Influence of spatial and temporal spot distribution on the ocular surface quality and maximum ablation depth after photoablation with a 1050 Hz excimer laser system.
OBJECTIVE
To investigate the effect of temporal and spatial distributions of laser spots (scan sequences) on the corneal surface quality after ablation and the maximum ablation of a given refractive correction after photoablation with a high-repetition-rate scanning-spot laser.


METHODS
IROC AG, Zurich, Switzerland, and WaveLight AG, Erlangen, Germany.


METHODS
Bovine corneas and poly(methyl methacrylate) (PMMA) plates were photoablated using a 1050 Hz excimer laser prototype for corneal laser surgery. Four temporal and spatial spot distributions (scan sequences) with different temporal overlapping factors were created for 3 myopic, 3 hyperopic, and 3 phototherapeutic keratectomy ablation profiles. Surface quality and maximum ablation depth were measured using a surface profiling system.


RESULTS
The surface quality factor increased (rough surfaces) as the amount of temporal overlapping in the scan sequence and the amount of correction increased. The rise in surface quality factor was less for bovine corneas than for PMMA. The scan sequence might cause systematic substructures at the surface of the ablated material depending on the overlapping factor. The maximum ablation varied within the scan sequence.


CONCLUSIONS
The temporal and spatial distribution of the laser spots (scan sequence) during a corneal laser procedure affected the surface quality and maximum ablation depth of the ablation profile. Corneal laser surgery could theoretically benefit from smaller spot sizes and higher repetition rates. The temporal and spatial spot distributions are relevant to achieving these aims.
Mrochen
Michael
M
Institute for Refractive and Ophthalmic Surgery (IROC), Zurich, Switzerland. Michael.mrochen@iroc.ch
Schelling
Urs
U
Wuellner
Christian
C
Donitzky
Christof
C
D000818:Animals; D002417:Cattle; D003315:Cornea / Q000473:pathology* / Q000601:surgery*; D006956:Hyperopia / Q000601:surgery; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008954:Models, Biological; D009216:Myopia / Q000601:surgery; D018903:Photorefractive Keratectomy; D012086:Reoperation; D013499:Surface Properties