Mechanism for a Rare, Idiosyncratic Complication Following Hyperopic LASIK: Diurnal Shift in Refractive Error Due to Epithelial Thickness Profile Changes.

PURPOSE: Case series report of normal-appearing eyes after hyperopic LASIK exhibiting diurnal shift in refractive error found to correlate with diurnal shifts in epithelial thickness profile.

METHODS: Patients complaining of diurnal shift in vision during the course of the day with more hyperopia on waking and decreasing hyperopia in the evening in the absence of abnormal epithelial or slit-lamp findings were examined. Diurnal concomitant measurement of refraction, topography, and Artemis very high-frequency digital ultrasound scanning (VHFDU) (ArcScan Inc., Morrison, CO) epithelial thickness profile mapping was undertaken throughout the day. A full review of the clinical database revealed 8 eyes of 5 patients with such symptoms. The authors report the findings in 6 eyes of 4 patients with such symptoms.

RESULTS: Excimer ablation was performed with standard aspheric profiles of 7-mm (4 eyes) and 6.5-mm (2 eyes) optical zone, centered on the coaxially fixating nascent corneal vertex. The total spherical equivalent laser data entry (primary plus re-treatments) was between +3.22 and +8.33 diopters (D). Mean postoperative keratometry was between 41.2 and 48.35 D. One eye treated for spherical equivalent of +4.25 D spontaneously resolved and the remaining 5 eyes possessed increasing central epithelial thickness from morning to afternoon correlated with increased central corneal power and reduced hyperopia. This complication represented 0.3% of all hyperopic eyes treated within a similar refractive range.

CONCLUSIONS: This phenomenon of diurnal refractive instability in the absence of clinical slit-lamp findings has not been reported previously. The cause has been identified as being due to idiosyncratic diurnal epithelial thickness profile changes. Further study into predictors for this complication and reversal is underway. [J Refract Surg. 2016;32(6):364-371.].