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Michael Sullivan-Mee, Suchitra Katiyar, Denise Pensyl; Long-term variability of corneal hysteresis and corneal resistance factor. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3139. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate corneal biomechanical parameter measurement variability over a several-year period in eyes with and without glaucoma.
All subjects were participating in a prospective, longitudinal glaucoma research study at the Albuquerque VA Medical Center in which corneal hysteresis (CH) and corneal resistance factor (CRF) measurements were obtained at 6 month intervals for subjects diagnosed Primary Open-Angle Glaucoma (POAG), Ocular Hypertension (OH), and Glaucoma Suspect (GS), and at 6 to12-month intervals for normal controls (NML). Subjects were required to have at least four years of follow-up and at least six good quality CH and CRF measurements. Right eyes were analyzed unless the right eye did not meet diagnostic criteria and then the left eye was analyzed. For both CH and CRF, linear regression slopes, longitudinal within-subject standard deviations, and within-subject coefficients of variation (COV) were calculated. Regression analyses were utilized to investigate factors associated with longitudinal CH and CRF behavior.
Over a mean period of 6.0 ±1.3 years, we obtained an average of 11.9 ±3.5 measurements in 98 POAG, 49 OH, 39 GS, and 50 NML eyes. Among all eyes, mean CH and CRF decreased over time (-0.14 ±0.09 mmHg and -0.17 ±0.11 mmHg per year respectively). While CRF showed greater reduction over time in the POAG and OH groups versus the GS and NML groups (p<0.001), CH change over time was similar for all four diagnostic groups. Within-subject COV was highest for the POAG group (10.2%), followed by the OH (9.6%), GS (8.3%) and NML (8.1%) groups (POAG>GS and NML groups, p=0.005). In multivariate regression analyses, several factors were independently related to CH and CRF measurement variability, including higher mean IOP, diagnosis, use of a prostaglandin analog, and CH and CRF slopes over time.
Our results show that inter-visit CH and CRF measurement variability is substantial, particularly when considering the diagnostic range of these parameters. Many factors were identified as being independently related to CH and CRF variability over time, and consideration of these factors may be useful for interpretion of CH and CRF values.
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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