Steroid-Induced Glaucoma and Cataract: The Price of Corticosteroids

Why steroids raise eye pressure

The eye's pressure is a balance between fluid made and fluid drained. The ciliary body continuously secretes aqueous humour, and it drains out mainly through a sieve-like tissue at the angle of the eye called the trabecular meshwork. Intraocular pressure (IOP) is simply the balance of the two. Corticosteroids don't increase how much fluid is made — they clog the drain. Glucocorticoids acting on the trabecular meshwork switch on genes that build up extracellular matrix (proteins like myocilin and fibronectin) and stiffen the cells' internal cytoskeleton. The meshwork becomes congested and less permeable, outflow resistance climbs, and pressure rises behind it. It is a plumbing problem: the tap runs the same, but the sieve is silting up. This raised-outflow-resistance mechanism is exactly the one taught in the Glaucoma subtopic, where lowering IOP by any means is the goal.

Crucially, not everyone reacts the same way. Susceptibility is genetically determined, and the population splits roughly into thirds: most people show little pressure rise, some show a moderate one, and about a third are true "steroid responders" whose IOP climbs substantially on potent steroids. Certain groups are far more likely to respond: patients with primary open-angle glaucoma (and their first-degree relatives), high myopes, people with diabetes or connective-tissue disease, and — importantly — children, who can respond fast and dramatically. The elevated pressure typically appears within a few weeks of starting a potent steroid, but with weaker agents or lower exposure it can smoulder over months.

Any route counts — not just eye drops

Students fixate on steroid eye drops, but the eye pays the price for steroids given almost anywhere. Topical ocular drops and ointments are the highest-risk because they deliver drug straight to the meshwork, but periocular injections and — increasingly — intravitreal steroid implants are a notable and often severe cause, sometimes producing very high, hard-to-control pressures. Beyond the eye itself: inhaled steroids for asthma, nasal sprays for rhinitis, steroid creams around the eyelids, and systemic oral or IV corticosteroids can all raise IOP in a susceptible person. Even a patient who has never touched an eye drop can develop steroid glaucoma from a long-term inhaler or a course of prednisolone. The intravitreal-implant route ties directly to the Retina chapter, where sustained-release dexamethasone and fluocinolone implants treat macular oedema — and buy that benefit at the cost of pressure rise and cataract.

Potent steroids versus "soft" steroids

The risk tracks with the steroid's potency and how long it lingers in the eye. Not all ocular steroids are equal offenders. The potent, penetrating agents — dexamethasone, betamethasone, and prednisolone acetate — are the strongest anti-inflammatories and, correspondingly, the most likely to raise pressure and hasten cataract. At the other end sit the "soft" or ester steroids, engineered to act at the eye surface and then be broken down before they can drive up pressure: loteprednol etabonate is the classic modern example, and fluorometholone and rimexolone are milder older options. The clinical bargain is a trade-off — a soft steroid is a safer choice for long or repeated courses (chronic allergic eye disease, dry-eye flares), while a potent steroid is reserved for serious intraocular inflammation where you accept the pressure risk and simply monitor closely. This potency-versus-safety balance is introduced in the Ocular steroids & NSAIDs chapter, and steroid-induced glaucoma is the hazard it warns about.

The silent thief: managing steroid glaucoma

The reason steroid-induced ocular hypertension is so feared is that it behaves like open-angle glaucoma: painless and asymptomatic until it has quietly eroded the optic nerve and carved away peripheral visual field. By the time a patient notices anything, irreversible nerve damage may already be done. That is the entire argument for monitoring — you cannot rely on symptoms. The management follows two tracks at once. First, address the cause: stop or taper the steroid, switch to a softer agent, or reduce the dose to the lowest that controls the underlying disease. In most people this alone lets the meshwork recover and pressure falls over days to weeks — but not always, and long or intense exposure can leave a permanently elevated pressure. Second, treat the pressure itself exactly as you would any glaucoma: IOP-lowering drops (a prostaglandin analogue, a beta-blocker such as timolol, an alpha-agonist, or a topical/oral carbonic-anhydrase inhibitor), and for the stubborn cases — especially high-pressure intravitreal-implant glaucoma — laser or surgery. The principle is simple: remove the trigger and lower the pressure until the nerve is safe.

The other price: posterior subcapsular cataract

Steroids also cloud the lens — in a distinctive, tell-tale place. The second great steroid complication is cataract, and it has a signature: it forms at the back of the lens, just under the rear capsule — a posterior subcapsular cataract (PSC). Its location matters clinically, because sitting right on the visual axis it scatters light and blurs near vision and reading out of proportion to how small it looks, and it glares badly in bright light. Steroid cataract is dose- and duration-dependent: the longer and higher the cumulative exposure, the greater the risk, whether from prolonged systemic steroids, chronic topical drops, or long-term inhalers. And unlike the pressure rise, it does not reverse when the steroid stops — a formed cataract is structural. The only treatment is surgical removal of the lens. This is the same posterior subcapsular pattern that appears in the systemic corticosteroid adverse-effect profile taught in the Endocrine and Inflammation sections, where the ocular toll of long-term steroids sits alongside osteoporosis, hyperglycaemia, and skin thinning.