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Ashima Bajaj, Rohit Shetty, Rashmi Deshmukh, Tushar Grover, Natasha Pahuja; Influence of post crosslinking haze on the repeatability of topography machines.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5279.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the repeatability of corneal measurements using various topographers post accelerated collagen crosslinking (ACXL) and to study effect of post ACXL haze on the measurement of thinnest corneal thickness(TCT) and mean keratometry(Km).
Sixty eyes of 60 patients who had undergone ACXL a year before underwent imaging with scanning slit (OrbscanII) and three Scheimpflug imaging devices (PentacamHR, Sirius and Galilei) in this prospective study. Three measurements of each eye of TCT, steep(K1), flat keratometry(K2) and Km were obtained. Haze was measured using densitometry software on PentacamHR. Effect of haze on repeatability of TCT and Km was evaluated using regression models.Coefficient of repeatability (CRw) and coefficient of variation (CVW) were used to test repaetability.
The mean parameter measurements with different instruments were compared by repeated measures ANOVA.Twenty-seven female and 33 male patients with a mean age of 23 ± 5.32 years(range15-36) were analyzed. CRw for TCT in Orbscan was significantly worse than those of the Scheimpflug devices (p<0.05) whereas K1, K2 did not show statistically significant difference. CVw for TCT, K1 and K2 for Orbscan was significantly higher than those of Scheimpflug devices (p<0.05). Haze was maximum in anterior and central 0-2mm zone of cornea. Haze affected TCT measurement of Orbscan (p<0.05) in all zones while its repeatability was affected with PentacamHR and Sirius (p<0.05). Km was affected by haze on PentacamHR (p<0.05) while other topographers showed good measurements. Km repeatability was unaffected for all devices.
Scheimpflug devices are less variable while measuring corneal parameters in post ACXL eyes than slit scanning device. Galilei parameters were the least affected by haze. Hence topography measurements in the presence of haze should be interpreted with caution.
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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