One hundred and twenty-six subjects followed up in our institution were included in the study. The tenets of the Declaration of Helsinki and Spanish legislation were adhered to and the Institutional Review Board approved the study protocol. Each patient signed an informed consent after receiving a detailed explanation of the nature of the study procedures. Only one eye from each patient was included (better eye). The subjects underwent complete ophthalmic examination, including a review of the medical history, slit-lamp biomicroscopy, intraocular pressure (IOP) measurement, extraocular motility examination, fundus examination, and standard automated perimetry. Humphrey Automated Field Analyzer II (Carl Zeiss Meditec, Dublin, CA) with SITA STANDARD 24-2 protocol was used. Only visual fields with fewer than 33% false-negative errors, fewer than 33% false-positive errors, and fewer than 20% fixation losses were considered. A normal visual field was required for the healthy group. Glaucomatous eyes had an IOP greater than 21 mm Hg and reliable pathologic visual fields. All eyes included in the study had a best-corrected visual acuity of 20/40 or better, sphere within ±5.0 diopters (D), cylinder within ±3.0 D, and absence of peripapillary atrophy, disc tilt, or papillary abnormalities (other than glaucomatous abnormalities in the glaucoma group). Subjects who had undergone intraocular surgery (other than trabeculectomy) or who were currently using medication that could affect visual field sensitivity were excluded from the study. Laser trabeculoplasty (selective or argon) or the use of hypotensive drops was not considered exclusion criteria for this study.
To stage glaucomatous visual field loss severity, we used the method proposed by Hodapp et al.
12 based on the overall extent of the damage, the number of defective points in the deviation probability map, and the proximity of the defect to fixation point. Early glaucomatous visual fields had mean deviation between −2 and −6 dB, fewer than 25% of the points were depressed below the 5% level and fewer than 10 points were depressed below 1% on the pattern deviation plot, and all points in the central 5° had a sensitivity of at least 15 dB. Moderate glaucomatous visual fields had mean deviation less than −12 dB; fewer than 50% of the points were depressed below the 5% level and fewer than 20 points were depressed below 1% on the pattern deviation plot; and no points in the central 5° had a sensitivity of 0 dB, and no more than one hemifield had a sensitivity of less than 15 dB within 5° of fixation. Sixty-six eyes were categorized as healthy, 30 were classified as early glaucomatous, and 30 as moderate glaucomatous.
The Spectralis SDOCT (software version 5.3, including the FoDi software) fast RNFL examination protocol was used. All pupils were first dilated with 1% tropicamide (Colircusi Tropicamida 1%; Alcon Cusi, SA, Barcelona, Spain). A minimum image quality score of 35 was required. Image acquisition was repeated if the quality was insufficient. The fundus image allowed for surveillance of the fovea and disc during imaging acquisition. Internal fixation was encouraged. The same investigator performed all scans and adequately relocated the fovea of the intermediate image when internal fixation failed owing to poor patient cooperation. This final image was considered as the baseline for each patient. Relocation of the fovea was allowed even on a day different from the acquisition day in the new FoDi software when “RNFL acquisition protocol with FoDi enhancement” was being used. This option would have not been available if the “circle scan” protocol had been used because in this regimen, the reference point is the center of the circle and not the fovea.
By manually lowering the position of the fovea, the baseline image was modified without requiring the presence of the patient (the position of the fovea was edited after the initial image acquisition): clockwise torsion of the scan disc of 5°, 10°, and 15° from the original fovea–disc alignment. By raising the position of the fovea, counterclockwise torsion of 5° and 10° was created (
Fig. 1). Further counterclockwise torsion was not induced, because it resulted in foveal simulated positions that were superior to that of the optic nerve head in all subjects. As this foveal location is extremely rare according to the results of population studies,
13 we considered only those situations that might lead to errors in actual clinical practice. Thus, the five created images for each patient were the result of postacquisition manipulation of baseline images and did not include successive imaging.
New analyses of these images were performed. Total mean and quadrant (I, S, N, T, and superior temporal [ST], superior nasal [SN], inferior temporal [IT], and inferior nasal [IN] subdivisions of T and N in the second pie chart) thickness measurements were recorded for the analysis.
Normality of quantitative data was analyzed with Shapiro-Wilk test. Quantitative variables were expressed as their corresponding means and standard deviations. Differences in total mean and sector thickness between baseline images and modified images were assessed by using ANOVA test. Least significant difference Fisher test was conducted post hoc if ANOVA showed statistical significance. Percentage of eyes with color change in each sector was calculated for all groups. All analyses were performed by using SPSS software version 18.0 (SPSS, Inc., Chicago, IL). A P value of less than 0.05 was considered statistically significant.