GP Insights

Sclerals Dominate GSLS Posters

BY EDWARD S. BENNETT, OD, MSED, FAAO

Scleral lenses represented the most common subject of the record 67 scientific poster presentations at the 2014 Global Specialty Lens Symposium (GSLS), held Jan. 23 to 26 in Las Vegas.

Six Notable Scleral Posters

Following are some of the important findings of these scleral poster presentations.

1 Midday Visual Fogging in Scleral Lens Wearers – Does Fit Matter? (Leach et al) This poster was awarded first place in the research-based poster competition. The authors compared individuals who wore scleral lenses all day without interruption versus those who had to remove and reapply them after eight hours due to fogging. They found that the interrupted wearers had a much higher Dry Eye Questionnaire score (i.e., eyes much drier), a much higher average post-lens tear layer thickness (i.e., 575µm versus 315µm), and were almost twice as likely (i.e., 71.4% versus 37.5%) to exhibit a tight peripheral edge fit.

2 Corneal Thickness Variation Post Scleral Lens Wear (Achong-Coan et al) The authors noted that there is 2.8% corneal swelling upon awakening when no lens is worn. Considering this, they measured corneal swelling following eight hours of open-eye scleral lens wear in three different materials from Contamac. They found 2.27% corneal swelling with Optimum Comfort (Dk = 65,), 1.54% with Optimum Extra (Dk = 100), and 1.39% with Optimum Extreme (Dk = 125). They concluded that these corneal swelling levels—notably with >100 Dk materials—are within clinically acceptable limits.

3 Sagittal Depth Relationship to High Contrast Visual Acuity and Low Contrast Visual Acuity with Scleral Contact Lenses (Kuhn & LaKamp) The authors fitted 30 subjects with a series of four lenses of varying sagittal depth. They found no significant impact of vault height on either high-contrast or low-contrast visual acuity. They concluded that best-corrected visual acuity is not necessarily impacted by high-vaulting scleral lenses needed for advanced corneal abnormalities.

4 Scleral Lens Clearance Assessment by Biomicroscopy (Yeung & Sorbara) This study evaluated the accuracy of measuring central corneal clearance (CCC) using biomicroscopy relative to an image-processing program. The authors found an overall trend for underestimation by approximately 50 microns in all subjects regardless of prior experience with scleral fitting. However, it was concluded that this pilot study validates estimation of CCC through biomicroscopy.

5 Introducing a Scleral Lens Fit Assessment Based on Tear Layer Thickness Guide (DiNardo et al) Participants in an online survey were asked to select which of several options best represented central clearance of a scleral lens design. They were then shown the MCO (Michigan College of Optometry) scleral lens fit scale system and subsequently asked to grade the central vault of several lenses. The accuracy of all respondents increased significantly after using the lens fit scale system. The authors concluded that the MCO scleral fitting guide can improve both accuracy and confidence in assessing scleral vault.

6 Estimation of Refractive Power of Scleral Lens/Fluid Reservoir Optical Systems in Non-Parallel Scleral Lens Fits (Schornack et al) This study evaluated the theoretical contribution of the fluid reservoir to an entire scleral lens/fluid reservoir optical system and how scleral lens power, corneal curvature, fluid reservoir depth, and disparity between keratometric indices and scleral lens base curve affect the power of the entire optical system. The authors found that the calculations typically used to predict over-refraction with corneal GPs do not accurately predict scleral lens power. They also concluded that refraction over scleral lenses is essential to determine optimal refractive correction. CLS

For references, please visit www.clspectrum.com/references.asp and click on document #220.

Dr. Bennett is assistant dean for Student Services and Alumni Relations at the University of Missouri-St. Louis College of Optometry and is executive director of the GP Lens Institute. You can reach him at ebennett@umsl.edu.