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Naveed Nilforushan, Kouros Nouri-Mahdavi, Nariman Nassiri, Dennis Mock, Anne Coleman, Simon Law, JoAnn Giaconi, Joseph Caprioli; Structure-Function Relationships Are Linear in Early Glaucoma. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5084.
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© ARVO (1962-2015); The Authors (2016-present)
To explore whether structure-function relationships, as evaluated with retinal nerve fiber layer (RNFL) thickness measurement and achromatic visual fields or short wavelength automated perimetry (SWAP), can be detected in early glaucoma.
One-hundred eighteen eyes of 78 patients with early or suspected glaucoma were selected from the clinical database at UCLA’s Glaucoma Division. All patients had a spectral-domain optical coherence tomography (SD-OCT) RNFL image (optic disc cube 200x200, Cirrus OCT, Carl Zeiss Meditec, Inc) and a reliable 24-2 SITA-Standard (Group A: MD better than -5.0 dB; 73 eyes) or SWAP (Group B: 45 eyes) Humphrey visual field within a 6-month period. The OCT images were required to be well focused, have a signal strength more than or equal to 7 and average RNFL thickness more than or equal to 80 microns. Canonical correlation analyses were used to determine the correlation between the average RNFL thickness in 10-degree OCT sectors on the OCT’s circumpapillary measurement circle (diameter 3.46 mm) and 52 individual visual field locations (excluding points above and below the blind spot) grouped in 4 main regions (superior, inferior, temporal, and central clusters). The correlation between the first canonical coefficients from the structural and functional measures was the main outcome measure.
The average RNFL thickness was 88.6 ± 5.7 and 88.6 ± 4.9 microns in Group A and B, respectively. The average mean deviation was -1.0 ± 1.7 dB in Group A and -0.61 ± 3.4 dB in Group B. All the first canonical coefficients for the correlations between inferior, superior, central, and temporal regions of the visual field vs. corresponding regions of the RNFL were significant for both groups (Rc = 0.81, 0.81, 0.57, and 0.52 in Group A and Rc = 0.91, 0.98, 0.71, and 0.74, respectively in Group B; p <0.001 for all). The structure-function relationship between the corresponding regions of visual field and peripapillary RNFL was mostly linear.
Structure-function relationships seem to be linear in early glaucoma and can be detected if more localized measures of RNFL or visual field are employed.
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