OP4.1-10 | Cornea, Keratitis and Eye Donation — Glossary

Supplementary lacrimal secretory tissue: glands of Krause (in the fornices) and Wolfring (at the upper lid margin); provide basal tear secretion when the main lacrimal gland output is reduced.

A dense corneal scar in which the iris has become adherent to the posterior surface of the cornea, typically following corneal perforation sealed by iris plugging; associated with corectopia (displaced pupil).

A low-speed motorised burr attachment for slit-lamp use, designed to gently debride rust rings from the corneal stroma after iron foreign body removal.

Ocular chemical injury from alkali agents (lime, ammonia); more devastating than acid burns because alkali undergoes saponification causing continuing deep penetration; first treatment = immediate copious irrigation.

DED caused by insufficient aqueous secretion from the lacrimal glands, as in Sjögren's syndrome, lacrimal gland scarring, or medication-related suppression.

A superficial calcium deposition in Bowman's layer and anterior stroma, appearing as a horizontal grey-white band across the interpalpebral zone; associated with hypercalcaemia, chronic uveitis, and phthisis bulbi; treated with chelation (EDTA) or PTK.

A large, plano soft contact lens placed over the cornea to protect a large epithelial defect and reduce discomfort; useful for large post-FB-removal epithelial defects.

Topical anaesthetic eye drop (0.4%) alternative to proparacaine; procedural use only.

Foamy, triangular whitish deposits on the bulbar conjunctiva (typically temporal) in vitamin A deficiency; WHO stage X1B; conjunctival, not corneal.

Presenting visual acuity less than 3/60 in the better eye, or visual field less than 10 degrees around central fixation.

An acellular anterior condensation of collagen fibrils beneath the corneal epithelium; cannot regenerate and heals by scarring.

Advanced corneal oedema due to endothelial failure, in which epithelial blisters (bullae) form, rupture, and cause pain.

Enlarged, globe with stretched cornea secondary to chronically elevated IOP in congenital glaucoma; associated with corneal oedema and Haab's striae.

Rare autoimmune condition combining non-syphilitic interstitial keratitis with audio-vestibular symptoms (sensorineural hearing loss and vertigo); treated with systemic corticosteroids.

Displacement of the pupil from its normal central position, seen in adherent leukoma where the iris is pulled toward the corneal scar.

Bilateral corneal opacity causing visual acuity below the blindness threshold; the second leading cause of avoidable blindness in India after cataract.

Treatment for progressive keratoconus using riboflavin drops and UV-A irradiation to form covalent bonds between collagen fibrils, halting ectasia.

Failure of the endothelial pump, typically when cell density falls below ~500 cells/mm², leading to stromal oedema, bullous keratopathy, and loss of transparency.

A single post-mitotic hexagonal cell layer (~2,500–3,000 cells/mm²) that maintains corneal transparency by actively pumping water from the stroma into the aqueous humour.

The outermost 5–6 cell layer of the cornea; non-keratinised stratified squamous epithelium regenerated from limbal stem cells every 7–10 days.

Any extraneous particle (metallic, organic, glass, stone, etc.) embedded in or on the corneal surface; classified by material type and depth of penetration.

Ingrowth of blood vessels into the normally avascular cornea, driven by VEGF under conditions of chronic hypoxia or inflammation, compromising transparency.

Full-thickness corneal ulcer breakthrough, with aqueous escaping; the iris may plug the defect (iris prolapse); requires emergency surgical management.

The middle and thickest layer (~90% of corneal thickness), composed of approximately 200 orthogonal Type I collagen lamellae with interspersed keratocytes.

The junction between the transparent cornea and the opaque white sclera; site of limbal stem cells, Schlemm's canal, and the trabecular meshwork.

Retrieval of the anterior segment (cornea + a rim of sclera) from the deceased donor without removing the entire globe; less disfiguring, allows prosthetic eye insertion.

Fatal prion disease; an absolute contraindication to corneal donation because the abnormal prion protein cannot be destroyed by standard sterilisation; transplanted CJD-infected corneas have caused recipient deaths.

A topical agent (cyclopentolate 1%, homatropine 2%) that paralyses the ciliary muscle, relieving ciliary spasm and its associated deep aching pain following corneal FB removal; used for 2-3 days post-procedure.

Topical immunomodulatory drops (calcineurin inhibitor) that reduce T-cell-mediated inflammation in the lacrimal gland and conjunctiva; first-line anti-inflammatory treatment for moderate-severe DED; effect develops over 3–6 months.

Replacement of host epithelium and stroma down to (but not including) Descemet's membrane; preserves host endothelium; eliminates risk of endothelial rejection; indicated for anterior-mid stromal disease with healthy endothelium.

The time from death to placement of the donor cornea in preservation medium; ideally ≤6 hours, acceptable up to 12 hours; extended by body refrigeration.

Surgical replacement of epithelium and stroma down to Descemet's membrane, preserving the host endothelium; avoids endothelial rejection; preferred for anterior stromal disease with healthy endothelium.

The classic HSV epithelial keratitis lesion: a branching, tree-like corneal epithelial defect with terminal bulbs at each branch tip; stains with both fluorescein and rose bengal.

The basement membrane of the corneal endothelium; highly resistant to collagenases and preserved in deep anterior lamellar keratoplasty (DALK).

Forward bulging of Descemet's membrane through a thinned corneal stroma destroyed by ulceration; an ophthalmological emergency indicating impending perforation.

Replacement of Descemet's membrane and endothelium only (no posterior stroma); the most selective endothelial keratoplasty; fastest visual recovery and lowest rejection rate; technically most demanding.

A multifactorial disease of the ocular surface characterised by instability and hyperosmolarity of the tear film, with symptoms of discomfort and visual disturbance, and potential ocular surface damage.

Replacement of host Descemet's membrane and endothelium with a thin posterior stroma + Descemet's + endothelium donor lenticule; indicated for endothelial failure without significant stromal opacity.

Endothelial keratoplasty procedures replacing only Descemet's membrane and endothelium through a small incision; indicated for endothelial failure without significant stromal opacity; faster visual recovery and lower rejection than PK.

Eye Bank Association of India — the apex body governing eye banking standards, training, and accreditation of eye banks in India.

An advancing line of elevated epithelium across the donor cornea, representing epithelial graft rejection; the least serious rejection type; responds readily to topical steroids.

A yellowish-white inflammatory deposit on the posterior corneal surface (endothelium) seen in fungal keratitis; visible on slit-lamp as a posterior opacity.

The Na-K-ATPase and carbonic anhydrase-powered system in corneal endothelial cells that keeps stromal water content at ~78%, preventing oedema.

The most serious form of corneal graft rejection, involving T-cell destruction of donor endothelial cells, manifesting as the Khodadoust line; irreversible if untreated; treated with intensive topical and systemic steroids.

Surgical removal of the entire globe from the orbit; a retrieval method for eye donation; being replaced by corneoscleral rim excision in modern eye banking practice.

The gap in the corneal epithelium left after FB removal, visualised by fluorescein staining; heals within 24-48 hours by migration and proliferation of surrounding epithelial cells.

DED caused by excessive tear evaporation despite normal aqueous production, most commonly from meibomian gland dysfunction causing lipid layer deficiency.

The integrated process of collecting, evaluating, preserving, and distributing donor corneal tissue for keratoplasty; regulated in India by THOA 1994 and overseen by EBAI.

The voluntary posthumous gift of a deceased individual's corneas (and possibly other ocular tissue) for transplantation, research, or training purposes; living eye donation is not performed.

The irregular, feather-like extensions of a fungal corneal ulcer infiltrate, reflecting hyphal growth into the surrounding stroma; pathognomonic of filamentous fungal keratitis.

A brownish ring of iron (haemosiderin) deposition in basal corneal epithelial cells at the base of the cone in keratoconus; best seen with cobalt blue filter.

An expanded, irregular map-shaped HSV epithelial ulcer resulting from progression of a dendritic ulcer, particularly after topical steroid use without antiviral cover.

Empty non-functional blood vessel channels remaining in the corneal stroma after resolution of syphilitic or other interstitial keratitis; visible as fine linear stromal opacities.

Specialised epithelial cells in the conjunctiva that secrete mucin, transforming the hydrophobic corneal surface into a wettable substrate for the aqueous tear layer.

Horizontal breaks in Descemet's membrane in congenital glaucoma, caused by stretching of the enlarged cornea; pathognomonic of buphthalmos.

The triad of congenital syphilis: interstitial keratitis + Hutchinson's teeth (notched upper incisors) + sensorineural nerve deafness.

A white, layered, sterile inflammatory exudate (fibrin and leukocytes) settling inferiorly in the anterior chamber in severe keratitis; shifts with head position; indicates severe inflammatory burden, not direct AC infection.

The relative resistance of the normal avascular cornea to immune rejection, due to absence of blood vessels, lymphatics, and MHC class II-expressing APCs; lost when cornea becomes vascularised.

Corneal inflammation and ulceration caused by a pathogen (bacteria, fungi, viruses, or parasites); associated with epithelial defect, stromal infiltration, and potential sight-threatening complications.

Inflammation of the corneal stroma without primary epithelial ulceration; caused by immune-mediated reactions to infections (syphilis, TB, herpes) or autoimmune disease (Cogan's syndrome).

A foreign body that has penetrated through the full thickness of the cornea (or sclera) into the intraocular space; a surgical emergency — slit-lamp removal is absolutely contraindicated.

The ocular manifestation of aqueous-deficient dry eye — dry eyes with corneal and conjunctival epithelial damage; the hallmark ocular feature of Sjögren's syndrome.

Non-inflammatory bilateral progressive thinning and conical ectasia of the corneal stroma, presenting at puberty with irregular astigmatism; characterised by Fleischer's ring, Vogt's striae, and Munson's sign.

The resident fibroblast of the corneal stroma; becomes an activated myofibroblast following injury, synthesising collagen in a disorganised arrangement that forms scar tissue.

Global spherical corneal ectasia with peripheral thinning; associated with Ehlers-Danlos and Marfan syndrome; distinct from keratoconus which is paracentral.

Corneal softening and necrosis from severe vitamin A deficiency; a medical emergency that can cause bilateral corneal perforation and blindness within 24–48 hours; treated with high-dose vitamin A.

Surgical replacement of diseased corneal tissue with healthy donor tissue; classified as lamellar (partial-thickness: DALK, DSEK, DMEK) or penetrating (full-thickness: PK).

The pathognomonic sign of endothelial graft rejection: a line of endothelial keratic precipitates advancing from the periphery to the centre of the donor cornea, with stromal oedema developing behind it; a medical emergency.

Multiple fine subepithelial infiltrates across the graft in subepithelial rejection; respond to topical steroids.

A dense white corneal opacity through which the iris is not visible; typically involves mid-to-deep stroma; causes severe VA reduction if central on the visual axis.

Destruction of limbal stem cells (palisades of Vogt) by severe chemical burns, Steven-Johnson syndrome, or trachoma cicatrix; causes conjunctivalisation of the corneal surface; treated by limbal stem cell transplantation before keratoplasty.

Epithelial progenitor cells located in the palisades of Vogt at the corneoscleral limbus; responsible for continuous replenishment of the corneal epithelium.

A moderate-density corneal opacity visible in direct illumination; iris is visible through it but iris details are indistinct; causes moderate VA reduction if central.

Theory explaining corneal transparency: regular spacing of collagen fibrils (< half the wavelength of visible light) causes destructive interference of scattered light, allowing transmission without scatter.

Traditional corneal preservation medium stored at 4°C providing 48–96 hours of viability; contains M199 culture medium + dextran + chondroitin sulphate + antibiotics.

Bilateral clear cornea with diameter >13 mm, usually X-linked recessive, with normal IOP; must be distinguished from buphthalmos.

Obstruction or dysfunction of the meibomian (tarsal) glands, reducing the lipid layer of the tear film and causing evaporative dry eye; the commonest cause of DED overall.

Congenital corneal horizontal diameter less than 10 mm; may be associated with microphthalmos, cataract, and predisposition to glaucoma.

Technique for interim preservation of a deceased donor's corneas: closed eyelids with moist sterile gauze pads, optionally combined with body refrigeration, to maintain corneal viability until eye bank retrieval.

V-shaped protrusion of the lower eyelid in downgaze, seen in advanced keratoconus, reflecting the conical corneal shape.

A topical polyene antifungal (5% eye drops) that is first-line treatment for filamentous fungal keratitis (Aspergillus, Fusarium); targets ergosterol in the fungal cell membrane.

An annual 2-week awareness campaign (August 25 – September 8) promoting voluntary eye donation in India.

The least dense grade of corneal opacity; visible only in oblique illumination; iris details clearly visible through it; rarely causes significant VA reduction unless central in a child.

Corneal epithelial breakdown secondary to trigeminal denervation; characterised by oval persistent epithelial defects, reduced or absent corneal sensation, and no inflammatory reaction.

National Programme for Control of Blindness and Visual Impairment — India's centrally-sponsored national programme targeting cataract, corneal, glaucoma, childhood blindness, and diabetic retinopathy.

Extended cold-storage preservation medium stored at 4°C, maintaining corneal viability for up to 14 days; current standard in most Indian eye banks.

Corneal preservation at 31–37°C in culture medium for up to 4 weeks; European standard; allows direct endothelial monitoring; requires more infrastructure than cold storage.

Measurement of corneal thickness; normal central thickness ~520–540 µm; values above 600 µm suggest oedema.

Excessive watering in a patient with dry eye disease, caused by lacrimal reflex stimulation from ocular surface irritation due to inadequate tear film lubrication.

Full-thickness corneal transplantation replacing all five layers; required when Descemet's membrane and endothelium are involved; carries lifelong endothelial rejection risk needing topical steroids.

Congenital central corneal opacity due to absent posterior corneal layers (Descemet's membrane and endothelium centrally) with iridocorneal adhesions; requires urgent glaucoma monitoring and keratoplasty.

Excimer laser ablation of the anterior corneal surface to treat opacities in the epithelium, Bowman's layer, or anterior stroma (up to ~150 µm depth); used for superficial nebulae, recurrent erosion syndromes, and anterior stromal dystrophies.

A bedside test using a card with small holes to reduce the effect of refractive error on VA; a pinhole that markedly improves VA suggests refractive error is the cause; it does NOT improve VA reduced by corneal opacity or macular disease.

A broad-spectrum cysticidal and trophozoitocidal antiseptic agent used as 0.02% eye drops in Acanthamoeba keratitis, combined with chlorhexidine.

Assessment of whether a patient can accurately localise a light source direction in all four quadrants; tests gross macular and visual pathway function in eyes with opaque media before surgical planning.

Topical anaesthetic eye drop (0.5%) used to anaesthetise the cornea and conjunctiva for procedures; for procedural use only — must not be prescribed for home use due to epitheliotoxicity.

Insertion of silicone plugs into the lacrimal puncta to reduce tear drainage and conserve tear volume; used in aqueous-deficient DED when lubricants are inadequate.

Pathognomonic sign of Acanthamoeba keratitis: white radial infiltrates along the course of corneal stromal nerves, caused by amoebic invasion of neural sheaths.

A circular stromal infiltrate surrounding the central cornea in Acanthamoeba keratitis, representing the immune inflammatory reaction encircling the infection focus.

A vital dye that stains devitalised and virally-infected epithelial cells; used in HSV keratitis to highlight the margin of the dendritic ulcer where active viral replication occurs.

Warning symptoms of graft rejection taught to every keratoplasty patient: Redness, Sensitivity (photophobia), Vision decrease, Pain — any of which requires immediate review.

A ring of iron oxide (rust) deposited in the corneal stroma around an embedded iron or steel foreign body; forms within hours; best removed 24-48 hours after FB extraction when it has softened.

WHO strategy for trachoma elimination: Surgery (trichiasis correction), Antibiotics (azithromycin MDA), Facial cleanliness, Environmental improvement.

Diffuse deep stromal reddish-pink vascularisation in syphilitic interstitial keratitis during the active phase; leaves ghost vessels after resolution.

Small round corneal infiltrates peripheral to the main fungal ulcer, following the direction of hyphal spread; a key distinguishing feature of filamentous fungal keratitis.

Quantitative tear production test using filter paper strips placed in the lower fornix; Schirmer I (without anaesthesia) measures basal + reflex secretion; ≥10 mm at 5 min = normal; <5 mm = severe deficiency.

Congenital peripheral (or complete) corneal opacification with vascularisation and ill-defined limbus, due to failure of mesenchymal differentiation.

Diagnostic test for corneal perforation: fluorescein applied to the suspected area and examined under cobalt blue light; a brighter green rivulet streaming from the FB site indicates aqueous leaking through a full-thickness corneal wound.

Autoimmune exocrinopathy causing lymphocytic destruction of lacrimal and salivary glands; primary Sjögren's = KCS + xerostomia + anti-Ro/SSA ± anti-La/SSB antibodies; secondary = in context of RA, SLE, or scleroderma.

Non-contact imaging technique that images individual endothelial cells using specular reflection to measure cell density, pleomorphism, and polymegethism.

The technique of approaching the corneal surface at a shallow angle (15-30 degrees, nearly parallel to the surface) with the needle bevel-up during FB removal, minimising the risk of inadvertent deep penetration or perforation.

Time in seconds from last blink to first dark spot in the fluorescein-stained tear film; ≥10 sec = normal; <10 sec = unstable tear film, typical of evaporative DED.

Transplantation of Human Organs Act 1994 (amended 2011) — the Indian legislation governing organ and tissue transplantation including eye donation; requires family consent from next-of-kin.

A chronic follicular conjunctivitis caused by Chlamydia trachomatis serotypes A, B, C; leading infectious cause of preventable blindness globally; causes cicatricial entropion, trichiasis, and corneal opacity.

A circular cutting instrument used to excise the recipient corneal button and prepare the donor button during keratoplasty; size 7.5–8.5 mm for routine PK.

Misdirection of eyelashes toward the cornea, typically from cicatricial entropion in trachoma; causes repeated corneal abrasion; WHO trachoma stage TT; treated surgically by bilamellar tarsal rotation.

WHO-IAPB global initiative 'The Right to Sight' aiming to eliminate avoidable blindness through combined prevention and treatment strategies.

Fine vertical or oblique stress lines in the deep stroma of keratoconus, disappearing on gentle pressure to the eye.

The spectrum of ocular manifestations of vitamin A deficiency, ranging from night blindness (XN) to keratomalacia (X3A/X3B) and corneal scarring (XS).