Mr. Hubbard is a researcher in the Department of Ophthalmology and Visual Sciences at the University of Wisconsin School of Medicine and Public Health. He is also Associate Director-Image Grading, Fundus Photograph Reading Center, Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison. His research has included developing an ordinal scale to express the severity of diabetic retinopathy and designing the Reading Center's grading program for evaluating treatment of infection that can lead to blindness in patients with AIDS.
Effect of image compression and resolution on retinal vascular caliber.
Invest Ophthalmol Vis Sci. 2012 Aug;53(9):5117-23
Authors: Pauli TW, Gangaputra S, Hubbard LD, Thayer DW, Chandler CS, Peng Q, Narkar A, Ferrier NJ, Danis RP
PURPOSE: Changes in retinal vascular caliber measured from digital color fundus photographs have been independently associated with systemic outcomes in epidemiologic studies, but the effect of image resolution and compression on vascular measurements has not been previously evaluated.
METHODS: To explore image compression, 40 natively digital fundus images were selected with good photo quality, high spatial resolution, and no previous image compression. Using Adobe Photoshop, these images were compressed at progressively higher levels up to 147:1, and then retinal vascular caliber was measured at each level using semiautomated software. To examine resolution, 40 fundus photographs acquired on high-resolution film were scanned with settings corresponding to 10, 7, 5, 3, and 1 megapixel fundus cameras. After adjusting for scale factor, vascular caliber was measured at each level of resolution. Data were analyzed by comparing the calculated central retinal arteriole equivalent (CRAE) and the central retinal venular equivalent (CRVE) of the original and altered images, using repeated measures ANOVA.
RESULTS: CRAE became significantly wider with increasing levels of compression at the 25:1 threshold (~1 μm wider, P < 0.001) and was ~5 μm wider with 147:1 compression. CRVE also increased, but less than CRAE. Using 7 (megapixel)-MP resolution as the standard, CRVE was significantly narrower at the 5-MP simulation (~2 μm, P < 0.001) and was ~12 μm narrower at the 1-MP simulation. CRAE also decreased, but less than CRVE.
CONCLUSIONS: Increasing digital image file compression and decreasing fundus image spatial resolution led to skewed measurements of the retinal vascular caliber.
PMID: 22736618 [PubMed - indexed for MEDLINE]
Retinal vessel caliber among people with acquired immunodeficiency syndrome: relationships with visual function.
Am J Ophthalmol. 2012 Mar;153(3):428-433.e1
Authors: Kalyani PS, Fawzi AA, Gangaputra S, van Natta ML, Hubbard LD, Danis RP, Thorne JE, Holland GN, Studies of the Ocular Complications of AIDS Research Group
PURPOSE: To evaluate relationships between retinal vessel caliber and tests of visual function among people with AIDS.
DESIGN: Longitudinal, observational cohort study.
METHODS: We evaluated data for participants without ocular opportunistic infections at initial examination (baseline) in the Longitudinal Studies of the Ocular Complications of AIDS (1998-2008). Visual function was evaluated with best-corrected visual acuity, Goldmann perimetry, automated perimetry (Humphrey Field Analyzer), and contrast sensitivity (CS) testing. Semi-automated grading of fundus photographs (1 eye/participant) determined central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and arteriole-to-venule ratio (AVR) at baseline. Multiple linear regression models, using forward selection, sought independent relationships between indices and visual function variables.
RESULTS: Included were 1250 participants. Smaller AVR was associated with reduced visual field by Goldmann perimetry (P = .003) and worse mean deviation (P = .02) on automated perimetry and possibly with worse pattern standard deviation (PSD) on automated perimetry (P = .06). There was a weak association between smaller AVR and worse CS (P = .07). Relationships were independent of antiretroviral therapy and level of immunodeficiency (CD4+ T lymphocyte count, human immunodeficiency virus [HIV] RNA blood level). On longitudinal analysis, retinal vascular indices at baseline did not predict changes in visual function.
CONCLUSIONS: Variation in retinal vascular indices is associated with abnormal visual function in people with AIDS, manifested by visual field loss and possibly by reduced CS. Relationships are consistent with the hypothesis that HIV-related retinal vasculopathy is a contributing factor to vision dysfunction among HIV-infected individuals. Longitudinal studies are needed to determine whether changes in indices predict change in visual function.
PMID: 22019221 [PubMed - indexed for MEDLINE]
Retinal vessel caliber among people with acquired immunodeficiency syndrome: relationships with disease-associated factors and mortality.
Am J Ophthalmol. 2012 Mar;153(3):434-444.e1
Authors: Gangaputra S, Kalyani PS, Fawzi AA, Van Natta ML, Hubbard LD, Danis RP, Thorne JE, Holland GN, Studies of the Ocular Complications of AIDS Research Group
PURPOSE: To evaluate relationships between retinal vessel caliber, AIDS-related factors, and mortality.
DESIGN: Longitudinal, observational cohort study.
METHODS: We evaluated data for participants without ocular opportunistic infections at initial examination (baseline) in the Longitudinal Studies of the Ocular Complications of AIDS (1998-2008). Semi-automated evaluation of fundus photographs (1 eye/participant) determined central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and arteriole-to-venule ratio (AVR) at baseline. Multiple linear regression models, using forward selection, identified independent relationships between indices and various host- and disease-related variables.
RESULTS: Included were 1250 participants. Mean follow-up for determination of mortality was 6.1 years. Smaller CRAE was related to increased age (P < .001) and hypertension (P < .001); larger CRAE was related to lower hematocrit (P = .002). Larger CRAE and CRVE were associated with black race (P < .001). Larger CRVE was related to smoking (P = .004); smaller CRVE was related to age (P < .001) and higher mean corpuscular volume (P = .001). We observed the following relationships with AIDS-associated factors: smaller CRAE and larger CRVE with history of highly active antiretroviral therapy (HAART; P < .001); and larger CRAE with lower CD4+ T lymphocyte count (P = .04). We did not identify independent relationships with human immunodeficiency virus RNA blood levels. There was a 12% (95% CI, 2%-21%) increase in mortality risk per quartile of decreasing AVR (P = .02).
CONCLUSIONS: Variations in retinal vascular caliber are associated with AIDS-specific factors and are markers for increased mortality risk. Relationships are consistent with the hypothesis that the vasculature is altered by known atherogenic effects of chronic HAART or the prolonged inflammatory state associated with AIDS.
PMID: 22019225 [PubMed - indexed for MEDLINE]
Transition from film to digital fundus photography in the Longitudinal Studies of the Ocular Complications of AIDS.
Retina. 2012 Mar;32(3):600-5
Authors: Gangaputra S, Pak JW, Peng Q, Hubbard LD, Thayer D, Krason Z, Joyce J, Danis RP, Studies of the Ocular Complications of AIDS Research Group
PURPOSE: To describe the transition to digital imaging and assess any impact on ocular disease classification.
METHODS: Film and digital images, acquired by certified photographers, were evaluated independently according to standard procedures for the following: image quality, presence of cytomegalovirus retinitis lesions, and their extent and proximity from disk and macula. Intergrader agreement within the digital medium was also assessed.
RESULTS: Among the 15 eyes with cytomegalovirus retinitis, the mean difference between film and digital images for linear distance of lesion edge to disk was 0.02 disk diameters, for distance to center of macula was -0.04 disk diameters, and area covered by cytomegalovirus retinitis was 0.95 disk area. There was no statistically significant difference in distance and area measurements between media. Intergrader agreement in measurements of digital images was excellent for distance and area estimated.
CONCLUSION: Our results suggest that digital grading of cytomegalovirus retinitis in Longitudinal Studies of the Ocular Complications of AIDS is comparable with that from film regarding disease classification, measurements, and reproducibility. These findings provide support for continuity of grading data, despite the necessary transition in imaging media.
PMID: 21857393 [PubMed - indexed for MEDLINE]
Mosaics versus Early Treatment Diabetic Retinopathy seven standard fields for evaluation of diabetic retinopathy severity.
Retina. 2011 Sep;31(8):1553-63
Authors: Li HK, Esquivel A, Hubbard LD, Florez-Arango JF, Danis RP, Krupinski EA
PURPOSE: To compare agreement between mosaicked and seven field photographs for classification of the diabetic retinopathy (DR) severity.
METHODS: Mosaic digital (MosD) images were compared with seven field stereo film (7FF) and stereo digital (7FD) photographs from a 152-eye cohort with full-spectrum Early Treatment of Diabetic Retinopathy severity levels for agreement on severity level, DR presence with ascending severity thresholds, DR index lesion presence, and classification repeatability.
RESULTS: There was a substantial agreement classifying the Early Treatment Diabetic Retinopathy Study DR severity level between MosD and 7FF (kunweighted = 0.59, klinear weighted = 0.83), MosD and 7FD (κ = 0.62, κ weighted = 0.86), and 7FD and 7FF (κ = 0.62, κ weighted = 0.86) images. Marginal homogeneity analyses found no significant difference between MosD and 7FF (P = 0.44, Bhapkar's test). Kappa between MosD and 7FF ranged from 0.75 to 0.91 for the presence or absence of DR at 8 ascending severity thresholds. Repeatability among readers using MosD images was similar to repeatability among those using 7FF or 7FD. Repeatability among readers using MosD and 7FF images at various severity thresholds was similar. Kappa between MosD and 7FF grading for identifying DR lesions ranged from 0.61 to 1.00.
CONCLUSION: Mosaic images are generally comparable with standard seven-field photographs for classifying DR severity.
PMID: 21522039 [PubMed - indexed for MEDLINE]
Imaging of diabetic retinopathy and diabetic macular edema.
Curr Diab Rep. 2011 Aug;11(4):236-43
Authors: Danis RP, Hubbard LD
Imaging of the retinal complications of diabetes mellitus is rapidly changing from the emergence of new technology such as optical coherence tomography. In particular, the characterization of diabetic macular edema is much easier for the clinician and there are new, more sensitive clinical research end points. However, our understanding of structure-functional relationships remains suboptimal and the classification of macular edema by optical coherence tomography continues to evolve. The classification of diabetic retinopathy severity continues to rely upon fundus photography, although the transition from film to digital photography presents both challenges and advantages.
PMID: 21607565 [PubMed - indexed for MEDLINE]
Comparison of digital and film grading of diabetic retinopathy severity in the diabetes control and complications trial/epidemiology of diabetes interventions and complications study.
Arch Ophthalmol. 2011 Jun;129(6):718-26
Authors: Hubbard LD, Sun W, Cleary PA, Danis RP, Hainsworth DP, Peng Q, Susman RA, Aiello LP, Davis MD, Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study Research Group
OBJECTIVE: To compare diabetic retinopathy (DR) severity as evaluated by digital and film images in a long-term multicenter study, as the obsolescence of film forced the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study (DCCT/EDIC) to transition to digital after 25 years.
METHODS: At 20 clinics from 2007 through 2009, 310 participants with type 1 diabetes with a broad range of DR were imaged, per the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol, with both film and digital cameras. Severity of DR was assessed centrally from film and tonally standardized digital cameras. For retinopathy outcomes with greater than 10% prevalence, we had 85% or greater power to detect an agreement κ of 0.7 or lower from our target of 0.9.
RESULTS: Comparing DR severity, digital vs film yielded a weighted κ of 0.74 for eye level and 0.73 for patient level ("substantial"). Overall, digital grading did not systematically underestimate or overestimate severity (McNemar bias test, P = .14). For major DR outcomes (≥3-step progression on the ETDRS scale and disease presence at ascending thresholds), digital vs film κ values ranged from 0.69 to 0.96 ("substantial" to "nearly perfect"). Agreement was 86% to 99%; sensitivity, 75% to 98%; and specificity, 72% to 99%. Major conclusions were similar with digital vs film gradings (odds reductions with intensive diabetes therapy for proliferative DR at EDIC years 14 to 16: 65.5% digital vs 64.3% film).
CONCLUSION: Digital and film evaluations of DR were comparable for ETDRS severity levels, DCCT/EDIC design outcomes, and major study conclusions, indicating that switching media should not adversely affect ongoing studies.
PMID: 21670338 [PubMed - indexed for MEDLINE]
Comparability of digital photography with the ETDRS film protocol for evaluation of diabetic retinopathy severity.
Invest Ophthalmol Vis Sci. 2011 Jun;52(7):4717-25
Authors: Li HK, Danis RP, Hubbard LD, Florez-Arango JF, Esquivel A, Krupinski EA
PURPOSE: To evaluate digital photography parameters affecting comparability with the Early Treatment Diabetic Retinopathy Study (ETDRS) film protocol for diabetic retinopathy (DR) severity grading.
METHODS: ETDRS protocol photographs and four variations of digital images (uncompressed stereoscopic, compressed stereoscopic, uncompressed monoscopic, and uncompressed monoscopic wide-angle mosaic) of 152 eyes were independently evaluated by using ETDRS classifications. Digital formats were compared to film and each other for agreement on severity level, DR presence at ascending threshold, presence of the DR index lesion, and repeatability of grading. Study parameters included image resolution sufficient to distinguish small lesions, color balancing of digital images to film, documenting essential ETDRS classification retinal regions, similar magnification, and supplementary green-channel viewing.
RESULTS: The κ statistic was substantial or near substantial between all digital formats and film for classifying severity levels (κ = 0.59-0.62; κ(w) [linear weighted] = 0.83-0.87). The distribution of DR levels in all digital formats was not significantly different from that of the film (Bhapkar test, P = 0.09-0.44). The κ among digital formats for severity level was also substantial or near substantial (κ = 0.58-0.76, κ(w) = 0.82-0.92). Differences between digital formats and film for grading severity level, severity threshold, or index lesions were not significant. The repeatability of grading between readers using film and all digital formats was also similar.
CONCLUSIONS: Digital format variations compared favorably with film for DR classification. Translating film characteristics (resolution, color/contrast) and protocol (magnification, retinal regions) to digital equivalents and augmentation of full color with green-channel viewing most likely contributed to the results.
PMID: 21345979 [PubMed - indexed for MEDLINE]
Suboptimal image focus broadens retinal vessel caliber measurement.
Invest Ophthalmol Vis Sci. 2011;52(12):8558-61
Authors: Chandler CS, Gangaputra S, Hubbard LD, Ferrier NJ, Pauli TW, Peng Q, Thayer DW, Danis RP
PURPOSE: Studies have used central retinal arteriolar (CRAE) and central retinal venular (CRVE) calibers, measured from images produced with computerized image analysis, to detect risk factors for systemic diseases. The authors explored suboptimal image focus as a possible contributing factor to artificially larger vascular caliber measurements.
METHODS: From the reading center image collections, 30 digital retinal images were selected for optimum quality. Image analysis software was used to derive nine progressively blurred versions of the originals. IVAN measurement software was used to measure CRAE and CRVE in the original and the blurred series derived from them. To check the adequacy of the simulation, progressively defocused series of images were taken of several volunteers.
RESULTS: For CRAE, each level of simulated blurring produced a statically significant increase in apparent vessel caliber from the original (P<0.01, Wilcoxon signed rank test). For an average CRAE of 160 μm, mean broadening with minimal/moderate/severe blurring was 3 μm/12 μm/33 μm. For CRVE, every blurring level beyond the first was found to be significant (P<0.01). From an average CRVE of 200 μm, mean broadening ranged from 0 to 11 μm with minimal to severe blurring. Analysis of the progressively defocused series taken of volunteers yielded similar results overall.
CONCLUSIONS: Suboptimal focus can result in erroneously larger vessel caliber measurements. Slight blurring has a minimal effect, but more severe blurring has a progressively greater effect.
PMID: 21948645 [PubMed - indexed for MEDLINE]
Comparison of multiple stereoscopic and monoscopic digital image formats to film for diabetic macular edema evaluation.
Invest Ophthalmol Vis Sci. 2010 Dec;51(12):6753-61
Authors: Li HK, Hubbard LD, Danis RP, Florez-Arango JF, Esquivel A, Krupinski EA
PURPOSE: To assess agreement between evaluations of monoscopic and stereoscopic digital images versus stereo film photographs in diabetic macular edema (DME).
METHODS: A 152-eye group of digital monoscopic macular images (seven-field sets and wide-angle mosaics) were compared with digital stereoscopic images (uncompressed and compressed seven-field sets) and stereo 35-mm film photos (Early Treatment Diabetic Retinopathy Study protocol) for the presence of hard exudates (HE), retinal thickening (RT), clinically significant macular edema (CSME), and RT at the center of the macular (RTCM).
RESULTS: Agreement, according to the κ statistic, was almost perfect in identifying HE and RT between all digital formats and stereo film (HE, κ = 0.81-0.87; RT, κ = 0.87-0.92). Distribution in all digital formats was not significantly different from that in film (Bhapkar test: HE, P = 0.20-0.40; RT, P = 0.06-1.0). CSME and RTCM grading differences were either significant or trended toward significance. The readers detected CSME and RTCM in film images more often than in digital formats. In identifying DME features, agreement between evaluations of monoscopic digital formats and film was similar to that between stereo digital formats and film, and the performance of uncompressed images versus film was similar to that of compressed images versus film. Repeatability between readers was similar in evaluations of film and all digital formats. Repeatability in identifying RTCM was lower than that of other DME components in film and all digital formats.
CONCLUSIONS: Stereoscopic digital formats are equivalent to monoscopic for DME evaluation, but digital photography is not as sensitive as film in detecting CSME and RTCM.
PMID: 20574011 [PubMed - indexed for MEDLINE]
Evaluation of the age-related eye disease study clinical lens grading system AREDS report No. 31.
Ophthalmology. 2010 Nov;117(11):2112-9.e3
Authors: Chew EY, Kim J, Sperduto RD, Datiles MB, Coleman HR, Thompson DJ, Milton RC, Clayton JA, Hubbard LD, Danis RP, Ferris FL
PURPOSE: To examine the grading (interrater) reliability of the Age-Related Eye Disease Study (AREDS) Clinical Lens Grading System (ARLNS).
DESIGN: Evaluation of diagnostic test or technology.
PARTICIPANTS: One hundred fifty volunteers (284 eyes).
METHODS: Participants with lens opacities of varying severity were independently graded at the slit lamp for cataract severity by 2 examiners (retinal or anterior segment specialists) using the ARLNS, which employs 3 standard photographs of increasing severity for classifying each of the 3 major types of opacity. Lens photographs were taken and graded at a reading center using the more detailed AREDS System for Classifying Cataracts from photographs.
MAIN OUTCOME MEASURES: The Pearson correlation, weighted-kappa, and limits-of-agreement statistics were used to assess the interrater agreement of the gradings.
RESULTS: Examinations were performed on 284 lenses (150 participants). Tests of interrater reliability between pairs of clinicians showed substantial agreement between clinicians for cortical and posterior subcapsular opacities and moderate agreement for nuclear opacities. A similar pattern and strength of agreement was present when comparing scores of retinal versus anterior segment specialists. Interrater agreement between clinical and reading center gradings was not as great as inter-clinician agreement.
CONCLUSIONS: Interrater agreements were in the moderate to substantial range for the clinical assessment of lens opacities. Inherent differences in cataract classification systems that rely on slit lamp vs photographic assessments of lens opacities may explain some of the disagreement noted between slit lamp and photographic gradings. Given the interrater reliability statistics for clinicians and the simplicity of the grading procedure, ARLNS is presented for use in studies requiring a simple, inexpensive method for detecting the presence and severity of the major types of lens opacities.
FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.
PMID: 20561686 [PubMed - indexed for MEDLINE]
Digital versus film Fundus photography for research grading of diabetic retinopathy severity.
Invest Ophthalmol Vis Sci. 2010 Nov;51(11):5846-52
Authors: Li HK, Hubbard LD, Danis RP, Esquivel A, Florez-Arango JF, Ferrier NJ, Krupinski EA
PURPOSE: To assess agreement between digital and film photography for research classification of diabetic retinopathy severity.
METHODS: Digital and film photographs from a 152-eye cohort with a full spectrum of Early Treatment Diabetic Retinopathy Study (ETDRS) severity levels were assessed for repeatability of grading within each image medium and for agreement on ETDRS discrete severity levels, ascending severity thresholds, and presence or absence of diabetic retinopathy index lesions, between digital and 35-mm slides (film). Digital photographs were color balanced to match film.
RESULTS: There was substantial agreement (κ = 0.61, κ(w) [linear weighted] = 0.87) in classification of ETDRS diabetic retinopathy severity levels between digital images and film. Marginal homogeneity analyses found no significant difference in frequency distributions on the severity scale (P = 0.21, Bhapkar test). The κ results ranged from 0.72 to 0.95 for presence or absence of eight ascending diabetic retinopathy severity thresholds. Repeatability of grading between readers viewing digital images was equal to or better than that obtained with film (pair-wise interreader κ for digital images ranged from 0.47 to 0.57 and for film from 0.43 to 0.57. The κ results for identifying diabetic retinopathy lesions ranged from moderate to almost perfect. Moderate agreement of intraretinal microvascular abnormalities and venous beading between digital images and film accounted for slightly lower concordance for severity thresholds ≥47 and for slightly lower interreader agreement within digital and film images at severity thresholds ≥43 and ≥47.
CONCLUSIONS: Under controlled circumstances, digital photography can equal the reliability of 35-mm slides for research classification of ETDRS severity level.
PMID: 20484593 [PubMed - indexed for MEDLINE]
Monoscopic versus stereoscopic retinal photography for grading diabetic retinopathy severity.
Invest Ophthalmol Vis Sci. 2010 Jun;51(6):3184-92
Authors: Li HK, Hubbard LD, Danis RP, Esquivel A, Florez-Arango JF, Krupinski EA
PURPOSE: To assess agreement between monoscopic and stereoscopic photography for research classification of the severity of diabetic retinopathy (DR).
METHODS: Monoscopic digital (MD) images were compared with stereo digital (SD) and film (SF) photographs from a 152-eye cohort with full-spectrum Early Treatment Diabetic Retinopathy Study (ETDRS) severity levels for agreement on severity level, DR presence with ascending severity threshold, presence of DR index lesions, and repeatability of grading.
RESULTS: There was substantial agreement classifying ETDRS DR severity levels between MD and SF (kappa = 0.65, kappa(w) [linear weighted] = 0.87), MD and SD (kappa = 0.66, kappa(w) = 0.87), and SD and SF (kappa = 0.62, kappa(w) = 0.86) images. Marginal homogeneity analyses found no significant difference between MD and SF images (P = 0.53, Bhapkar test). The kappa agreement between MD and SF ranged from 0.80 to 0.94 for the presence or absence of eight ascending DR severity thresholds. Repeatability between the readers of the MD images was equal to or better than that of the readers of SD or SF images. Severity threshold grading repeatability between readers was similar with the MD and SF images. The kappa agreement between MD and SF for identifying diabetic retinopathy lesions ranged from moderate to almost perfect. The kappa comparisons showed that performance of grading new vessels on the disc in MD images was slightly lower than that with the SF images.
CONCLUSIONS: Monoscopic photography can equal the reliability of stereo photography for full ETDRS DR severity scale grading.
PMID: 20053978 [PubMed - indexed for MEDLINE]
Grading diabetic retinopathy severity from compressed digital retinal images compared with uncompressed images and film.
Retina. 2010 Nov-Dec;30(10):1651-61
Authors: Li HK, Florez-Arango JF, Hubbard LD, Esquivel A, Danis RP, Krupinski EA
PURPOSE: To compare research grading of diabetic retinopathy (DR) severity level from compressed digital images versus uncompressed images and film.
METHODS: Compressed (JPEG2000, 37:1) digital images (C) were compared with uncompressed digital (U) and film (F) stereoscopic photographs from a 152-eye cohort with full-spectrum Early Treatment Diabetic Retinopathy Study severity levels for agreement on severity level, DR presence with ascending severity threshold, presence of DR index lesions, and repeatability of grading.
RESULTS: Classification of Early Treatment Diabetic Retinopathy Study severity levels from C images agreed substantially with results from F images (κ = 0.60, κ(w) [linear weighted] = 0.86) and uncompressed digital images (κ = 0.76, κ(w) = 0.92). For agreement of uncompressed digital versus F images, κ = 0.62 and κ(w) = 0.86. Distribution of Early Treatment Diabetic Retinopathy Study levels was not significantly different between C and F images (P = 0.09, Bhapkar's test for marginal homogeneity). For presence/absence of DR at 8 ascending severity thresholds, agreement between C and F was "almost perfect" (κ ≥ 0.8). Agreement on severity level between readers with C images was at least as good as that with uncompressed digital image or F. Repeatability of severity threshold grading between readers was similar using C or F images. For identifying individual DR lesions, agreement between C and F ranged from "moderate" to "perfect." Agreement of grading venous beading from C was slightly lower than from F.
CONCLUSION: Full Early Treatment Diabetic Retinopathy Study scale DR severity level grading using C images is comparable to that using U images or film.
PMID: 20921928 [PubMed - indexed for MEDLINE]