Comparison of refractive state and circumferential morphology of retina, choroid, and sclera in chick models of experimentally induced ametropia.

PURPOSE: Simultaneous comparisons of the circumferential morphological tissue profiles and final refractions from form-deprivation myopia (FDM), defocus-induced myopia (DIM), and defocus-induced hyperopia (DIH) models of ametropia have been made to test the hypothesis that changes in the thickness profiles of the three coats of the eye, and particularly that of the choroid, can be predicted from the degree of induced refractive error. METHODS: Hatchling chickens (n = 23) were raised for 2 weeks wearing either a monocular translucent diffuser (FDM, n = 8), monocular -10.00 D lens goggle (DIM, n = 7), monocular +10.00 D lens goggle (DIH, n = 7), or nothing (Norm, n = 1). All animals were refracted using retinoscopy and were then sacrificed, and whole eyes were processed for scanning electron microscopy. Retinal, choroidal, and cartilaginous sclera (CS) thickness measurements were made from photographic collages of the entire circumference of the globe. Of the 23 chickens, complete morphological profile data were available for both eyes of 10 animals (nine treated and one normal). The contralateral fellow eyes (FEyes) of all nine experimental chickens were used as experimental controls as paired comparisons for statistical analyses. RESULTS: Morphological profiles of control and experimental eyes revealed significant systematic regional variations in tissue thickness. This variation was related to nasal or temporal eccentricity with the nasal side generally thinner than the temporal. Retinal, choroidal, and CS tissue from FDM and DIM eyes showed very similar anatomical responses despite significantly different degrees of refractive change. DIH eyes showed significant increases in choroidal thickness but none in retinal or CS thickness. Analysis of fellow control eyes indicated that in both myopia models (FDM and DIM), significant changes in all tissues of the untreated fellow eyes occur whereas only the choroid of the fellow eye was affected in the hyperopic (DIH) model. CONCLUSIONS: The morphological similarity observed in the circumferential profiles of the retina, choroid, and cartilaginous sclera of the FDM and DIM eyes despite approximately 20 D difference in final refraction suggests that choroidal thickness is not a good predictor of final refractive error across models. Similarly, the final refractive difference of approximately 20 D between the DIM and the DIH eyes did not receive a major contribution from the final difference in choroidal thickness (with its implied effect on vitreous chamber length).

Varicella-zoster infection after allogeneic bone marrow transplantation: incidence, risk factors and prevention with low-dose aciclovir and ganciclovir.

We examined the incidence of herpes varicella-zoster virus (VZV) infection in 151 patients undergoing allogeneic BMT between August 1990 and September 1997 and who survived at least 3 months. Median follow-up was 17 (range 3.3-80.7) months. Herpes simplex virus antibody positive (HSV+) patients received aciclovir 1200 mg p.o. daily or 750 mg i.v. daily, in divided doses from day 0 to engraftment. Ganciclovir (5 mg/kg i.v. three times per week) was given in CMV+ patients (or if the donor was CMV+) from engraftment to day 84. Ganciclovir was continued or recommenced if a dose of greater than 20 mg of prednisone was used for the treatment of GVHD otherwise aciclovir was recommenced. In HSV+ patients not receiving ganciclovir, aciclovir 600 mg p.o. daily in divided doses was given until at least 6 months after BMT. Thirty-two patients developed VZV infection from 4.1 to 28 months after transplant. The estimated cumulative incidence of VZV was 13% (95% confidence interval 6-19%) at 12 months, 32% (22-42%) at 24 months and 38% (27-50%) at 28 months, with no further cases beyond that time. No patient developed VZV whilst receiving aciclovir or ganciclovir (P < 0.0001). However, there was a rapid onset of VZV following cessation of antiviral therapy (33% (20-46%) at 1 year post cessation). The presence of GVHD and the prior duration of antiviral prophylaxis were significant and independent risk factors for the development of VZV. Age, underlying disease, conditioning therapy or donor type were not. We conclude that 3-6 months of low-dose aciclovir and ganciclovir are effective at delaying the onset of VZV after allogeneic BMT, but may not affect the overall incidence of infection. Prolonged prophylaxis may be warranted in patients at high risk of infection, for example those patients with GVHD.

A technique for in vivo measurement of photoreceptor orientation in the chicken retina.

The aim of the current study was to develop a method for simultaneously assessing central and peripheral photoreceptor alignment in vivo in animal models. The stimulus apparatus consisted of nine light-emitting diodes (LED) positioned 7.5 degrees apart around an arc. The stimulus was viewed through a pinhole imaged into the entrance pupil of the eye using a telecentric lens system. Photodiodes placed over an array of the VERIS imaging system stimulated the electroretinogram. Data were obtained by positioning the pinhole at 0.25-mm intervals across the pupil and recording (Volk Optical, Mentor, OH, USA) at each location. Orientation assessed in normal chickens demonstrates that photoreceptors orientate towards a locus near the centre of the pupil and that there is a systematic change in peak location with eccentricity. This technique provides a valuable method for determining photoreceptor orientation properties in vivo and can be applied to animal models of pathology.

Increased survival in patients diagnosed with Hodgkin's disease in Tasmania, 1972-1992.

BACKGROUND: It has been shown that in certain populations the prognosis of Hodgkin's disease (HD) has improved markedly since the late 1960s. This has not been formally demonstrated in an Australian population. AIMS: To review all patients in Tasmania diagnosed with HD between 1972 and 1992, and to ascertain whether variation in survival is evident in this group over this period. METHODS: Tasmanian patients with HD diagnosed from 1978 to 1992 were identified retrospectively from the Tasmanian Cancer Registry database. Identification of those diagnosed prior to 1978 was obtained from a previously published data set. To be valid for inclusion, subjects were required to have been diagnosed between January 1972 and December 1992, enabling a minimum four year follow up period. Survival was assessed by contacting patients' medical practitioners and by examining the most current electoral roll, medical records, and the register of births, deaths and marriages. Univariate and multivariate analyses were performed of the influence on prognosis of age, sex, histological subtype and epoch of diagnosis; information concerning stage of disease was not available. RESULTS: During the period of this study 206 patients were newly diagnosed as having HD. Comparisons of cases diagnosed in the successive seven-year epochs 1972-8, 1979-85 and 1986-92 revealed a significant increase in survival duration (p = 0.023), with ten year survival rates of 46%, 55% and 73% respectively. In a multivariate analysis adjusting for age, sex and histology, each successive epoch was associated with an estimated 28% reduction in the death rate relative to the preceding epoch (p = 0.022). CONCLUSIONS: There was a significant improvement in the survival duration of patients diagnosed with HD in Tasmania over the period 1972-92, which was possibly due to a combination of better diagnostic techniques and more effective treatments.

Anatomical correlates of experimentally induced myopia.

PURPOSE: The present study compares morphological changes associated with optical defocus-induced myopia (ODM) with those from form deprivation myopia (FDM), as it is yet to be determined whether the latter is a consequence of visual deprivation or active myopic eye growth. METHODS: Hatchling chicks were reared for 2 weeks wearing a monocular translucent occluder or -10.00 D lens, with the other eye used as a control. After enucleation, eyes were processed for scanning electron microscopy. RESULTS: Anatomical profiles of control eyes revealed significant variations in tissue thickness as a function of nasotemporal location. Both FDM and ODM eyes demonstrated similar morphological profiles of retinal thinning, cartilaginous scleral thickening, enlarged photoreceptor inner segments and decreased photoreceptor cell density towards the ora serrata. A graded differential orientation of photoreceptors existed in all eyes. CONCLUSION: The comparable morphological changes in FDM and ODM suggest that the response to altered visual experience is similar in both paradigms.

Formoguanamine-induced inhibition of deprivation myopia in chick is accompanied by choroidal thinning while retinal function is retained.

Twenty hatchling chickens were injected intravitreally every 4 days from day 2 to day 16 with dimethyl sulphoxide (DS) in one eye and DS or formoguanamine dissolved in DS (FG.DS) with or without occlusion in the other (FG.DS.MD, DS.MD, FG.DS). At day 16, the FG.DS.MD eyes failed to show the high refractive myopia and showed less axial elongation than that developed by the DS.MD eyes. Electroretinograms indicated that at the dosage used, FG.DS does not eliminate phototransduction. Light microscopy showed choroidal and retinal thinning in DS.MD and FG.DS.MD eyes but less than in FG.DS eyes, suggesting that change in choroidal thickness is unlikely to be the primary cause of form deprivation myopia.

The future of hospice care: what will be the costs?

The effective integration of hospice services into the Medicare system may depend heavily on what the costs of such services will be when administered through the home or a hospital. Are hospice services a substitute for treating the terminally ill? More work is needed in determining the cost of care associated with the terminally ill and the effects of a specific delivery mode on the total costs of care.