Arab Board Ophthalmology Clinical & Oral key terms

Progressive thinning and outward bulging of the cornea that distorts its shape and blurs vision, seen in keratoconus and after refractive surgery that removes too much tissue.

Measurement of corneal thickness, usually by ultrasound or optical scanning, used to screen for ectasia risk and to plan refractive surgery or assess oedema.

Measurement of the curvature of the anterior corneal surface, giving the radius of curvature in millimetres and the power in dioptres along two principal meridians.

Number of corneal endothelial cells per square millimetre measured by specular microscopy, used to judge the reserve for pump function before intraocular surgery.

Persistent corneal swelling with epithelial blisters after cataract surgery, caused by endothelial cell loss that leaves the cornea unable to pump out fluid.

Full-thickness replacement of the central cornea with donor tissue, used for scarring, ectasia or endothelial failure when the whole cornea is affected.

Immune attack on a corneal transplant, appearing as a rejection line on the endothelium, stromal infiltrates or graft swelling, and treated with intensive topical and sometimes systemic steroids.

Refractive error in which the eye has different focusing power along different meridians, so a point of light forms a line rather than a point on the retina.

An implant with cylinder power marked on its optic and alignment marks on its haptics, used at cataract surgery to neutralise pre-existing corneal astigmatism.

The predicted postoperative depth of the intraocular lens within the eye, which determines the final refractive power achieved and is the main source of biometry error.

Measurement of eye length, corneal curvature and sometimes lens thickness before cataract surgery, used to calculate the power of the intraocular lens to implant.

Clouding of the residual lens capsule behind an intraocular lens months to years after surgery, causing gradual visual loss that is treated with a laser capsulotomy.

Laser treatment that creates an opening in an opacified posterior lens capsule to restore the visual axis after cataract surgery.

Severe infection inside the eye, usually after surgery or trauma, presenting with pain, marked visual loss, hypopyon and vitritis, and requiring urgent intravitreal antibiotics.

A layer of white blood cells settling in the anterior chamber and forming a visible fluid level, indicating severe intraocular inflammation or infection.

Inflammation of the iris and ciliary body causing eye pain, redness, photophobia, cells and flare in the anterior chamber, and sometimes a small pupil from spasm.

An abnormal adhesion of the iris, either to the lens or capsule (posterior) or to the peripheral cornea (anterior), which can block aqueous flow and raise pressure.

Blockage of aqueous outflow because the peripheral iris obstructs the drainage angle, causing a sudden rise in eye pressure with pain, haloes and a cloudy cornea.

Examination of the anterior chamber drainage angle using a contact lens with mirrors or prisms that overcomes total internal reflection at the cornea.

Enlargement and deepening of the central depression of the optic nerve head with loss of the neuroretinal rim, the structural hallmark of glaucomatous damage.

A reproducible area of reduced sensitivity on perimetry, typically a nasal step, arcuate scotoma or paracentral loss in glaucoma, mapped to nerve fibre bundle damage.

Non-invasive imaging that uses light interference to produce cross-sectional pictures of the retina and optic nerve, quantifying nerve fibre and ganglion cell layers.

A thin sheet of fibrous tissue growing on the inner surface of the macula that wrinkles the retina and causes distortion and reduced central vision.

A full-thickness defect in the centre of the macula causing a central blind spot and distortion, often treated by vitrectomy with membrane peeling and gas tamponade.

Surgery that removes the vitreous gel through ports placed in the pars plana, used for haemorrhage, retinal detachment, membranes and infection.

Separation of the neurosensory retina from the pigment epithelium caused by a full-thickness retinal break through which fluid enters the subretinal space.

An external silicone element sutured to the sclera to indent the eye wall, relieve vitreous traction and close retinal breaks in detachment surgery.

A weaker direct pupil response when light is swung from the healthy eye to the affected one, indicating asymmetric damage to the retina or optic nerve.

Inflammation of the optic nerve causing painful loss of vision, reduced colour vision and a relative afferent pupillary defect, often the first sign of demyelinating disease.

Swelling of the optic disc caused by raised intracranial pressure, usually bilateral, with preserved central vision until late and enlarged blind spots.

Forward displacement of the eyeball out of the orbit, measured in millimetres, caused by mass effect, inflammation or vascular problems within the orbit.

A rapid rise in orbital pressure after bleeding or swelling that threatens the optic nerve and retinal blood supply, requiring urgent decompression such as lateral canthotomy and cantholysis.

A white pupillary reflex in a child, which is a red flag for retinoblastoma, congenital cataract, retinal detachment or other serious intraocular disease.

A malignant tumour arising from immature retinal cells in young children, presenting with a white pupil or squint and treated by chemotherapy, laser, cryotherapy or enucleation.

Surgical removal of the entire eyeball with part of the optic nerve, leaving orbital tissues intact, performed for intraocular tumour or a blind painful eye.

Reduced vision in one or both eyes caused by abnormal visual experience during childhood, such as strabismus, anisometropia or deprivation, correctable if treated early.

Misalignment of the eyes in which the visual axes do not point at the same object, classified by direction as esotropia, exotropia, hypertropia or hypotropia.

A significant difference in refractive power between the two eyes, which can cause unequal retinal images and amblyopia in a child.

Blunt trauma to the eye causing transient or permanent whitening of the retina from disruption of photoreceptor outer segments, sometimes with a cherry-red spot at the fovea.

A circumferential tear at the ora serrata, usually from blunt trauma, which allows fluid to enter the subretinal space and cause a retinal detachment.