IOP and Optic Nerve Head Morphology during Scleral Lens Wear

Abstract

Significance: Scleral lenses (SLs) are increasing in scope, and understanding their ocular health impact is imperative. The unique fit of an SL raises concern that the landing zone causes compression of conjunctival tissue that can lead to resistance of aqueous humor outflow and increased intraocular pressure (IOP).

Purpose: This study aimed to assess changes in optic nerve head morphology as an indirect assessment of IOP and evaluate other IOP assessment methods during SL wear.

Methods: Twenty-six healthy adults wore SL on one randomly selected eye for 6 hours, whereas the fellow eye served as a control. Global minimum rim width (optical coherence tomography) and IOP (Icare, Diaton) were measured at baseline, 2 and 6 hours after SL application, and again after SL removal. Central corneal thickness, anterior chamber depth, and fluid reservoir depth were monitored.

Results: Minimum rim width thinning was observed in the test (-8 μm; 95% confidence interval [CI], -11 to -6 μm) and control (-6 μm; 95% CI, -9 to -3 μm) eyes after 6 hours of SL wear (P < .01), although the magnitude of thinning was not significantly greater in the lens-wearing eyes (P = .09). Mean IOP (Icare) significantly increased +2 mmHg (95% CI, +1 to +3 mmHg) in the test eyes (P = .002), with no change in the control eyes. Mean IOP changes with Diaton were +0.3 mmHg (95% CI, -0.9 to +3.2 mmHg) in the test eyes and +0.4 mmHg (95% CI, -0.8 to +1.7 mmHg) in the control eyes. However, Diaton tonometry showed poor within-subject variation and poor correlation with Icare. No clinically significant changes were observed in central corneal thickness or anterior chamber depth.

Conclusions: This study suggests that SLs have a minimal effect on IOP homeostasis in the normal eye during SL wear and an insignificant impact on the optic nerve head morphology in healthy adult eyes.

Trial registration: ClinicalTrials.gov NCT03926975.

Figures

Figure 1.

Acquisition of radial scans at the optic nerve head to measure minimum rim width. At each imaging session, test and control eyes underwent a 24-line radial scan of the optic nerve head. A fundus image shows the placement of the scan lines (A). Each of the 24 scan lines is an optical coherence tomography section at the nerve (B), shown with the minimum rim width detection arrows in blue. The detection arrows can be manually adjusted as needed, and the program software automatically measures the length of the arrows for each scan. The global (average of all scans) minimum rim width value was used for this study.

Figure 2.

Mean intraocular pressure and changes during six hours of scleral lens wear, measured using Icare and Diaton. The mean intraocular pressure of the test and control eyes are plotted as the mean with 95% CI at each time point for the Icare (A) and Diaton (C), The change in intraocular pressure (Δ IOP) from baseline is shown for the Icare (B) and the Diaton (D) measured after scleral lens removal for test and control eyes. Positive values indicate pressure increased from baseline. A dotted line indicates minimal time passed between measurements. Intraocular pressure measured with Icare was significantly increased in the test eye after six hours of scleral lens wear (P = 0.02). IOP: intraocular pressure.

Figure 3.

Comparison graphs showing the Bland-Altman and correlation plots comparing the Icare and Diaton. A total of 100 measurements, all taken with the Icare and Diaton on eyes that were not wearing scleral lenses, were compared. The Bland-Altman plot (A) indicates a poor agreement between the Diaton and Icare. Each measurement was plotted against each other in the linear regression plot (B), which has a shallow slope that also shows poor agreement between the instruments. The 95% limits of agreement for each plot are shown by the dashed lines.

Figure 4.

Mean minimum rim width changes over six hours of scleral lens wear, measured with optical coherence tomography. Subjects wore a lens on one randomly selected eye for six hours and the fellow eye acted as the control. Mean change in minimum rim width from baseline (Δ MRW) is plotted as the mean with 95% CI at each time point (A) for the test and control eyes (a dotted line for test group plot indicates minimal time passed between measurements). The total change from baseline at six hours (before scleral lens removal) is also shown (B) as a scatterplot of each test and control eye with whiskers showing the 95% CI for each group. Negative values indicate thinning of the minimum rim width. Minimum rim width in the test eyes shows a slightly greater amount of thinning, although not representative of a significant difference (P = .09). MRW: minimum rim width.