Scleral lenses have gained popularity in the last decade. From a lens with limited viability for over 100 years to the fastest growing segment of the gas permeable lens market, scleral lenses have come a long way. Yet there is still some hesitance on the part of many practitioners to fit or recommend them, and some misconceptions about scleral lenses may be holding back individuals who might otherwise be offering them to the benefit of many patients.
I wanted to explore what I felt were five myths about scleral lenses and how getting past these myths might help some practitioners begin to embrace sclerals and incorporate them into their practices.
Myth 1: Sclerals are hard to fit
Many practitioners look at the size of a scleral lens and assume that it must be hard to fit. Practitioners already feel like fitting corneal gas permeable lenses is challenging enough, and that a lens that is significantly larger can be only more complicated to fit. This is simply a myth.
Scleral lenses do require a slightly different way of thinking than other lenses. Instead of thinking in terms of curves, it is helpful to think in terms of depth or clearance. Once we clear that hurdle, fitting sclerals can seems quite simple.
Fitting scleral lenses is a three-step process, and following this process each and every time will lead to success in a majority of patients.
Step one. Choose a lens with enough depth to clear the cornea entirely. Scleral lenses by definition do not touch the cornea. If you put a lens on the eye that touches the cornea, it is simply not deep enough. Moving to a lens with greater depth will eventually lead to a lens that clears the cornea entirely. Once you have achieved that clearance, you can get more specific and work on getting the exact amount of clearance you desire. This amount of clearance will be part of the fitting guide for the lens design you use, it but should be somewhere in the neighborhood of 150-450 µm.
Step two. Ensure the lens clears the limbus. A scleral lens that bears on the limbus will eventually lead to problems with dryness, redness, and discomfort. You can tell if there is limbal clearance by looking for the fluorescein under the lens to extend beyond the limbal area (Figure 1). If you do not have limbal clearance, it is as simple as asking your lab consultant to make the lens with more clearance.
Step three. Make sure the lens bears evenly on the sclera. Thankfully, the sclera is a very forgiving layer of tissue. Lenses that are too flat on the edge will have edge standoff. Lenses that are too steep on the edge will compress the blood vessels of the conjunctiva and create blanching. Lenses that are too flat or steep in one meridian only will require a toric landing zone. Modifying the landing zone is usually as easy as asking for steeper, flatter, or toric landing curves.
Fitting a scleral lens is actually quiet straightforward because the sclera is more forgiving than the cornea. If the idea that fitting scleral lenses is difficult is what is holding you back, you are falling prey to Myth 1.