The record 101 scientific posters on display at the 2017 Global Specialty Lens Symposium (GSLS) was a good indicator that GP lenses would have an important presence...and they did, with almost 60% of the posters pertaining to scleral lenses. This included many case reports in which scleral lenses changed the life of a patient—including a patient who had been struck by lightning (Cunningham, 2017)! This column will focus on the results of three research studies pertaining to scleral and hybrid lenses.
Three Scleral and Hybrid Posters
- DeNaeyer GW, Sanders DR, Farajian TS. Surface Coverage with Single vs. Multiple Gaze Surface Topography to Fit Scleral Lenses. The authors took advantage of the benefits of corneo-scleral elevation topography systems, which can determine both the sagittal height (sag) of the eye at the diameter of the scleral lens and the shape of the sclera. They used the sMap3D (Visionary Optics, manufactured by Precision Ocular Metrology), which takes three images from different gaze directions and stitches them together to produce one wide topographic image, in this study. The three-image information was compared to data obtained from a single straight-gaze image in terms of providing a sufficient area of measurable sclera (coverage) to obtain accurate data for mini-scleral and full scleral lens fitting.
The authors found that at the 14mm, 15mm, 16mm, 18mm, and 20mm diameter circles, the straight-gaze image covered only 68%, 53%, 39%, 18%, and 6% of the ocular surface, respectively, while the stitched image covered 98%, 96%, 93%, 75%, and 32%, respectively. This is particularly important for the popular 15mm (96% coverage versus 53%) and 16mm (93% coverage versus 39%) diameters. It was concluded that a three-gaze stitched image from a corneo-scleral topographer was more accurate compared to a straight-gaze image for fitting scleral lenses.
- Doan TT, Kolozhvari E, Lee R, Hernandez R. Assessing the HyperBond at the Junction of RGP and SiHy in SynergEyes Hybrid Duette Contact Lens. A problem with the early generations of hybrid lens designs was tearing at the junction between the GP and soft regions of the lens, often occurring upon lens removal. As is well known, this has not been a problem observed with the multiple lens designs manufactured in recent years by SynergEyes. The purpose of this study was to evaluate the bond strength at the junction of SynergEyes Duette hybrid contact lenses by measuring its tensile strength.
The tensile tests of the 21 lens samples indicated that they could withstand approximately 8.5 times the force applied by a finger during cleaning before breakage occurred. The lenses were stretched beyond their point of recovery before breakage occurred. None of the tested lenses separated at the junction. The authors concluded that the occurrence of breakage within the silicone hydrogel (SiHy) skirt and not at the junction indicates that the HyperBond strength at the junction of the GP and SiHy parts of the lens is higher compared to the tensile strength of the SiHy skirt.
- Yeung D, Sorbara L. A survey of scleral lens prescribing trends and complications. The authors surveyed North American scleral lens fitters on their prescribing habits, with 93 of 197 (47.2%) responding. Among the results, they found the following:
- 87% prescribe lenses between 15.1mm and 18mm in overall diameter.
- 89% achieve between 150 to 250 microns of central corneal clearance after settling.
- 82% achieve between 50 to 75 microns of limbal clearance after settling.
- 26.8% of the respondents’ patient population experienced midday fogging.
- Limbal hyperemia was present in 23.7% of the patients.
- Corneal staining was observed by respondents in 13.3% of the patient population. CLS
For references, please visit www.clspectrum.com/references and click on document #257.