Optokinetic nystagmus in strabismus: are asymmetries related to binocularity?

PURPOSE: Strabismus may be associated with an asymmetry of monocular horizontal optokinetic nystagmus (OKN). It is unclear whether OKN asymmetries are associated with deficiency in binocular and/or stereovision. In the current study, patients with different degrees of binocularity were investigated. METHODS: OKN was examined in the dominant and nondominant eyes of four groups of patients: (1) no measurable binocularity (NB), (2) poor binocularity (PB)-that is, showing binocularity on the Bagolini Test and/or rudimentary stereovision, (3) good binocularity (GB) with good stereoacuity after squint surgery, and (4) a control group. Monocular OKN was elicited with black-and-white stripes moving temporally to nasally (TN) or nasally to temporally (NT) at velocities of 15, 30, 45, and 60 deg/s. Eye movements were recorded with infrared oculography. RESULTS: Only subjects in the NB group showed a significant OKN asymmetry, with preference for TN stimulation in dominant and nondominant eyes. Subjects with PB did not have significant OKN asymmetries but reduced OKN gains in both stimulus directions. Subjects with GB had normal mean OKN gains without asymmetry. Larger OKN asymmetries were correlated with younger age at detection of strabismus if NB and GB were grouped together, but not if each group was analyzed separately. CONCLUSIONS: For the first time, a large groups of patients classified by level of binocular vision has been investigated. The results show that OKN gain and asymmetry are associated with the development of binocular vision. OKN investigation may be helpful to identify patients with binocularity or binocular potential in strabismus.     

How much has the introduction of laparoscopic surgery changed open surgery?

During the last decade of the twentieth century there was a proliferation of laparoscopic surgical procedures. This has been credited with significantly improving the care and outcomes of surgical patients, despite the presence of little evidence to support such claims. Many laparoscopic procedures have developed due to the perception that they are better; however, this perception was not and is not supported by level one data (randomised controlled trial). It is hard to obtain level one data to validate the perception of advantage once a technique has become fully established. At the same time that laparoscopic surgery was developing, many other aspects of peri-operative care changed that influenced outcomes. These changes may account for many of the benefits claimed by laparoscopic surgery.     

Population and antenatal-based HIV prevalence estimates in a high contracepting female population in rural South Africa

Background  

To present and compare population-based and antenatal-care (ANC) sentinel surveillance HIV prevalence estimates among women in a rural South African population where both provision of ANC services and family planning is prevalent and fertility is declining. With a need, in such settings, to understand how to appropriately adjust ANC sentinel surveillance estimates to represent HIV prevalence in general populations, and with evidence of possible biases inherent to both surveillance systems, we explore differences between the two systems. There is particular emphasis on unrepresentative selection of ANC clinics and unrepresentative testing in the population.     

Accumulation of A2-E in mitochondrial membranes of cultured RPE cells

Background Lipofuscin occurs in association with various blinding diseases, including ARMD. Formation of lipofuscin is considered to be initiated by the inability of the RPE lysosome to degrade constituents of phagocytosed material resulting in its intralysosomal accumulation. Thus, the deposition of abnormal retinoid adducts causing the autofluorescent properties of RPE lipofuscin originates from abnormal products of the retinoid cycle contained in phagocytosed photoreceptor outer segments. The major lipofuscin retinoid conjugate A2-E was previously shown to exert toxic effects on RPE cells by directly damaging lysosomal function and structure. However, A2-E was also proposed to severely harm extralysosomal RPE cell structures during the pathogenesis of ARMD. This would require release or leakage of A2-E from the lysosomal compartment with subsequent targeting of other cellular compartments. Methods We therefore now investigated intralysosomal accumulation, possible biodegradation, release from the lysosomal compartment and intracellular spreading of ¹⁴C-labelled A2-E in cultured human RPE cells. We specifically loaded lysosomes of cultured human RPE cells with [¹⁴C]A2-E. Results A linear increase of intracellular radioactivity was observed during the 4-week loading period. Cell fractionation experiments indicated that more than 90% of loaded A2-E was specifically accumulating in the lysosomes. After loading, the fate of the radioactive label was chased over a period of an additional 4 weeks. No metabolism or secretion of A2-E to the medium was detectable. Subcellular fractionation revealed that during the chase period, about 13% were shifted from the lysosomes to mitochondrial fractions. This effect was strikingly intensified when after loading the cells with the labeled retinoid, its intralysosomal concentration was boosted by an additional load with non-labeled A2-E. Thus about 44% of the label were located in mitochondria at the end of the chase period. No significant spreading to other cell compartments was detectable. Conclusions Since A2-E was suggested to act as a proapoptotic molecule via a mitochondrial pathway, we postulate that upon reaching a critical intralysosomal concentration, A2-E is released from the lysosome and then specifically targets the outer mitochondrial membrane thereby initiating apoptosis of the RPE cell. This may also apply correspondingly to other lipofuscin-associated molecules that cause leakage of the lysosomal membrane. DFG Grant Ho 1926/2-2, DFG Priority Research Program AMD (1088), Germany.