title: Surface ablation with iris recognition and dynamic rotational eye tracking-based tissue saving treatment with the Technolas 217z excimer laser.
abstract: OBJECTIVE
  To evaluate the visual and refractive outcomes and expected benefits of Tissue Saving Treatment algorithm-guided surface ablation with iris recognition and dynamic rotational eye tracking.
  
  
  METHODS
  This prospective, interventional case series comprised 122 eyes (70 patients). Pre- and postoperative assessment included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, and higher order aberrations. All patients underwent Tissue Saving Treatment algorithm-guided surface ablation with iris recognition and dynamic rotational eye tracking using the Technolas 217z 100-Hz excimer platform (Technolas Perfect Vision GmbH). Follow-up was performed up to 6 months postoperatively. Theoretical benefit analysis was performed to evaluate the algorithm's outcomes compared to others.
  
  
  RESULTS
  Preoperative spherocylindrical power was sphere -3.62 ± 1.60 diopters (D) (range: 0 to -6.75 D), cylinder -1.15 ± 1.00 D (range: 0 to -3.50 D), and spherical equivalent -4.19 ± 1.60 D (range: -7.75 to -2.00 D). At 6 months, 91% (111/122) of eyes were within ± 0.50 D of attempted correction. Postoperative UDVA was comparable to preoperative CDVA at 1 month (P=.47) and progressively improved at 6 months (P=.004). Two eyes lost one line of CDVA at 6 months. Theoretical benefit analysis revealed that of 101 eyes with astigmatism, 29 would have had cyclotorsion-induced astigmatism of ≥ 10% if iris recognition and dynamic rotational eye tracking were not used. Furthermore, the mean percentage decrease in maximum depth of ablation by using the Tissue Saving Treatment was 11.8 ± 2.9% over Aspheric, 17.8 ± 6.2% over Personalized, and 18.2 ± 2.8% over Planoscan algorithms.
  
  
  CONCLUSIONS
  Tissue saving surface ablation with iris recognition and dynamic rotational eye tracking was safe and effective in this series of eyes.
authors.affiliation: Dr Agarwal's Eye Hospital and Eye Research Centre, Chennai, India.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Prakash
authors.forename: Amar
authors.initials: A
authors.lastname: Agarwal
authors.forename: Dhivya Ashok
authors.initials: DA
authors.lastname: Kumar
authors.forename: Soosan
authors.initials: S
authors.lastname: Jacob
authors.forename: Athiya
authors.initials: A
authors.lastname: Agarwal
authors.forename: Amrita
authors.initials: A
authors.lastname: Maity
mesh_terms: D057128:Aberrometry; D000293:Adolescent; D000328:Adult; D000465:Algorithms; D003315:Cornea / Q000601:surgery*; D005260:Female; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D009216:Myopia / Q000601:surgery*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D012399:Rotation; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult