Selective zonal ablations with excimer laser for correction of irregular astigmatism induced by refractive surgery.
OBJECTIVE
To demonstrate the safety and efficacy of selective zonal ablations with excimer laser for the correction of irregular astigmatism induced by refractive surgery.


METHODS
Thirty-one eyes of 26 patients. Retrospective and noncomparative case series.


METHODS
The authors reviewed the medical results of the two series of consecutive cases of irregular astigmatism induced by refractive surgery. One group showed a topography map with a defined pattern: decentered ablation, decentered steep central island, central irregularity, and peripheral irregularity. The other group showed an irregular astigmatism without defined pattern. Selective zonal ablation was performed with a broad-beam excimer laser. Laser ablations were adjusted according to the Munnerlyn formula. A phototherapeutic keratectomy (PTK) mode was used in all cases without using viscous masking solution.


METHODS
Uncorrected visual acuity, best spectacle-corrected visual acuity (BCVA), and Holladay diagnostic summary (Eye Sys 2.000) were considered before and after surgery to obtain the qualitative and quantitative characteristics of the visual acuity and corneal topography. The corneal uniformity index (CUI) was used to evaluate the corneal surface changes induced by the selective zonal ablations in the correction of irregular astigmatism. It proved to be a useful tool in the understanding of astigmatic changes when it is not possible to apply the vector analysis.


RESULTS
In group 1, the irregular astigmatism was significantly improved in 96.4% of cases. The CUI was improved from 58+/-0.3% to 87+/-0.8%, P < 0.005 (Student's t-test). The improvement of the BCVA was from 20/40+/-20/100 to 20/25+/-20/100, P < 0.005 (Student's t-test). The results obtained in group 2 were not clinically significant in terms of improvement of CUI and BCVA.


CONCLUSIONS
Using the corneal topographic map as a guide, selective zonal ablations with excimer laser can be used to create a more regular corneal surface, when a defined pattern of topographic irregularities can be defined.
Alió
J L
JL
Instituto Oftalmológico de Alicante, Spain. oftalio@ibm.net
Artola
A
A
Rodriguez-Mier
F A
FA
D000328:Adult; D001251:Astigmatism / Q000209:etiology / Q000601:surgery*; D003315:Cornea / Q000473:pathology / Q000601:surgery*; D019781:Corneal Topography; D016039:Corneal Transplantation / Q000009:adverse effects*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000009:adverse effects*; D017075:Laser Coagulation / Q000009:adverse effects*; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery; D018903:Photorefractive Keratectomy / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D014792:Visual Acuity