Scleral lenses continue to grow in popularity year after year, although there are still many unknowns about the long-term outcomes of this modality. One hot topic is whether intraocular pressure (IOP) is affected by scleral lens wear. To date, there are no prospective, randomized, multiyear studies that assess the effect of scleral lenses on patients with glaucoma.
In 2016, McMonnies hypothesized that scleral lenses may increase IOP during lens wear due to compression of the episcleral veins.1 Is it possible that scleral lenses could apply significant pressure on the episcleral veins and aqueous humor drainage to inhibit aqueous outflow, thus elevating IOP?
In 2016, Nau et al evaluated intraocular pressure after two hours of small-diameter scleral lens wear in 29 neophyte healthy subjects.2 A 15mm Jupiter scleral lens was fit on a single study eye and worn for two hours. Intraocular pressure was measured by pneumatonometry (Model 30 Classic: Reichert) in both eyes on the cornea centrally and on the sclera peripherally. In healthy, neophyte eyes, scleral lens wear did not increase IOP after two hours.
Vincent et al described changes in IOP after scleral lens wear using an irregular cornea 16.5mm design Paragon Vision Sciences scleral lens.3 The first study measured IOP of seven subjects before and three hours after scleral lens wear with the Ocular Response Analyzer (Reichert). The follow-up study evaluated IOP in five subjects before and eight hours after scleral lens wear with a non-contact tonometer (TX-20P, Canon). Decreases in IOP were found after scleral lens wear that were consistent with normal diurnal fluctuations in IOP in the control eye. The authors suggested that short-term wear of scleral lenses does not elevate IOP, despite superficial tissue compression near the scleral spur.4
In 2018, a prospective, randomized study published by Michaud et al evaluated IOP using two different scleral lens diameters in 21 subjects with healthy eyes with no known risk for glaucoma.5 Baseline IOPs were established and did not reveal significant diurnal variations. Transpalpebral IOP was taken before and during scleral lens wear. In each subject, one eye was fit with a 15.8mm diameter scleral lens (L1) and the fellow eye was fit with an 18.0mm scleral lens (L2) of the same design, thickness, and material. With L1, IOP rose from 10.1 + 1.9 mmHG to 14.4 + 5.5 mmHG after 4.5 + 0.3 hours, while with L2, it rose from 9.2 + 2.1 mmHG to 14.4 + 4.8 mmHg. This difference is statistically significant based on time but not on lens diameter. Additionally, anterior segment tomography using Oculus Pentacam was taken prior to and after lens removal. These parameters did not vary except for anterior chamber volume and corneal thickness. This study suggests that IOP may be elevated an average by 5 mmHg with scleral lens wear. Although long-term studies have not been performed, this study implies that caution in advised when fitting scleral lenses in patients at risk for or confirmed with glaucoma. When fitting scleral lenses in patients with glaucoma, ocular hypertension or status post a filtration device, caution may be advised. It is important to establish baselines parameters of IOP, visual fields, optical coherence tomography (OCT) and pachymetry prior to fitting scleral lenses and habitually with scleral lens wear. At each scleral lens visit, consider monitoring IOP in patients diagnosed and at risk for glaucoma. If scleral lens wear is of substantial concern or is contraindicated, other contact lens options may be considered.
These studies lead to additional questions. Should different scleral lens designs be manufactured that rest differently on the scleral conjunctiva to prevent IOP elevation? Should scleral lenses not be fit in patients with glaucoma? Are other parameters such as ocular blood flow or corneal hysteresis valuable in this population? Of upmost importance is that there are numerous studies that need to be performed.
McMonnies CW. A hypothesis that scleral contact lenses could elevate intraocular pressure. Clin Exp Optom. 2016;99(6):594-596.
Nau CB, Schornack MM, McLaren JW, Sit AJ. Intraocular Pressure After 2 Hours of Small-Diameter Scleral Lens Wear. Eye Contact Lens. 2016 Nov;42(6):350-353.
Vincent SJ, Alonso-Caneiro D, Collins MJ. Evidence on scleral contact lenses and intraocular pressure. Clin Exp Optom. 2017;100:87-88.
Alonso-Caneiro D, Vincent SJ, Collins MJ. Morphological changes in the conjunctiva, episclera and sclera following short-term miniscleral contact lens wear in rigid lens neophytes. Cont Lens Anterior Eye. 2016 Feb;39(1):53-61.
Michaud L, Samaha D, Giasson CJ. Intra-ocular pressure variation associated with the wear of scleral lenses of different diameters. Cont Lens Anterior Eye. 2018 Jul 24. [Epub ahead of print]
Dr. Barnett is a principal optometrist at the University of California Davis Eye Center in Sacramento, specializing in anterior segment disease and specialty contact lenses. She is the past president of the Scleral Lens Education Society. She is an advisor to and/or has received honoraria or travel expenses from AccuLens, Alcon, Alden Optical, Allergan, Bausch + Lomb, Contamac, CooperVision, EveryDay Contacts, Johnson & Johnson Vision, Ocusoft, Paragon Bioteck, RaayonNova, ScienceBased Health, Shire, SynergEyes, and Visioneering Technologies.