Purpose: To clinically evaluate long-term users of two different contact lens care preservative systems and to investigate whether prolonged use is associated with an increase in the prevalence of dry eye.
Methods: Eighty-nine wearers of group IV hydrogel or silicone hydrogel lenses participated in this one-visit, investigator-masked study. Subjects were required to have consistently used a polyhexamethylene biguanide (PHMB) or polyquaternium-1 (PQT) based solution for 2 years. Consistent use was defined as 80% for the past 2 years and 100% for the past year. Clinical assessments included: average and comfortable wear time; overall and end-of-day comfort; signs of dryness, discomfort, burning or stinging, grittiness or scratchiness and visual changes; non-invasive and fluorescein break-up-time; pre-ocular tear film lipids, tear meniscus height, Schirmer and fluorescein clearance tests; limbal and bulbar hyperemia; palpebral roughness; corneal and conjunctival staining; lens front surface wetting; and lens film deposits.
Results: Significantly more grittiness or scratchiness was reported by subjects using a PHMB-containing system (67% vs. 44%; P = 0.02). Palpebral roughness and hyperemia were significantly greater in the PHMB group wearing group IV lenses (P = 0.01 and P = 0.05, respectively). Corneal staining was significantly higher in the PHMB users in all four peripheral sectors (P < 0.01). Nasal and temporal conjunctival staining was also significantly higher for users of PHMB-containing systems (P < 0.05). Front surface lens wettability was significantly better for group IV PQT users compared to PHMB users (P = 0.008), with 84% vs. 72%, respectively, with lenses graded by the investigator as having "good" or "excellent" wettability. Significantly higher levels of lens front surface film deposits were noted with PHMB users (P = 0.007), with 58% of group IV lenses treated with PHMB compared with 38% of group IV lenses treated with PQT showing some lens front surface film deposition. No significant differences between the two preservative system groups were noted for the range of dry eye evaluations nor the remaining clinical assessments.
Conclusions: Differences in both ocular and lens characteristic were observed between long-term users of two preservative systems used in many contact lens multi-purpose solutions. The findings from this study did not support the hypothesis that prolonged use of PHMB-containing solutions leads to dry eye. Additional studies including a larger sample size and perhaps longer use of the systems could help to further elucidate differences in clinical performance between systems.