The Impact of New Generation Aspherical Soft Contact Lenses on Quality of Vision: A Comparison with Spherical Contact Lenses and Spectacle Correction

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Anissa Doyle
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1 Deniz Oral, Maryo C. Kohen, Melda Yenerel, Ebru Gorgun, Sule Ziylan, Ferda Ciftci Yeditepe University Faculty of Medicine, Department of Ophthalmology, Istanbul Introduction The correction of higher order aberrations (HOA) along with spherocylindrical refractive errors to improve quality of vision has become an area of great interest within the last ten years. Among all HOAs, spherical aberration has the most profound effect on quality of vision 1. Therefore contact lens manufacturers started using aspherical technology in lens design for the correction of spherical aberration. The correction of positive spherical aberration that is inherently present in normal eyes with the application of aspherical contact lenses has the purported advantage of better visual quality with less halos and glare especially under low light conditions. Purpose In this study we have aimed to investigate whether aspherical contact lenses reduce ocular HOAs and improve visual acuity and contrast sensitivity (CS) compared to spherical soft contact lenses and spectacle correction.

2 Materials and Methods Thirty eyes of 15 patients aged between 19 and 40 (mean 28±7 years)withmyopiaand astigmatism less than 0.75D were included in this study. Visual acuity and contrast sensitivity at 4 different spatial frequencies (3,6,12,18 cycles/degree) under photopic and scotopic conditions were measured with manifest refraction spectacle correction. Higher order aberrations of each eye was then measured over a 5.5mm pupil with a wavefront analyser. Based on spherical equivalent refraction the eyes were first fitted with spherical contact lenses (Bausch and Lomb, Soflens 38) and then with new generation aspherical contact lenses (Bausch and Lomb, Purevision 2HD). Visual acuity, CS and HOA measurements were repeated with each type of contact lenses. Spectacle correction, spherical and aspherical contact lenses were then compared regarding their effect on visual parameters. Results The spherical equivalent refractions of 7 female and 8 male subjects were ranging between and -5.00D (mean -2.28±1.28D). Best corrected visual acuities with aspherical contact lenses were not significantly different than with spherical lenses and spectacle correction.

3 Total HOA, coma and trefoil values remained unchanged with both types of contact lenses. Aspherical contact lenses decreased spherical aberration significantly, whereas there was no change in spherical aberration with spherical lenses. Table 1 shows visual acuities and HOAs with different refractive corrections. Spectacles Spherical CL Asperical CL p value Visual Acuity (logmar) ± ± ± Higher Order Aberrations (µm) Total HOA 0.35 ± ± ± Coma 0.20 ± ± ± Trefoil 0.17 ± ± ± Spherical Aberration 0.05 ± ± ± 0.31 < 0.001* Table 1. Corrected visual acuities and HOAs

4 Contrast sensitivity scores with aspherical contact lenses were higher than spherical lenses and spectacle correction under both photopic and scotopic conditions. The contrast sensitivity with aspherical lenses was significantly higher than with spherical lenses at one frequency under photopic and at two frequency levels under scotopic conditions. Table 2 shows logarithmic values of contrast sensitivity scores. Photopic Frequency Spectacles Spherical CL Aspherical CL p value 3 cpd 1.74 ± ± ± cpd 1.89 ± ± ± cpd 1.58 ± ± ± cpd 1.18 ± ± ± * Scotopic 3 cpd 1.71 ± ± ± * 6 cpd 1.95 ± ± ± cpd 1.55 ± ± ± * 18 cpd 1.12 ± ± ± Table 2. Contrast sensitivity scores (log)

5 Conclusions In this study aspherical lenses reduced the existing positive spherical aberration and resulted in negative spherical aberration while the spherical aberration remained unchanged with spherical contact lenses. Visual acuity with aspherical lenses was not significantly different than spherical contact lenses and spectacle correction. Under both scotopic and photopic conditions the CS scores with aspherical lenses were higher than with spherical lenses and spectacles. At same tested frequencies the CS with aspherical lenses showed statistically significant improvement over spherical lenses but this was not a constant finding. Our study results are in accordance with previous similar studies reporting reduction in spherical aberration with aspherical contact lenses without significant change in visual acuity compared to spherical lenses 2-4. References 1) Applegate RA, Sarver EJ, Khemsara V. Are all aberrations equal? J Refract Surg. 2002; 18: S ) Lindskoog Pettersson A, Jarkö C, Alvin A, Unsbo P, Brautaset R. Spherical aberration in contact lens wear. Cont Lens Anterior Eye. 2008; 31: ) Efron S, Efron N, Morgan PB. Optical and visual performance of aspheric soft contact lenses. Optom Vis Sci. 2008; 85: ) Lindskoog Pettersson A, Mårtensson L, Salkic J, Unsbo P, Brautaset R. Spherical aberration in relation to visual performance in contact lens wear. Cont Lens Anterior Eye. 2011; 34:

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