Scope/Abstract This document specifies the methods of testing the physicochemical properties of contact lens materials. Ophthalmic optics - Contact lenses - Part 4: Physicochemical properties of contact lens materials Alternatively, lens diameter can be decreased to lessen the impact of toricity.Part B: Supplementary Information Sheet (SIS) In these cases, switching the patient to a lens with a toric haptic can help with centration issues. Typically, he adds, this can be recognized through the observation of “tight fit/compression along the horizontal meridian and a looser fit in the vertical meridian.” “Unlike a corneal GP-which will often ride high with the lid-the scleral lens will instead settle inferiorly,” Dr. Jedlicka explains, “the lens will not be able to sit on that meridian.” Displacement often results. “If the sclera is flatter along the 3 and 9 o’clock meridian,” Dr. DeNaeyer says.Īside from excessive lens vault and lens mass, another potential cause of inferior decentration could be toricity of the sclera. “The decrease in mass will often help to minimize decentration,”Dr. Jedlicka suggests trimming the lens thickness, which would lower “the effect of gravity on the lens as well as the lid pressures on the lens.” However, make sure that decreasing the lens thickness does affect other aspects of the fit or cause other problems, such as flexure.Īlternatively, try a small-diameter scleral lens such as a 16mm mini-scleral. Reducing the lens mass could also help ease discomfort and decentration. Switching the patient to hybrid lenses or specialty soft lenses may also aleviate the problem. A daily disposable is best suited for this method, and those made of silicone hydrogel in particular should be considered to achieve the greatest possible oxygen transmissibility. DeNaeyer, is to piggyback the scleral lens on top of a soft lens, which acts as a cushion between the area of bearing and the lens. So, “decreasing the vault will reduce the lid pressures that drive the lens lower.” Of course, he adds, this can only be done if there is already more than enough vault to begin with.Īnother possible method, says Dr. “The more the lens lifts away from the eye, the greater the lid pressure on the lens,” says Jason Jedlicka, OD, from the Cornea and Contact Lens Institute of Minnesota in Edina. On the other hand, make sure you don’t have too much vault. This will take lens bearing off of the superior nasal cornea,” he says. First, “increase the overall vault of the lens by steepening the base curve and/or mid-peripheral curves. DeNaeyer suggests several solutions to help alleviate the irritation. Also, because the patient is complaining of discomfort with a decentered scleral lens, it’s likely that lens bearing on the superior nasal quadrant may be causing epithelial erosion, Typically, erosion will show up as staining under slit-lamp examination after lens removal.ĭr. “Inferior lens decentration could be attributed to lens mass and bearing of the upper lid,” explains Greg DeNaeyer, OD, clinical director of Arena Eye Surgeons in Columbus, Ohio. The lens decenters inferiorly and temporally in this patient.Ī: Before changing lenses, you need to figure out the reason for the decentration, which is likely one of these two causes: the lens may have excess mass or vault, or the patient’s sclera is toric. The superior nasal tear film thinning (dark fluorescein) appears due to higher elevation superiorly and nasally. Any suggestions for the next lens change? It seems to be creating some comfort issues (awareness and reduced wearing time). Q: I recently fit a large-diameter scleral lens (18mm) on a moderately severe keratoconus patient with adequate central clearance, but the lens decenters inferiorly.
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