Orbscan Evaluation of Corneal Power after Myopic PRK: Placido Disc-Based vs Scanning Slit Topography

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• 作者：Nicola Rosa¹ ; ² ; ^{nicola.rosa@unina2.it} ; Luigi Capasso³ ; Emma Minutillo¹ ; Maria Borrelli² ; Maddalena De Bernardo² ; Michele Lanza¹ ; ²
• 关键词：corneal power ; myopic PRK ; placido disc ; scanning slit topography
• 刊名：Journal of Optometry
• 出版年：2009
• 出版时间：2009
• 年：2009
• 卷：2
• 期：2
• 页码：94-100
• 全文大小：649 K

文摘

Purpose

To compare Placido disc-based and scanning slit topography in the evaluation of corneal power changes after PRK.

Methods

The changes in corneal power, evaluated with an Orbscan II utilizing both Placido disc-based and Scanning Slit topography, before and 1, 3 and 6 months after PRK were compared with refractive changes in 109 individuals (149 eyes) who underwent photorefractive keratectomy (PRK) with a sphero equivalent refraction, calculated at the corneal apex, ranging from -0.25 to -12 D (mean -4.58¡À2.54 D).

Results

1,3 and 6 months refractive changes showed a good correlation with changes in BFS (r²=0.64, r²= 0.53, r²= 0.62, respectively); in Sim K's (r²= 0.77, r²= 0.8, r²= 0.78, respectively) in Mean Power 3 mm (r²= 0.81, r²= 0.88, r²= 0.87, respectively) in Mean Power 5 mm (r²= 0.68, r²= 0.78, r²= 0.78, respectively) in Anterior Mean Power 3 mm (r²= 0.88, r²= 0.85, r²= 0.85, respectively) in Anterior Mean Power 5 mm (r²= 0.75, r²= 0.7, r²= 0.75, respectively) in Total Mean Power 3 mm (r²= 0.75, r²= 0.71, r²= 0.79, respectively) in Total Mean Power 5 mm (r²= 0.75, r²= 0.71, r²= 0.78, respectively). However, all differences were statistically significant (P<0.001).

Conclusion

The data obtained with the scanning slit system seem to be more reliable, but need correcting factors to improve their precision.