Abstract
Objective: To assess whether Tono-Pen and pneumatonometer measurements obtained from the sclera correlate to intraocular pressure measurements obtained from the cornea. Methods: This is a prospective, cross-sectional study, conducted at the New York Eye and Ear Infirmary of Mount Sinai. Patients were randomized to have their left or right eye included in the study. Exclusion criteria included prior intraocular surgery (except uncomplicated cataract extraction), uveitis, corneal or scleral thinning, central corneal thickness 575 μm, and hyperopia greater than +2 diopters or myopia greater than -4 diopters. Goldmann applanation tonometry, Tono-Pen and pneumatonometer measurements were obtained from the cornea. Tono-Pen and pneumatonometer measurements were obtained from the sclera in the superonasal, superotemporal, inferonasal, and inferotemporal quadrants. Product moment correlation and linear regression were used to examine correlations between the measurements. Results: 50 eyes of 50 patients were enrolled. The scleral intraocular pressure measurements (S-IOP) differed significantly from the corneal intraocular pressure (C-IOP) readings. Moderate correlation was found between the pneumatonometer readings from the superotemporal (r=0.64, P 30 mmHg and an inferotemporal pneumatonometer S-IOP of >39 mmHg was 92.3% (95% Confidence Interval [CI] 63.9%, 98.7%) sensitive and 94.6% (CI 81.8%, 99.2%) specific for a C-IOP ≥ 20 mmHg with positive likelihood ratio of 17.1 (CI 4.4-66.3). Conclusion: S-IOP measurements, especially from the superotemporal and inferotemporal quadrants, can provide useful information about intraocular pressure in eyes in which accurate C-IOP measurements cannot be obtained.
Highlights
Despite the numerous modalities of applanation currently available, intraocular pressure (IOP) estimation remains a challenge when corneal thickness and surface irregularities are present [1]
Goldmann applanation tonometry (GAT) remains the gold standard for IOP assessment; its accuracy is greatly affected by corneal irregularities [1]
Our study aims to evaluate whether there is a relationship between pneumatonometer and Tono-Pen measurements of IOP obtained from each of the four scleral quadrants, as compared to pneumatonometer, Tono-Pen, and GAT measurements obtained from the cornea
Summary
Despite the numerous modalities of applanation currently available, intraocular pressure (IOP) estimation remains a challenge when corneal thickness and surface irregularities are present [1]. Goldmann applanation tonometry (GAT) remains the gold standard for IOP assessment; its accuracy is greatly affected by corneal irregularities [1]. Tono-Pen and pneumatonometer, which have a smaller contact area, may be more useful in such patients; even these tools have limited use when extensive corneal pathology is present. Patients with significant corneal pathology often have concomitant glaucoma [2]. Glaucoma is prevalent after keratoprosthesis surgery [3]; the keratoprosthesis implant precludes assessment of IOP by corneal measurement. Digital palpation is often used to estimate IOP in these patients [4], which has questionable reliability [5]
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