Biomedical subjects
Publications and source records attributed to P Erickson.
This 44-year-old patient showed a distinctive bilateral pigmentary lesion of the macula which led to the tentative diagnosis, butterfly-shaped pigment dystrophy of the fovea. This is an extremely rare condition, with only a handful of cases reported in the literature. The disease is described, along with the rationale used in making the diagnosis.
Calculation of total refractive astigmatism by analyzing refractive parameters of the individual components can be very tedious, especially when the principal meridians among all the components are not orthogonal. A straightforward programming algorithm for accomplishing these calculations is presented. The algorithm is applicable to any programmable device which performs trigonometric functions.
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Changes in refractive status induced by contact lenses have been attributed to changes in various intraocular comonents. Limitation of previous mathematical attempts to quantify the effects of changes in these components are discussed. A series of simple ray-tracing equations is developed which avoids these limitations and provides a practical means of relating calculations to clinical measurements.
We analyzed data from 4 orthokeratology studies of refractive error change (deltaRE) and keratometer-reading change (deltaK). Instead of the reported deltaRE/deltaK ratio of 2:1, we calculated from linear-regression analysis a ratio (slope) of 2:3. The ordinate intercept of the straight line fitted to the data (N = 181 eyes) indicates that when deltaK = 0, deltaRE = 0.72. The correlation between deltaK and deltaRE is poor (+0.63). Causes and interpretations of these results are discussed.
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The reaction of the populations of two villages in Ponape District to PPD-Battey and to two tuberculin tests of different strengths was analyzed. The average annual incidence of infection in one village was estimated to be between seven and nine per cent per year; in the other village the incidence of infection was less than one per cent. Why these infection rates in the two villages were so different is not clear, but it is felt that the identification of the causative factor(s) may be considerable significance to the formulation of tuberculosis control policies in the district.
BACKGROUND: A substantial number of patients who elect to undergo photorefractive keratectomy do so without the motivation of occupational uncorrected vision requirements. We hypothesized that information processing preferences for the auditory (versus visual) modality in a global, associative (versus detailed, sensory-oriented) style with adaptability and risk-taking (versus predictability) personality characteristics would predominate in patients electing photorefractive keratectomy. METHOD: Seventy-three prospective photorefractive keratectomy patients attended informational sessions. Sixteen occupationally driven patients and one refusal were excluded from the analysis. The 27 patients electing to proceed with surgery were compared with the 29 declining surgery. Personality characteristics and cognitive styles were determined by the Myers-Briggs Type Indicator: Abbreviated Version and the Modality Strengths Indicator. RESULTS: Subjects electing surgery showed significantly greater preferences for processing information in the auditory modality and in a global, associative style, with adaptability and risk-taking personality characteristics. Combining the attributes statistically differentiated the two groups. CONCLUSIONS: Specific cognitive styles and personality characteristics strongly influence the choice to pursue photorefractive keratectomy when that choice is not occupationally driven.
We investigated the relationship between ocular dominance and monovision visual performance in 15 presbyopic subjects. Ocular dominance was determined using sighting (hole-in-the-card and mirror tests) and sensory (anisometropic blur suppression test) methods. Correcting the dominant sighting eye for a given viewing distance was found to be an unreliable method of optimizing blur suppression or binocular high/low contrast visual acuity at that distance. If there is any advantage to a particular strategy for selecting the distance monovision eye, it must be realized in vision performance areas other than visual acuity.
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A review of the literature is presented to discuss anterior tooth trauma in the primary dentition. Studies show that the incidence ranges from 4 percent to 30 percent and varies depending upon the sex and age of the child. Classification of the type of trauma is subdivided into trauma to the tooth and trauma to the periodontium. Treatment modalities depend upon various factors and range from nontreatment to splinting to extraction. Possible sequelae of primary tooth trauma may include tooth discoloration, loss of vitality, root resorption and/or abscess formation. Careful follow-up is recommended following any type of trauma, because the ultimate goal in treatment is to prevent damage to the permanent successor.
This study investigated the epidemiology, sequelae, and prognosis of subluxation injuries to the maxillary primary anterior dentition. Data were collected from dental records at the Montreal Children's Hospital, Montreal, Canada, of patients sustaining trauma between 1982 and 1993. The study group consisted of 207 teeth in 134 patients, 81 males and 53 females. The age of the patients ranged from 0.8 years to 7.5 years, with a mean of 3.5 years. The highest incidence of trauma was in males between the ages of 3 and 4 years, and in females between 1 and 3 years. The highest incidence of trauma (66.2%) involved the primary central incisors. The most common cause of trauma (52%) was simple falls indoors. Occlusal or periapical radiographs were the radiographic view of choice unless an anterior nasal spine fracture was suspected, in which case a lateral projection was exposed. Approximately 64% of the study teeth had a mobility ranging from 0.6 to 1.5 mm. Treatment varied from no treatment (80% of teeth) to extraction. Post-traumatic evaluations were distributed into six common time intervals used by dentists for follow up. The results indicated that patient discomfort and occlusal interference were not common. Discoloration and pulpal calcification increased with time. Mobility decreased with time, with the majority of teeth returning to a normal physiologic range. External resorption may have been present, but was rare. Treatment or antibiotics were rarely needed at follow-up visits. Overall, these teeth responded positively, and there was a low morbidity associated with subluxation injuries.