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A story of unwanted outcomes: biomechanics of corneal cross-linking in keratoconic eyes

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Session Details

Session Title: Medical Cornea & Biomechanics

Session Date/Time: Sunday 23/09/2018 | 08:00-10:00

Paper Time: 08:57

Venue: Room A3, Podium 3

First Author: : R.Vaishnav INDIA

Co Author(s): :    R. Shetty   A. Roy   P. Khamar   M. Francis           

Abstract Details


In vivo biomechanics of keratoconus after corneal cross-linking (CXL) procedure has been an intriguing question among corneal surgeons. This study aimed to quantify the corneal stiffness change after CXL procedure and link the same to corneal tomographic parameters.


Study was conducted at Narayana Nethralaya Eye Hospital, Bangalore, India. Avedro KXL (Avedro Inc, USA) was used for CXL procedure. Corvis -ST and Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) was used for corneal biomechanics and tomographic measurements respectively.


111 keratoconus eyes, which underwent accelerated CXL using 0.1% riboflavin solution and 9mW/cm2 UV-A beam for 10 min after epithelium removal, were analyzed. The analysis focused on algorithmically derived corneal stiffness (kc) from corneal deformation waveform reported by Corvis -ST. This was then compared to tomographic parameters reported by Pentacam HR. Based on the change in corneal stiffness preoperative (pre-op) to 3 months postoperative (post-op), the data was split into decreased (<-5%), no change and increased (>+5%) kc groups. The study also reports new Corvis-ST parameters such as CBI (corneal biomechanical index) and TBI (total biomechanical index).


Keratometry, BAD-D, pachymetry were similar between the groups at pre-op time point. Percentage stiffness change after surgery were -17% (102.28±3.23 and 84.82±2.57N/m, pre-op and post-op respectively; p<0.001), <0.5% (87.46±1.57 and 87.04±1.67N/m; p=0.48) and +19% (86.68±3.67 and 102.85±3.48N/m; p<0.001) for decreased, no change and increased groups, respectively. Increased or no change in kc was observed in 79% eyes. HORMS of aberrations was unchanged, reduced by -6% and -22.7%, respectively in the above kc groups. A similar trend was noted in lower order aberrations. Keratometry, CBI and TBI showed no changes within the groups.


These results showed the inadequacy of conventional tomographic indices in accurately capturing the stiffening effect of CXL. The stiffness parameter was accurately able to quantify the biomechanical changes after CXL in accordance with total change in surface wavefront aberrations. This novel stiffness parameter could be a viable early marker in evaluating CXL outcomes.

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