Preparing for the Ophthalmology Station in Medical School OSCEs

Vishanna Balbirsingh 

A common objective structured clinical examination (OSCE) station for medical students is an ophthalmology station where students are required to examine the eye and communicate their findings. In many medical schools in the United Kingdom (UK), a mannequin is used where pictures can be inserted in the mannequin’s eye of fundus images with pathologies.

It is often an area of anxiety for students as they have little practice examining patients’ eyes. Below the steps involved in examining the eye and communicating findings, in a 10-minute OSCE station, are examined.

Section A: Examining a Mannequin’s Eye

Objective: To learn how to perform a thorough and systematic eye examination on a mannequin’s eye, ensuring that you can demonstrate proficiency in the core elements of an eye exam.

Step 1: Preparation

Before beginning the examination, ensure that you have all necessary equipment including: (i) Penlight (for direct inspection of the eye), (ii) Ophthalmoscope (for fundoscopy), (iii) Tuning fork (for assessing visual acuity and extraocular movements), (iv) Cotton wool (for testing sensation), and (v) Eye chart (for visual acuity testing).

Step 2: Approach the Station Calmly

As you begin the station, it is useful to start with a brief introduction, for example “Good morning/afternoon. I will now perform a systematic examination of the eye. I will first inspect the external features of the eye and then proceed to assess visual acuity and perform fundoscopy.”

Step 3: External Examination

Start with the external structures of the eye:

  1. Inspection: Examine the eyelids, lashes, and surrounding skin for any abnormalities such as ptosis, lid swelling, or masses.
  2. Assessment of Pupil Reflexes:
    • Check direct and consensual reactions to light by shining a penlight into each pupil and observing the response.
    • Assess the accommodation reflex by asking the mannequin to focus on a near object (e.g., your finger) and then shift focus to a distant object.
  3. Corneal Light Reflex: Shine a light at the midline of the mannequin’s face and observe the reflection of light on both corneas. This will help assess for any strabismus (misalignment of the eyes).
  4. Visual acuity: Explain to the examiner that you would ask the patient to read from the Snellen eye chart (or assume its vision if it’s a mannequin). Record the vision as a fraction (e.g., 20/20 or 6/6). If visual acuity is impaired, consider other causes such as refractive errors or ocular pathology.
  5. Visual fields: Ask the patient to cover one eye while you cover your corresponding eye and ask them to focus on your nose; then, using your hands or a target, move an object into their peripheral vision from various directions, asking them to report when they see it. Repeat the process for the other eye, and compare the patient’s visual fields to yours to detect any abnormalities, such as field defects or blind spots
  6. Eye movements: Move your finger in the six cardinal directions to assess for any restriction in movement, nystagmus, or abnormalities in extraocular muscle function.

Section B: Interpreting Fundus Images

Objective: To learn how to systematically interpret fundus images, including identifying common ocular pathologies.

Step 1: Introduction to Fundus Examination

Fundus images are essential in diagnosing a variety of eye conditions, such as diabetic retinopathy, glaucoma, and macular degeneration. The ophthalmoscope is used to visualize the retina and its structures. However, in the OSCE, you may be given a fundus image to interpret instead of performing a live fundoscopy.

Step 2: Key Structures to Identify

When interpreting fundus images, focus on the following structures:

  1. Optic Disc: This is the point where the optic nerve enters the retina. It should appear pale and round. Any changes in its size, colour, or shape may indicate pathology (e.g., glaucoma, papilledema).
  2. Macula: The small, central part of the retina responsible for detailed vision
  3. Fovea: This is the small depression in the macula where the sharpest vision occurs. Any changes in the fovea can indicate macular disease.
  4. Retinal Vessels: The arteries (narrower and brighter) and veins (wider and darker) should be evenly distributed. Any changes in their calibre or tortuosity can suggest systemic conditions such as hypertension or diabetes.

Step 3: Common Fundus Pathologies

As you examine the fundus image, be aware of the following common pathologies:

  1. Diabetic Retinopathy: Look for microaneurysms, haemorrhages, cotton wool spots, and exudates. These changes often occur in a characteristic pattern (1).
  2. Hypertensive Retinopathy: Check for arterial narrowing, arteriovenous (AV) nicking, and retinal haemorrhages, which are signs of chronic hypertension (2).
  3. Glaucoma: Examine the optic disc for cupping. The ratio of the cup to the disc should not exceed 0.3 in a healthy eye. An increased cup-to-disc ratio suggests optic nerve damage, often seen in glaucoma (3).
  4. Macular Degeneration: Look for drusen (yellow deposits) near the macula, or signs of macular haemorrhage and degeneration (4).
  5. Retinal Detachment: Signs may include elevated retina, areas of folding, or tearing in the retina (5).

Step 4: Practice

In the OSCE, you may be shown multiple fundus images. The goal is to rapidly assess the images for abnormal findings and provide a clear, concise diagnosis.

When interpreting fundus images:

  • Identify key structures (optic disc, macula, blood vessels).
  • Look for asymmetry or abnormalities in these structures.
  • Describe the findings succinctly (e.g., “The optic disc shows increased cupping, consistent with glaucoma”).

Section C: Tips for Success in the OSCE

  1. Stay Calm and Methodical: Practice maintaining a calm, systematic approach throughout the exam. In OSCEs, examiners are looking for structure and thoroughness.
  2. Time Management: You may have limited time at each station, so ensure that you perform key steps efficiently. Keep an eye on the clock and avoid spending too long on one aspect of the exam.
  3. Clear Communication: Clearly state your findings aloud, even if the mannequin cannot respond. This demonstrates your clinical reasoning and provides the examiner with insight into your thought process.
  4. Be Prepared to Explain Your Findings: If asked, provide a brief rationale for your interpretation of the fundus images or eye exam results.

References

1. Cai J, Boulton M. The pathogenesis of diabetic retinopathy: old concepts and new questions. Eye [Internet]. 2002 May [cited 2024 Dec 16];16(3):242–60. Available from: https://www.nature.com/articles/6700133

2. Tsukikawa M, Stacey AW. A Review of Hypertensive Retinopathy and Chorioretinopathy. Clin Optom. 2020;12:67–73.

3. Davis BM, Crawley L, Pahlitzsch M, Javaid F, Cordeiro MF. Glaucoma: the retina and beyond. Acta Neuropathol (Berl) [Internet]. 2016 Dec [cited 2024 Dec 16];132(6):807–26. Available from: http://link.springer.com/10.1007/s00401-016-1609-2

4. Taylor TRP, Menten MJ, Rueckert D, Sivaprasad S, Lotery AJ. The role of the retinal vasculature in age-related macular degeneration: a spotlight on OCTA. Eye [Internet]. 2024 Feb [cited 2024 Dec 16];38(3):442–9. Available from: https://www.nature.com/articles/s41433-023-02721-7

5. Ghazi NG, Green WR. Pathology and pathogenesis of retinal detachment. Eye [Internet]. 2002 Jul [cited 2024 Dec 16];16(4):411–21. Available from: https://www.nature.com/articles/6700197

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