Prescribing for Presbyopia
Scleral Lens Multifocals: A Good Option for Dry Eye?
By Craig W. Norman, FCLSA
GP lenses larger than 12mm have been prescribed for patients who have severe dry eye relating to medical conditions such as Stevens-Johnson syndrome, chronic ocular graft versus host disease, Sjögren's syndrome, Herpes zoster, Herpes simplex, and other conditions. They can also be used after certain types of eye surgery or corneal grafts.
But what about their use for dry eye syndrome? Or how about contact lens-induced dry eye, which may be the No. 1 reason for the large dropout rate? The rationale for scleral lenses reducing dry eye symptoms is quite simple. The lens is usually filled with sterile, non-preserved saline solution, which keeps the eye “wet” for long periods of time. The saline solution does not contain surfactants, disinfectants, or preservatives that may cause dry eye symptoms. The lack of lens movement and the non-hydrophilic lens material reduces surface dehydration.
New Designs Target Presbyopia
Over the past five years, U.S.-based contact lens manufacturers have developed a wealth of interesting scleral lens designs to correct vision and provide comfort in medically related situations. This year, many of these same manufacturers will be offering similar designs as an alternative choice for managing dry eye that also provide presbyopic correction.
Optically, these multifocal sclerals are similar to multifocal soft lenses. Mostly center-near optics will be employed, although it is possible that this will be combined with a distance-biased lens in the fellow eye. The add zone will be approximately 2.0mm, adjustable larger or smaller depending on pupil size and dynamics. As with soft multifocals, positioning of this zone will be critical to visual success and must be closely aligned to the line of sight.
Pros and Cons of Scleral Multifocals
There are definite benefits for this design, in particular improved comfort for contact lenswearing dry eye patients and some ability to position the near portion in a patient's line of sight.
Regarding challenges, one that I foresee is the selection of lens diameter. Sclerals for medical indications have been getting larger, with diameters of 18.0mm or more becoming more common. While this may improve some fitting characteristics, it also tends to cause slight decentration, which may create optical issues with a small central near zone. On the other hand, if we choose a much smaller lens, we may not be able to achieve the same fit and comfort benefits.
Another concern is the patient response to a large GP. Most medical scleral lens wearers have overcome their initial wariness of handling and wearing a lens of this size, but what about patients who want contact lenses only for cosmetic use?
Another potential issue is long-term wear of scleral lenses in a “normal” eye. Do we really know enough about the effects of these lenses on corneal and limbal health to be suggesting them for dry eye syndrome, contact lensinduced dry eye, and presbyopia? Time will tell if this is a healthy long-term solution in these cases. I hope so, as it will be a helpful alternative to aid some of our presbyopic dry-eye patients. CLS
|Craig Norman is director of the Contact Lens Section at the South Bend Clinic in South Bend, Indiana. He is a fellow of the Contact Lens Society of America and is an advisor to the GP Lens Institute. He is also a consultant to B+L. You can reach him at email@example.com.|