MP 9.03.13

Digital Imaging Systems for the Detection and Evaluation of Diabetic Retinopathy

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Medical Policy
Section Miscellaneous Policies	Original Policy Date 11/9/04	Last Review Status/Date Reviewed with literature search/2:2005
Issue 4:2005		Return to Medical Policy Index

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Disclaimer

Our medical policies are designed for informational purposes only and are not an authorization, or an explanation of benefits, or a contract.  Receipt of benefits is subject to satisfaction of all terms and conditions of the coverage.  Medical technology is constantly changing, and we reserve the right to review and update our policies periodically.

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Description

Policy

Policy Guidelines

Benefit Application

Rationale

Diabetic retinopathy is the most frequent cause of new cases of blindness among adults aged 20–74 years. The likelihood of retinal changes increases with length of time the condition has been existent. After 20 years of disease, almost all patients with type 1 and >60% of patients with type 2 diabetes will manifest microvascular changes characteristic of the disease. (1)

Retinopathy progresses, at varying rates, from asymptomatic, mild nonproliferative abnormalities to proliferative diabetic retinopathy (PDR) with new blood vessel growth on the retina and posterior surface of the vitreous. Resultant vision loss may be due to any of several mechanisms. Central or acute vision may be impaired from edema that develops from increased vascular permeability or from ischemia from capillary nonperfusion. The new blood vessels that occur in PDR may stimulate the development of fibrous tissue resulting in bleeding and traction retinal detachments. (2)

The value of screening for diabetic retinopathy is well established. Diabetic retinopathy has few visual or ocular symptoms until vision loss develops. Laser photocoagulation is effective at retarding the progression of the changes but uncommonly is able to restore lost vision. Because treatments are aimed at preventing vision loss, and retinopathy can be asymptomatic, it is important to detect disease and begin treatment early in the process. The benefit of early treatment of diabetic retinopathy was established in the large Early Treatment Diabetic Retinopathy Study (ETDRS) supported by the National Eye Institute (NEI). (3)

Annual dilated, indirect ophthalmoscopy coupled with biomicroscopy or 7-standard field stereoscopic 30°fundus photography have been considered to be the screening techniques of choice. (4) Because these techniques require a dedicated visit to a competent eye care professional, typically an ophthalmologist, there is underutilization of this screening recommendation by at-risk members. The under-use rate is estimated to be 30% or higher, (5) which has resulted in the exploration of retinal imaging, using film or digital photography, as an alternative to direct ophthalmic examination of the retina.

A number of photographic methods have been evaluated that allow images of the retina to be captured and then interpreted by expert readers who may not be located conveniently to the patient. This local acquisition/remote interpretation technique was used to consistently detect and evaluate the retinal changes of participants in the ETDRS. The ETDRS used 7 mydriatic standard field 35-mm stereoscopic color fundus photographs evaluated by a single reading center. Digital fundus photography has been evaluated as an alternative to conventional film photography. (2) Digital imaging has the advantage of easier acquisition, transmission, and storage. In addition, the potential for digital images of the retina to be acquired in a primary care setting and evaluated by trained readers in a remote location with retinal specialist consultation exists.

A number of studies have reported on the agreement regarding the presence and stage of retinopathy based on ophthalmoscopy versus photography or standard film versus digital imaging. The studies generally found a high level of agreement between retinal examination and imaging. Several studies suggested that retinal imaging through a dilated pupil was equivalent or superior to ophthalmic examination regarding the detection of diabetic retinal changes. Moss et al reported on an overall agreement of 85.7% when comparing retinopathy detection by ophthalmoscopy performed by skilled examiners to 7-standard field stereoscopic 30°fundus photography evaluated by trained graders. (6) A study by Kinyoun (7) found fair-to-good agreement between ophthalmoscopy and evaluating of 7-standard field stereoscopic 30°fundus photography by the examining ophthalmologist as well as by trained readers. Analysis of the discordance suggested that conventional ophthalmoscopy could miss up to 50% of microaneurysms, some of the earliest changes of diabetic retinopathy. (7) Delori et al reported more accurate visualization and documentation of the structures of the ocular fundus when using monochromatic illumination (red-free green light) as compared to the white light used to obtain color photographs. (8)

The efficacy of digital image acquisition, as compared to film-based acquisition, has been reported by several investigators. (9, 10) Fransen et al published the results of a comparison of standard evaluations using film to the same fields captured and transmitted as digital images. In the study of 290 adult diabetic patients, the sensitivity of digital compared to film was 98.2% and the specificity was 98.7%. Statistical analysis identified that the evaluation of film and digital images provided substantially equivalent results. (11) When comparing high-resolution stereoscopic digital fundus photography to contact lens biomicroscopy, Rudnisky et al found a high level of agreement regarding the detection of clinically significant macular edema in diabetic patients.(12)

In addition to the examination technique and the comparison of different photographic techniques, the results of dilated versus nonmydriatic fundus photography has been studied. (13, 14) Scanlon et al compared mydriatic and nonmydriatic photo screening programs using dilated slit lamp biomicroscopy as the reference standard. In the study of 3,611 patients, the sensitivity of mydriatic digital photography was 87.8%, the specificity was 86.1%, and the technical failure rate was 3.7%. Photography through an undilated pupil was found to provide a sensitivity of 86.0%, a specificity of 76.6%, and a technical failure rate of 19.7%. The authors concluded that while dilated digital photography is an effective method of screening for diabetic retinopathy, nonmydriatic photography has an unacceptable failure rate and low specificity. (15)

In summary, the published medical literature is adequate to conclude that digital imaging systems are safe and effective alternatives to the gold standards of dilated indirect ophthalmoscopy coupled with biomicroscopy or stereoscopic fundus photography. Additional advantages of digital imaging systems include short examination time, ability to perform without mydriasis, and the ability to perform the test in the primary care physician setting.

2005 Update

A literature search based on the MEDLINE database performed for the period of 2004 through June 2005 did not identify any additional published articles that would prompt reconsideration of the policy statement, which remains unchanged. Studies continue to report that digital imaging systems are an acceptable alternative to a dilated fundus examination for the evaluation of diabetic retinopathy, and are adaptable for use in the primary care physicians’ office. (16, 17) No further review is scheduled for this technology.

References:

Index

Policy History

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