Marie Carole Boucher

Effectiveness and safety of screening for diabetic retinopathy with two nonmydriatic digital images compared with the seven standard stereoscopic photographic fields.

BACKGROUND The use of nonmydriatic cameras, which offer ease of screening and 45 degrees immediate imaging of the fundus, is gaining increasing acceptance for screening programs tailored to diverse conditions. We performed a study to evaluate the effectiveness and safety of screening for diabetic retinopathy with two nonmydriatic camera images compared with the seven standard stereoscopic 30 degrees fields (7SF). We also wished to determine whether safe screening guidelines could be established to identify patients needing referral to an ophthalmologist. METHODS In this prospective masked cross-sectional study, we evaluated agreement in the assessment of the severity of diabetic retinopathy by means of two 45 degrees images centred on the optic disc and on the macula obtained with the Topcon CRW6 nonmydriatic camera and by means of 7SF photography and ophthalmologic slit-lamp biomicroscopy, both performed with pupil dilation. Between November 2000 and June 2001, 98 adult patients known to have type 1 or 2 diabetes mellitus who presented for the first time to the diabetic retinopathy clinic of a tertiary care centre in Montreal were enrolled consecutively. Thus, patient recruitment was weighted toward more severe retinopathy to ensure sufficient representation of less frequent but more severe levels. Each patient underwent nonmydriatic fundus photography of both eyes, followed by a complete ophthalmologic examination with pupil dilation by a single retina specialist and 7SF photography of both eyes with pupil dilation. The level of retinopathy was graded independently in each eye from the 7SF photographs according to the Early Treatment Diabetic Retinopathy Study (ETDRS) scale by two graders; an independent retina specialist adjudicated the rare instances of interreader disagreement in a masked fashion. Two months later, two graders independently graded the nonmydriatic images in a blinded fashion according to the ETDRS scale; a third observer adjudicated the rare instances of interreader disagreement. We measured concordance between grading results with the various screening techniques using the weighted and unweighted kappa statistic. We used sensitivity and specificity indices to determine safe screening guidelines to identify patients needing referral to an ophthalmologist. RESULTS There was substantial agreement in the grading of retinopathy with nonmydriatic camera imaging and with 7SF photography, both for all eyes (kappa = 0.626 [standard deviation (SD) 0.045]) and for the eye with more severe disease (kappa = 0.654 [SD 0.063]). With nonmydriatic camera imaging, screening thresholds for patient referral to an ophthalmologist of very mild retinopathy (ETDRS grade 20), mild retinopathy (ETDRS grade 35) and moderate retinopathy (EDTRS grade 43) had sensitivity values of 97.9%, 97.1% and 53.3% respectively and specificity values of 81.3%, 95.5% and 96.9% respectively. Screening thresholds of very mild or mild retinopathy both correctly identified 100% of eyes with severe nonproliferative or proliferative retinopathy. With a screening threshold of mild retinopathy, screening with the nonmydriatic camera would lead to referral to an ophthalmologist of 37.8% of patients because of detected disease and of an additional 17.3% because of insufficient image quality in at least one eye, for a total of 55.1%. The overall sensitivity and specificity of a two-field nonmydriatic screening strategy with a threshold of mild retinopathy for referral of patients with insufficient image quality in at least one eye are 97.7% and 84.0% respectively. INTERPRETATION Our results suggest that two-field nonmydriatic camera imaging is a safe screening strategy that may identify the patients with diabetes most in need of ophthalmologic care.

Procedure to detect anatomical structures in optical fundus images

We present an overview of the design and test of an image processing procedure for detecting all important anatomical structures in color fundus images. These structures are the optic disk, the macula and the retinal network. The algorithm proceeds through five main steps: (1) automatic mask generation using pixels value statistics and color threshold, (2) visual image quality assessment using histogram matching and Canny edge distribution modeling, (3) optic disk localization using pyramidal decomposition, Hausdorff-based template matching and confidence assignment, (4) macula localization using pyramidal decomposition and (5) bessel network tracking using recursive dual edge tracking and connectivity recovering. The procedure has been tested on a database of about 40 color fundus images acquired from a digital non-mydriatic fundus camera. The database is composed of images of various types (macula- and optic disk-centered) and of various visual quality (with or without abnormal bright or dark regions, blurred, etc).

Teleophthalmology screening for diabetic retinopathy through mobile imaging units within Canada

BACKGROUND This study aimed to describe and measure the health results of a Category 3 teleophthalmology screening project for diabetic retinopathy (DR). Implemented through mobile screening imaging units located within pharmacies, the project had the goal of reaching unscreened diabetic patients in urban communities while lowering barriers to screening and saving medical resources. METHODS Image capture of both eyes of 3505 known diabetic individuals was performed in the provinces of Quebec, British Columbia, Alberta, Manitoba, and Saskatchewan. A photographer performed fundus imaging, and a nurse used mild pupil dilation only when necessary to secure image quality. Screening was provided free of cost in the context of DR health days for DR screening. Through teleophthalmology, ophthalmologists proceeded with data and image interpretation, and timely referral when indicated. RESULTS This project allowed the resumption of screening of over 38% of the cohort of known diabetics who reported never having undergone any eye examination with pupil dilation, and an additional 30% who reported not having been examined for over 2 years. All known diabetics were under the care of a general physician, and their mean diabetes duration, when known, was 8 years. DR pathology was found in 22.5% (20%-28%) of the cohort, 1.8% requiring urgent referral (within 30 days) as a result of the severity of the DR and 0.6% (0%-1.8%) requiring urgent referral for other reasons. An additional 8.7% (8.1%-19.5%) required ophthalmologic attention within 6 months because of DR and another 2.0% (0%-6.3%) between 6 months and 1 year. Incidental findings were found in 23%, the majority of which were related to cataract and dry macular degeneration. Urgent or significant incidental findings were found in 0.6% of the screened eyes. Pupil dilation with tropicamide 1% was deemed useful or necessary in 33.7% of the cohort. For 0.7% of the cohort, the images could not be interpreted because of poor image quality and for that reason had to be referred for a traditional dilated eye examination. Ophthalmologists were relieved of the examination of 85.6% of the screened diabetic individuals who benefited from screening without requiring a traditional ophthalmologic examination. On the other hand, ophthalmologists were required to provide urgent (within 30 days) services to 2% of the cohort, either because of threatening DR or because of incidental findings requiring rapid ophthalmologic attention. INTERPRETATION This screening strategy for DR through mobile teleophthalmology imaging units efficiently lowered barriers to screening and created new screening opportunities for a large number of known diabetic individuals who were lost to the traditional health system. It has the potential to provide better outreach to diabetic populations while identifying individuals truly in need of the services of an ophthalmologist; at the same time it maximizes the use of limited ophthalmologic resources while favouring multidisciplinary collaborations. The significant incidental findings associated with screening highlight the need for ophthalmologic competencies during DR screening within a teleophthalmology approach. Further involvement of government health authorities is pivotal in embracing the opportunities provided by emerging technologies such as teleophthalmology and translating them into better outreach services to diabetic populations and thus better visual health results.

Comparison of two, three and four 45° image fields obtained with the Topcon CRW6 nonmydriatic camera for screening for diabetic retinopathy

BACKGROUND The use of the nonmydriatic camera is gaining increasing acceptance for the detection of diabetic retinopathy when integrated into a community-tailored program. We performed a study to evaluate the optimal number and positioning of photographic fields necessary to screen for diabetic retinopathy with the Topcon CRW6 nonmydriatic camera. METHODS In this prospective masked cross-sectional comparative study, we compared the assessment of diabetic retinopathy using two, three or four 45 degrees fundus images (centred respectively on the disc and the macula; on the disc, on the macula and temporal to the macula; and on the disc, on the macula, temporal to the macula and superotemporal to the macula, including the superior temporal vein) acquired with the Topcon CRW6 nonmydriatic camera, with the grading of the seven standard stereoscopic 30 degrees field photographs (7SF). The study population consisted of 98 consecutive adult patients known to have type 1 or 2 diabetes mellitus who presented for the first time to the diabetic retinopathy clinic of a tertiary care centre in Montreal. All patients underwent four nonmydriatic fundus photography sessions of both eyes, 7SF photography with pupil dilation and a complete ophthalmologic examination with pupil dilation by a retina specialist. RESULTS Compared to the 7SF, the sensitivity and specificity of screening for any retinopathy (Early Treatment Diabetic Retinopathy Study [ETDRS] grade greater than 10) using the two central fields were 95.7% and 78.1% respectively. The corresponding values with three image fields were 97.6% and 71.9%, and with four image fields, 97.6% and 65.6%. The sensitivity and specificity of screening for mild or worse disease (ETDRS grade 35 or greater) using the two central fields were 87.5% and 92.3%. The corresponding values with three image fields were 88.9% and 94.6%, and with four image fields, 88.9% and 91.9%. Poor image quality occurring with the addition of extra fields resulted in an increase of 6.2% in the rate of referral to an ophthalmologist. The use of two image fields missed no cases of retinopathy. INTERPRETATION The use of image fields in addition to the two 45 degrees images centred on the disc and the macula on imaging with the Topcon CRW6 nonmydriatic camera did not significantly increase the sensitivity or specificity of screening for diabetic retinopathy. Contrary to the desired effect, the addition of fields resulted in diminished utility and cost-effectiveness of this screening approach.

Canadian Ophthalmological Society evidence-based clinical practice guidelines for the management of diabetic retinopathy

The objective of this document is to provide guidance to Canadian ophthalmologists regarding screening and diagnosis of diabetic retinopathy (DR), management of diabetes as it pertains specifically to DR, and surgical and nonsurgical approaches to the treatment of DR. These guidelines apply to all Canadians with type 1 or type 2 diabetes of all ethnic origins. Other health professionals involved in the care of people with diabetes may find this document helpful. These guidelines were systematically developed and based on a thorough consideration of the medical literature and clinical experience. These guidelines are not meant or intended to restrict innovation. Guidelines are not intended to provide a “cookbook” approach to medicine or to be a replacement for clinical judgment; rather, they are intended to inform patterns of practice. Adherence to these guidelines will not necessarily produce successful outcomes in every case. Furthermore, these guidelines should not be used as a legal resource, as their general nature cannot provide individualized guidance for all patients in all circumstances. Guidelines are not intended to define or serve as a legal standard of medical care. Standards of medical care are specific to all the facts or circumstances involved in an individual case and can be subject to change as scientific knowledge and technology advance, and as practice patterns evolve. There is no expectation that these guidelines be applied in a research setting. No comment is made on the financial impact of procedures recommended in these guidelines. Ideally, guidelines are flexible tools that are based on the best available scientific evidence and clinical information, reflect the consensus of professionals in the field, and allow physicians to use their individual judgment in managing their patients. These guidelines

Contemporary Management of Diabetic Retinopathy in Canada: From Guidelines to Algorithm Guidance

Recent advances in the therapeutic options and approaches for diabetic retinopathy (DR) and diabetic macular edema (DME) have resulted in improved visual outcomes for many patients with diabetes. Yet, they have also created many clinical dilemmas for treating ophthalmologists and retina specialists, including treatment selection, initiation, frequency and duration. With this in mind, a panel of Canadian retina specialists met and discussed the current clinical evidence as well as specific situations and scenarios commonly encountered in daily practice. They also shared their experiences and therapeutic approaches. This document, containing a consensus on treatment algorithms for various clinical scenarios, is the result of their lengthy and in-depth discussions and considerations. The intent is to provide a step-by-step approach to the treatment of DR and DME. Although clinicians are encouraged to use and refer to these algorithms as a guide for various situations, they are not meant to be a replacement for sound clinical judgment.

Canadian Ophthalmological Society Evidence-based Clinical Practice Guidelines for the Management of Diabetic Retinopathy - executive summary.

The Canadian Ophthalmological Society Evidence-based Clinical Practice Guidelines for the Management of Diabetic Retinopathy were developed to provide guidance to Canadian ophthalmologists regarding the management of diabetic retinopathy (DR). Readers are directed to the full guideline document, available online at http://www. canadianjournalofophthalmology.ca/, for more detail and references.

Diabetic retinopathy screening

We would like to thank Greve and Tennant for their comments in the editorial accompanying our article in the December 2008 issue of the Candian Journal of Ophthalmology. Although diabetic retinopathy is a treatable eye disease, it remains a leading cause of blindness in industrialized countries. Despite efforts to educate both patients and physicians about the importance of routine diabetic screening and despite the publication of Canadian screening guidelines, a large percentage of the diabetic population continues to receive inadequate retinopathy screening. This has led to the search for strategies to better detect vision-threatening retinopathy and reduce the incidence of complications and blindness from diabetic retinopathy. Diabetic retinopathy is an important public health concern requiring targeted examinations to obtain improved vision outcomes. Although new developments in technology make comprehensive teleophthalmology possible, the best strategy for diabetic retinopathy may or may not require a comprehensive eye examination. A screening strategy specifically designed for diabetic retinopathy in a public health context may not need to provide a complete eye examination, just as screening for colon cancer does not entail a comprehensive gastrointestinal workup. Screening must be separated from diagnosis, treatment, and followup where a more sophisticated setup and technology are probably necessary. Screening for diabetic retinopathy addresses a very specific public health need and results in better awareness, education, and access to reliable screening. In addition, such a screening strategy for diabetic retinopathy is supported by international scientific literature. The screening strategy and methods used in our study are in accordance with published literature and public screening programs in other parts of the world, such as the U.K. Greve and Tennant have expressed some concern about using pharmacies as an entry point for a screening program, and suggest the use of family doctors and endocrinology offices as a more sustainable option, a strategy that has until now failed to reach diabetics efficiently. Our intent was not to dictate a single program for teleophthalmology diabetic retinopathy screening, but to demonstrate the significant health results that can be obtained when screening is provided for these patients with diabetes. The use of pharmacies as an entry point is only one possible solution to the problem of accessibility. Physicians are very effective at providing care to a captive patient population in a health care setting, but in order for a screening program to be beneficial, we need to target the population outside traditional medical settings. Different populations and regions may require different solutions, and we need to be creative in our outreach methods to maximize the general population’s exposure to timely screening. We believe that efforts to improve screening rates need to be multifaceted and that better access to rigorous, reliable, and timely screening services for diabetic retinopathy offers the best chance of preventing disease and preserving the vision of our diabetic population. We are adamant that government health authorities need to become more involved many external reviewers before it is ultimately reviewed and endorsed by the society itself. I am proud of the guidelines that the COS committee produced and am happy to praise them rather than bury them.