Evaluation of the relationship of corneal biomechanical metrics with physical intraocular pressure and central corneal thickness in ex vivo rabbit eye globes Q6 Q5 FangJun Bao a, b , ManLi Deng a, b , QinMei Wang a, b , JinHai Huang a, b , Jing Yang a, b , Charles Whitford c , Brendan Geraghty c , AYong Yu a, b, * , Ahmed Elsheikh c, d a The Affiliated Eye Hospital of WenZhou Medical University, Wenzhou, 325027, China b The Institution of Ocular Biomechanics, Wenzhou Medical University, Wenzhou, Zhejiang Province, 325027, China c School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK d National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, UK article info Article history: Received 12 January 2015 Received in revised form 14 May 2015 Accepted in revised form 26 May 2015 Available online xxx Keywords: Corneal biomechanical behavior Ex vivo Whole globe inflation experiment Intraocular pressure Central corneal thickness abstract The relationship of corneal biomechanical metrics provided by the Ocular Response Analyzer (ORA) and Corvis ST (CVS) with physical intraocular pressure (IOPp) and central corneal thickness (CCT) was evaluated. Thirty fresh enucleated eyes of 30 rabbits were used in ex vivo whole globe inflation exper- iments. IOPp was measured with a pressure transducer and increased from 7.5 to 37.5 mmHg in steps of 7.5 mmHg while biomechanical data was acquired using the ORA and CVS. At least 3 examinations were performed at each pressure level, where CCT and twelve biomechanical metrics were recorded and analyzed as a function of IOPp. The biomechanical metrics included corneal hysteresis (CH) and corneal resistance factor (CRF), obtained by the ORA. They also included the applanation times (A1T, A2T), lengths (A1L, A2L) and velocities (A1V, A2V), in addition to the highest concavity time (HCT), peak distance (PD), radius (HR) and deformation amplitude (DA), obtained by the CVS. The variation of CCT and the twelve biomechanical metrics for the 30 rabbit eyes tested across the 5 pressure stages considered (inter-pressure differences) were statistically significant (P ¼ 0.00). IOPp was highly to moderately correlated with most biomechanical metrics, especially CRF, A1T, A1V, A2V, PD and DA, while the relationships with CH, A2T, A1L and HCT were poor. IOP has important influences on most corneal biomechanical metrics provided by CVS and ORA. Two biomechanical metrics A1V and HR were influ- enced by CCT after correcting for the effect of IOP in most pressure stages, while the correlation with others were weak. Comparisons of research groups based on ORA and CVS with different IOPs and CCTs may lead to possible misinterpretations if both or one of which are not considered in the analysis. © 2015 Published by Elsevier Ltd. 1. Introduction The cornea accounts for more than two thirds of the refractive power of the eye and is an important part of the outer, mechanically-tough, ocular tunic, which protects the eye's internal components (Fatt, 1978). Because of its importance to clear vision, a great deal of research has been conducted to understand its per- formance and how it responds to disease and surgery (Jue and Maurice, 1986), (Kurita et al., 2007). This included careful evalua- tion of the health and adequacy of the cornea to identify keratitis, increase the accuracy of corneal refractive surgery and prevent iatrogenic keratectasia (Seiler et al., 1998). In addition, the cornea's mechanical properties, essential for maintaining its dimensional stability and hence clear vision, rely primarily on the cornea's thickness and the biomechanical behavior of the tissue (Liu and Roberts, 2005), this topic has attracted increasing attention in recent years (Ali et al., 2014; Mikula et al., 2014; Wolffsohn et al., 2012). Understanding the cornea's biomechanical behavior is impor- tant for several clinical applications. A clear example is refractive * Corresponding author. No. 270 Xueyuan West Road, WenZhou City, ZheJiang Prov 325027, China. Q1 E-mail address: yaybetter@hotmail.com (A. Yu). Contents lists available at ScienceDirect Experimental Eye Research journal homepage: www.elsevier.com/locate/yexer http://dx.doi.org/10.1016/j.exer.2015.05.018 0014-4835/© 2015 Published by Elsevier Ltd. Experimental Eye Research xxx (2015) 1e7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 YEXER6676_proof ■ 28 May 2015 ■ 1/7 Please cite this article in press as: Bao, F., et al., Evaluation of the relationship of corneal biomechanical metrics with physical intraocular pressure and central corneal thickness in ex vivo rabbit eye globes, Experimental Eye Research (2015), http://dx.doi.org/10.1016/ j.exer.2015.05.018