Glaucoma

Aqueous Humour and Intraocular Pressure: The Target of Every Glaucoma Drug

Not one glaucoma drug touches the optic nerve it is trying to save. Every single agent — the drop the patient instils at bedtime, the tablet swallowed in an emergency — works on one small circuit of fluid inside the front of the eye. The eye makes a clear liquid, circulates it, and drains it, and the pressure inside is simply the balance between how fast it is made and how freely it leaves. Understand that circuit and you understand the whole pharmacology: every drug either turns down the tap or opens the drain. Miss it, and the drug names are just a list to memorise.

Prostaglandin Analogues: The First-Line Glaucoma Drug

For a century glaucoma was fought by turning the tap down — drugs that told the eye to make less fluid. Prostaglandin analogues did something cleverer: they opened a second drain the eye had barely been using. One drop at bedtime lowers pressure more than any other single agent, with none of the heart-and-lung baggage of the old beta-blockers. The cost is almost entirely cosmetic — a redder eye, a darker iris, longer lashes — which is exactly why the same molecule that saves sight is also sold to grow eyelashes.

Beta-Blockers and Carbonic Anhydrase Inhibitors: Turning Down Aqueous Production

Every glaucoma drug has one job: get the pressure down. Prostaglandins do it by opening a bigger drain. This chapter is about the other lever — the tap. The ciliary body quietly manufactures aqueous humour all day; turn that tap down and the pressure falls even if the drain never changes. Two classes do exactly this: topical beta-blockers and the carbonic anhydrase inhibitors. Both are elegant on the eye and treacherous off it, because a drop that lands on the cornea does not always stay in the cornea.

Alpha-2 Agonists, Pilocarpine and Rho-Kinase Inhibitors

Prostaglandin analogues, beta-blockers and carbonic-anhydrase inhibitors carry most of the day-to-day work of lowering eye pressure. But the glaucoma cabinet holds three more classes, and each earns its place for a specific reason. One has a dual action and a terrifying trap in babies. One is almost never used long-term — yet it is the single drop that can save an eye in acute angle closure. And one is the first genuinely new mechanism in decades. Learn what each does to aqueous humour, and the whole cabinet starts to make sense.

Acute Angle-Closure Glaucoma: The Ophthalmic Emergency

Most glaucoma is a slow thief, stealing sight over years without a symptom. Acute angle-closure glaucoma is the opposite: an eye that goes from normal to blinding in hours. The drainage angle slams shut, aqueous has nowhere to go, and the pressure inside the globe climbs to levels that can strangle the optic nerve in a single afternoon. It is one of the few true emergencies in ophthalmology — and one of the most satisfying pharmacology stories in medicine, because the treatment attacks the pressure from four directions at once. It is also a trap: the wrong eye drop, or the wrong systemic drug, can trigger the whole crisis.