DHA Optometrist flashcards
DHA Optometrist · 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.
- Corneal endothelium function
- A non-regenerating monolayer that maintains corneal deturgescence through Na+/K+ ATPase pumps, preventing stromal oedema and preserving corneal clarity.
- Fovea centralis
- A cone-only retinal depression temporal to the optic disc, free of retinal vessels, that provides maximal visual acuity and colour discrimination.
- Trabecular meshwork
- The drainage pathway that carries aqueous humour from the anterior chamber into Schlemm's canal; obstruction raises intraocular pressure in open-angle glaucoma.
- Reduced eye power
- The schematic eye has a total power of about +60 D, with the cornea contributing roughly +43 D and the crystalline lens about +17 D.
- Snell's law
- n1 sin θ1 = n2 sin θ2; light bends only when it crosses an interface between media of different refractive indices.
- Aqueous humour production
- Secreted by the ciliary epithelium at about 2–3 microlitres per minute and drained mainly through the trabecular meshwork into Schlemm's canal.
- Spherical equivalent formula
- Sphere plus half the cylinder power; used when a toric correction cannot be provided, such as in some soft lens fittings.
- Duochrome test interpretation
- If letters appear clearer on red the eye is myopically overcorrected; if clearer on green it is undercorrected, guiding a small sphere adjustment.
- Prentice's rule
- Induced prism in prism dioptres equals decentration in centimetres multiplied by lens power in dioptres; used to predict prismatic effect.
- Retinoscopy working distance
- The examiner subtracts the dioptric equivalent of the working distance: 50 cm adds +2.00 D, 67 cm adds +1.50 D, and 1 m adds +1.00 D.
- Retinoscopy with and against motion
- With motion means more plus is needed; against motion means more minus is needed until the reflex becomes neutral and fills the pupil.
- Prescribing rule
- Give the maximum plus and minimum minus lens power that maintains best visual acuity, reducing accommodative demand and asthenopia.
- Keratometry use
- Measures anterior corneal curvature and is used to select the base curve of rigid contact lenses and to estimate corneal astigmatism.
- Dk/t significance
- Oxygen transmissibility, not Dk alone, governs corneal oxygenation through a contact lens; higher Dk/t reduces hypoxic complications.
- Rigid lens fluorescein pattern
- Central pooling indicates a steep fit, while central bearing indicates a flat fit; an ideal pattern shows even apical clearance and edge clearance.
- Bacterial keratitis
- Presents with pain, photophobia, stromal infiltrate and possible hypopyon; urgent topical antibiotic therapy is first-line management.
- Acute angle-closure glaucoma
- Shows a mid-dilated fixed pupil, corneal oedema and markedly raised intraocular pressure; requires urgent IOP-lowering treatment and laser iridotomy.
- Prostaglandin analogue effects
- Topical prostaglandin analogues lower intraocular pressure by increasing uveoscleral outflow but commonly cause iris and eyelid pigmentation and lash lengthening.
- Cover test
- Detects manifest deviation by observing the uncovered eye's movement; the alternate cover test reveals latent deviations by fully dissociating fusion.
- Amblyopia management
- Reduced acuity without organic cause is treated by correcting refractive error and then occlusion or atropine penalisation during the critical period.
- Convergence insufficiency
- Characterised by near exophoria and a receded near point of convergence; managed with convergence exercises and sometimes plus lenses for near.
- Goldmann applanation tonometry
- The reference standard for intraocular pressure measurement; normal pressure is approximately 10 to 21 millimetres of mercury.
- Amsler grid
- A central visual field test that detects scotomas and metamorphopsia in macular disease such as age-related macular degeneration.
- Kestenbaum rule
- Estimates the magnification needed for reading from the reciprocal of best-corrected acuity, guiding low vision aid selection.
- DHA licensure
- Optometrists must hold a valid Dubai Health Authority licence to practise; scope covers refractive and some ocular conditions but excludes surgery.
- Informed consent
- Must be obtained before examination, pupil dilation or any procedure, with the patient understanding purpose, risks and alternatives.
- Infection control requirement
- Hand hygiene and disinfection of instruments between patients are mandatory to prevent cross-infection in optometric practice.
- Myopia correction
- Corrected with diverging minus lenses; hyperopia with converging plus lenses; astigmatism with cylindrical lenses at the correct axis.
- Anisometropia in children
- A difference greater than about 1 D risks amblyopia and warrants refractive correction and ongoing monitoring of visual development.
- Diabetic retinopathy signs
- Microaneurysms, dot-blot haemorrhages and hard exudates; proliferative disease requires laser photocoagulation or anti-VEGF therapy.
- OCT imaging
- Provides cross-sectional retinal images that detect macular oedema, epiretinal membranes and ganglion cell loss in glaucoma.
- Vertex distance effect
- Moving a minus lens away from the eye increases its effective minus power; high-power prescriptions must specify vertex distance.