A 45-year-old male was referred for a contact lens evaluation. He had been diagnosed with keratoconus 15 years prior and had recently had intracorneal rings OS (6 months prior) and corneal collagen cross-linking in both eyes (4 months prior). He reported distorted vision without correction and needed some form of correction for his profession of driving trucks long distances. 

Upon examination, VA through habitual glasses was 20/20- OD and 20/40- OS, pinhole 20/25 OS. Subjective refraction was -2.50 -1.25 x 021 OD and -2.25 – 3.00 x 160 OS, which improved his vision to 20/20 OD and 20/20 OS. 

During slit lamp exam, the lids of both eyes showed 1+ MGD. The conjunctiva and sclera of both eyes had 1+ diffuse injection. The right cornea had apical thinning and steepening; and the left cornea had apical thinning, steepening, and two corneal segments positioned superiorly and inferiorly OS. 

Corneal tomography was performed. The right cornea had K readings of 42.30/44.50 @109.9 and pachymetry of 473 microns. The left cornea had Ks of 39.7/43.5 @71.6 and pachymetry of 464 microns (Figure 1). The patient was fit with the Metro InSight (Metro Optics) scleral lens OS, a prolate design with toric landing zones, and a higher Dk material to avoid mechanical disruption from a lens touching the cornea over the position of the Intacs.

The initial diagnostic lens parameters were SAG 42.50, power -4.00D, OAD 15.6mm, landing zone +50/-50, and Optimum Infinite material. Over-refraction was -4.50D OD and -5.00D OS, with an ADD powers of +1.50D. The right scleral lens provided adequate limbal clearance and the landing zone showed slight impingement in the nasal horizontal meridian, so the scleral landing zone was flattened by 25 in that meridian, from 50 to 75. An over-refraction of -4.50DS provided vision of 20/20. 

The left scleral lens only had 425 microns of central post-lens fluid reservoir clearance prior to settling. The lens decentered inferiorly and appeared to have slight superior corneal touch. The landing zone was adjusted to improve centration and sagittal depth. An over-refraction of -5.00DS improved vision to 20/25-. 

These changes resulted in the second order parameters OD of SAG 42.50, power -8.25D, OAD 15.6mm, landing zone +50/+75/-50/-50, and OS SAG 42.50, power -8.75D, OAD 15.6mm, landing zone Std/-2.0 resulting in VA 20/20 OU. 

The patient was instructed to fill the lenses with a preservative-free solution prior to application and to disinfect nightly with hydrogen peroxide. Patient reported the lenses were comfortable and being worn 12 hours per day. There was trace staining at the limbus upon lens removal OS at follow-up 2 weeks after the dispense appointment. The overall diameter of the lens was increased to 16.0mm OS to improve the clearance over the transition zone/limbus. 

Discussion

Due to the peripheral corneal elevation above the intracorneal rings, corneal GPs may cause mechanical irritation to the cornea when fitting. Scleral lenses may be more appropriate, as they eliminate the mechanical stress to the cornea as they are designed to completely vault the cornea and limbus and land entirely on the sclera (Barnett et al, 2021).¹     

Jennifer S. Harthan, OD, is a professor of optometry at Illinois College of Optometry and chief of the Cornea Center for Clinical Excellence at the Illinois Eye Institute in Chicago. She practices at Glenview Vision Care in Glenview, Ill. She reports renumeration from Allergan, Art Optical, Bausch + Lomb, Contamac, CooperVision, Euclid, International Keratonus Academy, Johnson & Johnson Vision, Metro Optics, SynergEyes, and Ocular Therapeutix.

REFERENCE

1. Barnett M, Courey C, Fadel D, Lee K, et al. CLEAR- Scleral lenses. Cont Lens Anterior Eye. 2021 Apr; 44(2):270-288.