Article

THE SCLERAL LENS VAULT

VAULTING SCLERAL OBSTACLES

A critical aspect to scleral lens design is matching the back surface of the scleral lens haptic with the individual eye being fit. Scleral shape can be spherical, toric, or irregular. Surface irregularities may be due to pingueculas, which are located either nasally or temporally from the corneal limbus. Pingueculas are associated with outdoor activity, age, and contact lens use (Mimura et al, 2010; Viso et al, 2011). A study of Spanish individuals over age 40 showed a prevalence of pinguecula of 47.9% (Viso et al, 2011).

Practitioners routinely fit soft lenses for patients who have pingueculas, and unless inflamed, they often don’t affect wear because the soft material drapes over their elevated surface. The majority of scleral lenses that are fit for specialty lens applications range from 15mm to 17mm in diameter (Harthan et al, 2017) and, therefore, are likely to interact with pingueculas. While scleral lenses often will fit over pingueculas that have low elevations without consequence, pingueculas with a moderate-to-high elevation can significantly affect fit. Impingement of the pinguecula will not only create irritation, but it will also lift the edge, resulting in reduced comfort and a potential entrance for the intake of reservoir debris. Additionally, this can cause the lens to decenter, affecting both fit and vision.

Troubleshooting

Consider designing a scleral lens that is smaller in diameter to avoid contact with the pinguecula. The limiting factor is the patient’s corneal diameter. Larger corneas require larger-diameter scleral lenses to achieve clearance. Another option is to incorporate an edge lift designed to vault the pinguecula. The location, axis, width, and height of the pinguecula need to be accurately communicated to the lab consultant. The lens will have to be rotationally stabilized with double slab-off prism, back-surface toricity, or a multi-meridian back surface. The patient should apply the lens in its proper rotational position using lens markings for orientation.

Case Example

A 44-year-old patient who had previous hyperopic laser-assisted in situ keratomileusis (LASIK) surgery reported with decreased near vision. Examination showed a significant paracentral Salzmann’s scar of his left cornea and best-corrected vision of 20/30. The patient was fit with a near-powered scleral lens for his left eye, as his uncorrected right eye was 20/20 at distance. Slit lamp examination and corneo-scleral topography revealed a significant nasal pinguecula (Figure 1). A sagittal height plot (Figure 2) was used to design the back surface haptic. The final lens (Figure 3) has a customized edge lift that vaults the nasal pinguecula and front-surface toricity to correct residual astigmatism. The lens is rotationally stabilized with a back-surface-toric design. CLS

Figure 1. Scleral elevation map OS. The nasal red spot highlights the pinguecula.

Figure 2. A sagittal height plot used to design the back surface haptic. The peak of the pinguecula is at 189°.

Figure 3. Scleral lens with an edge lift that vaults the pinguecula.

For references, please visit www.clspectrum.com/references and click on document #262.