Preventive eye care in people with diabetes is cost-saving to the federal government. Implications for health-care reform

OBJECTIVE

Diabetic retinopathy, which leads to macular edema and retinal neovascularization, is the leading cause of blindness among working-age Americans. Previous research has demonstrated significant cost savings associated with detection of eye disease in Americans with type I diabetes. However, detection and treatment of eye disease among those with type II diabetes was previously thought not to be cost-saving. Our purpose was to estimate the current and potential federal savings resulting from the screening and treatment of retinopathy in patients with type II diabetes, based on recently available data concerning efficacy of treating both macular edema and neovascularization along with new data on federal budgetary costs of blindness.

RESEARCH DESIGN AND METHODS

We used computer modeling, incorporating data from population-based epidemiological studies and multicenter clinical trials. Monte Carlo simulation was used, combined with sensitivity analysis and present value analysis of cost savings.

RESULTS

Screening and treatment for eye disease in patients with type II diabetes generates annual savings of $247.9 million to the federal budget and 53,986 person-years of sight, even at current suboptimal (60%) levels of care. If all patients with type II diabetes receive recommended care, the predicted net savings (discounted at 5%) exceeds $472.1 million and 94,304 person-years of sight. Nearly all savings are associated with detection and treatment of diabetic macular edema. Enrolling each additional person with type II diabetes into currently recommended ophthalmological care results in an average net savings of $975/person, even if all costs of care are borne by the federal government.

CONCLUSIONS

Our analysis indicates that prevention programs aimed at improving eye care for patients with diabetes not only reduce needless vision loss but also will provide a financial return on the investment of public funds.

Relative letter and position difficulty on visual acuity charts from the Early Treatment Diabetic Retinopathy Study

Ten Sloan letters were used in the visual acuity charts developed for use in the Early Treatment Diabetic Retinopathy Study. We used the data from the 3,710 Early Treatment Diabetic Retinopathy Study subjects to investigate the relative difficulty of the ten Sloan letters and to evaluate whether the position of a letter on a line affected its relative difficulty. In general, our findings were consistent with those of the previous study. The four letters with curved contours (C, O, S, and D) were more difficult to discern at threshold than the six letters (Z, N, H, V, R, and K) composed of straight lines. Our data demonstrate that under these test conditions, letters at the end of a line are more likely to be read incorrectly than letters at the beginning of the line. This finding indicates that these data are probably not useful for evaluating possible crowding phenomena.

Issues in management of diabetic retinopathy

Panretinal photocoagulation could prevent most blindness from proliferative disease--if risk is identified early. This makes it essential that primary physicians include annual ophthalmologic evaluation in the management of patients at risk. Meanwhile, studies are under way on promising medical approaches, including intensive insulin regimens, aldose reductase blockers, and angiogenesis inhibitors.

Diabetic retinopathy

OBJECTIVE

To review the natural history and treatment indications for diabetic retinopathy.

RESEARCH DESIGN AND METHODS

Studies of the natural history of diabetic retinopathy and major clinical trials sponsored by the National Eye Institute were reviewed.

RESULTS

Diabetic retinopathy remains a leading cause of vision disability in the U.S. Vision loss results from the consequences of proliferative retinopathy or macular edema. Photocoagulation has been demonstrated to be an effective treatment for these complications of diabetes.

CONCLUSIONS

All people with diabetes should be evaluated regularly to determine whether they would benefit from photocoagulation. As a referral guideline, any person with type I diabetes of > 5 yr duration and all people with type II diabetes or any retinopathy should be referred to an ophthalmologist.

Pars plana vitrectomy in the Early Treatment Diabetic Retinopathy Study. ETDRS report number 17. The Early Treatment Diabetic Retinopathy Study Research Group

BACKGROUND

The Early Treatment Diabetic Retinopathy Study (ETDRS) enrolled 3711 patients with mild-to-severe nonproliferative or early proliferative diabetic retinopathy in both eyes. Patients were randomly assigned to aspirin 650 mg/day or placebo. One eye of each patient was assigned randomly to early photocoagulation and the other to deferral of photocoagulation. Follow-up examinations were scheduled at least every 4 months, and photocoagulation was initiated in eyes assigned to deferral as soon as high-risk proliferative retinopathy was detected. Aspirin was not found to have an effect on retinopathy progression or rates of vitreous hemorrhage. The risk of a combined end point, severe visual loss or vitrectomy, was low in eyes assigned to deferral (6% at 5 years) and was reduced by early photocoagulation (4% at 5 years). Vitrectomy was carried out in 208 patients during the 9 years of the study. This report presents baseline and previtrectomy characteristics and visual outcome in these patients.

METHODS

Information collected at baseline and during follow-up as part of the ETDRS protocol was supplemented by review of clinic charts for visual acuity and ocular status immediately before vitrectomy.

RESULTS

Vitrectomy was performed in 208 (5.6%) of the 3711 patients (243 eyes) enrolled in the ETDRS. The 5-year vitrectomy rates for eyes grouped by their initial photocoagulation assignment were as follows: 2.1% in the early full scatter photocoagulation group, 2.5% in the early mild scatter group, and 4.0% in the deferral group. The 5-year rates of vitrectomy (in one or both eyes) were 5.4% in patients assigned to aspirin and 5.2% in patients assigned to a placebo. The indications for vitrectomy were either vitreous hemorrhage (53.9%) or retinal detachment with or without vitreous hemorrhage (46.1%). Before vitrectomy, visual acuity was 5/200 or worse in 66.7% of eyes and better than 20/100 in 6.2%. One year after vitrectomy, the visual acuity was 20/100 or better in 47.6% of eyes, including 24.0% with visual acuity of 20/40 or better.

CONCLUSIONS

With frequent follow-up examinations and timely scatter (panretinal) photocoagulation, the 5-year cumulative rate of pars plana vitrectomy in ETDRS patients was 5.3%. Aspirin use did not influence the rate of vitrectomy.

Assessing the costs and benefits of medical research: the diabetic retinopathy study

Significant amounts of scarce resources are devoted to medical research, but there have been few attempts to assess whether the benefits to society of these investments exceed the costs. A method for undertaking such an assessment has been developed and applied retrospectively to the Diabetic Retinopathy Study, a major clinical trial funded by the National Eye Institute from 1972-1981. It was estimated that the trial, which cost $10.5 million, generated a net saving of $2816 million to society ($231 million when the costs of lost production are excluded) (1982 prices) and a gain to patients of 279,000 vision years. This approach could be applied prospectively in considering priorities for medical research, in conjunction with traditional criteria such as the scientific merit of the proposal and the capabilities of the investigators. The key factors affecting the economic returns from medical research are the prevalence, incidence and economic burden of the disease in question, the costs and effectiveness of the medical intervention concerned, the likely impact of the clinical trial on clinical practice and the likely timespan of benefits from knowledge obtained during the trial.

Aspirin effects on the development of cataracts in patients with diabetes mellitus. Early treatment diabetic retinopathy study report 16

The Early Treatment Diabetic Retinopathy Study, a randomized clinical trial supported by the National Eye Institute, was designed to assess the effect of photocoagulation and aspirin in 3711 patients with mild to severe nonproliferative or early proliferative diabetic retinopathy. Although the primary goal of the study was to evaluate the effect of photocoagulation and aspirin on diabetic retinopathy, the study also provided an opportunity to evaluate the effects of aspirin on the development of cataract. No evidence showed that aspirin use reduced the risk of development of cataract requiring extraction (4.1% vs 4.3% in patients assigned to aspirin or placebo treatment, respectively; Mantel-Cox P = .77; relative risk, 1.05; 99% confidence interval, 0.73 to 1.51). Aspirin use also did not reduce the risk of less extensive but visually significant lens opacities developing (29.6% vs 28.3%; Mantel-Cox P = .76; relative risk, 0.99; 99% confidence interval, 0.85 to 1.15). Early Treatment Diabetic Retinopathy Study results do not support the hypothesis that aspirin (at a dose of 650 mg/d) reduces the risk of cataract development in this diabetic population.

Factors associated with visual outcome after photocoagulation for diabetic retinopathy. Diabetic Retinopathy Study Report #13

Six risk factors for severe visual loss despite panretinal (scatter) photocoagulation were identified by analyzing data collected during the first 5 years after randomization in the Diabetic Retinopathy Study. Proportional hazards regression revealed NVD (neovascularization on/around the optic disc) to be the most important risk factor. The risk of severe visual loss rose with increasing NVD, hemorrhages/microaneurysms, retinal elevation, proteinuria, and hyperglycemia and fell with increasing "treatment density." These results are similar to previous DRS findings on untreated eyes. The importance of "treatment density" as an independent predictor of visual outcome is a new finding and lends support to the common clinical practice of repeating photocoagulation if initial treatment does not reduce or stabilize retinal neovascularization.

Krypton laser for proliferative diabetic retinopathy: the Krypton Argon Regression of Neovascularization Study

The Krypton Argon Regression of Neovascularization Study (KARNS) is a multicenter, randomized, controlled clinical trial designed to determine the efficacy of red krypton laser photocoagulation in the treatment of proliferative diabetic retinopathy.

Transient severe visual loss after panretinal photocoagulation

Seven diabetic patients experienced severe but transient visual loss after panretinal photocoagulation for proliferative diabetic retinopathy. In all patients, visual acuity decreased shortly after treatment to levels ranging from 5/200 to no light perception. In five of the patients, no observable ocular disease or surgical complications could explain the degree of visual loss. The other two patients developed exudative macular detachments, although it was not clear that this change accounted for their severe visual loss. Vision improved in all patients over a period ranging from nine days to nine months. In five patients, visual acuity returned to within two Snellen lines of the pretreatment level.

The early treatment of diabetic retinopathy

Advances in the understanding of diabetic retinopathy have allowed the development ofnew treatments directed at the preservation of sight. Recent data compiled by the Early Treatment Diabetic Reti nopathy Study (ETDRS) show that focal photocoagulation therapy can reduce the risk of further vision loss in diabetic patients with clinically significant macular edema. Therefore, treatment should be considered for all eyes that meet the criteria of clinically significant macular edema.

Optic disk neovascularization and retinal vessel diameter in diabetic retinopathy

We measured retinal vessel diameter before and after panretinal photocoagulation in 59 eyes with diabetic retinopathy and moderate to severe optic disk neovascularization. Treatment significantly reduced mean arteriolar and venular diameter. The diameter of the retinal arterioles after treatment correlated significantly with the amount of regression in disk neovascularization. Eyes with large diameter vessels after treatment usually had little or no regression of proliferative retinopathy, whereas regression was more frequently seen in eyes with smaller diameter vessels after treatment.

Diabetic retinopathy and cardiovascular disease in type II diabetics. The Framingham Heart Study and the Framingham Eye Study

Data from the Framingham Heart Study and the Framingham Eye Study were used to examine the association between diabetic retinopathy and the occurrence of cardiovascular events (coronary heart disease, intermittent claudication, congestive heart failure, and stroke). Among the 206 persons with Type II diabetes in the Framingham Eye Study, the odds ratios for diabetic retinopathy and cardiovascular disease were 14.3 (95% confidence interval (CI) = 2.7-101.9), 2.0 (95% CI = 0.5-8.1), and 0.3 (95% CI = 0.05-1.3) for ages 52-64, 65-74, and 75-85 years, respectively. The test for homogeneity indicated highly significant differences for the odds ratios across age groups. The associations were similar when sex, duration of diabetes, age at diagnosis of diabetes, and history of insulin treatment were accounted for by logistic regression. Our data suggest an association in younger diabetics between diabetic retinopathy, a small vessel complication of diabetes, and a group of cardiovascular events commonly thought to result from large vessel disease. The finding may merely indicate that diabetics with large vessel disease are also more likely to have small vessel disease. However, it is also consistent with the hypothesis, suggested by histologic data, that a more generalized microangiopathy affecting not only the eye but also organs such as the heart may play a role in the pathogenesis of cardiovascular disease in diabetics.

Macular thickening and visual acuity. Measurement in patients with cystoid macular edema

Cystoid macular edema (CME) is commonly associated with many ocular conditions. The presence of CME on fluorescein angiographic examination need not, however, preclude good visual acuity. The hypothesis that the degree of macular thickening is associated with visual acuity was tested. Ten consecutive stereoscopic fluorescein angiograms were graded by 13 ophthalmologists using a set of four standards. Linear regression showed a significant relationship between mean macular thickening and the visual acuity recorded at the time of angiography. However, no significant relationship could be made between the estimation of visual acuity and the amount of fluorescein staining measured in the posterior pole. Although the observation of fluorescein leakage is indispensable for documenting a breakdown in the blood-retinal barrier, the observation of retinal thickening is important for identifying the sites of edema accumulation, and may be the useful parameter to follow when trying to assess improvement or worsening of retinal edema and in cases of uveitis when the cause of poor vision may be multifactorial.

Macular edema in Diabetic Retinopathy Study patients. Diabetic Retinopathy Study Report Number 12

Results from the Diabetic Retinopathy Study (DRS) demonstrate that scatter photocoagulation is associated with some loss of visual acuity soon after treatment. This visual loss is especially prominent in eyes with preexisting macular edema. It is also associated with the intensity of treatment. Reducing macular edema by focal photocoagulation before initiating scatter treatment and dividing scatter treatment into multiple sessions with less intense burns may decrease the risk of the visual loss associated with photocoagulation.

Intraocular pressure following panretinal photocoagulation for diabetic retinopathy. Diabetic Retinopathy Report No. 11

Data collected during the first five years after randomization in the Diabetic Retinopathy Study were analyzed to determine the effect of panretinal photocoagulation on intraocular pressure (IOP). At each follow-up visit, median IOP was identical for the treated and untreated eyes. Mean IOP rose slightly in each group. The proportion of untreated eyes with IOP above 30 mm Hg at two consecutive visits was twice that of the treated eyes (2% vs 1%). These data show that panretinal photocoagulation reduces the risk of subsequent intraocular hypertension, apparently by preventing the development of neovascular glaucoma.

Clinical measurement of saturation discrimination

In this paper, we describe how a circular reflective neutral-density wedge can be used to construct an apparatus which provides a relatively rapid procedure for the clinical measurement of saturation discrimination. Subsequent to an initial measurement of the patient's relative luminosity function, the patient need only turn a single control which varies the colorimetric purity of a test field which remains luminance matched to a white light reference field.

Comparability of ophthalmic diagnoses by clinical and Reading Center examiners in the Visual Acuity Impairment Survey Pilot Study

Technologic advances in ophthalmic equipment offer the possibility of replacing direct clinical examinations with Reading Center evaluations of data recorded in epidemiologic studies. Clinical and Reading Center examiners made independent ophthalmic diagnoses of 133 right and 132 left eyes of 138 adults in the Visual Acuity Impairment Survey Pilot Study, carried out in three US cities, Boston, Detroit, and Minneapolis, in August 1981-December 1982. The Reading Center diagnosed eye conditions using only photographic and visual field data collected at the time of the clinical examination. In the comparisons of clinical and Reading Center evaluations reported here, only eyes judged by the examiners to have pathology severe enough to reduce visual acuity to 6/9 or worse were classified as having pathology. (No visual acuity criterion was required for the diagnosis of glaucoma or diabetic retinopathy.) There was agreement in diagnostic assessments between clinical and Reading Center examiners in about 80% of eyes. The kappa statistic, which adjusts for chance agreement, was in the fair to good range: 0.60 for 133 right eyes and 0.62 for 132 left eyes. When the Reading Center examiners were provided with additional information on medical history, refractive error and best corrected visual acuity, the agreement between clinical and Reading Center assessments among the subset of eyes with 6/9 or worse vision again was in the fair to good range, with kappas of 0.61 for 45 right eyes and 0.68 for 48 left eyes. Inter-observer agreement between Reading Center examiners in diagnosing pathology was in the good to excellent range. Use of Reading Centers in future epidemiologic studies should be considered, but elimination of the clinical examinations is not recommended until modifications in the protocol described here have been made and shown to improve levels of agreement between clinical and Reading Center examiners.

Evaluation of medical data: role of clinical trials

Over the centuries, methods have been developed to evaluate diseases and their treatments. One systematic method is the case series, in which groups of patients are followed over time to estimate the likelihood of various disease outcomes, either with or without treatment. A more efficient method for assessing treatment effectiveness is the clinical trial. Both methods have been used for evaluating current treatments of macular diseases. the combination of case series and clinical trials has been used to advantage for many of these diseases. However, when one wants to be certain that a treatment is effective, there is no substitute for the clinical trial.

Age-related macular degeneration and blindness due to neovascular maculopathy

Age-related macular degeneration (AMD) is one of the four most common causes of blindness in the United States. Retinal manifestations of AMD can be categorized as either atrophic or neovascular/exudative. To the best of our knowledge, the proportion of patients legally blind due to the neovascular/exudative manifestations of this disease has not been previously reported. Data from two studies, the Framingham Eye Study and a large case-control study, demonstrate that the vast majority of patients with legal blindness due to AMD have the neovascular/exudative form of the disease. Seventy-nine percent of eyes legally blind due to AMD in the Framingham population and 90% of eyes legally blind due to AMD in the case-control study had neovascular/exudative retinopathy. This is in spite of the fact that neovascular/exudative retinopathy is a relatively infrequent complication of AMD.

Site visits in a multicenter ophthalmic clinical trial

Site visits were conducted to 19 clinical centers in a large multicenter ophthalmologic clinical trial, the Early Treatment Diabetic Retinopathy Study (ETDRS). The purpose of these site visits was to ensure the consistency of study procedures among clinics and to verify that these procedures were being carried out in accordance with the ETDRS Manual of Operations. The five major aspects of this quality control program are as follows: To monitor and review each clinical center's organization and procedures; To promote comparability of participating centers in all important aspects of the clinical trial; To gain more understanding about special problems facing individual clinical centers; To establish good rapport between the site visitor and clinic staff to aid future clinic monitoring; To promote and maintain enthusiasm for the study. The ETDRS clinical center site visits were conducted by using an observational approach. Presite visit preparations included the formation of a site visit agenda and the design of a site visit form, providing a guide for the site visitor, and a list of the topics that were to be reviewed at each center. Important concerns common to all site visits proved beneficial in the ETDRS.

Macular edema. A complication of diabetic retinopathy

Diabetic macular edema is the leading cause of decreased vision from diabetic retinopathy. This decreased vision is caused by an increase in extracellular fluid within the retina distorting the retinal architecture and frequently taking on a pattern of cystoid macular edema. This fluid accumulates within the retina because of the breakdown of the barriers within the retinal blood vessels and possibly the pigment epithelium. Diabetic macular edema tends to be a chronic disorder. Although spontaneous recovery is not an uncommon occurrence, over one-half of diabetics with macular edema will lose two or more lines of visual acuity within two years. The most promising treatment for diabetic macular edema has been photocoagulation. It is recommended that in all patients with diabetic macular edema attempts be made to normalize elevated blood glucose, decrease elevated blood pressure, and improve cardiac or renal status. Reduction of serum lipids by diet or pharmacologic means is an unproven treatment at this time. The Early Treatment Diabetic Retinopathy Study hopefully will provide more definitive information as to whether photocoagulation is effective in various subgroups of patients with diabetic macular edema.

Senile macular degeneration: review of epidemiologic features

Senile macular degeneration is a leading cause of visual loss in the United States, England, and probably many other industrialized countries. The clinical manifestations of this disease include: drusen, atrophy of the retinal pigment epithelium, serous detachment of the retinal pigment epithelium, subretinal neovascularization, and disciform scars. Standardized techniques for defining these manifestations of senile macular degeneration are necessary for epidemiologic study of this disease. Such standardization is facilitated by the use of fundus photographs. If a visual acuity deficit is included in the definition of senile macular degeneration, care must be taken to assure that senile macular degeneration is responsible for the decreased vision. The Framingham Eye Study provides the best senile macular degeneration prevalence data. The rapid increase in prevalence of senile macular degeneration after the fifth decade is demonstrated in this study and is consistent with other studies. In fact, increasing age has the strongest association with senile macular degeneration of any of the risk factors considered to date. Many other possible risk factors have been identified but further investigation is necessary to verify these associations.

Senile macular degeneration: a case-control study

Senile macular degeneration, although a leading cause of visual loss in the United States, remains a poorly understood disease. To assess the effects of host and environmental factors on this condition, a study of 228 cases and 237 controls matched by age and sex, who had visited any of 34 Baltimore ophthalmologists between September 1, 1978 and March 31, 1980, was conducted. Study participants were interviewed for past medical, residential, occupational, smoking and family histories, as well as social and demographic factors. Diagnoses were validated by means of fundus photographs. The 162 cases and 175 controls who met the study diagnostic criteria for cases and controls were included in the analysis. Statistically significant associations were demonstrated between senile macular degeneration and family history of macular disease (odds ratio (OR) = 2.9), chemical work exposures (OR = 4.2), blue or medium pigmented eyes (OR = 3.5), history of one or more cardiovascular diseases (OR = 1.7), decreased hand grip strength, and hyperopia. The risk of macular degeneration in cigarette smokers was significant for males only (OR = 2.6). The study results suggest that the development of macular degeneration is mainly influenced by familial, genetic, and personal characteristics, rather than by the few environmental factors studied. Additional studies are needed to further evaluate the role of environmental factors.

An ocular clinicopathologic correlative study of six patients from the Diabetic Retinopathy Study

The authors studied the eyes postmortem from six patients who were enrolled in the multicenter Diabetic Retinopathy Study and treated by photocoagulation. All were patients of the Wilmer Institute, The Johns Hopkins Hospital. Of these six patients, four had equal or better vision in the treated eye at their last visit. Two patients had worse vision, due primarily to cystoid macular edema. All but one patient had clinically significant field loss in the treated eye, and this correlated with the retinal damage induced by photocoagulation. This treatment produced local retinal and choroidal effects and did not alter the histopathologic appearance of the anterior segment of the eye.

New visual acuity charts for clinical research

Three new visual acuity charts facilitate quantitative use of visual acuity test results. The charts have high-contrast lettering on washable white polystyrene. Each line has five Sloan letters; the lines are of equal difficulty and there is a geometric progression in letter size from line to line. This provides a similar task for each line on the chart with the letter size being the only variable. Charts with different letter sequences are used for testing right and left eyes.