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Q 45What screening tests should be used for diabetic eye damage in adults with Type 1 diabetes?

Author/Title/Reference/YrScottish Intercollegiate Guidelines Network 2001 Management of Diabetes: A national clinical guideline
N=61 studies
Research DesignSystematic review – Guidelines
AimTo determine optimum screening practice for diabetes
PopulationMixed diabetes population
InterventionTechnologies for detection and management of diabetic retinopathy
ComparisonVarious controls
OutcomePrevention, detection or treatment of diabetic retinopathy
CharacteristicsVaried between studies
ResultsRisk identification and prevention
Poor glycaemic control
Raised blood pressure
Increasing number of microaneurysms
Duration of diabetes
Microalbuminuria and proteinuria
Raised triglycerides and lowered haematocrit
Pregnancy
Available evidence suggests that smoking may be a risk factor for diabetic retinopathy in type 1 diabetes.
Patients with multiple risk factors should be considered at a high risk of developing diabetic retinal disease
Diabetic retinal disease is the commonest form of visual impairment in type 1 diabetes. Patients have a twofold increased risk of cataract. Risk increases with poor glycaemic control.
Tight blood glucose control reduces the risk of onset and progression of diabetic eye disease in type 1 and 2 diabetes.
Reducing HbA1c by 1.5% and if possible to 7% and reducing blood pressure to 144/82 mm Hg reduces incidence and progression sight-threatening diabetic eye disease. This is likely also to be so for type 1 diabetes.
Reducing BP and HbA1c below these targets is likely to reduce the risk of eye disease further. Microvascular endpoints (including retinopathy) are decreased by 37% with each 1% reduction in Hba1C and by 13% for each 10mm Hg reduction in systolic blood pressures.
Good glycaemic and blood pressure control should be maintained to prevent onset and progression of diabetic eye disease
Rapid improvement of glycaemic control can results in short worsening of diabetic retinal disease although the long term outcomes remain beneficial
Sight threatening retinal disease, if present, should be stabilised before rapid clinical improvements in glycaemic control are achieved.
There is absence of good evidence for any additional benefits of ACE inhibitors in diabetic eye disease. 1 RCT exists but is of poor methodological quality.

Cardiovascular risk factors:
Cigarette smoking. The prevalence of cigarette smoking is significantly higher in patients with diabetes than those without (33.27%)
Observational studies have shown that smoking is an independent risk factor in people with diabetes and the excess risk attributable to smoking is more than additive
Dyslipidaemia:
Observational studies have shown dyslipidaemia to be commonly present in Type 2 diabetes.
An increased concentration of LDL cholesterol or total cholesterol has also been identified as an independent risk factor for cardiovascular morbidity and mortality. Each 1 mmol/l reduction of LDL cholesterol represents a 36% reduction in risk of CVD disease. Triglycerides are also an independent marker of increased risk of cardiovascular disease in Type 2 diabetes.
The ongoing Fenofibrate Intervention and Event Lowering id Diabetes (FIELD) study (n=8000) is addressing whether lowering serum triglyceride concentrations reduces CVD events in people with diabetes with and without coronary heart disease
Hypertension:
Hypertension is positively related to risk of CVD death, with a progressive increase in risk with rising systolic pressures. Each 10 mmHg reduction in systolic pressure is associated with a 15% (95% CI 12 to 18%) reduction in the risk of CVD death over 10 years
Hyperglycaemia:
Increasing glycaemia (measured as HbA1c) results in increased risk of CVD morbidity and mortality. Each 1% reduction in HbA1c is associated with a 21% (95% CI 15 to 27%) reduction in the risk of diabetes related death and specifically a 14% reduction for MI over 10 yrs. No lower threshold can be demonstrated
Other risk factors:
No studies identifying obesity as an independent risk factor in established diabetes were identified. In addition to its role in identifying patients at risk of diabetic nephropathy, microalbuminuria is an independant marker associated with a doubling in cardiovascular risk. There is insufficient evidence to determine whether reducing albumin excretion rate specifically reduces cardiovascular morbidity of mortality

Screening
Who:
Screening is an effective at detecting unrecognised sight-threatening retinopathy
In type diabetes, pre-proliferative retinopathy has been identified 3.5 years after diagnosis in post-puberty patients, and within two months of onset of puberty
Patients with no retinopathy at baseline have greater than 1% chance of developing sight-threatening retinopathy within two years.
Patients with existing diabetic retinal disease may require more frequent retinal examination
Systematic annual screening for diabetic retinal disease should be provided for all people with diabetes
Patients with type 1 diabetes should be screened from diagnosis
How:
Diabetes UK propose that an effective screening system have 95% specificity, 80% sensitivity and less than 5% technical failure rate
Retinal photography frequently achieves 80 % sensitivity and is more effective than ophthalmoscopy, even when carried out by trained operators
Dilated direct ophthalmoscopy should only be used for opportunistic screening.
Screening modalities should aim to detect sight threatening retinal disease with a sensitivity ≥ 80% and specificity ≥ 95%
Patients with ungradeable retinal photography’s should receive slit lamp and indirect ophthalmoscopy examination where possible.
Where possible and practical screening should be performed at a site convenient to patients.
Grading:
Digital imaging is more sensitive than Polaroid prints and similar to 35mm film. Initial data indicates high-resolution automated techniques to identify the absence of microaneurysms on digital images with a sensitivity of 85%, although more research is needed before validation
All screening modalities should undergo quality assurance checks (at least 1% of all screening events).
Retinal photographs should be graded using digital images or 35 mm film by and appropriately trained grader.

Treatment
Referral intervals
Delay in treatment of greater than 2 years from diagnosis of sight-threatening diabetic retinopathy is associated with poor outcomes and severe visual loss.
Royal College of ophthalmologists recommendations:
Assess by ophthalmologist within 4 weeks if:
There is unexplained drop in visual acuity, hard exudations within 1 disc diameter of the fovea, macular oedema is present, there are unexplained retinal findings, pre-proliferative or more advanced (severe) retinopathy is present
Assess by ophthalmologist within 1 week if:
There is new vessel formation, there is evidence of pre-retinal or vitreous haemorrhage, rubeosis iridis is present
Assess by an ophthalmologist on the same day if
There is sudden loss of vision, there is retinal detachment
Method of assessing diabetic retinopathy
Slit lamp biomicroscopy by and appropriately experienced ophthalmologist is as good as the gold standard of 7-field stereoscopic photography for the assessment of clinically significant macular oedema (CSMO) and proliferative diabetic retinopathy and severe non-proliferative diabetic retinopathy

Rehabilitation
Low vision clinics and community self-help groups as part of a low vision service can improve the quality of life and functional ability for patients with visual impairment.
Community support, low vision aids and training in their use should be provided to people with diabetes and visual impairment.
Patients with visual impairment should be assisted to register as blind/partially sighted at an early stage.

Additional recommendations made on laser treatment and vitrectomy
Hierarchy of Evidence GradingIa (various)
CommentsSystematic review of the literature carried out using an explicit search strategy devised by the SIGN information team
All searches covered systematic reviews, meta-analysis and randomised controlled trials, extended to cover observational studies where appropriate.
All searches covered: Cochrane Library, Embase, Healthstar and Medline. Where appropriate they also covered CINAHL and PsychInfo.
Years searched: 1991–2000
All selected papers were evaluated using standard methodological checklists before conclusions were considered as evidence.
Specific clinical questions addressed are not detailed in the guideline report
To address patients view representation was provided by Diabetes UK on the advisory group and recommendations panel.
Diabetic retinopathy working party included a Diabetes Care Adviser from Diabetes UK
Not all studies use an appropriate Gold Standard
Evidence statements and recommendations all relate only to care for individuals rather than establishment of a national screening programme.
Individual studies included in the review are small, potential selection bias could limit their individual generalisability
Other biases such as experience, training and motivation may be present given the limited numbers of personnel in many of the studies.
Trials includedSee original study
Reference/Citation
Author/Title/Reference/YrNICE. Management of type 2 diabetes: Retinopathy - screening and early management. 1–24. 2002.
N=N=15000+
Research DesignSystematic review - Guidelines
AimGuideline covers the clinical care and management of people with diagnosed type 2 diabetes in primary and secondary care.
PopulationIncluded studies for type 1 and type 2 diabetes specifically addressing screening for, and early management of, diabetic retinopathy
InterventionA number of different diagnostic screening tests are considered
ComparisonVarious gold standards are used
OutcomeDetection of diabetic retinopathy
CharacteristicsVaried between studies
ResultsNational screening committee has recommended screening for diabetic retinopathy as a national priority
Previous literature review concluded that there was inconsistent and inconclusive evidence on the most effective methods for screening.
Bachmann & Nelson 1998 pooled data from many screening studies and concluded that retinal photography was the screening test of choice

Sensitivities and specificities of screening tests
Ophthalmoscopy:
GP test sensitivity levels = 33%–66% in the detection of referable sight-threatening, pre-proliferative, proliferative or serious retinopathy.
A larger study showed for 2350 screened by 318 general practitioners, sensitivity for detecting sight threatening retinopathy was 41%–67%
Opticians and optometrists:
Sensitivity of detection of referable proliferative or sight threatening retinopathy ranged from 48%–100%
Ophthalmologists
Five studies evaluated ophthalmologists using ophthalmoscopy (indirect ophthalmoscopy, n=4). For sight threatening and proliferative retinopathy, sensitivity of detection was 65% and 70% respectively. Studies evaluated individual ophthalmologists, limiting the generalisability of this statement
Other professionals:
Effectiveness of other professionals such as diabetologists, nurses, junior doctors, hospital physicians, and technicians. Sensitivities ranged from 27% to 81% in detecting serious or proliferative retinopathy.
In summary: overall the studies demonstrate that direct ophthalmoscopy does not usually meet the required standards for retinopathy screening and review. There is some limited evidence that professionals using indirect slit-lamp ophthalmoscopy can achieve the required standards

45º retinal photography
In general specificities are lower than those with ophthalmoscopy. However, sensitivities are higher for retinal photography.
General practitioners
Sensitivity ranged from 87% to 100% in the three studies (all using mydriatic photography) in the detection of proliferative sight threatening or referable retinopathy.
Opticians/optometrists
Mydriatic 35 mm photographs taken at general practices and assessed by optometrists achieved a level of sensitivity greater than 91%
Ophthalmologists/ophthalmologist assistants
Two UK studies showed sensitivities of 89% to 93% for non-mydriatic and mydriatic photographs, respectively
Other professionals
Sensitivities for the detection of sight threatening or proliferative retinopathy in two studies ranged from 60% to 98%, while in the third sensitivities ranged from 25% to 50%
Diabetes specialists achieved sensitivities for sight threatening retinopathy of 89% in mydriatic retinal photography

Digital imaging techniques: produce an instant enlarged retinal image on a computer monitor. Complete agreement in grading retinopathy seen between digital and conventional photography in 93% of eyes.
To prove the usefulness of digital imaging techniques, further evaluation is needed against acceptable reference standards.

Ophthalmoscopy combined with 45º retinal photography:
Combining these two techniques increased sensitivity for detecting sight threatening retinopathy in all operators across five studies

Studies of the use of 45º retinal photography demonstrate that it is possible to reach an acceptable standard of clinical practice with such methods. The results are not dependent on the type of professional involved, but data for between-observer variations underline the need for training in reading the photographs or images.

Combined studies of ophthalmoscopy with retinal photography demonstrate that although retinal photography may reach an acceptable standard of sensitivity and specificity, ophthalmoscopy is still below standard. Therefore ophthalmoscopy should not be the method of choice of most professionals for screening/review of retinopathy.

Effectiveness of screeners and screening methods:
Comparison of healthcare professionals
No studies reported whether differences found in sensitivities of healthcare professionals were statistically significant

Comparison of ophthalmoscopy and non mydriatic retinal photography
Sensitivities between these two methods were not statistically significant.
In detecting moderate to severe and proliferative retinopathy, assessment of non-mydriatic retinal photographs had a higher sensitivity than ophthalmoscopy interpretation by ophthalmologists (61% vs. 33%) but these differences were not statistically significant. Another study showed significantly higher specificity with ophthalmoscopy than non-mydriatic photographs (pless than 0.0001)

Comparison of ophthalmoscopy and mydriatic retinal photography
Three studies showed better sensitivity achieved by mydriatic photographs than ophthalmoscopy and similarly for detection of moderate to severe and proliferative retinopathy. In the detection of sight threatening retinopathy retinal photographs achieved sensitivities of 87% compared to 66% in ophthalmoscopy

Comparison of mydriatic and non-mydriatic retinal photography:
Mydriatic photography was demonstrated to have greater sensitivity than non-mydriatic photography in one study comparing the two methods, but no significant difference was seen in a second study. Comparison of two studies evaluating these two methods individually shows a greater sensitivity (87%, 91% and 89%) compared to non-mydriatic retinal photography (56% and 60% sensitivity)

Mydriatic 45º retinal photography/imaging appears the most effective test when screening for, or when reviewing established diabetic retinopathy

Visual acuity testing
There is a lack of discrete evidence about the role and usefulness of visual acuity testing in retinopathy screening. As a result no recommendation for its use in systematic screening programmes has been included in the National Screening Committee report.
However broad consensus exists for its usefulness as an essential element of the overall approach to eye care for people with diabetes, and therefore an important part of clinical practice. The Royal College of ophthalmologists clinical practice guideline include its use as part of the overall eye care approach. This view was supported by the retinopathy working group.

Macular oedema
Diagnosis of macular oedema rests on the use of stereoscopic, slit lamp, indirect ophthalmoscopy in expert hands.
Presence of macular oedema requires referral within four weeks.
Due to the difficulty of differentiating non-significant and clinically significant macular oedema, the use of visual acuity testing is recommended for routine proactive. Reduced visual acuity is an indication for specialist referral.

Mydriasis
Mydriasis using tropicamide (0.5–1%) is safe and the risk of inducing acute glaucoma was close to zero.
Stronger combined mydriatics had an overall risk of between 1/3300 and 1/20000 of inducing acute glaucoma.
Use of pilocarpine to reduce mydriasis is potentially harmful and should be discouraged.
Hierarchy of Evidence GradingNICE
CommentsBased on Hutchinson A, McIntosh A, Peters J et al 2001 Clinical guidelines and evidence review for Type 2 diabetes: Diabetic retinopathy: early management and screening. Sheffield: ScHARR, University of Sheffield
Areas of care covered by the evidence review:
Screening method
Professional performing screening method
Location of screening
Classification of patient of result of screen
Screening interval
Risk factors and speed of progression
Full details of the methodology are outlined in the document
Databases Searched: Cinhal, Cochrane Trials Register, Embase, Healthstar, Medline, Psyclit, Science Citation, Social Science Citation, HEED, NHS Economic Evaluation Database for Economic Evaluations, ECRI HTAIS. Trial registers searched for ongoing and unpublished trials and conference proceedings were examined using the Index to Scientific and Technical Conference Proceedings (ISI). Access to grey literature was through the HMIC database and SIGLE.
Databases searched from 1983–1999
Search terms not included.
Details of search strategies available from the authors.
Assessment and grading of papers retrieved was conducted independently by two reviewers and disagreements were resolved by discussion.
Papers graded according to study design using the AHCPR hierarchy
Specific clinical questions addressed are not detailed in the guideline report
To address patients view representation was provided by Diabetes UK on the advisory group and recommendations panel.
Diabetic retinopathy working party included a Diabetes Care Adviser from Diabetes UK
Not all studies use an appropriate Gold Standard
Evidence statements and recommendations all relate only to care for individuals rather than establishment of a national screening programme.
Individual studies included in the review are small, potential selection bias could limit their individual generalisability
Other biases such as experience, training and motivation may be present given the limited numbers of personnel in many of the studies.
Trials includedSee original study
Reference/Citation201
Author/Title/Reference/YrHenricsson M, Karlsson C, Ekholm L, Kaikkonen P, Sellman A, Steffert E, Tyrberg M 2000 Colour slides or digital photography in diabetes screening— a comparison. Acta Ophthalmologica Scandinavia 78:164–168
N=279 diabetic patients
n=200 screened with digital retinal images vs. colour photography
n=79 screened with digital retinal images plus digital redfree photography vs. colour photography
Sweden
Research DesignDiagnostic study
AimA study to evaluate the accuracy of screening tests
PopulationType 1 and Type 2 diabetes
Intervention50° Digital colour photography with the Topco Imagenet System
80 patients were also screened with digital redfree, monochrome, black and white images using the same system
Comparison50º 35mm retinal colour photography performed in pharmacological mydriasis
OutcomeScreening accuracy
Digital images and slides were taken by an ophthalmologic nurse.
Grading of digital images and slides were performed by the same ophthalmologic nurse and by an ophthalmologist independently, at different times, and in a different order. Inter-grader variation was obtained by comparing gradings
Characteristicsmean age 59 (10–84), men=167 (60%), patients with no diabetic retinopathy = 142 (51%)
ResultsIntragrader and intergrader agreement: Intragrader: Ophthalmologists: 77% (weighted kappa 0.84; 95% CI 0.74— 0.93) for digital retinal images and 83% (weighted kappa 0.84; 95% CI 0.74— 0.98) for colour slides, compared to Ophthalmic nurses: 70% (weighted kappa 0.77; 95% CI 0.68— 0.87) for digital retinal images and 84% (weighted kappa 0.88; 95% CI 0.78— 0.97)
Exact Intergrader agreement was achieved in 77% of grading for digital colour images, 85% in colour slides and 71% of digital redfree images
Digital colour images vs. colour slides: Exact agreement in 82% (weighted kappa 0.88; 95% CI 0.80–0.96)
Undergrading in digital images was found in 34 patients (12%) and overgrading in 15% of patients
Taking digital colour images as a reference standard, sensitivity and specificity for detection of any retinopathy on digital images is 93% and 91% respectively. The positive predictive value is 91% and negative predictive value, 93%
Digital redfree images vs. colour slides: Exact agreement in 66% (weighted kappa 0.79; 95% CI 0.64–0.91), overgrading occurred in 25 patients (32%) and undergrading in 2 patients (3%)
Digital redfree images and redfree black and white images vs. colour slides: There was an 85% agreement between the two digital images graded together and colour slides (weighted kappa 0.86; 95% CI 0.71–1.00). Retinopathy was overgraded in 9 patients (11%) and undergraded in 3 patients (5%)
Hierarchy of Evidence GradingDS
CommentsNurses and ophthalmologists had no knowledge of the patients clinical data
Classification of DR was by modified Wisconsin Epidemiologic Study of Diabetic Retinopathy
Digital images were enhanced at the examiners discretion
Diabetic retinopathy was graded on Digital colour and Digital redfree images first in separately and then together
Discrepancies in grading were resolved by an independent adjudicator
Regrading of the colour images of the first 200 patients by each examiner was carried out after six months
Study designed with a statistical power of 80% for detecting a difference in the grading of 10 retinopathy levels, given a significance level of 0.05
Patients were mainly free of diabetic retinopathy. Only a small proportion of patients included in this trial had proliferative diabetic retinopathy graded as severe or above, thus interventions are not being tested for diagnosis of more severe retinopathy
Reference/Citation
Author/Title/Reference/YrLarsen, N., Godt, J., Grunkin, M., Lund-Andersen, H., & Larsen, M. 2003, "Automated detection of diabetic retinopathy in a fundus photographic screening population", Investigative Ophthalmology & Visual Science., vol. 44, no. 2, pp. 767–771.
N=N=260 eyes in 137 diabetic patients.
Location: The Steno Diabetes Center, Greater Copenhagen area of Denmark.
Sites:1.
Research DesignDiagnostic study.
AimThe study evaluated the performance of an automated fundus photographic image-analysis algorithm in high-sensitivity and/or high specificity segregation of patients with diabetes with untreated diabetic retinopathy from those without retinopathy.
PopulationInclusion criteria per patient were an established history of diabetes mellitus, type 1 or type II and availability of at least one macula-centred colour fundus photograph from at least one eye. Exclusion criteria per eye were previous photocoagulation or surgical treatment of diabetic retinopathy or other vitreoretinal disease and media opacities precluding adequate visualization of the fundus by fundus photography, as evaluated at the routine screening sessions.
InterventionAn automated fundus photographic image-analysis algorithm (Retinalyze System; Retinalyze A/S, Hørsham, Denmark).
ComparisonThe reference standard which was a grading of macula-centred slides by an experienced ophthalmologist who classified each eye as having or not having diabetic retinopathy. The photographs were shown in random order of presentation. The reference grader was allowed as much time as needed to review the slides. The grading was made with the aid of magnifiers and a slide projector. Additionally comparisons were made with routine grading by a retina specialist.
OutcomeSensitivity and specificity to detect retinopathy.
CharacteristicsNo patient characteristics reported.
ResultsThe automated lesion detection correctly identified 90.1% of patients with retinopathy and 81.3% of patients without retinopathy.
All patients with false-negative gradings had been reference-graded as having questionable retinopathy or minimal nonproliferative retinopathy with red lesions only.
A per-eye analysis demonstrated that the automated lesion detection could be adapted to simulate various visual evaluation strategies.
When adapted at high sensitivity, the automated system demonstrated sensitivity at 93.1% and specificity at 71.6%. When adapted at high specificity the automated system demonstrated sensitivity at 76.4% and specificity at 96.6%, closely matching routine visual grading at sensitivity 76.4% and specificity 98.3%.
Hierarchy of Evidence GradingDS
CommentsAuthors conclusions: Automated detection of untreated diabetic retinopathy in fundus photographs from a screening population of patients with diabetes can be made with adjustable priority settings, emphasizing high-sensitivity identification of diabetic retinopathy or high specificity identification of absence of retinopathy, covering opposing exremes of visual evaluation strategies demonstrated by human observers. The results warrant further study of the method’s practical applicability in clinical screening practice.
Reference/Citation
Author/Title/Reference/YrLin, D. Y., Blumenkranz, M. S., Brothers, R. J., & Grosvenor, D. M. 2002, "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.[comment]", American Journal of Ophthalmology., vol. 134, no. 2, pp. 204–213.
N=N= 403 consecutive subjects under care for diabetes mellitus. Only 197 patients completed all 3 tests. 99% completed digital imaging however over 70% returned for the dilated ophthalmoscopy examination and 58% for the standard seven field colour photography.
Location: The Kaiser Oakland Medical Center (California)- a large health care maintenance organization.
Sites:1.
Research DesignDiagnostic study.
AimTo evaluate single-field digital monochromatic nonmydriatic fundus photography as an adjunct in screening of diabetic retinopathy.
PopulationEligible patients included both type I and type II diabetic patients with any disease duration. Patients were ineligible if they were less than 21 years of age, dad received laser photocoagulation treatment for diabetic retinopathy in either eye, or had been seen by an ophthalmologist for a retinal examination within the last 12 months.
InterventionSingle-field digital monochromatic nonmydriatic fundus photography.
ComparisonDilated ophthalmoscopy by an ophthalmologist (the current clinical standard) and seven Early Treatment Diabetic Retinopathy Study (ETDRS)standardised 35mm colour stereoscopic mydriatic images (the reference standard which has been used in clinical trials).
OutcomeAll digital and colour photographs were classified by a standard modification of the ETDRS scale. The Kaiser Permanente Medical Group Diabetic Retinopathy criteria were used to evaluate images for referral. Any patient with retinopathy greater than mircoaneursyms in either eye (ETDRS retinopathy level greater than/=35) was recommended for further consultation and treatment. No referral was defined as ETDRS retinopathy level less than/=20). This “referral” and “no referral” dichotomy was used in the sensitivity and specificity analysis. The percentage of overcalls, undercalls, exact agreements and Kappa (k) values were examined.
CharacteristicsOf the participants with all 3 tests completed, 58% were male and 75% were aged 40–69 years (no mean age reported). 53% were African American, 23% were Caucasian American and 15% Asian American. The exclusion of participants who failed to complete all three tests did not result in any significant age or race/ethnicity redistribution.
ResultsThere was highly significant agreement (κ=0.97, P=0.0001) between the degree of retinopathy detected by a single nonmydriatic monochromatic digital photograph and that seen in seven standard 35mm colour stereoscopic mydriatic fields.
The sensitivity of digital photography compared with colour photography was 78% with a specificity of 86% for referral/no referral for retinopathy.
Agreement was poor (k=0.40, P=0.0001) between mydriatic ophthalmoscopy and the seven-field standard 35mm colour photographs.
Sensitivity of ophthalmoscopy compared with colour photography was 34%, with a specificity of 100%.
Hierarchy of Evidence GradingDS
CommentsAuthors conclusions: A single nonmydriatic monochromatic wide-field digital photograph was more sensitive for diabetic retinopathy screening than mydriatic ophthalmoscopy, the currently accepted screening method. When adjudicated by standard seven-field colour photographs, the higher sensitivity of digital photography primarily reflected the reduced sensitivity of ophthalmoscopy in detecting early retinopathy.
It is notable that of the participants recruited, only 48.5% completed the 3 tests. This is mainly due to the number of participants who did not complete other tests after their digital imaging. It is stated however that included and excluded participants did not demonstrate any significant difference in severity of diabetic retinopathy and the authors explain that this may be due to the greater convenience and comfort of the digital photography method.
Digital images and seven-field colour photographs were read in a standard fashion at a remote reading centre by a specially trained, experienced and certified reader. Digital images were read within 3 working days of receipt and the colour fundus photographs were read approximately 4 weeks later after film processing. The reader was masked to the original digital readings. The opthalmologists and research associates (the latter responsible for recruitment, consent, demographic data collection and digital imaging) were not masked as to the identity of the patients.

The included and excluded participants did not demonstrate any significant difference in severity of diabetic retinopathy.
Reference/Citation
Author/Title/Reference/YrMaberley, D., Cruess, A. F., Barile, G., & Slakter, J. 2002, "Digital photographic screening for diabetic retinopathy in the James Bay Cree", Ophthalmic Epidemiology., vol. 9, no. 3, pp. 169–178.
N=N=200 eyes of 100 consecutive subjects.
The study was performed in the remote communities of Moose Factory and Moosonee, Ontario, Canada. The diabetic retinopathy screening programme in Western James Bay is based at the regional hospital in Moose Factory.
Research DesignDiagnostic study.
AimTo evaluate the use of a single, 45-degree fundus image from a non-mydriatic camera for the triage of subjects at risk for diabetic retinopathy in comparison to a complete retinal assessment by a retina specialist (the reference standard).
PopulationOne hundred consecutive patients recruited from the diabetic retinopathy screening programme.
InterventionThe subjects’ retinas were photographed by an ophthalmic photographer with a Topcon™ TRC-NW5SF non-mydriatic camera connected to the Topcon IMA-GEnet™2000 system. (For 30 eyes a minimally trained health care worker also took the photographs). Digital retinal colour photographs of a 45-degree field were generated. All images were coded for patient confidentiality and sent electronically for evaluation to Queens University, Ontario and the Lu Esther T Mertz Retinal Research Unit, New York. A retina specialist at each centre performed the image evaluations. These examiners were blinded to the clinical diagnosis of the subjects.
ComparisonAll participants were evaluated by one of two retinal specialists who performed a complete ocular assessment including anterior segment slit-lamp examination, dilated indirect ophthalmoscopy, and slit lamp biomicroscopy with a 78 diopter lens.
OutcomesThe Kappa statistic for two independent observers for the identification of retinopathy from the digital images. Sensitivities, specificities, positive predictive values and negative predictive values calculated from the digital images using the clinical examinations of the retina as the reference standard.
Characteristics31% male. The mean age was 54.6 years.
ResultsThe Kappa statistic for the two independent observers was 0.85 (p less than 0.001) for the identification of retinopathy from the digital images.
The sensitivity of the digital camera for the evaluation of any retinopathy was 84.4% whilst for clinically significant macular oedema and or proliferative disease it was over 90%. For the identification of any retinopathy, specificity was 79.2% +/−5.1%, positive predictive value was 73.0%+/−6.4% and negative predictive value was 88.4%+/− 4.3.
Unreadable (low quality) images comprised only 1% of all images. There was no statistical difference in the quality of images taken by the ophthalmic photographer and the minimally trained health care professional (Chi Square Test 2.61, p=0.27).
Hierarchy of Evidence GradingDS
CommentsAuthors conclusions: The use of a single digital retinal image for the evaluation of diabetic retinopathy was performed with a high degree of inter-observer concordance and a high degree of sensitivity. The value of this finding rests in the fact that a simple and easily implemented photographic protocol is required if hundreds of geographically isolated communities are to be evaluated in a timely fashion using a small number of cameras and minimally trained technicians.

The study does not specify which type of diabetes the subjects have however it seems likely that it is a mixed type I and type II population.

The study was performed in the remote communities of Moose Factory and Moosonee, Ontario. The prevalence of diabetes here is close to 30% for individuals over 45 years of age. It is not thought that this very specific population inhibits the generalisability of the study when considering diabetic retinopathy screening.
Reference/Citation

From: Appendix D, Evidence tables

Cover of Type 1 Diabetes in Adults
Type 1 Diabetes in Adults: National Clinical Guideline for Diagnosis and Management in Primary and Secondary Care.
NICE Clinical Guidelines, No. 15.1.
National Collaborating Centre for Chronic Conditions (UK).
Copyright © 2004, Royal College of Physicians of London.

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