COA Certified Ophthalmic Assistant flashcards

31 cards. Read the term and the definition here. The deck at the top of this page is optional.

Snellen fraction meaning

The numerator is the testing distance, usually 20 feet, and the denominator is the distance at which a standard eye reads that same line. Thus 20/40 means the patient needs 20 feet to read letters standard vision reads at 40 feet.

Pinhole test interpretation

Looking through a pinhole reduces blur from defocus. If acuity improves, the loss is largely refractive; if acuity does not improve, media opacity, retinal, or optic nerve disease should be suspected and further evaluation arranged.

Goldmann applanation principle

The tonometer flattens a circular corneal area 3.06 mm in diameter. Because corneal surface tension and rigidity balance at that area, grams of force equal millimeters of mercury, so the dial reading approximates intraocular pressure.

Amsler grid purpose

A grid held at reading distance tests the central 10 degrees of field. The patient fixates the center dot and reports distortion, missing, or blurred areas, which can indicate macular disease such as edema or metamorphopsia.

Corneal refractive power

The cornea supplies roughly 60 diopters, about two-thirds of the eye's total refractive power, mostly from the anterior surface. The crystalline lens adds about 20 diopters and changes power during accommodation.

Aqueous humor outflow pathway

Aqueous humor is secreted by the ciliary epithelium into the posterior chamber, passes through the pupil into the anterior chamber, and drains through the trabecular meshwork into Schlemm canal and episcleral veins.

Rods versus cones

Rods support dim-light and peripheral vision, peak near 500 nm, and are absent from the fovea. Cones support daylight and color vision, concentrate in the fovea, and have three photopigment types.

Myopia and its correction

In myopia, light from a distant object focuses anterior to the retina, usually because the eye is too long. It is corrected with a minus, concave lens that diverges light before it enters the eye.

Cranial nerve muscle supply

Cranial nerve III supplies the superior, inferior, and medial recti plus the inferior oblique and levator. Cranial nerve IV supplies the superior oblique, and cranial nerve VI supplies the lateral rectus.

Relative afferent pupillary defect

In the swinging flashlight test, light moved from the normal eye to an eye with asymmetric optic nerve or retinal disease causes that pupil to dilate rather than constrict, indicating reduced afferent input from that eye.

Perimetry reliability indices

Automated perimetry reports fixation losses, false-positive, and false-negative rates. High rates mean the patient was not reliably fixating or responding, so results must be interpreted cautiously and testing may need repeating.

Optical coherence tomography use

OCT uses low-coherence light interference to create cross-sectional retinal images. It measures retinal nerve fiber layer and macular thickness, supporting glaucoma and macular disease diagnosis and monitoring over time.

Refraction notation order

Refraction is written sphere, then cylinder, then axis. The sphere gives spherical power, the cylinder the astigmatic power, and the axis the cylinder meridian in degrees between 1 and 180.

Fluorescein angiography precautions

Fluorescein dye is injected intravenously and excreted renally, temporarily discoloring urine. Consent and allergy screening are required, and extravasation at the injection site must be managed per office protocol.

Tropicamide versus cyclopentolate

Tropicamide is a short-acting mydriatic that wears off within hours. Cyclopentolate is a cycloplegic that also paralyzes accommodation and lasts longer, so near vision stays blurred longer after instillation.

Phenylephrine dilation effect

Phenylephrine dilates by constricting iris blood vessels without paralyzing the ciliary muscle, so accommodation is largely preserved. It can raise blood pressure, so use caution in hypertensive or cardiac patients.

Chemical burn first response

For a chemical splash, irrigate the eye copiously with saline or water immediately, before checking vision, and continue until pH normalizes. Then notify the physician urgently, since delay worsens ocular damage.

Open globe precautions

With a suspected open globe, do not apply pressure, do not measure intraocular pressure, and do not instill drops unless directed. Shield the eye, keep the patient calm, and notify the physician immediately.

Topical anesthetic misuse risk

Topical anesthetics are for office procedures only. Repeated or home use causes corneal epithelial toxicity, delayed healing, and potential perforation, so they are never dispensed for patient self-administration.

Tonometer tip disinfection

Tonometer tips and trial lenses must be cleaned and disinfected between every patient according to manufacturer instructions and office infection-control policy, reducing transmission of ocular surface pathogens.

Keratometry measurement zone

Keratometry measures corneal curvature over the central roughly 3 mm. It converts radius of curvature to diopters using the corneal refractive index of about 1.376, and average corneal power is about 43 to 44 diopters.

Schiøtz tonometry limitation

Schiøtz tonometry uses a weighted plunger and conversion table. Readings are less reliable with irregular astigmatism or after corneal surgery, and repeated measurements displace aqueous, so they must be done quickly.

Pachymetry and pressure reading

Central corneal thickness affects tonometry. Thick corneas tend to overestimate and thin corneas underestimate true intraocular pressure, so pachymetry helps interpret Goldmann readings accurately.

Tear film three layers

The outer lipid layer from meibomian glands slows evaporation. The middle aqueous layer comes from lacrimal glands. The inner mucin layer from goblet cells anchors tears to the corneal epithelium.

Optic nerve blind spot

The optic nerve head lacks photoreceptors, creating a physiologic scotoma. It lies about 15 degrees nasal to the fovea, so each eye has a blind spot in its temporal visual field.

Astigmatism correction lens

Astigmatism occurs when corneal or lenticular curvature differs between meridians, so light focuses at different planes. It is corrected with a cylindrical lens, whose axis aligns with the meridian needing no correction.

Ocular history sequence

A complete history records the chief complaint with onset and duration, ocular history, medical and surgical history, medications, allergies, family history, and social history including smoking and occupational exposure.

Ishihara plate purpose

Ishihara plates screen for red-green color vision deficiency. A patient who cannot identify any plate may have a severe acquired defect, which warrants further evaluation rather than a diagnosis of simple congenital color blindness.

Mydriasis patient warning

After dilating drops, warn patients of photophobia and blurred near vision lasting hours. Those with shallow anterior chambers need intraocular pressure assessment after dilation as directed by the physician.

Clinical record legal status

The chart is a legal document. Record what was done and observed, including eye, time, medication and strength, and patient statements. Never alter entries later except through a dated addendum.

Patient confidentiality rule

Patient information is protected by privacy law. Do not discuss patients in public areas, share images without consent, or access records without a care-related reason, since violations carry legal and professional consequences.