Does Photorefractive Keratectomy Alter the Effect of Topical Medications?

Abstract

Introduction: The influence of photorefractive keratectomy (PRK) on drug penetration into the eye is not yet established, as this procedure may alter the barrier function of the cornea as well as the blood ocular barrier. Pupillary response to topical tropicamide depends on its penetration into the anterior chamber. The purpose of this study was to examine the influence of PRK on pupillary response to topical tropicamide, and hence to evaluate whether PRK alters drug penetration into the eye. Methods: Pupillary diameter was measured using infrared pupillometer at 0, 15 and 30 min after instillation of 0.1% tropicamide to both eyes of 28 patients 4 weeks after PRK in one eye. The untreated eye served as control. Results: Pupillary diameter before and 30 min after dilation was 7.4 ± 1.2 and 8.0 ± 1.0 mm in the treated eyes and 7.5 ± 1.2 and 8.1 ± 1.0 mm in the untreated eyes, respectively (p = 0.45). Percentage of pupillary dilation (Δ pupillary diameter/pupillary diameter at 0 min ×100) was also similar in treated and untreated eyes for the entire study group (12.5 and 10.5%, respectively, p = 0.17). A trend for greater dilation was seen in patients with myopia above 6 diopters (13.7 and 10.5% in treated and untreated eyes, respectively, p = 0.11) and cornea thinner than 540 µm (14.2 and 10.1% in treated and untreated eyes, respectively, p = 0.1). Discussion: Our results confirm animal and human studies that found restoration of the ocular drug barrier at 4 weeks following PRK. The trend for greater penetration in patients with high myopia and thin corneas warrants further study on a larger cohort of this subgroup.

Effect of liposomal formulation of ascorbic acid on corneal permeability

“…In case of all investigated PC concentration BUS showed significantly higher permeability as positive corneal PAMPA control in comparison to HYD. The trend-like change in permeability is consistent with in vivo studies that report increased permeability and drug transport conditions in the inflammatory and postoperative states of the cornea 32 – 35 . Similar results were obtained for the dilutions of AA (API) solution and AA-LLipo formulation.…”

“…The characterization of the topical absorption of the liposomal formulation was performed in the corneal-PAMPA system developed by our research group, where healthy rabbit corneal penetration values of known drugs are used for the development of in vitro non-cellular permeability model 31 . However, changes in the integrity and enhanced penetration of partially damaged corneal epithelium during postoperative treatment and inflammatory processes have been reported in several studies 32 – 35 . Given the reduced permeability of AA due to its hydrophilic nature, which were wanted to be addressed by liposomal formulation, the modelling of the change in penetration in the healing process of the corneal epithelium was also aimed in this study.…”

Pupil response to tropicamide following LASIK

“…2 Our study was similar in design to the Chung and Feder study with 2 important exceptions. However, we have studied pupil response to tropical tropicamide to examine drug penetration in the eye in photorefractive keratectomy patients.…”