Makindo Medical Notes

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 tumors (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 tumors, 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 tumors.

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 tumor, 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, tumor 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 tumor).
• 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.