title: Retinal safety of near-infrared lasers in cataract surgery.
abstract: Femtosecond lasers have added unprecedented precision and reproducibility to cataract surgery. However, retinal safety limits for the near-infrared lasers employed in surgery are not well quantified. We determined retinal injury thresholds for scanning patterns while considering the effects of reduced blood perfusion from rising intraocular pressure and retinal protection from light scattering on bubbles and tissue fragments produced by laser cutting. We measured retinal damage thresholds of a stationary, 1030-nm, continuous-wave laser with 2.6-mm retinal spot size for 10- and 100-s exposures in rabbits to be 1.35 W (1.26 to 1.42) and 0.78 W (0.73 to 0.83), respectively, and 1.08 W (0.96 to 1.11) and 0.36 W (0.33 to 0.41) when retinal perfusion is blocked. These thresholds were input into a computational model of ocular heating to calculate damage threshold temperatures. By requiring the tissue temperature to remain below the damage threshold temperatures determined in stationary beam experiments, one can calculate conservative damage thresholds for cataract surgery patterns. Light scattering on microbubbles and tissue fragments decreased the transmitted power by 88% within a 12 deg angle, adding a significant margin for retinal safety. These results can be used for assessment of the maximum permissible exposure during laser cataract surgery under various assumptions of blood perfusion, treatment duration, and scanning patterns.
authors.affiliation: Stanford University, Department of Applied Physics, 452 Lomita Mall, Stanford, California 94305, USA. jywang2@stanford.edu
authors.forename: Jenny
authors.initials: J
authors.lastname: Wang
authors.forename: Christopher
authors.initials: C
authors.lastname: Sramek
authors.forename: Yannis M
authors.initials: YM
authors.lastname: Paulus
authors.forename: Daniel
authors.initials: D
authors.lastname: Lavinsky
authors.forename: Georg
authors.initials: G
authors.lastname: Schuele
authors.forename: Dan
authors.initials: D
authors.lastname: Anderson
authors.forename: David
authors.initials: D
authors.lastname: Dewey
authors.forename: Daniel
authors.initials: D
authors.lastname: Palanker
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000528:radiation effects; D002387:Cataract Extraction / Q000009:adverse effects*; D004307:Dose-Response Relationship, Radiation; D005131:Eye Injuries / Q000209:etiology / Q000517:prevention & control*; D007259:Infrared Rays; D053685:Laser Therapy / Q000009:adverse effects* / Q000379:methods*; D008452:Maximum Allowable Concentration; D011817:Rabbits; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D012160:Retina / Q000293:injuries / Q000503:physiopathology* / Q000528:radiation effects*