How Blink Anomalies Can Contribute to Post-LASIK Neurotrophic Epitheliopathy.

: Post-LASIK (laser in situ keratomileusis) symptoms and signs of dry eye have multiple causes. For example, tear osmolarity and the concentration of inflammatory mediators can increase because of reduced aqueous production and increased evaporative loss as a result of lower blink rates and increased interblink intervals. The tear concentration of inflammatory mediators can also increase because of surgical trauma, wound healing, comorbid systemic and ocular diseases, and the use of punctal plugs. Studies that examine only mechanical sensitivity of the cornea cannot detect changes in chemical sensitivity, which can persist longer. Symptoms may be partly attributed to sensitization of the traumatized corneal or lid wiper sensory nerves by inflammatory mediators. Increased lid wiper sensitivity could increase awareness of blinks, especially if ocular surface lubricity is reduced. Incomplete blinks have been found to represent 10 to 22% of the total number of blinks. Loss of neural stimuli and lower blink rates increase the significance of incomplete blinks that approximately double related interblink intervals and tear evaporation. The most common location of post-LASIK epitheliopathy is the inferior area of the cornea, which is overexposed by incomplete blinks. The relevance of incomplete blinking to post-LASIK epitheliopathy is supported by the relative absence of this complication in the similarly neurotrophically disadvantaged upper corneal areas for which blink rates and other tear functions usually appear to be adequate to prevent epitheliopathy, which stains. Occupational or leisure-time activities such as computer use and reading, which have been found to reduce blink rates and blink completeness, appear to be significant risk factors for symptoms and signs of dry eye. Apart from reducing symptoms and signs of dry eye, prophylactic and post-LASIK blink exercises to reduce incomplete blink rates and associated overexposure of the ocular surface may also contribute to more accurate refractive outcomes through faster wound healing.