pective Analysis of Risk Factors Associated With Contact Lens Induced Inflammatory Events During Continuous Wear

Michelle Flint BA, William Miller, OD, PhD, FAAO University of Houston, College of Optometry

PURPOSE:

Even though silicone hydrogel (SiHy) contact lenses have provided the corneal surface with exceptional oxygen levels, problems with corneal inflammation and infection have still been observed. One possible explanation for these complications may be tear stagnation under the contact lens due to insufficient tear exchange. The purpose of this study was to determine the tear exchange rate in seven different silicone hydrogel contact lens materials using an in vivo fluorophotometer on 15 patients when compared to a control hydrogel contact lens. In addition, the diurnal variation in tear exchange rate was also determined to assess the effects of any decrease in lens movement throughout the course of daytime wear.

METHODS:

Lens movement was determined using a calibrated scale attached to a biomicroscope. Corneal astigmatism and elevation was determined using the Orbscan topographer (B&L). Tear exchange rate was determined by instilling high molecular weight sodium fluorescein (FITC) onto the concave portion of the lens with subsequent application to the cornea. Diurnal variation was determined by looking at tear exchange rate at different times of the day. Slow tear exchange rate was ascertained using Kleidograph and Microsoft Excel.

RESULTS:

The slow decay rates were as follows: Lotrafilcon A (8.5%), Lotrafilcon (5.3%), Etafilcon (4.9%), Galyfilcon (3.6%), Senofilcon (3.5%), Comfilcon (2.5%), Balafilcon (1.8%), and Enfilcon (1.1%). Largest vertical movement was Lotrafilcon (.3mm). Smallest vertical movement was Senofilcon A (.1mm). Normal corneal astigmatism and elevations were observed.

CONCLUSIONS:

Lens movement and tear exchange rate were different between some SiHy contact lenses and the control hydrogel contact lens. The range of slow decay rate was 8.5% to 1.1%. Lens movement and slow decay rate showed a positive correlation resulting in a greater decay with increased movement. Results suggest that differences in individual SiHy lenses were exhibited due to the biophysical differences between lenses.

ADDITIONAL COMMENTS:

NEI training grant