Louis A. Lobes

Contribution of Diabetes Duration Before Puberty to Development of Microvascular Complications in IDDM Subjects

The contribution of diabetes duration, both pre- and postpuberty, to the development of microvascular complications and mortality in diabetic subjects was investigated in three study populations from the Childrens Hospital of Pittsburgh Insulin-Dependent Diabetes Mellitus (IDDM) Registry. Life-table analyses by total and postpubertal IDDM duration were used to evaluate differences in the prevalence of microvascular complications and diabetes-related mortality in subjects diagnosed before and during puberty, as defined by an age at IDDM onset marker of 11 yr for girls and 12 yr for boys. The prevalence of retinopathy and overt nephropathy in 552 White adult diabetic subjects (population 1, mean IDDM duration 20.8 yr) was significantly greater in subjects diagnosed during puberty compared with those diagnosed before puberty. However, similar analyses by postpubertal duration showed no difference in microvascular complication prevalence between the two groups. These findings did not appear to be due to a confounding effect of age. Additional analyses of 239 adolescent diabetic subjects (population 2, mean duration 8.3 yr) revealed the same trend for the prevalence of retinopathy. Finally, results concerning the risk of diabetes-related mortality in a cohort of 1582 subjects (population 3, mean duration 12.9 yr) indicated that postpubertal duration of IDDM may be a more accurate determinant of the development of microvascular complications and diabetes-related mortality than total duration, and it is suggested that the contribution of the prepubertal years of diabetes to long-term prognosis may be minimal.

Micron: An Actively Stabilized Handheld Tool for Microsurgery

We describe the design and performance of a handheld actively stabilized tool to increase accuracy in microsurgery or other precision manipulation. It removes involuntary motion, such as tremor, by the actuation of the tip to counteract the effect of the undesired handle motion. The key components are a 3-degree-of-freedom (DOF) piezoelectric manipulator that has a 400-μm range of motion, 1-N force capability, and bandwidth over 100 Hz, and an optical position-measurement subsystem that acquires the tool pose with 4-μm resolution at 2000 samples/s. A control system using these components attenuates hand motion by at least 15 dB (a fivefold reduction). By the consideration of the effect of the frequency response of Micron on the human visual feedback loop, we have developed a filter that reduces unintentional motion, yet preserves the intuitive eye-hand coordination. We evaluated the effectiveness of Micron by measuring the accuracy of the human/machine system in three simple manipulation tasks. Handheld testing by three eye surgeons and three nonsurgeons showed a reduction in the position error of between 32% and 52%, depending on the error metric.

Progressive Retinopathy with Improved Control in Diabetic Dwarfism (Mauriac's Syndrome)

We report four children aged 11–18½ yr first seen 7–14 yr after the diagnosis of insulin-dependent diabetes. At presentation, all had marked short stature, two had hepatomegaly, and the older three had delayed adolescence. They had been severely underinsulinized. Initial funduscopy demonstrated only occasion microaneurysms in two children and a single intraretinal hemorrhage in another. The youngest was normal. Improved control required large increases in insulin dosage. Growth rate improved significantly and hepatomegaly regressed. Puberty progressed rapidly in two older patients with poor final height. Paradoxically, with improved control, retinopathy progressed rapidly with appearance of multiple microaneurysms, nerve fiber layer infarctions, intraretinal microangiopathic changes, hemorrhages, exudates, and macular edema in all the patients and severe proliferation changes in three. One child with proliferative retinopathy in both eyes developed vitreous hemorrhage and blindness in one eye. Two required panretinal photocoagulation with no further progression of their retinopathy. These rapidly progressive retinal changes remain unexplained. We advise caution when correcting metabolic derangements of diabetic patients who have been poorly controlled for a prolonged period.

Urban measles in the vaccine era: A clinical, epidemiologic, and serologic study

A measles epidemic, during which 130 children were hospitalized and six died, occurred in St. Louis City and County during 1970 to 1971. A survey revealed an attack rate of 8.5 per cent in unvaccinated children who had not had natural measles, a rate of 1.7 per cent in children vaccinated after one year of age, but 6.3 per cent for children immunized before age one year. Measles attack rates in vaccinees were independent of time elapsed since immunization. Serum from 8 of 15 children with modified measles had no reduction in acute measles hemagglutination-inhibiting antibody titer after treatment with 2-mercaptoethanol. Twelve children had “atypical measles-rd but six of them had received only live vaccine. Ten per cent of 248 immunized children had hemagglutination-inhibiting titers of

Human Leptospirosis from Immunized Dogs

Abstract Leptospira icterohaemorrhagiaewas isolated from the urine of a critically ill patient from suburban St. Louis. Additional cases among close contacts of the patient and the animal source of...

Proteinuria in children with insulin-dependent diabetes: relationship to duration of disease, metabolic control, and retinal changes.

The relationship of early retinal changes and subclinical proteinuria to duration and metabolic regulation of insulin-dependent diabetes was studied in 67 children. Retinopathy was found in 25 patients and occurred almost exclusively (96%) in those with duration of disease longer than five years. Glomerular filtration rate was normal or increased in all patients. Urinary excretion of beta 2-microglobulin, albumin, transferrin, and IgG was significantly increased in patients, as compared with controls, whereas serum concentrations of these proteins were generally normal. The mechanisms responsible for the hyperexcretion of both large and small proteins are unclear but probably involve both glomerular and tubular dysfunction. Increased urinary protein excretion occurred independently of duration of disease. Retinopathy but not microproteinuria was more common in patients with glycosylated hemoglobin greater than 11% and in those with duration of disease longer than five years. Although a significant association was found between retinopathy and the hyperexcretion of one or more of the large molecular weight proteins, the weight of the evidence suggests that these two sequelae of diabetes differ in their pathogenesis. Long-term follow-up of these patients may provide insight as to their risk of developing more serious retinopathy or nephropathy, and whether good glycemic control may protect against these complications of insulin-dependent diabetes.

Presumed Toxoplasmic Papillitis

Six patients with ocular toxoplasmosis are described whose only active site of inflammation was at the optic nervehead. These patients presented with severe papillitis, vitreous inflammation, and sector or nerve fiber bundle field defects. Because of the papillitis and the absence of other typical foci of retinitis to suggest toxoplasmosis in these patients, the initial diagnoses were usually incorrect. These cases are presented to familiarize ophthalmologists with this unusual cause of papillitis.

Treatment of endophthalmitis after cataract extraction.

Background: A series of 34 patients was prospectively treated for postoperative endophthalmitis according to a specific protocol. The data are from the pilot study performed before initiation of the Endophthalmitis Vitrectomy Study (EVS). Methods: Patients with bacterial endophthalmitis that developed within 6 weeks of cataract extraction received intravitreal amikacin and vancomycin, subconjunctival and topical antimicrobials and corticosteroids, and systemic corticosteroids. All patients had diagnostic samples removed from the aqueous and vitreous, with randomized assignment to immediate vitrectomy versus vitreous tap and treatment with or without intravenous antibiotics. Outcome was evaluated 3 and 9 months after treatment. Results: At the 9-month visit, visual acuity was 20/50 or better in 49% of all eyes, 20/200 or better in 79%, and 5/200 or better in 91%. Media clarity was such that a “20/40 or better view” of the retina was present in 71 % of patients at 3 months and in 97% at 9 months. Conclusion: This is one of the largest series of patients with postoperative endophthalmitis treated and evaluated under a prospective protocol and without selection bias. Each of the options used in this study to treat postoperative endophthalmitis may result in good visual results.

Semiautomated intraocular laser surgery using handheld instruments.

In laser retinal photocoagulation, hundreds of dot‐like burns are applied. We introduce a robot‐assisted technique to enhance the accuracy and reduce the tedium of the procedure.

Vision-Based Control of a Handheld Surgical Micromanipulator With Virtual Fixtures

Performing micromanipulation and delicate operations in submillimeter workspaces is difficult because of destabilizing tremor and imprecise targeting. Accurate micromanipulation is especially important for microsurgical procedures, such as vitreoretinal surgery, to maximize successful outcomes and minimize collateral damage. Robotic aid combined with filtering techniques that suppress tremor frequency bands increases performance; however, if knowledge of the operators goals is available, virtual fixtures have been shown to further improve performance. In this paper, we derive a virtual fixture framework for active handheld micromanipulators that is based on high-bandwidth position measurements rather than forces applied to a robot handle. For applicability in surgical environments, the fixtures are generated in real time from microscope video during the procedure. Additionally, we develop motion scaling behavior around virtual fixtures as a simple and direct extension to the proposed framework. We demonstrate that virtual fixtures significantly outperform tremor cancellation algorithms on a set of synthetic tracing tasks (p <; 0.05). In more medically relevant experiments of vein tracing and membrane peeling in eye phantoms, virtual fixtures can significantly reduce both positioning error and forces applied to tissue (p <; 0.05).