Elsevier

Ophthalmology

Volume 114, Issue 7, July 2007, Pages 1259-1265
Ophthalmology

Original Article
Retinal Nerve Fiber Layer Thickness and Visual Sensitivity Using Scanning Laser Polarimetry with Variable and Enhanced Corneal Compensation

Presented at: the Fourth Annual International Society for Imaging in Eye meeting, May 2006, Fort Lauderdale, Florida.
https://doi.org/10.1016/j.ophtha.2006.10.020Get rights and content

Purpose

To compare the strength of the structure–function association between scanning laser polarimetry-measured retinal nerve fiber layer (RNFL) thickness and visual sensitivity. Two methods of corneal compensation were evaluated, variable corneal compensation (VCC) and enhanced corneal compensation (ECC).

Design

Observational case series.

Participants

One hundred twenty-seven glaucoma (repeatable abnormal visual fields [VF] by pattern standard deviation and/or glaucoma hemifield test) or glaucoma suspect (glaucomatous-appearing discs by photograph assessment without field defects) participants in the University of California, San Diego Diagnostic Innovations in Glaucoma Study.

Methods

One eye of each participant was imaged using GDx VCC and GDx ECC on the same day. Visual fields tested using the Humphrey Field Analyzer (with Swedish interactive threshold algorithm) were obtained within 6 months of imaging.

Main Outcome Measure

The associations (R2) using linear and logarithmic regression between RNFL thicknesses measured in 6 sectors (inferior, inferotemporal, temporal, superotemporal, superior, nasal) with VCC and ECC and VF sensitivities (decibel threshold measurements) measured in 6 corresponding sectors were compared. Comparisons were made using paired t tests on the log-transformed absolute values of regression residuals.

Results

Using GDx VCC, 32 scans had a typical scan score (TSS) ≤ 78 (lowest quartile) and no ECC scans had TSS<86. Most RNFL thickness measurements obtained using GDx VCC were significantly greater than those measured using GDx ECC. Regional structure–function associations (R2) ranged from 0.03 (temporal RNFL) to 0.22 (superotemporal RNFL) for VCC and from 0.01 (temporal RNFL) to 0.26 (superotemporal RNFL) for ECC. Associations generally were slightly stronger for ECC than for VCC, although these differences were only significant for inferotemporal RNFL (R2 = 0.19 and 0.11, for ECC and VCC, respectively).

Conclusion

The RNFL thickness associations with VF sensitivity are stronger using ECC compared with VCC, suggesting that ECC provides a better cross-sectional representation of visual function than VCC.

Section snippets

Participants

One eye each from 127 glaucoma patients or glaucoma suspects (criteria below) enrolled in the University of California, San Diego–based longitudinal Diagnostic Innovations in Glaucoma Study was studied. All participant eyes had good quality GDx-VCC and GDx-ECC images obtained on the same day. A reliable visual field (VF) test within 6 months also was required.

Each study participant underwent a comprehensive ophthalmologic evaluation including review of medical history, best-corrected visual

Retinal Nerve Fiber Layer Thickness Differences

Significant differences in RNFL thickness measured using VCC compared with ECC were found in the temporal, superotemporal and nasal circumpapillary sectors. In all significant cases, ECC measurements were lower than VCC measurements. Differences were greatest in the temporal RNFL (Δ RNFL thickness = 10.49 μm) followed by the superotemporal RNFL (Δ RNFL thickness = 5.23 μm) and the nasal RNFL (Δ RNFL thickness = 3.04 μm; Table 1). In addition, TSS was significantly different for VCC (mean, 85.4;

Discussion

This study showed that measurements of RNFL thickness differed between SLP using VCC and ECC, but only in the temporal, superotemporal, and nasal circumpapillary regions. In addition, although structure–function associations were generally stronger using ECC compared with VCC, this difference was only significant between inferotemporal RNFL measurements and superonasal VF sensitivity measurements. The second finding was somewhat surprising because we assumed that increased strength of

References (19)

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Manuscript no. 2006-805.

Supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior/Ministério da Educação e Cultura, Brasília, Brazil, and the National Institutes of Health, Bethesda, Maryland (grant nos. EY11008, EY08208). Participant retention incentive grants in the form of glaucoma medication at no cost: Alcon Laboratories Inc., Allergan, Pfizer Inc., and SANTEN Inc.

1

Drs Medeiros, Zangwill, Sample, and Weinreb received research funding and/or research materials at no cost from Carl Zeiss Meditec. Drs Zangwill and Weinreb received research funding and/or research materials at no cost from Heidelberg Engineering. Dr Zangwill received gifts in kind, honoraria, or travel reimbursement valued at >$1000 in the last 12 months from Heidelberg Engineering. Dr Weinreb received gifts in kind, honoraria, or travel reimbursement valued at >$1000 in the last 12 months from Carl Zeiss Meditec and Heidelberg Engineering.

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