was removed because it increased lung cancer risk in smokers.
• Screening is the ADA's answer for diabetes: dilated exam at diagnosis in type 2 diabetes and within 5 years of diagnosis in type 1, then at intervals guided by findings; the strongest predictor of retinopathy is disease duration.
• Bone-spicule pigmentation with nyctalopia and a reduced ERG is retinitis pigmentosa; cottage cheese and ketchup retinitis with CD4 below 50 is CMV.