Scleral Lenses for Healthy Eyes – A World of Opportunities
BY LANGIS MICHAUD, OD, MSC
At the end of a recent lecture, I was about to leave the room when one of my students came forward. “Sorry to keep you late, but you told us we have to consider scleral lenses as the future of the contact lens market. I’m struggling to see that happening anytime soon. I don’t believe that, at a given point, they will replace daily disposable lenses. Did I miss something? Are there that many patients with keratoconus?” The following is a summary of my answer.
Busting the myth
In the past, scleral lenses were mostly fit to treat ocular surface disease and visual correction for irregular corneal astigmatism. However, with the recent evolution in designs and manufacturing processes, and considering their main characteristics, it would be a mistake to keep them as niche products, prescribed only by a few contact lens experts. Fortunately, the trend is headed in a different direction. The rebirth of the scleral lens modality is due in part to proactive practitioners who are thinking outside the box and looking to explore other patient conditions that can benefit from scleral lens technology. It is time to bust the myth that scleral lenses are specialty contact lenses used only with special corneas. They are, in fact, becoming mainstream.
Scleral lenses – what can they offer?
This modality can offer many different positive outcomes compared with other ones, especially in fixing two major issues that often lead to dropout: vision and comfort.
In general, scleral lenses have been known to help optimize visual acuity. They are made of rigid gas permeable (GP) materials known to be optically superior to any other type of material. Scleral lenses help to lower high-order aberrations through optical correction and better compensation of surface irregularities.
Also, scleral lenses are designed with a larger optic zone that doesn’t interfere with a larger pupil diameter. Consequently, fewer halos and less glare are experienced due to lighting conditions or when driving.
Another important aspect is that scleral lenses move minimally once stabilized on the ocular surface. To provide good visual acuity, they also have to be well centered. This is easier to achieve with smaller diameter scleral lenses.
Given the conjunctival anatomy and gravity, larger scleral lenses tend to de-center inferior (downward) and temporal, leading to a misalignment between the visual and optical axis, which contaminates visual perception. This element becomes crucial when correcting for presbyopia. Smaller diameter scleral lenses (15.5 mm or less) are usually preferred for normal corneas and healthy eyes.
Scleral lenses can also help improve the contact lens experience by enhancing short- and long-term comfort. First, scleral lenses don’t touch the cornea or limbus, which are two of the most sensitive parts of the body. When blinking, they also limit lens-to-lid interaction, which is the main cause of discomfort with small diameter GP lenses.
Higher lens coefficient of friction is thought to be associated with contact lens discomfort. Roflufocon A and E, and Hyfocon A materials are characterized by a very low wetting angle. This implies that the tear film can spread easily on the surface with minimal surface tension. Consequently, this lowers the amount of deposits on the lens surface, at least in healthy eyes without meibomian gland dysfunction and blepharitis. Lens moisture can also be improved with plasma treatment. Moreover, if hydrogen peroxide is used as a care regimen as directed without rubbing of the lens, plasma treat- ment will remain unaltered for several months. With an abrasive contact lens cleaner, plasma treatment may last 30 to 45 days. In my opinion, the new Hydra-Peg surfacing technology can also be considered as a good alternative to improve lens resistance to deposits. Finally, scleral lenses never dehydrate, and the presence of the post-lens fluid reservoir helps to keep the ocular surface moist during all wearing hours, which enhances patient comfort.
To have a patient switch from soft contact lens wear, or to consider fitting scleral lenses on a naïve patient, we must identify a benefit or an unmet need that will be fulfilled with scleral lenses. The risk/benefit (R/B) ratio should be evaluated for every patient.
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