Designing Lenses to Work Around Scleral Obstacles
By Gregory W. Denaeyer, OD, FAAO
The relatively larger diameter of scleral or hybrid lens designs allows them to fit out onto the scleral conjunctiva. Typically, success or failure of these lens types hinges on an even bearing distribution on the sclera that avoids excessive compression or edge lift. Occasionally, anatomical obstacles that are located on the scleral conjunctiva have the potential to negatively impact the fitting of these lens designs.
The Most Common Culprit
The most common scleral obstacles that you may encounter are pingueculae. Most pingueculae, which can reside nasally and/or temporally on the bulbar conjunctiva a few millimeters from the limbus, are shallow enough that they do not affect the fit of contact lenses. Practitioners routinely fit soft, hybrid, and scleral lenses on the surface of these mild pingueculae without negative sequelae. However, a pinguecula that has significant elevation can affect a GP scleral fit.
The firm nature of scleral GPs can cause patients significant irritation if the lens edge bumps into the pinguecula, or their rigidness will prevent an acceptable fit if an elevated pinguecula lies beneath the haptic. If this is the case, you may want to consider a corneal GP, soft specialty design, or hybrid design (Figure 1). Alternatively, a notch can be beveled out of a scleral lens, which will allow it to bypass the pinguecula.
Figure 1. Soft skirt of a hybrid lens abutting the edge of a pinguecula.
A conjunctival bleb is the second most common scleral obstacle that you might encounter during a specialty fit. Conjunctival blebs, superiorly located, most commonly result after trabeculectomy that is performed on glaucoma patients who have failed with medications and laser surgery.
If the bleb is relatively flat, a specialty soft lens may be able to successfully drape over the bleb without negatively affecting the fit. A corneal GP that has an interpalpebral fit may work if the lens will stay centered. A GP lens that decenters superiorly can be damaging to the bleb. As well, these lenses can eject from the eye if they get squeezed between the bleb and the lower lid.
The most effective way to manage patients who need a GP lens(es) is by fitting them with a scleral lens that has a beveled notch (Figure 2). Generally, diameters between 13mm to 15mm work best because larger diameters will require deeper notches that are more likely to induce air bubbles. The notch should be wide enough so that it doesn't constrict the bleb, and the scleral lens should have a semi-sealed fit without movement. Instruct patients to put the lens on like a puzzle piece so that the notch matches up with the bleb. Carefully monitor patients for mechanical injury to the bleb, which could result in a leak or blebitis.
Figure 2. Scleral lens with a beveled notch on eye with a conjunctival bleb.
Be Creative, Successful
Creativity in lens selection and design will help you successfully fit patients who present with scleral obstacles. CLS
|Dr. DeNaeyer is the clinical director for Arena Eye Surgeons in Columbus, Ohio, and a consultant to Visionary Optics, B+L, and Aciont. You can contact him at firstname.lastname@example.org.|