OMSB Ophthalmology (OEOPTH) key terms

A measure of central visual resolution expressed as the distance at which a standard optotype subtends 5 minutes of arc, written as a fraction comparing the test distance with the distance at which a normal eye would read that line.

The sharpest letter recognition achievable once refractive error is neutralised with lenses, marking the ceiling of optical correction and the baseline against which any visual loss is judged non-refractive.

A quick screening manoeuvre in which the patient reads through a small aperture; improvement indicates uncorrected refractive error or media opacity, while no improvement suggests retinal, optic nerve or amblyopic causes.

Asymmetric pupillary constriction when a light is swung between eyes, reflecting unilateral or asymmetric disease of the retina or optic nerve on the affected side, detected with the swinging flashlight test.

A bedside comparison of the patient's peripheral field with the examiner's by presenting fingers or targets in each quadrant, useful for detecting large defects such as hemianopias or advanced glaucomatous loss.

Automated static perimetry that quantifies threshold sensitivity across the central field and reports indices such as mean deviation and pattern standard deviation, the standard tool for monitoring glaucomatous progression.

Loss of the temporal half of each visual field, localising to the optic chiasm where crossing nasal fibres are compressed, classically by a pituitary adenoma, and often accompanied by reduced colour vision.

Loss of the same half of the visual field in both eyes, indicating a retrochiasmal lesion on the opposite side of the brain; macular sparing suggests occipital rather than optic tract involvement.

Magnified examination using a variable slit of light to illuminate and optically section the lids, conjunctiva, cornea, anterior chamber, iris and lens, forming the core anterior segment assessment technique.

Slit-lamp signs of intraocular inflammation: cells are leucocytes scattering light in the aqueous, while flare is proteinaceous haze; their grading guides diagnosis and treatment of uveitis.

Examination of the anterior chamber angle using a contact lens and mirror or prism, required because total internal reflection hides the angle from direct view; it distinguishes open from closed angles.

The fluid pressure within the globe, normally roughly 10 to 21 mmHg, determined by aqueous humour production and outflow; elevated values are a major modifiable risk factor for glaucomatous damage.

The reference method for measuring intraocular pressure, using a calibrated prism to flatten a fixed area of cornea; accuracy is reduced by abnormal corneal thickness or irregular astigmatism.

Corneal thickness at the apex, measured by pachymetry; thinner corneas under-read on applanation tonometry and independently increase glaucoma risk, so it modifies interpretation of pressure readings.

Examination of the posterior segment after mydriasis, allowing systematic inspection of the optic disc, macula, vessels and peripheral retina, and essential before missing retinal tears or detachment.

Enlargement of the central pale depression of the optic nerve head with loss of neuroretinal rim tissue, assessed as the cup-to-disc ratio; progressive cupping is a hallmark of glaucoma.

Non-invasive cross-sectional imaging by low-coherence interferometry that quantifies retinal layers, macular oedema and peripapillary nerve fibre thickness, now central to diagnosing and monitoring macular and glaucomatous disease.

Imaging after intravenous fluorescein that reveals retinal vascular perfusion, leakage, staining and capillary non-perfusion, used to characterise diabetic retinopathy and guide laser or anti-VEGF treatment.

Any mismatch between the eye's optical power and its axial length so that distant images do not focus on the retina, encompassing myopia, hyperopia and astigmatism and correctable with lenses or surgery.

A refractive state in which parallel rays focus anterior to the retina, usually from excessive axial length, causing blurred distance vision and raising lifetime risk of retinal detachment and myopic maculopathy.

Reduced vision in one or both eyes from abnormal visual experience during the sensitive period, without structural cause; treatable by correcting refractive error, occlusion or penalisation if detected early.

Misalignment of the visual axes so the eyes are not simultaneously directed at the same object, classified by direction and comitance; may cause diplopia in adults and amblyopia or suppression in children.

An alternating occlusion test of each eye to reveal manifest and latent deviation, quantifying tropia and phoria and helping distinguish comitant from incomitant (paralytic) strabismus.

A white pupillary reflex in a child, an urgent red flag for retinoblastoma, congenital cataract, retinopathy of prematurity or Coats disease; any child with it needs prompt specialist assessment.

The commonest intraocular malignancy of childhood, arising from retinal precursor cells, often with leukocoria or strabismus; heritable cases carry RB1 mutations and risk of second tumours.

Opacity of the lens present at birth or early infancy that obscures the visual axis and causes dense deprivation amblyopia unless surgically removed and optically rehabilitated within the sensitive period.

Progressive loss of retinal ganglion cells and their axons producing characteristic disc cupping and field defects, with intraocular pressure the main but not sole risk factor; vision lost is irreversible.

Occlusion of the trabecular meshwork by the iris root in an anatomically crowded anterior segment, causing acute painful pressure rise with haloes, nausea and a fixed mid-dilated pupil, an emergency.

Inflammation of the iris and ciliary body producing pain, photophobia, ciliary injection and cells in the anterior chamber; associated with HLA-B27 disease, sarcoidosis and trauma, and treated with steroids and cycloplegia.

Inflammation of the cornea from infection, exposure or immune mechanisms, presenting with pain, photophobia, tearing and a corneal epithelial defect or infiltrate; microbial causes threaten sight and need urgent treatment.

A defect of corneal epithelium with underlying stromal inflammation, most often microbial after contact lens wear or trauma; scrapings for culture and intensive topical therapy are required to prevent perforation.

Corneal inflammation associated with contact lens wear, ranging from sterile infiltrates to sight-threatening microbial keratitis, especially with overnight wear or poor hygiene; requires lens removal and assessment.

Opacification of the crystalline lens reducing light transmission and causing gradual painless visual loss, glare and altered colour perception; surgery with intraocular lens implantation is the definitive treatment.

Modern cataract surgery using ultrasonic energy to emulsify the lens nucleus through a small incision, followed by aspiration of cortex and insertion of a foldable intraocular lens, giving rapid rehabilitation.

Severe intraocular infection, most often after surgery or intravitreal injection, presenting with pain, hypopyon and profound visual loss; vitreous sampling and intravitreal antibiotics are urgent.

Microvascular retinal disease from chronic hyperglycaemia, graded from non-proliferative changes such as microaneurysms and haemorrhages to proliferative neovascularisation; screening and glycaemic control reduce blindness.

Advanced diabetic eye disease with retinal neovascularisation driven by ischaemia, risking vitreous haemorrhage and tractional detachment; treated with panretinal photocoagulation or anti-VEGF agents.

Fluid accumulation in the macula from leaking retinal capillaries in diabetes, the commonest cause of vision loss in these patients; detected by clinical examination or OCT and treated with anti-VEGF injections.

Intravitreal injection of antibodies or fusion proteins that neutralise vascular endothelial growth factor, reducing neovascularisation and vascular permeability in diabetic retinopathy, macular degeneration and retinal vein occlusion.

Degeneration of the macular photoreceptors, retinal pigment epithelium and Bruch membrane in older adults; the neovascular form causes rapid distortion and loss and responds to anti-VEGF injections.

Separation of neurosensory retina from the pigment epithelium, presenting with flashes, floaters and a curtain-like field loss; rhegmatogenous cases from a retinal tear need urgent surgical repair.

Abnormal retinal vascular proliferation in premature infants exposed to supplemental oxygen, staged by location and severity; severe disease is treated with laser or anti-VEGF to prevent detachment and blindness.

Inflammation of the optic nerve, typically causing subacute unilateral painful visual loss with colour desaturation, a relative afferent pupillary defect and often a swollen disc; strongly linked to multiple sclerosis.

Infarction of the optic nerve head, usually non-arteritic and painless in older patients with vascular risk factors, or arteritic with giant cell arteritis; produces sudden altitudinal field loss with a swollen disc.

Large-vessel vasculitis of older adults that can cause irreversible anterior ischaemic optic neuropathy; suggested by headache, jaw claudication and raised inflammatory markers, and treated immediately with high-dose steroids.

Bilateral optic disc swelling from raised intracranial pressure, usually preserving central acuity but enlarging the blind spot; requires neuroimaging and investigation for mass lesions or venous thrombosis.

Raised cerebrospinal fluid pressure without a mass lesion, typically in young women with obesity, causing headache, transient visual obscurations and papilloedema; managed with weight loss and acetazolamide.

Infection of orbital tissues behind the orbital septum, causing proptosis, painful eye movement and fever, usually spreading from sinusitis; requires urgent intravenous antibiotics and imaging to exclude abscess.

Infection limited to lid tissues anterior to the orbital septum, with swelling and erythema but no proptosis, pain on eye movement or visual change; treated with oral antibiotics in most cases.

Forward displacement of the globe within the orbit, measured with an exophthalmometer, indicating mass effect, inflammation or vascular anomaly and requiring imaging and endocrine assessment where relevant.

Orbital inflammation and tissue expansion associated with autoimmune thyroid disease, causing lid retraction, proptosis, diplopia and occasionally compressive optic neuropathy; smoking worsens the course.

Retinal vascular changes from sustained high blood pressure, including arteriolar narrowing, flame haemorrhages, exudates and papilloedema in severe cases; grading reflects systemic risk.

Blockage of a branch or central retinal vein causing sectorial or widespread haemorrhage, oedema and visual loss, associated with hypertension, diabetes and glaucoma; macular oedema is treated with anti-VEGF.

Systematic evaluation after injury covering acuity, pupil reactions, globe integrity, anterior chamber, fundus and orbital signs, with urgent imaging when a retained intraocular or orbital foreign body is suspected.

Full-thickness breach of cornea or sclera after trauma, suggested by a shallow anterior chamber, peaked pupil or uveal prolapse; requires a protective shield, systemic antibiotics and urgent surgical repair.

Corneal and conjunctival damage from acid or alkali exposure, with alkalis penetrating more deeply; immediate copious irrigation is the priority before any detailed examination or referral.

The route from retina through optic nerve, chiasm, optic tract, lateral geniculate nucleus and optic radiations to occipital cortex, whose lesions produce field defects of characteristic patterns.

Reduced vision from damage to the occipital visual cortex despite a normal eye examination, often with macular sparing, preserved pupillary responses and sometimes unawareness of the deficit.