not licensed eye care provider to adequately detect a level of retinopathy requiring referral [11]. This revealed 100% agreement for detection of referable diabetic retinopathy between a trained and certified reader and a retina specialist. Overall agreement between the reader and retina specialist for referral versus no referral was 93% with all cases of disagreement due to abnormalities other than diabetic retinopathy. As a result of these findings, we increased our training of readers to include identification of other common retinal abnormalities such as age-related macular degeneration and other retinal vascular disease.

seen as soon as practical and ideally within 1 week) to an ophthalmologist in the presence of disease felt to be vision threatening including neovascularization of the disc or elsewhere, preretinal hemorrhage, vitreous hemorrhage, and macular exudates suggesting macular edema. Patients with other suspected ocular diseases such as age-related macular degeneration, venous occlusive disease, or disc findings suspicious for glaucoma are also referred urgently or nonurgently depending on the severity of the findings.

11.4.2Criteria for Referral

to an Ophthalmologist

For the DigiScope® diabetic retinopathy surveillance system, relatively stringent referral criteria are in place as we feel any patient with more than mild diabetic eye disease should be under the care of an ophthalmologist. Patients are referred to an ophthalmologist in the presence of any level of retinopathy greater than mild nonproliferative disease based on the proposed International Classification of Clinical Diabetic Retinopathy and Macular Edema Severity Scale [12]. Patients may therefore be referred even if retinopathy has not yet reached a level requiring treatment. Patients are either reimaged if initial fundus images could not be obtained or are automatically referred if the images are unreadable due to a presumed physiologic cause. Patients are urgently referred (recommendation that patient is

11.5Detection of Macular Edema

Because the DigiScope® images are not reviewed stereoscopically, there may be a concern that patients with macular edema may not be detected with this imaging modality. With our system, any patient noted to have hard exudates in the central macular field, or within one disc diameter of the center of the macula, is identified as having a “marker for macular edema,” and urgent referral for possible vision-threatening pathology is recommended (Fig. 11.4). Based on a screening approach described by Bresnick and collaborators [1], such criteria have a sensitivity of 94% for detection of clinically significant macular edema. Additionally, since clinically significant macular edema is likely to be accompanied by other lesions of diabetic retinopathy that will trigger referral with the DigiScope® system, one can expect that very few cases of macular edema will be missed using this imaging modality and our referral criteria.

Fig. 11.4 DigiScope® image of a patient with “markers for macular edema” exemplified by hard exudates (yellow circles). Additionally, the red circles mark microaneu-

rysms and intraretinal hemorrhages while the green circles mark a laser lesion

11.6Implementation

To date, the DigiScope® system has been implemented in more than 400 primary care offices. The system is being utilized in more than 25 states, the District of Columbia, Bermuda, and the island nation of Palau. Through the end of 2009, a total of 101,773 patient encounters were completed using the DigiScope® technology. Regular referral was recommended for 17% of patients, while urgent referral was recommended for 3% of encounters. Including both unreadable images and those encounters when it was not possible to obtain images from one or both eyes for various technical reasons, the overall rate of unreadable images was 12%. Reassessment in 6 or 12 months was the recommendation for 68% of patient encounters indicating that the majority of patients imaged with this technology had mild or no diabetic retinopathy.

A study looking at a more detailed breakdown of patients imaged with the DigiScope® over a 6-month period (2,771 encounters) was performed

[13]. The age ranged from 20 to 93 years with a mean of 60 years. The age distribution in this cohort was comparable to that of the adult diabetic population. The rate of referral for diabetic retinopathy was 20% which is similar to other studies (10–19%) [14–16]. As expected, the abnormality leading to referral in this cohort was overwhelmingly diabetic retinopathy (87%). In the absence of diabetic retinopathy requiring referral, 21% of referrals were for findings suggestive of age-related macular degeneration. Other abnormalities found included disc appearance suggestive of glaucoma, myopic degeneration, and miscellaneous retinal vascular disease. Although additional studies are required to validate referrals for nondiabetic abnormalities with this system, these referrals are likely justified since they are based on unequivocal findings such as drusen and optic-disc appearance. Pilot studies have shown that the DigiScope® may be useful for screening for macular degeneration (Fig. 11.5) and optic nerve findings suggestive of glaucoma [17, 18].