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Yue Shi, Jason D Marsack, Anita Ticak, Darren Eugene Koenig, Raymond A Applegate, Visual Optics Institute; Modeling scleral contact lens stabilization to assess efficacy of full magnitude 2nd to 5th radial order wavefront guided corrections in keratoconus. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2130.
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© ARVO (1962-2015); The Authors (2016-present)
Misalignment of a full magnitude wavefront guided scleral contact lens correction with respect to the underlying wavefront error can result in image quality worse than no correction. It is assumed that the correction patch can be put on the lens to account for any mean translation and rotation errors. The purpose of this study was to model optical performance of an 18.2 mm diameter scleral contact lens with toric peripheral curves and to assess whether the lens provides adequate registration precision to implement a full magnitude 2nd to 5th radial order wavefront guided correction without inducing significant change in visual acuity (< 1 line).
Six normal eyes (3 subjects) and 2 keratoconic eyes (1 subject) were fit with scleral contact lenses using standard clinical procedure. After 1 hour of settling time, the position of the center of the contact lens with respect to the center of the pupil was recoded at 1 Hz for 7 seconds every 20 minutes for 1 hour. There was no significant difference between the registration errors of the 6 normal eyes and the 2 keratoconic eyes. Using the average location in each of the 7 second sampling period, we modeled the change in the visual image quality metric log visual Strehl (logVSX) for the wavefront error of 5 keratoconic eyes wearing a full magnitude 2nd to 5th order correction over a 4mm pupil. The change in visual acuity was predicted based on the difference in logVSX from the best logVSX for each eye (Ravikumar, et al 2012; Shi, et al 2013).
For all 5 keratoconic eyes modeled, all of the registration error induced a predicted acuity loss of less than one line. The average predicted letters lost for each of the 5 eyes was 3.38±0.80, 3.68±0.63, 3.63±0.42, 2.87±1.28, 2.81±0.94, respectively.
Modeling suggests that 18.2 mm contact lenses with peripheral toric stabilization provide adequate registration precision for full magnitude 2nd to 5th radial order wavefront guided correction in eyes with keratoconus, assuming the lens design can be accurately aligned and remain aligned with the underlying wavefront error of the eye over long periods of time.
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