Comparison of Pneumatonometry and Transpalpebral Tonometry Measurements of Intraocular Pressure during Scleral Lens Wear

Abstract

SIGNIFICANCE As scleral lens wear becomes more common, understanding the impact of these lenses upon ocular physiology is critically important. Studies on the effect of scleral lens wear upon intraocular pressure (IOP) have used different instruments and have reported conflicting results. PURPOSE The purpose of this study was to compare assessment of IOP during scleral lens wear using pneumatonometry and transpalpebral tonometry. METHODS Twenty healthy subjects wore a small-diameter (15.2 mm) and a large-diameter (18.0 mm) scleral lens on the right eye, each for 1 hour in randomized order. IOP was assessed with pneumatonometry and transpalpebral tonometry on both eyes before lens application, immediately after lens application, after 1 hour of lens wear, and immediately after lens removal. Paired t test compared mean IOP in the study eye to the control eye. Repeated-measures ANOVA was performed to take instrumentation, lens diameter, and their interaction into account in an analysis of the change in IOP in the study eye. RESULTS Mean peripheral IOP measured with pneumatonometry was not significantly different from baseline at any subsequent measurement. Measurements with transpalpebral tonometry, however, were significantly different during scleral lens wear immediately after application and after 1 hour of wear with both diameter lenses ( P < .005), but were not significantly different after either sized lens was removed. Repeated-measures ANOVA revealed that the instrument used to measure IOP was a significant factor in IOP changes found during lens wear ( P ≤ .001). CONCLUSIONS Assessment of IOP during scleral lens wear varies based upon the instrument that is used. Although further studies are clearly needed to further elucidate this issue, clinicians should continue to monitor optic nerve structure and function in scleral lens wearers, as they do in all patients.

BCLA CLEAR - Scleral lenses

“…The first methodological challenge is the instrument to be used, as IOP cannot be measured with the accepted gold standard technique (Goldmann applanation tonometry) with the lens in-situ. Measurements obtained following lens removal show minimal change in IOP after short term lens wear [274][275][276][277][278], although one study reported an average increase of 5.8 mmHg after 8 h of wear [279]. Only two studies have examined post-lens removal IOP following longer periods of lens wear (up to 6 months) and reported no significant variation [280].…”

Corneal Biomechanics and Intraocular Pressure Following Scleral Lens Wear in Penetrating Keratoplasty and Keratoconus

“…12 The stable IOP observed after lens wear (median change<0.1 mm Hg increase) is also consistent with recent studies of IOP measured after nonfenestrated scleral lens (15–18 mm diameters) removal using nontrans palpebral tonometers (mean changes ranging from a 1.3 mm Hg decrease to a 1.0 mm Hg increase). 29–35…”

Scleral Tonometry Precision During Scleral Lens Wear: A Pilot Study

“…A majority of studies take two to three consecutive IOP measurements for each eye at each specific time point and average the results, but of note, such studies typically make no comment regarding the confidence interval or standard deviation readout from the instrument itself (the instrument’s assessment of the data reliability). 1 , 2 , 4 , 6 , 12 We believe reporting on this data set is essential as this is how a clinician in a typical office setting would determine whether a measurement taken individually was “reliable” by manufacturer’s standards. Each individual pressure measurement deemed “reliable” and analyzed in each cohort for each eye in the handheld tonometry group had a CI of 90% or greater (mean 94.38%) and in the pneumatonometry group had a standard deviation less than 2 mmHg (mean 0.468).…”

“…In recent years, clinicians have sought to determine whether the application and wear of a prosthetic replacement of the ocular surface ecosystem (PROSE, BostonSight, Needham MA) or scleral lens induces any change in intraocular pressure (IOP). 1–6 Prosthetic replacement of the ocular surface ecosystem (PD) is an integrated treatment that includes designing, manufacturing and fitting a customized medical ocular surface prosthetic device (PD), comprehensive application and removal training, and ongoing collaborative optimization of optometric and ophthalmic care. The PD is manufactured using a gas-permeable plastic material (typically fluorosilicone acrylate) which is customized to each eye using a web-based design software (FitConnect, BostonSight, Needham MA) and mechanical lathe.…”

“…Although prior clinical trials have utilized scleral tonometry to investigate IOP changes in scleral lens wear, to our knowledge, no prior study has focused an investigation on the basic foundational question of the precision (reproducibility) of traditional tonometry instruments when used on the sclera with a PD or scleral lenses applied. 1 …”