Scleral lenses are wonderful; however, here are three intrinsic factors that limit their use in certain cases.

1. Sclerals’ ability to be tinted/painted is limited, and their safety profile is unknown. Scleral lenses are selectively tinted in the dry state by using a modified pad printer and then curing or baking the pigment at high temperatures to seal in the color; this allows a very specific pattern to be incorporated onto the scleral lens surface. The lenses can be further treated with plasma or polyethylene glycol (depending on the lab). Some labs can permanently distribute pigment into the lens matrix so that the pigment is not raised on the lens surface. Regardless of the method used to achieve the final tinted look, the addition of layers of pigments contributes to overall lens thickness and can potentially impact oxygenation to the cornea. In a patient who has congenital microcornea, aphakia, and aniridia—requiring a high-plus lens power (for improvement of quantity of vision) and a prosthetic iris print (for improvement of quality of vision)—a custom soft lens that is made 2mm-to-3mm larger than the size of the cornea with an opaque iris ring is an appropriate fitting option.
2. Sclerals exert a force when they land on the ocular surface. Even a best-fit scleral lens will leave some indentation on the eye. If you remove lenses from established scleral lens wearers during follow-up visits and stain the eye with sodium fluorescein (NaFl), this indentation ring can be visualized. Stain uptake over a filtering bleb (Figure 1) or scleral sutures following trauma is evidence of injury to the underlying ocular surface epithelial cells. If adequate vault over these structures cannot be achieved or an edge/haptic vault is required that leads to a bubble when the patients blink their eyes, a custom soft lens can be lathe cut and fitted to better protect the delicate conjunctiva to prevent erosion.

   

3. Even at a minimal lens center and fluid reservoir thickness, sclerals can induce hypoxic changes in compromised corneal tissue. A thin scleral lens (~250 microns) made of hyper-Dk material and with a 100-to-200 micron fluid chamber vault can induce corneal changes in eyes that have undergone one or more corneal transplant surgeries (Figure 2).

   

Hypoxia can lead to the formation of epithelial bullae that can be scary when first observed. At this point, it is imperative to co-manage with the patient’s corneal surgeon to closely watch for possible rejection of graft tissue. However, it is not uncommon to notice these fluid-filled blisters regress once scleral lens wear is discontinued or decreased. If the goal for these patients is to be alleviated of pain and discomfort, a custom soft lens can serve as a healthier barrier between the undersurface of the eyelids and the delicate corneal tissue.

In Conclusion

While superior visual outcomes may result with sclerals in complex corneal cases, custom soft lenses may be a healthier option for a long-term solution in some cases. CLS