Michael Lawless1,2, Gerard Sutton1, Colin Chan1, Chris Hodge1,3

Purpose: Preoperative dry eye represents a risk for sub-optimal results following cataract and corneal refractive surgery. Our aim was to highlight the characteristics and incidence of tear film abnormali- ties in a standard, real world, refractive surgery population.
Methods: 1150 patients undergoing screening for cataract and refractive surgery from October 2016 through to October 2017 were reviewed. Routine examination included visual acuity, refraction, dry eye testing including tear film osmolarity (TFO) and the Ocular Surface Disease Index (OSDI) questionnaire.
Results: Mean TFO was 300.42 11.28 mOsm/L with 80.0% of eyes <308 mOsm/L indicating normal tear-film homeostasis. Mean inter-eye TFO differ- ence was 8.7 8.4mOsm/L with 39.2% greater than 8 mOsm/L. TFO was positively correlated with age, inter-eye difference and spherical equivalent. TFO was correlated to subjective dry eye in a subset of OSDI patients. There was no correlation between TFO and time of day the assessment took place. Multivariate analysis indicated that age and contact lens wear were significant factors in determining tear osmolarity values (age P = 0.040 and adjusted r2 = 0.011, contact lens wear P = 0.006 and adjusted r2 = 0.017). Conclusions: Almost 40% of routine patients pre- senting for refractive surgery assessment exhibited abnormal tear film hyperosmolarity. These patients may or may not have dry eye symptoms as demon- strated on the OSDI questionnaire. Screening tear osmolarity testing in all patients, in a standardized manner, identifies those who require treatment to optimize the tear film prior to corneal laser surgery or prior to biometry for intraocular lens calculations.