Biomedical subjects
Publications and source records attributed to J D Trobe.
Quality control of manual visual field examination is impaired because the process is difficult to monitor, and because examiners have minimal formal training and supervision, and are subject to rapid turnover. Computer simulation can be used both to teach perimetry and to provide a reference standard against which performance may be measured.
Evaluation of 20 essential blepharospasm patients by using structured interview and psychological testing (MMPI, Rorschach) revealed characteristic pathological personality patterns in all cases. Recent losses or life change, marital conflict, and specific precipitating events were common. Test findings indicated unexpressed hostility, denial, and repression in a majority of women. Three of five men showed evidence of depression. This initial systematic investigation of psychological factors in blepharospasm supports the hypothesis that neurological and psychogenic factors may interact etiologically. The data suggest that personality, recent stress, and precipitating events warrant both clinical assessment and controlled research to determine the specificity and prevalence of these findings.
A review of 49 tumors compressing the intracranial optic nerve, optic chiasm, or optic tract revealed that the majority of patients had symptoms and signs of visual loss predominantly affecting one eye. Seventy-seven per cent of patients had a relative afferent pupillary defect (RAPD), and 96% had a hemianopic defect in at least one eye. All patients had either a RAPD or a hemianopic defect. The junctional pattern of visual field defects was nearly as common (39%) as the classic bitemporal pattern (46%). Many fields contained a mixture of nerve fiber bundle and hemianopic defects; the hemianopias tended to obscure the coexisting nerve fiber bundle defects. Poor preoperative acuity predicted a relatively poor postoperative acuity, but 95% of the patients had 20/40 or better acuity in at least one eye after operation.
A patient who suffered traumatic hematomas of both occipitotemporal regions, but who had normal visual acuity, language, and cognitive functions, could not recognize faces of family members, celebrities , or recent acquaintances (prosopagnosia). He could distinguish same from different faces when they were presented simultaneously, but could not recognize faces that had been presented to him 90 seconds earlier. He could read and name objects correctly, but could not recognize any previously viewed object if it was reexamined later with other objects of the same semantic class. He had no difficulty copying complex figures, but synthesized incomplete visual information poorly and pursued an abnormal visual search strategy. We suggest that prosopagnosia is part of a more general inability to distinguish among objects within a visual semantic class. It results from impaired visual memory and perception caused by visual association cortex damage and interruption of the inferior longitudinal fasciculus connecting visual association cortex and temporal lobe.
Power spectral analysis (PSA) was performed on the visual evoked potentials (VEPs) to counterphased checkerboard stimuli from 98 eyes in 49 patients with multiple sclerosis (MS) and 54 eyes of 27 normal volunteers. Attenuation of high frequency components of the transient visual evoked potential was found in 53% of MS patients and 4% of controls. Loss of high frequency components was poorly correlated with prolonged latency (r = 0.346). The consideration of both PSA and latency of the VEP increased the percentage of MS patients exhibiting visual pathway conduction abnormalities from 61% to 86%. The use of PSA in the diagnosis of MS is useful in increasing detection especially in cases where deformed waveforms preclude a reliable estimation of latency.
The clinical dictum that pupil sparing in oculomotor nerve palsy predicts an extraaxial ischemic lesion while pupil involvement predicts an extraaxial compressive lesion has some important exceptions. Two case reports and a review of the literature disclose that pupil sparing occurs in a small proportion of intraaxial and compressive subarachnoid oculomotor nerve lesions and in a large proportion of compressive cavernous sinus oculomotor nerve lesions. Careful examination is also necessary to separate examples of apparent pupil sparing in cases of aberrant regeneration and in some instances of cavernous sinus compression.
A recent study that sampled the performance of nonphysician perimetrists in community ophthalmic practices revealed that the detection rate for any defect averaged only 69%. Nasal steps were correctly identified more often (77%) than were hemianopic defects (44%). If this relatively low identification rate for hemianopias is representative, then patients with unexplained visual loss should all have CT scans regardless of the result of the visual field examination. Greater accuracy in perimetry may be achieved by improved teaching, by optimizing exploration strategies, and perhaps by automated devices.
Interviews with 163 patients and the 19 ophthalmologists who examined them disclosed that patients considered an adequate explanation of diagnosis, treatment, and prognosis as the most important communication items in determining satisfaction with care. Ophthalmologists in private practice appeared to share this valuation, except that explaining the prognosis of an illness was not rated as highly. Resident ophthalmologists rated all explanatory items far less important than did their patients. Among items related to personalization of the encounter, ophthalmologists in private practice underrated the importance of dealing with the patient's concerns, while residents underrated familiarity, undivided attention, and encouragement. In spite of these differences, ophthalmologists apparently are sensitive to patient expectations, inasmuch as they received generally high ratings for their performance in each of the items that patients valued highly and poorer ratings for those items that were held less important.
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Forecasts of the requirements for and supply of ophthalmologists in 1990 have produced conflicting results because of varying assumptions about the future utilization of eye care services, incidence and prevalence of ophthalmic disease, physician productivity, and availability of residency training positions. A typical "utilization-based" models, founded on present consumer behavior, predicts a substantial 1990 surplus of ophthalmologists at current rates of residency training. Two "need-based" models, founded on ideal rather than actual use, reach different conclusions because of varying use of a fragile data base and the need to rely heavily on the subjective judgment of experts with regard to norms of care. The 1980 Graduate Medical Educational National Advisory Committee forecasted a surplus, while the 1978 American Academy of Ophthalmology predicted a deficit. Utilization-based models may slightly underestimate future ophthalmologist requirements. However, analysis of the factors that will influence future use suggests that need-based models are likely to overestimate the requirements. It is risky to accept the need-based model projections because of the high cost of a surplus, which include not only the expenses of training unneeded ophthalmologists but also the cost of their decreased exposure to disease and of declining physician morale, acumen, and thresholds for surgical procedures. Because free market mechanisms are ineffective in governing the supply of health providers, it will be necessary for the profession itself to review the current and projected supply and to set limits on the number of persons in training.
Formal monitoring of quality control in American graduate medical education is the task of the residency review committees (RRCs). The RRC for ophthalmology consists of nine members appointed by the American Board of Ophthalmology, the American Academy of Ophthalmology, and the American Medical Association. The RRC meets twice each year to determine the accreditation status of residency training programs. As of 1978, the residents ae board eligible only if they have graduated from accredited programs. The review process is based on data collected in standard hospital information forms and a site survey. An RRC member evaluates this information and makes a recommendation that is discussed and voted on by the nine-member RRC body. In response to pressures for greater quality control and regulatory visibility, the review process has been bolstered by improvements in the data-gathering forms and in the surveyors and by a revision of the minimum requirements for accreditation that provides clearer and more stringent guidelines.
Two patients with intracranial dissemination of squamous carcinoma along the trigeminal nerve had facial dysesthesias mistakenly diagnosed as tic douloureux. In one case, tumor originated in the skin of the lateral canthus and spread along an orbital nerve to involve the cavernous sinus and Gasserian ganglion. In the other, the primary site was the retromolar trigone, with preponderantly deep intraosseous growth. Perineural spread occurred along the inferior alveolar nerve to eventually involve the facial and the ocular motor nerves. Such neurotropic spread of tumors is unfamiliar to many clinicians, yet early diagnosis may be life-saving. If intracranial foramina have not been transgressed, surgery and radiotherapy have been curative; otherwise, treatment is largely palliative. Adequate initial treatment of the primary lesion would seem to be the best preventive measure. Treatment of recurrent lesions should include consideration of neural invasion.
We assessed the accuracy of ten ophthalmic technologist trainees (OTs) in commonly performed tasks of the ophthalmic examination. Results were derived from 224 patient examinations; 160 patients were examined both by OTs and ophthalmology residents, and an additional 64 were examined both by OTs, residents, and a faculty ophthalmologist. In measurement tasks, there was no significant difference in the results produced by the three types of providers. In identifying abnormalities of the globe and adnexae, and in history-taking, OT performance was nearly as accurate as that of the residents, when compared to the findings of the faculty ophthalmologist. In diagnosis and disposition, OT performance fell below the physician standard, especially in difficult cases. Patient acceptance of both formally trained and on-the-job trained ophthalmic medical assistants was very high. These results suggest that assistants with training comparable to that of the participants in this study may perform a large proportion of the routine ophthalmic examination without sacrificing quality or satisfaction with care.
A critical review of published ophthalmic histocompatibility antigen association studies found numerous conflicting or ambiguous reports. Methodologic errors that could account for these discrepancies were categorized into 3 groups (1) arbitrary application of statistical methods to determine significance, (2) poor sampling design, and (3) variable disease definition. Multivariate analysis, not previously applied in this area provides a more powerful tool for assessing statistical significance. A computer program using this methodology for large studies is now available.
A strategy that selectively explores the vertical fixational meridian of the visual field was as sensitive as conventional quantitative Goldmann perimetry in detecting chiasmal hemianopic field defects, although it required only one quarter of the usual testing time. A trained but "masked" perimetrist, applying this abbreviated method to the examination of 28 eyes with hemianopic defects, 17 eyes with nerve-fiber defects, and 14 normal eyes, detected 100% of the hemianopias when using the Goldmann perimeter, 92% when using the conventional tangent screen, and 87% when using the projection tangent screen. False-positive diagnoses of hemianopic defects were 16%, 11%, and 14% on the respective instruments. While this strategy did not define the field defects fully, it accurately identified the features of diagnostic importance. By its efficiency, this approach may encourage greater use of visual fields as a determinant in managing the conditions of patients with unexplained visual loss.
The accuracy of a variety of finger and color confrontation tests in identifying chiasmal and optic nerve visual field defects was assessed in patients whose field defects had been established beforehand by a conventional achromatic kinetic technique on the Goldmann perimeter. Kinetic and static finger confrontation methods identified an average of 42% of the 28 chiasmal hemianopic defects. False negatives included eyes with hemianopias complete to the largest (V4e) Goldmann isopter. False positives (average, 15%) occurred in eyes containing nerve fiber bundle defects with borders that fell near the vertical fixational meridian. Kinetic and static color confrontation techniques were 78.6% sensitive to hemianopias. Accuracy did not differ significantly whether the red target was presented kinetically or statically against the tangent screen, projected on the Autoplot screen, or held in the examiner's hand without attention to background. False positives (average, 23%) were slightly greater than with finger confrontation methods and occurred not only in eyes with nerve fiber bundle defects but also in eyes with no defects in reference visual fields. Finger confrontation identified 11% or fewer of optic nerve field defects, while some color techniques detected as many as 31 1/3%. There were no false positives.
Although its prevalence in dysthyroidism is estimated at less than 5%, optic neuropathy should be recognized as a preventable cause of disabling visual loss. Obscured by more obvious external congestive signs, it is usually insidiously progressive and bilateral, but may be acute and unilateral. Neuro-ophthalmic findings are nonspecific (prechiasmal field defects, normal or swollen nerveheads), and the diagnosis should be suspected in the context of typical adnexal changes of dysthyroidism. Optic nerve involvement is probably secondary to apical orbital compression by congested muscles. Treatment with oral corticosteroids, irradiation, or orbital decompression has been beneficial, especially in the early phases.
In the investigation of visual loss from anterior visual pathway disease, it is imperative to differentiate the infrequent compressive from the much more common noncompressive lesions. To determine how relatively low-cost, risk-free, but error-prone visual field examination (VF) and high-cost, risk-prone, but accurate CT Scan (CT) and cerebral angiography (Angio) can be cost-effectively utilized to solve this diagnostic problem, the authors have developed a decision making model for the analysis of three management strategies. The visual field examination precedes and determines the use of neuroradiologic studies in Strategy A (VF-CT-Angio), whereas it follows the neuroradiologic studies in Strategies B (CT-VF-Angio) and C (CT-Angio-VF). The visual field-determined strategy (A) proved most cost-effective, based upon an estimated 6% or lower relative prevalence of chiasmal compressive lesions, a negligible risk in delaying their diagnosis, and a sensitive method of visual field examination. At a visual field sensitivity to chiasmal defects of 84% and a specificity of 88%, Strategy A annually saves $4 million over Strategy B and $27 million over Strategy C. At lower levels of perimetric accuracy, Strategy B is the most cost-effective approach. Strategy C is never cost-effective.