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L. A. Engelbrecht, I. J. E. van der Meulen, L. Franssen, E. Zola, T. J. T. P. van den Berg; Straylight in Habitual Contact Lens Wearers. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4875.
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We measured straylight in rigid gas-permeable (RGP) and soft contact lens (cl) wearers to obtain an impression of the straylight increase in habitual cl wearers and to evaluate factors that may affect straylight such as the condition of the contact lens and corneal thickness.
Both eyes of 49 subjects (16 RGP and 33 soft cl wearers) were included. All subjects underwent straylight measurements using the C-Quant (Oculus GmbH), slitlamp examination with and without cl and pachymetry. The Efron Grading Scale was used for the assessment of cl complications. A Contac Lens Score (Clscore) was determined to assess cl condition. In 20 subjects additional straylight measurements and pachymetry were performed 1 and 3 hours after cl removal.
Mean straylight value, expressed as log(s), in the soft cl group was 0.94 while wearing the cl and 0.96 after cl removal. The majority of these measurements were within the 95% confidence limits of normal eyes but they were all slightly but significantly increased compared to the mean value (0.90) in the age-matched population. Mean straylight value in the RGP group was 1.31 while wearing cl and 1.08 after cl removal. In this group both values were strongly increased (p<0.01) compared to normal eyes. Cl removal drasticly decreased the straylight value but it was still 0.15 log(s) units elevated compared to the mean value (0.93) in the age-matched population. In both cl groups no significant change occurred in straylight and corneal thickness 1 and 3 hours after cl removal. Before cl removal only the RGP group showed a significant correlation between straylight and Clscores. After cl removal both groups showed a significant correlation between straylight and corneal thickness. In both groups no significant correlation existed between straylight measured without cl and Efron Grading Scales.
In our study, straylight was slightly increased in soft cl wearers and there was no change in straylight several hours after cl removal. However, in the RGP cl group we found highly significantly increased straylight values wearing cl and long-lasting elevated values after cl removal. We suggest that the first effect can be attributed to the lens itself. The second effect might be due to an effect of the hard cl on the corneal epithelium, which could lead to epithelial damage, influx of fluids into the corneal stroma and a minimal change of stromal thickness.
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