Nine GP Pearls From the GSLS
BY EDWARD S. BENNETT, OD, MSED, FAAO
The Global Specialty Lens Symposium (GSLS) had an emphasis on GP lenses this year, notably on scleral lens applications. Following are some pearls from the 2013 GSLS meeting.
Nine Pearls From Vegas
1 Patrick Caroline, FAAO, discussed the two-year results of Dr. Pauline Cho’s Retardation of Myopia in Orthokeratology (ROMIO) study (Cho et al, 2012). With 102 subjects aged 6 to 10 randomly assigned to either ortho-k or glasses wear, the ortho-k subjects had a slower rate of axial elongation by 43 percent.
2 On the same theme, in his keynote address, Professor Brien Holden discussed the results of a study (Hiraoka et al, 2012) in which young people wearing spectacles or overnight ortho-k were evaluated over a five-year period. Axial length progression was significantly different (0.99 for overnight ortho-k and 1.41 for the spectacle group), primarily during the first three years.
3 Patrick Caroline described the “Mountford” method of removing debris from the front surface of a scleral lens. A DMV wetted with a lubricating drop is placed on the lens while on-eye and moved across the anterior surface like a “squeegee.”
4 The shift toward more scleral lens fitting was evident and was commented on in Dr. Jason Nichols’ state of the industry address. He stated that in a survey for Contact Lens Spectrum, when practitioners were asked which GP lens they would use for fitting an irregular cornea patient, 33 percent indicated a scleral lens as compared to 67 percent indicating corneal/intralimbal lenses.
5 Patrick Caroline, in a study at Pacific University, found that the tear layer depth decreased by an average of 96 microns after eight hours of scleral lens wear and a total of 146 microns after one month of wear. Therefore, Dr. Langis Michaud recommended a minimum of 100 microns of tear layer thickness after settling for smaller scleral lenses, and Patrick Caroline recommended 300 to 400 microns of clearance upon dispensing. Excessive clearance (>500 microns initially) can result in compromised optics due to the large vault, mucus and too much negative pressure under the lens, and application bubbles.
6 Although edema problems are not common with scleral lenses, Dr. Christine Sindt commented that she will not fit anyone with sclerals who has an endothelial cell count of less than 800. She found in a record review that individuals whom she had fit who had a cell count between 600 to 800 were more likely to have hypoxia-related complications.
7 It is important to evaluate the lens periphery in scleral lenses. Using an optic section with the slit lamp is a good predictor of central clearance, while optical coherence tomography is beneficial for evaluating the edge-sclera relationship. The edge should align with the sclera; if embedded into the sclera, a flatter (outer) peripheral curve radius is indicated. For more localized conjunctival impingement, Dr. Halina Manczak recommended a toric or quadrant-specific periphery.
8 Patrick Caroline reported that smaller (i.e., 15mm to 17mm) scleral lenses sometimes decenter temporally. He has found that, notably in the right eye more than the left, the sclera is more elevated nasally; therefore these lenses tend to be embedded nasally and the lens will tend to shift slightly temporally.
9 Dr. Stephanie Woo reported on a multi-center study coordinated by Dr. Michaud that compared comfort and vision of a soft toric lens design versus a small (14.3mm) scleral lens design, with subjects wearing each lens design for a one-month period. All subjects were initially wearing soft lenses, but at the conclusion 52 percent wanted to wear scleral lenses. In addition, the initial comfort was equal between the two modalities, and 75 percent preferred the vision of the scleral lens design. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #208.
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 firstname.lastname@example.org.