Eyeworld

EW CORNEA 36 November 2017 vault the cornea and rest entirely on the limbus and sclera or rest entirely on the sclera, or extend for 2 mm beyond the limbus. Another crite- rion for scleral lenses could include tear exchange under the lens. The brand is not as important as the characteristics of fit, especially in an eye with underlying disease or compromise of the endothelium or epithelium, Dr. Jacobs said. In the short term, some of these patients do well with thera- peutic soft lenses, first on extended wear and then converted to a daily wear basis to lower infection risk. For long-term need or if surface issues continue despite the use of therapeutic soft lenses, Dr. Jacobs views conversion to scleral lenses as warranted. Lens options Not all scleral lenses are equivalent. Corneo-scleral lenses and mini-scler- al lenses are marketed as scleral lenses, Dr. Jacobs noted. "The definition of a scleral lens is evolving and may include diame- ter and/or aspects of fit," Dr. Jacobs said. For example, definitions might include the need for the lens to For physiologic function, it is important that there be fluid venti- lation, which is tear exchange under the lens, and that is more likely to be achieved in lenses 17.5 mm or larger, Dr. Jacobs said. Very steep cones may require diameters of 19.5 mm or greater to allow for fluid ven- tilation and to avoid apical touch and excess haptic compression. Other lenses In comparison, hybrid lenses are small, hard lenses with a soft skirt. A hybrid lens "has the advan- tage of the hard lens in the center with the soft skirt so it's more com- fortable on the outside," Dr. Jeng said. "This lens can be used for ecta- sia but it cannot be used effectively for ocular surface disease patients because there's no reservoir to bathe the surface in. The scleral lens has a huge advantage over this lens in that setting." Dr. Patel noted scleral lenses are entirely composed of PMMA. Addi- tionally, they vault the cornea and limbus and are comfortable because of their large shape (the edge is un- der the upper eyelid), though they can collect debris in the pre-corneal tear film, which often requires clean- ing during the day. "Scleral lenses provide better vision than soft lenses for irregular astigmatism," Dr. Patel said. "Soft lenses are comfortable and conve- nient. RGPs give the best vision but perhaps less comfort than scleral lenses in very irregular corneas." Ophthalmologists should be aware that therapeutic scleral con- tact lenses exist and most can be fit for a modest price, Dr. Patel said. "Be familiar with the indications because they can prevent significant morbidity for many patients with ocular surface disease," Dr. Patel said. Ophthalmologists should work with optometrists who are specif- ically trained to fit scleral lenses because they are tricky to fit, or the ophthalmologists need to be trained themselves, Dr. Jeng said. "They are not straightforward, and they need to be cared for like daily contact lenses. Physicians need to emphasize that to patients," Dr. Jeng said. EW Editors' note: Dr. Jacobs has financial interests with BostonSight. Drs. Jeng and Patel have no financial interests related to their comments. Contact information Jacobs: djacobs@bostonsight.org Jeng: bjeng@som.umaryland.edu Patel: patel.sanjay@mayo.edu Understanding continued from page 34 OPHTHALMOLOGY'S ONLY READY-LOADED IRIS EXPANDER Made in the U.S.A. DIAMATRIX ® featuring by Visit Diamatrix.com or call us at 800.867.8081 to trial the "the most elegant ring on the market". READY-LOADED

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