Direct Ophthalmoscopy

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Direct ophthalmoscopy is a troublesome skill for medical students and practitioners, but when practiced frequently, this is a technique that can be very useful in clinical practice. It is advisable that each medical student should purchase their own direct ophthalmoscopes as this technique is assessed in junior clerkship, senior clerkship and specialty clerkship. It is an essential skill for every medical practitioner.

Technique

• Sit the patient comfortably in a dimly lit room. Explain to the patient that you are going to get very close to his/her face and shine a bright light into his/her eye. Advise the patient not to look directly into the light. Dilating the pupils greatly improves fundal view.
• Always use your right eye to examine the patient’s right eye and your left eye for the patient’s left eye. Stand on the same side of the eye you are examining.
• Stand at one arm’s length away from the patient and shine the ophthalmoscope on the patient’s pupil to look for a red-light reflex (while you are looking through the ophthalmoscope). The presence of a strong red-light reflex indicates a lack of media opacity (cataracts, vitreous haemorrhage, intraocular tumors).
• Continue to fixate on the red-light reflex while you move closer to the patient’s eye. The first structure to look for is the optic disc (on the nasal side of the retina). Once you have found this, adjust the focus of your ophthalmoscope till the structures are at its sharpest. Look for optic disc pallor or swelling.
• Then work your way along each of the four main retinal vascular branches to look for exudates and haemorrhage.
• Finally ask the patient to look directly at the light to see the patient’s macula.

Clinical importance

The most important situation where a medical practitioner will have to perform a direct ophthalmoscope examination is in a patient with severe headache, where an intracranial space-occupying lesion is suspected. The presence of bilateral optic disc swelling (papilloedema) should point the examiner to raised intracranial pressure. Urgent referral to the Accident and Emergency Department is warranted. Direct ophthalmoscopy is also useful in the assessment of disorders of the optic nerve.

Approach to optic neuropathies

Disorders of the optic nerve may present with optic disc swelling during the acute phase and optic atrophy during the chronic phase. In both phases, signs of optic nerve dysfunction will be present and should be looked for.

Important signs to check

• Visual acuity
• Red-green colour desaturation
• Visual field
• Relative afferent pupillary defect

The diagnosis of an optic neuropathy and the determination of its cause usually cannot be made based on disc appearance alone.

Most common causes in children (usually bilateral)

1. Tumors compressing on the visual pathway
2. Trauma to the optic nerve
3. Hereditary optic neuropathies

Most common causes in adults

1. Ischaemic optic neuropathies
2. Optic neuritis
3. Tumors compressing on the visual pathway

Scenario 1: Acute unilateral visual loss with normal fundus exam

• Young adult with sudden onset visual loss with pain around and behind eye as well as pain on eye movement
• The most important differential diagnosis is optic neuritis
• In this condition women are affected more than men
• There is decreased central vision and more important red-green desaturation (often out of proportion to the drop in visual acuity). Relative afferent pupillary defect is positive
• In 2/3 of patients with optic neuritis, the disc appearance is normal, as it is a retrobulbar neuritis
• The most common cause in Western countries is demyelination
• In Asia, although demyelination is still the most likely diagnosis, systemic inflammatory and infectious diseases should be considered (syphilis, Cat-scratch disease)
• If an infective cause has been ruled out, patients are usually treated with a course of systemic steroids to hasten recovery
• Patients should then be investigated with investigations such as cranial +/- spinal magnetic resonance imaging (to determine whether there are other demyelinating lesions), lumbar puncture for oligoclonal bands and blood for anti-aquaporin-4 antibody (in patients with neuromyelitis optica – also known as anti-NMO antibody)

Scenario 2: Subacute unilateral visual loss with a normal fundus

• The most common diagnosis is non-arteritic ischaemic optic neuropathy
• There is usually no eye pain or pain on movement
• Red-green desaturation usually mirrors the drop in visual acuity
• Visual field examination usually gives an altitudinal or arcuate field defect
• Relative afferent pupillary defect is usually present
• Patients are usually over 55 years of age, men and women are equally affected
• Look for underlying systemic vasculopathy (hypertension, hyperlipidaemia, diabetes mellitus, migraine, obstructive sleep apnea). Other risk factors include use of erectile dysfunction drugs (vasodilators) and amiodarone use
• One important differential diagnosis is arteritic ischaemic optic neuropathy secondary to underlying giant cell arteritis (also known as temporal arteritis)
• Clinical features of this condition include profound cupping of the disc with a pale neuro-retinal rim (chalky white appearance)
• Associated local symptoms include jaw claudication, tongue claudication, scalp tenderness and ear pain
• Associated systemic include recent weight loss, flu-like illness, polymyalgia rheumatica

Scenario 3: Acute bilateral simultaneous visual loss

• Differential diagnoses include: intracranial mass, optic neuritis (especially that associated with neuromyelitis optica) and ischaemic optic neuropathy
• The most common area of compression by an intracranial mass is at the optic chiasm by a pituitary lesion. If the patient develops acute visual loss with bitemporal hemianopia, pituitary apoplexy should be suspected

Common mistakes in examinations

• Claiming to see the red light reflex without looking through the ophthalmoscope
• Injuring the patient with the ophthalmoscope
• Accidentally kissing the patient during examination
• Failure to get close enough to properly focus on the patient’s retina
• Looking for the optic disc at the temporal retina