The Effect of Artificial Tears on Visual Performance in Normal Subjects Wearing Contact Lenses

Clinical discussion on the relative efficacy of 2 surfactant-containing lubricating agents in removing proteins during contact lens wear

BACKGROUND

This clinical study aims to evaluate the clinical efficacy of 2 popular rewetting agents, Blink-N-Clean, manufactured by Advanced Medical Optics (Santa Ana, California), and Clens 100, manufactured by Alcon (Ft. Worth, Texas), on protein removal in a nonsymptomatic population of contact lens wearers fitted with etafilcon A soft contact lenses, Acuvue 2, manufactured by Vistakon, a division of Johnson and Johnson Vision Care (Jacksonville, Florida).

METHODS

This randomized, double-blind, crossover study was performed on 22 subjects who had been fitted successfully with etafilcon A soft contact lenses. Each subject was examined on 3 occasions, at 2-week intervals, to evaluate a number of clinical signs related to contact lens wear, with or without the use of ocular lubricants specifically designed to reduce the levels of proteins adsorbed on the lens. A washout period was observed between each of the study's different phases. High- and low-contrast visual acuity levels were measured using the Bailey-Lovie (logMAR) chart under mesopic and scotopic conditions. Protein levels adsorbed on the lenses were determined using a modified Lowry method. Ocular health was assessed under biomicroscopy using conventional techniques. Subjective comfort was also evaluated, using a questionnaire based on a Likert scale graded from 0 to 50.

RESULTS

Objectively, no significant difference in either visual acuity or comfort was found between the use or the nonuse of drops or the use of one specific product. Using Clens 100 allowed for a significant reduction in the quantity of protein on the lens surface. More than 3 subjects of 4 (77%) preferred the Clens 100 product, in large part because they found the size of drops dispensed from the Clens 100 bottle less disturbing during insertion because of the size of the drops and blur.

CONCLUSION

Among healthy contact lens wearers fitted with the same type of contact lens, a significant difference was observed in the quantity of proteins adsorbed on the lens with the use of Clens 100, as compared with the use of either Blink-N-Clean or no product at all. This difference does not seem to have had an impact because clinical signs and symptoms did not vary over the course of the study.

Effect of Artificial Tears on Visual Performance in Subjects With Dry Eye

PURPOSE

Disruption of the anterior refracting surface of the eye (i.e., the tear layer) reduces visual performance. Tear layer breakup occurs soon after a blink in contact lens wearers and patients with dry eye. This study determined whether artificial tears stabilize the tear film and improve visual performance in contact lens wearers who also exhibit a dry eye.

METHODS

Five subjects with mild to moderate dry eye (probably as a result of an evaporative dry eye) during spectacle and contact lens wear were fitted with a Focus Night & Day hydrogel lens for this study. A temporal, two-alternative, forced-choice paradigm was used to measure contrast sensitivity. The stimuli were vertically oriented sine wave gratings (between 0.5 and 14 cpd) presented for 16.67 msec. The stimuli were presented at two different times after blink detection: 2 sec after blink detection (i.e., before tear layer breakup) or 4 sec after tear film breakup. Four conditions were investigated at 4 sec after tear layer breakup: 1) without artificial tears added, 2) with Clerz2 (Alcon, Fort Worth, TX) instilled, 3) with Sensitive Eyes (Bausch & Lomb, Rochester, NY), and 4) with GenTeal (Novartis, Basel, Switzerland) applied. The artificial tears were instilled at 10-min intervals during the data collection. The short-term visual effects of drop instillation were also investigated by continually monitoring contrast sensitivity for a 14-cpd grating after a single-drop administration.

RESULTS

High spatial frequency contrast sensitivity and visual acuity were found to be reduced after tear film breakup in the absence of supplementation with artificial tears. For the group data (and four of five subjects), the instillation of Sensitive Eyes improved the contrast sensitivity and visual acuity to the level attained before tear breakup, thus prolonging visual performance. Clerz2 and GenTeal did not produce any enhancement in visual performance. A short-term decrease in contrast sensitivity was also observed with a single administration of Clerz2 and GenTeal.

CONCLUSIONS

This study indicates that there was a benefit of Bausch & Lomb Sensitive Eyes tear supplementation on visual performance in subjects with an evaporative dry eye. This may be the result of 1) aqueous supplementation in these subjects and/or 2) the minimal tear layer disruption found with Sensitive Eyes drop administration. The results suggest that practitioners need to identify those patients who can benefit from the use of appropriate artificial tear supplements.

Wavefront technology: Past, present and future

After outlining what is meant by wavefront aberration, the history of the field of wavefront technology is sketched and methods for measuring ocular wavefront aberration are briefly described. The variations in aberration of the normal eye with the individual and their pupil size, accommodation and age are summarised. Potential contact lens applications are outlined, including the design and on-eye performance of single-vision lenses, lenses for presbyopes and keratoconics, orthokeratology, tear film studies, and the design and performance of customised contact lenses intended to minimise residual lens-eye wavefront error.