Topically applied caffeine induces miosis in the ketamine/xylazine anesthetized rat

Pharmacokinetics and Tissue Distribution of Pilocarpine After Application to Eyelid Skin of Rats

Extending the delivery of drugs into the eyes while reducing systemic bioavailability is of utmost importance in the management of chronic ocular diseases. Topical application onto the lower eyelid skin, as an alternative to eye drops, is seen to be a valuable strategy in the treatment of chronic eye diseases. To elucidate the critical value of delivering drugs in solution onto the eyeball through the eyelid skin, pharmacokinetic studies of pilocarpine were conducted, and the results were verified using a direct pharmacodynamic study in rats. The mean residence time of pilocarpine after topical eyelid application to the eyelid skin, conjunctiva, eyeball, and plasma were 14.9, 8.50, 6.29, and 8.11 h, respectively. Conjunctiva and eyeball concentrations of pilocarpine at 8 h were 80-fold and 8-fold higher after topical eyelid application, respectively, than those for eye drops. Pupillary constriction was sustained over 8 h after topical eyelid application. Topical eyelid skin application exhibited a localized drug absorption and specific drug accumulation in the ocular tissues. Hence, it is rational to prepare topical formulations directed onto the eyelid skin, which is suitable for drugs required for long-term treatment.

Caffeine and the eye

Caffeine, a popular psychostimulant that acts as an adenosine receptor antagonist, is the most widely used drug in history, consumed daily by people worldwide. Knowledge of the physiological and pathological effects of caffeine is crucial in improving public health because of its widespread use. We provide a summary of the current evidence on the effect of caffeine on the eye. Most of the research conducted to date is in relation to cataract and glaucoma, two of the most common eye diseases among the elderly.

Effect of Single Administration of Coffee on Pupil Size and Ocular Wavefront Aberration Measurements in Healthy Subjects

No study has so far evaluated the impact of coffee drinking on ocular wavefront aberration (OWA) measurements. This study presents novel findings regarding the OWA of the eye following coffee intake. We aimed to evaluate the acute changes in pupil size and OWA of the eye after single administration of coffee. A total of 30 otherwise healthy participants were included in this prospective study. All subjects drank a cup of coffee containing 57 mg caffeine. Measurements of pupil size, total coma (TC), total trefoil (TF), total spherical aberration (TSA), and total higher order aberration (HOA) were performed before and at 5 minutes, at 30 minutes, and at 4 hours after coffee drinking using a wavefront aberrometer device (Irx3, Imagine Eyes, Orsay, France). The mean age of the study population was 20.30 ± 2.74 years. Pupil size did not show a significant change during the measurements (p > 0.05). A significant increase was observed in TF and HOA measurements following coffee intake (p = 0.029 and p = 0.009, resp.). Single administration of coffee results in significant increase in TF and total HOAs in healthy subjects without any effect on pupil diameter. Ultrastructural changes in the cornea following coffee intake might be of relevance to the alterations in ocular aberrations in healthy subjects.