DHA Optometrist common mistakes
DHA Optometrist · Understand the traps and how to avoid them.
Converting a sphero-cylinder prescription to a different cylinder sign without adjusting the sphere and axis, e.g. writing +1.00/-2.00 x 180 as +1.00/+2.00 x 180.
Candidates memorise the rule that axis changes by 90 but forget that the sphere must equal the sum of the old sphere and old cylinder, so the transposition is internally inconsistent.
What to do instead
Drill the full three-step transposition (new sphere = old sphere + old cylinder; new cylinder = same power, opposite sign; new axis = old axis ±90, keeping it between 1 and 180) on at least 20 worked examples until the check 'new sphere + new cylinder = old sphere' becomes automatic.
Choosing the final prescription by simply accepting the maximum-plus or least-minus that gives best acuity, ignoring binocular balance and the patient's tolerance history.
Candidates treat refraction as a monocular endpoint exercise and forget that over-minusing a hyperope or over-plussing a myope can disturb accommodation and binocular balance.
What to do instead
Practise the sequence: monocular best vision, then binocular balance (alternating cover or fogging), then duochrome/red-green refinement, and always state the rationale for the final sphere in terms of both acuity and comfort.
Reporting a retinoscopy result without subtracting working distance, or subtracting it in the wrong direction.
The working distance lens effect is applied inconsistently under time pressure, and candidates confuse 'with' and 'against' motion with the sign of the neutralisation lens.
What to do instead
Fix the working distance (e.g. 50 cm = -2.00 D) at the start of every practice attempt, write it on the record, and apply 'subtract the working distance power algebraically from the sphere' as a written step before transposing.
Fitting a soft contact lens by base curve alone, without checking diameter, sagittal depth or corneal diameter, and without a fluorescein assessment of centration and movement.
Candidates reduce lens selection to a single number and skip the on-eye evaluation because it feels subjective.
What to do instead
Use a structured fitting checklist every time: keratometry/HVID, lens total diameter relative to HVID, fluorescein pattern (centration, edge lift, movement on blink), over-refraction, and a documented pass/fail against each criterion.
Missing the red flags that convert a routine eye examination into an urgent referral, such as sudden painless vision loss, flashes and floaters with a field defect, or a painful red eye with a fixed pupil.
Candidates focus on the refractive result and treat symptoms as background, and they have not rehearsed the differential for acute presentations.
What to do instead
Build a one-page 'refer now' list (retinal detachment symptoms, giant cell arteritis, acute angle closure, microbial keratitis, chemical injury) and practise classifying 30 symptom vignettes into routine, soon, and emergency.
Describing a pathological process by naming the disease rather than the mechanism, e.g. answering 'cataract' when asked what causes the lens opacity at a cellular level.
Candidates revise from lists of diagnoses rather than from tissue-level pathophysiology, so they cannot answer mechanism-based stems.
What to do instead
For each major condition, write three lines: tissue affected, cellular/biochemical change, and functional consequence (e.g. lens crystallin aggregation and oxidative damage leading to light scatter and reduced contrast sensitivity).
Prescribing or recommending a drug without checking the relevant contraindication, e.g. advising a topical steroid or a mydriatic in a patient with a known risk profile, or missing the interaction with the patient's systemic medication.
Candidates recall the indication well but not the caution list, and they do not habitually take a medication and allergy history before recommending anything.
What to do instead
Adopt a fixed drug-safety script: indication, dose and duration, contraindications, interactions, and follow-up. Rehearse it for the common optometric agents (topical antibiotics, steroids, antihistamines, mydriatics, artificial tears).
Interpreting a cover test or ocular motility finding without first establishing whether the deviation is comitant or incomitant, and without recording the measurement at distance and near with and without correction.
Candidates jump to a diagnosis (e.g. 'exotropia') from a single observation and skip the systematic measurements that distinguish the underlying cause.
What to do instead
Follow a fixed strabismus work-up: cover/uncover, alternate cover with prism neutralisation at distance and near, versions and ductions, and a note on comitance. State the diagnosis only after all four are documented.
Reporting a visual field or imaging result as 'abnormal' without describing the pattern, location and reliability indices, or without relating it to the expected defect for the suspected condition.
Candidates treat diagnostic tests as pass/fail and do not practise structured interpretation, so they cannot match a defect pattern to a lesion site.
What to do instead
Interpret every field with a fixed template: reliability indices first, then defect type (arcuate, altitudinal, hemianopic, central), then laterality and respect of the vertical or horizontal meridian, then the anatomical correlation.
Answering professional-practice or regulatory questions from general ethical instinct rather than from the specific Dubai Health Authority requirements on registration, scope of practice, record keeping, consent and referral.
Candidates prepare the clinical domains thoroughly and treat the regulatory domain as common sense, so they miss jurisdiction-specific rules and mandatory documentation standards.
What to do instead
Study the current DHA professional regulations and facility licensing standards directly, and build a one-page summary of mandatory record content, consent requirements, scope-of-practice limits and referral obligations, then test yourself on scenario questions set in Dubai facilities.