Red flags include dysphagia, unplanned weight loss, anorexia, haematemesis and/or melaena, older age, lack of response to therapy, chronic symptoms, and being on long-term therapy.
Basics
- Knowledge of retinal anatomy/physiology is essential.
- Cones: Concentrated centrally and responsible for color vision.
- Rods: Located peripherally and enable visibility in low light.
- The optic nerve enters the eye on the nasal side.
- The macula is densely packed with cones.
- Understand the optic pathways and be able to draw them accurately.
- Brainstem plays a role in controlling eye movements; knowledge of the anatomy of cranial nerves III, IV, and VI is necessary.
Appearance
- Partial Ptosis: Horner's syndrome, congenital, age-related, myasthenia gravis, myotonic dystrophy, myopathy.
- Full Ptosis: Indicates a third nerve lesion.
- Lid Retraction: Seen in Graves’ disease (thyrotoxicosis).
- Proptosis: Graves' thyroid eye disease, retroorbital tumours (e.g., optic nerve glioma, dermoid), carotid-cavernous fistula (pulsatile with bruit), orbital inflammation, or cellulitis.
- Red Eye: Causes include conjunctivitis, acute glaucoma, Graves' disease, orbital tumours, orbital cellulitis, carotid-cavernous fistula.
- Enophthalmos: Horner's syndrome.
Pupils - Light Reflex
- With the patient gazing into the distance, shine a bright light into each eye.
- Requires a functioning eye, optic pathway, optic radiations, and midbrain.
- Fibers synapse in the Edinger-Westphal nucleus, leading to bilateral pupillary constriction via cranial nerve III.
- Pathologies include Argyll Robertson pupil.
- Test for relative afferent pupillary defect (RAPD).
Pupils - Accommodation
- Patient looks at a distant point, then focuses on a finger held 10 cm away, which should cause pupil constriction and adduction.
- This response originates in the frontal lobes and travels efferently through the same pathways as the light reflex.
Dilated Pupil
- Causes: Cocaine, adrenaline, anticholinergics.
- Possible third nerve lesion with associated headache (consider SAH or PCOMM aneurysm).
- Holmes-Adie pupil: Unilateral semi-dilated pupil constricts slowly to light or accommodation, often seen in young women with decreased deep tendon reflexes.
Small Pupil
- Causes: Opiates, senile miosis, Horner's syndrome, Argyll Robertson pupils.
- Argyll Robertson pupils: Miosed, irregular pupils that accommodate but have no light reaction, associated with neurosyphilis, diabetes, and midbrain tumours.
Causes of Horner's Syndrome
- Symptoms: Unilateral miosis, mild ptosis, enophthalmos, facial anhidrosis.
- Light reflex is intact.
- Central Causes: Stroke, MS, trauma, syringomyelia.
- Peripheral Causes: Pancoast tumour, neck trauma, carotid dissection, left Horner’s from thoracic aortic aneurysm.
Acuity
- Test each eye individually using a Snellen chart or comparable assessment.
- If no chart is available, use small newsprint at 30 cm.
- Record as 6/60 (smallest line readable at 6m). Use a pinhole if glasses are unavailable.
Causes of Reduced Visual Acuity
- Corneal issues (ulcer, edema), cataracts, vitreous hemorrhage.
- Retinal causes: Hemorrhage, infarction.
- Optic neuropathy: Demyelination, ischaemia, compression.
- Optic pathway lesions (e.g., stroke, tumour in occipital lobe).
Optic Neuritis
- Characterized by visual loss, eye pain, altered color vision, and swollen disc.
- Common causes include multiple sclerosis, idiopathic conditions.
Optic Atrophy
- Signs: Pale disc, reduced acuity, impaired color vision.
- Causes: Glaucoma, multiple sclerosis, traumatic or ischemic optic neuropathy, chronic papilloedema, hereditary conditions (e.g., Leber’s optic neuropathy).
Relative Afferent Pupillary Defect (RAPD)
- Torch test by swinging from one eye to the other. Normal eye constricts to light, then dilates when light removed.
- In affected eye, dilation occurs despite direct illumination (Marcus Gunn pupil).
Visual Fields
- Commonly used to assess for hemianopia due to stroke or lesion. Light from the left is processed by contralateral optic radiations and occipital cortex.
- Screen for gross defects (e.g., upper or lower quadrants) by asking the patient to identify moving fingers in each quadrant.
Common Visual Field Defects
- Tunnel Vision: Chronic papilloedema, glaucoma, retinitis pigmentosa.
- Blind Eye: Often due to eye or optic nerve issues.
- Bitemporal Hemianopia: Typically from a chiasmal lesion (e.g., pituitary tumour).
- Homonymous Hemianopia: Lesion behind the chiasm (e.g., stroke).
Fundoscopy
- Dark Lesions: Retinitis pigmentosa, laser burns, melanoma.
- Macula: Cherry-red spot in central retinal artery occlusion.
- Haemorrhages: Dot (microaneurysms), blot (retinal bleeds), flame (superficial retinal bleeds).
- Optic Disc: Venous pulsations, papilloedema, atrophy, or cupping in chronic glaucoma.
Eye Movements
- Support the patient's head and assess both pursuit and saccadic movements.
- Pursuit: Follow an object in an “H” pattern.
- Saccades: Rapidly switch focus between two objects to detect discrepancies.
Cranial Nerves III, IV, and VI
- Oculomotor (III): Controls all eye muscles except lateral rectus and superior oblique. Lesion causes ptosis, "down and out" gaze, and dilated pupil.
- Trochlear (IV): Controls superior oblique, helping with downward and inward gaze. Lesion causes diplopia.
- Abducens (VI): Controls lateral rectus for eye abduction; lesion results in diplopia.
Internuclear Ophthalmoplegia (INO)
- Due to damage in the medial longitudinal fasciculus between cranial nerve nuclei III and VI, impairing horizontal gaze coordination.
- Often from MS, but also seen in pontine infarcts or diabetes.