Measuring Drug‐Induced Eye Irritation: A Simple New Clinical Assay

Abstract

Thirty-six normal subjects received a drop in either eye of two of four ophthalmic solutions, balanced saline (S), carteolol, 1% (C1), carteolol, 2% (C2), or timolol, 0.5% (T), in a double-blind, randomized trial in a balanced incomplete block design. Subjects reported immediately, at three, and again at ten minutes after administration whether one eye felt more irritated and marked an analog scale of irritation. An observer also made ratings at three minutes based on responses to stereotyped questions. Significant differences in irritation between timolol and each of the other drugs and placebo were shown by analog scale scores immediately after instillation of the solutions. Maximum likelihood estimates were calculated based on statements of subject preference, and a significant preference was demonstrated. Observer ratings also demonstrated a treatment effect. This simple clinical assay system provides a new, valid method for estimating irritation induced by ophthalmic solutions.