Contact Lens Spectrum

Newsletter

March 2019

Mastering Scleral Lens Fitting

Melissa Barnett, OD, FAAO, FSLS, FBCLA

The scleral lens modality continues to grow; however, there are few studies that describe specific details of scleral lens fitting.¹ A recent study evaluated the practitioner learning curve when fitting scleral lenses in 85 subjects using a diagnostic lens fitting.² Scleral lenses were fit by a single licensed optometrist who did not have a history of clinical experience fitting scleral lenses. In this study, the initial trial lens was selected based on the manufacturers’ guidelines, severity of the corneal condition and clinical evaluation of the ocular surface. Corneal topography, simulated keratometry measurements and corneal asphericity of the flat and steep corneal meridians were analyzed for each group. Objective measurements such as scleral topography and ocular coherence tomography were not utilized.

Lenses were fit empirically with two diagnostic lens sets from Procornea (Eerbeek, Netherlands). The diagnostic fitting sets consisted of two diameters, 16.4 mm (10 trial lenses) and 20.0 mm (9 trial lenses) with different parameters. Lenses were assessed after a settling time of at least 90 minutes of lens wear for an post-lens tear reservoir of 100 to 200 µm after settling. All subjects were either new to the scleral lens modality or previous scleral lens wearers refit to a different scleral lens design. The study included two major groups, an irregular cornea group and a regular cornea group. The irregular cornea group consisted of comprised corneas with primary or secondary ectasias, post-penetrating keratoplasty, post-refractive surgery and other corneal irregularities. The regular cornea group comprised of those with regular, healthy corneas who failed or rejected other forms contact lenses due to either inadequate vision or lens comfort.

With practitioner experience, both the number of trial lenses required to achieve the best fit and the number of reorders with time was reduced. The number of trial lenses required was statistically significantly lower after fittings 61 to 80 (p<0.05, Wilcoxon) compared to the first 20 fittings. Comparing the irregular and regular cornea groups, there was no difference in the number of trial lenses needed to achieve an ideal fit. In this study, the mean number of lens ordered per eye was 1.76±0.77 on average, similar to a previous study by Adeline Bauer (1.70 lenses per eye).¹

The reorders were performed due to inadequate sagittal height (greater than 30% in both groups), poor vision (23.6%, irregular cornea group), and a combination between poor vision and inadequate fit (33.3%, regular cornea group). Of interest, about 10% of the subjects from both groups reported lens discomfort, even with a satisfactory lens fitting, requiring a reorder. When the lens included a back surface toric design with alterations of the landing zone, comfort improved. Of interest, there was a large increase in the number of toric landing zone lens designs between the first 20 fittings (35%) and fittings numbers 41 to 60 (97%). In the irregular cornea group, 85% of the total lenses fit were toric compared to 74% of lenses in the regular cornea group. Previous studies have illustrated the benefits of toric landing zones including improved comfort, increased wearing time, overall satisfaction, better visual quality, and enhanced optical correction.^3-5 Additional advantages are decreased less lens distortion,⁶ air bubble formation, localized conjunctival vessel blanching,^7,8 lens impingement,^9,10 conjunctival prolapse, debris influx into the lens reservoir⁶ and improved lens centration.⁶

With the assistance of technologies such as scleral topography and anterior segment OCT, the scleral lens fitting process may become increasingly streamlined, thus reducing the number of trial lenses and lens reorders, saving time for scleral lens practitioners and patients alike. Future studies with these technologies will guide us to greater scleral lens success.

Reference(s):

Bauer A, Scleral Lens Data: The first 150 fits. Free Paper presented at Global Specialty Lens Symposium (GSLS), Las Vegas, Nevada, USA, 2018.
Macedo-de-Araújo, RJ, van der Worp, E, González-Méijome JM. Practitioner Learning Curve in Fitting Scleral Lenses in Irregular and Regular Corneas Using a Fitting Trial. Biomed Res Int. 2019 Jan 28;2019:5737124. doi: 10.1155/2019/5737124. eCollection 2019.
Visser ES, Visser R, Van Lier HJ. Advantages of toric scleral lenses. Optom Vis Sci. 2006 Apr;4:233-236.
Visser ES, Visser R, Van Lier HJ, Otten HM. Modern scleral lenses part I: clinical features. Eye Contact Lens. 2007 Jan;33:13-20.
Visser ES, Van der Linden BJ, Otten HM, Van der Lelij A, Visser R. Medical applications and outcomes of bitangential scleral lenses. Optom Vis Sci. 2013 Oct;90:1078-1085.
van der Worp E. A Guide to Scleral Lens Fitting, Version 2.0 [monograph online]. Forest Grove, OR: Pacific University; 2015. Available at http://com- mons.pacificu.edu/mono/10/.
Visser ES, Visser R, Van Lier HJJ, Otten HM. A cross sectional survey of the medical indications for and performance of scleral contact lens wear in The Netherlands. Ophthalmic Res. 2004;36 (suppl 1):180.
Visser ES, Visser R. Case report: bitorische scleralens bij keratitis sicca. Visus 2002;2:92-95.
Schornack MM. Toric haptics in scleral lens design: a case series. Poster presented at the Global Specialty Lens Symposium. Las Vegas, 2013 January. 15. Mahadevan R, Jagadeesh D, Rajan R, Arumugam AO. Unique hard scleral lens post-LASIK ectasia fitting, Optom Vis Sci. 2014 Apr;91(4 Suppl 1):S30- S33.
Mahadevan R, Jagadeesh D, Rajan R, Arumugam AO. Unique hard scleral lens post-LASIK ectasia fitting, Optom Vis Sci. 2014 Apr;91(4 Suppl 1):S30- S33.