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.
Received 19 July 2006; accepted 5 October 2006. published online 06 February 2007.
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.
Hamilton Glaucoma Center, Department of Ophthalmology, University of California, San Diego, California.
Correspondence to Christopher Bowd, PhD, Hamilton Glaucoma Center, Department of Ophthalmology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0946.
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.
ABSTRACT