A new rare phenomenon following hyperopic LASIK: diurnal fluctuations in refractive error due to diurnal epithelial thickness profile fluctuations

Session Details

Session Title: Hyperopic corrections

Session Date/Time: Sunday 14/09/2014 | 16:30-18:00

Paper Time: 16:57

Venue: Boulevard B

First Author: : G.Carp UK

Co Author(s): :    D. Reinstein   M. Gobbe   T. Archer        

Abstract Details

Purpose:

To report a case series of eyes exhibiting diurnal fluctuations in refractive error following hyperopic LASIK proven to be due to diurnal epithelial thickness profile shifts.

Setting:

London Vision Clinic, London, UK

Methods:

Retrospective analysis of 7 eyes treated with hyperopic LASIK using the MEL80 at the London Vision Clinic between January 2005 and August 2010. All patients were over the age of 48. All standard non-wavefront-guided ablations retained the nascent corneal vertex position and angle-kappa by ablation centration on the corneal vertex (CV). The total summated spherical equivalent (SEQ) laser data entry in each eye (including enhancements) was between +3.94D and +6.75D. A total of 1679 eyes were treated with SEQ laser data entry above +3.75D with the MEL80 between May 2003 and Jan 2014. The first bilateral case identified had undergone primary LASIK for +6.75 in September 2009, and the mechanism was confirmed in August 2010. A full review of our clinical database was undertaken to find other similar cases. One eye of a bilaterally treated low-hyperopic patient was identified from several years previously (2005) and two further patients treated December 2009 and August 2010 were identified and returned for detailed examination. For the 3 persistent bilateral cases, special examinations were repeated diurnally: concomitantly measuring manifest refraction, corneal topography and Artemis VHF digital ultrasound scanning (VHFDU) epithelial thickness profile mapping.

Results:

The 6 eyes with persistent diurnal fluctuations represented 0.36% of all hyperopic eyes treated at our facility within the same refractive range. Mean postop keratometry was between 41.2D and no higher than 48.0 D and 3 of the eyes were flatter than 43.5D. The 2005 treated +3.50D hyperopic eye only experienced refractive fluctuations following an enhancement procedure of +1.50D and was found to have significant central epithelial thinning (28 μm) as demonstrated by VHFDU despite the presence of flat (41.2 D) keratometry; this case resolved over a period of 6 months spontaneously using only intensive ocular lubricants with a recovery of the epithelial thickness minimum to 34 microns. Diurnal changes in manifest refraction correlated to diurnal changes in topography and epithelial thickness; increasing central epithelial thickness from morning to afternoon correlated with increased vertex/central corneal power (within the central 2mm zone) and reduced levels of hyperopia or myopisation. Diurnal corneal keratometry measurement changes did not correlate to the observed refractive shifts.

Conclusions:

To our knowledge this diurnal phenomenon has not been reported previously. The observed phenomenon of persistent diurnal fluctuations in refraction was identified as being due to diurnal fluctuations in epithelial thickness profile. Given the known behavior of epithelial compensation we postulate that this is due to an unusual combination of the altered rate of change of curvature of the stromal surface, eyelid tension and nascent epithelial health.

Financial Interest:

One or more of the authors... has significant investment interest in a company producing, developing or supplying product or procedure presented, 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