Screening of Ophthalmic and Antiglaucoma Drugs

Introduction & rationale

• Definition — Experimental ophthalmic pharmacology is the preclinical (in-vitro / ex-vivo / in-vivo) evaluation of drugs acting on the eye — chiefly intraocular-pressure (IOP)-lowering (antiglaucoma) agents, plus miotics/mydriatics, ocular anti-inflammatories, anti-cataract agents, corneal anaesthetics and ocular-safety (irritation) profiling. It is the bench-and-animal methodology, not clinical ophthalmic pharmacotherapy.
• The IOP equation — The quantitative driver of every antiglaucoma assay: IOP = F/C + P_V, where F = aqueous formation rate, C = outflow facility, P_V = episcleral venous pressure — each target manipulates one of these three terms. Normal IOP ≈ 10–21 mmHg (mean ~15.5 mmHg); ocular hypertension (OHT) = raised IOP without disc/field damage (the key glaucoma risk factor); hypotony = IOP ≤ 5 mmHg.
• Goal of screening — Identify agents that lower IOP (below ~20 mmHg for mild, ~15 mmHg for severe disc change) or that are neuroprotective / anti-inflammatory / anti-cataract, using models that mimic the human disease and permit tonometric monitoring in the live animal.
• Ideal model criteria — Animal eye structurally resembling the human eye; an IOP-raising method that is easy, reliable/reproducible, permits live tonometry and minimises secondary inflammation; economical, easily housed animals.
  • The rabbit is the most common, feasible whole-eye model; rodents (rat/mouse) are increasingly preferred (availability, cost, genetic tractability), especially for laser and microbead models.