Karl J. Fritz

Metabolic Control in Diabetic Patients: Effect of Insulin-secretory Reserve (Measured by Plasma C-Peptide Levels) and Circulating Insulin Antibodies

We measured circulating hemoglobin A1 (HbA1) and fasting plasma C-peptide concentrations in 100 diabetic patients. Pancreatic insulin reserve showed a negative correlation with HbA1 concentrations in nonobese, insulin-treated patients but not in obese patients, whether they were treated with insulin, oral agent, or diet alone. Patients with fasting C-peptide concentrations above 0.1 pmol/ml had significantly better metabolic control than did those with lower values. Anti-insulin antibodies were measured in 37 patients. There was no correlation between metabolic control and the affinity constants or binding capacities of these antibodies.

Intraocular Lens Power Formulas

We have developed a FORTRAN digital computer program to evaluate intraocular lens power for any thin lens and combination of corneal curvature and axial length. Partial derivatives of the power with respect to cornea power, axial length, and lens position allow estimation of error in power of the lens. These derivatives are computed along with power of the lens for six far points which may be changed with the program running. The program is written for remote access so that an ordinary telephone and portable terminal provide the ability to compute lens power.

Congenital bilateral horizontal gaze palsy in a brother and sister.

A man of 21 years and his sister aged 20 years had congenital bilateral horizontal gaze palsy. Convergence was normal but the vestibulocephalic and oculocephalic reflexes were absent. Aplasia of the paramedian zone of the pontine tegmentum, on a familial basis, is postulated as the cause.

Hemoglobin A1 and diabetic retinopathy.

The levels of the minor hemoglobin A1 components were measured in a consecutive series of 102 diabetic patients who were extensively studied for signs of diabetic retinopathy. We found a statistically significant relationship between metabolic control, as reflected by the hemoglobin A1 level, and the severity of diabetic retinopathy in patients with diabetes diagnosed before 30 years of age (P less than or equal to .001). We did not demonstrate a significant correlation between metabolic control and the severity of retinopathy in patients with diabetes diagnosed after the age of 30 years. We found significantly more severe retinopathy among patients with longer duration of the disease, in men, in whites, in diabetics diagnosted before 30 years of age who were treated with lower insulin doses, and in obses patients with the onset of diabetes after the age of 30 years.

Medical Therapy of Metastatic Meningococcal Endophthalmitis

We treated a 15-year-old girl who had meningococcal meningitis and metastatic endophthalmitis with large doses of intravenously administered penicillin G. The patient promptly improved with this therapy, and the visual axis completely cleared during the subsequent five months.

Slit-Lamp Examination of the Bedridden Patient

Slit-lamp examination of bedridden patients is facilitated by using a stretcher with the patient lying prone and holding the head erect.

Visual evoked Response Anomalies in a Patient with Friedreich’s Ataxia

Steady state visual evoked responses were studied in a patient with the clinical diagnosis of Friedreich’s ataxia. Ophthalmologic examination revealed no anomalies including visual acuity of 6/6 in both eyes, full visual field in both eyes, normal screening color vision, absence of optic atrophy and absence of nystagmus. Steady state VER revealed a monocular moderately attenuated signal in the left eye at 12 and 16 Hz and a markedly attenuated signal at 20 and 25 Hz. This contrasted with a normal VER in the right eye. The patient died of cardiac failure secondary to cardiomyopathy associated with Friedreich’s ataxia. Autopsy examination of the brain revealed a number of structural changes. The spinal cord had the usual severe demyelination and axonal changes associated with Friedreich’s ataxia. Histologic examination of the optic nerves showed no abnormality in the right nerve but focal axonal swelling, and some evidence of demyelination in the left optic nerve.

Laser Generated Patterned Stimuli for Visual Evoked Responses

The coherent radiation produced by a laser may be used to produce a variety of interference patterns. These patterns may be projected on a screen or projected directly onto the retina. Several methods exist whereby these patterns may be changed rapidly. Use of changing laser generated interference patterns as a stimulus for visual evoked responses is described. Use for clinical evaluation of visual acuity in anesthetized, comatose or infantile patients or those unable to recognize a stable interference pattern is proposed.

Computer Processing of the Visual Evoked Response

One of the chief problems in making the visual evoked response (VER) a usable tool in the clinic and laboratory is the complex nature of the response itself. Signal averaging removes much noise but the remaining complex waveform requires further processing. We have studied three processing techniques which analyze the shape of the waveform as a whole. These are: projection of the waveform onto a vector space spanned by orthogonal functions; least squares fitting with non-linear functions of the parameters; and integration of the product of the waveform and a template function. These studies were motivated by our need for computer methods to characterize waveforms during the course of experiments.