Fitting scleral lenses can be a challenge for even the most seasoned practitioner. Patient expectations can up the ante of complexity, when it’s a new wearer with a high expectation of comfort and adaptation, “promised” visual acuity post-laser procedure, or completion of the fit in a limited time frame. Choosing a lens design that’s easy and predictable to manipulate can help make the difference when the prescriber is given these demands.

Case Description

A 20-year-old male college student presents during winter break for a scleral lens fitting OS. He was diagnosed with keratoconus, OS>OD, earlier in the year and had epi-off corneal cross-linking (CXL) in his left eye 6 months prior over his summer break. CXL for his right eye had to be postponed because he did not have a suitable contact lens option he could successfully wear (attempts with a corneal GP failed due to discomfort and difficulties with handling).

Manifest refraction and visual acuities were  -4.25 -2.25 x 030, 20/20 OD and -5.50 -3.50 x 135, 20/100 OS. His simulated K’s were 44.5/46.2 D with symmetrical apical astigmatism OD, and 52.1/59.6 D with a central cone OS. Horizontal visible iris diameter was 11.9 mm in each eye.

The diagnostic fitting was performed with the SynergEyes VS (CooperVision), and the initial lens selection of 8.4 base curve (BC), 16.0 mm, plano, 3600 sag, 36-42 scleral landing zone (SLZ) was applied as recommended by the fitting guide. While the lens was settling, over-refraction was performed with a final resultant power of +2.75 sph and BCVA = 20/30. Upon slit-lamp evaluation, the lens was slightly inferiorly decentered, and central clearance obtained by OCT was 346 µm after 20 minutes of wear with thicker midperipheral and limbal clearance than needed. The toric markings indicating the flat meridians of the haptic were located at 12 o’clock and 6 o’clock, with mild superior edge lift and mild mid-haptic blanching in the opposite/steep meridian of the haptic at 3 o’clock and 9 o’clock, indicating slightly flat LZ circumferentially. 

To optimize the fit, the BC ordered was steepened from 8.4 mm to 8.2 mm to reduce the midperipheral and limbal clearance, and to match the peripheral profile of the cornea more closely (Figure 1). This BC change requires additional minus power. The lens ordered was modified and had the benefit of decreasing the amount of hyperopic power by
1 D, which also reduces central thickness. The sagittal depth was decreased 100 µm to a 3500 sag to lessen the central clearance. To align the landing zones more evenly in both major meridians, the SLZ of 38-44 was chosen to steepen the haptics by 60 µm circumferentially and the diameter increased to 16.5 to better distribute the weight
by expanding the foot. Note that each of these changes are all independent and do not affect the others. Menicon Z material was chosen to maximize the Dk/t of the lens, especially since plus scleral lenses will always be thicker centrally than their minus lens counterparts.

Discussion

The first lens ordered was a great fit while giving the patient the best vision he’s had in a long time (20/25). In the meantime, we replaced his habitual glasses with a plano lens OS so he could continue to wear them over the scleral lens to maintain binocularity while awaiting crosslinking for his OD next summer.

For the new or seasoned scleral lens prescriber, predictability is dependent on stability of the diagnostic lens. The tangential landing zones and independent parameters of this design allowed for a quicker outcome.

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Dr. Andrzejewski is an optometrist at Chicago Cornea Consultants and an adjunct clinical professor at the Illinois College of Optometry and the Chicago College of Optometry. She is a Fellow of the American Academy of Optometry. She discloses renumeration from Bausch + Lomb Specialty Vision Products, Contamac, CooperVision Specialty Eyecare, Essilor Contact Lenses, and the GPLI.