B.Optom Practical and Viva Stations: 30 OSCE-Style Stations With Model Answers

Task: Measure and record distance and near visual acuity in both eyes.

Examiner questions (answer aloud, then tap to check):

1. How do you record acuity on a 6 m Snellen chart if the patient reads the 6/9 line with two mistakes?
   Show answer

   6/9 −2 (or 6/12 if your clinic records the last complete line). Always state the chart and distance.
2. What if the patient cannot read the top letter?
   Show answer

   Move the patient closer (e.g. 3/60), then counting fingers, hand movements, perception of light with projection.
3. Why use a pinhole?
   Show answer

   To tell refractive error from other causes: improvement with pinhole suggests uncorrected refractive error.
4. Why is logMAR preferred in research?
   Show answer

   Equal steps between lines, five letters per line, each letter scored.

Examiner tip: Occlude properly (palm or occluder, not fingers pressing the eye) and test the worse eye first only if your protocol says so.

Task: Perform streak retinoscopy and give your gross and net findings.

Examiner questions (answer aloud, then tap to check):

1. What does "with" movement mean?
   Show answer

   The reflex moves in the same direction as the streak: the far point is behind you (hyperopia, low myopia or under-neutralised). Add plus.
2. How do you find the axis in astigmatism?
   Show answer

   Look for the break, the width and the skew of the reflex; rotate the streak until it aligns with the reflex.
3. Working distance correction at 67 cm?
   Show answer

   −1.50 D (at 50 cm, −2.00 D).
4. A scissors reflex suggests?
   Show answer

   Keratoconus or irregular cornea.

Examiner tip: Keep your working distance constant and the patient fixating the distance target with the other eye fogged.

Task: Refine sphere and cylinder after retinoscopy.

Examiner questions (answer aloud, then tap to check):

1. What is the end point of the sphere?
   Show answer

   Maximum plus for best visual acuity (MPMVA).
2. Which do you refine first with the cross-cylinder?
   Show answer

   Axis first, then power.
3. How do you keep the spherical equivalent constant?
   Show answer

   Add +0.25 D sphere for every −0.50 D cylinder added.
4. How do you check binocular balance?
   Show answer

   Prism dissociation (Humphriss or 3Δ up/down) or alternate occlusion, then balance with +0.25 D steps.

Examiner tip: Say what you are doing to the patient in plain words; examiners mark communication.

Task: Use the duochrome to check the sphere end point.

Examiner questions (answer aloud, then tap to check):

1. Green clearer: what do you do?
   Show answer

   Add plus (too much minus).
2. Red clearer?
   Show answer

   Add minus (too much plus).
3. Why does it work in colour-blind patients?
   Show answer

   It depends on chromatic aberration, not colour naming.
4. Ideal end point?
   Show answer

   Equal, or red very slightly clearer.

Examiner tip: Do it monocularly with the room lights dimmed.

Task: Determine a near add for a 50-year-old.

Examiner questions (answer aloud, then tap to check):

1. How do you measure amplitude?
   Show answer

   Push-up (RAF rule) or minus lens method, monocularly with distance correction.
2. Hofstetter minimum expected amplitude?
   Show answer

   15 − 0.25 × age.
3. How do you set the add?
   Show answer

   Leave half (or one-third) of the amplitude in reserve; check the range of clear vision at the working distance.
4. What else confirms it?
   Show answer

   Fused cross-cylinder or NRA/PRA balance.

Examiner tip: Always ask the patient's working distance before you finalise the add.

Task: Explain how you would refract a 5-year-old with suspected hyperopia.

Examiner questions (answer aloud, then tap to check):

1. Which drug and how many drops?
   Show answer

   Cyclopentolate 1% (0.5% under 1 year), one drop twice 5–10 minutes apart; refract after 30–45 minutes.
2. What do you check before instilling?
   Show answer

   Anterior chamber depth, history of seizures or heart disease, allergies.
3. What do you prescribe in accommodative esotropia?
   Show answer

   Full cycloplegic correction.
4. Side effects to warn about?
   Show answer

   Blurred near vision, light sensitivity, rarely flushing, fever or drowsiness.

Examiner tip: Mention the tonus allowance only if you prescribe less than the full correction in a child without esotropia.

Task: Read and record the power of a pair of glasses.

Examiner questions (answer aloud, then tap to check):

1. First step?
   Show answer

   Focus the eyepiece for your own eye.
2. How do you find the axis in a minus-cylinder reading?
   Show answer

   Focus the most plus meridian (sphere lines), note the axis, then focus the cylinder lines.
3. How do you mark the optical centre?
   Show answer

   Centre the target and use the marking pins.
4. How do you read prism?
   Show answer

   Note how far and in which direction the target is displaced from the centre.

Examiner tip: Read the right lens first with the frame bottom against the table.

Task: Measure corneal curvature.

Examiner questions (answer aloud, then tap to check):

1. What does the instrument measure?
   Show answer

   Radius of curvature of the central 3 mm of the anterior cornea.
2. Which refractive index converts radius to power?
   Show answer

   1.3375.
3. With-the-rule astigmatism?
   Show answer

   Vertical meridian steeper.
4. Uses?
   Show answer

   Contact lens fitting, IOL power calculation, monitoring keratoconus.

Examiner tip: Calibrate with a steel ball if asked; tell the patient to blink before you read.

Task: Demonstrate diffuse, direct focal and retro-illumination.

Examiner questions (answer aloud, then tap to check):

1. Which shows corneal endothelium?
   Show answer

   Specular reflection.
2. Which shows corneal oedema at the limbus?
   Show answer

   Sclerotic scatter.
3. How do you grade cells in the anterior chamber?
   Show answer

   1 mm × 1 mm high-magnification beam, count cells (SUN grading).
4. Van Herick technique?
   Show answer

   Narrow beam at the temporal limbus, angle 60°; compare peripheral chamber depth with corneal thickness.

Examiner tip: Start low magnification, then increase; adjust the eyepieces and chin rest before the patient sits.

Task: Measure IOP with a Goldmann tonometer.

Examiner questions (answer aloud, then tap to check):

1. Area flattened?
   Show answer

   3.06 mm diameter.
2. End point?
   Show answer

   Inner edges of the two semicircles just touching.
3. Errors?
   Show answer

   Thick mires (high reading), thin cornea or after LASIK (low), astigmatism over 3 D (rotate the prism).
4. How do you disinfect the prism?
   Show answer

   As per clinic protocol, e.g. hydrogen peroxide or alcohol wipe, or disposable tips.

Examiner tip: Ask about allergy to anaesthetic drops and remove contact lenses first.

Task: Examine the fundus and describe the optic disc.

Examiner questions (answer aloud, then tap to check):

1. What do you describe at the disc?
   Show answer

   Size, colour, margins, cup-to-disc ratio, rim (ISNT rule), vessels, haemorrhages.
2. Image in direct vs indirect ophthalmoscopy?
   Show answer

   Direct: erect, about 15× magnification, small field. Indirect: inverted, laterally reversed, larger field.
3. Which lens for the slit lamp?
   Show answer

   +90 D or +78 D.
4. Red flags needing same-day referral?
   Show answer

   Disc swelling, new retinal haemorrhages with sudden vision loss, retinal tear or detachment.

Examiner tip: Dim the room, use the patient's right eye with your right eye, and keep the patient fixating a distant target.

Task: Screen the visual fields.

Examiner questions (answer aloud, then tap to check):

1. How do you do confrontation?
   Show answer

   Sit 1 m away, eyes level, patient covers one eye, test each quadrant with finger counting or a red target.
2. What does the Amsler grid test?
   Show answer

   The central 10° (20° × 20° grid at 30 cm): metamorphopsia and scotoma.
3. Pattern in pituitary tumour?
   Show answer

   Bitemporal hemianopia.
4. When do you refer for formal perimetry?
   Show answer

   Any defect, glaucoma suspects, neurological symptoms.

Examiner tip: Keep your own eye open opposite the patient's open eye so you compare fields.

Task: Perform the cover–uncover and alternate cover test.

Examiner questions (answer aloud, then tap to check):

1. What does cover–uncover detect?
   Show answer

   Tropia (cover) and phoria (uncover).
2. Alternate cover test?
   Show answer

   Total deviation (phoria plus tropia).
3. How do you measure the angle?
   Show answer

   Prism cover test: prism base opposite the deviation until no movement.
4. Distance and near?
   Show answer

   Test at 6 m and 33 cm with an accommodative target.

Examiner tip: Keep the occluder in place 2–3 seconds and watch the uncovered eye first.

Task: Measure NPC and fusional vergences.

Examiner questions (answer aloud, then tap to check):

1. Normal NPC?
   Show answer

   Under about 6–10 cm (break).
2. How do you measure vergences?
   Show answer

   Prism bar or rotary prism: blur, break and recovery for base-out and base-in.
3. Sheard's criterion?
   Show answer

   Compensating vergence (blur) should be at least twice the phoria.
4. Convergence insufficiency signs?
   Show answer

   Exophoria greater at near, remote NPC, low base-out at near.

Examiner tip: Use an accommodative target and repeat NPC several times to check fatigue.

Task: Test for fusion, suppression and stereoacuity.

Examiner questions (answer aloud, then tap to check):

1. Four lights seen?
   Show answer

   Fusion (or harmonious ARC with a tropia).
2. Five lights?
   Show answer

   Diplopia.
3. Two red or three green?
   Show answer

   Suppression of the eye behind the green or red filter respectively.
4. Normal stereoacuity?
   Show answer

   About 40–60 seconds of arc.

Examiner tip: Check which filter is over which eye before you interpret.

Task: Examine eye movements and interpret a Hess chart.

Examiner questions (answer aloud, then tap to check):

1. Positions tested?
   Show answer

   Nine positions of gaze in an H pattern.
2. Hess chart: smaller field?
   Show answer

   Eye with the underacting muscle.
3. Sixth nerve palsy?
   Show answer

   Limited abduction, esotropia worse on looking to the affected side.
4. Fourth nerve palsy?
   Show answer

   Hypertropia worse on looking down and to the opposite side and on head tilt to the same side.

Examiner tip: Ask about double vision in each position.

Task: Test colour vision with Ishihara plates.

Examiner questions (answer aloud, then tap to check):

1. Test distance and lighting?
   Show answer

   75 cm, daylight or equivalent, 3 seconds per plate.
2. What does Ishihara detect?
   Show answer

   Red–green defects; not blue–yellow.
3. Which test grades severity?
   Show answer

   Farnsworth D-15 or 100-hue.
4. Inheritance of red–green defect?
   Show answer

   X-linked recessive (about 8% of men).

Examiner tip: Test each eye separately when looking for acquired defects.

Task: Assess the fit of a soft lens.

Examiner questions (answer aloud, then tap to check):

1. Signs of a good fit?
   Show answer

   Centred, full corneal cover, 0.2–0.4 mm movement on blink, easy push-up recovery.
2. Tight lens?
   Show answer

   Little movement, conjunctival indentation, vision fluctuates or improves after blink.
3. Loose lens?
   Show answer

   Decentration, excessive movement, edge stand-off, unstable vision.
4. How do you change the fit?
   Show answer

   Steeper or larger lens to tighten; flatter or smaller to loosen.

Examiner tip: Wait 10–20 minutes after insertion before assessing.

Task: Interpret a fluorescein pattern.

Examiner questions (answer aloud, then tap to check):

1. Alignment fit?
   Show answer

   Even thin fluorescein under the lens with an edge band.
2. Steep (apical clearance)?
   Show answer

   Central pooling, mid-peripheral touch, air bubble.
3. Flat (apical touch)?
   Show answer

   Central dark area, wide peripheral pooling, lens decentres.
4. With-the-rule toric cornea?
   Show answer

   Dumbbell pattern with touch horizontally.

Examiner tip: Use the cobalt blue filter with a yellow (Wratten) filter if available.

Task: The lens mark has rotated. Decide what to order.

Examiner questions (answer aloud, then tap to check):

1. LARS rule?
   Show answer

   Left add, right subtract (as you see the mark).
2. Lens rotated 10° to your right, axis 180?
   Show answer

   Order axis 170.
3. When to wait?
   Show answer

   If rotation is unstable from blink to blink, re-check fit first.
4. If over-refraction gives cylinder?
   Show answer

   Use a cross-cylinder calculation (e.g. the contact lens calculator).

Examiner tip: Confirm the mark position at 6 o'clock in primary gaze.

Task: Identify and manage common complications.

Examiner questions (answer aloud, then tap to check):

1. Red painful eye with a corneal infiltrate in a lens wearer?
   Show answer

   Treat as microbial keratitis: stop the lens, same-day referral.
2. Giant papillary conjunctivitis?
   Show answer

   Large papillae on the upper tarsus, mucus, lens intolerance; change to daily disposables, treat, refit.
3. Corneal neovascularisation?
   Show answer

   Chronic hypoxia; refit with higher Dk/t (silicone hydrogel) or reduce wearing time.
4. Acanthamoeba risk factors?
   Show answer

   Tap water, swimming in lenses, poor case hygiene.

Examiner tip: Always ask about sleeping in lenses and water exposure.

Task: Measure PD and fitting height for progressives.

Examiner questions (answer aloud, then tap to check):

1. Which PD for progressives?
   Show answer

   Monocular PD to each pupil centre.
2. Fitting height measured from?
   Show answer

   Pupil centre to the lowest point of the lens rim, frame adjusted on the face.
3. Near PD at 40 cm?
   Show answer

   About 3 mm less than distance PD.
4. Common error?
   Show answer

   Measuring in an unadjusted frame.

Examiner tip: Sit at the patient's eye level and close your right eye to measure their left.

Task: Recommend a lens and frame for a −7.00 D myope.

Examiner questions (answer aloud, then tap to check):

1. Material?
   Show answer

   High index (1.67 or 1.74) with AR coating, or polycarbonate.
2. Frame?
   Show answer

   Small, round or oval, PD close to frame PD, full rim.
3. Why?
   Show answer

   Thinner edges, less weight and less prism from decentration.
4. What to avoid?
   Show answer

   Large rimless frames.

Examiner tip: Explain the trade-offs: price, Abbe value and appearance.

Task: Transpose a prescription and give its spherical equivalent.

Examiner questions (answer aloud, then tap to check):

1. Transpose +1.00/−2.00 × 90.
   Show answer

   −1.00/+2.00 × 180.
2. Spherical equivalent of −2.00/−1.00 × 180?
   Show answer

   −2.50 D.
3. Near-only prescription for −1.00/−0.50 × 180, add +2.00?
   Show answer

   +1.00/−0.50 × 180.
4. Vertex correction needed above?
   Show answer

   About ±4.00 D.

Examiner tip: Write each step; examiners mark the method.

Task: Calculate prism from decentration.

Examiner questions (answer aloud, then tap to check):

1. Formula?
   Show answer

   Prism (Δ) = decentration (cm) × power (D).
2. +5.00 D lens decentred 4 mm out?
   Show answer

   2Δ base out.
3. Where is the base in a minus lens decentred outwards?
   Show answer

   Base in (minus lenses: base opposite to decentration).
4. Tolerance for horizontal prism (ANSI)?
   Show answer

   About 0.67Δ total.

Examiner tip: Draw the lens and the direction of decentration.

Task: Assess a patient with 6/60 vision due to macular degeneration.

Examiner questions (answer aloud, then tap to check):

1. Starting near add (Kestenbaum)?
   Show answer

   Reciprocal of the acuity: 60/6 = +10.00 D.
2. Which aid for spot reading?
   Show answer

   Hand or stand magnifier, electronic magnifier.
3. Which aid for television?
   Show answer

   Galilean or Keplerian telescope.
4. Non-optical aids?
   Show answer

   Lighting, contrast, large print, apps, typoscope.

Examiner tip: Ask about the patient's goals first: reading, faces, mobility.

Task: Explain how visual disability is graded in India.

Examiner questions (answer aloud, then tap to check):

1. Which law?
   Show answer

   Rights of Persons with Disabilities Act, 2016.
2. Based on?
   Show answer

   Best-corrected acuity in each eye and visual fields.
3. Who certifies?
   Show answer

   A medical board including an ophthalmologist.
4. Tool?
   Show answer

   The visual disability calculator on this site.

Examiner tip: Optometrists help with accurate acuity and fields; the board certifies.

Task: Assess a patient with dry eye symptoms.

Examiner questions (answer aloud, then tap to check):

1. Tests?
   Show answer

   Symptom questionnaire (OSDI), TBUT, fluorescein and lissamine staining, Schirmer, meibomian gland expression.
2. Abnormal TBUT?
   Show answer

   Under 10 seconds.
3. First-line management?
   Show answer

   Lid hygiene, warm compresses, preservative-free lubricants, screen breaks.
4. When to refer?
   Show answer

   Severe staining, filaments, systemic disease (Sjögren), no improvement.

Examiner tip: Do TBUT before any drops or contact tonometry.

Task: Decide whether a red eye needs urgent referral.

Examiner questions (answer aloud, then tap to check):

1. Red flags?
   Show answer

   Pain, reduced vision, photophobia, corneal opacity, irregular pupil, raised IOP, contact lens wearer, trauma.
2. Conjunctivitis features?
   Show answer

   Discharge, normal vision, no photophobia, follicles or papillae.
3. Acute angle closure?
   Show answer

   Pain, haloes, mid-dilated pupil, hazy cornea, high IOP: same day.
4. Chemical injury?
   Show answer

   Irrigate immediately, then refer.

Examiner tip: If in doubt, phone the ophthalmologist; never give steroid drops.

Task: Screen a diabetic patient's fundus.

Examiner questions (answer aloud, then tap to check):

1. What do you look for?
   Show answer

   Microaneurysms, haemorrhages, exudates, cotton-wool spots, venous beading, IRMA, new vessels, macular thickening.
2. Severe NPDR (4-2-1 rule)?
   Show answer

   Haemorrhages in 4 quadrants, venous beading in 2, IRMA in 1.
3. Referral urgency for new vessels?
   Show answer

   Urgent (within days).
4. Follow-up with no retinopathy?
   Show answer

   Yearly.

Examiner tip: Dilate unless contraindicated and examine the macula carefully.