The Effect of Actinoquinol with Hyaluronic Acid in Eye Drops on the Optical Properties and Oxidative Damage of the Rabbit Cornea Irradiated with UVB Rays

Abstract

Irradiation of the cornea with UVB rays leads to its oxidative damage, swelling and increased light absorption. We investigated changes in the corneal optics (evaluated by changes of corneal hydration and light absorption) and microscopical disturbances of corneas irradiated with UVB rays as influenced by eye drops containing actinoquinol with hyaluronic acid. Rabbit corneas were irradiated with a daily dose of 0.5 or 1.01 J cm(-2) of UVB rays (312 nm) for 4 days. During irradiation, the eye drops were applied on the right eye and buffered saline (or hyaluronic acid) on the left eye. On day 5 the rabbits were sacrificed and the corneas examined spectrophotometrically for light absorption. The corneal thickness (hydration) was measured using a pachymeter. Corneas of some other rabbits were examined immunohistochemically. After buffered saline treatment UVB rays evoked changes in the corneal optics and induced oxidative damage of the corneas. After actinoquinol-hyaluronic acid application, these changes were diminished. Hyaluronic acid alone was less effective. In conclusion, actinoquinol-hyaluronic acid eye drops decreased changes in corneal optics and suppressed oxidative damage in the UVB-irradiated cornea. However, the effective corneal protection by these eye drops was limited to the lower UVB dose.

Methods of Assessment of the Corneas of the Eyes Laboratory Rabbits Exposed to Solar Ultraviolet‐B Radiation

“…The technique was reported for rabbits in the 1950s (24) and provides an objective assessment of any compromise of the cornea since this will be expected to result in an increase in corneal thickness. Pachymetry is the logically preferred method for objective assessment of UV-B-induced cornea edema (rather than simply assigning a grade) and has been used in numerous rabbit studies to assess the effects of UV-B exposure (8,15,(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). The assessments of corneal thickness do not need to be made by optical pachymetry on the living eye for an alternative is to use an ultrasound pachymeter.…”

The Reversibility of UV‐B Induced Alterations in Optical Properties of the Rabbit Cornea Depends on Dose of UV Irradiation

“…A spectrophotometrical method which we developed was used in this study to measure light absorption in corneas after 2 months of healing. Although the effect of repeated UVB doses of 0.5 and 1.01 J cm −2 on corneal light absorption and hydration was described , for comparison with healed corneas, in this study some corneas were examined 1 day after the last irradiation and some following 2 months of healing. The corneas were examined 1 day after the last irradiation because the development of UVB‐induced changes requires some time, called the latent period .…”

“…The UVB-induced corneal disturbances result in the increase in light absorption in the cornea (38,39). Although it was described (38,40) that corneal light absorption increased along with the increase in UVB dose applied on the cornea, the novelty of this study consists in the investigation of the reversibility of these changes. To examine the reversibility of UVB-induced changes in corneal light absorption is important because the increased light absorption in the cornea leads to a decrease in visual acuity (38).…”

Hydration and Transparency of the Rabbit Cornea Irradiated with UVB-Doses of 0.25 J/cm2and 0.5 J/cm2Compared with Equivalent UVB Radiation Exposure Reaching the Human Cornea from Sunlight

“…37 With the aim of decreasing the damaging effect of UVB radiation on the eye, we examined in a rabbit irradiation model the efficacy of eye drops containing the sunscreen actinoquinol combined with hyaluronic acid. 38 In these experiments, during irradiation with a dose of 0.5 J/cm 2 the tested eye drops were applied on the right eye and buffered saline on the left eye. Using this UVB dose in our study, in which no drops were applied on the eye surface during irradiation, we can show that the application of buffered saline on the corneal surface during the irradiation procedures had no significant additional effect on changes in corneal hydration and transparency.…”