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 30-year-old woman presents with acute onset of painful blurring of vision in her right eye, which developed over the last 3 days. She describes colours appearing 'washed out' or 'greyish'. On examination, her visual acuity is 6/18 in the right eye and 6/6 in the left. There is a relative afferent pupillary defect (RAPD) in the right eye. Ophthalmoscopy of both optic discs appears normal. She recalls a transient episode of numbness in her left leg 6 months ago that resolved spontaneously.
A 68-year-old man presents to the emergency department complaining of severe pain in his left eye, associated with blurring of vision, halos around lights, and headache for the past 4 hours. He also reports feeling nauseous and has vomited once. On examination, his left eye is red, the pupil is mid-dilated and fixed, and the globe feels firm to palpation. Intraocular pressure is measured at 48 mmHg (normal 10-21 mmHg). His right eye is asymptomatic with normal findings.
A 68-year-old man with a history of hypertension, type 2 diabetes, and atrial fibrillation presents with sudden, painless complete loss of vision in his left eye over the past hour. On examination, his left pupil has a relative afferent pupillary defect. Fundoscopy reveals a pale retina with a 'cherry-red spot' at the macula.
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