Purpose: : It has been suggested that the natural lens provides some compensatory optical effect in the periphery. Therefore it is expected that when this lens is substituted by an intraocular lens (IOL) during cataract surgery, the quality of the peripheral optics would be modified. To better understand this situation, we compared the peripheral image quality of patients with a monofocal IOL implanted in one eye and still their natural pre-cataract lens in the fellow eye.
Methods: : We used a scanning peripheral wavefront sensor based on the Hartmann-Shack (HS) principle (Jaeken et al., Opt.Exp. 2011). The sensor operates in infrared light and measures the central 80° of the visual field along a horizontal meridian in 1.8 seconds. The path length between the eye and the first element of the HS-sensor is constant at all measured angles. A series of wavefront aberrations is obtained for each degree. Twelve patients with an age range between 65 to 81 years old were evaluated. They had one eye implanted with a monofocal IOL (different manufactures and models) while the fellow eye was un-operated and presented in all cases only minor signs of early cataract. From the HS-images recorded at each angle, Zernike coefficients were fitted using all data points then rescaled to a 3 mm pupil. The results of the phakic and pseudophakic eyes were compared using the mean spherical equivalent (M), oblique astigmatism (J0) and the higher order aberrations RMS (3rd and 4th order). The overall retinal image quality was examined by calculating the Strehl ratio. A one-way multivariate ANOVA test was used to investigate the statistical difference at each angle between the two eyes.
Results: : For the eyes implanted with IOLs, M in the periphery was only slightly more myopic than in the normal eyes for a selected number of angles. J0 increased much faster in the periphery for the pseudophakic eyes compared to the phakic eyes. The mean values were significantly different from 9° at the temporal retina and from 17° at the nasal retina. As an example, at 30°, the eyes implanted with IOLs presented on average 1.2 D of additional astigmatism. The overall degradation of the image quality in the periphery was dominated by J0 resulting in a poorer retinal image quality from 7° at the temporal retina and from 22° at the nasal retina for the pseudophakic eyes. The higher order aberrations were not significantly different between the two groups.
Conclusions: : Eyes implanted with a monofocal IOL present larger values of oblique astigmatism in the periphery as compare with normal older eyes. This degradation of the peripheral retinal image quality may have some possible impact on the reduction of the pseudophakic patient’s performance in common visual tasks.