Comparison of Blue-Light Autofluorescence and Ultrawidefield Green-Light Autofluorescence for Assessing Geographic Atrophy.

PURPOSE: The goal of this study was to evaluate and compare the intermodality and interreader agreement of manual and semiautomated geographic atrophy (GA) area measurements in eyes with GA due to age-related macular degeneration (AMD) using conventional blue-light fundus autofluorescence (FAF) and ultrawidefield (UWF) green-light FAF systems. DESIGN: Prospective Cohort Study. SUBJECTS: Seventy-two eyes of 50 patients with a diagnosis of advanced nonneovascular AMD with GA. METHODS: Fundus autofluorescence images of eyes with GA were obtained during a single visit using both the Spectralis HRA + OCT2 device and the Optos California device. The area of the GA lesion(s) was segmented and quantified (mm2) with a fully manual approach where the lesions were outlined using Optos Advance and Heidelberg Eye Explorer (HEYEX) software. In addition, for the Heidelberg blue FAF images, GA lesions were also measured using the instrument's semiautomated software (Region Finder 2.6.4). For comparison between modalities/grading method, the mean values of the 2 graders were used. Intraclass correlation coefficients were computed to judge the agreement between graders. RESULTS: Seventy-two eyes of 50 patients were included in this study. There was nearly perfect agreement between graders for the measurement of GA area for all 3 modalities (intraclass correlation coefficient: 0.996 for manual Optos Advance, 0.996 for manual Heidelberg HEYEX, and 0.995 for Heidelberg Region Finder). The measurement of GA area was strongly correlated between modalities, with Spearman correlation coefficients of 0.985 (P < 0.001) between manual Heidelberg and manual Optos, 0.991 (P < 0.001) for Region Finder versus manual Heidelberg, and 0.985 (P < 0.001) for Region Finder versus manual Optos. The absolute mean area differences between the Heidelberg manual versus Region Finder, manual Optos versus Region Finder, and manual Optos versus manual Heidelberg were 1.61 mm2 (P < 0.001), 0.90 mm2 (P < 0.006), and 0.71 mm2 (P < 0.001), respectively. CONCLUSIONS: We observed excellent interreader agreement for measurement of GA using either 30-degree blue-light FAF or UWF green-light FAF, establishing the reliability of UWF imaging for macular GA assessment. Although the absolute measurements between devices were strongly correlated, they differed significantly, highlighting the importance of using the same device for a given patient for the duration of a study. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

A New Method of Magnification Correction for Accurately Measuring Retinal Vessel Calibers From Fundus Photographs.

Purpose: To report a semiautomated retinal vessel caliber measurement system that measures central retinal artery (vein) equivalent (CRAE [CRVE]) with individual correction for magnification errors under conditions assuming optimal focus. Methods: The focusing condition of the subject eye fundus camera optical system was individually determined by constructing an optical model of each eye applying its refractive error, corneal curvature, and axial length (AL) to Gullstrand's schematic eye, and by adjusting the position of the camera's focusing lenses using each eye's refractive error. Once the focusing condition of the entire optical system was fulfilled, magnification of the fundus images was calculated using paraxial ray tracing. Measurements of CRAE (CRVE) were performed in an annular area centered on the optic disc with magnification-corrected diameter from 1.8 to 2.7 mm. Reproducibility of the measurements of the results using the new method and comparison with those using interactive vessel analysis (IVAN) were performed in normal Japanese eyes. Results: Intra- and interexaminer intraclass correlation coefficient (ICC) for CRAE (CRVE) measurements was greater than 0.978. CRAE (CRVE) using the new method averaged 148.9 ± 10.9 µm (225.0 ± 13.9 µm; mean ± SD, N = 99). Differences between the new method and IVAN were greater with increasing AL (P < 0.001). The new method yielded CRAE (CRVE) in good agreement with IVAN in eyes with AL of approximately 24 mm. However, the new method yielded smaller values in eyes with shorter AL and vice versa. Conclusions: A new accurate and reproducible method to measure CRAE (CRVE) from fundus photographs was reported.

Effect of age and disc size on rim order rules by Heidelberg Retina Tomograph.

PURPOSE: The ISNT rule for nonglaucomatous eyes suggests that the neuroretinal rim is thickest at the inferior quadrant (I), followed by the superior (S), nasal (N), and temporal (T) quadrants. This study aimed to use Heidelberg Retina Tomograph (HRT III) measurements to assess (a) fulfillment of the ISNT rule and its derivatives in a large normative database and (b) effect of disc size and age on rule fulfillment. PATIENTS AND METHODS: A multicenter, prospective, cross-sectional study of a Caucasian normative database consisting of 280 subjects with normal comprehensive biomicroscopic examination, intraocular pressure <21 mm Hg, and normal automated visual field testing was conducted. Right eye neuroretinal rim and disc area, measured by HRT III, for each of the 4 quadrants were analyzed. Compliance of the rim area to the ISNT rule (I≥S≥N≥T) and its derivates was determined. Effect of age and disc area on rule compliance was further determined. RESULTS: Only 18% of normal eyes had rim areas that complied with the ISNT rule; however, a majority complied to IS (77%) and IST (73%) rules. The temporal quadrant had the smallest rim area [(I,S,N)>T] in 91% of patients. The likelihood of ISNT rule violation was increased in larger discs (χ², P=0.003) but was not affected by age. CONCLUSIONS: The ISNT rule does not apply to neuroretinal rim area as measured by HRT, as only 18% of the eyes complied with the ISNT rule in this normative database. Although the ISNT rule may be more applicable to normal eyes with a smaller disc area, the IS and IST rules seem to better represent the normative database.

Human perceptual performance with nonliteral imagery: region recognition and texture-based segmentation.

In this study the authors address the issue of how the perceptual usefulness of nonliteral imagery should be evaluated. Perceptual performance with nonliteral imagery of natural scenes obtained at night from infrared and image-intensified sensors and from multisensor fusion methods was assessed to relate performance on 2 basic perceptual tasks to fundamental characteristics of the imagery. Specifically, single-sensor imagery and fused multisensor imagery (both achromatic and false color) were used to test performance on a region recognition task and a texture segmentation task. Results indicate that the use of color rendering and type of scene content play specific roles in determining perceptual performance allowed by nonliteral imagery. The authors argue that the usefulness of various image-rendering methods should be evaluated with respect to multiple perceptual tasks.

Fourier analysis of optical coherence tomography and scanning laser polarimetry retinal nerve fiber layer measurements in the diagnosis of glaucoma.

OBJECTIVE: To evaluate a new Fourier-based analysis method for diagnosing glaucoma using retinal nerve fiber layer (RNFL) thickness estimates obtained from the optical coherence tomograph (OCT) (OCT 2000) and the scanning laser polarimeter (GDx). METHODS: We obtained RNFL thickness estimates from 1 eye of 38 healthy individuals and 42 patients with early glaucomatous visual field loss using the OCT and GDx devices. The shape of the RNFL double-hump pattern was assessed using Fourier analysis, and values were entered into a linear discriminant analysis. Receiver operating characteristic (ROC) curves were used to compare the performance of the Fourier-based metrics against other commonly used RNFL analytical procedures. Reliability was assessed on independent samples by the split-half method. Correlations were calculated to determine the extent to which the Fourier discriminant measures and other RNFL measures covaried between the 2 devices and the relationship between these RNFL measures and visual field measures. RESULTS: Sensitivity and specificity for the linear discriminant function (LDF) based on the Fourier analysis of the OCT data were 76% and 90%, respectively, and the area under the ROC curve was 0.925 (SEM, 0.028). For the GDx data, the Fourier-based LDF yielded sensitivity and specificity of 82% and 90%, respectively, with an ROC curve area of 0.928 (SEM, 0.029). These values were better than those determined using the GDx number, a previous discriminant function using GDx variables and OCT thickness values. The Fourier-based LDFs and numerous other measures were significantly correlated between the 2 devices. For each device, the visual field measures correlated most highly with the Fourier-based LDF measure. CONCLUSIONS: For both devices, the LDF based on the output from a Fourier analysis of RNFL data resulted in better diagnostic capability compared with other common RNFL analytical procedures. That this technique improves RNFL analysis is also supported by the better correlations between visual field measures and the Fourier-based LDF measures.

Oblique stimuli are seen best (not worst!) in naturalistic broad-band stimuli: a horizontal effect.

People with normal eyesight typically see horizontal and vertical gratings better than oblique gratings (Psychological Bulletin 78 (1972) 266; Perception 9 (1980) 37). In the present study we investigated whether this oblique effect anisotropy is still observed when viewing more complex visual stimuli that better correspond to the content encountered in everyday viewing of the world. We show that the ability to see oriented structure in an image consisting of broadband spatial content is indeed anisotropic, but that the pattern of this orientation bias is completely different from that obtained with simpler stimuli. Horizontal stimuli are seen worst and oblique stimuli are seen best when tested with more realistic broadband stimuli. We suggest that this "horizontal effect" would be useful in an evolutionary capacity by serving to discount the horizon and other oriented content that tends to dominate natural scenes and thereby increase the salience of objects contained in typical outdoor scenes.

Psychophysical assessments of image-sensor fused imagery.

The goal of this study was to determine the perceptual advantages of multiband sensor-fused (achromatic and chromatic) imagery over conventional single-band nighttime (image-intensified and infrared) imagery for a wide range of visual tasks, including detection, orientation, and scene recognition. Participants were 151 active-duty military observers whose reaction time and accuracy scores were recorded during a visual search task. Data indicate that sensor fusion did not improve performance relative to that obtained with single-band imagery on a target detection task but did facilitate object recognition, judgments of spatial orientation, and scene recognition. Observers' recognition and orientation judgments were improved by the emergent information within the image-fused imagery (i.e., combining dominant information from two or more sensors into a single displayed image). Actual or potential applications of this research include the deployment of image-sensor fused systems for automobile, aviation, and maritime displays to increase operators' visual processing during low-light conditions.