Scleral lenses are mostly utilized for patients who have irregular corneas, but can be an option for normal corneas. Glasses are often the first consideration for correcting refractive error, however contact lenses can improve cosmesis and visual comfort by reducing magnification effects caused by the vertex distance in glasses in high ametropia and anisometropia.

Though many patients can successfully wear soft contact lenses (SCLs), sometimes they do not provide satisfactory vision and/or comfort due to residual astigmatism, excessive movement, or rotational instability. In these cases, specialty lenses including hybrids, corneal GPs, or sclerals may be considered.

All three options provide the excellent optics of rigid GPs. Corneal GPs tend to cause initial lens awareness and require adaptation to achieve adequate comfort. Hybrids improve initial comfort with the addition of a soft skirt to reduce upper lid and lens edge interaction, but they may tighten over time. Sclerals also reduce this lid-lens interaction, while additionally providing a fluid reservoir that bathes the cornea in saline, offering a solution for patients struggling to adapt to other designs.

Sclerals for Everyone?

If sclerals can fix all of these problems, this begs the question: Why not fit all patients in scleral lenses? The reasons may include fitting time, handling, higher cost, and health considerations.

First, sclerals often require more chair time and higher cost to fit. Though innovative technology using scleral topography or impression-molding can reduce chair time, lenses still may not always fit predictably, and require further modification.

Second, education on care and handling is another hurdle. Application and removal are performed using plungers and non-preserved saline is required to fill the lens during application. The process can take longer to learn than other designs.

Finally, sclerals fit differently from other contact lenses, so practitioners should consider the potential risks of prolonged wear time. Sclerals land near the episcleral venous outflow system of the eye, and it has been hypothesized that they may affect aqueous outflow and increase intraocular pressure (IOP). While IOP has been shown to return to baseline after lens removal, it is difficult to reliably measure IOP while the lens is on the eye (Nau et al, 2016). Closer monitoring is warranted in patients who have conditions like glaucoma.

Sclerals also create a mild suction force under the lens, which can lead to conjunctival prolapse (Walker et al, 2016). If left over time, the conjunctiva can adhere to the cornea with associated vascularization and scarring of the limbus and peripheral cornea (Walker et al, 2016). While the long-term implications of prolapse are not well understood, it is best to prevent damage to areas where limbal stem cells reside.

Another consideration is potential hypoxia, which can result in corneal edema or vascularization. Sclerals induce about 1% to 1.5% swelling during open-eye wear, which is only about one-third of physiological corneal swelling (4% to 4.5% under closed-eye conditions) (Kim et al, 2018). Although tear exchange is minimal under a scleral, the cornea receives oxygen through the lens and fluid reservoir and most hypoxic complications are avoided so long as lens thickness is not excessive, a high-Dk material is used, and overnight wear is avoided. The long-term effects of all these considerations are still not fully understood, and ongoing research will help us better comprehend their implications.

Weigh the Pros and Cons

Since contact lens wear itself increases risk of microbial keratitis, decreasing risk factors can reduce sight-threatening infection, particularly avoiding overnight wear and practicing good hygiene (Stapleton and Carnt, 2012). Given the complex wear and care parameters of sclerals, patient education is essential. For the most part, with proper compliance, sclerals are a great option without significant complications for patients with normal corneas who cannot wear other lens designs. CLS

References

1. Nau CB, Schornack MM, McLaren JW, Sit AJ. Intraocular Pressure After 2 Hours of Small-Diameter Scleral Lens Wear. Eye Contact Lens. 2016 Nov;42:350-353.
2. Walker MK, Bergmanson JP, Miller WL, Marsack JD, Johnson LA. Complications and fitting challenges associated with scleral contact lenses: A review. Cont Lens Anterior Eye. 2016 Apr;39:88-96.
3. Kim YH, Tan B, Lin MC, Radke CJ. Central Corneal Edema with Scleral-Lens Wear. Curr Eye Res. 2018 Nov;43:1305-1315.
4. Stapleton F, Carnt N. Contact lens-related microbial keratitis: how have epidemiology and genetics helped us with pathogenesis and prophylaxis. Eye (Lond). 2012 Feb;26:185-193.