Do Routine Eye Exams Reduce Occurrence of Blindness from Type 2
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JFP_09.04_CI_finalREV 8/25/04 2:22 PM Page 732 Clinical Inquiries F ROM T HE F AMILY P RACTICE I NQUIRIES N ETWORK Do routine eye exams reduce photography. Median follow-up was 3.5 years occurrence of blindness (range, 1–8.5 years). from type 2 diabetes? The patients were divided into cohorts based on level of demonstrated retinopathy. The mean screening interval for a 95% probability of remaining free of sight-threatening retinopathy ■ EVIDENCE-BASED ANSWER was calculated for each grade of baseline Screening eye exams for patients with type 2 retinopathy. Screening patients with no retino- diabetes can detect retinopathy early enough so pathy every 5 years provided a 95% probability of treatment can prevent vision loss. Patients with- remaining free of sight-threatening retinopathy. out diabetic retinopathy who are systematically Patients with background retinopathy must be screened by mydriatic retinal photography have a screened annually to achieve the same result, and 95% probability of remaining free of sight-threat- patients with mild preproliferative retinopathy ening retinopathy over the next 5 years. If back- need to be screened every 4 months (Table). ground or preproliferative retinopathy is found at A systematic review2 of multiple small English- screening (Figure), the 95% probability interval language studies evaluating screening and moni- for remaining free of sight-threatening retino- toring of diabetic retinopathy found consistent pathy is reduced to 12 and 4 months, respective- results. Screening by direct or indirect ophthal- ly (strength of recommendation [SOR]: B, based moscopy alone detected 65% of patients with on 1 prospective cohort study). A reliably sensitive screening exam requires mydriatic retinal photography augmented by What are Clinical Inquiries? ophthalmoscopy when photographs are inconclusive Clinical Inquiries answer real questions that family (SOR: A, based on a systematic review). For patients physicians submit to the Family Practice Inquiries Network with diabetes not differentiated by type, photocoagu- (FPIN), a national, not-for-profit consortium of family practice departments, residency programs, academic health sciences lation significantly decreases visual deterioration libraries, primary care practice-based research networks, and and reduces the chances of blindness (SOR: A, based other specialists. on randomized controlled trials [RCT]). Questions chosen for Clinical Inquiries are those that fam- ily physicians vote as most important through a web-based voting system. ■ EVIDENCE SUMMARY Answers are developed by a specific method: The Liverpool Diabetic Eye Study1 prospectively Type I answers • FPIN medical librarians conduct systematic and standardized evaluated the risk of vision-threatening retino- literature searches in collaboration with an FPIN clinician or pathy in a cohort that included all patients with clinicians. diabetes mellitus who were registered with a gen- • FPIN clinician authors select the research articles to include, critically appraise the research evidence, review eral practitioner and were not under the care of the authoritative sources, and write the answers. an ophthalmologist. A subgroup of 4770 patients • Each Clinical Inquiry is reviewed by 4 or more peers and with type 2 diabetes who did not have sight- editors before publication in JFP. threatening retinopathy at baseline underwent at • FPIN medical librarians coauthor Type I Clinical Inquiries that have required a systematic search. least 1 additional screen. Screening included non- • Finally, a practicing family physician writes an accompany- stereoscopic 3-field (45° or 50° field) mydriatic ing commentary. 732 SEPTEMBER 2004 / VOL 53, NO 9 · The Journal of Family Practice JFP_09.04_CI_finalREV 8/25/04 2:22 PM Page 733 CLINICAL INQUIRIES FIGURE Nonproliferative and proliferative diabetic retinopathy . AUGSBERGER, MD HTGAH BYPHOTOGRAPHY J JAMES Background (nonproliferative) diabetic retinopathy Proliferative diabetic retinopathy. Note the network is characterized by macular retinal exudates, edematous of abnormal preretinal new blood vessels just super- retinal thickening, dot and blot retinal hemorrhages, otemporal to the macula and the linear accumulations and retinal capillary microaneurysms. of blood in the preretinal vitreous below the macula. sight-threatening retinopathy. Screening by mydri- tiated by type of diabetes, were each treated in 1 atic retinal photography, augmented by ophthal- eye chosen at random with a xenon-arc photoco- moscopy when the photographs were inconclusive, agulator. Patients underwent follow-up treat- detected 88% to 100% of such cases. ments to the treated eye by clinical indication. An RCT of 1700 patients with diabetes and The untreated eyes were observed as controls. retinopathy evaluated preservation of vision with Blindness occurred significantly less often in the photocoagulation.3 Patients were not differentiat- treated eyes (19% total after 5 to 7 years) than in ed by type of diabetes. Each patient had initial the control eyes (39%; NNT=5 to prevent 1 blind and follow-up stereoscopic fundus photography. eye). Patients without proliferative retinopathy at One eye was selected at random to receive treat- onset experienced the most dramatic slowing of ment and the other remained untreated to serve deterioration; photocoagulation was more useful as a control. Because of the magnitude of differ- in maintaining than in improving vision. ence in vision between the eyes, the study was halted at 2 years to permit photocoagulation of ■ RECOMMENDATIONS FROM OTHERS the untreated eyes. Patients whose eyes had new The American Diabetes Association 2003 Clinical vessels on or near the disk lost vision (defined as Practice Recommendations5 state that patients visual acuity less than 5/200) more often in with type 2 diabetes should have an initial dilated untreated eyes (18.3% cumulative rate at 2 and comprehensive eye examination by an oph- years) compared with treated eyes (6.4%; num- thalmologist or optometrist shortly after diagno- ber needed to treat [NNT]=8.4). sis of diabetes. An ophthalmologist or optometrist Another RCT4 of patients with diabetes who is knowledgeable and experienced in diag- showed that photocoagulation maintained vision nosing diabetic retinopathy and is aware of its in diabetic retinopathy if the disease was not too management should repeat subsequent examina- advanced. Ninety-nine patients, also not differen- tions for both type 1 and type 2 diabetic patients SEPTEMBER 2004 / VOL 53, NO 9 · The Journal of Family Practice 733 JFP_09.04_CI_final 8/20/04 9:53 AM Page 734 CLINICAL INQUIRIES TABLE REFERENCES 1. Younis N, Broadbent DM, Vora JP, Harding SP. Incidence of sight-threatening retinopathy in patients with type 2 dia- Screening frequency betes in the Liverpool Diabetic Eye Study: a cohort study. for sight-threatening retinopathy Lancet 2003; 361:195–200. 2. Hutchinson A, McIntosh A, Peters J, et al. Effectiveness Stage of Screening of screening and monitoring tests for diabetic retinopa- thy—a systematic review. Diabet Med 2000; 17:495–506. retinal disease frequency* 3. The Diabetic Retinopathy Study Research Group. Preliminary report on effects of photocoagulation therapy. None 5 years Am J Ophthalmol 1976; 81:383–396. 4. British Multicentre Study Group. Photocoagulation from Background retinopathy 1 year diabetic maculopathy: a randomized controlled clinical trial using the xenon arc. Diabetes 1983: 32:1010–1016. 5. Fong DS, Aiello L, Gardner TW, et al. American Diabetes Mild preproliferative 4 months Association. Diabetic retinopathy. Diabetes Care 2004; 26 retinopathy Suppl 1:S84–S87. *For 95% chance of remaining free of sight-threatening retinopathy. What is the most effective diagnostic evaluation annually. Examinations are required more fre- of streptococcal pharyngitis? quently if retinopathy is progressing. Charles G. Tubbs, MD, Abraham Safeek, MD, Helen G. Mayo, MLS, University of Texas Southwestern ■ EVIDENCE-BASED ANSWER Medical Center, Dallas Standardized clinical decision rules, such as the Centor criteria, can identify patients with low ■ CLINICAL COMMENTARY likelihood of group A beta-hemolytic streptococ- Screen for retinal complications early, cal (GABHS) pharyngitis who require no further regularly, by an experienced eye doctor evaluation or antibiotics (strength of recommen- Family physicians play a central role in the dia- dation [SOR]: A, based on validated cohort stud- betes care team. They must not only achieve ies). For patients at intermediate and higher risk good blood sugar control, but also monitor for by clinical prediction rules, a positive rapid anti- complications and coordinate their treatment. gen detection (RAD) test is highly specific for Educating patients and reaching common GABHS (SOR: A, based on systematic reviews of ground with them is essential for success. diagnostic trials). Evidence suggests that screening for eye compli- A negative RAD test result, using the best cations reduces blindness. Patients with early technique, approaches the sensitivity of throat retinopathy changes are usually asymptomatic; culture (SOR: B, based on retrospective cohort therefore it takes a committed and educated studies). In children and populations with an patient to comply with screening recommenda- increased prevalence of GABHS and GABHS com- tions. Also, many patients have the misconcep- plications, adding a backup throat culture reduces tion that a visual acuity exam by an optometrist the risk of missing GABHS