Master Ophthalmology
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Core Concepts
The eye is a complex organ vital for vision. Key structures include the cornea (clear front window, primary refractive surface), iris (controls pupil size), lens (focuses light, changes shape via ciliary body), retina (light-sensitive tissue, converts light into electrical signals), and optic nerve (transmits signals to brain). Aqueous humor fills the anterior and posterior chambers, maintaining intraocular pressure (IOP) and providing nutrition; it's produced by the ciliary body and drains via the trabecular meshwork (angle). Vitreous humor is a gel filling the posterior segment. Vision is measured via Snellen charts (e.g., 6/6 normal). Pupillary light reflex involves optic nerve (afferent), pretectal nucleus, Edinger-Westphal nucleus, and oculomotor nerve (efferent). Fundoscopy visualizes the optic disc, retinal vessels, and macula.
Clinical Presentation
- Red Eye:
- Painful: Acute Angle-Closure Glaucoma (AACG), Keratitis/Corneal Ulcer, Anterior Uveitis, Scleritis.
- Painless: Conjunctivitis (allergic/viral/bacterial), Subconjunctival Haemorrhage, Episcleritis.
- Sudden Painless Vision Loss:
- Central Retinal Artery Occlusion (CRAO), Central Retinal Vein Occlusion (CRVO), Retinal Detachment, Vitreous Haemorrhage, Ischaemic Optic Neuropathy (e.g., Non-arteritic AION).
- Sudden Painful Vision Loss:
- Acute Angle-Closure Glaucoma (AACG), Optic Neuritis, Giant Cell Arteritis (GCA) causing Arteritic AION, Keratitis, Endophthalmitis.
- Gradual Vision Loss:
- Cataract, Chronic Open-Angle Glaucoma, Age-related Macular Degeneration (AMD), Diabetic Retinopathy, Optic Atrophy.
- Flashes & Floaters: Posterior Vitreous Detachment (PVD), Retinal Tear/Detachment, Vitreous Haemorrhage.
- Diplopia (Double Vision):
- Monocular: Refractive error, Cataract, Corneal pathology.
- Binocular: Cranial nerve palsies (III, IV, VI), Myasthenia Gravis, Thyroid Eye Disease, Orbital mass.
- Visual Field Defects: Glaucoma (arcuate scotoma), Stroke/Tumour (hemianopia, quadrantanopia), Optic nerve lesions (central scotoma).
- Proptosis/Exophthalmos: Thyroid Eye Disease, Orbital Cellulitis, Orbital Tumours.
- Photophobia: Uveitis, Keratitis, Meningitis, Migraine.
Diagnosis (Gold Standard)
Comprehensive eye exam: Visual acuity, pupillary reactions (checking for Relative Afferent Pupillary Defect - RAPD), extraocular movements, slit lamp examination (cornea, anterior chamber, iris, lens), tonometry (IOP measurement), and fundoscopy (optic disc, retina, vessels, macula). Specific gold standards for conditions:
- Glaucoma: Ocular coherence tomography (OCT) for retinal nerve fibre layer (RNFL) thickness, visual field testing (perimetry).
- Retinal Detachment: Indirect ophthalmoscopy (detailed retinal view).
- Macular Degeneration: OCT, Fluorescein angiography (for wet AMD).
- Diabetic Retinopathy: Fundoscopy (dilated), Fluorescein angiography.
- Optic Neuritis: MRI orbits/brain (demyelination).
- Giant Cell Arteritis (GCA): Temporal artery biopsy, raised ESR/CRP.
Management (First Line)
- Acute Angle-Closure Glaucoma (AACG): Topical beta-blocker (e.g., Timolol), topical alpha-agonist (e.g., Brimonidine), topical pilocarpine, systemic acetazolamide. Urgent laser peripheral iridotomy.
- Central Retinal Artery Occlusion (CRAO): Ocular massage, anterior chamber paracentesis, CO2 rebreathing (paper bag), sublingual isosorbide dinitrate. Aim for urgent referral within 90 minutes.
- Retinal Detachment: Urgent ophthalmology referral for surgical repair (e.g., vitrectomy, scleral buckle).
- Giant Cell Arteritis (GCA): High-dose IV methylprednisolone immediately upon suspicion, followed by oral prednisolone. Temporal artery biopsy within 1-2 weeks.
- Orbital Cellulitis: Urgent IV broad-spectrum antibiotics (e.g., Co-amoxiclav, Ceftriaxone). Surgical drainage if abscess.
- Keratitis/Corneal Ulcer: Topical broad-spectrum antibiotics (e.g., Moxifloxacin). Acyclovir for herpetic keratitis.
- Anterior Uveitis: Topical corticosteroids (e.g., Prednisolone), topical cycloplegics (e.g., Cyclopentolate, Atropine) to relieve pain and prevent synechiae.
- Chemical Eye Injury: Immediate and copious irrigation with saline/water for at least 30 minutes, then urgent ophthalmology review.
Exam Red Flags
- Sudden, painful, unilateral vision loss with red eye, fixed mid-dilated pupil, headache/nausea: Acute Angle-Closure Glaucoma (AACG) - **Urgently lower IOP.**
- Sudden, painless, unilateral vision loss ("curtain descending"), flashes & floaters: Retinal Detachment - **Urgent ophthalmology referral for surgery.**
- Sudden, profound, painless unilateral vision loss, "cherry-red spot" on fundoscopy: Central Retinal Artery Occlusion (CRAO) - **Ocular emergency, aim to restore flow within 90 minutes.**
- Sudden unilateral vision loss (painful or painless) in elderly patient, jaw claudication, scalp tenderness, headache, malaise: Giant Cell Arteritis (GCA) - **Immediate high-dose systemic steroids to prevent contralateral eye involvement/stroke.**
- Proptosis, pain, restricted eye movements, fever, reduced vision: Orbital Cellulitis - **Medical emergency, risk of brain abscess/meningitis, requires IV antibiotics.**
- Any red eye with associated vision loss, pain, photophobia, or ciliary flush: Suggests serious ocular pathology (e.g., keratitis, uveitis, AACG, scleritis) - **Requires urgent ophthalmology review.**
- New onset diplopia with other neurological symptoms: Requires neurological workup (e.g., stroke, tumour, myasthenia).
- Relative Afferent Pupillary Defect (RAPD): Indicates significant unilateral optic nerve or retinal pathology - **ALWAYS concerning.**
Sample Practice Questions
A 68-year-old woman presents to the emergency department with sudden onset of severe right eye pain, headache, and nausea. She reports seeing halos around lights and has blurred vision in the affected eye. On examination, her right eye is red, the pupil is fixed in a mid-dilated position, and the globe feels firm on palpation. Her visual acuity is significantly reduced in the right eye. There is no discharge.
A 72-year-old woman presents to the emergency department with a sudden onset of severe pain in her right eye, associated with blurring of vision, headache, and nausea. She reports seeing 'halos' around lights. On examination, her right eye is red with a hazy cornea, and the pupil is semi-dilated and unreactive to light. Intraocular pressure (IOP) is 58 mmHg in the right eye (normal range 10-21 mmHg). The left eye is normal.
A 60-year-old man reports a gradual decline in his peripheral vision over the last few years, causing him to frequently bump into objects or miss steps. He denies any pain, redness, or sudden vision changes. His best corrected visual acuity is 6/6 in both eyes. On fundoscopy, both optic discs show an increased cup-to-disc ratio and thinning of the neuroretinal rim. Intraocular pressure (IOP) is 24 mmHg in the right eye and 23 mmHg in the left eye.
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