Glaucoma, Neuro-Ophthalmology, and Oculoplastics
Core concepts
Distinguish open-angle from angle-closure glaucoma by mechanism and presentation. Acute angle closure is an emergency: mid-dilated fixed pupil, corneal edema, high intraocular pressure, and a shallow anterior chamber; definitive treatment is laser peripheral iridotomy after pressure control. Understand the optic nerve head changes-cupping, disc hemorrhage, retinal nerve fiber layer loss-and the principle that IOP is a risk factor, not the definition. In neuro-ophthalmology, master the pupillary light reflex pathway to localize lesions: an afferent defect (RAPD) points to optic nerve or severe retinal disease, while an efferent defect points to the iris or third nerve. Know the classic optic neuritis triad (pain with eye movement, decreased vision, RAPD) and the difference between papilledema (bilateral, raised ICP) and optic disc drusen. For oculoplastics, know orbital compartment syndrome as a surgical emergency requiring lateral canthotomy.
Traps
Questions often mislead by pairing a red eye with glaucoma-only acute angle closure produces a red, painful eye with high pressure. Another trap is calling any swollen disc papilledema; papilledema requires bilateral involvement and raised ICP. Also remember that a third nerve palsy with a fixed dilated pupil suggests compression (surgical emergency), while pupil sparing favors ischemic etiology.
Worked example
A patient has a painful eye, halos, nausea, and a mid-dilated pupil with IOP of 50 mmHg. Diagnosis: acute angle closure. Rule of thumb: treat pressure medically first, then perform laser peripheral iridotomy to prevent recurrence.