Iran Ophthalmology Specialty Board key terms

A single number representing a lens power, calculated by adding half of the cylindrical power to the spherical power. It approximates the eye's overall defocus and is used to compare refractive errors and monitor change over time.

A refractive condition in which the eye's optical power differs across meridians, so light from a point source forms a line or ellipse rather than a point on the retina, causing blurred vision at all distances.

Measurement of the curvature of the anterior corneal surface, usually expressed as radii of curvature and dioptric power in two principal meridians, used to detect astigmatism and fit contact lenses.

A computerized technique that maps the curvature and elevation of the corneal surface across many points, producing color-coded maps used to diagnose ectasia, plan refractive surgery, and fit contact lenses.

A progressive non-inflammatory corneal ectasia in which the cornea thins and steepens, producing irregular astigmatism, reduced best-corrected acuity, and characteristic topographic abnormalities; cross-linking may slow progression.

Acute corneal stromal edema caused by a break in Descemet membrane, allowing aqueous to enter the stroma. It presents with sudden visual loss and corneal opacity, most often in advanced keratoconus, and usually resolves with scarring.

A fibrovascular growth of conjunctiva that extends onto the cornea, typically from the nasal limbus in sun-exposed individuals. It can induce astigmatism, cause irritation, and recur after excision.

A benign yellow-white elevated nodule of degenerated conjunctival tissue near the limbus, usually on the nasal side, related to ultraviolet exposure. It does not cross onto the cornea and is mainly a cosmetic or irritative concern.

Microbial infection of the corneal stroma, often associated with contact lens wear or corneal trauma, presenting with pain, photophobia, stromal infiltrate, and possible hypopyon. It is a sight-threatening emergency requiring prompt topical antibiotics.

A defect of the corneal epithelium with underlying stromal inflammation or loss, caused by infection, trauma, or exposure. Fluorescein staining outlines the epithelial defect and helps guide urgent treatment.

Cataract surgery technique in which ultrasound energy delivered through a small incision breaks the lens nucleus into fragments that are aspirated, allowing implantation of a foldable intraocular lens with rapid visual recovery.

Opacification of the residual lens epithelial cells on the posterior capsule after cataract surgery, causing gradual visual decline months to years later. It is treated with neodymium:YAG laser capsulotomy.

Severe inflammation of intraocular tissues, usually caused by bacterial or fungal infection after surgery or trauma. It presents with pain, marked vision loss, and vitritis, and requires urgent intravitreal antibiotics and sometimes vitrectomy.

Accumulation of white blood cells in the anterior chamber that settles inferiorly and forms a visible layer. It signals severe intraocular inflammation such as infection, uveitis, or tumor and is an urgent clinical sign.

The fluid pressure within the eye, determined mainly by the balance between aqueous humor production by the ciliary body and outflow through the trabecular meshwork. Elevated pressure is a major modifiable risk factor for glaucoma.

A chronic progressive optic neuropathy with characteristic optic disc cupping and visual field loss, in which the anterior chamber angle is open. Raised intraocular pressure is common but not required for diagnosis.

Examination of the anterior chamber angle using a contact lens with mirrors or prisms that overcomes total internal reflection, allowing classification of the angle as open or closed and detection of abnormal vessels or pigment.

Glaucoma caused by obstruction of aqueous outflow when the iris blocks the trabecular meshwork, often with a shallow anterior chamber. Acute attacks cause severe pain, halos, a mid-dilated pupil, and require urgent pressure-lowering treatment.

Enlargement and deepening of the central depression of the optic nerve head with loss of neuroretinal rim tissue, a hallmark structural change of glaucoma that is assessed by stereoscopic disc examination and imaging.

A non-invasive imaging method using low-coherence light interference to produce cross-sectional images of ocular tissues, especially the retina and optic nerve, widely used to detect macular edema, measure retinal layers, and monitor glaucoma.

Microvascular damage of the retina caused by chronic hyperglycemia, ranging from non-proliferative changes such as microaneurysms and hemorrhages to proliferative disease with neovascularization and macular edema, a leading cause of blindness.

Bleeding into the vitreous cavity, commonly from proliferative diabetic retinopathy, retinal tear, or trauma, causing sudden floaters or vision loss. Ultrasound helps assess the retina when the view is obscured.

Separation of the neurosensory retina from the retinal pigment epithelium caused by a full-thickness retinal break through which liquefied vitreous enters the subretinal space. It requires urgent surgical repair to prevent permanent vision loss.

Inflammation of the uveal tract, including the iris, ciliary body, and choroid, classified by anatomic location as anterior, intermediate, posterior, or panuveitis. It may be infectious or immune-mediated and can cause synechiae and vision loss.

A human leukocyte antigen allele strongly associated with seronegative spondyloarthropathies and with acute anterior uveitis, which is typically unilateral, recurrent, and fibrinous in these patients.

A pupil test finding in which the pupil dilates when light is swung from the healthy eye to an eye with asymmetric optic nerve or extensive retinal disease, indicating reduced afferent conduction on the affected side.

Inflammation of the optic nerve, often demyelinating and associated with multiple sclerosis, causing subacute unilateral vision loss, pain on eye movement, color desaturation, and a relative afferent pupillary defect.

Bilateral optic disc swelling caused by raised intracranial pressure, typically preserving normal visual acuity early while enlarging the blind spot and risking subsequent optic atrophy if the pressure is not treated.

Infection of the lacrimal sac, usually resulting from nasolacrimal duct obstruction, presenting with pain, swelling, and redness over the medial canthus and possible purulent discharge from the punctum.

Excessive tearing that overflows onto the cheek, caused by overproduction of tears or, more often, by impaired drainage through the lacrimal system, eyelid malposition, or pump failure.

Drooping of the upper eyelid that may be congenital or acquired, due to weakness of the levator muscle, aponeurotic dehiscence, or sympathetic or oculomotor nerve disease, and can cause amblyopia in children.

Reduced best-corrected visual acuity in one or both eyes caused by abnormal visual experience during the critical period, such as strabismus, anisometropia, or deprivation, with no organic lesion explaining the deficit.

Misalignment of the eyes in which the visual axes do not point at the same object, classified as esotropia, exotropia, or hypertropia. It may cause diplopia in adults and amblyopia in children.

The most common intraocular malignancy of childhood, arising from retinal precursor cells and presenting with leukocoria or strabismus. It may be hereditary, bilateral, and associated with RB1 gene mutations.

A white pupillary reflex that is abnormal and requires urgent evaluation for retinoblastoma, congenital cataract, retinopathy of prematurity, or other causes of an absent red reflex in a child.

Clear fluid produced by the ciliary epithelium that fills the anterior and posterior chambers, nourishes avascular structures, and drains mainly through the trabecular meshwork into the venous system, determining intraocular pressure.

A spongy tissue at the anterior chamber angle through which aqueous humor passes on its way to Schlemm canal. Increased resistance to outflow here is a central mechanism in open-angle glaucoma.

Sensitivity is the proportion of people with disease who test positive; specificity is the proportion without disease who test negative. Both are intrinsic test properties used to judge screening and diagnostic tests.

The probability that a person with a positive test result truly has the disease. Unlike sensitivity, it depends on disease prevalence and falls when a test is applied in a low-prevalence population.