Eyes & Vision

A sudden mechanical blockage of aqueous outflow at the iridocorneal angle causes a rapid, severe rise in intraocular pressure, producing an excruciatingly painful red eye with visual loss that is an ophthalmic emergency.

Inflammation of the iris and ciliary body causes a painful, photophobic red eye with an irregular pupil and visual blurring, reflecting immune-mediated attack on the anterior uvea and often signalling an underlying systemic disease.

Progressive opacification of the crystalline lens scatters and blocks incoming light, causing gradual, painless blurring of vision that only surgery (replacing the lens) can reverse, because the damaged protein structure cannot be cleared or treated medically.

Inflammation of the conjunctiva from infection, allergy or irritation causes a red, gritty eye with discharge but preserved vision and a normal pupil: the mechanism that distinguishes it from sight-threatening causes of the red eye.

Chronic hyperglycaemia damages retinal capillaries, driving a progression from microvascular leakage to ischaemia to pathological new vessel growth, which is why screening and staging by the underlying vascular damage, not symptoms, determines when to treat.

Separation of the neurosensory retina from the underlying retinal pigment epithelium cuts off its blood supply and causes progressive, painless visual field loss, a surgical emergency where speed of treatment determines whether central vision is saved.