Centre for Contact Lens Research

Purpose. This non-dispensing cross-over study was conducted to determine if lenses presoaked in Opti-Free RepleniSH (OFR) or ReNu MultiPlus (RMP) cause solution-induced corneal staining (SICS) and subsequent cell sloughing before the typical 2 h in vivo examination point. Methods. Study lenses (PureVision) were worn bilaterally by 13 participants for periods of 15, 30, 60, and 120 min using two different contralateral care regimen pairings. The lens worn on the test eye was soaked overnight in either OFR or RMP and the control eye in Clear Care (CC). After lens removal, corneal staining was rated on a scale of 0 (negligible) to 100 (severe) for four peripheral quadrants and the central region, and the differential global staining score was calculated by subtracting baseline staining scores. Following the staining assessment, corneal cells were collected from the ocular surface using a non-contact irrigation system to determine ocular cell shedding rates. Results. Differential global staining score with OFR was greater than CC with the differences being statistically significant at 30 and 60 min (p 0.05). Conclusions. SICS occurred earlier but to a significantly lower degree when PureVision lenses were presoaked in OFR compared with RMP, while lenses presoaked in CC did not cause SICS. Ocular surface cell shedding after lens removal was not impacted by lens wear durations of ≤2 h. © 2012 American Academy of Optometry.

Purpose: To determine distribution of central corneal swelling (CCS) across subjects after 8 hr of sleep in eyes wearing silicone hydrogel lenses with various oxygen transmissibility (Dk/t) values and in eyes without lenses. Methods: Twenty-nine neophytes wore lotrafilcon A (Dk, 140), balafilcon A (Dk, 91), galyfilcon A (Dk, 60), and senofilcon A (Dk, 103) lenses in powers -3.00, -10.00, and +6.00 diopters on separate nights, in random order, and on 1 eye only. The contralateral eye (no lens) served as the control. Central corneal thickness was measured using a digital optical pachometer before lens insertion and immediately after lens removal on waking. Results: The average difference between the mean (7%) and the median (6.8%) CCS of all lenses was only 0.2%, suggesting a normal distribution. There was no correlation between the mean and the range of the CCS (r=0.058, P=0.766). Normal CCS distributions were also found with each lens-wearing eye and the control eye (P>0.20 for all). There was a significant correlation between lens-wearing eye and control eye (r=0.895, P<0.001) and between lotrafilcon A and each of the other 3 lenses for mean CCS across the study participants (P<0.001 for all). Conclusions: Distribution of corneal swelling in both lens-wearing eye and control eye followed a normal curve. An individual's corneal swelling response seems to be independent of lens type. © 2011 Lippincott Williams & Wilkins.

PURPOSE. To compare central corneal swelling after 8 hours of sleep in eyes wearing 2 different silicone hydrogel lenses with high oxygen transmissibility. METHODS. Twenty neophyte subjects were randomly assigned to wear a comfilcon A lens (CooperVision Inc) in one eye and a lotrafilcon A lens (CIBA Vision) in the contralateral eye for an 8-hour overnight period. The study was repeated with another 20 neophyte subjects wearing comfilcon A in one eye only and no lens in the contralateral control eye. Central corneal thickness was measured with optical pachometry before lens insertion, immediately after lens removal on waking, at 20 and 40 minutes, 1 hour, 2 hours and 3 hours. RESULTS. There was no significant difference between the amount of overnight central corneal swelling induced by the 2 lenses (4.1% ± 1.9% with comfilcon A vs. 4.0% ± 1.7% with lotrafilcon A; P>0.05). The swelling of the comfilcon A lens-wearing eyes was significantly higher than that found in the non-lens-wearing contralateral eyes (4.5% ± 2.1% vs. 3.0% ± 1.7%; P<0.05). CONCLUSIONS. The same amount of overnight corneal swelling was induced by the 2 study lenses. The higher overnight swelling observed with the comfilcon A lenses compared to the non-lens-wearing eyes is similar to that reported in the literature for studies using lotrafilcon A lenses. © 2006 Lippincott Williams & Wilkins, Inc.

PURPOSE: The purpose of this study was to develop a simple method for cross-calibrating instruments that measure corneal thickness. METHODS: Fourteen rigid lenses of different thicknesses were manufactured using a material with refractive index of 1.376. Center thickness of the lenses (CT) was measured using a computerized optical pachometer (OP), two optical coherence tomographers (OCTs), and a confocal microscope (CM). Accuracy of measurements was compared between the four instruments. RESULTS: Before calibrating the machines, there was a significant effect of the measurement device (p < 0.05). The differences between instruments were eliminated (p > 0.05) after applying calibration equations for each device. In addition, after each instrument was calibrated with lenses of 1.376 refractive index, there was no significant difference (p > 0.05) between measured values of lens center thickness by OP, each OCT, CM, and the physical center thickness of the lenses. CONCLUSIONS: Using calibration lenses with the same refractive index as the cornea (1.376) allows rapid and simple calibration of the pachometers so that corneal thickness measurements from different devices can be used interchangeably.

PURPOSE. Silicone hydrogel (SiH) lenses offer many physiological advantages for daily wear (DW) in addition to the continuous-wear modality for which they were originally developed. The purpose of this study was to investigate the clinical performance and physiological responses in a group of successful long-term wearers of conventional hydrogel lenses when refitted with DW SiH contact lenses. METHODS. Eighty-seven successful soft lens wearers (8.4 ± 4.7 years of prior lens wear) participated in this study. Bulbar and limbal hyperemia were subjectively graded and digitally photographed for subsequent masked objective evaluation. Subjective symptoms were scored using visual analog scales. In addition, refractive error, corneal curvature, and corneal thickness were measured. All subjects were refitted with Focus Night & Day (lotrafilcon A) SiH lenses; however, to reduce the potential for bias, they were informed that they were being randomly assigned to wear either low oxygen permeability (Dk) lenses or high Dk SiH lenses and were "masked" as to their lens assignment. Subjects returned after 1 week, 1 month, and 2 months of DW, at which time all gradings, photographs, and measurements were repeated. End-of-day subjective symptoms were also graded periodically during the study. RESULTS. Ninety-three percent of subjects were successfully refitted. Both objective and subjective evaluations showed that bulbar and limbal hyperemia decreased significantly in all quadrants during the study (p < 0.001), particularly for those subjects with greater baseline hyperemia (p < 0.001). Subjects reported a concurrent reduction in end-of-day dryness and improved end-of-day comfort compared with their habitual lenses (p < 0.001). No significant changes in refractive error, tarsal papillary response, corneal curvature, or corneal thickness were found during the study. CONCLUSIONS. Hyperemia in contact lens wearers may be attributed to a number of factors, including hypoxia. Refitting existing low Dk lens wearers with SiH lenses on a DW basis can result in a decrease in hyperemia, which may be significant for some subjects and also results in improvements in symptoms of dryness and discomfort. © 2006 American Academy of Optometry.

Purpose. The purpose of this study was to measure central and topographical corneal swelling in response to contact lens wear and eye closure, to determine whether the swelling induced by soft and polymethyl methacrylate (PMMA) lenses is different, and to determine whether the anterior and/or posterior corneal shape alters with corneal swelling. Methods. An Orbscan II corneal topographer was used to measure corneal swelling and the shape of the anterior and posterior corneal surfaces of 16 neophytes before and after wearing soft and PMMA contact lenses with near-zero oxygen transmissibility. The lens-wearing eye was patched for 3 h. Results. The mean 15.1% ± 3.8% (±SD) central corneal swelling with soft lenses was significantly > 12.6% ± 4.1% with PMMA lenses. Topographical corneal swelling was significantly greater with soft vs. PMMA lenses. However, the difference between central and peripheral corneal swelling was much greater with PMMA lenses. With both lenses, the cornea swelled significantly more in the center than the periphery. The anterior best-fit sphere radius remained unchanged in response to soft lenses (0.00 ± 0.04 mm) and steepened slightly but significantly with PMMA lenses (-0.04. ± 0.05 mm). The posterior best-fit sphere radius flattened significantly with both lenses (0.12 ± 0.07 mm with soft and 0.14 ± 0.08 mm with PMMA lenses). Conclusions. Corneal swelling (greater centrally than peripherally) flattens the posterior surface of the cornea and is independent of lens type. Although the anterior best-fit sphere radius steepened with PMMA, the magnitude is probably clinically unimportant. Both lens types produced greater central vs. peripheral corneal swelling. However, the soft lens induced significantly greater overall swelling than PMMA. Because their oxygen transmission was the same, these results suggest that there is lateral diffusion of oxygen from the peripheral area of the cornea (that is not covered by the lens) toward the center.

E-abstract 85077

E-abstract 85076

E-Abstract 060095

E-Abstract 060066

E-Abstract 060069

E-abstract 050083