OA Admission Exam key terms

A reduced pupillary constriction when light is swung from the healthy eye to the affected eye, indicating asymmetric optic nerve or extensive retinal dysfunction. Detected with the swinging flashlight test and graded by the strength of the escape response.

A technique in which light is alternated between the two eyes to compare the direct pupillary response. A pupil that dilates rather than holds constriction when illuminated reveals an afferent conduction defect.

Damage to the optic nerve from ischemia, inflammation, compression, or toxicity, producing reduced acuity, color desaturation, visual field loss, and an afferent pupillary defect. Anterior ischemic disease often shows a swollen disc.

Loss of the same half of the visual field in both eyes, caused by a post-chiasmal lesion on the side opposite the field loss. Macular sparing may occur with occipital lesions.

Loss of the temporal fields of both eyes, typically from a chiasmal lesion compressing crossing nasal fibers. Commonly caused by pituitary adenoma and often accompanied by reduced color vision and acuity.

A reproducible area of reduced or absent sensitivity within the field of vision, mapped by perimetry. Pattern and location help localize damage along the visual pathway from retina to occipital cortex.

A standardized scheme (commonly 0 to 4+) that quantifies inflammatory cells and protein flare in the anterior chamber by slit-lamp beam. It guides diagnosis of uveitis and monitoring of treatment response.

Inflammation of the iris and ciliary body producing pain, photophobia, redness, cells and flare, and sometimes keratic precipitates. Often associated with HLA-B27 disease, trauma, or autoimmune conditions.

A layer of white blood cells settled in the inferior anterior chamber, visible as a fluid level. It signals severe intraocular inflammation or infection and requires urgent evaluation.

Severe intraocular infection, most often after surgery or penetrating trauma, causing pain, marked vision loss, hypopyon, and vitritis. It is an emergency requiring intravitreal antibiotics and urgent referral.

Examination using a stereoscopic microscope with an adjustable slit of light to view anterior segment structures in optical section and, with lenses, the fundus. It is fundamental for grading inflammation and detecting subtle lesions.

A method of estimating intraocular pressure by measuring the force needed to flatten a fixed area of cornea. Accuracy depends on corneal thickness and curvature, and the technique requires topical anesthetic and fluorescein.

The measured thickness of the cornea at its center, which influences applanation pressure readings. Thicker corneas tend to overestimate true pressure and thinner corneas to underestimate it.

The fluid pressure within the eye, determined by aqueous production and outflow. Elevated pressure is a major modifiable risk factor for glaucomatous optic nerve damage.

The difference between arterial blood pressure and intraocular pressure that drives blood flow to the optic nerve and retina. Low perfusion pressure may contribute to glaucomatous damage independent of eye pressure.

A topical glaucoma medication, such as latanoprost, that increases uveoscleral aqueous outflow and is usually the most effective single agent. Common side effects include iris darkening, eyelash growth, and periorbital pigmentation.

The route by which fluid leaves the anterior chamber, mainly through the trabecular meshwork and Schlemm canal, with a smaller uveoscleral component. Drugs and surgery target these pathways to lower eye pressure.

A drug that stimulates alpha or beta adrenergic receptors, reducing aqueous production and, for some agents, increasing outflow. Brimonidine and apraclonidine are common examples with allergic and sedating side effects.

Retinoscopy or subjective refraction performed after paralyzing accommodation with a cycloplegic drug. It reveals the full hyperopic error and is standard in young children and suspected accommodative disorders.

Paralysis of the ciliary muscle, eliminating accommodation, produced by anticholinergic drops such as cyclopentolate or atropine. It also dilates the pupil and is used for refraction and anterior segment treatment.

Dilation of the pupil, achieved pharmacologically with anticholinergic or sympathomimetic agents or occurring pathologically. It facilitates fundus viewing but can precipitate angle-closure in predisposed eyes.

A single value representing a spherocylindrical prescription, calculated as sphere plus half the cylinder. It is used for contact lens ordering and for comparing refractive states.

The separation between the back surface of a spectacle lens and the front of the cornea. It matters when converting high-power prescriptions between spectacles and contact lenses.

A clinically significant difference in refractive error between the two eyes. It can cause aniseikonia, poor binocularity, and amblyopia in children, and complicates contact lens fitting.

A perceived difference in image size between the two eyes, often arising from anisometropia or unequal magnification by correction. Symptoms include headache, asthenopia, and disturbed depth perception.

Reduced best-corrected acuity in one or both eyes without structural cause, resulting from abnormal visual experience during development. Causes include strabismus, anisometropia, and deprivation.

Misalignment of the eyes in which the visual axes do not intersect at the fixation target. It may be constant or intermittent, comitant or incomitant, and can lead to amblyopia and loss of binocularity.

A binocular alignment test in which one eye is occluded while the other fixates, revealing manifest deviation, and then the occluder is moved to expose a latent deviation. It is the core method for detecting tropia and phoria.

A progressive noninflammatory corneal thinning disorder producing conical steepening, irregular astigmatism, and reduced acuity. Management ranges from spectacles to rigid lenses and corneal cross-linking.

A contact lens made of oxygen-permeable rigid material that maintains its shape and masks irregular corneal astigmatism. It provides crisp vision in keratoconus but demands careful fitting and adaptation.

A measure (Dk/t) of how much oxygen passes through a contact lens of given thickness. Higher values reduce hypoxia-related complications such as neovascularization and edema.

Fluid accumulation within the cornea causing haze, halos, and reduced acuity. It can result from contact lens hypoxia, endothelial failure, or elevated eye pressure.

An allergic inflammatory response of the upper tarsal conjunctiva to contact lens deposits or mechanical irritation, producing itching, mucus, and large papillae. Management includes lens replacement or refitting.

Occlusion of the anterior chamber angle by iris, blocking aqueous outflow and causing a rapid rise in eye pressure. Acute attacks present with pain, halos, nausea, and a mid-dilated fixed pupil.

Blockage of the main retinal artery causing sudden painless monocular vision loss with a pale retina and cherry-red macula. It is an emergency linked to embolic and cardiovascular disease.

A large-vessel vasculitis of older adults causing headache, jaw claudication, and risk of irreversible vision loss from ischemic optic neuropathy. Urgent steroids and biopsy are required.

Microvascular retinal damage from chronic hyperglycemia, ranging from nonproliferative changes to proliferative disease with neovascularization. It is a leading cause of preventable vision loss in working-age adults.

Retinal vascular changes from elevated blood pressure, including arteriolar narrowing, AV nicking, hemorrhages, and exudates. Severe grades may include disc edema and signal systemic urgency.

The process of disclosing risks, benefits, and alternatives so a patient can voluntarily agree to care. It must be documented and is essential before procedures and off-label treatments.

The legally defined set of activities a clinician is permitted to perform under their license. It varies by jurisdiction and governs prescribing, procedures, and referral obligations.