OPTE flashcards
OPTE · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Vergence formula
- L = n/l, where n is refractive index and l is distance in meters. Diverging light has negative vergence and converging light positive; this quantity drives thin-lens calculations.
- Thin lens equation
- U + F = V: object vergence plus lens power equals image vergence. Image distance is n'/V; a positive V forms a real image on the emergent side.
- Prism diopter definition
- One prism diopter displaces an object 1 cm at 1 m. Deviation δ in prism diopters equals 100 times tan of the deviation angle in degrees.
- Corneal endothelial pump
- The endothelium actively removes fluid from the stroma, maintaining corneal deturgescence. Human endothelial cells do not regenerate; loss causes edema and reduced clarity.
- Aqueous humor outflow pathways
- Aqueous leaves the anterior chamber mainly through the trabecular meshwork and Schlemm canal, with a smaller uveoscleral route. Outflow obstruction raises intraocular pressure.
- Foveal cone density
- The foveola contains the highest cone density, roughly 150,000–200,000 per square millimeter, with no rods and no overlying vessels, supporting maximum acuity.
- Spherical equivalent
- Sphere plus half the cylinder power. A prescription of −2.00/−1.00×180 has a spherical equivalent of −2.50 diopters, useful for estimating overall refractive error.
- Jackson cross-cylinder technique
- A cross-cylinder with axes at 45 degrees to the tested meridians refines astigmatism. Flip to compare clarity, adjust axis first, then cylinder power in 0.25 D steps.
- Duochrome test principle
- Red and green wavelengths focus at different positions due to chromatic aberration. With best sphere, both appear equally clear; red clearer means add minus, green clearer means add plus.
- Vertex distance compensation
- When the refracting and fitting vertex distances differ, adjust power with Fc = F/(1 − dF). Minus lenses gain plus power as they move closer to the eye.
- Prentice's rule
- Prism in diopters equals decentration in centimeters multiplied by lens power in diopters. A −4.00 D lens decentered 3 mm induces 1.2 prism diopters.
- Abbe value and chromatic aberration
- Abbe value measures dispersion; lower values produce more chromatic aberration. High-index materials reduce lens thickness but typically lower Abbe value.
- RGP fluorescein pattern
- Fluorescein evaluation shows apical clearance, mid-peripheral alignment, and edge lift. Excessive central pooling indicates a steep fit; touch indicates a flat fit.
- Dk/t oxygen requirement
- Dk/t expresses oxygen transmissibility. Daily wear needs about 24 and extended wear about 87 in standard units; silicone hydrogels exceed these values comfortably.
- Toric lens rotation rule
- Assess rotation with slit lamp and axis marks, then apply LARS: left add, right subtract. Rotate the prescribed axis in the direction of lens rotation.
- Cyclopentolate versus tropicamide
- Cyclopentolate 1% gives stronger cycloplegia lasting about 24 hours. Tropicamide 0.5–1% gives shorter mydriasis and weaker cycloplegia, useful for screening.
- Fluorescein staining
- Sodium fluorescein stains areas of corneal epithelial loss. Cobalt blue excitation makes defects visible; it also assesses tear breakup time and contact lens fit.
- Timolol mechanism
- Timolol, a topical beta-blocker, lowers intraocular pressure by reducing aqueous production. It is contraindicated in asthma, bradycardia, and heart block.
- Hirschberg test
- Corneal light reflex decentration estimates deviation: 1 mm equals roughly 7 degrees or 15 prism diopters. The reflex appears displaced opposite the direction of strabismus.
- AC/A ratio
- Accommodative convergence per diopter of accommodation, normally 4–6 prism diopters per diopter. High ratios suggest convergence excess; low ratios suggest divergence excess.
- Alternate cover test
- Alternating cover breaks fusion and reveals the total deviation, including latent phoria. The prism alternate cover test measures the magnitude until movement reverses.
- Glaucomatous disc signs
- Cupping greater than 0.6, rim thinning, disc hemorrhage, and nerve fiber layer loss suggest glaucoma. Correlate with intraocular pressure and visual field defects.
- Keratoconus signs
- Inferior corneal steepening, irregular astigmatism, Vogt striae, and Fleischer ring indicate keratoconus. Topography confirms and monitors progression for crosslinking decisions.
- Anterior uveitis findings
- Cells and flare in the anterior chamber, photophobia, ciliary flush, and miosis characterize anterior uveitis. Topical steroids and cycloplegics are standard treatment.
- Goldmann applanation principle
- A 3.06 mm diameter probe applanates the cornea; force converts directly to pressure. Central corneal thickness affects accuracy, with thinner corneas underestimating pressure.
- Pinhole test
- A pinhole reduces blur circles from refractive error, improving acuity in uncorrected ametropia. Failure to improve suggests media opacity or retinal or neural disease.
- Indirect ophthalmoscopy
- A condensing lens with a head-mounted or handheld scope provides a magnified, inverted, stereoscopic view of the peripheral retina, useful for detecting tears and detachments.
- Visual field reliability indices
- Fixation losses below 20 percent and false positive and negative rates below 33 percent indicate a reliable field. Unreliable fields should be repeated before interpretation.
- Informed consent elements
- Disclose the diagnosis, proposed procedure, alternatives, material risks, and expected outcome. Document the discussion and the patient's agreement in the record.
- Record retention
- Retain clinical records for the period required by law, often 7–10 years and longer for minors. Records must be legible, dated, and include advice given.
- Scope of practice
- Professionals must limit care to procedures permitted by licensure and their training. Refer patients when a condition falls outside that competence.
- Patient abandonment
- Terminating care without reasonable notice or transfer opportunity constitutes abandonment. Provide records on request and document the transfer arrangement.