Gonioscopy demonstration for an external examiner

1. Introduction and preparation

1. Wash hands and introduce yourself.
2. Confirm the patient’s identity and explain:
   “I need to examine the drainage angle of your eye using a special contact lens. I will put in an anaesthetic drop first. The lens may feel like pressure, but it should not be painful.”
3. Obtain consent. Ask about allergy to topical anaesthetic or previous relevant ocular problems.
4. Ensure the goniolens has been disinfected and is clean.
5. Perform this before pupillary dilatation, particularly when angle closure is suspected.
6. Dim the room lights. Bright light and pupillary constriction can artificially open a narrow angle.
7. Set the slit lamp to a narrow, short beam at the lowest illumination that still permits viewing. Avoid shining the beam through the pupil.
8. Seat the patient correctly, with forehead firmly against the headband and chin on the chin rest. Ask them to keep both eyes open and look straight ahead.

2. Anaesthesia and lens placement

1. Instil one drop of topical anaesthetic into the eye being examined.
2. Select the lens:

• Goldmann single/three-mirror lens: needs coupling gel.
• Zeiss/Posner/Sussman four-mirror lens: usually no coupling gel and permits indentation gonioscopy.

1. If using Goldmann, put a small amount of coupling gel on the contact surface, avoiding air bubbles.
2. Ask the patient to look up.
3. Gently retract the lower lid if necessary and place the inferior edge of the lens onto the inferior cornea.
4. Rotate/bring the lens onto the cornea smoothly, then ask the patient to look straight ahead. Avoid pressing on the globe.

3. Explain the image orientation

“With an indirect goniolens, I see the angle opposite the mirror. Therefore, to examine the inferior angle, I place the mirror superiorly.”

4. Examine the angle systematically

1. Begin with the inferior angle, because it is generally widest and trabecular pigmentation is often easiest to identify.
2. Then examine all four quadrants in a consistent order:

• Inferior
• Nasal
• Superior
• Temporal

1. Schwalbe’s line
2. Anterior non-pigmented trabecular meshwork
3. Posterior pigmented trabecular meshwork
4. Scleral spur
5. Ciliary body band
6. Iris root/recess

“I identify Schwalbe’s line, then the trabecular meshwork, followed by the scleral spur and ciliary body band. The most posterior structure visible indicates the degree of angle opening.”

5. Assess and describe what you see

• Angle width
• Most posterior structure visible
• Iris configuration: flat, convex, plateau-like, concave
• Trabecular meshwork pigmentation
• Peripheral anterior synechiae (PAS)
• Any abnormality such as:
  • Neovascularisation
  • Angle recession
  • Excess pigment
  • Pseudoexfoliative material
  • Blood in Schlemm canal
  • Tumour/cyst/foreign material

6. Grade the angle: Shaffer system

“The angle is open to the ciliary body band inferiorly and temporally, and to scleral spur superiorly and nasally, with moderate trabecular pigmentation and no PAS.”

7. Indentation gonioscopy, if the angle appears narrow or closed

1. First document the static view in dim light, primary gaze, without indentation.
2. Then gently press the lens posteriorly against the central cornea, without excessive force.
3. Observe the effect:

• If the angle opens, this indicates appositional closure.
• If it does not open, this supports peripheral anterior synechiae (PAS).

“On indentation, the angle opens, suggesting appositional iridotrabecular contact rather than PAS.”

“The area remains closed on indentation, consistent with PAS.”

8. Finish the examination

1. Remove the lens gently, usually by asking the patient to look up and breaking the inferior seal.
2. Wipe excess gel from lids and lashes.
3. Check that the patient is comfortable.
4. Repeat in the other eye.
5. Clean/disinfect the lens according to local infection-control policy.
6. Thank the patient and document findings.

Example of a complete OSCE-style presentation

“Gonioscopy was performed in a dim room using topical anaesthetic and a four-mirror goniolens. The patient maintained primary gaze, and static gonioscopy was performed before indentation. All four quadrants were examined. In the right eye, the angle was open to the scleral spur in all quadrants, with moderate trabecular pigmentation, a flat iris configuration, and no peripheral anterior synechiae or neovascularisation. Indentation did not reveal any additional abnormality. The left eye was examined similarly.”

High-yield errors to avoid

• Doing gonioscopy in a bright room.
• Directing the slit beam through the pupil.
• Pressing too hard with a non-indentation lens, causing corneal folds or artificial angle distortion.
• Forgetting that the mirror shows the opposite quadrant.
• Calling an angle open after asking the patient to look too far toward the mirror.
• Performing indentation before recording the true static angle.
• Failing to compare all four quadrants and both eyes.

Goldmann applanation tonometry: OSCE demonstration

Equipment

• Slit lamp with Goldmann applanation tonometer
• Disinfected prism or disposable cap
• Topical anaesthetic
• Fluorescein strip/drop
• Cobalt-blue filter
• Tissue/cotton wool

Step-by-step demonstration

1. Introduction and safety

1. Wash hands. Introduce yourself and confirm patient identity.
2. Explain the procedure:

   “I will measure the pressure inside your eye using a blue light and a small contact prism. I will first put in an anaesthetic and yellow dye drop. It should not hurt, although you may feel gentle contact.”

3. Obtain consent.
4. Ask about:
   • Allergy to local anaesthetic
   • Active red eye, discharge, suspected conjunctivitis or corneal infection
   • Recent corneal trauma or epithelial defect
5. Inspect the prism. It must be clean, intact, and free of cracks or residue. Ensure it has been disinfected or attach a disposable tip.
6. Check tonometer calibration according to local policy, ideally before the clinical session.

2. Prepare the patient

1. Seat the patient comfortably at the slit lamp.
2. Adjust chin rest and headband. Ensure the forehead is firmly against the headrest.
3. Ask the patient to keep both eyes open, look straight ahead, relax, and breathe normally.
4. Instil topical anaesthetic followed by a small amount of fluorescein into the lower conjunctival fornix. Avoid excessive fluorescein.
5. Ask the patient to blink gently to distribute the drops.

3. Set up the slit lamp and tonometer

1. Set the Goldmann tonometer dial initially to 1.0, equivalent to 10 mmHg.
2. Use the cobalt-blue filter.
3. Set the slit beam to maximum brightness and direct it at approximately 60 degrees to the prism.
4. Position the prism in front of the corneal apex.

4. Take the measurement

1. Without touching or pressing on the globe, gently separate the lids if required by holding them against the orbital rim. Do not exert pressure on the eye.
2. Advance the prism slowly until it just contacts the centre of the cornea.
3. Look through the slit-lamp oculars.
4. Identify the two green fluorescein semicircular mires, one upper and one lower.
5. Ensure the mires are:

• Centrally placed
• Equal in size
• Correct thickness, about 10% of the diameter of the arc

1. Rotate the dial until the inner borders of the upper and lower semicircles just touch.

“I adjust the force until the inner margins of the fluorescein semicircles are in contact.”

1. Read the dial and multiply by 10 to obtain IOP in mmHg.
   Example: dial reading 1.8 = 18 mmHg.
2. Withdraw the prism gently and repeat once to confirm, especially if the reading is unexpected or the mires were suboptimal.
3. Repeat on the other eye.

5. Complete the examination

1. Wipe away excess fluorescein if needed and ensure that the patient is comfortable.
2. Document the IOP, eye, time, technique, and any factors affecting reliability, such as corneal oedema, marked astigmatism, or poor cooperation.
3. Disinfect the reusable prism or dispose of the single-use cap.
4. Wash hands and thank the patient.

Short OSCE presentation

“I measured intraocular pressure by Goldmann applanation tonometry. After confirming consent and excluding suspected ocular infection or corneal injury, I applied topical anaesthetic and fluorescein. With the patient positioned at the slit lamp, I used cobalt-blue illumination at approximately 60 degrees and set the dial initially to 10 mmHg. I gently contacted the central cornea with the prism, avoiding pressure on the globe. I adjusted the dial until the inner edges of the two fluorescein semicircular mires just touched. The dial value multiplied by 10 gives IOP in mmHg. I repeated the measurement and documented the result and its reliability.”

Viva points

1. Principle of Goldmann applanation tonometry

P = F/A

• P = pressure inside an ideal sphere
• F = force required to flatten its surface
• A = area flattened

2. Why is fluorescein used?

3. What is the normal IOP?

4. Why use cobalt-blue light?

5. Why should the patient not squeeze their eyes?

6. Why must the patient not look down at the prism?

7. Causes of falsely high GAT readings

• Thick cornea
• Excess fluorescein: thick mires
• Corneal scarring or rigidity
• Corneal oedema can produce variable readings, although commonly falsely low
• Pressure on globe by fingers/lids
• Squeezing eyelids
• Valsalva/breath-holding
• Tight extraocular muscles, for example thyroid eye disease
• Marked astigmatism if not corrected for
• Incorrect calibration

8. Causes of falsely low GAT readings

• Thin cornea
• Insufficient fluorescein: thin mires
• Post-refractive-surgery cornea
• Corneal oedema
• Corneal irregularity
• Incorrect calibration

9. What if astigmatism exceeds 3 dioptres?

10. Contraindications or situations to defer contact GAT

• Suspected infectious conjunctivitis or keratitis, especially adenoviral disease
• Corneal epithelial defect, ulcer, or significant trauma
• Recent ocular surgery, depending on surgeon guidance
• Severe patient distress or inability to cooperate

11. Alternatives to Goldmann tonometry

• Perkins handheld applanation tonometer
• Tono-Pen
• iCare rebound tonometry
• Non-contact air-puff tonometry
• Dynamic contour tonometry
• Pneumotonometry

Disinfection of the Goldmann prism

Between patients

1. Wear gloves if indicated by local infection-control policy.
2. Remove visible fluorescein, tears, mucus, and debris first.
3. Use the manufacturer-approved protocol and local hospital infection-control policy. Do not assume every prism tolerates every disinfectant.
4. A commonly cited method for a reusable prism is immersion in 2% sodium hypochlorite for at least 5 minutes, followed by a thorough sterile-water or sterile-saline rinse and complete air-drying before reuse.
5. Inspect the prism after cleaning. Do not use it if there is cracking, clouding, swelling, roughness, or residual disinfectant.
6. Consider disposable single-use prisms/caps where available, especially in high-volume settings or where infection risk is a concern.

Important viva statement

“I would not rely on a 70% isopropyl alcohol wipe alone for a reusable Goldmann prism, because it may not provide adequate protection against viral transmission. I would follow the manufacturer-approved and local infection-control disinfection protocol, rinse thoroughly, dry completely, and inspect the prism before reuse.”

Post-exposure / high-risk patient

Binocular indirect ophthalmoscopy (BIO): fundus examination demonstration

Equipment

• Head-mounted binocular indirect ophthalmoscope
• Condensing lens, usually 20 D
• Dilating drops, if appropriate
• Tissue
• Optional scleral depressor/cotton-tipped applicator for peripheral examination

OSCE step-by-step method

1. Introduction, consent and safety

1. Wash hands, introduce yourself, confirm identity.
2. Explain:

“I will examine the back of your eye with a head-mounted light and a hand-held lens. The light is bright but the test should not be painful. Your vision may be blurred and light-sensitive if dilating drops are used.”

1. Obtain consent.
2. Ask about:
   • Previous adverse reaction to dilating drops
   • History/symptoms of angle closure glaucoma
   • Current red painful eye or acute visual loss
   • Whether they need to drive after dilation
3. Check visual acuity, pupils, and anterior segment first.
4. Dilate the pupil unless contraindicated or unsafe. If there is concern for narrow angles, assess the angle before dilatation.
5. Allow adequate time for dilation, usually 15-30 minutes depending on the agents used.
6. Advise the patient not to drive until their near vision and glare sensitivity have returned to normal.

2. Positioning and instrument set-up

1. Dim the room lights.
2. Recline the patient in a chair or lie them supine. A reclining position helps examination of the inferior retina.
3. Set the BIO headband comfortably and adjust the interpupillary distance.
4. Align and focus the illumination beam centrally in the viewing aperture.
5. Select a 20 D lens for routine examination. Hold it with the flat surface toward the patient.
6. Ask the patient to keep both eyes open and look at a distant target.

3. Obtain the red reflex

1. Start at roughly arm’s length, approximately 30-50 cm from the patient.
2. Direct the illumination through the pupil and obtain a good red reflex.
3. Hold the 20 D lens between yourself and the patient, centred in the optical path.
4. Move closer while maintaining the red reflex.
5. Move the lens gently forwards or backwards until the retinal image is sharply focused.

4. Important orientation statement for the examiner

“The BIO image is real, inverted, laterally reversed, and stereoscopic. Therefore, if the patient looks up, I examine the inferior retina; if the patient looks right, I examine the left peripheral retina.”

5. Examine the fundus systematically

1. Peripheral retina first
2. Posterior pole
3. Macula last or early if central visual symptoms require it

Peripheral fundus

1. Ask the patient to look in the direction that exposes the area you need:

• To view superior retina, patient looks down
• To view inferior retina, patient looks up
• To view temporal retina, patient looks nasally
• To view nasal retina, patient looks temporally

1. Examine each quadrant in a consistent order:

• Superior
• Temporal
• Inferior
• Nasal

1. Look for:

• Retinal tears, holes, lattice degeneration
• Retinal detachment or subretinal fluid
• Haemorrhages, exudates, cotton-wool spots
• Chorioretinal scars
• Neovascularisation
• Masses or pigmentary abnormalities
• Vitreous haemorrhage, cells, pigment, or posterior vitreous detachment

Posterior pole

1. Examine the optic disc:

• Colour: pink/orange or pale
• Margins: sharp or blurred
• Cup-to-disc ratio
• Neuroretinal rim
• Disc haemorrhage
• Swelling or atrophy

1. Examine the vessels:

• Artery-to-vein ratio
• Arteriolar narrowing
• Arteriovenous crossing changes
• Haemorrhages, emboli, sheathing or neovascularisation

1. Examine the macula and fovea:

• Ask the patient to look directly at the light briefly.
• Assess foveal reflex, pigmentation, oedema, haemorrhage, drusen, exudates, or membrane.

1. Compare the two eyes and document the findings.

6. Completion

1. Switch off the light, remove the lens, and make the patient comfortable.
2. Explain that blurred near vision and photophobia can persist for several hours after dilatation.
3. Document the examination, including whether the view was limited by cataract, vitreous haemorrhage, small pupil, or poor cooperation.

Example OSCE presentation

“I performed a dilated binocular indirect ophthalmoscopic examination using a 20 D condensing lens. The patient was reclined in a darkened room. I obtained the red reflex and focused the inverted, laterally reversed stereoscopic retinal image. I examined all four peripheral quadrants systematically, followed by the optic disc, vessels, macula and fovea. In the right eye, the media were clear, the disc margins were sharp with a cup-to-disc ratio of 0.3, vessels were normal, and the macula and peripheral retina were unremarkable with no retinal break or detachment.”

Scleral depression

Method

1. Explain that you will apply mild pressure on the eyelid/white of the eye to see the far periphery.
2. Use a sterile scleral depressor or cotton-tipped applicator.
3. To view the superior ora serrata at 12 o’clock:
   • Ask the patient to look down
   • Place the depressor externally over the upper lid at the tarsal margin
   • Then ask them to look up while gently advancing the depressor tangentially to create an internal retinal “bump”
4. Direct your view to the bump and inspect the retina around it.
5. Move gradually around the periphery.

Safety

• Keep the depressor tangential, not perpendicular, to the globe.
• Do not perform scleral depression in suspected or confirmed open globe injury.
• Use caution or avoid it in marked inflammation, severe pain, recent surgery, or very thin sclera.

Viva points

1. What is binocular indirect ophthalmoscopy?

2. What type of image does it produce?

3. Main advantage over direct ophthalmoscopy?

• Wider field of view
• Stereopsis
• Better peripheral retinal examination
• Can see through greater media opacity
• Allows scleral depression

4. Disadvantages?

• Lower magnification than direct ophthalmoscopy
• Requires pupil dilatation for a full examination
• More difficult to learn
• Bright light may be uncomfortable
• Image is inverted and reversed

5. What lens is commonly used?

6. What are the uses of a 28 D lens?

• Smaller pupil
• Greater field of view
• Shorter working distance
• Often useful in children

7. What about a 40 D lens?

8. How do lens power and magnification relate?

• Lower-power lens: more magnification, narrower field
• Higher-power lens: less magnification, wider field

9. Why dilate the pupil?

10. Why is the patient reclined?

11. How do you inspect the superior retina?

12. How do you inspect the inferior retina?

13. What is scleral depression?

14. Indications for scleral depression

• Symptoms of posterior vitreous detachment: flashes/floaters
• Suspected retinal tear or detachment
• Ocular trauma, once open globe injury is excluded
• Lattice degeneration
• High myopia
• Fellow eye of a patient with retinal detachment

15. Contraindication to scleral depression?

16. What should a normal fundus description include?

“Media are clear. Optic disc is pink with sharp margins, normal neuroretinal rim and cup-to-disc ratio. Retinal vessels are of normal calibre. Macula is flat with a normal foveal reflex. The peripheral retina is flat and attached for 360 degrees, with no tears, holes, haemorrhages, exudates or retinal detachment.”

17. Common examination errors

• Poor alignment of the BIO illumination and viewing system
• Failure to obtain a stable red reflex
• Holding the lens upside down
• Moving the head and lens independently rather than together
• Examining only the posterior pole and missing peripheral pathology
• Forgetting the inverted and laterally reversed image orientation
• Using scleral depression before basic BIO technique is reliable