OP9.1-5 | Retina, Optic Nerve and Visual Pathway — Glossary

Criteria for severe NPDR: haemorrhages in all 4 retinal quadrants, OR venous beading in 2 or more quadrants, OR IRMA in 1 or more quadrants; meeting any one criterion indicates severe NPDR with 50% progression risk to PDR within 12 months.

Ischaemia of the anterior optic nerve; arteritic form from giant cell arteritis (bilateral emergency); non-arteritic form from atherosclerotic risk factors (altitudinal field loss, no proven treatment).

Intravitreal injection of agents that block vascular endothelial growth factor (ranibizumab, bevacizumab, aflibercept), used to treat centre-involved DME and as adjunct in PDR; anti-VEGF is now first-line for DME.

Age-Related Eye Disease Study 2 — a formulation of antioxidant vitamins and minerals (vitamins C and E, zinc, copper, lutein, zeaxanthin) shown to reduce the risk of progression from intermediate to advanced AMD.

A point where a retinal arteriole crosses over a retinal venule, sharing an adventitial sheath; when the arteriole is sclerotic (hypertension), it compresses the venule, predisposing to BRVO at that site.

Compression of the retinal vein where it crosses under a thickened retinal artery at an arteriovenous crossing; a sign of hypertensive retinopathy.

Compression of a retinal vein at an arteriovenous crossing by a thickened arteriole, appearing as apparent tapering or disappearance of the vein at the crossing point; a sign of grade II hypertensive retinopathy.

Loss of both temporal (lateral) visual fields, respecting the vertical midline; caused by compression of the crossing nasal fibres at the optic chiasm; most commonly from a pituitary macroadenoma.

The dramatic fundoscopic appearance of CRVO: dense flame haemorrhages in all four retinal quadrants, markedly dilated and tortuous veins, and disc oedema; the haemorrhages resemble 'blood splattered across the fundus'.

A characteristic fundoscopic finding in retinitis pigmentosa: clusters of black pigment in the mid-peripheral retina shaped like cortical bone spicules, representing RPE cell migration into the degenerating outer retina.

Occlusion of a branch of the central retinal artery, typically embolic, causing a segmental (quadratic or altitudinal) visual field defect with localised retinal pallor in the affected territory.

Thrombosis of a retinal branch vein, most commonly superotemporal, at an arteriovenous crossing; produces sector-limited flame haemorrhages, macular oedema, and risk of neovascularisation.

A neurosensory retinal detachment of the macula caused by a localised RPE defect allowing fluid from the choriocapillaris to accumulate beneath the retina; affects young-middle-aged men; often resolves spontaneously.

A bright red circular area at the fovea against a surrounding pale ischaemic retina, pathognomonic of CRAO; caused by preserved choroidal perfusion through the thin, avascular foveal tissue when the surrounding retina is ischaemic.

Growth of new blood vessels from the choriocapillaris through Bruch's membrane into the sub-RPE or subretinal space; the defining feature of wet (neovascular) AMD; treated with intravitreal anti-VEGF.

A high-power convex lens (e.g. 20D or 28D) used with the indirect ophthalmoscope, held between the examiner and the patient to create a real aerial image of the fundus.

Total bilateral visual loss from bilateral occipital cortex destruction; pupillary reflexes are preserved because the pupillary pathway diverges from the optic tract before the lateral geniculate nucleus.

A white fluffy retinal lesion representing ischaemic infarction of the nerve fibre layer (a microinfarct), seen in hypertensive retinopathy, diabetic retinopathy, and HIV retinopathy.

Sudden, complete occlusion of the central retinal artery causing total monocular visual loss with pale ischaemic retina and cherry-red spot at the fovea; a true ocular emergency with treatment window of approximately 90 minutes.

Thrombotic occlusion of the central retinal vein producing the 'blood-and-thunder' fundus: 4-quadrant flame haemorrhages, dilated tortuous veins, and disc oedema; classified as ischaemic or non-ischaemic.

Macular oedema meeting ETDRS criteria: retinal thickening or hard exudates within 500 microns of the foveal centre, or a zone of retinal thickening ≥1 disc area within 1 disc diameter of the fovea; the leading cause of visual loss in DR.

The ratio of the cup diameter to the optic disc diameter, normally 0.3–0.4; CDR >0.5 or inter-eye asymmetry >0.2 is suspicious for glaucoma.

Accumulation of fluid in cystoid spaces within the macula, producing a petaloid pattern on FFA and cross-sectional cystic spaces on OCT; caused by multiple conditions including post-operative (Irvine-Gass), uveitis, and retinal vascular disease.

The focusing adjustment on a direct ophthalmoscope that compensates for the refractive errors of both the examiner and the patient (range approximately +20 to −20 dioptres).

A round, dark-red haemorrhage in the deep retinal layers (inner nuclear and outer plexiform layers), characteristic of diabetic retinopathy; appears as a blot rather than the flame-shape of superficial haemorrhages.

Yellow-white deposits of extracellular material (waste products) that accumulate beneath the RPE between the RPE and Bruch's membrane; the hallmark of dry AMD; large soft drusen carry highest risk of progression to wet AMD.

An idiopathic peripheral retinal periphlebitis predominantly affecting young Indian males, characterised by inflammatory sheathing of peripheral veins, ischaemia, neovascularisation, and recurrent vitreous haemorrhage.

A fibrate lipid-lowering agent shown in the FIELD and ACCORD-Eye trials to reduce DR progression beyond its lipid-lowering effect; used as adjunctive systemic therapy in DR management.

Imaging technique using intravenous fluorescein dye to visualise retinal vascular perfusion and leakage; used in DR to map areas of capillary non-perfusion, identify leaking microaneurysms, and characterise neovascularisation.

A bright pinpoint of reflected light at the foveola seen on ophthalmoscopy in healthy, young patients; its absence suggests macular oedema or atrophy.

The interior posterior surface of the eye as seen on ophthalmoscopy, including the retina, optic disc, macula, and retinal vessels.

A systemic granulomatous vasculitis affecting large and medium vessels in patients typically over 50, capable of causing CRAO by occluding the ophthalmic artery or central retinal artery; presents with headache, jaw claudication, elevated ESR/CRP; requires immediate high-dose steroids.

A bright yellow, sharply defined deposit of lipoprotein and lipid-laden macrophages in the outer retinal layers from leaking retinal vessels; seen in diabetic and hypertensive retinopathy.

A cholesterol embolus visible as a bright, refractive yellowish plaque in a retinal arteriole at a branching point, indicating atheroembolism from the carotid artery; associated with BRAO and CRAO.

Loss of the same half of the visual field (e.g. left half) in both eyes; indicates a retrochiasmal lesion in the contralateral hemisphere (optic tract, radiation, or cortex).

Raised ICP without an identifiable cause; typically in obese young women; presents with headache, papilloedema, and transient visual obscurations; treated with acetazolamide, weight loss, and optic nerve sheath fenestration if vision is threatened.

A binocular headset-mounted instrument that uses a condensing lens to produce a wide-field, inverted, real image of the fundus; allows examination of the entire retina including the periphery.

Dilated, tortuous intraretinal capillaries that shunt blood around areas of capillary non-perfusion; a marker of severe NPDR and impending neovascularisation; IRMA lies within retinal layers (unlike NVE which projects on the surface).

A severe form of CRVO characterised by extensive capillary non-perfusion (>10 disc areas on FFA), reduced visual acuity, RAPD, and approximately 30% risk of rubeosis iridis and neovascular glaucoma within 3 months.

A grading system for hypertensive retinopathy: Grade I (arteriolar narrowing), Grade II (AV nipping), Grade III (haemorrhages, exudates, cotton-wool spots), Grade IV (Grade III + papilloedema = hypertensive emergency).

An abnormal white pupillary reflex (replacing the normal red reflex), indicating serious pathology such as retinoblastoma, dense cataract, or retinal detachment; urgent referral is mandatory.

The central 5 mm area of the retina responsible for central and colour vision; contains the fovea at its centre and is identified on fundoscopy as slightly darker than the surrounding retina.

Preservation of central (foveal) vision in occipital cortex lesions; occurs because the macular cortical representation at the occipital pole has dual blood supply (PCA and MCA collaterals).

A pattern of hard exudates arranged radially around the macula along Henle's fibre layer, seen in grade III-IV hypertensive retinopathy; resembles a star or sunburst pattern.

The anterior loop of the inferior optic radiation fibres (representing the superior visual field of the contralateral hemifield) that curves through the temporal lobe; lesions here cause superior homonymous quadrantanopia.

A focal, saccular outpouching of a retinal capillary wall — the earliest fundoscopic sign of diabetic retinopathy — visible as a tiny red dot smaller than the diameter of a major retinal vein.

A severe secondary glaucoma caused by a fibrovascular membrane growing across the anterior chamber angle (following rubeosis iridis), preventing aqueous outflow; characterised by markedly elevated IOP and severe pain.

Pathological growth of new, fragile retinal blood vessels — on the disc (NVD) or elsewhere (NVE) — driven by VEGF in ischaemic conditions such as proliferative diabetic retinopathy.

Growth of new, fragile blood vessels on the retinal surface at sites other than the disc; hallmark of PDR along with NVD; projects into vitreous and bleeds easily.

Growth of new, fragile blood vessels on or within one disc diameter of the optic disc surface, driven by VEGF from ischaemic retina; the defining hallmark of PDR when on the disc.

A milder form of CRVO with less capillary non-perfusion (<10 disc areas on FFA), better visual acuity, absent RAPD, and lower risk of neovascular complications; better visual prognosis.

Early to intermediate stages of diabetic retinopathy characterised by microaneurysms, haemorrhages, exudates, and ischaemic changes — but WITHOUT neovascularisation; classified as mild, moderate, or severe.

Digital pressure on the closed eyelid alternately applied and released to produce IOP oscillations, aiming to dislodge an embolus from the central retinal artery; used as an emergency manoeuvre in acute CRAO.

A landmark RCT demonstrating that IV methylprednisolone hastens visual recovery in optic neuritis by ~2 weeks but does not improve final 1-year visual acuity; oral prednisone alone increased relapse rate.

An instrument used to examine the interior of the eye, particularly the retina, optic disc, and retinal vessels, by illuminating the fundus and neutralising the optical system of the eye.

End-stage disc pallor from any process destroying optic nerve axons; primary = sharp pale disc from direct damage (glaucoma, compression, toxic); secondary = follows papilloedema; progressive visual loss and RAPD.

The X-shaped junction of the two optic nerves, located just anterior to the pituitary gland; site of partial decussation — nasal (medial) fibres from each eye cross to the contralateral optic tract; lesions produce bitemporal hemianopia.

The visible head of the optic nerve on fundoscopy, where nerve fibres and retinal vessels enter/exit the eye; appears as a pale-pink oval, 1.5 mm in diameter.

Inflammatory demyelination of the optic nerve causing subacute unilateral visual loss with painful eye movement, RAPD, colour desaturation, and central scotoma; strongly associated with multiple sclerosis.

Non-invasive retinal imaging using light waves to produce cross-sectional images of retinal layers at micron-level resolution; gold standard for detecting and monitoring diabetic macular oedema.

Laser treatment applied to the peripheral retina to destroy ischaemic retinal tissue and reduce VEGF production, thereby causing regression of neovascularisation in PDR.

Inflammatory swelling of the optic disc, clinically similar in appearance to papilloedema but typically unilateral, painful, and causing acute visual loss (optic neuritis).

Bilateral optic disc swelling caused by raised intracranial pressure; features include blurred disc margins, loss of venous pulsations, disc haemorrhages, and eventual vision loss.

A surgical procedure to remove the vitreous (and any blood, fibrous tissue) from the posterior segment, indicated for non-clearing vitreous haemorrhage, tractional retinal detachment, and other advanced PDR complications.

A severe stage of diabetic retinopathy defined by the presence of neovascularisation (NVD and/or NVE) driven by VEGF from ischaemic retina; complicated by vitreous haemorrhage and tractional retinal detachment.

A normal central pallor within the optic disc where the optic nerve fibre bundles exit; expressed as the cup-to-disc ratio (CDR), normally <0.5.

A pituitary adenoma >10 mm in diameter that can grow superiorly to compress the optic chiasm, causing bitemporal hemianopia; managed by transsphenoidal surgery (or dopamine agonists for prolactinomas).

Posterior retinal vascular dilation and tortuosity in the four quadrants at or near the disc in ROP, indicating active severe disease requiring treatment; absence of plus disease indicates less severe ROP.

Age-related liquefaction and collapse of the vitreous gel causing separation from the retinal surface; normal with ageing, but can cause retinal tears by traction at vitreoretinal adhesions.

A difference in pupillary light reflex between the two eyes on swinging flashlight test — the affected pupil dilates when the light swings to it; indicates reduced afferent input from the diseased optic nerve or extensive retinal ischaemia.

A tumour suppressor gene on chromosome 13q14 encoding the retinoblastoma protein (pRb); biallelic loss causes retinoblastoma; the prototype of Knudson's two-hit hypothesis of tumour suppressor inactivation.

The orange-red glow seen when a light is directed into the pupil from arm's length, caused by reflection from the vascular choroid and retina; absence or asymmetry is pathological.

A group of inherited retinal dystrophies characterised by progressive rod (then cone) degeneration; classic fundoscopic triad: bone-spicule pigmentation, arteriolar attenuation, waxy disc pallor; presents with nyctalopia then tunnel vision; no proven cure.

The most common primary intraocular malignancy of childhood, arising from biallelic RB1 tumour suppressor gene loss; presents with leukocoria; life-threatening if extraocular extension occurs; do NOT biopsy.

Optic neuritis where the inflammation is posterior to the optic disc, leaving the disc appearing normal on fundoscopy; classic teaching: 'the patient sees nothing and the doctor sees nothing' (normal fundus with severe visual loss).

Retinal detachment caused by a break (tear or hole) in the retina allowing vitreous fluid to accumulate between the neurosensory retina and RPE; the most common type; surgical emergency.

A vasoproliferative disorder of the developing retinal vessels in premature infants, classified by zone (I-III) and stage (1-5); treated with laser or intravitreal anti-VEGF at type 1 ROP criteria.

Neovascularisation of the iris from VEGF released by ischaemic retina, a complication of ischaemic CRVO; if untreated, progresses to neovascular glaucoma by closure of the anterior chamber angle.

Presence of pigment granules (RPE cells) in the anterior vitreous, appearing as brown/black 'tobacco dust'; a sign of retinal break or early retinal detachment.

Normal rhythmic pulsations of the central retinal vein visible at the optic disc; their presence suggests intracranial pressure is not significantly elevated.

Loss of the upper quarter of the visual field on the same side in both eyes ('pie in the sky'); caused by damage to the inferior optic radiation (Meyer's loop) in the temporal lobe.

Retinal detachment caused by fibrovascular membranes on the vitreoretinal interface physically pulling the retina off the RPE without a retinal break; commonest cause is proliferative diabetic retinopathy.

A short-acting anticholinergic mydriatic (1%) used to dilate the pupil for fundoscopy; onset 20 minutes, effect lasts 2–4 hours, causes temporary blurring of near vision.

An irregular, sausage-like calibre variation of retinal veins, indicating severe retinal ischaemia; a feature of severe NPDR and a marker of high risk of progression to PDR.

An electrophysiological test measuring the latency and amplitude of the cortical response to a visual stimulus; prolonged P100 latency is diagnostic of demyelinating optic neuritis, even subclinically.

Haemorrhage from ruptured new vessels of PDR into the vitreous cavity, causing sudden painless visual loss; may clear spontaneously or require vitrectomy.