June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
A diagnostic biomechanical framework to distinguish keratoconus and normal eyes using air-puff applanation
Author Affiliations & Notes
  • Pooja Khamar
    Cornea and refractive services, Narayana Nethralaya, BANGALORE, India
  • Mathew Francis
    IBMS LAB, NARAYANA NETHRALAYA, BANGALORE, KARNATAKA, India
  • RUSHAD SHROFF
    Cornea and refractive services, Narayana Nethralaya, BANGALORE, India
  • Natasha Pahuja
    Cornea and refractive services, Narayana Nethralaya, BANGALORE, India
  • Roshan T
    Cornea and refractive services, Narayana Nethralaya, BANGALORE, India
  • Rohit Shetty
    Cornea and refractive services, Narayana Nethralaya, BANGALORE, India
  • HIMANSHU MATALIA
    Cornea and refractive services, Narayana Nethralaya, BANGALORE, India
  • Abhijit Sinha Roy
    IBMS LAB, NARAYANA NETHRALAYA, BANGALORE, KARNATAKA, India
  • Footnotes
    Commercial Relationships   Pooja Khamar, None; Mathew Francis, None; RUSHAD SHROFF, None; Natasha Pahuja, None; Roshan T, None; Rohit Shetty, None; HIMANSHU MATALIA, None; Abhijit Sinha Roy, Cleveland Clinic Innovations , India (P), SIBAC grant, Indo-German Science and Technology center, India. (F)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 4347. doi:
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      Pooja Khamar, Mathew Francis, RUSHAD SHROFF, Natasha Pahuja, Roshan T, Rohit Shetty, HIMANSHU MATALIA, Abhijit Sinha Roy; A diagnostic biomechanical framework to distinguish keratoconus and normal eyes using air-puff applanation. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4347.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To develop a diagnostic classification score for keratoconus using waveform analyses of corneal deformation

Methods : 44 normal (44 patients) eyes, 62 suspect (fellow eyes of unilateral keratconus patient) eyes and 143 keratoconus (143 patients) were evaluated with Pentacam and Corvis-ST (OCULUS Optikgerate Gmbh, Germany). A spring and dashpot model (Matalia et al., J Ref. Surg., 2016; 32: 486-93) was used to derive corneal stiffness and other waveform derived variables. The model used segregated corneal and extra-tissue deformation from the total deformation amplitude (DA) reported by Corvis-ST. Based on the biomechanical model corneal stiffness was defined as linear [kc (constant)] and a non-linear measure [kc (mean)]. Multivariate linear regression analyses was performed. Area under the curve (AUC), sensitivity and specificity of the adjusted variables were obtained after including the suspect eyes in the keratoconus group. Cone location magnitude index (CLMI) was also calculated.

Results : Analysis showed peak DA (1.08±0.02 vs. 1.18±0.02), applanation 1 time (7.25±0.01 vs. 7.20±0.01 msec), applanation 2 time (21.5±0.04 vs. 21.58±0.02 msec), kc (constant) [109.4±1.64 vs. 98.37±1.33 N/m], kc (mean) [107.53±2.02 vs. 93.38 N/m] and corneal peak DA [0.95±1.95×10-2 vs. 1.01±1.12×10-2 N/m] were significantly different between normal and keratconus eyes (p<0.001). Calculated and measured parameters of the fellow eyes (suspect) were similar to the keratconus group, particularly grade 1 (p>0.05). The AUC was highest in kc (constant) and kc (mean) (0.97 and 0.98 respectively) with sensitivity (>95%)and specificity (>88%). The logistic regression with the combination of kc parameters (constant and mean) improved AUC to1.0 (cut-off probability score of 0.82 between normal and keratoconus eyes including suspect eyes, 99.2%, 100.0%).

Conclusions : The suspect as well as keratoconus eyes could be differentiated from normal eyes based on corneal stiffness accurately. Further studies with eyes from different populations are needed to validate the scoring system based on corneal stiffness.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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