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. 2025 Apr 30;25(1):263.
doi: 10.1186/s12886-025-04060-5.

Intraocular pressure correlation to progressive retinal nerve fiber layer loss in primary open angle glaucoma as measured by standard and modified goldmann applanation tonometers

Sean McCafferty  1 , Manjool Shah  2 , Anupam Laul  3 , Khin Kilgore  4
Affiliations

Intraocular pressure correlation to progressive retinal nerve fiber layer loss in primary open angle glaucoma as measured by standard and modified goldmann applanation tonometers

Sean McCafferty et al. BMC Ophthalmol. .

Abstract

Purpose: Characterize the relationship between intraocular pressure (IOP) as measured by standard and modified Goldmann prisms and the progressive loss of retinal nerve fiber layer (RNFL) in a cohort of glaucoma patients.

Design: Retrospective cross-sectional cohort data analysis.

Participants: The study included all patients from a database of 1927 eyes, 966 patients with same visit sequential standard and modified Goldmann IOP measurements. From the database, 148 eyes, 75 patients met the inclusion criteria of a diagnosis of primary open angle glaucoma (POAG) with at least 5 sequential quality optical coherence tomographer (OCT) measurements.

Methods: Sequential OCT images were obtained with the spectral domain Zeiss OCT5000. Participants were all diagnosed with POAG by untreated IOP ≥ 22, disk changes, and visual field (HVF) loss consistent with glaucomatous optic neuropathy (GON). Included were 575 Goldmann IOP measurements with standard and modified prisms affixed to the Goldmann applanation tonometer (GAT) armature. A modified prism includes a corneal conforming applanation surface minimizing the cornea's contribution to the IOP measurement. The study included a total of 940 OCT visits with an average of 6.3 visits per eye over an average of 4.9 years. Retinal nerve fiber layer (RNFL) loss rate was calculated by serial linear fit of average RNFL thickness measurements. Demographics as well as central corneal thickness (CCT) and corneal hysteresis (CH) data were also collected.

Outcome measures: Pearson correlation coefficients and random coefficient models were used to evaluate the relationship between mean standard and modified IOP measurements and RNFL thickness measurements over time in POAG subjects. Secondary outcomes of CCT and CH correlation to RNFL were similarly analyzed.

Results: For all 148 POAG eyes, the overall rate of RNFL loss for an average standard GAT IOP of 17.9 mmHg was 1.08 µm per year (p = 0.002). Each 1-mmHg increase in standard GAT IOP was associated with an additional RNFL loss of 0.047 µm per year (r = 0.153, p = 0.06). Each 1-mmHg increase in modified GAT IOP was associated with an additional RNFL loss of 0.084 µm per year (r = 0.289, p = 0.0005). A modified prism IOP measurement ≥ 22 mmHg indicates a 2.57 times greater probability of significant RNFL loss than a standard prism IOP measurement ≥ 22 mmHg, p < 0.0001.

Conclusions: Higher levels of GAT IOP during follow-up were related to higher rates of progressive RNFL loss detected by optic nerve OCT in treated POAG. A modified GAT prism surface demonstrates a significantly increased sensitivity, reliability and differentiation to progressive RNFL loss when compared to a standard GAT prism measured IOP. PRéCIS: A modified applanation surface prism with a corneal conforming shape used on a Goldmann tonometer appears to be a more sensitive and reliable indicator of progressive glaucomatous optic neuropathy as measured by retinal nerve fiber layer changes.

Keywords: Corneal biomechanics; Corneal hysteresis; Glaucoma; Glaucomatous optic neuropathy; OCT; Retinal nerve fiber layer; Tonometry.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: This clinical study was conducted in accordance with the ethical principles contained within Declaration of Helsinki, Protection of Human Volunteers (21 CFR 50), and Obligations of Clinical Investigators (21 CFR 812). The study was completed using retrospective data analysis on deidentified data, therefore IRB approval was not sought. The U.S. Department of Health and Human Services (HHS) regulations under 45 CFR 46.101(b), research involving the collection or study of existing data, documents, records, or specimens can be exempt from IRB review if these sources if the information is recorded by the investigator in such a manner that subjects cannot be identified, directly or through identifiers linked to the subjects. This is outlined in 45 CFR 46.104(d)(4) of the revised Common Rule. Consent for publication: N/A. Competing interests: Only Author Sean McCafferty has a competing interest: The Submitted manuscript titled"Intraocular Pressure Correlation to Progressive Retinal Nerve Fiber Layer Loss in Primary Open Angle Glaucoma as measured by Standard and Modified Goldmann Applanation Tonometers"was completed by referencing studies with funding from an NIH/NEI SBIR grant 1R43 EY026821 - 01. Requirements of this grant are commercialization of potentially beneficial ophthalmic/optometric medical devices/products. The commercialization necessitates intellectual property and a company to produce the product. Commonly in new technology start-up companies (and in this case), an author is also part owner in the intellectual property and the associated company (Intuor Technologies). This is a conflict of interest. However, the authors attest to the stringent efforts made to provide unbiased information provided in this manuscript.

Figures

Fig. 1
Fig. 1
- RNFL loss in POAG (annualized) verses average IOP measured by a standard and modified Goldmann prism
Fig. 2
Fig. 2
- RNFL loss in POAG (annualized) verses average paired differential IOP modified minus standard Goldmann prism measurements
See this image and copyright information in PMC

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