Scleral Lens Primer: Part 2
By Edward S. Bennett, OD, MSED, FAAO, & Christopher Gilmartin, OD
Large-diameter GP designs can prove challenging to new wearers who need to master handling these lenses. Following are some recommendations to help optimize success with this process.
For the initial fitting evaluation, fill non-fenestrated scleral lenses completely with an appropriate media and add fluorescein from a strip to the filled bowl. Use sterile non-preserved ophthalmic saline to fill the bowl for application. An alternative is an isotonic, non-preserved artificial tear. Do not use any fluorescein dye that incorporates an anesthetic or preservative.
The lens can be supported on a large DMV scleral cup (or equivalent). It can also be balanced on a “tripod” made up of the thumb, middle, and index fingers, but this requires more dexterity. The patient's face should be parallel to the ground, and the lids must be retracted and well-controlled. Direct the patient to look straight down toward the floor. After preparing the scleral lens and mounting it on the DMV plunger, retract the patient's lids and raise the lens onto the eye in one continuous motion. Once the lens has been gently positioned on the eye, release the lids before lowering the support plunger. Additional application tips include:
● If seated, cover the patient's lap with paper towels before application because some of the media will overflow and could stain clothing.
● Have a tissue ready for the patient after application.
● Have the patient retract his upper lid while you retract the lower lid or vice versa.
● Rotate the patient's chair to allow for easier positioning if needed.
If you observe a bubble after applying a non-fenestrated mini-scleral lens, it is likely an insertion bubble. Very small bubbles are inconsequential unless they develop after a bubble-free application, which may indicate a peripheral fit that is too loose. If a bubble forms immediately after application, remove and reapply the lens. To avoid bubbles, apply the lens in one continuous motion. Common causes for insertion bubbles are under-filling the lens before application and accidental contact with lids and/or lashes during application.
Fenestrated lenses will often yield bubbles if the fit is not appropriate. It is becoming more common for practitioners to use non-fenestrated lenses as they are much more forgiving during the fitting process.
It is normal and expected for the lens to be somewhat suctioned onto the eye, particularly after settling. The suction must be loosened before lens removal. Gently pushing on the inferior periphery in a repeated motion for several seconds can be effective. With the superior lid well controlled, the inferior lid can be used to lift the lower portion of the lens away from the eye. The lens can then be gently lifted from the eye while using the upper lid to assist in pushing the lens in a downward motion over the lower lid.
Alternately, while the patient looks down, the superior edge of the lens can be lifted by controlling the upper lid. A medium DMV suction cup can also be effective for scleral lens removal. If using this method, moisten and gently squeeze the suction cup, then apply it to the inferior lens periphery. Pull the DMV “down and out.” That is, the removal force should be directed perpendicular to the lens surface, not parallel to the visual axis. Superior lid control is very important to ensure that the patient does not close the lid during removal.
Finally, applying an appropriate rewetting drop just prior to application can be helpful, particularly when using a DMV suction cup to remove the lens. CLS
Dr. Bennett is assistant dean for Student Services and Alumni Relations at the University of Missouri-St. Louis and is executive director of the GP Lens Institute. You can reach him at firstname.lastname@example.org. Dr. Gilmartin is a part-time assistant clinical faculty member in the Department of Cornea and Contact Lenses at the University of Missouri-St Louis College of Optometry. He spends the balance of his time in a specialty private practice setting. Contact him at email@example.com.