Enhanced accommodation and expanded depth-of-focus in presbyopic scleral implant patients: objective correlates for improved near visual acuity

Session Details

Session Title: Presbyopic Corrections

Session Date/Time: Monday 15/09/2014 | 16:30-18:30

Paper Time: 18:08

Venue: Boulevard F (Level 1)

First Author: : L.Baitch USA

Co Author(s): :    D. Schanzlin   D. Iskander           

Abstract Details

Purpose:

To establish objective optical correlates to long-term post-operative near visual acuity improvements, which have been observed in Refocus scleral implant surgery patients.

Setting:

Clinical practice/ Clinical research trial

Methods:

COAS® Dynamic Stimulus Wavefront Aberrometry was performed pre-operatively, and at three-month intervals over an 18-month post-operative period, on nine presbyopic study patients (MRSE -0.75D to +1.00D, Astig ≤1.00D) ages 50-60 years. Subjects viewed an accommodative target through a dichoptic periscope. Optical wavefronts were recorded sequentially at 7.5 FPS in a 10-second time-series as the stimulus target alternated from far to near. Artifact-filtered responses were analyzed using Zernike mode computation up to the 6th Zernike radial order. Refractive power components, depth-of-focus (DoF), visual Strehl ratio-based visual acuity estimates and other salient parameters were also computed as time-series. Correlational analysis was performed between all measured parameters. Far and near visual acuity and refractions were monitored throughout the study on all subjects.

Results:

While MRSE and distance visual acuity remained unchanged throughout the post-operative period, mean distance-corrected near visual acuity (DCNVA) improved from logMAR 0.6 (20/80) to logMAR 0.21 (20/32); mean uncorrected near visual acuity (UCNVA) improved from logMAR 0.7 (20/100) to logMAR 0.25 (20/35). Optical wavefront data were reliably obtained for all subjects. Wavefront-based predicted visual acuity showed high correlation with published earlier regression results between wavefront higher-order RMS and image quality metrics. Spherical accommodative shift, as determined by M- and Z20- modes, increased in magnitude relative to pre-operative values. More significantly, dynamic COAS time-series analysis showed substantial changes over the post-operative duration in expansion of DoF (as calculated at the 50% cut-off of the through-focus visual Strehl optical transfer function (VSOTF)), and increase of negative spherical aberration with accommodative effort.

Conclusions:

Near visual acuity improvements after scleral implant surgery appear to be related to substantial changes in higher-order wavefront structure (primarily spherical aberration), expanded depth-of-focus, and a partial restoration of the spherical accommodative shift lost to presbyopia. This small prospective cohort of scleral implant study patients show changes in objectively-measured pre- vs post-op optical behavior, which are dynamic in nature, and whose metrics parallel observed near visual acuity improvements.

Financial Interest:

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