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Visual effect of the Stiles-Crawford peak location in patients with a small-aperture corneal inlay

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Session Details

Session Title: Intracorneal Inlays for Presbyopia

Session Date/Time: Tuesday 08/09/2015 | 16:00-18:00

Paper Time: 16:06

Venue: Main Auditorium

First Author: : P.Artal SPAIN

Co Author(s): :    P. Prieto   C. Robles   S. Manzanera   J. Holladay           

Abstract Details


Small aperture corneal inlays are successfully used to extend depth of focus in presbyopic patients. On the other hand, the Stiles-Crawford (SC) effect produces a change in the apparent brightness of rays entering the eye through different pupil positions. Although the SC peak is typically 0.33 mm nasally located to the pupil center, it can be significantly more decentered in some patients. The purpose of this study was to evaluate the impact of the location of the SC peak on the visual performance with a small aperture.


Laboratorio de Optica, Universidad de Murcia, Murcia, Spain


Optical and visual analysis was performed. Ray-tracing techniques were applied to the personalized biometric data from the eyes of 20 subjects. Through-focus image quality parameters were obtained for a pupil diameter of 1.6 mm with a Stiles-Crawford apodization both centered and laterally decentered. An instrument was developed to measure the location and shape of the Stiles-Crawford. It is based on registering the psychophysical responses to flickering stimulus when viewed through a small aperture at different locations within the pupil. In addition, estimations of the luminance reduction with a decentered SC and their impact in high contrast visual acuity were obtained.


The retinal image quality in eyes with a small aperture is minimally affected by the location of the Stiles-Crawford effect. However, the perceived luminance would be reduced as much as an equivalent optical density of 0.2 (64%) for a SC decentered of 2 mm. This will not affect high contrast visual acuity under photopic conditions (> 1 cd/m2). However, with a centered small aperture in mesopic conditions (0.01 to 1.0 cd/m2, a decentered (≥ 2 mm) SC peak can decrease high contrast visual acuity by approximately one line. A well centered small aperture within 1 mm or less of the SC peak would not affect high contrast visual acuity even in mesopic conditions.


The SC peak location has a negligible or limited impact on visual performance for most patients implanted with small aperture corneal inlays. However, in those cases with largely decentered SC (≥ 2 mm) a reduction of mesopic high contrast visual acuity could be expected.

Financial Interest:

One of the authors receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented

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