Free COT Exam Flashcards

The structure behind the iris that produces aqueous humor and contains the ciliary muscle controlling accommodation. Its dual role is why cycloplegic drops (which paralyze the ciliary muscle) both dilate the pupil and block near focusing.

A single layer of cells lining the posterior cornea that actively pumps fluid out of the stroma to maintain corneal clarity. Unlike epithelium, endothelial cells do not regenerate in humans, so cell loss from surgery or disease is permanent.

Lipid (meibomian glands) over aqueous (lacrimal gland) over mucin (goblet cells). The lipid layer prevents evaporation, aqueous provides nutrition and oxygen, and mucin allows the film to adhere to the corneal epithelium. Layer disruption causes different dry-eye subtypes.

The macula is the central retina responsible for sharp, color vision; the fovea is the small central depression within it containing the highest cone density. Macular disease spares peripheral vision but destroys central acuity, which is why AMD patients keep side vision but lose reading ability.

The main aqueous outflow pathway at the angle between iris and cornea. Aqueous passes through the meshwork into Schlemm's canal, then into episcleral veins. Resistance here is the primary driver of elevated IOP in open-angle glaucoma, which is why most glaucoma medications target this pathway or aqueous production.

The numerator is the testing distance and the denominator is the distance at which a normal eye could read the same line. A patient reading 20/40 must stand at 20 feet to read what a normal eye reads at 40 feet, so a larger denominator always means worse acuity.

Alternative acuity charts for patients who cannot read letters (illiterate, non-English speaking, or young children). The patient indicates the direction the E points or where the gap in the C ring sits. They measure the same spatial resolution as Snellen letters without requiring letter recognition.

Preferential-looking cards used to test acuity in preverbal infants. The examiner watches whether the infant turns toward a grating of varying spatial frequency; since the baby cannot report, gaze direction becomes the response. The Snellen chart is useless here because the patient cannot name letters.

When recording acuity, a minus number after the line means letters missed on that line, while a plus means extra letters read on the next line. 20/20-2 means the patient read the 20/20 line but missed 2 of its letters; 20/25+2 means 20/25 fully read plus 2 letters on 20/20. This precision catches subtle acuity changes between visits.

A 10-degree central field screening tool for metamorphopsia (wavy lines) caused by macular disease. The patient views the grid at reading distance with one eye and reports distortion, missing areas, or wavy lines. It is a macula screen only and misses peripheral pathology.

An objective refraction method where the examiner neutralizes the pupillary light reflex with trial lenses, requiring no patient responses. This contrasts with subjective refraction (phoropter) where the patient compares lens choices. Retinoscopy is essential for children and non-communicative patients who cannot give reliable subjective answers.

A lens with equal and opposite cylinder powers used to refine astigmatic correction in two steps: first the axis (with the JCC straddling the corrected axis), then the power (with the JCC axis aligned). Flipping the lens lets the patient compare two orientations; sphere power is refined separately by duochrome or best sphere.

Uses chromatic aberration: red light focuses behind the retina and green in front. When letters on both backgrounds are equally clear, the refraction is balanced at the retina. If red is clearer the patient is under-minused; if green is clearer they are over-minused. It is a final sphere-balancing step, not a cylinder tool.

Always focus the most-plus (or least-minus) meridian first to record the sphere, then bring the orthogonal meridian into focus; the difference is the cylinder power. Starting with the minus meridian would mislabel the cylinder sign. Prism and optical center are checked separately after sphere and cylinder are recorded.

WTR means the steeper corneal meridian is near vertical (90 degrees) and is common in younger patients; ATR means the steeper meridian is near horizontal (180 degrees) and is more common in older adults. The minus-cylinder axis is roughly perpendicular to the steeper meridian, so WTR is corrected with axis near 180 and ATR with axis near 90.

The gold-standard IOP measurement based on the Imbert-Fick principle: the force needed to flatten a 3.06 mm area of cornea equals the pressure inside the eye. It requires topical anesthetic plus fluorescein and a slit-lamp mounted probe, giving more reliable readings than air-puff or Tono-Pen in most clinical settings.

The correct endpoint is when the inner edges of the two fluorescein semicircles just touch. Overlapping mires mean too much force was applied (overestimated IOP); widely separated mires mean too little. Thin mires indicate insufficient fluorescein and wide mires indicate excess dye, both of which corrupt the reading.

Applanation tonometry is biased by central corneal thickness (CCT). A thick cornea requires more force to applanate and reads artificially high; a thin cornea reads artificially low. Pachymetry is therefore essential to interpret IOP, especially in glaucoma suspects, and average CCT is roughly 540-560 micrometers.

Population normal is 10-21 mmHg, but this range does not rule glaucoma in or out. Normal-tension glaucoma damages the nerve at pressures within the normal range, and ocular hypertension patients may tolerate pressures above 21 mmHg without damage. IOP is a modifiable risk factor, not the disease definition itself.

A bowl perimeter that presents fixed-location stimuli of varying intensity while the patient presses a button. Unlike Goldmann kinetic perimetry (which moves a target inward), static perimetry maps threshold sensitivity at each point. The Humphrey 24-2 is the standard glaucoma pattern, testing 54 points within the central 24 degrees plus 2 nasal points to 30 degrees.

False positives occur when the patient presses the button despite no stimulus being presented (trigger-happy). High false positives inflate sensitivity and make the field look better than it is. Fixation losses indicate the eye drifted off target; false negatives indicate inattention or fatigue. All three must be within acceptable limits before the field is clinically useful.

The classic glaucomatous field defect, arching from the blind spot around fixation following the retinal nerve fiber bundle pattern. It differs from neurologic defects: homonymous hemianopia reflects post-chiasmal lesions and bitemporal hemianopia reflects chiasmal compression, neither of which follow the arcuate nerve fiber pattern.

The 24-2 covers the central 24 degrees (plus 2 nasal points) at lower density and is the default for glaucoma. The 10-2 tests the central 10 degrees at much higher density and is reserved for advanced glaucoma or macular disease, where fine central detail matters. Choosing the wrong pattern can miss or obscure the disease being tracked.

Uses low-coherence interferometry with light (not sound) to produce high-resolution cross sections of retinal layers. It is the primary tool for macular edema, AMD, macular holes, and glaucoma RNFL analysis. B-scan ultrasonography serves a different role: it works when media opacities (dense cataract, vitreous hemorrhage) block light from reaching the retina.

Measures retinal nerve fiber layer thickness around the optic disc, comparing the patient to a normative database. RNFL thinning is a structural marker of glaucomatous damage that often appears before visual field loss on perimetry, so serial OCT RNFL is used to detect early glaucoma and monitor progression between visits.

A two-dimensional ultrasound through closed eyelid or anesthetized globe. Its key advantage over OCT is penetration of dense media: when cataract or vitreous hemorrhage blocks light-based imaging, B-scan still images the retina and orbit, detecting retinal detachment, tumors, or posterior vitreous detachment.

The optic disc appears as a bright, well-defined circular structure where nerve fibers exit the eye, with a central cup whose size relative to the disc gives the cup-to-disc ratio. The macula sits temporal to the disc and appears darker. Asymmetry in cup-to-disc ratio above 0.2 between eyes or a ratio of 0.7 or larger raises glaucoma suspicion.

A short-acting mydriatic with mild cycloplegic effect, used for routine dilation. It works by parasympathetic blockade (not sympathetic stimulation), so it differs from phenylephrine, which is a sympathomimetic and produces mydriasis without cycloplegia. Tropicamide typically wears off within 4-6 hours.

A potent cycloplegic used for pediatric refractions. Children accommodate strongly and can mask hyperopia, so paralyzing the ciliary muscle reveals the true refractive error. Phenylephrine is not a substitute here: it dilates the pupil but provides no cycloplegia, so it cannot unlock hidden hyperopia in children.

An alpha-adrenergic agonist (sympathomimetic) that stimulates the iris dilator muscle to produce mydriasis without cycloplegia. This contrasts with tropicamide and cyclopentolate, which block the parasympathetic pathway. Phenylephrine is often paired with tropicamide for combined maximal dilation, since each acts on a different pathway.

A topical beta-blocker that lowers IOP by reducing aqueous humor production at the ciliary body. It is a workhorse first-line glaucoma drop but carries systemic risk: bradycardia and bronchospasm, so asthma and certain cardiac conditions are contraindications. Prostaglandin analogs like latanoprost work by the opposite mechanism (increasing outflow).

A prostaglandin analog that lowers IOP by increasing uveoscleral (non-conventional) outflow rather than suppressing aqueous production. Dosed once daily at bedtime, it can lower IOP 25-35%. Cosmetic side effects are distinctive: iris darkening, eyelash growth, and periorbital fat atrophy, which are not seen with beta-blockers.

Both are topical anesthetics, but proparacaine 0.5% is preferred for routine applanation tonometry because it stings less and acts within 20 seconds. Tetracaine is an alternative but causes more patient discomfort, which can introduce tearing and affect the reading. Either is paired with fluorescein for Goldmann tonometry.

A progressive ectatic disorder in which the cornea thins and bulges into a cone, producing irregular astigmatism that spectacle correction cannot fully fix. It typically begins in adolescence and is diagnosed with corneal topography. Distorted keratometry mires are a clinical clue, since regular astigmatism produces clear mires of differing sizes, not distorted ones.

Defined by neovascularization: abnormal new vessels growing on the retina or optic disc in response to ischemia. These vessels are fragile and bleed, causing vitreous hemorrhage and tractional retinal detachment. Hard exudates, cotton-wool spots, and microaneurysms alone are non-proliferative findings and do not define the proliferative stage.

The most common age-related cataract, involving yellowing and hardening of the lens nucleus. It can cause a myopic shift ('second sight') before acuity drops significantly. Posterior subcapsular cataracts are less common but progress faster and cause more glare, especially under bright lights or at night.

Separation of the vitreous from the retina, presenting with new flashes (photopsia) and floaters. PVD itself is benign in most cases, but it can create a retinal tear that progresses to detachment, so new symptoms warrant urgent dilated examination. This is not the same as a retinal detachment, where the retina itself separates from the underlying tissue.

A 'secondary cataract' where residual lens epithelial cells proliferate on the posterior capsule after cataract surgery. It can affect 20-50% of patients within 2-5 years and causes slowly blurring vision. Treatment is a quick Nd:YAG laser capsulotomy, which opens the opacified capsule without re-entering the eye.

Cataract removal using ultrasonic vibrations at a titanium or steel tip to emulsify the lens, with simultaneous aspiration of fragments through the same handpiece. This allows a 2.2-2.8 mm sutureless incision, much smaller than the 10-12 mm required for older extracapsular extraction, and reduces surgically induced astigmatism.

A viscoelastic (e.g., sodium hyaluronate) injected into the anterior chamber to maintain space and protect the corneal endothelium from ultrasonic energy and instruments during phacoemulsification and IOL insertion. It is removed at the end of surgery; leaving it would cause a postoperative IOP spike.

A non-contact device using partial coherence interferometry to measure axial length, keratometry, anterior chamber depth, and white-to-white. It is more precise than ultrasound A-scan for most eyes, but cannot image through a dense cataract, in which case A-scan ultrasound is required instead.

A commonly used IOL power formula combining axial length and keratometry inputs. Newer formulas like Barrett Universal II and Hill-RBF may outperform SRK/T in unusual eyes (very long, very short, post-refractive). Axial length errors of even 0.1 mm can shift the IOL power by roughly 0.25-0.3 D, which is why biometry precision is critical.

Through the pars plana, 3.5 mm posterior to the limbus in pseudophakic eyes and 4.0 mm in phakic eyes. This avoids the lens and retina. The technician supports by prepping the eye (povidone-iodine), positioning the patient, and maintaining the sterile field; the injector does not perform the actual injection.

Mnemonic for extraocular muscle innervation: Superior Oblique by CN IV (trochlear), Lateral Rectus by CN VI (abducens), and all the rest (Superior Rectus, Inferior Rectus, Medial Rectus, Inferior Oblique) by CN III (oculomotor). CN III palsy therefore causes a down-and-out eye with ptosis, while CN VI palsy causes inward deviation (esotropia).

Cover-uncover isolates the manifest deviation (tropia): covering the fixating eye forces the deviated eye to move to take up fixation. Alternate cover (cross-cover) disrupts fusion by switching the cover back and forth and reveals the total deviation (tropia plus latent phoria). Alternate cover always measures equal to or greater than cover-uncover for the same patient.

Esotropia is inward (nasal) deviation of one eye and is the most common childhood strabismus. Exotropia is outward (temporal) deviation. Direction matters for cause and treatment: esotropia is often accommodative and may respond to hyperopia correction, while exotropia may be intermittent and worsen with fatigue or daydreaming.

The closest a target can approach the nose before one eye breaks fixation and turns out, reported in centimeters. A normal NPC is within 6-10 cm. A receded NPC suggests convergence insufficiency, a common cause of eyestrain and diplopia with prolonged reading. It tests convergence ability, not accommodation amplitude.

Wait 3-5 minutes between different eye drops so the second does not wash out the first. The conjunctival sac holds only about 10 microliters while a single drop is 25-50 microliters, so immediate sequential instillation wastes medication. Ointments and gel drops go last because their film blocks absorption of any aqueous drop that follows.

Between patients, wipe or soak the applanation tip with 70% isopropyl alcohol or dilute sodium hypochlorite, rinse with sterile water, and air dry. This prevents transmission of adenovirus and other pathogens. Autoclaving is impractical between patients and tap-water rinsing alone is insufficient disinfection.

The unit of prism power in ophthalmology, abbreviated with a triangle. One prism diopter displaces a light ray 1 cm at a distance of 1 m. It differs from a lens diopter, which measures focal power. Prisms are prescribed to compensate for phorias or tropias by shifting the image to align with the deviated eye.