Comparison of Corneal Biomechanical Properties between Post-LASIK Ectasia and Primary Keratoconus
Wuxiao Zhao, Yang Shen, Weijun Jian, Jianmin Shang, Vishal Jhanji, Aruma Aruma, Xingtao Zhou
Abstract
Purpose. To compare the corneal biomechanical properties between post-LASIK ectasia and primary keratoconus. Methods. A total of 42 eyes of 42 patients with matching age and central corneal thickness (CCT) were divided into two groups according to diagnosis of post-LASIK ectasia (PLE group; n = 21; age range: 22–47 years) and primary keratoconus (KC group; n = 21; age range: 21–47 years). The corneal biomechanical properties were assessed using Scheimpflug-based technology (Corvis ST; Oculus Optikgeräte, Wetzlar, Germany). The paired t-test and linear regression analysis were performed. Results. The PLE group had significantly higher mean stiffness parameter at the first applanation (SP-A1; 76.65 ± 21.66 vs 52.72 ± 13.65, <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mi>p</a:mi> <a:mo>≤</a:mo> <a:mn>0.001</a:mn> </a:math> ) and mean stress-strain index (SSI) (SSI: 0.78 ± 0.16 versus 0.64 ± 0.12, <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:mi>p</c:mi> <c:mo>=</c:mo> <c:mn>0.001</c:mn> </c:math> ) than the KC group. SP-A1 was positively correlated with CCT in the PLE group (Pearson’s r = 0.816, <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mi>p</e:mi> <e:mo>≤</e:mo> <e:mn>0.001</e:mn> </e:math> ), but not in the KC group (Pearson’s r = −0.014, <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" id="M4"> <g:mi>p</g:mi> <g:mo>=</g:mo> <g:mn>0.952</g:mn> </g:math> ). No statistical correlation was observed between SSI and CCT in either group (Pearson’s r = 0.292, <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M5"> <i:mi>p</i:mi> <i:mo>=</i:mo> <i:mn>0.199</i:mn> </i:math> , and Pearson’s r = 0.004, <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" id="M6"> <k:mi>p</k:mi> <k:mo>=</k:mo> <k:mn>0.985</k:mn> </k:math> , respectively). Conclusions. In our case series, KC manifested more severe than PLE in biomechanical properties. Since SSI measurements were independent of corneal thickness, it can be used for corneal biomechanical assessment.