OEBC OSCE Component cheat sheet

Chief complaint is recorded in the patient's own words, then expanded using onset, duration, frequency, severity, location, quality, aggravating and relieving factors, and associated symptoms.

Sudden painless monocular vision loss suggests retinal artery occlusion, retinal detachment or vitreous haemorrhage; sudden painful loss suggests acute angle closure, uveitis or microbial keratitis.

Flashes with new floaters and a curtain-like field defect indicate retinal tear or detachment and require same-day dilated funduscopy.

Monocular diplopia persists with either eye covered and points to an ocular cause such as cataract, corneal irregularity or high astigmatism; binocular diplopia resolves when either eye is covered.

Medication review: hydroxychloroquine (retinal toxicity after 5 years or >5 mg/kg/day), ethambutol (optic neuropathy), amiodarone (corneal deposits, optic neuropathy), topiramate (acute myopia, angle closure), tamsulosin (intraoperative floppy iris).

Headache with nausea, vomiting, halos and a mid-dilated fixed pupil is acute angle closure until proven otherwise; a painful pupil-involving third nerve palsy raises suspicion of aneurysm.

Family history of glaucoma, age-related macular degeneration, retinal detachment, keratoconus or high myopia raises risk and shortens screening intervals.

Communication sequence: open-ended opening question, uninterrupted listening, closed clarification, summary, then teach-back; use a trained interpreter, not a family member, for consent discussions.

Document the consent conversation for dilation, record sharing and procedures, including risks discussed and the patient's questions.

Slit lamp illumination modes: diffuse for overview, direct focal with an optic section for depth, indirect for opacities, retroillumination for subtle corneal or lens change, sclerotic scatter for oedema and scars, specular reflection for endothelium.

Van Herick technique compares peripheral anterior chamber depth with corneal thickness at the temporal limbus; grade 4 (depth equal to or greater than corneal thickness) is safe, grade 2 or less indicates a narrow angle and prompts gonioscopy.

Goldmann applanation requires topical anaesthetic and fluorescein, aligned mires, and gives intraocular pressure as dial reading multiplied by ten in mmHg; repeat readings and note the time of day.

Central corneal thickness alters applanation: thicker corneas read falsely high and thinner corneas falsely low, roughly 1 mmHg per 25 micrometres from a 540 micrometre reference in common clinical approximations.

Normal intraocular pressure is about 10-21 mmHg; diurnal fluctuation beyond 5 mmHg, asymmetry over 4-5 mmHg, or a pressure outside the range with suspicious discs warrants further glaucoma assessment.

Gonioscopy is performed in a darkened room with a short narrow beam kept off the pupil; the corneal wedge locates the angle structures and indentation distinguishes peripheral anterior synechiae from appositional closure.

Shaffer grading: 4 = 35-45 degrees (ciliary body visible), 3 = 25-35 degrees, 2 = about 20 degrees, 1 = about 10 degrees, 0 = closed; grades 0-1 indicate an occludable angle.

Direct ophthalmoscopy magnifies about 15 times and shows roughly two disc diameters undilated; a 78 D or 90 D condensing lens with the slit lamp gives a wider, stereoscopic, inverted and laterally reversed view.

Optic disc assessment records cup-to-disc ratio, neuroretinal rim according to the ISNT rule, pallor, disc haemorrhages, retinal nerve fibre layer defects and peripapillary atrophy; inter-eye ratio asymmetry of 0.2 or more is suspicious.

Snellen 6/6 equals 20/20; logMAR 0.0 equals 6/6 and each chart line changes acuity by 0.1 log unit; decimal acuity = 6 divided by the Snellen denominator in metres, and logMAR = minus log base ten of decimal acuity.

A pinhole that improves acuity indicates uncorrected refractive error or media opacity causing blur circles; no improvement suggests retinal or neural disease and requires ocular health assessment.

Retinoscopy working distance must be subtracted: 50 cm requires minus 2.00 D and 67 cm requires minus 1.50 D from the neutralization finding; with motion is neutralized with plus, against motion with minus.

Transposition: add the cylinder power to the sphere, reverse the cylinder sign, and change the axis by 90 degrees; plus-cylinder and minus-cylinder forms describe the same lens.

Jackson cross cylinder: handle aligned with the correcting cylinder axis to refine axis (rotate toward the clearer option), then handle 45 degrees away to refine power; add minus when the patient prefers the minus axis position.

Duochrome at the end of monocular refraction relies on chromatic aberration: if the red target is clearer add minus, if the green target is clearer add plus, keeping the eye slightly fogged.

Hofstetter's expected amplitude of accommodation in dioptres: minimum 15 - 0.25 x age, average 18.5 - 0.3 x age, maximum 25 - 0.4 x age; the push-up method records the first sustained blur.

Presbyopic add is set from the working distance demand (1/distance in metres) plus half the amplitude in reserve, adjusted for the patient's preferred near range and binocular balance.

A vertex distance change alters effective power; the shift is clinically negligible at low powers but significant above roughly 4.00 D of ametropia.

Cover test: observe the uncovered eye for movement as the cover is shifted; alternate cover test reveals the total deviation, and recovery speed and smoothness indicate control.

Hirschberg estimation: about 1 mm of corneal reflex displacement from the pupil centre equals roughly 7 degrees, or 12-15 prism dioptres; Krimsky testing neutralizes the reflex with prism for a measured deviation.

Near point of convergence is normally 5-7 cm break with recovery near 10 cm; a remote or absent NPC supports convergence insufficiency when paired with near exophoria and reduced positive fusional reserves.

AC/A by the heterophoria method = interpupillary distance in cm + (near phoria - distance phoria)/near fixation demand in dioptres; normal is about 4-6 to 1.

Worth 4-dot: four lights = fusion, two red = left eye suppressed, three green = right eye suppressed, five lights = diplopia; test at 6 m and 33 cm.

Stereoacuity norms: about 40 arc seconds of arc is normal on circle tests; the Titmus fly is 3000 seconds, animals 400-100 seconds, circles 800-40 seconds.

Developmental milestones: fixate and follow by about 3 months, acuity near 6/12 (20/40) by 3 years, and 6/6 by 5-6 years; constant esotropia after 2-3 months of age warrants referral.

Amblyopia is defined by an interocular acuity difference of two or more lines; 2-6 hours of daily patching is as effective as longer regimens for moderate amblyopia, with atropine penalization as an alternative.

Cycloplegic refraction with cyclopentolate 1% gives onset in 30-40 minutes and recovery within about 24 hours; it is required in children because of high accommodative tone.

Soft lens fit criteria: centred, 0.5-1.5 mm of post-blink movement, 0.5-1 mm of coverage beyond the limbus, no limbal impingement or conjunctival vessel compression.

A steeper base curve tightens the fit and a flatter base curve loosens it; rigid lens assessment uses the fluorescein pattern for alignment, apical clearance, bearing and edge lift.

Higher Dk/t reduces corneal oedema; overnight and extended wear are the strongest risk factors for microbial keratitis, so patients are counselled on strict wearing schedules.

Contact lens acute red eye presents with waking pain, redness and photophobia after overnight or tight lens wear; remove the lens, manage conservatively, and differentiate from microbial keratitis with staining and infiltrates.

Giant papillary conjunctivitis shows upper tarsal papillae over 1 mm with itching, mucus and reduced tolerance; managed by refitting, frequent replacement and mast cell stabilizers.

Care regimen: rub and rinse lenses, use multipurpose solution or a hydrogen peroxide system with full neutralization time, never use tap water, and replace the case at least every three months.

Sodium fluorescein with cobalt blue illumination and a yellow barrier filter grades corneal staining; lissamine green stains devitalized cells and is better for conjunctival assessment.

Tear break-up time of 10 seconds or more is normal and under 5 seconds indicates an unstable tear film that predicts lens intolerance.

Topical proxymetacaine or benoxinate anaesthesia lasts about 15-20 minutes; it is used for procedures only and never dispensed for home use because of toxicity and masking of injury.

Informed consent requires patient capacity, adequate disclosure of risks, benefits and alternatives, voluntariness, and contemporaneous documentation of the discussion.

Confidentiality is limited to need-to-know sharing for care; disclosure to third parties requires consent or a specific legal duty, and record requests are verified before release.

Records are legible, contemporaneous and complete, and are retained according to jurisdictional rules, typically at least 10 years from last contact and longer for minors.

A referral letter states the reason for referral, relevant history, examination findings, working diagnosis, specific request and urgency, so the receiving clinician can act without repeating the workup.

Fitness-to-drive assessment compares acuity and visual field against the local standard (commonly at least 6/12 acuity and 120 degrees horizontal field), and advice is documented when standards are not met.

Any financial interest in a product or referral is disclosed to the patient and managed so that clinical recommendations are not influenced by remuneration.

Statutory reporting duties override confidentiality for suspected child abuse, specified communicable diseases and drivers who are medically unfit; report only the information required.

Clinical errors are disclosed openly and promptly to the patient, the discussion is documented, and an incident report is filed; an apology is not, in most jurisdictions, an admission of liability.

Practice stays within competence and equipment; when findings exceed either, arrange timely co-management or referral rather than proceeding unsupported.