SCLERAL CONTACT LENSES can be designed based on ocular surface impressions to generate the most detailed and customized eye-to-lens fitting relationship. The material utilized for the impression is ophthalmic grade polyvinyl siloxane (similar to materials used in dental and audiological device impressions).
Once a quality impression is obtained, it is sent to a laboratory, where a 3D scanning device is used to create an elevation model of the ocular surface with an accuracy of 1 to 2 microns based on more than 5 million data points. The data is directed to a computerized lathe in order to create, in essence, a “fingerprint” of the ocular surface.
The following research suggests the most appropriate applications of this amazing technology, which can be used to accommodate the most challenging ocular surfaces.
Nguyen and co-workers (2018) report on indications and outcomes for patients fit with impression-based therapeutic scleral lenses. Fourteen eyes were reviewed retrospectively. Indications for fitting included limbal stem cell deficiency, post-photorefractive keratectomy (PRK) decentered ablation, pellucid marginal degeneration, Stevens-Johnson syndrome, keratoconus, dry eye, neurotrophic keratitis, exposure keratitis, and post-radial keratotomy (RK) symptoms.
Nine patients reported resolution of their blurry vision, and all reported improvement of dry eye, eye redness, and pain. Six of 7 previous lens wearers reported significantly greater comfort with the impression-based lenses and the ability to wear them throughout the day.
In a separate survey of 95 eyes of 69 patients who were fitted with impression-based scleral lenses (Silverman et al, 2021), indications included irregular corneal shape, ocular surface disease, and extra corneal topographic abnormalities. The authors concluded that this lens is a viable therapy for patients for whom traditional sclerals did not work.
Another study reported on outcomes for 70 eyes of 44 patients (Nau et al, 2021). Primary indications for impression-based sclerals included corneal irregularity and ocular surface disease. Visual acuity improved significantly with these lenses compared to traditional correction modalities. Completion of the fitting process (including a visit to take the impression and do post-fitting assessments) required an average of four visits. The researchers concluded that patients who have complex eye disease and are unable to successfully wear standard scleral lenses may achieve visual and therapeutic success with impression-based devices.
Optimized fitting and stability achieved with impression-based sclerals allows for more successful application of higher-order aberration-correcting optics to the front surface of these lenses. A case report described the use of wavefront-guided (WFG) optics on custom ocular impression-based scleral lenses for visual improvement in a patient with keratoconus (Gelles et al, 2022). When compared with the impression-based lens, the WFG-enhanced lenses reduced the total higher-order root mean square 67% and 64% in the right and left eyes, respectively, resulting in a two-line improvement in best contact lens visual acuity for both eyes in this individual patient.
Impression-based scleral lenses provide the most accurate and customized lens-to-ocular-surface fitting relationship. They address comfort, vision, and physiological response challenges. Hopefully, further development of this technology will benefit more patients.
REFERENCES
1. Nguyen MTB, Thakrar V, Chan CC. EyePrintPRO therapeutic scleral contact lens: indications and outcomes. Can J Ophthalmol. 2018 Feb;53:66-70.
2. Silverman JIM, Huffman JM, Zimmerman MB, Ling JJ, Greiner MA. Indications for Wear, Visual Outcomes, and Complications of Custom Imprint 3D Scanned Scleral Contact Lens Use. Cornea. 2021 May 1;40:596-602.
3. Nau A, Shorter ES, Harthan JS, Fogt JS, Nau CB, Schornack M. Multicenter review of impression-based scleral devices. Cont Lens Anterior Eye. 2021 Oct;44:101380.
4. Gelles JD, Cheung B, Akilov S, Krisa S, Trieu G, Greenstein SA, Chung D, Hersh PS. Ocular Impression-Based Scleral Lens With Wavefront-Guided Optics for Visual Improvement in Keratoconus. Eye Contact Lens. 2022 Nov 1;48:485-488.
