OP8.1-6 | Lens, Cataract and Aphakia — Glossary

Reduced visual acuity in one or both eyes due to abnormal visual development during the critical period (birth to approximately 7–8 years); caused by visual deprivation (dense cataract, aphakia), strabismus, or anisometropia; treated by optical correction and patching of the fellow eye.

Unequal image sizes perceived by the two eyes; the maximum tolerable difference is approximately 5%; aphakic spectacle correction in unilateral aphakia causes ~25–30% magnification — far beyond the tolerable threshold, making binocular fusion impossible.

An intraocular lens placed in the anterior chamber angle when no posterior capsular support is available (e.g. after ICCE); associated with higher long-term risk of corneal endothelial damage compared to in-bag posterior chamber IOLs.

Absence of the crystalline lens from the eye; results in high hypermetropia (~+10D), loss of accommodation, and optical aberrations; corrected by IOL implantation, contact lens, or aphakic spectacles.

Cross-sectional acoustic imaging of the posterior segment; mandatory when fundus is not visible due to dense cataract or media opacity; detects retinal detachment, vitreous haemorrhage, and posterior segment tumours.

A newer, more accurate IOL power calculation formula for eyes with average or extreme axial lengths and those with prior refractive surgery; increasingly adopted as the preferred formula.

Pre-operative measurement of axial length and corneal curvature (keratometry) used to calculate the required IOL power; inaccurate biometry is the commonest cause of unexpected refractive error after cataract surgery.

Continuous curvilinear capsulotomy — a smooth, circular, continuous anterior capsular opening made during modern cataract surgery; provides a stronger, more controlled opening than the older can-opener technique.

The number of cataract operations performed per million population per year; India's current national target is 8,000 per million; used as a health systems indicator for programme performance.

Number of endothelial cells per mm² measured by specular microscopy; normal ~2000–3000 cells/mm²; risk of corneal decompensation after phacoemulsification increases significantly below ~1000–1500 cells/mm².

The period of visual cortex plasticity from birth to approximately 7–8 years during which visual experience shapes neural pathway development; visual deprivation during this window causes permanent amblyopia even if optical correction is provided later.

The principal structural proteins of the lens (α, β, γ); α-crystallin also functions as a molecular chaperone; their ordered packing maintains lens transparency.

Post-operative petaloid fluid accumulation in the macula due to prostaglandin-mediated inflammation or vitreous incarceration; treated with topical NSAIDs and steroids; intravitreal anti-VEGF in refractory cases.

Fluid accumulation in the macular retina due to diabetic vascular leakage; the leading cause of visual loss in diabetic retinopathy; may need intravitreal anti-VEGF treatment before or concurrent with cataract surgery.

Cataract extraction via a large (10–12 mm) limbal incision with expression of the nucleus; requires sutures; now largely replaced by phaco and MSICS.

Severe intraocular infection presenting 2–7 days after cataract surgery with pain, red eye, hypopyon, and reduced vision; caused most commonly by Staphylococcus epidermidis; treated urgently with intravitreal antibiotics ± vitrectomy (per EVS criteria).

Landmark RCT defining endophthalmitis management after cataract surgery: patients with hand motion or worse vision benefit from pars plana vitrectomy + intravitreal antibiotics; those with better vision do equally well with intravitreal antibiotics alone.

Catastrophic intraoperative haemorrhage in the suprachoroidal space causing sudden IOP rise and expulsion of intraocular contents through the wound; rare; risk factors include uncontrolled hypertension and anticoagulation.

Injection of balanced salt solution under the anterior capsular edge to separate the lens nucleus from the cortex and capsule, facilitating nuclear rotation and expression during cataract surgery.

Removal of the entire lens including the capsule; largely obsolete; used only in specific cases such as complete zonular dehiscence.

Randomised clinical trial comparing primary IOL implantation vs contact lens correction in infants with unilateral congenital cataract; found no significant difference in visual acuity at 4.5 years; both groups required aggressive patching therapy.

A process ensuring a patient with decision-making capacity voluntarily agrees to a procedure after receiving adequate information about its risks, benefits, alternatives, and consequences of refusal; documented in writing.

Surgical complication seen in patients taking alpha-1A adrenergic blockers (especially tamsulosin) in which the iris becomes floppy, billows during surgery, prolapse toward incisions, and resists dilation; managed with iris hooks or ring expanders.

Artificial lens implanted inside the eye during cataract surgery to replace the refracting power of the extracted natural lens.

Trembling of the iris when the patient moves their eye; pathognomonic of aphakia (loss of lens posterior support for the iris); distinguished from phacodonesis (lens trembling with weak zonules, lens still present).

Bedside test in which a pen torch is directed from the temporal side: presence of a crescentic iris shadow on the lens indicates an immature cataract; absence indicates a mature or hypermature cataract.

Visual phenomenon in aphakic spectacle wearers where objects in the ring scotoma suddenly 'jump' into the central field of view when the patient turns their head; caused by the prismatic effect of the thick convex aphakic lens.

The elastic basement membrane surrounding the lens; thickest anteriorly and thinnest posteriorly; preserved during extracapsular surgery to hold the IOL.

A single layer of cuboidal cells beneath the anterior capsule; the only mitotically active component of the adult lens; equatorial cells differentiate into new lens fibres.

Standard intraocular lens providing sharp focus at one distance (usually distance); reading glasses required for near work post-operatively; covered under government schemes.

An advanced hypermature cataract in which the lens cortex is fully liquefied and the denser nucleus sinks inferiorly; carries high risk of phacolytic glaucoma.

Cataract surgery via a 5–7 mm self-sealing scleral tunnel incision with manual nucleus expression; the preferred high-volume technique in India under NPCBVI.

Premium intraocular lens with multiple focal zones providing acceptable vision at distance and near without glasses; may cause glare and halos, especially at night.

Outpatient laser procedure used to create a central opening in the opacified posterior capsule in PCO; it is NOT a second cataract surgery.

India's national government programme targeting blindness prevention and visual rehabilitation; sets targets for cataract surgical rate (CSR) and post-operative visual outcome benchmarks.

Progressive hardening and yellowing/browning of the lens nucleus with age; the most common morphological pattern of senile cataract.

Non-contact instrument measuring axial length by partial coherence interferometry; combined with keratometry to calculate IOL power; current gold standard for pre-operative biometry.

Regional anaesthesia for cataract surgery by injecting local anaesthetic (lignocaine ± bupivacaine) into the peribulbar space (outside the muscle cone); provides akinesia and analgesia without the higher risks of retrobulbar injection.

Trembling of the crystalline lens due to weakened zonular fibres (seen in pseudoexfoliation syndrome, Marfan syndrome, trauma); the lens is still present — differs from iridodonesis.

Modern cataract surgery technique using a 2–3 mm incision and ultrasonic probe to emulsify the lens nucleus in situ, followed by aspiration and foldable IOL implantation; the current global standard.

Secondary open-angle glaucoma caused by leakage of liquefied lens proteins from a hypermature cataract, which obstruct the trabecular meshwork via macrophage-laden debris.

Acute angle-closure glaucoma precipitated by an intumescent (swollen) lens pushing the iris-lens diaphragm forward, shallowing the anterior chamber.

Sympathomimetic mydriatic eye drop (5% or 10% solution) that dilates the pupil by stimulating the dilator pupillae; used in combination with tropicamide for maximum dilation; avoid 10% in uncontrolled hypertension due to risk of systemic BP elevation.

The commonest late complication of cataract surgery; proliferation of residual equatorial lens epithelial cells across the posterior capsule causing visual blurring; treated by Nd:YAG laser capsulotomy.

Intraoperative complication where the thin posterior capsule (2–4 µm) tears; management depends on vitreous prolapse — if present, anterior vitrectomy is performed; IOL placed in sulcus rather than in the bag.

Opacity located at the posterior pole of the lens just anterior to the posterior capsule; causes disproportionate visual loss and glare; associated with steroids, diabetes, and uveitis.

Broad-spectrum antiseptic instilled as 5% solution into the conjunctival sac immediately pre-operatively; the evidence-based gold standard for reducing post-operative endophthalmitis after cataract surgery.

The state of having an intraocular lens (IOL) implanted within the eye after cataract extraction; provides optical correction close to emmetropia with minimal magnification (~1–2%).

Regional anaesthesia injected inside the extraocular muscle cone (retrobulbar space); provides excellent akinesia and analgesia but carries higher risks of globe perforation, optic nerve injury, and retrobulbar haemorrhage.

An absolute blind area (scotoma) in the peripheral visual field produced by the prismatic effect of a thick +10D aphakic spectacle lens; objects in this zone disappear and reappear as the patient turns their head — the 'jack-in-the-box' phenomenon.

The non-sterile team member in the operating theatre responsible for opening instrument packs, managing the phaco machine and irrigation, adjusting room conditions, and communication outside the sterile field.

A sterile team member gowned and gloved within the sterile field; responsible for passing instruments to the surgeon and maintaining instrument count; must not touch non-sterile surfaces.

Surgical implantation of an IOL in an eye that was left aphakic at the original cataract surgery; performed weeks to decades later; IOL type (in-bag, sulcus, AC-IOL) depends on available capsular support.

The aldose reductase pathway that converts glucose or galactose to corresponding sugar alcohols (sorbitol or galactitol) in the lens; osmotic accumulation causes the metabolic cataracts of diabetes and galactosaemia.

Non-contact clinical instrument that photographs and quantifies the corneal endothelial cell density (cells/mm²) and morphology; used pre-operatively to assess risk of corneal decompensation from phacoemulsification energy.

A regression-based formula (Sanders-Retzlaff-Kraff/Theoretical) for IOL power calculation; reliable for eyes with average axial length; less accurate for extreme axial lengths where Barrett Universal II is preferred.

Application of local anaesthetic eye drops (proxymetacaine 0.5%) to the conjunctiva and cornea; used for phacoemulsification in cooperative patients; patient remains alert and may observe light during surgery.

IOL designed to correct pre-existing corneal astigmatism; must be aligned precisely on the correct meridian; reduces post-operative astigmatic refractive error in selected patients.

Anticholinergic mydriatic eye drop (1% solution) that dilates the pupil by paralysing the sphincter pupillae; onset 20–30 minutes; duration 4–6 hours; used pre-operatively for cataract surgery.

WHO-IAPB global initiative (launched 1999) targeting the elimination of avoidable blindness by 2020; India is a signatory; cataract surgery is the primary intervention under this framework.

Prolapse of vitreous gel through a posterior capsular tear into the anterior chamber during cataract surgery; requires meticulous anterior vitrectomy to prevent vitreous incarceration in the wound.

Standardised pre-operative safety check with three time-out points (sign-in, time-out, sign-out); includes correct site/patient/procedure verification; adopted in all accredited Indian surgical facilities.

The suspensory ligament of the lens; fibrous zonular fibres run from the ciliary body to insert into the equatorial lens capsule, holding the lens in position and transmitting ciliary muscle tension for accommodation.