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Short-term wear of small-diameter scleral lenses does not affect IOP
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Large-diameter scleral lenses settle into conjunctival tissue and may also compress deeper structures that produce resistance to aqueous humor outflow.
However, researchers determined that 15-mm scleral lens wear for 2 hours does not increase intraocular pressure in healthy eyes, according to a study in Eye & Contact Lens.
A total of 29 healthy participants from 22 years to 44 years old were included. Central IOP measured between 10 mm Hg and 21 mm Hg in each eye, and IOP was within 3 mm Hg between eyes.
No one had a history of eye disease, scleral lens wear or eye surgery.
Each participant was fitted with a 15-mm Jupiter scleral lens on one eye. IOP was measured in both eyes by pneumatonometry centrally on the cornea and peripherally on the sclera.
The lens was placed on the eye and worn for 2 hours.
Researchers remeasured IOP immediately after placement, at 1 hour and 2 hours of lens wear and immediately after lens removal.
At baseline, before lens application, mean central IOP was not different in the study eye compared with the control eye.
Mean peripheral IOP did also not vary significantly from the study eye and the control, but it was higher in both the study eye and the control compared with central IOP in each eye, according to researchers.
After 5 minutes of wear, researchers reported no difference between mean peripheral IOP in the study eye and the control. After 1 hour of lens wear, there was no difference between mean peripheral IOP in the study eye and control. At 2 hours of lens wear, mean IOP remained no different between the study eye and control.
Immediately after removing the scleral lens, mean central IOP in the study eye was not different from mean central IOP in the control or mean baseline central IOP in the study eye, according to researchers.
The researchers said these results should not be considered in patients with glaucoma as they, “may be more susceptible to lens wear because even slight obstruction to conventional outflow may have more effect on IOP,” they wrote.
Also, all patients were relatively young. In older patients, “decreased conjunctival thickness may place them at greater risk for focal compression of the episcleral vasculature, collector channels or the Schlemm’s canal,” they added.
Finally, scleral lens designs vary, and these results may not apply to all scleral lens designs, the researchers concluded. – by Abigail Sutton
Disclosure: Nau reported no relevant financial disclosures. For a list of all remaining authors’ financial disclosures please see the full study.
Perspective
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Blair Lonsberry, OD, FAAO
The treatment of ocular surface conditions and corneal irregularity with scleral contact lenses has dramatically increased over the past several years. These lenses are designed to vault the cornea and have a landing zone on the conjunctiva.
The additional pressure from the lids during a blink could result in compression of the episcleral vessels and a resulting increase in IOP. Large diameter lenses (>18 mm) have wide landing zones and are unlikely to result in increased IOP, but smaller diameter lenses (14 mm to 16.5 mm) have a more limited landing zone near the limbus and could cause elevated IOP.
The authors determined that a smaller diameter (15 mm) scleral contact lens did not significantly influence IOP in neophyte healthy subjects over a 2-hour time period after lens application. This provides valuable information for short-term wear of lenses in the healthy population, but we know that glaucoma patients may respond differently, and the potential changes in IOP with scleral lens wear should be assessed in a glaucoma patient population and for a longer wear time.
Until this issue is clarified, it is advisable to carefully monitor scleral lens wearing glaucoma patients for possible lens-induced pressure elevation.
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Nau CB, et al. Eye & Contact Lens. 2016;doi:1097/ICL.0000000000000214.
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