Special Topics & Neuro-ophthalmology

Dry Eye Disease: Tears, Inflammation and the Ocular Surface

Dry eye sounds trivial — a dose of drops and be done with it. It is anything but. It is one of the commonest reasons a patient ever walks into an eye clinic, and it is one of the most quietly instructive stories in ocular pharmacology: a self-perpetuating vicious cycle that no single drop can break, treated by a ladder that climbs from simple lubricants all the way to drugs that switch off T cells on the surface of the eye. Learn dry eye and you learn how modern ophthalmology thinks — that the tear film is not just water, and that the real disease is inflammation.

Neuro-ophthalmology: Botulinum Toxin, Myasthenia and Idiopathic Intracranial Hypertension

The eye is the only place in the body where you can watch a nerve directly — the optic disc is brain tissue you can see with a light. So it is no surprise that neurological disease so often knocks first on the ophthalmologist's door: a drooping lid, a doubled image, a swollen optic nerve. What makes this corner of the subject beautiful is that the pharmacology runs in both directions. The same molecule that is one of the deadliest poisons known becomes a precise therapeutic. A weakness that a single injection can transiently reverse becomes a diagnosis. And a pressure inside the skull is lowered by the very same drug used for glaucoma. This is the pharmacology at the interface of the eye and the brain.

Pharmacological Pupil Testing: Localising the Lesion With Drops

An unequal pupil is a small sign with a long differential — anything from a benign anatomical variant to a life-threatening aneurysm pressing on a nerve. You could reach straight for a scan of the whole neck, chest and brain. Or you could reach for a bottle of eye drops. Because the muscles of the iris are driven by two exquisitely mapped autonomic nerves, a denervated pupil betrays exactly where its nerve was cut by how it answers to a drug. A couple of drops, ten minutes in a dim room, and the abnormal pupil tells you which pathway is broken and roughly where — often sparing the patient an expensive, radiation-heavy hunt. This is autonomic pharmacology used as a scalpel.

Ocular Prescribing in Children and Pregnancy

A drop on the eye feels like the most local thing in medicine — a milligram of drug touching a surface the size of a fingernail. But that surface drains straight into the nose and the bloodstream, and it delivers the same dose whether the patient weighs 70 kilograms or 3. In an infant, a routine dilating drop can raise the blood pressure; a glaucoma drop can stop the breathing. In pregnancy, the same molecule that lowers eye pressure can reach a developing fetus. The whole discipline of prescribing eye drops in these two populations comes down to one habit of mind: never ask only what the drop does to the eye — ask what dose it delivers to the body.