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. Author manuscript; available in PMC: 2021 Sep 1.
Published in final edited form as: Optom Vis Sci. 2020 Sep;97(9):661–668. doi: 10.1097/OPX.0000000000001567

Intraocular Pressure and Optic Nerve Head Morphology during Scleral Lens Wear

Maria K Walker 1, Laura P Pardon 1, Rachel Redfern 1, Nimesh Patel 1
PMCID: PMC7687658  NIHMSID: NIHMS1617645  PMID: 32932395

Abstract

Significance.

Scleral lenses (SL) are increasing in scope and understanding their ocular health impact is imperative. The unique fit of a 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.

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 six hours while the fellow eye served as a control. Global minimum rim width (optical coherence tomography) and IOP (Icare, Diaton) were measured at baseline, two and six hours after SL application, and again post-SL removal. Central corneal thickness, anterior chamber depth, and fluid reservoir depth were monitored.

Results.

Minimum rim width thinning was observed in test (−8 μm; 95% CI: −11 to −6 μm) and control (−6 μm; 95% CI: −9 to −3 μm) eyes after six hours of scleral lens 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 mm Hg (95% CI: +1 to +3 mm Hg) in the test eyes (P = .002), with no change in control eyes. Mean IOP change with Diaton was +0.3 mm Hg (95% CI: −0.9 to +3.2 mm Hg) in test eyes, and +0.4 mm Hg (95% CI: −0.8 to +1.7 mm Hg) in 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.

Scleral lens use has become increasingly widespread to correct vision and provide ocular surface protection for diseased eyes, with the benefits well-established by the visual quality and comfort they provide.1–5 While examples of visual success are acclaimed with scleral lens wear, and the capacity to rehabilitate the ocular surface is proven,6–9 alongside these successes are accounts of adverse events and an increasing concern for potential side effects.10–16 Accordingly, there is an increasing interest in the effects of these custom devices on the ocular surface and adnexa.17,18 With evidence of adverse effects, and considering the diseased eyes for which they are indicated,2,19–25 it is imperative to understand both the positive and negative ocular health impact of scleral lenses.

The scleral lens fit is unique, vaulting over the cornea and landing on the conjunctival tissue adjacent to the limbus. The position of the lens on the eye is driven by a sub-atmospheric pressure beneath the lens,26,27 which forces the scleral lens against the conjunctiva and causes compression as great as about 50 μm.28 Beneath the conjunctiva lie the episcleral veins, and beneath that the trabecular meshwork, canals, ducts and channels of the aqueous humor outflow pathway. A disruption of aqueous dynamics could have an effect on intraocular pressure, a major risk factor for glaucoma. The landing of scleral lenses over these important structures has given rise to concern that the scleral lens can create resistance to aqueous humor outflow and lead to increased intraocular pressure.27,29 Furthermore, greater amounts of scleral lens settling would in theory lead to greater suction force that could exacerbate an increase in intraocular pressure.27

Measuring intraocular pressure during scleral lens wear presents a challenge since most clinical methods of measurement make direct contact with the cornea, which is covered by the scleral lens. To manage this challenge, investigators have measured intraocular pressure using several different techniques: (1) by measuring the pressure over the cornea immediately after lens removal,30–33 (2) by using a corneal-calibrated device against the conjunctival tissue,30 and (3) by using a transpalpebral tonometer that measures intraocular pressure through the eyelids.34 The first modern study, conducted by Nau et al., used both the first and second technique with a pneumotonometer, calibrated for customary use against the cornea.30 Intraocular pressure was measured over the cornea before and after two hours of scleral lens wear, and no difference was found before, during or after scleral lens wear with either technique. A small pilot study by Vincent et al. found no significant increase in intraocular pressure after 3 or 8 hours of lens wear using the Ocular Response Analyzer (Reichert, Buffalo, New York) and a non-contact tonometer (TX-20P, Canon, Amstelveen, The Netherlands), respectively.32 Another more recent study by Aitsebaomo et al. used Icare (Icare Finland Oy, Vantaa, Finland) immediately after lens removal,31 and a study by Michaud et al. used a transpalpebral tonometer (Diaton, DevelopAll Inc.) just prior to lens removal.34 Shahnazi et al. measured intraocular pressure after lens removal in patients with ocular surface disease, using a tonopen.33 Each of these studies has variation in type of scleral lenses worn, sample size, hours of lens wear, and technique used to measure intraocular pressure, which creates a challenge when comparing results from one study to the next.

The optic nerve head is a relatively weak point in the otherwise rigid corneoscleral shell and, as a result, is particularly susceptible to the effects of intraocular pressure.35 Accordingly, in response to acute intraocular pressure elevation with ophthalmodynamometry, changes in optic nerve head structure (e.g., prelaminar tissue, neuroretinal rim thickness) can be detected.36–39 Minimum rim width, quantified using optical coherence tomography, is a robust measure of the neuroretinal rim that has demonstrated excellent repeatability40–43 and is sensitive for detecting subtle changes in optic nerve head structure caused by intraocular pressure increase. Changes in intraocular pressure can result in thinning of the minimum rim width in as little as 5 minutes after intraocular pressure increase in primate models, although it takes approximately 2 hours to see the maximum change.44 Although not typically measured during minimal (<10 mm Hg) changes in intraocular pressure, the dose dependent nature of minimum rim width thinning is suggestive that even with small increases in intraocular pressure (e.g., 5 mm Hg) there would be changes to the minimum rim width after a prolonged increase. In this study, changes in the minimum rim width are measured to indirectly assess fluctuations in intraocular pressure during scleral lens wear.

The goals of the present study were to (1) assess changes in minimum rim width over six hours of scleral lens wear in order to indirectly determine whether scleral lens wear influences intraocular pressure and (2) compare two techniques (Diaton and Icare) for measuring intraocular pressure during scleral lens wear, and determine their relationship to the minimum rim width findings.

METHODS

This study was done in compliance with the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board at the University of Houston College of Optometry. A total of 27 healthy scleral lens neophytes were recruited (26 completed), and all subjects signed an informed consent prior to enrollment. Sample size was determined for ANOVA, using a moderate effect size of f (0.3) with α = 0.05 and power of 0.8. Potential subjects were excluded if they had a personal history of ocular hypertension or glaucoma, if their intraocular pressure measured greater than 20 mm Hg in either eye on the day of enrollment, or if they had a history of ocular surgery (including refractive surgery such as LASIK) that could affect intraocular pressure readings.

The first study visit determined eligibility and selected the lens to be used on the experimental day. Intraocular pressure was measured using Icare (Finland Oy, Vantaa, Finland) rebound tonometry. A scleral lens fitting set (Zenlens RC for regular corneas, Alden Optical, Rochester, NY) was used to fit one randomly selected eye with a 15.4 mm diagnostic scleral lens. Lenses were selected to vault the cornea by approximately 250 μm and provide clearance over the limbus, landing without obvious compression of the conjunctival blood vessels. All transition zone radii and landing zone radii had spherical curvatures for this study.

On the day of the experiment, subjects arrived at 7:30 am. Biomicroscopy and visual acuity were evaluated to confirm normal ocular health. After initial baseline testing, a scleral lens was applied to the test eye at approximately 8:30 am and worn for a total of six hours. Measurements were taken at baseline (before and after scleral lens application), after two and six hours of scleral lens wear, and again immediately after lens removal. The two principal data collected were intraocular pressure and optical coherence tomography derived minimum rim width (primary outcome); additionally, anterior chamber depth and corneal thickness were measured (Lenstar LS900, Haag-Streit, Koeniz, Switzerland), as well as scleral lens fluid reservoir depth (Spectralis OCT2, Heidelberg Engineering, Heidelberg, Germany).

Intraocular Pressure Measurement

During the experimental visit, intraocular pressure was measured with the Icare rebound tonometer and the Diaton transpalpebral tonometer. The Icare, which requires contact with the cornea, was used only before and after scleral lens wear on the test eyes (control eyes were measured at each timepoint) and was measured within five seconds of scleral lens removal when applicable. Measurements were repeated three times at each session and averaged for the final values. The Diaton was used on both eyes at all timepoints, while subjects laid in a supine position and were instructed to look at a target approximately 45 degrees down toward their feet. The instrument probe was placed posterior to the eyelash margin just above where the scleral lens edge would land. Each instrument output represented a series of measurements analyzed and averaged by the instrument, and two measurements were obtained and averaged for each timepoint. The agreement of the two instruments was compared using a total of 100 matched measurements taken on the same eyes.

Minimum Rim Width Measurement

Optical coherence tomography (Spectralis OCT2, Heidelberg Engineering, Heidelberg, Germany) was used to measure the change in minimum rim width over six hours of scleral lens wear. Global minimum rim width was measured in both eyes at baseline (pre- and post-lens application for test eyes), at the two-hour and six-hour time points, and again in the test eye after scleral lens removal. The Spectralis OCT system used for this study has a theoretical resolution of 7 μm. However, this axial resolution is for a single A-scan, and thickness measures are an average of several A-scans. Hence, with rigorous manual segmentation, it is possible to detect changes smaller than the theoretical axial resolution. Minimum rim width has demonstrated excellent repeatability with a within-subject standard deviation between approximately 1–2 μm.45,46

To quantify minimum rim width, defined as the minimum distance from Bruch’s membrane opening to the internal limiting membrane, a 24-line (15-degree) radial scan centered on the optic nerve head was acquired, and Bruch’s membrane opening and the inner limiting membrane were automatically identified (Glaucoma Module Premium Edition, version 6.0, Heidelberg Engineering, Heidelberg, Germany) (Figure 1). The software will occasionally fail to correctly locate Bruch’s membrane opening, which can then be manually re-selected for the software to calculate rim width. Each scan was carefully inspected during this manual segmentation process and adjusted as needed by a single investigator (MW), then verified by a second investigator (NP). Manual correction of automated segmentation is an essential step in analysis to ensure accurate Bruch’s membrane opening detection; however, pre- and post- segmentation correction values for global minimum rim width still have excellent agreement as shown in other studies.43,46 In order to minimize magnification effects with scleral lens wear, all scans subsequent to the initial pre-lens baseline were obtained using the AutoRescan feature.

Figure 1.

Figure 1.

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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,43 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.

Statistical Analysis

Normality of the data was tested using the D’Agostino-Pearson normality test. Mean intraocular pressure and minimum rim width were compared between eyes before, during, and after scleral lens wear, using repeated-measures ANOVA, paired t-test, and the non-parametric equivalents when appropriate. Linear regression and Pearson’s correlation analyses were done to determine if there were associations between change in minimum rim width, change in intraocular pressure, and change in the fluid reservoir depth. To compare these variables of different scales, values were normalized by calculating them as their percent change from baseline.

To assess the performance of the Icare and Diaton, a total of 100 intraocular pressure measurements taken on the same eyes with both instruments were compared using Bland-Altman analysis, linear regression, and Pearson’s correlation coefficient. Additionally, repeatability was calculated for each instrument. All statistical analysis was completed using GraphPad Prism 7 (GraphPad Software, Inc, La Jolla, CA).

RESULTS

A total of 26 adults (81% female) between the ages of 23 and 33 years with normal ocular health and no history of scleral lens wear were included in this study. Mean central fluid reservoir depth was 221 μm (95% CI: 192 – 251 μm) at initial application and 148 μm (95% CI: 121 – 175 μm) after six hours of lens wear, settling an average of 73 μm (95% CI: 56 – 91 μm). Prior to scleral lens application, mean central corneal thickness in test eyes was 540 μm (95% CI: 520 – 559 μm) and in the control eyes was 535 μm (95% CI: 513 – 557 μm), showing no difference between the eyes (P = 0.18). After 6 hours of scleral lens wear, and measured within 5 minutes of lens removal, mean corneal thickness in test eyes was 537 μm (95% CI: 517 – 557 μm), and in control eyes was 523 μm (95% CI: 501 – 544 μm), significantly greater in the test eyes (P = 0.0001) but reduced from baseline in both eyes. Anterior chamber depth remained unchanged in test and control eyes throughout the experimental visit: baseline: 3.133 mm (95% CI: 2.900 – 3.366 mm) in test eyes; 3.039 mm (95% CI: 2.937 – 3.141 mm) in control eyes (P = 0.50). Post-lens removal: 3.062 mm (95% CI: 2.953 – 3.172 mm) in test eyes; 3.010 mm (95% CI: 2.905 – 3.115 mm) in control eyes (P = 0.24).

Intraocular Pressure

Mean intraocular pressure (Icare) on the morning of the experimental visit was 14 mm Hg (95% CI: 12 – 15 mm Hg) in both the test and control eyes. At the two-hour, six-hour, and post-lens timepoints, average intraocular pressure in the control eyes was 13 mm Hg (95% CI at six-hours: 12 – 14 mm Hg), showing no significant change after six hours (P = 0.19). Mean intraocular pressure in the test eyes, only measured again after scleral lens removal, was 16 mm Hg (95% CI: 14 – 18 mm Hg), showing a +2 mm Hg (95% CI: +1 to +3 mm Hg) increase in intraocular pressure from baseline (P = .002) (Figure 2).

Figure 2.

Figure 2.

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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.

Intraocular pressure measured with the Diaton was 14 mm Hg (95% CI: 12 – 16 mm Hg) in both the test and the control eyes prior to scleral lens application. After six hours of scleral lens wear (pre-removal), it was 15 mm Hg (95% CI: 13 – 18 mm Hg) in the test eyes and 14 mm Hg (95% CI: 12 – 16 mm Hg) in the control eyes, not significantly different from each other (P = .35) or from their respective baseline measurements (P = .11 for test eyes; P = .71 for control eyes). After scleral lens removal, the mean test eye measurement returned to 14 mm Hg (95% CI: 12 to 16 mm Hg). The mean intraocular pressure change with Diaton was +0.3 mm Hg (95% CI: −0.9 to +3.2 mm Hg) in the test eyes, and +0.4 mm Hg (95% CI: −0.8 to +1.7 mm Hg) in the control eyes, showing no difference between the two eyes (P = .90).

A comparison of means between the Icare and Diaton for 100 intraocular pressure measurements showed no significant difference (Diaton: 15 mm Hg (95% CI: 13 – 15 mm Hg); Icare: 14 mm Hg (95% CI: 14 – 15 mm Hg); P = .35). The within-subject standard deviation was calculated (square root of the variance), then multiplied by 2.77 to determine repeatability.47 For the Diaton, the repeatability was 8 mm Hg, versus the Icare which had a repeatability of 2 mm Hg. The instruments were also compared using Bland-Altman analysis which showed poor agreement and correlation of the instruments (regression slope = 0.22; R2 = 0.03; Y-Intercept = 10.00; P = .07) (Figure 3).

Figure 3.

Figure 3.

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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.

Minimum Rim Width

The mean minimum rim width at baseline, measured between 8 am and 9 am, was 351 μm (95% CI: 330 – 372 μm) in test eyes and 344 μm (95% CI: 323 – 365 μm) in control eyes. Intrasubject values were highly correlated to each other at baseline (R2 = 0.76; P < .001). After six hours and prior to scleral lens removal, minimum rim width was 343 μm (95% CI: 323 – 363 μm) in test eyes and 338 μm (95% CI: 318 – 358 μm) in control eyes. This was a significant amount of minimum rim width change from baseline in both the test (−8 μm; 95% CI: −11 to −6 μm) and the control eyes (−6 μm; 95% CI: −9 to −3 μm) (P < .01) (Figure 4). The difference in minimum rim width change between eyes, calculated by subtracting the control eye thinning from the test eye thinning for each subject, was on average −2 μm (95% CI: −5 to 0 μm), indicating a slightly greater amount of thinning in the test eyes; however, this difference was not statistically significant (P = .09). After scleral lens removal, minimum rim width was repeated in test eyes and did not change significantly from the pre-scleral lens removal measurements taken at six hours (P = .88) (Figure 4).

Figure 4.

Figure 4.

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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.

There was individual variation observed in this data. While on average there was not a significant difference in the minimum rim width with scleral lens wear, 8 test eyes (31%) and 7 control eyes (27%) had greater than 10 μm of minimum rim width thinning over the six-hour period. Most of the subjects with high amounts of thinning showed relatively symmetrical thinning between the eyes, although there was a trend of approximately 3 to 5 μm greater thinning in test eyes for several subjects (n = 10). Only two eyes, both test eyes, showed greater than 20 μm thinning during the test period, but both fellow control eyes also showed higher than average amounts of thinning.

Linear regression and correlation analyses were done to evaluate associations between changes in minimum rim width, intraocular pressure, and fluid reservoir depth. Change in minimum rim width was not correlated with change in intraocular pressure (regression slope = 0.01; R2 = 0.02; Y-Intercept = −0.02; P = .50) or change in fluid reservoir depth (regression slope = 0.002; R2 = 0.0005; Y-Intercept = −0.02; P = .91). Additionally, there was no correlation between change in intraocular pressure (measured with Icare after lens removal) and change in fluid reservoir depth (regression slope = 0.31; R2 = 0.11; Y-Intercept = 0.3; P = .10).

DISCUSSION

In this study the effect of scleral lens wear on the optic nerve head minimum rim width and intraocular pressure were evaluated. Although there was a trend for increased thinning of the minimum rim width in test eyes, the change for the six hours of scleral lens wear was not statistically significant for these healthy eyes. However, there was a trend of greater thinning in the eyes wearing scleral lenses that suggests certain individuals may be experiencing changes to the optic nerve head structure due to an increase in intraocular pressure. Individuals in this study with the greatest magnitude of minimum rim width thinning of the test or control eye were of greatest interest, as in theory they would be more likely to be sensitive to changes in intraocular pressure. However, in these individuals, the magnitude of minimum rim width thinning was similar between the eyes.

Almost all eyes showed minimum rim width thinning, regardless of scleral lens wear. The normal eye exhibits diurnal changes in minimum rim width throughout the day, on average showing approximately 8 μm of thinning between 7am and 7pm in young, healthy individuals without contact lens wear. However, there is considerable individual variability over a 12-hour period (range −31 to +1 μm).45 Therefore, this study used a control eye from the same individual to help reduce the effect of inter-subject variability. Ultimately, a normal eye appears to be quite capable of wearing a fitted scleral lens and maintaining a balance in intraocular pressure within limits that does not create significant mechanical stress at the optic nerve head.

It is not surprising that we do not see a significant difference in minimum rim width thinning between eyes, because normal individuals are quite capable of managing long-term intraocular pressure stress. The natural homeostasis of intraocular pressure is constantly tested by forces such as fluid intake, medications, body orientation, alcohol consumption, respiration, heart rate, exercise, and diurnal rhythms.48 In response, the trabecular meshwork is capable of sensing a transient increase in outflow resistance, and will respond by increasing pulsatile flow or reducing upstream resistance to avoid prolonged intraocular pressure increases that can create stress at the optic nerve head.49–52 However, glaucomatous eyes are often unable to self-regulate these stresses on intraocular pressure,52–54 therefore it is essential that these experiments be repeated in that population. Furthermore, individuals with collagen diseases such as keratoconus, a population with a high incidence of scleral lens wear, may show a different response than seen with the normal eye.55

Intraocular pressure was measured using two different methods. The Diaton, able to measure intraocular pressure as indicated during scleral lens wear, seemed desirable to use but exhibited questionable reliability. This was in agreement with other studies that showed poor comparability to the gold standard Goldmann applanation tonometry.56–59 The Icare, a validated instrument that is reasonably comparable to Goldmann applanation tonometry,60–62 was in part used here to offer potential validation of the Diaton. Our assessment of the instruments showed a large variability of the Diaton, which had a repeatability of 8 mm Hg. Conversely, the Icare showed a better repeatability of 2 mm Hg. There was also poor correlation between the Icare and the Diaton, suggesting poor accuracy of the Diaton, a conclusion that is in agreement with other studies.56–58 We propose that the inconsistencies of the Diaton are in part due to variation in eyelid morphology between subjects, such as eyelid thickness, elasticity, and other mechanical tissue properties. The Diaton data in this study also did not agree with the study by Michaud et al., which showed an approximately 5 mm Hg increase after several hours of lens wear.34 Ultimately, the Diaton cannot be considered an accurate and reliable instrument for intraocular pressure assessment during scleral lens wear.

After removal of the scleral lenses, the Icare intraocular pressure was significantly greater in test eyes than control eyes. This is in relative agreement with the Aitsebaomo study, which also used Icare, although they saw an average increase about three times greater.31 However, the Icare data here does not agree with several studies that have used different methods of measuring intraocular pressure. Nau et al. found no increase using corneal pneumotonometry after two hours of scleral lens wear,30 Vincent et al. saw a slight reduction after several hours of lens wear when measuring with an ocular response analyzer and a non-contact tonometer,32 and Shahnazi et al. also observed a slight decrease when measuring with tonopen in ocular surface disease patients.33 The discrepancies in the studies may be due to the instruments used, the duration of scleral lens wear (which was 2, 3–8, and 1–8 hours, respectively for the studies mentioned) or differences in the exact protocol for measuring intraocular pressure after scleral lens removal (i.e. how long after removal was intraocular pressure measured?). If an increase in intraocular pressure is true, either due to scleral lens wear or from the process of removing the lens itself, McMonnies et al. would predict that at removal the intraocular pressure would almost instantly return to baseline.27,63 This study measured IOP within 5 seconds of scleral lens removal, so may have still been able to capture an increase during SL wear, although this is ultimately unknown. The remaining questions are whether the increased Icare measurements are true, and if so, are they caused by prolonged intraocular pressure increase during scleral lens wear, or caused by the process of lens removal itself?

This study, while novel in technique, had several limitations that should be considered when designing similar studies. This study was short-term and in normal subjects; long-term studies in diseased eyes may show different results, and this type of study should be repeated in individuals with glaucoma and keratoconus specifically. Another limitation is that normal diurnal changes in minimum rim with were not evaluated in test eyes in the absence of a scleral lens. However, test eyes would be expected to follow a similar diurnal pattern to control eyes for a given individual, especially given the high correlation of minimum rim width between eyes at baseline. Additionally, the duration of intraocular pressure increase measured with Icare after lens removal was not determined, and future studies should measure intraocular pressure for several minutes or longer after lens removal. Future studies may also benefit from careful biomicroscopic assessment of the anterior segment aqueous and episcleral veins beneath the scleral lens landing zone, which can sometimes be observed for pulsatile blood flow patterns.50,51 Lastly, a direct and accurate measure of intraocular pressure was still not obtained during scleral lens wear, although we are not aware of an instrument that can safely accomplish this task.

This is the first study to our knowledge that evaluates the sensitive optic nerve head tissue as an indirect measure of intraocular pressure during scleral lens wear. This study suggests that scleral lenses have a relatively small effect on intraocular pressure in the normal eye, and that any impacts of pressure fluctuation on the optic nerve are likely not significant for young, healthy eyes. This conclusion is supported by the insignificant difference in optic nerve head minimum rim width change in scleral lens wearing eyes. The long-term effects of scleral lenses on intraocular pressure and optic nerve head structure, especially in susceptible eyes, should be investigated.

ACKNOWLEDGMENTS

Supported by NIH Grant P30 EY007551, University of Houston GEAR grant.

The authors would like to acknowledge Bausch & Lomb Specialty Vision Products, whose diagnostic fitting set was used for this study.

Footnotes

REFERENCES

  • 1.Visser ES, Visser R, van Lier HJ, Otten HM. Modern Scleral Lenses Part I: Clinical Features. Eye Contact Lens 2007;33:13–20. [DOI] [PubMed] [Google Scholar]
  • 2.Dimit R, Gire A, Pflugfelder SC, Bergmanson JP. Patient Ocular Conditions and Clinical Outcomes using a PROSE Scleral Device. Contact Lens Anter Eye 2013;36:159–63. [DOI] [PubMed] [Google Scholar]
  • 3.Bergmanson J, Walker MK, Johnson LA. Assessing Scleral Contact Lens Satisfaction in a Keratoconus Population. Optom Vis Sci 2016;93:855–60. [DOI] [PubMed] [Google Scholar]
  • 4.Laballe R, Vigne J, Denion E, et al. Preclinical Assessment of Scleral Lens as a Reservoir-based Ocular Therapeutic System. Contact Lens Anter Eye 2016;39:394–6. [DOI] [PubMed] [Google Scholar]
  • 5.van der Worp E, Bornman D, Ferreira DL, et al. Modern Scleral Contact Lenses: A Review. Contact Lens Anter Eye 2014;37:240–50. [DOI] [PubMed] [Google Scholar]
  • 6.Visser E-S, Van der Linden BJ, Otten HM, et al. Medical Applications and Outcomes of Bitangential Scleral Lenses. Optom Vis Sci 2013;90:1078–85. [DOI] [PubMed] [Google Scholar]
  • 7.Alipour F, Kheirkhah A, Jabarvand Behrouz M. Use of Mini Scleral Contact Lenses in Moderate to Severe Dry Eye. Contact Lens Anter Eye 2012;35:272–6. [DOI] [PubMed] [Google Scholar]
  • 8.Visser E-S, Visser R, van Lier HJ, Otten HM. Modern Scleral Lenses Part II: Patient Satisfaction. Eye Contact Lens 2007;33:21–5. [DOI] [PubMed] [Google Scholar]
  • 9.Heur M, Bach D, Theophanous C, Chiu GB. Prosthetic Replacement of the Ocular Surface Ecosystem Scleral Lens Therapy for Patients with Ocular Symptoms of Chronic Stevens-Johnson syndrome. Am J Ophthalmol 2014;158:49–54. [DOI] [PubMed] [Google Scholar]
  • 10.Walker M, Bergmanson J, Miller W, et al. Complications and Fitting Challenges Associated with Scleral Contact Lenses: A Review. Contact Lens Anter Eye 2016;39:88–96. [DOI] [PubMed] [Google Scholar]
  • 11.Fernandes M, Sharma S. Polymicrobial and Microsporidial Keratitis in a Patient Using Boston Scleral Contact Lens for Sjogren’s Syndrome and Ocular Cicatricial Pemphigoid. Contact Lens Anter Eye 2013;36:95–7. [DOI] [PubMed] [Google Scholar]
  • 12.Rathi VM, Mandathara PS, Vaddavalli PK, et al. Fluid Filled Scleral Contact Lens in Pediatric Patients: Challenges and Outcome. Contact Lens Anter Eye 2012;35:189–92. [DOI] [PubMed] [Google Scholar]
  • 13.Michaud L For a Better Understanding of Scleral Contact Lens-related Pathophysiology. Invest Ophthalmol Vis Sci 2014;55:6430. [DOI] [PubMed] [Google Scholar]
  • 14.Compañ V, Aguilella-Arzo M, Edrington TB, Weissman BA. Modeling Corneal Oxygen with Scleral Gas Permeable Lens Wear. Optom Vis Sci 2016;93:1339–48. [DOI] [PubMed] [Google Scholar]
  • 15.Nixon AD, Barr JT, VanNasdale DA. Corneal Epithelial Bullae after Short-term Wear of Small Diameter Scleral Lenses. Contact Lens Anter Eye 2017;40:116–26. [DOI] [PubMed] [Google Scholar]
  • 16.Isozaki VL, Chiu GB. Transient Corneal Epithelial Bullae Associated with Large Diameter Scleral Lens Wear: A Case Series. Contact Lens Anter Eye 2018;41:463–8. [DOI] [PubMed] [Google Scholar]
  • 17.Povedano-Montero FJ, Alvarez-Peregrina C, Hidalgo Santa Cruz F, et al. Bibliometric Study of Scientific Research on Scleral Lenses. Eye Contact Lens 2018;44(Suppl. 2):S285–S91. [DOI] [PubMed] [Google Scholar]
  • 18.Davies I Scleral Publications & Contact Lens Category Growth. Contact Lens Anter Eye 2019;42:234–5. [DOI] [PubMed] [Google Scholar]
  • 19.Rathi VM, Mandathara PS, Taneja M, et al. Scleral Lens for Keratoconus: Technology Update. Clin Ophthalmol 2015;28:2013–8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Barnett M, Mannis MJ. Contact Lenses in the Management of Keratoconus. Cornea 2011;30:1510–6. [DOI] [PubMed] [Google Scholar]
  • 21.Pullum KW, Whiting MA, Buckley RJ. Scleral Contact Lenses: the Expanding Role. Cornea 2005;24:269–77. [DOI] [PubMed] [Google Scholar]
  • 22.Severinsky B, Behrman S, Frucht-Pery J, Solomon A. Scleral Contact Lenses for Visual Rehabilitation after Penetrating Keratoplasty: Long-term Outcomes. Contact Lens Anter Eye 2014;37:196–202. [DOI] [PubMed] [Google Scholar]
  • 23.Bavinger JC, DeLoss K, Mian SI. Scleral Lens use in Dry Eye Syndrome. Curr Opin Ophthalmol 2015;26:319–24. [DOI] [PubMed] [Google Scholar]
  • 24.Takahide K, Parker PM, Wu M, et al. Use of Fluid-Ventilated, Gas-Permeable Scleral Lens for Management of Severe Keratoconjunctivitis Sicca Secondary to Chronic Graft-versus-Host Disease. Biol Blood Marrow Transplant 2007;13:1016–21. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Schornack MM, Baratz KH, Patel SV, Maguire LJ. Jupiter Scleral Lenses in the Management of Chronic Graft versus Host Disease. Eye Contact Lens 2008;34:302–5. [DOI] [PubMed] [Google Scholar]
  • 26.Miller D, Carroll J, Holmberg A. Scleral Lens Cling Measurement. Am J Ophthalmol 1968;65:929–30. [DOI] [PubMed] [Google Scholar]
  • 27.McMonnies CW. A Hypothesis that Scleral Contact Lenses could Elevate Intraocular Pressure. Clin Exper Optom 2016;99:594–6. [DOI] [PubMed] [Google Scholar]
  • 28.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. Contact Lens Anterior Eye 2016;39:53–61. [DOI] [PubMed] [Google Scholar]
  • 29.Fadel D, Kramer E. Potential Contraindications to Scleral Lens Wear. Contact Lens Anter Eye 2019;42:92–103. [DOI] [PubMed] [Google Scholar]
  • 30.Nau CB, Schornack MM, McLaren JW, Sit AJ. Intraocular Pressure after 2 Hours of Small-Diameter Scleral Lens Wear. Eye Contact Lens 2016;42:350–3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31.Aitsebaomo A, Wong-Powell J, Miller WL, Amir F. Influence of Scleral Lens on Intraocular Pressure. J Contact Lens Res Sci 2019;3:e1–9. [Google Scholar]
  • 32.Vincent SJ, Alonso-Caneiro D, Collins MJ. Evidence on Scleral Contact Lenses and Intraocular Pressure. Clin Exper Optom 2017;100:87–8. [DOI] [PubMed] [Google Scholar]
  • 33.Shahnazi KC, Isozaki VL, Chiu GB. Effect of Scleral Lens Wear on Central Corneal Thickness and Intraocular Pressure in Patients With Ocular Surface Disease. Eye Contact Lens 2019;Oct. 24:e-pub ahead of print:doi 10.1097/ICL.0000000000000670. [DOI] [PubMed] [Google Scholar]
  • 34.Michaud L, Samaha D, Giasson CJ. Intra-ocular Pressure Variation Associated with the Wear of Scleral Lenses of Different Diameters. Contact Lens Anter Eye 2019;42:104–10. [DOI] [PubMed] [Google Scholar]
  • 35.Downs JC. Optic Nerve Head Biomechanics in Aging and Disease. Exp Eye Res 2015;133(4):19–29. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 36.Fazio MA, Johnstone JK, Smith B, et al. Displacement of the Lamina Cribrosa in Response to Acute Intraocular Pressure Elevation in Normal Individuals of African and European Descent. Investig Ophthalmol Vis Sci 2016;57:3331–9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37.Bedggood P, Tanabe F, McKendrick AM, et al. Optic Nerve Tissue Displacement during Mild Intraocular Pressure Elevation: its Relationship to Central Corneal Thickness and Corneal Hysteresis. Ophthalmic Physiol Opt 2018;38:389–99. [DOI] [PubMed] [Google Scholar]
  • 38.Agoumi Y, Sharpe GP, Hutchison DM, et al. Laminar and Prelaminar Tissue Displacement during Intraocular Pressure Elevation in Glaucoma Patients and Healthy Controls. Ophthalmology 2011;118:52–9. [DOI] [PubMed] [Google Scholar]
  • 39.Tun TA, Atalay E, Baskaran M, et al. Association of Functional Loss with the Biomechanical Response of the Optic Nerve Head to Acute Transient Intraocular Pressure Elevations. JAMA Ophthalmol 2018;136:184–92. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40.Gupta L, Rahmatnejad K, Gogte P, et al. Reproducibility of Minimum Rim Width and Retinal Nerve Fibre Layer Thickness using the Anatomic Positioning System in Glaucoma Patients. Can J Ophthalmol 2019;54:335–41. [DOI] [PubMed] [Google Scholar]
  • 41.Enders P, Bremen A, Schaub F, et al. Intraday Repeatability of Bruch’s Membrane Opening-based Neuroretinal Rim Measurements. Invest Ophthalmol Vis Sci 2017;58:5195–200. [DOI] [PubMed] [Google Scholar]
  • 42.Schrems-Hoesl L, Schrems W, Laemmer R, et al. Precision of Optic Nerve Head and Retinal Nerve Fiber Layer Parameter Measurements by Spectral-domain Optical Coherence Tomography. J Glaucoma 2018;27:407–14. [DOI] [PubMed] [Google Scholar]
  • 43.Park K, Kim J, Lee J. Reproducibility of Bruch Membrane Opening-Minimum Rim Width Measurements with Spectral Domain Optical Coherence Tomography. J Glaucoma 2017;26:1041–50. [DOI] [PubMed] [Google Scholar]
  • 44.Pardon LP, Harwerth RS, Patel NB. Neuroretinal Rim Response to Transient Changes in Intraocular Pressure in Healthy Non-Human Primate Eyes. Exp Eye Res 2020;193:107978. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 45.Pardon L, McAllister F, Cheng H, Patel N. Minimum Rim Width Decreases over a 12-hour Daytime Period in Healthy Individuals. Optom Vis Sci 2018;95:180035. [Google Scholar]
  • 46.Almobarak FA, O’Leary N, Reis AS, et al. Automated Segmentation of Optic Nerve Head Structures with Optical Coherence Tomography. Invest Ophthalmol Vis Sci 2014;55:1161–8. [DOI] [PubMed] [Google Scholar]
  • 47.Bland JM, Altman DG. Measurement error. Br Med J 1996;313:744. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 48.Abu-Hassan DW, Acott T, Kelley M. The Trabecular Meshwork: A Basic Review of Form and Function. J Ocul Biol 2014;2:1–22. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 49.Chowdhury UR, Hann CR, Stamer WD, Fautsch MP. Aqueous Humor Outflow: Dynamics and Disease. Invest Ophthalmol Vis Sci 2015;56:2993–3003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 50.Johnstone M, Martin E, Jamil A. Pulsatile Flow into the Aqueous Veins: Manifestations in Normal and Glaucomatous Eyes. Exp Eye Res 2011;92:318–27. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 51.Xin C, Wang RK, Song S, et al. Aqueous Outflow Regulation: Optical Coherence Tomography Implicates Pressure-Dependent Tissue Motion. Exp Eye Res 2017;158:171–86. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 52.Carreon T, van der Merwe E, Fellman RL, et al. Aqueous Outflow - a Continuum from Trabecular Meshwork to Episcleral Veins. Prog Retin Eye Res 2017;57:108–33. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 53.Acott TS, Kelley MJ, Keller KE, et al. Intraocular Pressure Homeostasis: Maintaining Balance in a High-pressure environment. J Ocul Pharmacol Ther 2014;30:94–101. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 54.Johnstone M, Jamil A, Martin E. Aqueous veins and open angle glaucoma In: Schacknow PN, Samples JR, eds. The Glaucoma Book: A Practical, Evidence-Based Approach to Patient Care. New York: Springer;2010:65–78. [Google Scholar]
  • 55.Loukovitis E, Sfakianakis K, Syrmakesi P, et al. Genetic Aspects of Keratoconus: A Literature Review Exploring Potential Genetic Contributions and Possible Genetic Relationships with Comorbidities. Ophthalmol Ther 2018;7:263–92. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 56.Li Y, Shi J, Duan X, Fan F. Transpalpebral Measurement of Intraocular Pressure using the Diaton Tonometer versus Standard Goldmann Applanation Tonometry. Graefe’s Arch Clin Exp Ophthalmol 2010;248:1765–70. [DOI] [PubMed] [Google Scholar]
  • 57.Doherty MD, Carrim ZI, O’Neill DP. Diaton Tonometry: An Assessment of Validity and Preference against Goldmann Tonometry. Clin Exp Ophthalmol 2012;40:e171–5. [DOI] [PubMed] [Google Scholar]
  • 58.Wisse RP, Peeters N, Imhof SM, van der Lelij A. Comparison of Diaton Transpalpebral Tonometer with Applanation Tonometry in Keratoconus. Int J Ophthalmol 2016;9:395–8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 59.Toker MI, Vural A, Erdogan H, et al. Central Corneal Thickness and Diaton Transpalpebral Tonometry. Graefe’s Arch Clin Exp Ophthalmol 2008;246:881–9. [DOI] [PubMed] [Google Scholar]
  • 60.Suman S, Agrawal A, Pal VK, Pratap VB. Rebound Tonometer: Ideal Tonometer for Measurement of Accurate Intraocular Pressure. J Glaucoma 2014;23:633–7. [DOI] [PubMed] [Google Scholar]
  • 61.Li BZ, Hong J, Peng RM, et al. Comparison of ICare Rebound Tonometer and Goldmann Applanation Tonometer after Descemet’s Stripping with Automated Endothelium Keratoplasty. Chinese J Ophthalmol 2013;49:257–62. [PubMed] [Google Scholar]
  • 62.Pronin S, Brown L, Megaw R, Tatham AJ. Measurement of Intraocular Pressure by Patients with Glaucoma. JAMA Ophthalmol 2017;135:1030–6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 63.McMonnies CW, Boneham GC. Experimentally Increased Intraocular Pressure using Digital Forces. Eye Contact Lens 2007;33:124–9. [DOI] [PubMed] [Google Scholar]

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