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Bruno Lay, Christine W Sindt, Ronan Danno; Comparing scleral contact lenses generated by impression technology vs Scheimpflug images. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1763.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this project was to evaluate elevation data generated by impression technology vs rotating Scheimpflug imagery of the anterior ocular surface, looking for stability and alignment to the ocular surface of the lenses generated by the elevation specific data.
The elevation specific lens design software (EPD) was modified to import a digitized impression as an STL file, or a Corneo-Scleral Profile (CSP) in CSV/DIF format, generated by the Scheimpflug system. The set of points of the CSP file was then automatically triangulated to be displayed in the EPD software. The optic center was automatically positioned at the CSP apex (Vertex Normal) location, and could be manually amended if needed. The remaining steps of the lens design remained the same, including Rx (spherical, torics, prism, HOAs) and clearance specification, and the final export to DAC and Optoform lathes.10 patients with normal eyes were recruited: 2 lenses per eye were generated with the impression and the CSP data. Lens diameter was limited to 16 millimeters. 3 dots were generated on the front surface of the lens on the limbal junction at 3,6 and 9 o’clock. The following parameters were assessed: Scleral lens comfort, high speed photography to measure vertical movement, rotational stability, horizontal and vertical corneal diameters, and centration using the limbal dots, central/limbal vault and landing on the scleral using ocular coherence tomography.
Lenses generated had similar fit profiles to the ocular surface. On average CSP lenses settled 48.5 microns in 30 minutes while impression lenses settled 17.75 microns. Comfort was comparable. All lenses had slight vertical movement without rotation, optics stayed centered. CSP data showed smaller limbal diameters than impression data. All lenses landed tangentially on the sclera.
Impression technology has been validated over many years and contact lenses have been successfully fit with this data. Rotating Scheimpflug cameras give similar data up to 16mm and can successfully generate mini scleral contact lenses. The Scheimpflug camera can give additional data such as pupil center, visual axis, automated limbal detection and posterior cornea higher order aberration. Scheimpflug technology opens the market for not only elevation specific mini scleral lens design, but also advanced optics including visual axis aligned multifocal and HOA correction.
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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