Correlation of Temperature and Humidity to Incidence of LASIK Flap Striae in High-Volume Refractive Surgery Center
Narrative Responses:
Purpose
To correlate temperature and humidity to the monthly and seaonal incidence of flap striae after LASIK performed by experienced surgeons at a single center between June 2007 and April 2012
Methods
The data on all LASIK cases performed at the Shinagawa LASIK Center in Tokyo between June 2007 and April 2012 was reviewed and organized by month to determine the total, monthly and seasonal incidence of flap striae requiring realignment. Statistical analyses were then performed to determine any significant differences in incidence by month, season, and year. Using data from the Japan Meteorological Agency, average monthly humidities and temperatures for the same time were obtained and compared to monthly realignment rates. The relationships were tested with Pearson's Correlation Coefficient.
Results
A total of 614,340 eyes had LASIK with 5,244 developing flap striae requiring realignment for a cumulative incidence of 0.85%. The average monthly number of LASIK cases across all years ranged from 8,959 to 12,028, while that of flap striae ranged from 73.8 to 107. Averaged for all years, the monthly incidence ranged from 0.657% to 1.006%, with the lowest incidences in the summer months (June-August)(p<.05). Comparison of the average monthly humidity and temperatures to the average monthly incidence of striae from 2008 to 2011 revealed a strong inverse correlation for each (R = -.902, p<0.00004:R = -.888, p<0.00006).
Conclusion
The cumulative incidence of striae requiring realignment after LASIK in the largest reported, single practice series is 0.85%. The lower incidence during Summer months has not been previously reported. The strong inverse correlation with monthly/seasonal temperature and humidity suggests air moisture provides a protective effect in the early postoperative period.