Blinking Reflex Changes After Lasik And Prk And Its Influence In Optical Quality.

The blinking reflex relies on the input from the corneal surface. Corneal LASER ablation to correct refractive errors is associated with corneal hypoesthesia. Our purpose was to analyze changes in blinking dynamics induced by two different techniques of laser vision correction (femtosecond laser-assisted laser in situ keratomileusis – LASIK - and alcohol-assisted photorefractive keratectomy - PRK) and its repercussions in optical quality.

Department of Ophthalmology, Centro Hospitalar Universitário do Porto, Portugal.

This study included 64 eyes in the LASIK group and 28 eyes in the PRK group, all treated for myopia and/or myopic astigmatism. A complete evaluation was performed before and 1 month, 3 months and 6 months after surgery. Blinking quality (BQ, %) was recorded automatically with IDRA® (SBM Sistemi) that considered the blinking frequency and count of full and partial blinks. Optical scatter index (OSI) was calculated with HD Analyzer® (Visiometrics). Non-invasive tear break-up time, lipid layer thickness, meibography, tear meniscus height, osmolarity and Schirmer test were also considered. Non-parametric statistical tests were used.

Age was not different between LASIK and PRK groups (p=0.849) and treated spherical equivalent was -2.80±1.33D and -2.30±0.93D, respectively (p=0.036). In the LASIK group, BQ was 71.0±20.8 at baseline, 70.9±21.6 at month 1 and decreased to 66.6±19.2 (p=0.040) at month 3 and 60.4±15.8 (p=0.003) at month 6. In the PRK group, BQ was 76.7±25.4 at baseline, 70.7±19.2 at month 1, 73.2±20.4 at month 3 and decreased to 52.0±23.7 (p=0.014) at month 6. In the LASIK group, baseline BQ was associated with OSI at month 6 (r=-0.414, p=0.023). There were no significant correlations or changes along the treatment in the other measurements.

The blinking reflex seems to be affected by laser vision correction and it may be a major player in pathogenesis of dry eye disease after corneal laser. A decrease in the blinking quality score was noticed 3 months after LASIK and 6 months after PRK. Earlier changes in the LASIK group may relate to the deeper obliteration of the corneal nerves during the flap creation and ablation. Additionally, the blinking score at baseline was associated positively with objective optical quality after the treatment. Better blinking may accelerate visual recovery after surgery and improve tear film-dependent optical quality. It may be amendable by patient education and should therefore be addressed in candidates for surgery.