Rx Note

Introduction Physiological and biochemical exists to protect the eye from harmful stimuli. Tears contain lysozymes and immunoglobulins, which impart an anti-infectious activity. While these mechanisms are protective, they do sometimes present to drug absorption. The tear volume in the normal is 5-9 µL. Basal tears are continuously secreted by the lacrimal glands at an average rate of 1.2 µL/min, thus giving a tear turnover rate of approximately 17% per minute. Reflex tears are triggered by irritants, and their secretion rate ranges from 3 to 400 µL/min, the intention being rapidly to eliminate the stimulus. Another protective mechanism is the eyelid movements associated with blinking. Blinking moves tear fluids and foreign matter to the nasal corner of the lid surface, where the liquid exits via the puncta and is then drained away by the nasolacrimal ducts into the inferior nasal passage - often called the lacrimal pump Topical ophthalmic preparations are medications applied directly t...