Abstract
Purpose :
As the scleral gas-permeable contact lens (SGP) becomes more widely prescribed for both irregular and regular corneas, more practitioners have integrated the technology of anterior segment optical coherence tomography (AS OCT) in its design and fit evaluation. In particular, the utilization of the built-in caliper tools of these instruments have become common practice to monitor the post-lens tear thickness, or the central corneal clearance (CCC). This study compared the agreement among high-definition AS OCT instruments in the measurement of scleral lens thicknesses in vivo against their validated corneal thickness measurements by the same software, and against scleral lens thickness measurements by digital thickness gauge.
Methods :
Baseline pachymetry maps on both eyes of one of our investigators were obtained with three different instruments: two AS OCT and one Scheimpflug system. High definition imaging of the corneas were also obtained as baseline, after which images of the anterior segment in different scleral lenses were captured. The built-in caliper tool of each instrument was used to measure the center thickness of each scleral lens, the CCC, and the central corneal thickness. The scleral lens thickness measurements by a digital thickness gauge were used as reference.
Results :
There was close agreement among all the instruments in central corneal thicknesses; however, both scleral lens thicknesses and the CCC varied, almost by a factor of 1.5, between two instruments.
Conclusions :
Further investigation into the calibration of these instruments may be necessary before they are applied to scleral lens design and fit evaluation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.