Abstract
Abstract: :
Purpose: To assess the role of aqueous tear evaporation at the time of and following LASIKMethods: Three hundred fifty eyes of both normals and patients with apparent aqueous deficient dry eye were assessed using an evaporometer to determine aqueous tear evaporation at humidities between 25% and 35% vs. 35% and 45% relative humidity under environmental conditions similar to those in a LASIK center. Additionally 25 patients with aqueous deficient dry eyes were assessed prior to and after the installation of one drop of a commercial preparation containing HP Guar.; SystaneTM, in circumstances comparable to a postoperative setting.Results: A decrease in humidity from an average of 40% to 30%, i.e., a 10% decrease in relative humidity, resulted in an aqueous tear evaporation increase of 40%. Aqueous tear evaporation decreased by 15% after the installation of one drop of SystaneTM containing HP Guar. Conclusions: At the time of LASIK relative humidity is critical and significantly effects the evaporation of water from the surface of the eye and potentially the amount of laser tissue removal. Therefore, humidity must be carefully controlled intra–operatively during the LASIK procedure to optimize predictability of results. A commercial preparation, SystaneTM, containing HP Guar significantly decreases aqueous tear evaporation in a setting comparable to that typical for postoperative LASIK eyes.
Keywords: aqueous • refractive surgery: LASIK • cornea: tears/tear film/dry eye