Determination of the influence of effectivity upon residual astigmatism.

PURPOSE: A computing scheme is described which allows determination of the astigmatic contribution of ocular surface effectivity towards residual astigmatism. METHODS: This involves paraxial raytracing through astigmatic surfaces at random axes and applies the principle of astigmatic decomposition. Calculations are shown for averaged data from 66 normal right eyes. Frequency distribution graphs demonstrate individual variations. RESULTS: The averaged ratio of corneal thickness:anterior chamber:lens thickness cylinder power contributions due to effectivity (1:5:17) did not match the ratio of their respective intraocular distances (1:7:7); a disproportionate amount of astigmatism arose from lens thickness effectivity. Although previous research has revealed that results for individual eyes are prone to accummulative experimental errors, frequency distribution graphs indicate that effectivity predominantly yelds direct astigmatism (axis 180 degrees +/- 22.5 degrees). CONCLUSIONS: This computing scheme offers a means of examining the functional ocular morphology of astigmatic eyes.

Measurement of astigmatism arising from the internal ocular surfaces.

A method is described for measuring internal ocular surface (posterior cornea, anterior and posterior crystalline lens) astigmatism. This involves the use of videokeratography, A-scan ultrasonography, and autorefractometry along with multi-meridional phakometric measurements of Purkinje images I(anterior corneal surface) II(posterior corneal surface) and IV(posterior lens surface). Data was collected from both eyes of 66 subjects. Right and left eyes exhibited similar mean levels of astigmatism from the posterior corneal surface (R + 0.21 DC axis 82 degrees; L + 0.22 DC axis 80 degrees), anterior lens surface (R + 0.52 DC axis 8 degrees; L + 0.49 DC axis 165 degrees) and posterior lens surface (R + 1.48 DC axis 99 degrees; L + 1.16 DC axis 90 degrees). It was generally found that astigmatism arising from the anterior corneal and lens surfaces in conjunction with intraocular distance effectivity are almost completely compensated for by the posterior corneal and lens surface. Repeatability was assessed on 20 subjects. Although the methods is prone to accumulated experimental errors, these are random in nature so that the difference between repeat group averaged data never exceeded +/- 0.27 DC cylindrical component and +/- 6 degrees cylinder axis.

Hemolytic-uremic syndrome in asir region.

INTRODUCTION: Hemolytic-Uremic Syndrome (HUS) is a worldwide disease and a common cause of acute renal failure in childhood. Recently the number of cases in our area seems to be increasing. AIM: The objective of this study was to look at epidemiology, clinical course and complications of hemolytic-uremic syndrome in the Southern region of Saudi Arabia. METHOD: The medical records of 24 patients with typical post diarrhea HUS who were seen in Asir Central Hospital (ACH) between January 1989 and December 1994 were retrospectively reviewed. RESULTS: Of the 24 patients 15 were boys and 9 were girls with sex ratio 1.7:1. Ages ranged from 7 months to 11 years with a mean of 38 months. Clustering of cases were during spring and autumn time. Shigella dysenteriae was the most commonly isolated micro-organism, found in the stools of 5 patients. Complications occurred in 8 patients (33%) in the acute phase, 5 (21%) had generalized tonic-clonic seizures, while 2 (8%) had depressed level of consciousness. Three of the patients who had generalized seizures developed permanent cortical blindness. One patient developed chronic renal failure. One patient (4%) died in the acute phase after prolonged generalised seizure and coma. The mean age of the group with complications was 3335 months while it was 41:03 months in the uncomplicated group and mean platelets count was 46±40 × 10(9)/L and 58 ± 35 × 10(9)/L, respectively. CONCLUSION: Males seem to be more affected than females and Shigella was the most commonly isolated organism. Cortical blindness was relatively more common than in other studies and patients with complications were generally younger and had lower platelet count than those without complications.

A clinical trial of the SUN SK-2000 computer-assisted videokeratoscope.

A clinical trial was performed on 20 optometry students in order to evaluate the suitability of the SUN SK-2000 (SUN contact lens company, Japan) computer-assisted videokeratoscope for use in clinical practice. Suitability was assessed by observing three factors: the accuracy, repeatability and agreement for central mean corneal power (MCP) with a keratometer (Javal Schiotz). Measurements of eight peripheral points and the central radius of curvature were made on 20 optometry students and on an 8 mm calibration surface using the SUN SK-2000. The SUN SK-2000 accurately determined the 8 mm calibration surface (supplied by manufacturers) to be spherical (SD = +/- 0.013, P = 0.776). Careful alignment was found to be an important factor in determining the actual radius of the calibration sphere. Unfortunately, the system required measurements to be taken at a point which was not coincident with the line of sight. A simple improvement to this has been suggested. Readings were most repeatable for central corneal radii. Peripheral radii showed the most repeatability for the horizontal and inferior corneal radii. It has been suggested that the ocular adnexa may be a possible cause for the poor repeatability in the superior area of the cornea. The level of agreement between the Javal Schiotz keratometer and the SUN SK-2000 in terms of mean refractive error (MRE) was not found to be sufficient for the two instruments to be interchangeable (P = 0.011). The C0 and C45 components of corneal astigmatism were found to have little association with the keratometer.

A study of the axis of orientation of residual astigmatism.

The aim of this study was to determine the axis of orientation of residual astigmatism in a sample of human eyes applying the principle of astigmatic decomposition. Calculations were carried out on keratoscopic and refractive data collected from the right and left eyes of 70 subjects (37 male and 33 female students) of mixed race (including 25 Asians and 43 Caucasians). No statistically significant difference was found for mean levels of residual astigmatism measured in the right (0.46 DC x 98.2 degrees) and left (0.50 DC x 99.4 degrees) eyes. Residual astigmatism was predominantly against-the-rule (83% of right eyes and 66% of left eyes) and was within +/- 20 degrees of being perpendicularly disposed relative to the corneal astigmatic power axis in two thirds of the eyes measured. No statistically significant differences were found for either gender or race.

Immunoregulatory CD4+ CD45R+ suppressor/inducer T lymphocyte subsets and impaired cell-mediated immunity in patients with Down's syndrome.

The monoclonal antibodies 2H4 and 4B4 allow CD4+ and CD8+ T lymphocytes to be subdivided into CD45R+ and CDW29+ functional subpopulations. The CD4+ CD45R+ lymphocytes are designated as suppressor/inducer and CD4+ CDW29+ as helper/inducer subsets. Peripheral blood lymphocytes from 19 patients with Down's syndrome and 19 age- and sex-matched normal controls were analysed for the CD45R+ and CDW29+ subsets from the CD4+ and CD8+ T lymphocytes. The percentage of CD4+ CD45R+ cells (suppressor inducer) was markedly increased and of CD4+ CDW29+ cells (helper/inducer) decreased in all patients with Down's syndrome. In contract, the percentage of CD8+ CD45R+ and CD8+ CDW29+ subsets showed no major differences between patients with Down's syndrome and normal controls. Moreover, an alteration in the CD4+ and CD45R+ and CD4+ CDW29+ T cell subsets was accompanied by a markedly reduced proliferative response to phytohaemagglutinin and concanavalin A stimulation of the CD4+ T lymphocytes. Thus, a deficiency exists in patients with Down's syndrome in the CD4+ CDW29+ helper/inducer T cell subset which may contribute to their impaired cell-mediated immunity.

T-cell abnormalities in antibody deficiency syndromes.

We studied two patients with hypogammaglobulinaemia, three with selective IgA deficiency, and four with selective extreme IgM deficiency for T-cell abnormalities in the circulating blood. Most patients had altered CD4+ helper/inducer and CD8+ suppressor/cytotoxic T-cell subsets, and an elevated percentage of HLA-DR+ and interleukin 2 (IL-2) receptor+ antigens on lymphocytes. One patient with the selective IgA deficiency had an absence of CD4+ T cells in blood. The lymphocytes of eight patients showed a diminished proliferative response and deficient IL-2 production in response to stimulation with phytohaemagglutinin or concanavalin A. The three patients with selective IgM deficiency were found to have a defective T-cell abnormality in IgM synthesis by B cells. It is interesting that CD8+ T cells of the two patients with IgM deficiency demonstrated suppressor cell function for IgM synthesis by the normal B and T cells.

Diaphragmatic hernia in Down's syndrome.

Three Saudi children with Down's syndrome were found to have anterior diaphragmatic hernias. They all needed surgical correction. In Down's syndrome, besides congenital heart disease and recurrent chest infection, a diaphragmatic hernia should be looked for as a possible cause of respiratory distress and chest deformity.