Risk factors for corneal infiltrative events during continuous wear of silicone hydrogel contact lenses

Abstract

Purpose: This study determined which microbiologic, clinical, demographic, and behavioral factors are associated with corneal infiltrative events (CIEs) during continuous wear of silicone hydrogel (SH) contact lenses.

Methods: Subjects (n = 205) were fitted with lotrafilcon A lenses for continuous wear and observed for 1 year. The main exposures of interest were corneal staining and bacterial lens contamination. Kaplan-Meier (KM) plots were used to estimate the cumulative unadjusted probability of remaining CIE free, and Cox proportional hazards regression was used to model the hazard of having a CIE, as a function of key predictor variables.

Results: The KM-unadjusted cumulative probability of remaining CIE free was 73.3%. Approximately 53% of subjects had repeated episodes of corneal staining (mild or greater), and 11.3% had repeated episodes of moderate or greater corneal staining. Corneal staining was not associated with the development of a CIE. The frequency of substantial bacterial bioburden on worn lenses at the time of a CIE was 64.7%, compared with only 12.2% during uncomplicated wear. The presence of substantial lens bacterial bioburden was associated with the development of a CIE (adjusted hazards ratio [HR], 8.66; 95% confidence interval [CI], 2.88-26.01). Smoking was also associated with a CIE (adjusted HR, 4.13; 95% CI, 1.27-13.45).

Conclusions: Corneal staining is common during continuous wear of SH lenses, but it is not associated with the development of a CIE. Smoking and substantial lens bacterial bioburden pose prominent risks of a CIE. In this study, more than 70% of the total risk of CIE in those with substantial lens bioburden is attributable to this exposure. (ClinicalTrials.gov number, NCT00727402).

Figure 1.

Example of grading of photographic corneal staining. Each of the five corneal zones was graded for staining type, surface area, and density. In this example, zone 5 was graded by the masked readers as a macropunctate stain, with a 31% to 45% surface area, and moderate density. On this visit, this eye was classified with overall moderate stain. This subject ended the study event free.

Figure 2.

Flow chart of subject retention and discontinuation in the LASH Study.

Figure 3.

Unadjusted cumulative probability of remaining CIE free stratified by (A) the presence or absence of at least one episode of moderate corneal staining or greater and (B) the presence or absence of repeated episodes of mild corneal staining or greater.

Figure 4.

The unadjusted cumulative probability of remaining CIE free, stratified by the presence or absence of substantial bioburden on study lenses.

Figure 5.

The unadjusted cumulative probability of remaining CIE free, stratified by the presence or absence of smoking.