Single-field fundus photography for diabetic retinopathy screening: a report by the American Academy of Ophthalmology

Development of a mobile phone based ophthalmoscope for telemedicine

Regular retinal examinations can contribute to the management of both hypertensive and diabetic retinopathy. One of the most successful means of evaluating these retinopathies is by means of a fundus camera generating a fundus photograph. Patients in rural clinics unfortunately often lack the financial means to undergo regular examinations. This study produced a handheld ophthalmoscope that combines with a digital camera to capture retinal images. The images are transferred to a mobile phone and then sent to a central website for evaluation. The evaluation report is automatically returned to the mobile phone via SMS. The quality of the images was rated as acceptable for clinical use by medical specialists at the Department of Ophthalmology of the Health Sciences Faculty of Stellenbosch University, South Africa.

Retinopathy and visual impairment in diabetes, impaired glucose tolerance and normal glucose tolerance: the Nord-Trøndelag Health Study (the HUNT study)

PURPOSE

The aim of the study was to describe the prevalence of visual impairment and retinopathy and to investigate risk factors for retinopathy in persons with diabetes, screen-detected diabetes, impaired glucose tolerance and normal glucose tolerance in a subpopulation of the HUNT study.

METHODS

We used a sample (n = 163) from a population-based screening survey of hyperglycaemia, undertaken in 2004-2005 in Verdal, Norway. Baseline information was accessible through the second Nord-Trøndelag Health Study (HUNT2), 1995-97. Data collection was made in 2005 and included patient history, refraction, visual acuity, cataract assessment and single-field, nonmydriatic retinal photography. Retinal photographs were graded independently by two graders blinded to patient information. Data were analysed with standard statistical methods, and p < 0.05 was considered significant.

RESULTS

In all, 126 (77%) persons participated, 55% were women. The mean (SD) age was 59 (± 14) years. Four (3%) had correctable visual impairment, and none were visually impaired. Retinal photographs were gradable for both eyes in 109 (87%) participants. The prevalence of retinopathy was 11% in persons with known diabetes, 4% in persons with screen-detected diabetes, 3% in persons with impaired glucose tolerance and 10% in persons with normal glucose tolerance. Retinopathy was not associated with known history of diabetes or current glycaemic status. Nonfasting plasma glucose (in 1995-97) was an independent risk factor for retinopathy (in 2005), OR (95% CI) 1.5 (1.01, 2.13), p = 0.046.

CONCLUSION

The prevalence of diabetic retinopathy in persons with diabetes in this study was low. Appropriate optical correction and regular eye examination can prevent unnecessary visual impairment in both persons with and without diabetes.

Screening for diabetic retinopathy: review of current methods

OBJECTIVE

To review the current screening methods for diabetic retinopathy, with a focus on nonmydriatic digital fundus photography.

METHODS

Articles from Medline were reviewed from 1976 to November 2011 for different combinations of the words "diabetic retinopathy," "screening," "fundus photography," and "nonmydriasis."

RESULTS

Because of its ease of use and cost-effectiveness, digital fundus photography is becoming the preferred method for diagnosing diabetic retinopathy. Current research has proven that pupillary dilation is not a necessary step in the fundus examination, although it reduces the number of unnecessary referrals to ophthalmologists. Automated grading systems, while saving time and reducing human error, still need refinement before they can replace manual grading by trained ophthalmologists.

CONCLUSION

Nonmydriatic digital fundus photography with manual grading by a trained technician is an acceptable method of screening for diabetic retinopathy.

Non-mydriatic single-field fundus photography for the screening of retinal diseases in an executive health clinic

BACKGROUND AND OBJECTIVE

To determine the accuracy and sensitivity of a single-field non-mydriatic digital fundus image interpreted by an ophthalmologist and performed within a primary care setting.

PATIENTS AND METHODS

Fundus photography using a digital non-mydriatic camera was performed on both eyes of 1,175 consecutive patients as part of an executive health program. All fundus images included a 45° field of the posterior pole capturing the optic nerve and macular area. Diagnostic findings were recorded and appropriate recommendations for follow-up were made. Patients were then contacted to see whether appropriate follow-up was successfully completed and chart reviews were performed to determine biomicroscopic findings.

RESULTS

Photographs were adequate in both eyes in 1,117 patients (95.1%). Examination findings were normal in both eyes in 951 (85.1%) patients. Abnormal findings were noted in either eye in 166 (14.9%) patients. The most common abnormal findings were macular degeneration (57/166, 34.3%), optic nerve cupping (45/166, 27.1%), hypertensive retinopathy (15/166, 9.0%), and choroidal nevi (10/166, 6.0%). In all patients with abnormal findings, routine follow-up ophthalmologic examination with an eye care specialist was indicated and none of the patients required urgent attention. Sensitivity was found to be 87% and stratification was performed based on the initial diagnosis. False-positive results were from confounding diagnoses rather than true false-positives.

CONCLUSION

Single-field non-mydriatic fundus photography is accurate and sensitive for screening retinal disease in a primary care setting.

Challenges to establishing nationwide diabetic retinopathy screening programs

PURPOSE OF REVIEW

To review the results of recently published studies on diabetic retinopathy screening.

RECENT FINDINGS

Despite numerous public health campaigns and the existence of guidelines designed to promote annual retinal exams for diabetes patients, an unacceptably high number of patients are not screened for diabetic retinopathy. Current findings suggest the need for novel methods to improve compliance with retinal screening exams among diabetes patients to preserve vision functionality in this population.

SUMMARY

Diabetic retinopathy represents a major cause of acquired vision loss. The following review addresses the factors that contribute to inadequate retinopathy screenings among diabetes patients and proposes solutions that have the potential to increase the quality and accessibility of screening programs for diabetes patients.

Diabetic retinopathy screening using tele-ophthalmology in a primary care setting

We evaluated tele-ophthalmology for diabetic retinopathy screening in a primary care setting. Four general practitioners (GPs) were taught to assess non-mydriatic retinography images of patients with diabetes. After training, a total of 1223 patients were screened using this method: 926 (76%) did not have diabetic retinopathy and 297 (24%) were referred for an ophthalmologic assessment. Of the 297 patients, 186 (15%) did not have diabetic retinopathy and were considered to be false positives, 85 (7%) had diabetic retinopathy and in 26 cases (2%) the retinography images were unreadable. The specificity of GPs for detecting diabetic retinopathy by non-mydriatic retinography was 83%. Ophthalmologists also assessed 120 patients who had been diagnosed as normal to detect false negatives. Ten patients (8.3%) had mild non-proliferative diabetic retinopathy with small isolated retinal hemorrhages. Only one patient (0.8%) had treatable diabetic retinopathy with hard exudates and microaneurysms. The sensitivity of GPs for detecting diabetic retinopathy was 90.9%; the sensitivity for detecting treatable lesions was 99.2%. We concluded that adequately trained GPs can screen for treatable lesions of diabetic retinopathy with a very high level of reliability using non-mydriatic retinography.

Diabetic retinopathy

Diabetic retinopathy is a common and specific microvascular complication of diabetes, and remains the leading cause of preventable blindness in working-aged people. It is identified in a third of people with diabetes and associated with increased risk of life-threatening systemic vascular complications, including stroke, coronary heart disease, and heart failure. Optimum control of blood glucose, blood pressure, and possibly blood lipids remains the foundation for reduction of risk of retinopathy development and progression. Timely laser therapy is effective for preservation of sight in proliferative retinopathy and macular oedema, but its ability to reverse visual loss is poor. Vitrectomy surgery might occasionally be needed for advanced retinopathy. New therapies, such as intraocular injection of steroids and antivascular endothelial growth-factor agents, are less destructive to the retina than are older therapies, and could be useful in patients who respond poorly to conventional therapy. The outlook for future treatment modalities, such as inhibition of other angiogenic factors, regenerative therapy, and topical therapy, is promising.

Automated detection of diabetic retinopathy: barriers to translation into clinical practice

Automated identification of diabetic retinopathy (DR), the primary cause of blindness and visual loss for those aged 18-65 years, from color images of the retina has enormous potential to increase the quality, cost-effectiveness and accessibility of preventative care for people with diabetes. Through advanced image analysis techniques, retinal images are analyzed for abnormalities that define and correlate with the severity of DR. Translating automated DR detection into clinical practice will require surmounting scientific and nonscientific barriers. Scientific concerns, such as DR detection limits compared with human experts, can be studied and measured. Ethical, legal and political issues can be addressed, but are difficult or impossible to measure. The primary objective of this review is to survey the methods, potential benefits and limitations of automated detection in order to better manage translation into clinical practice, based on extensive experience with the systems we have developed.

Microaneurysm number and distribution in the macula of Chinese type 2 diabetics with early diabetic retinopathy: a population-based study in Kinmen, Taiwan

To explore the number and distribution of microaneurysms (MA) in the macula of type 2 diabetics in Kinmen, Taiwan and associated risks for early diabetic retinopathy (DR). A baseline mass screening extracts 971 type 2 diabetics between 1991 and 1993 and follow-up eye screening at 1999 was then done. Number of MA was counted and associated systemic factors collected from a centered 45 degrees color fundus photograph of dilated eyes of type 2 diabetics (Topcon-NW5). Thirty-three (6.2%, n = 527) had MA retinopathy. Those with one eye involved (n = 26) had two mean MA; those with bilateral involvement (n = 7) had four mean per eye. Most MA were located temporally (mean MA = 0.79), then superiorly (mean = 0.58), inferiorly (mean = 0.46) and nasal (mean = 0.28). MA occurred at the 6,000-microm outermost ring (mean = 1.51), then the 3,000-microm ring (mean = 0.35), the 1,500-microm ring (mean = 0.26) and center 500 microm circle (mean = 0.01). After adjusting for confounding factors, early DR with MA was associated with longer duration of type 2 diabetes [odds ratios (OR) = 1.10, 95% confidence interval (CI) 1.00-1.21], higher glycosylated hemoglobin (OR = 1.36, 95%CI 1.11-1.66) and wider waist circumference (OR = 1.04, 95%CI 1.01-1.07). Our photograph grading system suggests that MA number and distribution at the macula may reflect severity of early DR and is a valid tool for predicting the progression of DR. Identifying those factors associated with MA only DR is important in developing prevention strategies for this early microvascular complication of type 2 diabetes.

Photoacoustic ophthalmoscopy for in vivo retinal imaging

We have developed a non-invasive photoacoustic ophthalmoscopy (PAOM) for in vivo retinal imaging. PAOM detects the photoacoustic signal induced by pulsed laser light shined onto the retina. By using a stationary ultrasonic transducer in contact with the eyelids and scanning only the laser light across the retina, PAOM provides volumetric imaging of the retinal micro-vasculature and retinal pigment epithelium at a high speed. For B-scan frames containing 256 A-lines, the current PAOM has a frame rate of 93 Hz, which is comparable with state-of-the-art commercial spectral-domain optical coherence tomography (SD-OCT). By integrating PAOM with SD-OCT, we further achieved OCT-guided PAOM, which can provide multi-modal retinal imaging simultaneously. The capabilities of this novel technology were demonstrated by imaging both the microanatomy and microvasculature of the rat retina in vivo.

Retinal imaging and image analysis

Many important eye diseases as well as systemic diseases manifest themselves in the retina. While a number of other anatomical structures contribute to the process of vision, this review focuses on retinal imaging and image analysis. Following a brief overview of the most prevalent causes of blindness in the industrialized world that includes age-related macular degeneration, diabetic retinopathy, and glaucoma, the review is devoted to retinal imaging and image analysis methods and their clinical implications. Methods for 2-D fundus imaging and techniques for 3-D optical coherence tomography (OCT) imaging are reviewed. Special attention is given to quantitative techniques for analysis of fundus photographs with a focus on clinically relevant assessment of retinal vasculature, identification of retinal lesions, assessment of optic nerve head (ONH) shape, building retinal atlases, and to automated methods for population screening for retinal diseases. A separate section is devoted to 3-D analysis of OCT images, describing methods for segmentation and analysis of retinal layers, retinal vasculature, and 2-D/3-D detection of symptomatic exudate-associated derangements, as well as to OCT-based analysis of ONH morphology and shape. Throughout the paper, aspects of image acquisition, image analysis, and clinical relevance are treated together considering their mutually interlinked relationships.

Screening for diabetic retinopathy: 1 and 3 nonmydriatic 45-degree digital fundus photographs vs 7 standard early treatment diabetic retinopathy study fields

PURPOSE

To evaluate if simple- or multiple-field digital color nonmydriatic (NM) retinal images can replace 7 standard stereoscopic fundus photographs in the screening of diabetic retinopathy (DR).

DESIGN

Prospective, masked, comparative case series.

METHODS

One hundred and eight eyes of 55 diabetics were studied to determine single lesions and to grade clinical levels of DR and diabetic macular edema (DME) using both 1 and 3 NM digital color retinal images compared with the Early Treatment Diabetic Retinopathy Study (ETDRS) 7 standard 35-mm stereoscopic color fundus photographs (7F-ETDRS). All eyes underwent NM 45-degree field images of 1 central field (1F-NM), NM 45-degree field images of 3 fields (3F-NM), and, after pupil dilatation, 30-degree 7F-ETDRS photography. Images were analyzed by 2 independent, masked retinal specialists (S.V. and E.B.), lesion-by-lesion according to the ETDRS protocol and for clinical severity level of DR and DME according to the international classification of DR.

RESULTS

Using 7F-ETDRS as the gold standard, agreement was substantial for grading clinical levels of DR and DME (kappa = 0.69 and kappa = 0.75) vs 3F-NM; moderate for DR level (kappa = 0.56) and substantial for DME (kappa = 0.66) vs 1F-NM; almost perfect for detecting presence or absence of DR (kappa = 0.88) vs both 1F-NM and 3F-NM; and almost perfect for presence or absence of DME (kappa = 0.97) vs 3F-NM and substantial (kappa = 0.75) vs 1F-NM. Sensitivity and specificity for detecting referable levels of DR were 82% and 92%, respectively, for 3F-NM and 71% and 96%, respectively, for 1F-NM.

CONCLUSIONS

Three color 45-degree NM fundus fields may be an effective tool in a screening setting to determine critical levels of DR and DME for prompt specialist referral. One central 45-degree image is sufficient to determine absence or presence of DR and DME, but not for grading it.

Prevalence and risk factors of diabetic retinopathy in a multi-racial underserved population

PURPOSE

To describe the prevalence, severity, and associated risk factors of diabetic retinopathy among different racial groups (whites, blacks, Hispanics, and Asians) within an urban, underserved population.

METHODS

2-field non-mydriatic retinal photographs of each eye were reviewed for 1073 patients referred to the San Francisco General Hospital mobile eye service, the Eye Van, for diabetic retinopathy screening. Presence and severity of diabetic retinopathy was determined based on a modification of the Airlie House classification system.

RESULTS

The prevalence of any retinopathy among all diabetics was 15.7%. There was no statistical difference in the prevalence of retinopathy among the racial groups. Significant independent predictors of presence and severity of retinopathy were longer duration of diabetes, and use of oral hypoglycemic medication or insulin (P < 0.05). Gender, age, primary language, income, and co-diagnosis of hypertension were not correlated.

CONCLUSIONS

In this population of similar socioeconomic status and access to healthcare, race was not an independent predictor of diabetic retinopathy. This suggests that racial differences described in previous studies may be eliminated when social factors are equalized.

Accuracy of primary care clinicians in screening for diabetic retinopathy using single-image retinal photography

PURPOSE

Diabetic patients with limited access to ophthalmologists have low screening rates for diabetic retinopathy. We evaluated a diabetic retinopathy screening program in a community health center using single images taken with a nonmydriatic retinal camera and primary care clinicians trained to read retinal images.

METHODS

This study was conducted from 2001 to 2004 in a multisite community health center staffed by family physicians, advanced practice nurses, and physician's assistants. The clinic serves a primarily low-income, Hispanic population. Clinic clinicians were trained to read the retinal photographs. All images were overread by an ophthalmologist. Patients were referred to eye care specialists for severe diabetic retinopathy, unknown or other abnormality, or inadequate photographs. We analyzed agreement between the clinicians and the ophthalmologist in recognizing diabetic retinopathy and in determining which patients needed referral. We also analyzed overall screening rates based on clinic access to the camera.

RESULTS

One thousand forty diabetic patients were screened for diabetic retinopathy at the health center. One hundred thirteen (10.9%) were found to have diabetic retinopathy, 46 severe enough to warrant referral to an ophthalmologist. The clinicians failed to refer 35 (10.2%) of the 344 patients the ophthalmologist believed needed referral. Most cases of missed referral were due to failure to recognize an inadequate photograph or for abnormalities other than diabetic retinopathy. Screening rates were better in the clinic with a permanent camera.

CONCLUSIONS

Primary care clinicians trained to read single images from a retinal camera have acceptable accuracy in screening for diabetic retinopathy. Further training may be necessary to recognize other common abnormalities.

Retinopathy of prematurity management using single-image vs multiple-image telemedicine examinations

PURPOSE

To compare performance of single-image vs multiple-image telemedicine examinations for retinopathy of prematurity (ROP) diagnosis.

DESIGN

Prospective comparative study.

METHODS

A total of 248 eyes from 67 consecutive infants underwent wide-angle retinal imaging by a trained neonatal nurse at 31 to 33 weeks and/or 35 to 37 weeks postmenstrual age (PMA) at a single academic institution. Data were uploaded to a web-based telemedicine system and interpreted by three masked retinal specialists. Diagnoses were provided based on single images, and subsequently on multiple images, from both eyes of each infant. Findings were compared to a reference standard of indirect ophthalmoscopy by a pediatric ophthalmologist. Primary outcome measures were recommended follow-up interval, presence of plus disease, presence of type-2 or worse ROP, and presence of visible peripheral ROP.

RESULTS

Among the three graders, mean sensitivity/specificity for detection of infants requiring follow-up in less than one week were 0.85/0.93 by single-image examination and 0.91/0.88 by multiple-image examination at 35 to 37 weeks PMA. Mean sensitivity/specificity for detection of infants with type-2 or worse ROP were 0.82/0.95 by single-image examination and 1.00/0.91 by multiple-image examination at 35 to 37 weeks PMA. Mean sensitivity/specificity for detection of plus disease were 1.00/0.86 by single-image examination and 1.00/0.87 by multiple-image examination at 35 to 37 weeks PMA. There were no statistically-significant intragrader differences between accuracy of single-image and multiple-image telemedicine examinations for detection of plus disease.

CONCLUSIONS

Single-image and multiple-image telemedicine examinations perform comparably for determination of recommended follow-up interval and detection of plus disease. This may have implications for development of screening protocols, particularly in areas with limited access to ophthalmic care.

Potential bias in ophthalmic pharmaceutical clinical trials

To make clinicians aware of potential sources of error in ophthalmic pharmaceutical clinical trials that can lead to erroneous interpretation of results, a critical review of the study design of various pharmaceutical ophthalmic clinical trials was completed. Discrepancies as a result of study shortcomings may explain observed differences between reported ophthalmic trial data and observed clinical results.

Low prevalence of retinopathy, but high prevalence of nephropathy among Maori with newly diagnosed diabetes-Te Wai o Rona: Diabetes Prevention Strategy

AIMS/HYPOTHESIS

To describe the prevalence of retinopathy and microalbuminuria at diagnosis of diabetes in a predominantly Maori study population.

METHODS

Biomedical assessment including photographic retinal examination was undertaken among 157 (68.9% of eligible) members of Maori families (3.3% non-Maori) diagnosed with diabetes during a community screening programme (n=5240) as part of a diabetes prevention strategy.

RESULTS

Mean HbA1c of those with newly diagnosed diabetes was 7.8+/-1.5% with 34.4% having an HbA1c >/=8.0%. Retinopathy was present in 3 (1.7%) subjects, cataracts in 3.2%, microalbuminuria in 29.6% and albuminuria in 7.7%. After adjusting for covariates, only smoking was a risk factor for microalbuminuria/proteinuria (current and former smokers: increased 3.81(1.32-11.0) and 3.67(1.30-10.4) fold, respectively).

CONCLUSIONS

The prevalence of retinopathy at diagnosis was lower than in previous studies, yet that of microalbuminuria/proteinuria remained high. The retinopathy data suggest that case detection for diabetes in the community may be improving, but that other strategies among those at risk of diabetes, including those promoting smoking cessation, will be needed to reduce the risk of renal disease among Maori with diabetes.

Evaluation of a system for automatic detection of diabetic retinopathy from color fundus photographs in a large population of patients with diabetes

OBJECTIVE

To evaluate the performance of a system for automated detection of diabetic retinopathy in digital retinal photographs, built from published algorithms, in a large, representative, screening population.

RESEARCH DESIGN AND METHODS

We conducted a retrospective analysis of 10,000 consecutive patient visits, specifically exams (four retinal photographs, two left and two right) from 5,692 unique patients from the EyeCheck diabetic retinopathy screening project imaged with three types of cameras at 10 centers. Inclusion criteria included no previous diagnosis of diabetic retinopathy, no previous visit to ophthalmologist for dilated eye exam, and both eyes photographed. One of three retinal specialists evaluated each exam as unacceptable quality, no referable retinopathy, or referable retinopathy. We then selected exams with sufficient image quality and determined presence or absence of referable retinopathy. Outcome measures included area under the receiver operating characteristic curve (number needed to miss one case [NNM]) and type of false negative.

RESULTS

Total area under the receiver operating characteristic curve was 0.84, and NNM was 80 at a sensitivity of 0.84 and a specificity of 0.64. At this point, 7,689 of 10,000 exams had sufficient image quality, 4,648 of 7,689 (60%) were true negatives, 59 of 7,689 (0.8%) were false negatives, 319 of 7,689 (4%) were true positives, and 2,581 of 7,689 (33%) were false positives. Twenty-seven percent of false negatives contained large hemorrhages and/or neovascularizations.

CONCLUSIONS

Automated detection of diabetic retinopathy using published algorithms cannot yet be recommended for clinical practice. However, performance is such that evaluation on validated, publicly available datasets should be pursued. If algorithms can be improved, such a system may in the future lead to improved prevention of blindness and vision loss in patients with diabetes.

Evaluation of retinal digital images by a general practitioner

Diabetes and systemic hypertension are among the most prevalent diseases in developed countries. Since both can produce retinal involvement, they often cause long waiting lists for ophthalmologist consultation. The inspection of digital eye fundus images by a general practitioner would help to divert only those cases with retinal involvement. To evaluate this possibility we studied the agreement between the assessment of digital fundus images made by a general practitioner and an ophthalmologist. A total of 776 fundus images of 194 patients were inspected by both observers looking for retinal lesions consistent with diabetic or hypertensive retinopathy. Contingency tables were made, and the agreement between both observers was assessed by using the kappa index. We found good agreement between the findings reported by the general practitioner and those reported by the ophthalmologist (kappa = 0.80 for patients with only diabetes, 1.00 for patients with only hypertension, and 0.79 for patients with both diseases). Our results suggest that the inspection of digital retinal images by a general practitioner could reduce the number of referred patients for specialist consultation.

[Screening diabetic retinopathy in Burgundy with an itinerant nonmydriatic camera]

INTRODUCTION

The aim of this study was to assess the suitability of screening diabetic retinopathy (DR) with an itinerant nonmydriatic camera.

METHODS

This program required collaboration between ophthalmologists and general practitioners. Three professional organizations gave their support: L'union Professionnelle des Médecins Libéraux de Bourgogne (UPMLB), le Fonds d'Aide à la Qualité des Soins de Ville (FAQSV), et la Fédération des Associations des Diabétiques de Bourgogne (FADB). The screening programm took place from November 2004 to June 2005 throughout the Burgundy region. General practitioners, health professionals (pharmacists, nurses), local media, and health insurance offices informed patients of the DR screening. An orthoptist took photographs with a nonmydriatic digital camera. Each patient had four fundus photographs without pupillary dilatation. Photographs were analyzed in the Department of Ophthalmology of Dijon's General Hospital.

RESULTS

In this study, 676 diabetic patients were screened. Among these patients, 58 had DR, exclusively nonproliferative retinopathies. Nine percent of the photographs were ungradable. The mean age of patients with DR was 65 years. The mean onset of diabetes was 18 years before the study. Insulin therapy was followed by 27 patients (46.6%). Hemoglobin A1c was known in 26 patients (44.8%), with a mean value of 8.14%. Nearly 60% of patients with DR did not have their recommended annual consultation. After screening, 84% of patients consulted an ophthalmologist.

CONCLUSION

Screening DR with an itinerant nonmydriatic camera can improve ophthalmologic follow-up of diabetics in rural areas. This screening program has continued in 2006 with an adapted vehicle.

Evaluating the use of a scanning laser-derived oedema index to grade diabetic retinopathy and maculopathy

PURPOSE

To evaluate the Heidelburg Retina Tomograph II (HRTII) retinal module as a tool for grading severity of retinopathy in a diabetic retinal screening and treatment service.

METHODS

Seventy-seven consecutive patients with type 2 diabetes underwent scanning laser tomography using the HRTII. Scan data were analysed using the proprietary macular module software and oedema indices calculated for each of nine topographic macular zones. Two consultant ophthalmologists, masked to the result of the HRTII scans, graded each subject for severity of retinopathy and presence of macular oedema. The oedema indices were analysed statistically to determine whether these correlated with severity of retinopathy and presence of macular oedema.

RESULTS

There is an increased oedema index in severe non-proliferative diabetic retinopathy in the outer temporal zone compared with lesser grades of diabetic retinopathy (P = 0.001). In patients with clinically detectable macular oedema, the oedema index from the 500-microm-diameter central zone was significantly higher than those without (P = 0.03).

CONCLUSION

The scanning laser-derived oedema index differentiated between moderate and severe non-proliferative diabetic retinopathy in this series and detected diabetic macular oedema. Further development of this technology may provide an important tool to supplement retinal photographic surveillance in eye clinics overwhelmed by an increasing prevalence of type 2 diabetes.

Improving diabetic retinopathy screening ratios using telemedicine-based digital retinal imaging technology: the Vine Hill study

OBJECTIVE

To evaluate the impact of a telemedicine, digital retinal imaging strategy on diabetic retinopathy screening rates in an inner-city primary care clinic.

RESEARCH DESIGN AND METHODS

This retrospective cohort study included all diabetic patients aged > or = 18 years (n = 495) seen at Vine Hill Community Clinic between 1 September 2003 and 31 August 2004. Patients were offered ophthalmology referral or digital screening. Patients choosing referral received the next available (within 3 months) appointment at the Vanderbilt Eye Clinic; patients choosing digital screening were screened during the visit.

RESULTS

Retinal screening was documented for 293 (59.2%) patients, a significant improvement compared with the 23% baseline rate. Of 293 patients screened, 92 (31.4%) were screened in ophthalmology, and 201 (68.6%) were digitally screened. Among the 201 digitally screened patients, 104 (51.7%) screened negative and were advised to rescreen in 1 year, 75 (37.3%) screened positive and were nonurgently referred to ophthalmology, and 22 (11.0%) screened positive for sight-threatening eye disease and were urgently referred for ophthalmological follow-up. Digital imaging technical failure rate was 0.5%. Referral status was associated with race/ethnicity (chi2 = 7.9, P < 0.02) with whites more likely to screen negative than non-whites (62.4 vs. 47.8%, respectively). Sight-threatening disease among non-whites (14.7%) was more than double that observed for whites (5.9%).

CONCLUSIONS

Digital imaging technology in the primary care visit can significantly improve screening rates over conventional methods, increase access to recommended diabetic eye care, and focus specialty care on medically indigent patients with greatest need.

Can we predict which patients are at risk of having an ungradeable digital image for screening for diabetic retinopathy?

PURPOSE

We aimed to determine the reasons for, and variables which predicted, ungradeable retinal photographs during screening patients for diabetic retinopathy.

MATERIALS AND METHODS

Age, duration of diabetes, visual acuity, and HbA1c were recorded. Following dark adaptation, a single 45 degrees nonmydriatic photograph was taken of each fundus. The pupils were then dilated and the photograph repeated. Using slit lamp biomicroscopy, lenticular changes (LOCS III), and fundus appearance were recorded.

RESULTS

In ungradeable photographs the fovea could not be visualised in 98% of cases of images from nonmydriatic photography, and in 88% if mydriasis was used. Poor definition in the nonmydriatic image was associated with a subsequent ungradeable mydriatic photograph (P=0.001), however, the positive predictive value was poor (34%). Age, posterior subcapsular cataract, and near vision predicted ungradeable status of nonmydriatic photographs (P<0.001, P=0.004, P=0.006, respectively; regression analysis). Nuclear colour and poor definition of the nonmydriatic photograph predicted ungradeable status of mydriatic photographs (P=0.006 & P=0.001, respectively).

CONCLUSION

Inability to visualise the fovea is the commonest cause of an ungradeable image from digital retinal photography. Age and posterior subcapsular cataract were best predictors of ungradeable status of nonmydriatic fundus photographs. Nuclear colour was the strongest predictor for ungradeable mydriatic photography.

Diabetic retinopathy: the unmet needs for screening and a review of potential solutions

Diabetic retinopathy remains the leading cause of severe vision loss and blindness in the developed world, in spite of recognized ocular treatments that are successful at reducing the rate of vision impairment. Retinal photography appears a promising method to perform screening in such a setting utilizing new 45 degrees + retinal cameras that do not require pupil dilation and can be operated by a trained, nonophthalmic technician. Certain developments may make the photography more successful including the conversion to electronic chip camera sensors that allow each picture as it is taken to be immediately projected onto a monitor for evaluation and assessment. Utilizing a nonmydriatic camera, studies of single-field photography through a dilated pupil have demonstrated superior or equal sensitivity to fundus examination by an ophthalmologist in a number of studies. However, photography without pupil dilation, especially in the older age group may result in poor-quality photographs owing to intense bilateral pupil constriction after the first images and also due to the presence of cataracts. Computer analysis of the retinal images allows extraction of quantitative data, not only of the diabetic lesions but also of vascular changes that, up until now, have been impossible by human grading and potentially allows a much more detailed and quantitative evaluation of the progression of retinopathy over time. When success of image processing algorithms is demonstrated for a large number of images taken under screening conditions, the benefits of retinal photography and image processing to provide timely, reliable, quantitative and cost-effective results, will make this the preferred method over physician examination or human grader evaluation of the images.

Interobserver Agreement in the Interpretation of Single-Field Digital Fundus Images for Diabetic Retinopathy Screening

PURPOSE

To assess agreement among a group of ophthalmic care providers, including ophthalmologists and trained nonphysician personnel, in the interpretation of single-field digital fundus images for diabetic retinopathy screening.

DESIGN

Interobserver reliability study.

PARTICIPANTS

Twelve ophthalmic care personnel, including 3 retina specialists, 3 general ophthalmologists, 3 ophthalmic nurses, and 3 ophthalmic photographers.

METHODS

All participants were to read 400 good single-field digital fundus images of diabetic patients from a community hospital. The nonphysician personnel group read the images 1 month after attending a 2-day intensive instruction course regarding diabetic retinopathy screening. The ophthalmologists read the images without additional training. The 3 retina specialists read the images again together 2 months later to form a consensus regarding retinopathy severity and macular edema for each case. All readers used the Early Treatment Diabetic Retinopathy Study standard photographs as guidelines.

MAIN OUTCOME MEASURES

The kappa statistic was used for the reliability assessment of the diabetic retinopathy severity and macular edema, and for the identification of cases that needed referral to ophthalmologists.

RESULTS

There is only fair agreement among all readers. The multirater kappa coefficient for retinopathy severity is 0.34; for macular edema, 0.27; and for referral cases, 0.28. Retina specialists have the best agreement among all groups (kappa = 0.58 for retinopathy severity or macular edema, kappa = 0.63 for referrals). There is also fair agreement when all readers are compared with the consensus of retina specialists (kappas = 0.35, 0.28, and 0.29 for retinopathy severity, macular edema, and referrals, respectively), and the retina specialist group also has the best agreement (kappas = 0.63, 0.65, and 0.67 for retinopathy severity, macular edema, and referrals).

CONCLUSIONS

Without additional training, retina specialists may be the most reliable personnel to interpret single-field digital fundus images for diabetic retinopathy screening. For other ophthalmic care personnel to achieve comparable reliability, a comprehensive instruction course with specific continuing education is essential. Authorized nonphysician interpreters should be experts, and new standard photographs for single-field digital fundus image interpretation may also be required to improve interobserver reliability.

Cerebrovascular Reserve Capacity Is Preserved in a Population-Based Sample of Patients with Type 2 Diabetes Mellitus

BACKGROUND AND PURPOSE

Type 2 diabetes mellitus (DM2) is associated with an increased risk of stroke. DM2 is also associated with cognitive impairments. Vascular dysfunction, such as impaired cerebrovascular reserve capacity (CVR), may be a determinant of these changes, but previous studies on CVR in DM2 have provided variable results in selected populations of patients. We aimed to examine CVR in a population-based sample of DM2 patients.

METHODS

The CO(2) reactivity of the middle cerebral artery was examined using transcranial Doppler ultrasonography in 81 DM2 patients and 38 controls. In DM2 patients CVR was correlated with diabetic parameters, vascular risk factors and cognitive functioning.

RESULTS

CVR was similar in patients and controls (51 vs. 49%). Within the DM2 group, there was no statistically significant relationship between CVR and DM duration, HbA(1c), albuminuria, blood pressure, intima-media thickness and cognition. CVR tended to be lower in diabetic patients with retinopathy [46 vs. 55%, mean difference: -7.9 (confidence interval -18.0, 2.2)].

CONCLUSION

We conclude that CVR is not impaired in unselected patients with DM2 and probably does not, therefore, play a major role in the aetiology of cognitive impairment.

Results of Implementation of the DigiScope for Diabetic Retinopathy Assessment in the Primary Care Environment

Approximately 50% of patients with diabetes in the United States do not undergo recommended ocular evaluations for diabetic retinopathy. The DigiScope (EyeTel Imaging, Inc., Columbia, MD) was developed as a cost-effective and practical telemedicine digital imaging system to screen for diabetic retinopathy in the primary care physician's (PCP) office. The DigiScope has been validated against seven-field stereo color fundus photography for the detection of diabetic retinopathy. This study reports on the implementation of the DigiScope for diabetic retinopathy assessment in the primary care environment. In PCP's offices, patients with diabetes who had not undergone an eye examination in the past year were imaged with the DigiScope. The images were transmitted to a reading center where the need for referral to an ophthalmologist was determined. Nonurgent referral was recommended for patients with diabetic retinopathy greater than a few micro-aneurysms, other ocular pathology, or unreadable images. Referral was deemed "urgent" for patients with sight-threatening disease and evaluation by an ophthalmologist within 72 hours was recommended. Between October 1, 2002 and March 31, 2771 patients with diabetes underwent DigiScope imaging at multiple sites. Nonurgent referral was recommended for 468 patients (17%). Urgent referral was recommended for 71 patients (3%). The images were unreadable in 295 cases (11%). This study indicates that implementation of the DigiScope in the primary care setting is practical and allows screening of patients with diabetes who are otherwise not receiving recommended eye examinations.

A Web-based Telemedicine System for Diabetic Retinopathy Screening Using Digital Fundus Photography

The purpose was to design and implement a Web-based telemedicine system for diabetic retinopathy screening using digital fundus cameras and to make the software publicly available through Open Source release. The process of retinal imaging and case reviewing was modeled to optimize workflow and implement use of computer system. The Web-based system was built on Java Servlet and Java Server Pages (JSP) technologies. Apache Tomcat was chosen as the JSP engine, while MySQL was used as the main database and Laboratory of Neuro Imaging (LONI) Image Storage Architecture, from the LONI-UCLA, as the platform for image storage. For security, all data transmissions were carried over encrypted Internet connections such as Secure Socket Layer (SSL) and HyperText Transfer Protocol over SSL (HTTPS). User logins were required and access to patient data was logged for auditing. The system was deployed at Hubert H. Humphrey Comprehensive Health Center and Martin Luther King/Drew Medical Center of Los Angeles County Department of Health Services. Within 4 months, 1500 images of more than 650 patients were taken at Humphrey's Eye Clinic and successfully transferred to King/Drew's Department of Ophthalmology. This study demonstrates an effective architecture for remote diabetic retinopathy screening.

Web-based screening for diabetic retinopathy in a primary care population: the EyeCheck project

The objective of this study was to evaluate the feasibility of ATA category 2 Web-based screening for diabetic retinopathy in a primary care population in the Netherlands. A total of 1,676 patients in a primary care setting, with diabetes, without known diabetic retinopathy, and without previous screening by an ophthalmologist, were included between January 1 and December 31, 2003. Patients underwent a brief questionnaire and two field retinal photography. Photographs were independently read by two ophthalmologists. Outcome measures were gradability of the photographs, need for pharmacologic pupil dilation, assessment as suspect for presence of diabetic retinopathy, of neovascularization and of diabetic retinopathy, and agreement between graders. Of the population studied, 11.3% of patients required pupil dilation, average transmission time of images was 73 sec, 12.0% of patients had ungradable photographs, 10.4% of the patients with gradable photographs were assessed as "suspect for diabetic retinopathy," and 2.0% were assessed to need urgent referral. Red lesions were present in 3.5% and bright lesions were present in 1.6% of all gradable patients. Neovascularization of the disk was found in one patient. Type 1 patients had much higher rates of "suspect for diabetic retinopathy" (34.5%) than type 2 patients (9.4%). Interrater agreement kappa was 0.93. Web-based screening, using open source technology and uncompressed images, is feasible in a primary care setting, with a high rate of inter-rater agreement. Dilate-as-needed may be a sensible approach for retinal photography. The high incidence of "suspect for diabetic retinopathy" in type 1 diabetes patients illustrates that web-based diabetic retinopathy screening programs for these patients may detect diabetic retinopathy that would otherwise have gone undetected.