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Christine W Sindt, Bruno Lay, Ronan Danno; Repeatability and Validation of Scheimpflug Scleral Data. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1774.
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© ARVO (1962-2015); The Authors (2016-present)
To access the repeatability and validate the elevation data of the scleral profile using Scheimpflug technology (ST)
The ST normally captures up to 12mm corneal surface. With enhanced software, the coverage can be extended up to 16mm by collecting 5 scans. This is accomplished by:1. Using lower light for measuring the peripheral scleral area2. The 4 peripheral exams (nasal, temporal, superior, inferior) are captured in primary gaze displacing the machine by 1 mm and not by moving the fixation.3. The 5 exams (4 peripheral and one central) are stitched together to create one 3D shape file covering 16mm of the cornea and sclera. Since there is no fixation displacement during image capture, tilt reconstruction is not necessary. Each sub-exam uses 25 segmental images, so a total of 125 Images are captured during the acquisition phase.22 eyes were scanned at 2 different time point using ST. The scans were imported into the EyePrint Designer Software (EPD)On the 3-D ocular image, 5+ points were chosen to define the best fit limbal circle in the x,y axis. A best fit plane drawn through the limbal points was defined in the z axis.Starting at 0.5mm beyond the limbal circle, along the limbal plane, the distance from the limbal plane to the scleral surface was measured. A series of concentric scleral rings, 100 microns apart with 90 meridians per ring, serve as the data locations from the limbal plane to scleral surface measurements (D value). Concentric rings are measured up to 4mm beyond the limbus.Ocular impressions of the same subjects were obtained and D values were obtainedThe 2 scans on each eye were analyzed for scleral elevation deviations and they were compared the impression data
Not all ST scans were able to reach 4mm past the limbus. The average difference between the 2 ST scans is .01666 mm with a SD of .05430 mm.The average difference between the scan and impression data is .86767 with an SD of .07679The average limbal diameters difference between the ST scans were .126 microns. The difference in limbal diameters between the ST scans and impression data is .792 microns
Scheimpflug scanning data provides reasonable elevations measurements up to 16mm, which are consistent over multiple scans and corresponds to impression elevations.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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