Non-mydriatic retinal photography as a screening service for general practitioners

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

OBJECTIVE

To evaluate whether single-field fundus photography can be used as a screening tool to identify diabetic retinopathy for referral for further ophthalmic care.

METHODS

A MEDLINE search of the peer-reviewed literature was conducted in June 2001 for the years 1968 to 2001 and updated in September 2003, yielding 145 articles. The search was limited to articles published in English. The Cochrane Library of clinical trials was also investigated. The authors reviewed the abstracts of these articles and selected 63 of possible clinical relevance for review by the panel. Of these 63 articles, the panel selected 32 for the panel methodologist to review and rate according to the strength of evidence.

RESULTS

Three of the 32 articles reviewed were classified as level I evidence, and 4 were classified as level II evidence. Evidence from level I studies demonstrates that as a tool to detect vision-threatening retinopathy, single-field fundus photography interpreted by trained readers has sensitivity ranging from 61% to 90% and specificity ranging from 85% to 97% when compared with the gold standard reference of stereophotographs of 7 standard fields. When compared with dilated ophthalmoscopy by an ophthalmologist, single-field fundus photography has sensitivity ranging from 38% to 100% and specificity ranging from 75% to 100%.

CONCLUSIONS

Single-field fundus photography is not a substitute for a comprehensive ophthalmic examination, but there is level I evidence that it can serve as a screening tool for diabetic retinopathy to identify patients with retinopathy for referral for ophthalmic evaluation and management. The advantages of single-field fundus photography interpreted by trained readers are ease of use (only one photograph is required), convenience, and ability to detect retinopathy. Further studies will be required to assess the implementation of single-field photography-based programs to confirm the clinical and cost-effectiveness of these techniques in improving population visual outcomes. Future research also should include establishing standardized protocols and satisfactory performance standards for diabetic retinopathy screening programs.

Screening for sight-threatening diabetic retinopathy: comparison of fundus photography with automated color contrast threshold test

PURPOSE

To compare tritan contrast threshold (TCT) with fundus photography in screening for sight-threatening diabetic retinopathy (STDR), before significant visual loss.

DESIGN

Prospective, comparative study.

METHODS

A total of 510 consenting diabetic patients attending a hospital-based photographic screening clinic were recruited over a 2-year period. Exclusion criteria included visual acuity of worse than 6/9, previous photocoagulation, and a history of previous eye disease known to affect color vision. The automated TCT test was performed using a computerized cathode ray tube-based technique. Retinal photography was performed using a Polaroid mydriatic fundus camera with a 45 degrees field. Grading of diabetic retinopathy was carried out by an ophthalmologist using slit-lamp biomicroscopy and a 78-diopters lens. Assessments of sensitivity, specificity, and predictive values for both fundus photography and the TCT test were made.

RESULTS

Both the fundus photography and TCT test correlated significantly with the presence of STDR (P <.0001, chi(2) test). The TCT test yielded a sensitivity of 94% (95% confidence interval [CI], 73%- 100%) and a specificity of 95% (95% CI, 92%- 96%) for detection of STDR compared with a sensitivity of 88% (95% CI, 66%-97%) and a specificity of 95% (95% CI, 93%-97%) with fundus photography. Combined modality improved overall screening performance.

CONCLUSION

The TCT assessment is an effective and clinically viable technique, in comparison with fundus photography, to screen for STDR among a diabetic population. Additionally, our results also showed that combining the TCT test with fundus photography greatly increases the performance of screening for STDR.

Stereo nonmydriatic digital-video color retinal imaging compared with Early Treatment Diabetic Retinopathy Study seven standard field 35-mm stereo color photos for determining level of diabetic retinopathy

OBJECTIVE

To evaluate the ability to determine clinical levels of diabetic retinopathy, timing of next appropriate retinal evaluation, and necessity of referral to ophthalmology specialists using stereoscopic nonmydriatic digital-video color retinal images as compared with Early Treatment Diabetic Retinopathy Study (ETDRS) seven standard field 35-mm stereoscopic color fundus photographs.

DESIGN

Prospective, clinic-based, comparative instrument validation study.

PARTICIPANTS

Fifty-four patients (108 eyes) with type 1 or type 2 diabetes mellitus selected after chart review from a single center to include the full spectrum of diabetic retinopathy.

METHODS

Nonsimultaneous 45 degrees -field stereoscopic digital-video color images (JVN images) were obtained from three fields with the Joslin Vision Network (JVN) system before pupil dilation. Following pupil dilation, ETDRS seven standard field 35-mm stereoscopic color 30 degrees fundus photographs (ETDRS photos) were obtained. Joslin Vision Network images and ETDRS photos were graded on a lesion-by-lesion basis by two independent, masked readers to assess ETDRS clinical level of diabetic retinopathy. An independent ophthalmology retina specialist adjudicated interreader disagreements in a masked fashion.

MAIN OUTCOME MEASURES

Determination of ETDRS clinical level of diabetic retinopathy, timing of next ophthalmic evaluation of diabetic retinopathy, and need for prompt referral to ophthalmology specialist.

RESULTS

There was substantial agreement (kappa = 0.65) between the clinical level of diabetic retinopathy assessed from the undilated JVN images and the dilated ETDRS photos. Agreement was excellent (kappa = 0.87) for suggested referral to ophthalmology specialists for eye examinations. Comparison of individual lesions between the JVN images and the ETDRS photos and for interreader comparisons were comparable to the prior ETDRS study.

CONCLUSIONS

Undilated digital-video images using the JVN system were comparable photographs for the determination of diabetic retinopathy level. The results validate the agreement between nonmydriatic JVN images and dilated ETDRS photographs and suggest that this digital technique may be an effective telemedicine tool for remotely determining the level of diabetic retinopathy, suggesting timing of next retinal evaluation and identifying the need for prompt referral to ophthalmology specialists. Thus, the JVN system would be an appropriate tool for facilitating increased access of diabetic patients into recommended eye evaluations, but should not be construed as a paradigm that would replace the need for comprehensive eye examinations.

Blindness in patients with diabetes who have been screened for eye disease

PURPOSE

Detection of diabetic retinopathy by screening is a major public health concern. Fundus photography has been shown to be a useful screening tool for the detection of diabetic retinopathy. In this paper the authors assess the incidence of blind and partially sighted registration due to diabetic eye disease in patients screened by a mobile fundus photography unit and identify the factors that contributed to loss of vision in the registered group.

METHODS

A retrospective review of blind and partially sighted registrations between 1990 and 1995 was performed in a diabetic population screened by a mobile fundus photography unit in a region with a population of 390,000. The incidence of blind and partially sighted registration in the screened diabetic population was calculated. In the registered group, cause of visual loss, accuracy of photograph reporting, delay in laser treatment, adequacy of laser treatment and non-attendance rates at ophthalmic clinics were assessed.

RESULTS

Of the 5390 patients screened by the mobile unit over 6 years, 68 (210 per 10(5) patient-years) were registered blind or partially sighted, but in only 17 patients (53 per 10(5) patient-years) was this as a result of diabetes. The factors contributing to loss of vision were found to be failure of laser treatment, rapidly progressive disease and poor patient attendance.

CONCLUSIONS

As the majority of visual impairment in patients with diabetes is not due to diabetic retinopathy, this has important implications for screening programmes and may make the St Vincent Declaration targets difficult to achieve. The rate of new blind and partially sighted registration due to diabetes in the screened population was low at 53 per 10(5) patient-years (95% confidence interval, 29-76).

Sensitivity and specificity of photography and direct ophthalmoscopy in screening for sight threatening eye disease: the Liverpool Diabetic Eye Study

OBJECTIVE

To evaluate different methods for community based screening for sight threatening diabetic eye disease.

DESIGN

Prospective study.

SETTING

Mobile screening unit visiting inner city community clinics; hospital assessment clinic (tertiary centre).

SUBJECTS

395 diabetic patients registered with four general practices in an inner city location.

INTERVENTIONS

Community based photography with mydriasis and direct ophthalmoscopy through dilated pupils by an experienced ophthalmologist, both compared with reference standard of slit lamp biomicroscopy by a consultant specialist in medical retinal disease.

MAIN OUTCOME MEASURES

Sensitivity and specificity of screening method and prevalence of sight threatening diabetic eye disease (moderate preproliferative retinopathy, circinate maculopathy, exudate within 1 disc diameter of fixation, other diabetes related eye disease).

RESULTS

358 subjects underwent photography, 326 attended hospital clinic for ophthalmoscopy, and six were ungradable on photographs and biomicroscopy, leaving 320 for analysis. Of these 295 (91%) attended clinic within four months of photography. Sensitivity of detection of eye disease by photography was 89% (95% confidence interval 80% to 98%), significantly better than for direct ophthalmoscopy (65% (51% to 79%)). Analysis of patients with false negative results indicated possible improvement of photographic sensitivity to 93% by addition of stereoscopic macular pair photographs. Specificity of detection of sight threatening eye disease was 86% (82% to 90%) for photography and 97% (95% to 99%) for direct ophthalmoscopy.

CONCLUSIONS

Since high sensitivity is essential for an effective screening programme, a photographic method should be considered as preferred option in national, community based screening programmes. Even in the hands of an experienced ophthalmologist, direct ophthalmoscopy is limited by weaknesses inherent to the instrument.

Detection of retinopathy by non-mydriatic fundus photography in diabetics treated with oral hypoglycaemic agents or diet

OBJECTIVE

To determine the prevalence of retinopathy by non-mydriatic fundus photography in diabetics treated with oral hypoglycaemic agents or diet.

DESIGN

Cross-sectional survey of diabetes-induced fundal changes assessed by fundus photography.

SETTING

Area of Health Centre of Oulu. Population 100,000.

SUBJECTS

All 1,228 diabetic patients, aged 30 years or over and treated with oral hypoglycaemic agents or diet at the Health Centre of Oulu.

MAIN OUTCOME MEASURES

Presence and severity of diabetic retinopathy in fundus photographs, need for laser photocoagulation, age, hypertension, body mass index (BMI), duration of diabetes, type of treatment of diabetes.

RESULTS

Retinopathy was observed in 178 (18%) of those 1,015 diabetics examined at the health centre. Retinopathic changes requiring laser treatment were observed in 15 cases, and eight of them had not been diagnosed earlier. Sixty non-attenders photographed at the Central University Hospital were also included, and 12 of them had retinopathy. The presence of retinopathy was associated with long duration of diabetes, poor glycaemic control, and high systolic blood pressure. No association was detected with sex, age at onset of diabetes, BMI, medication for coronary artery disease, or hypertension.

CONCLUSIONS

Non-mydriatic fundus photography detected a high prevalence of retinopathy in diabetic patients. Half of those with preproliferative changes were previously undiagnosed cases, and five were in need of immediate laser treatment. It is concluded that fundus photography is a useful tool for detecting retinopathy in a primary health care setting.

The quality of photographs produced by the non-mydriatic fundus camera in a screening programme for diabetic retinopathy: a 1 year prospective study

A prospective study was performed on the quality of photographs produced by the non-mydriatic fundus camera used in a hospital-based screening programme for diabetic retinopathy. In 1 year 981 binocular patients were photographed. A photograph of acceptable quality was obtained from 90.5% of eyes and 84.4% of patients had an acceptable photograph of both eyes. The photograph of the second eye was more often unacceptable than that of the first. This tendency was significant in females (p = 0.0196) and when considering the sexes together (p = 0.0044), but not significant in males (p = 0.1042). Photographs of unacceptable quality were obtained significantly more often in patients aged over 55 years for both right and left eyes (p = 0.001). An overall improvement in photographic quality might be achieved by allowing full recovery of flash-induced pupil constriction before taking the second photograph and by dilating those aged over 55 years.

Use of mobile screening unit for diabetic retinopathy in rural and urban areas

OBJECTIVES

To compare the effectiveness of a mobile screening unit with a non-mydriatic polaroid camera in detecting diabetic retinopathy in rural and urban areas. To estimate the cost of the service.

DESIGN

Prospective data collection over two years of screening for diabetic retinopathy throughout Tayside.

SETTING

Tayside region, population 390,000, area 7770 km2.

SUBJECTS

961 patients in rural areas and 1225 in urban areas who presented for screening.

MAIN OUTCOME MEASURES

Presence of diabetic retinopathy, need for laser photocoagulation, age, duration of diabetes, and diabetic treatment.

RESULTS

Compared with diabetic patients in urban areas, those in rural areas were less likely to attend a hospital based diabetic clinic (46% (442) v 86% (1054), p < 0.001); less likely to be receiving insulin (260 (27%) v 416 (34%), p < 0.001 and also after correction for differences in age distribution); more likely to have advanced (maculopathy or proliferative retinopathy) diabetic retinopathy (13% (122) v 7% (89), p < 0.001); and more likely to require urgent laser photocoagulation for previously unrecognised retinopathy (1.4% (13) v 0.5% (6), p < 0.02). The screening programme cost 10 pounds per patient screened and 1000 pounds per patient requiring laser treatment.

CONCLUSION

The mobile diabetic eye screening programme detected a greater prevalence of advanced retinopathy in diabetic patients living in rural areas. Patients in rural areas were also more likely to need urgent laser photocoagulation. Present screening procedures seem to be less effective in rural areas and rural patients may benefit more from mobile screening units than urban patients.

Detection of drusen and early signs of age-related maculopathy using a nonmydriatic camera and a standard fundus camera

PURPOSE

The study was designed to compare the severity of age-related maculopathy as graded from photographs taken using three different techniques.

METHODS

Two methods of nonstereoscopic 45 degrees retinal photography of the macula (through a nonpharmacologically dilated pupil and through a pharmacologically dilated pupil) were compared with results from standard 30 degrees stereoscopic photographs in 112 subjects. Corresponding photographic fields were graded by a masked grader for the presence of any drusen, soft drusen, retinal pigment epithelial degeneration, increased retinal pigmentation, and early and late age-related maculopathy.

RESULTS

Exact agreement between gradings of the 45 degrees photographs taken through nonpharmacologically dilated pupils and 30 degrees photographs taken through dilated pupils was 75% for any drusen, 72% for soft drusen, 72% for retinal pigment epithelial degeneration, 74% for increased retinal pigment, 85% for pure geographic atrophy, and 89% for exudative macular degeneration. The kappa scores varied from 0.33 for geographic atrophy to 0.60 for exudative macular degeneration. Slightly higher rates of agreement between gradings were found after dilation.

CONCLUSION

These data suggest that 45 degrees nonstereoscopic fundus photographs, when graded according to a standard classification scheme, should be considered for detection of age-related maculopathy in situations where the pupils cannot be pharmacologically dilated and retinal specialists are not available to examine the fundus.

Nonmydriatic fundus photography in screening for treatable diabetic retinopathy

Diabetic retinopathy is a complication of both insulin-dependent (type I) and non-insulin-dependent (type II) diabetes. The American Diabetes Association and others recommend screening for retinopathy, beginning 5 years after onset of symptoms for patients with type I diabetes and at the time of diagnosis for patients with type II diabetes. Ideally, diabetic patients are evaluated at recommended intervals by an ophthalmologist. Realistically, however, this is often not feasible, for reasons both of cost and availability. There is evidence that many diabetic patients are being referred too late for intervention, perhaps in part due to lax screening and detection, often the responsibility of internists and other primary care physicians. Data supports the need for a cheap, widely available, easy-to-use, effective screening tool for detecting treatable diabetic retinopathy. To this end, several studies have evaluated nonmydriatic fundus photography, and compared it with more-established methods of detecting diabetic retinal disease. The real question to be considered is whether nonmydriatic fundus photography will help to detect early treatable retinopathy better than the average physician using ophthalmoscopy. Several studies support its usefulness in this regard, and are discussed in this review. Questions remain, however, and further study is warranted in evaluating its potential role.

Screening for diabetic retinopathy in a widely spaced population using non-mydriatic fundus photography in a mobile unit. Tayside Mobile Eye Screening Unit

A screening project was established to assess the prevalence and severity of retinopathy in diabetic patients in Tayside (area: 3000 square miles, population: 390,000). A questionnaire was used to examine patient acceptability. Of 2112 patients photographed during the first year, 32% had abnormal photographs; 20.2% had diabetic retinopathy; 7.4% cataracts; 4.6% non-diabetic eye disease. Among this patient population, 73% were registered at a hospital diabetic clinic. The overall prevalence of diabetic retinopathy was similar between the two groups (hospital 23% vs non-hospital 20%). The prevalence of severe diabetic retinopathy was also similar (hospital 8.5% vs non-hospital 10%). This had been previously unrecognized or incorrectly defined in 6.5% of those not attending a hospital diabetic clinic, compared to 3.7% attending the hospital clinic (p less than 0.01). A favourable response to the service was indicated by 40% of patients with 7% unfavourable and 41% uncommitted. Non-mydriatic fundal photography housed in a mobile unit is a practical and effective method of assessing diabetic retinopathy. It is particularly suitable for screening in a widely spread population.

A relative cost-effectiveness analysis of different methods of screening for diabetic retinopathy

The relative cost and cost-effectiveness of different methods of screening diabetic patients for sight-threatening retinopathy are assessed. The resource costs per screening visit, both to the health service and to patients, of ophthalmoscopic examination by primary screeners including general practitioners, hospital physicians, and ophthalmic opticians are estimated together with those of a similar screening test by ophthalmological clinical assistants. The total resource cost per screen of screening using non-mydriatic photography is also estimated. Using estimates of sensitivity, specificity, and prevalence generated in the screening of 3318 diabetic patients in three UK centres, the relative cost-effectiveness of screening methods is estimated in terms of their cost per true positive case detected. On the assumption that a patient makes a special trip for eye screening, the cost per true positive case detected for primary screeners ranges from 633 pounds for a GP-screened group in one centre to 1079 pounds for another GP-screened group in a second centre; the cost per true positive case detected of photography ranges from 497 pounds for a camera that is taken to general practices in one centre to 1546 pounds for a hospital-based camera. Relative cost-effectiveness changes if, in some contexts, the screening can take place without requiring an additional patient visit, and is strongly related to the relative sensitivity of the screening methods and to the prior probability (prevalence or incidence) of retinopathy in the diabetic population.

Detection of diabetic retinopathy in the community using a non-mydriatic camera

The role of the non-mydriatic fundus camera in detection of diabetic retinopathy was evaluated as part of a comprehensive screening programme for diabetic complications offered to all diabetic patients in a rural town. Retinopathy was demonstrated in 124/358 (35%) of patients screened. Forty-eight patients (13%) were judged to have sight-threatening retinopathy, of whom 29 patients (8% of the total) were not already under the care of an ophthalmologist. However, in only 66% of patients were photographs of both eyes of adequate quality to assess for retinopathy. The percentage of poor quality photographs increased with age in those aged greater than 50 years. It is concluded that the non-mydriatic camera can increase the detection of sight-threatening retinopathy in the community. Although this method of screening is not perfect, because of the number of poor quality photographs, it may be as good as or better than existing screening practices in unselected diabetic populations.

Screening for treatable diabetic retinopathy: a comparison of different methods

The results of the screening of 3318 diabetic patients for sight-threatening diabetic retinopathy in three UK centres are reported. The aims of the study were to determine the extent of diabetic retinopathy in the screened population and to assess the relative effectiveness of different screening methods in appropriately referring cases from a diabetic population, in a context very close to a routine clinical service. Patients were assessed by ophthalmoscopic examination by an ophthalmological clinical assistant. The clinical assistants' referral grades formed the reference standard against which to assess the effectiveness of other screening methods including ophthalmoscopy by primary screeners who were general practitioners (GPs), ophthalmic opticians and hospital physicians, and the assessment by consultant ophthalmologists of non-mydriatic Polaroid fundus photography. The performance of primary screeners based on ophthalmoscopy ranged from a sensitivity of 0.41, with a specificity of 0.89, for one of the GP groups, to a sensitivity of 0.67, with a specificity of 0.96, for the hospital physician group. The performance of the non-mydriatic camera ranged from a sensitivity of 0.35, with a specificity of 0.95, to a sensitivity of 0.67, with a specificity of 0.98.

Comparison of non-mydriatic retinal photography with ophthalmoscopy in 2159 patients: mobile retinal camera study

OBJECTIVE

To determine whether non-mydriatic Polaroid retinal photography was comparable to ophthalmoscopy with mydriasis in routine clinic screening for early, treatable diabetic retinopathy.

DESIGN

Prospective study of ophthalmoscopic findings according to retinal camera screening and ophthalmoscopy and outcome of referral to ophthalmologist.

SETTING

Outpatient diabetic clinics of three teaching hospitals and three district general hospitals.

PATIENTS

2159 Adults selected randomly from the diabetic clinics, excluding only those registered as blind or those in wheelchairs and unable to enter the screening vehicle.

MAIN OUTCOME MEASURES

Numbers of patients and eyes correctly identified by each technique as requiring referral with potentially treatable retinopathy (new vessel formation and maculopathy) and congruence in numbers of microaneurysms, haemorrhages, and exudates reported.

RESULTS

Camera screening missed two cases of new vessel formation and did not identify a further 12 but indicated a need for referral. Ophthalmoscopy missed five cases of new vessel formation and indicated a need for referral in another four for other reasons. Maculopathy was reported in 147 eyes with camera screening alone and 95 eyes by ophthalmoscopy only (chi 2 = 11.2; p less than 0.001), in 66 and 29 of which respectively maculopathy was subsequently confirmed. Overall, 38 eyes received laser treatment for maculopathy after detection by camera screening compared with 17 after ophthalmoscopic detection (chi 2 = 8.0; p less than 0.01). Camera screening underestimated numbers of microaneurysms (chi 2 = 12.9; p less than 0.001) and haemorrhages (chi 2 = 7.4; p less than 0.01) and ophthalmoscopy underestimated hard exudates (chi 2 = 48.2; p less than 0.001).

CONCLUSIONS

Non-mydriatic Polaroid retinal photography is at least as good as ophthalmoscopy with mydriasis in routine diabetic clinics in identifying new vessel formation and absence of retinopathy and is significantly better in detecting exudative maculopathy.