Makindo Medical Notes

👁️ Visual acuity must always be assessed at the bedside during any eye examination. It provides a crucial baseline for both ocular and systemic conditions, and can guide urgency of referral.

📍 About

• Visual acuity depends on the integrity of the entire optic pathway — from the eye to the occipital cortex.

🌟 Perfect Vision Requires:

• Clear focusing of light by the cornea & lens onto the retina.
• Unobstructed optical media (cornea, aqueous, lens, vitreous).
• Healthy retina with functioning photoreceptors.
• Intact optic nerve to carry signals to the brain.
• Normal neural pathways (optic chiasm → tracts → radiations → occipital cortex).
• Testing each eye separately avoids masking of unilateral pathology by binocular vision.

🩺 Clinical Assessment of Visual Acuity

• Importance: Detects refractive errors, retinal disease, optic neuropathies, or cortical dysfunction.
• Techniques:
  • Always test with corrective lenses (or pinhole) to exclude refractive error.
  • Assess each eye independently (cover–uncover method).
• Methods:
  • Bedside: Use printed material or standard near-vision cards if a Snellen chart is unavailable.
  • Snellen Chart:
    • Standard at 6 m distance (20 feet in US) or near card at ~14 inches.
    • Results expressed as a fraction — e.g. 6/6 (normal), 6/60 (severe impairment).
  • Pinhole test: Improves vision in refractive error but not in retinal/optic nerve disease.

🔬 Investigations

• If vision is reduced, further evaluation may include:
  • Fundoscopy — retinal & optic disc assessment.
  • Slit-lamp — anterior segment and lens.
  • Visual fields — glaucoma, stroke, retinal lesions.
  • OCT — macula & retinal nerve fibre layer.
  • MRI/CT — optic nerve or cortical pathology.

💊 Management

• Refractive errors: Correct with glasses/contact lenses.
• Ocular disease: Ophthalmology referral for cataract, macular degeneration, diabetic retinopathy, glaucoma.
• Acute vision loss: Urgent referral — consider central retinal artery occlusion (CRAO), retinal detachment, optic neuritis, or temporal arteritis.
• Chronic disease: Manage systemic causes (diabetes, hypertension) and monitor progression.

📌 Exam Tip

🔑 Always document visual acuity in both eyes with and without correction. If vision improves with pinhole → refractive error. If not → consider retinal, optic nerve, or cortical pathology.