Analysis of Corneal Distortion after Myopic PRK

Michele Lanza,Francesca Simonelli,Sandro Sbordone,Ugo Antonello Gironi Carnevale,Rosa Boccia,Luigi De Rosa

doi:10.3390/jcm10010082

Michele Lanza, Francesca Simonelli + Show 4 more

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https://doi.org/10.3390/jcm10010082

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Abstract

The purpose of the study is to evaluate the corneal biomechanical properties (CBP) and their behaviors after myopic refractive surgery both with Ocular Response Analyzer (ORA) and Corvis ST (CST). This retrospective study included 145 eyes of 145 patients with a mean age of 33.13 ± 9.24 years, who underwent myopic photorefractive keratectomy (PRK) for a refractive defect, measured as spherical equivalent, of mean −4.69 ± 2.04 D and have been evaluated before surgery and at 1, 3 and 6 months follow-up. Corneal hysteresis (CH) and corneal resistance factor (CRF) values significantly decreased after 1 month and remained statistically stable during further follow-ups. CST parameters had a different evolution: only second applanation time (AT2) differences showed a significant variation after 1 month that did not statistically change over time. Highest concavity deformation amplitude (HCDA), highest concavity peak distance (HCPD), first applanation time (AT1) and velocity (AV1) showed continuous significant differences both after 3 and after 6 months. This study suggests that after central surface ablation surgery, such as myopic PRK, corneal shape is remodeling, and its deformation parameters are going to change even at 6 months follow-up. This indicates that it should be important to evaluate refractive surgery patients during a longer follow-up because this could allow earlier diagnosis and better management of late-onset complications.

Highlights

Assessment of in vivo corneal biomechanical properties (CBP) is gaining more importance in many aspects of ophthalmology, such as refractive surgery [1], corneal transplant [2,3], intraocular pressure evaluation [4] and overall eyeball deformation analysis [5].There are currently two devices able to provide CBP evaluation, and both of them analyze the corneal response to an air pulse stimulus: the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA) [6] and the Corvis ST (CST; Oculus, Wetzlar, Germany) [7,8]
Changes detected in CST parameters had a different behavior: only AT2 showed a significant change after 1 month that did not statistically change during further follow-up, whereas AT1, AV1, highest concavity peak distance (HCPD) and Highest concavity deformation amplitude (HCDA) showed a continuous significant change both after
The results observed in this study suggest that after central surface ablation surgery, such as myopic photorefractive keratectomy (PRK), corneal shape is still remodeling, and its deformation parameters are going to change during the first 6 months after surgery

Summary

Introduction

Assessment of in vivo corneal biomechanical properties (CBP) is gaining more importance in many aspects of ophthalmology, such as refractive surgery [1], corneal transplant [2,3], intraocular pressure evaluation [4] and overall eyeball deformation analysis [5]. There are currently two devices able to provide CBP evaluation, and both of them analyze the corneal response to an air pulse stimulus: the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY, USA) [6] and the Corvis ST (CST; Oculus, Wetzlar, Germany) [7,8]. Even if some of the other mentioned procedures are accepted, PRK is the preferred choice to correct myopia in the Air

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