Prevalence of Central Islands in Corneal Topographic Analysis after Excimer Laser Photo refractive Keratectomy for Myopia

Lee, Sang Bumm; Kim, Hee Kyu; Hahn, Duk Kee

Abstract

We analyzed the central islands in corneal topography after excimer laser photo refractive keratectomy(VISX Twenty/Twenty B(R) with VisionKey(TM) VISX, Inc. Santa Clara, CA, USA) to evaluate the prevalence of central island and the factors associated with their occurrence, prospectively. Corneal topographic analysis using Corneal Analysis System(EyeSys Technologies, Inc. Houston, TX, USA) was performed in 94 eyes of 77 patients at the postoperative 1-, 3- and 6-months after excimer laser PRK. Central islands were seen in 27%(25/92), 10%(8/79) and 8%(5/64) of patients at postoperative 1-, 3- and 6-months, respectively. There was statistically significant decrease in the occurrence of central island between postoperative 1 and 3 months follow-up groups(p<0.01). In consequence, central islands tended to resolve with time. There was no association between island prevalence and type of procedure(Photorefractive keratectomy vs Photorefractive astigmatic keratectomy), the amount of attempted correction (6D down vs 6D up), age or sex(All: p>0.05). We found that there was no demonstrable effect of central islands on the decrease of best spectacle corrected visual acuity at postoperative 1 month(p>0.05). Occurrence was statistically significantly decreased in the patients treated with the version 4.01 of central island removal software(1 month: p<0.01, 3 months: p<0.05). We suggest that the version 4.01 software of VISX 20/20B(R) was very effective to reduce the prevalence of central island after excimer laser PRK. In conclusion, if the software would be adjusted to increase the number of pulses centrally, this might reduce the prevalence of central island. New strategies and algorithms might be developed to reduce the prevalence of central islands.