Generation of Higher Order Aberrations with Soft Contact Lens by Excimer Laser Ablation

Although the human eye has a relatively simple optical system, it is not perfect. It has been well known that the human eye suffers from the wavefront aberration that includes both lower (defocus and astigmatism) and higher order aberrations. The lower order aberration has been effectively corrected with conventional ophthalmic lenses such as spectacles and contact lenses. However, it is more complicated to correct for the higher order aberrations. Ocular wavefront sensing technique [1] allows us to precisely understand optical quality of the eye by measuring the wave aberrations. It also makes it possible to correct the higher order aberration using advanced methods such as adaptive optics [2], laser refractive surgery [3] and customized optics [4]. Optical and psychophysical tests have demonstrated that correcting these aberrations significantly improves visual performance even in normal eyes. The visual benefit is even more substantial when correcting the aberration in eyes having abnormal corneal conditions such as keratoconus (abnormal cone shape cornea) and penetrating keratoplasty (corneal transplant). Adaptive optics is a powerful and noninvasive tool to achieve higher order correction in real time. However, it is an impractical method simply because of the size of the entire system. Although refractive surgery has been proven to be practical and effective to correct the aberration, it is a non-reversible surgical method and its availability is restricted by factors such as corneal thickness and the amount of the aberration. The interest in using customized optics to correct the aberration has been increased. This special optics includes phase plates, customized contact lenses and intraocular lenses (IOLs). Phase plate (spectacles capable of correcting the higher order aberration) has been proven to be an effective way to compensate for the static aberrations in the eye. This special optical component has an arbitrary surface profile created to correct the eye’s aberrations on a plate made of optical plastic. The successful correction of the higher order aberration resulted in significant visual improvement in both normal and abnormal eyes. However, we also found that decentration of the eye’s pupil due to changes in a gaze angle results in poor correction performance causing reduction of visual benefit. To overcome this limitation, customized soft contact lenses which follow most of the eyes’ movements was proposed as an alternative way to correct the aberration. This report presents the feasibility of generating the higher order aberration with soft contact lenses of which surface was ablated by an excimer laser. METHOD