Is This the New Norm?
Is This the New Norm?
Are Scleral Lenses the New Norm for Irregular Corneas?
By Mile Brujic, OD, & David L. Kading, OD, FAAO
Scleral lenses have become a mainstay in many of our offices for many types of patients. Although we utilize them for myriad conditions, sclerals certainly have an important place for irregular cornea patients.
When managing irregular corneal shape resulting from surgery, trauma, or disease, we traditionally think of corneal GP designs for the clarity of vision that they provide. If a patient can adapt, GP lenses can provide both comfortable wear and clarity of vision. However, there are always some patients who cannot adapt and are not able to complete the transition to the corneal GP modality.
Traditionally, such patients have had to resort to either wearing soft toric lenses or glasses; in more severe situations, they have had to undergo surgery. With the introduction of a new era of materials and lens designs for irregular cornea patients, we ask: Have scleral lenses become the new norm for irregular cornea patients?
Sclerals Versus Corneal GPs
So, how do scleral lenses compare with corneal GPs?
Adaptation Scleral lenses tend to provide a surprisingly comfortable initial wearing experience. A scleral lens rests on the conjunctiva and underlying sclera, vaulting the highly sensitive cornea. The lens diameter is significantly larger compared to its small-diameter corneal GP predecessor, and thus the edge of the lens will have little to no interaction with the lid.
Figure 1. Checking scleral lens clearance.
Fitting Process The size of scleral lenses tends to deter many practitioners from fitting them. Rather than focusing on the keratometry readings (which measure the central 3mm to 4mm of the cornea) as you would for a standard GP corneal lens, scleral lenses challenge you to think differently about the fitting process. The key components are central and limbal clearance (Figure 1), and proper scleral landing characteristics.
Parameter Availability Like corneal GP lenses, spherical scleral lenses can mask most of the irregular cylinder that patients have. However, approximately 20% of the scleral contact lenses that we order have some cylinder, either in the lens power to compensate for uncorrected astigmatism or in the scleral landing zones to optimize fits for those who have significant toricity in their scleral profile.
Lens Fit Scleral lenses vault the cornea, so they eliminate the challenges that can be introduced when a corneal GP lens rests along an irregular cornea.
Although contemporary scleral designs and GP materials have offered significant advantages for some of our most challenging patients, we should be cognizant of the clinical challenges that exist with this modality. Scleral lenses are certainly a viable option and continue to play an increasingly important role in our fitting strategies, including for irregular cornea patients. CLS
Contact Lens Spectrum, Volume: 29 , Issue: February 2014, page(s): 44