Digital Fundus Photography Research Articles

Chorioretinal scar growth after 810-nanometer laser treatment for retinoblastoma

Purpose To determine the extent of expansion of laser scars after single treatment with transpupillary thermotherapy (TTT) for retinoblastoma. Design We retrospectively reviewed medical records and RetCam (Massie Industries, Dublin, CA) digital fundus photographs of patients with retinoblastoma who received TTT by use of an 810-nm diode laser with large-spot indirect ophthalmoscope. Digital images were measured by use of RetCam software beginning immediately after treatment. Lesions were measured in both linear size and area by 2 observers. In addition, optic disc diameters were also measured for each image. Participants We identified 9 patients with hereditary retinoblastoma who were treated from 1997 to 2000. Main outcome measures Linear and area expansion of laser scars as a function of time. Results Fourteen tumors in 10 eyes were treated successfully with 1 session of TTT. Follow-up for all eyes was at least 16 months. Scars of 12 of the 14 lesions increased beyond their original borders (mean starting linear diameter, 2.02 mm; range 1.46–2.59 mm; mean increase, 0.72 mm [36%]) over time, most within 6 months to 1 year after treatment. Conclusions Scars from TTT for retinoblastoma may increase in size after treatment. This expansion must be considered when applying TTT to tumors near vital macular structures, such as the fovea and optic nerve.

Five to 15 year follow-up of resolved idiopathic central serous chorioretinopathy.

To recognize the long-term sequelae of resolved idiopathic central serous chorioretinopathy (ICSC) in relation to visual acuity, contrast sensitivity, and lesion size between time elapsed since disease onset. Patients were recruited from fluorescein angiogram records between January 1985 and December 1995 with confirmed ICSC. Visual acuity, contrast sensitivity, and digital fundus photographs were recorded on follow-up. Comparison with the initial red-free photographs were made. There was no statistically significant deterioration of visual acuity over time compared to eyes with ICSC after initial resolution and the normal eyes. The change of lesion size over time was also statistically insignificant. Contrast sensitivity compared to visual acuity showed positive correlation in both ICSC and normal eyes, but the results were statistically insignificant. Lesion size correlates negatively with visual acuity and contrast sensitivity although this was statistically insignificant. This study shows little, if any, correlation between time and progression of retinal pigment epitheliopathy following resolution of ICSC. Visual acuity did not seem to worsen over time. Our data were not statistically significant, but it does give insight into the natural history of what is still a relatively poorly understood disease.

Retinal vascular changes and 20-year incidence of lower extremity amputations in a cohort with diabetes

Objective: To examine the association of retinal vascular changes with the incidence of lower extremity amputations (LEAs) in a cohort with diabetes mellitus. Methods: Baseline examinations were performed in a cohortof996personswithdiabetesdiagnosedbeforethe age of 30 years and using insulin. History of LEAwas obtained at baseline and at 4, 10, 14, and 20 years. The cumulative 20-year incidence of first LEA was calculated by the product-limit method in 906 persons with follow-up information. Retinal arterioles and venules were measured on digitized fundus photographs obtained at baseline by a standard protocol. Generalized arteriolar narrowingwasdefinedasthelowest25%ofthearteriolevenuleratio.Measurementswereobtainedinatleastone eye for 820 persons. Focal arteriolar narrowing and arteriovenous nicking were also determined from fundus photographs by a standard protocol. Results:The 20-year cumulative incidence of LEAs was 9.9%.TheunadjustedriskofundergoingaLEAwashigher in persons with generalized arteriolar narrowing than in those without it (15.7% vs 5.7%; odds ratio [OR], 3.08; 95% confidence interval [CI], 1.60-4.68), and in personswithfocalnarrowing(33.1%vs6.8%;OR,5.59;95% CI,3.27-9.54).Theresultsforarteriovenousnickingwere not significant. With control for age, sex, levels of glycosylated hemoglobin, diastolic blood pressure, and history of ulcers of the feet, the relationships were attenuated but still statistically significant for both generalized narrowing (OR, 1.89; 95% CI, 1.06-3.35) and focal narrowing (OR, 3.56; 95% CI, 1.87-6.78).

Efficacy and reliability of fundus digital camera as a screening tool for diabetic retinopathy in Kuwait

Objective: Many screening and follow-up methods are available for detecting diabetic retinopathy (DR). However, once patients develop retinopathy, it is unclear as to what method should be used for their review. This study is designed to assess the correlation between fundus digital image and clinical examination and to develop a screening program for the early detection of sight-threatening DR using a Canon CF 60 UV fundus camera. Methods: Patients who were not treated for DR earlier were enrolled in the study. All patients underwent digital fundus photography. The photographs were evaluated and compared with the clinical findings as recorded by retinal specialists. DR and macular edema were analyzed separately, and the correlation was statistically measured. The kappa statistic was used to estimate the extent of the agreement between the two procedures. Results: A total of 92 eyes of 51 patients were eligible to be entered in the study. Comparison of the digital image of the fundus and the examination by an ophthalmologist showed a good correlation. The kappa score for retinopathy was estimated to be 93% with 95.6% concordance. The kappa score for diabetic maculopathy was 88% with concordance of 92.2%. Conclusion: We conclude that digital images provide an efficient method for diagnosing and classifying sight-threatening DR, particularly proliferative diabetic retinopathy (PDR). However, agreement between the digital fundus camera and clinical examination by an ophthalmologist for diabetic maculopathy detection, though substantial statistically, was not very satisfactory. It was also felt that the digital photographs can be used as a tool for teleophthalmology and can be integrated as a screening system in Kuwait.

Kinetics of retinal lipoprotein precipitation and elimination after closure of subretinal new vessels.

To study the kinetics of retinal precipitation and elimination of lipoprotein in relation to photodynamic therapy of subretinal new vessels. This was a retrospective observational study of subretinal precipitate before and after photodynamic therapy for subfoveal new vessels secondary to age-related macular degeneration in 14 eyes demonstrating precipitate at one or more visits, using digital red-free gray-scale fundus photography, intravenous fluorescein angiography, optical coherence tomography, and morphometric mapping. In 14 eyes of 14 patients, the area covered by lipoprotein precipitate increased from a mean of 0.54 optic disc areas (range, 0-2.61) before treatment to a mean of 0.65 optic disc areas (range, 0.01-3.04) at 45 d after treatment (P = 0.18). Eyes with a serous detachment at baseline, before the initial treatment (n = 10) demonstrated more treatment-related precipitation than eyes without a serous detachment at baseline (n = 4; P = 0.034). Two eyes with a large amount of precipitate and a long follow-up demonstrated net elimination of precipitate from approximately 100 days after the initial treatment, with uniexponential precipitate half-lives of 43 and 32 days. Photodynamic therapy for subfoveal new vessels may be associated with retinal precipitation of lipoprotein, presumably because early extraction of water and salts from the subretinal fluid increases the concentration of leaked plasma proteins. Despite reperfusion of the subretinal vessels, macromolecular leakage appears to cease within 100 days, indicating that functional maturation of the new vessels has occurred, with an associated decrease in pore size.

Photography or Ophthalmoscopy for Detection of Diabetic Retinopathy?

The U.K. National Screening Committee recommended digital fundus photography as the screening method of choice for diabetic retinopathy (DR). However, concerns have been expressed about replacing ophthalmoscopy with slit-lamp biomicroscopy by digital photography. These concerns included the possibility of missing peripheral and stereoscopic visible retinal lesions; increased chance of a technical failure compared with ophthalmoscopy, resulting in more reexaminations; and higher cost (1). New data from our study of 453 patients with diabetes, aged 31–86 years, highlight the need for a careful consideration of the retinal area photographed and the minimal resolution of …

The sensitivity and specificity of single-field nonmydriatic monochromatic digital fundus photography with remote image interpretation for diabetic retinopathy screening: a comparison with ophthalmoscopy and standardized mydriatic color photography

PURPOSE: To evaluate single-field digital monochromatic nonmydriatic fundus photography as an adjunct in the screening of diabetic retinopathy. DESIGN: Prospective, comparative, observational case series. METHODS: Patients with type I and type II diabetes mellitus (n = 197) were sequentially evaluated by three different techniques: single-field digital monochromatic nonmydriatic photography; dilated ophthalmoscopy by an ophthalmologist; and seven Early Treatment Diabetic Retinopathy Study (ETDRS) standardized 35-mm color stereoscopic mydriatic images. The seven stereoscopic color photographs served as the reference standard and were compared with either ophthalmoscopy or a single digital photograph transmitted electronically to a reading site. Levels of agreement were determined by κ analyses. The sensitivity and specificity of the three methods were compared based on a threshold for referral to further ophthalmologic evaluation (ETDRS level ≥35). RESULTS: There was highly significant agreement (κ = 0.97, P = .0001) between the degree of retinopathy detected by a single nonmydriatic monochromatic digital photograph and that seen in seven standard 35-mm color stereoscopic mydriatic fields. The sensitivity of digital photography compared with color photography was 78%, with a specificity of 86%. Agreement was poor (κ = 0.40, P = .0001) between mydriatic ophthalmoscopy and the seven-field standard 35-mm color photographs. Sensitivity of ophthalmoscopy compared with color photography was 34%, with a specificity of 100%. CONCLUSION: A single nonmydriatic monochromatic wide-field digital photograph of the disk and macula was more sensitive for diabetic retinopathy screening than mydriatic ophthalmoscopy, the currently accepted screening method. When adjudicated by standard seven-field color photographs, the higher sensitivity of digital photography primarily reflected the reduced sensitivity of ophthalmoscopy in detecting early retinopathy.

High-resolution stereoscopic digital fundus photography versus contact lens biomicroscopy for the detection of clinically significant macular edema

Purpose The purpose of this study was to compare high-resolution stereoscopic digital photography to contact lens biomicroscopy (CLBM) for the diagnosis of clinically significant macular edema. Study design Comparative, prospective, observational case series. Participants One hundred twenty diabetic patients. Methods Patients underwent clinical retinal examination with CLBM by a retinal specialist. On the same day as clinical grading, patients received high-resolution stereoscopic digital imaging of the macula. The stereoscopic digital images were viewed using liquid crystal shutter goggles at least 2 months after clinical examination by a single masked grader for the presence or absence of diabetic retinopathy. Main outcome measures Presence or absence of the Early Treatment of Diabetic Retinopathy Study criteria for clinically significant macular edema (CSME) overall, CSME 1, CSME 2, CSME 3, macular edema, microaneurysms, intraretinal hemorrhage, and hard exudate. Results Two hundred seven eyes of 105 patients had complete data sets from both diagnostic modalities. Exact agreement was high for all identified pathologic conditions: CSME overall, 83.6%; CSME 1, 83.6%; CSME 2, 96.1%; CSME 3, 88.5%; macular edema, 75.0%; microaneurysms, 77.9%; intraretinal hemorrhage, 83.7%; and hard exudate, 73.1%. Sensitivity ranged from 50.0% (CSME 2) to 90.6% (CSME overall). Specificity ranged from 90.0% (macular edema) to 99.0% (CSME 2). Conclusions High-resolution stereoscopic digital photography is both sensitive and specific when identifying CSME and correlates well with the accepted standard of CLBM for the diagnosis of CSME.

Clinical Investigation of a True Color Scanning Laser Ophthalmoscope

To show true color scanning laser ophthalmoscope (SLO) images produced by simultaneously imaging the retina with red, green, and blue lasers. Low-power red, green, and blue lasers were combined using fiber optics. By rapidly pulsing the lasers, each point on the fundus is illuminated by the 3 colors in quick succession, with the total power level being similar to that from a single laser. The reflected light is then decoded to extract the red, green, and blue color information and the true color fundus image is displayed live on a computer monitor. Comparison was made between the color SLO images from 5 patients and their digitized fundus photographs. The background fundus and retinal vasculature showed a similar appearance. The SLO gave better quality information in patients with ocular histoplasmosis, macular dystrophy, and optic disc drusen. By operating the color SLO in the indirect mode, macular edema could be clearly seen as lines and ridges surrounding the fovea. The color SLO offers all the advantages of the present commercially available monochromatic device, with the added advantage of true color representation of the fundus without increasing either imaging time or the level of exposure.

Automated detection of microaneurysms in digital red‐free photographs: a diabetic retinopathy screening tool

To develop a technique to detect microaneurysms automatically in 50 degrees digital red-free fundus photographs and evaluate its performance as a tool for screening diabetic patients for retinopathy. Candidate microaneurysms are extracted, after the image has been modified to remove variations in background intensity, by algorithms that enhance small round features. Each microaneurysm candidate is then classified according to its intensity and size by the application of a set of rules derived from a training set of 102 images. When 3,783 individual images were analysed and the results compared with the opinion of a clinical research fellow examining the same images, the program achieved a sensitivity of 81% and a specificity of 93% for the detection of images containing microaneurysms. Nine hundred and twenty-five sets of 4 images per patient were then analysed and the total number of microaneurysms detected compared with the overall patient retinopathy grade derived by the clinician examining the same images. In this context, intended to mimic a screening situation, the program achieved a sensitivity of 85% and a specificity of 76% for the detection of patients with (any) retinopathy (positive predictive value 0.71, negative predictive value 0.88). An automated technique was developed to detect retinopathy in digital red-free fundus images that can form part of a diabetic retinopathy screening programme. It is believed that it can perform a useful role in this context identifying images worthy of closer inspection or eliminating 50% or more of the screening population who have no retinopathy.

A telemedical approach to the screening of diabetic retinopathy: digital fundus photography.

The importance of screening for diabetic retinopathy has been established, but the best method for screening has not yet been determined. We report on a trial of assessment of digital photographs by telemedicine compared with standard retinal photographs of the same fields and clinical examination by ophthalmologists. A total of 129 diabetic inpatients were screened for diabetic retinopathy by slit-lamp biomicroscopy performed by an ophthalmologist and by two-field 50 degrees non-stereo digital fundus photographs assessed by six screening centers that received the images by electronic mail. Conventional 35-mm transparencies of the same fields as the digital photographs were assessed by a retinal specialist and served as the reference method for detection of diabetic retinopathy. Slit-lamp biomicroscopy was the reference method for the detection of macular edema. The prevalence of any form of diabetic retinopathy was 30% (n = 35); of sight-threatening retinopathy including macular edema, the prevalence was 6% (n = 7). The assessment of digital images by the six screening centers resulted in a median sensitivity of 85% and a median specificity of 90% for the detection of moderate nonproliferative or sight-threatening diabetic retinopathy. Clinically significant macular edema (n = 4) was correctly identified in 15 of the 24 grading reports. An additional seven reports referred the patients for further investigation because of concurrent diabetic retinopathy. Telescreening for diabetic retinopathy by an assessment of two-field 50 degrees non-stereo digital images is a valid screening method. Although detection of clinically significant macular edema using biomicroscopy is superior to digital or standard non-stereo photographs, only few patients with sight-threatening diabetic retinopathy are missed.

Retinal blood vessel width measured on color fundus photographs by image analysis.

The purpose of this paper was to develop a technique using computerized image analysis to measure the width of retinal arteries and veins on color fundus photographs. The width of the retinal vessel was determined from digitized fundus photographs by programs based on edge detection and boundary tracing. The average vessel width was determined at different distances or eccentricities from the center of the optic disc and using various lengths of vessel segment. Measurements of superior and inferior temporal vessel width for 20 eyes by 2 operators showed that about 75% of the measurements could be obtained without the use of plan points. The average percent coefficient of variation of the measurements was 2.17% for 3 measurements of each vessel. This technique provides a reproducible and objective method for obtaining the following parameters: the edges of the vessel, the length of the vessel segment to be measured, location of the measurement along the vessel and subsequent retinal vessel width. This technique is readily suitable for application to clinical studies particularly clinical trials.

Fundus pigmentation and the electroretinographic luminance-response function

Dark-adapted and light-adapted electroretinographic luminance-response functions were recorded from subjects with light or dark fundus pigmentation based on digitized fundus photographs. For dark- and light-adapted electroretinograms, subjects with dark fundi had smaller b-wave amplitudes at all luminance levels. There was no significant difference in b-wave implicit time for the dark-adapted electroretinogram, but there was a significant difference for the light-adapted ERG between the two groups. The results suggest that fundus pigmentation should be considered in the interpretation of electroretinogram results. A possible mechanism for the influence of fundus pigmentation on b-wave amplitude is based on increased resistance associated with melanin.

Fundus pigmentation and the dark-adapted electroretinogram.

Dark-adapted electroretinograms were obtained over a 3.6-log range of stimulus intensities from 17 black and 15 white normal subjects. Subjects were grouped on the basis of light or dark fundus pigmentation, determined from digitized fundus photographs. B-wave amplitudes for each group were fitted by the Naka-Rushton equation, and the measures Vmax, log K, and n were determined. The luminance-response functions revealed that subjects with light fundi had larger b-wave amplitudes at all luminance levels. There was a significant difference between groups for Vmax and n but not for log K. A comparison of b-wave implicit times showed no significant difference between subjects with dark and light fundi. Ancillary tests and multiple regression analysis suggested that the relationship between Vmax and fundus pigmentation could not be attributed to age, gender, refractive error, axial length or intraocular pressure. The results have implications for the collection of normative electroretinographic data and for the interpretation of electroretinogram results.

Computer measurement of retinal nerve fiber layer striations

An image analysis method to measure retinal nerve fiber layer (RNFL) striations from digitized fundus photographs was developed to improve detection and monitoring of progressive diffuse RNFL loss. Striations were measured by comparing the high spatial frequency variability across with the variability along the RNFL. This locally normalized measure of striations compensates for the wide density variations both within individuals and between individuals and RNFL photographs. Five repeated measurements were taken at each of three locations from each retinal image. Measurements from five patients with recorded visual field loss due to optic nerve diseases were compared with five normal subjects and five suspect eyes. Measurements clearly distinguished the three groups when taken at the temporal arcades. Measurements above and below the arcades were also consistent, but did not distinguish normals from suspects. The measure was correlated with graded estimates of RNFL integrity of two trained observers (rho = -0.57, p < 0.001 and rho = -0.61, p < 0.001).