Beyond retinal screening: digital imaging in the assessment and follow-up of patients with diabetic retinopathy

Abstract

Many screening methods are available for detecting diabetic retinopathy. However, once patients develop retinopathy, it is unclear as to what method should be used for their review. We describe a novel and integrated system for the screening and treatment of diabetic retinopathy using high street optometrists for primary screening and digital imaging as a secondary screening tool, with referral to a joint retinal clinic only where ophthalmological intervention may be required. Of 3586 patients screened by optometrists, 328 were classified as having moderate/severe pre-proliferative retinopathy or diabetic maculopathy. Patients with proliferative retinopathy (1% of the total) were recalled directly to the joint retinal clinic. A consecutive sample (281) of these patients, together with a further 100 classified by the optometrists as having no or background retinopathy were compared using digital images and standard 35 mm colour transparencies. These, together with the original optometrist reports, were reviewed independently and individually by an ophthalmologist. A further sample of 124 patients who had undergone both digital imaging and ophthalmologist slit-lamp examination were also compared. Comparison of 35 mm colour transparencies with optometrist reports showed the latter had a sensitivity for detecting sight-threatening retinopathy (STR) of 62%, a specificity of 84%, and a kappa score of 0.62. The results for digital images were 90%, 97%, and 0.90, respectively, although the extent of retinopathy was under-reported in 10 patients. With ophthalmologist slit-lamp examination as the gold standard, the sensitivity of digital imaging was 90% with a substantial level of agreement between them (kappa 0.61). We conclude that digital images provide an efficient method for the follow-up of patients with established or previously treated retinopathy.

Is screening with digital imaging using one retinal view adequate?

“…9 Screening studies have shown that up to 10% of diabetics have sight-threatening retinopathy. 10,11 Up to 40% of type II diabetics have some retinopathy at diagnosis.…”

Evaluation of the effect of JPEG and JPEG2000 image compression on the detection of diabetic retinopathy

“…The sensitivity to detect microaneurysms is not as good on digital photography as on conventional 35-mm photography, although several authors have found good agreement between both techniques for DR grading, [14][15][16] the poorest agreement between DR grades was recorded at level 21, characterized by the presence of few microaneurysms. [17][18][19] This is due to the lower resolution of digital photography, which makes the images granular and increases the number of questionable lesions when grading for microaneurysms.…”

Assessing diabetic retinopathy using two-field digital photography and the influence of JPEG-compression

“…Our results do not seem to be as good as Kerr's, who found a kappa of 0.90 for the agreement between 35 mm and digital images for the detection of vision-threatening retinopathy [2]. The most likely explanation is that their results were from a DR screening service, with lower rates of vision-threatening DR than in our population.…”

“…The resolution of 35-mm images is still higher than the digital images used in ophthalmology. Two British studies report an 85-90% sensitivity for the detection of sight-threatening retinopathy using digital images, which is considered to be sufficient [2,3]. On the other hand, an American survey reports that 15% of neovascularisations are missed on digital photographs.…”