The Influence of Soft Contact Lens Materials on the Central, Para-Central and Peripheral Corneal Endothelium

Title: The influence of soft contact lens materials on the central, para-central and peripheral corneal endothelium prior to and following two weeks cessation of soft contact lens wear. Purpose: To examine the influence of a variety of soft contact lens (SCL) materials on the central, para-central and peripheral corneal endothelium measurements, prior to and following two weeks cessation of SCL wear. Methods: Endothelial measurements were taken using the CEM-530 (Nidek, Japan) specular microscope. Full-time SCL wearers (n = 31 eyes) were compared to a non-contact lens (NCL) control group (n = 28 eyes) of a similar age. Seven areas of the endothelium were analysed: centrally, para-centrally (0.6mm from centre) at 0°, 90°, 180°, 270° and the superior and inferior periphery (3.7mm from center). Parameters examined were endothelial cell density (ECD; cell/mm2), mean cell area (MCA; µ2), coefficient of variation (COV) and hexagonality (%). Results: Prior to SCL cessation, two-way ANOVA testing resulted in significant differences between silicone hydrogel (SiH) SCL materials for the COV at 0º, with generation 2 SiH wearers showing increased COV (27.67 ±3.78) compared to generation 3 SiH wearers (24.50 ±3.73, p=0.01). COV at the superior periphery was significantly lower in the NCL group (25.63 ±2.79) compared to the hydrogel group (29.92 ±6.22, p=0.02). The MCA in the inferior periphery was also significantly higher in the NCL group (346.92 ±36.75) compared to the hydrogel group (314.92 ±16.57, p=0.02). Following 14 days SCL cessation the differences in measurements taken between day 0 and day 14 were calculated and analysed, no statistically significant differences in stability of endothelial parameters were detected between NCL and SCL material groups (all p values \u3e0.05). Conclusion: SCL wear has an effect on para-central and peripheral corneal endothelial measurements in SCL wearers compared to NCL wearers, with largest significant differences seen between NCL and hydrogel SCL wearers. Following two weeks SCL cessation, there was relative stability of all endothelial measurements, regardless of which SCL material was worn prior to SCL cessation

The Effect of Two Weeks and Twenty-Four Hours Soft Contact Lens Cessation Times on Corneal Refractive Surgery Outcomes

Purpose To investigate the influence of previous soft contact lens (SCL) wear on outcomes of corneal refractive surgery (CRS). SCL wear can reduce accuracy of pre-operative corneal measurements and outcomes of CRS. Short SCL cessation times prior to CRS may be insufficient for resolution of SCL-induced corneal changes. It was hypothesised that the visual and refractive CRS outcomes would be worse in a SCL group compared to a non-contact lens (NCL) group and worse in a SCL group who ceased SCL wear for 24 hours when compared to those who ceased SCL wear for two weeks prior to examination and treatment. Method CRS outcomes for dominant eyes of two groups of previous full-time SCL wearing patients were analysed retrospectively; those who ceased SCL wear for two weeks (n = 45) and twenty four hours (n = 49) prior to examination and treatment. In both groups results were compared to a NCL control group (2 weeks NCL group n = 45; 24 hours NCL group n = 49). LASIK and PRK/LASEK one, three and six months post-operative outcomes were assessed for efficacy (unaided distance visual acuity (UDVA) and residual refractive error), predictability (number of eyes within ± 0.25D and ± 0.50D of desired refractive outcome) and safety. Results There was a trend towards superior CRS outcomes for efficacy, predictability and safety in the two weeks SCL cessation group compared to NCL group. These results were significantly better for LogMAR UDVA in the SCL group and were maintained to the six month post-operative visit (LASIK SCL: -0.10 ± 0.10, NCL: -0.06 ± 0.07, p = 0.03; LASEK/PRK SCL: -0.10 ± 0.08, NCL -0.04 ± 0.08, p = 0.03). These findings were reiterated in the 24 hours SCL cessation group where the trend towards superior CRS outcomes for efficacy, predictability and safety in the SCL group compared to the NCL group was continued. UDVA efficacy outcomes following LASEK/PRK were significantly better in the SCL group at the six month post-operative visit (SCL: -0.11 ± 0.03, NCL -0.04 ± 0.07, p = 0.03). Conclusion Previous SCL wear did not negatively impact on CRS outcomes. SCL cessation times of two weeks and twenty four hours did not result in negative outcomes compared to a NCL control group. While these results were statistically significant, the number of letters difference in UDVA between the SCL and NCL groups was low and so one cannot conclude that these results are clinically significant

The influence of soft contact lens wear and two weeks cessation of lens wear on corneal curvature.

INTRODUCTION: Accurate corneal measurements are crucial in corneal refractive surgery (CRS) to ensure successful outcomes. Soft contact lens (SCL) wear may result in changes to corneal curvature and structure. United States Food and Drug Administration (FDA) pre-operative guidelines recommend that prior to CRS, SCL wearers cease SCL wear for "at least two weeks before examination and treatment" [1]. Corneal curvature changes induced by SCL wear may take longer than two weeks to resolve. PURPOSE: To examine the effect of SCL wear on corneal curvature before and following two weeks SCL wear cessation. To explore the possible impact of different SCL materials and years of SCL wear. METHODS: Retrospective data analysis, between a group of SCL wearers (SCL: n=45); and a non-contact lens control group (NCL: n=45). Corneal curvature parameters were measured using the Pentacam (Oculus, Germany), before and following two weeks cessation of SCL wear. RESULTS: No significant differences in keratometry or Sagittal radius of curvature between SCL and NCL groups prior to or following SCL cessation. Tangential radius of curvature showed significant inferior steepening for the SCL group prior to SCL cessation (SCL vs. NCL; 7.77±0.30mm vs. 7.90±0.30mm; p=0.04). Following two weeks cessation of SCL wear this appeared to have resolved. CONCLUSIONS: Two weeks cessation of SCL wear appears sufficient for resolution of corneal curvature changes with modern SCL materials and years of SCL wear. However, further studies with longer lens deprivation periods are required to ensure stability for all SCL wearing patients