Interest in scleral contact lens fitting has increased dramatically over the last few years, and it is not unusual for a practitioner new to specialty contact lenses to start learning and fitting with sclerals. While scleral lenses are certainly an important modality to consider for many patients, scenarios do arise in which a corneal GP (CGP) lens may be a better option.
Patients who have significant endothelial cell loss or who are at risk for ongoing decreases in endothelial cell density, such as those who are post-penetrating or endothelial keratoplasty (Price et al, 2016), need to be monitored closely with GP lens wear (Alipour et al, 2019). And, sclerals may be contraindicated altogether if the endothelial cell count is excessively low. As the instrumentation needed to evaluate the endothelial cell layer this closely is not always present in many smaller practices, a corneal GP lens may be the safer modality to pursue.
Hypoxia If corneal hypoxia is a concern, scleral lens wear may again be contraindicated. Michaud et al (2012) describe a significant reduction in oxygen transmissibility to the cornea depending on factors such as lens thickness, material Dk, and post-lens tear thickness. Eyes that show signs of hypoxia such as neovascularization (Figure 1) or corneal edema may need to be fit in lenses that allow for maximum tear exchange. A CGP lens is a great option if it can be fit to avoid bearing on areas that might be aggravated by lens movement. Practitioners must be aware, however, that similar clinical signs can also present in patients who have ocular surface disease that might conversely benefit from the protection of a scleral lens prosthetic.
Intraocular Pressure (IOP) Even though the relationship between IOP and scleral lens wear is still up for debate, it is prudent to use caution when fitting this modality on a patient who has glaucoma or ocular hypertension. This is particularly important if there is a drainage bleb or other surgical area that may negatively interact with scleral lens haptics or if the scleral lens fit is tight enough in the periphery to compress ocular structures and induce IOP elevation (Vincent et al, 2017). A corneal GP lens can usually be fit to avoid both of these potentially harmful situations.
Handling Some patients might find smaller CGP lens diameters easier to apply and/or remove. If specialty lens fitters cannot reach for a CGP alternative, these patients may end up with only inferior spectacle correction.
Cost While perhaps not seemingly as critical to a fitting practitioner, the lower price tag often associated with CGPs—compared to scleral lenses and other specialty modalities—can be very important to a patient. Even if the benefits of a scleral or other lens are well worth considering, a difference of hundreds or thousands of dollars may place these lenses out of reach for many patients.
As the interest in sclerals continues to grow, the need for practitioners to fit CGP lenses remains. It is well worth the time of new specialty lens fitters to gain practice and expertise in CGPs. As a specialty lens practice grows, the need for many different types of modalities and options will arise in this diverse and unique patient base. CLS
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