Kuwait Board Ophthalmology key terms

Distance from the anterior corneal surface to the fovea, measured by ultrasound or optical biometry; it is the strongest determinant of refractive error and is essential for intraocular lens power calculation.

Active developmental process in infancy and childhood in which eye growth is matched to the optical power of the cornea and lens so that images focus near the retina, normally reducing hyperopia toward emmetropia.

A difference in refractive error between the two eyes, commonly defined as more than 1 dioptre of spherical or cylindrical difference; a major cause of amblyopia because unequal retinal images prevent normal binocular development.

Reduced best-corrected visual acuity in one or both eyes caused by abnormal visual experience during the critical period, without organic disease; treated by correcting refractive error, occlusion, or penalisation.

Developmental window, roughly the first 7 to 10 years of life, during which the visual cortex remains plastic; deprivation within it causes amblyopia, and treatment becomes progressively less effective afterwards.

The most severe form of amblyopia, caused by form deprivation such as congenital cataract, ptosis, or corneal opacity during early infancy; it requires urgent removal of the obstacle to prevent permanent visual loss.

Progressive non-inflammatory ectasia in which the cornea thins and steepens, producing irregular astigmatism and reduced vision; managed with rigid contact lenses, corneal collagen cross-linking, or keratoplasty.

Treatment that saturates the cornea with riboflavin and exposes it to ultraviolet-A light, creating new collagen cross-links that stiffen the stroma and slow or halt keratoconus progression.

Measurement of central corneal thickness, used to assess ectasia risk before refractive surgery and to interpret Goldmann applanation tonometry, since thicker corneas read falsely high and thinner corneas falsely low.

Active bicarbonate and fluid transport by the corneal endothelium that counteracts stromal swelling; loss of endothelial cells causes corneal oedema, haze, and bullous keratopathy.

Persistent corneal oedema with epithelial blisters after cataract surgery, resulting from endothelial cell loss; treated with hypertonic agents, bandage contact lens, or endothelial keratoplasty.

Selective corneal transplant in which donor Descemet membrane and endothelium alone are implanted, giving faster visual recovery and lower rejection risk than full-thickness penetrating keratoplasty.

Use of biometry (axial length, keratometry, anterior chamber depth) with formulas such as SRK/T or Barrett to select an intraocular lens that achieves the intended postoperative refraction.

Measurement of ocular dimensions, including axial length, corneal curvature, and anterior chamber depth, by optical or ultrasound methods; accuracy is the main determinant of refractive outcome after cataract surgery.

Small-incision cataract surgery in which ultrasound energy emulsifies the lens nucleus within the capsular bag and the material is aspirated, leaving the posterior capsule intact for lens implantation.

Late complication of cataract surgery in which residual lens epithelial cells proliferate and migrate across the posterior capsule, causing glare and reduced acuity; treated with Nd:YAG laser capsulotomy.

Severe intraocular infection, most often after surgery or penetrating trauma, presenting with pain, hypopyon, and vitritis; treated urgently with intravitreal antibiotics and vitreous sampling.

Layer of white blood cells settling in the anterior chamber, indicating intraocular inflammation or infection; it requires urgent assessment to distinguish endophthalmitis from uveitis or tumour.

Reference method of measuring intraocular pressure by flattening a fixed corneal area, calibrated for average corneal thickness; readings are affected by corneal thickness, curvature, and astigmatism.

Chronic progressive optic neuropathy with open anterior chamber angles, characteristic disc cupping, and visual field loss, usually associated with raised intraocular pressure and treated by lowering it.

Enlargement of the central excavation of the optic nerve head with loss of neuroretinal rim, a structural hallmark of glaucoma assessed by stereoscopic examination and optical coherence tomography.

Ophthalmic emergency in which a closed drainage angle causes a rapid rise in intraocular pressure, with severe pain, haloes, mid-dilated pupil, and corneal oedema; requires urgent pressure-lowering and laser iridotomy.

Creation of a small hole in the peripheral iris to equalise pressure between the anterior and posterior chambers, relieving pupillary block; the definitive treatment for angle-closure disease.

Non-invasive imaging technique using low-coherence light to produce cross-sectional images of the retina, optic nerve, and anterior segment, quantifying oedema, fluid, and retinal nerve fibre layer thinning.

Fluid accumulation within the macula from leaking retinal capillaries in diabetes, the commonest cause of vision loss in diabetic retinopathy; treated with intravitreal anti-VEGF agents or focal laser.

Intravitreal injection of antibodies or fusion proteins that block vascular endothelial growth factor, reducing neovascularisation and vascular leakage in conditions such as diabetic retinopathy and age-related macular degeneration.

Advanced macular degeneration in which choroidal neovascular membranes grow beneath the retina, causing sudden distortion and haemorrhage; treated with repeated intravitreal anti-VEGF injections.

Separation of neurosensory retina from the pigment epithelium caused by a full-thickness retinal break allowing fluid to enter the subretinal space; presents with flashes, floaters, and a curtain-like field defect.

Microsurgical removal of vitreous through ports placed in the pars plana, used for retinal detachment, vitreous haemorrhage, macular hole, and epiretinal membrane, usually combined with gas or oil tamponade.

External silicone element sutured to the sclera to indent the eye wall, relieve vitreous traction, and close retinal breaks in rhegmatogenous detachment, often combined with cryotherapy and drainage.

Inflammation of the uveal tract classified as anterior, intermediate, posterior, or panuveitis; a systematic work-up is needed to identify infectious or systemic autoimmune causes before immunosuppression.

Adhesion of the iris to adjacent structures: posterior synechiae bind iris to lens and cause pupillary block, while anterior synechiae bind iris to cornea and close the angle.

Asymmetric pupillary constriction when light is swung from the healthy eye to the affected eye, indicating unilateral or asymmetric optic nerve or extensive retinal disease; detected by the swinging flashlight test.

Inflammation of the optic nerve, typically causing subacute unilateral visual loss, pain on eye movement, colour desaturation, and a relative afferent pupillary defect; often the first sign of demyelinating disease.

Bilateral optic disc swelling caused by raised intracranial pressure, usually preserving central acuity until late; it requires urgent neuroimaging and assessment for intracranial mass or venous sinus thrombosis.

White pupillary reflex in a child, a red flag for retinoblastoma, congenital cataract, retinopathy of prematurity, or Coats disease; any child with leukocoria needs urgent specialist assessment.

Most common primary intraocular malignancy of childhood, arising from retinal precursor cells; presents with leukocoria or strabismus and is managed by chemotherapy, focal therapy, or enucleation depending on stage.

Opacity of the lens present at birth or in early infancy that obstructs the visual axis and causes deprivation amblyopia; dense cases require surgery within the first weeks to months of life.

Surgical removal of the entire globe with preservation of orbital tissues, performed for intraocular malignancy, blind painful eye, or severe trauma, usually followed by orbital implant placement.

Removal of the intraocular contents while leaving the sclera and extraocular muscles intact, giving good motility but contraindicated when intraocular malignancy is suspected because tumour may spread.

Rapid rise in orbital pressure from haemorrhage, oedema, or emphysema that compromises optic nerve perfusion; presents with pain, proptosis, and falling acuity and requires urgent canthotomy and cantholysis.

Ocular emergency in which acid or, more severely, alkali penetrates the cornea and anterior segment; immediate copious irrigation and pH testing determine the outcome more than any later treatment.

Loss or dysfunction of stem cells at the corneoscleral limbus, causing conjunctivalisation, vascularisation, and persistent epithelial defects; managed by limbal stem cell transplantation in severe cases.

Filtration surgery creating a guarded fistula from the anterior chamber to the subconjunctival space, lowering intraocular pressure in glaucoma; failure results from scarring at the bleb or ostium.

Psychophysical measurement of the sensitivity of the visual field, commonly by automated static perimetry, used to detect and monitor glaucomatous loss and neurological defects such as hemianopia.

Mapping of corneal curvature and elevation across the surface, used to detect irregular astigmatism, keratoconus, and contact lens-related warpage, and to screen candidates before refractive surgery.

Laser procedure that creates an opening in an opacified posterior capsule after cataract surgery, restoring the visual axis; it carries a small risk of retinal detachment and lens dislocation.

Misalignment of the eyes in which the visual axes are not parallel, classified by direction as esotropia, exotropia, hypertropia, or hypotropia; assessment includes cover testing and refraction.