Contact Lens Design & Materials
Scleral GPs: More Indications?
By Neil Pence, OD, FAAO
Scleral lenses have been around for some time, but the revival of this lens type in the past five years has been remarkable. Modern manufacturing technologies, more oxygen permeable materials, and continued design innovation and refinement have combined to provide an outstanding option for many patients. Perhaps it is time for a second look at who benefits from scleral lenses.
Correcting Irregular Corneas
The prevailing opinion that “correcting the irregular cornea to restore vision is the main indication for fitting scleral lenses” was well stated by Eef van der Worp, BOptom, PhD, FAAO, FIACLE, FBCLA (2012). When considering all that “irregular cornea” may encompass, a large number of conditions might benefit from scleral lenses. Corneal ectasia constitutes many of the irregular corneas seen in daily practice.
A second group of irregular corneas are those in postsurgical patients. Corneal irregularity secondary to refractive surgery, including intrastromal rings or keratoplasty, is certainly helped by the vision correction that scleral lenses provide. An added benefit of vaulting the cornea entirely is in eliminating bearing on fragile postsurgical corneas. Other corneal irregularities result from stromal scarring, which may occur from penetrating injuries or corneal disease. This may be due to severe exposure keratitis secondary to ocular surface disease or possibly to lid abnormalities.
In extreme ocular surface disease, the function of a scleral lens is to protect the cornea as much as it is to correct vision. This is true in some recurrent erosion cases as well as in a number of severely dry eye conditions. The ability to maintain a fluid reservoir under the lens serves to protect the cornea from drying. Lack of scleral lens movement also protects against mechanical pressure or rubbing on the cornea.
Who Else Could Benefit?
As lens designs have improved, it may be time to question whether the previous list of indications is too narrow. Would this not be a good option for patients who do not have corneal irregularities or do not need the protection benefits that sclerals provide? Who among our “normal” patients might be candidates for sclerals if we broaden our indications?
Assuming vision correction is matched by corneal GP lenses, the main benefits of scleral lenses to patients who have normal corneas might be: comfort, stability and centration, and the lack of a significant tear pump. Because the lid never interacts with the lens edge and there is essentially no lens movement, scleral lenses are often more comfortable than corneal lenses are. This benefits patients who are less tolerant to corneal GPs, perhaps have tighter lids, or are occasional wearers not well adapted to GPs. I doubt that many practitioners offer scleral lenses to patients who wear contact lenses for weekend activities only, but the quick adaptation and lack of movement are assets for various physical activities.
Similarly, athletes in general can benefit from the crisp vision of a GP with excellent stability and no lens displacement or loss. The vision is stable with blinking, eye movements, or jarring.
Windy or dusty environments are much less of a concern if debris is not pumped under their lens.
One particular college baseball player comes to mind. While 20/20 in soft toric lenses, he preferred the acuity from his GPs. Problems with dust and the occasional lens displacement were eliminated with scleral lenses.
An Option for More Patients
The ability to help patients who have irregular corneas and to protect the cornea in certain cases has been a wonderful scleral lens application. It may be time to offer this modality to “normal” patients, and look for manufacturers to begin targeting them, too. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #203.
|Dr. Pence is the associate dean for Clinical and Patient Care Services, Indiana University School of Optometry in Bloomington, Indiana. He is also a consultant to B+L, J&J Vision Care, and Alcon. You can reach him at email@example.com.|