This study presents the first direct evidence of low folate status and indoor pollution in the aetiology of endemic bilateral optic neuropathy in Tanzania.

Epidemic levels of optic neuropathy are evident in Somalia. The extent of visual loss in the first month emphasizes the need to initiate treatment early in the course of the disease. Training and establishing health surveillance systems in community clinics may form a central component to this strategy.

Combined displays of graphics and text, such as figure captions in newspapers and books, lead to distinctive inspection patterns, or scanpaths. Readers characteristically look very briefly at the picture, and then read the caption, and then look again at the picture. The initial inspection of the picture is the focus of interest in the present experiment, in which we attempted to modify the inspection by giving participants advance knowledge of the subject of a sentence (the cued object) that was to be verified or denied on the basis of whether it correctly described some aspect of the scene shown in the picture. Eye fixations were recorded while the viewers looked at the picture and the sentence in whatever sequence they chose. By allowing viewers to know the subject of the sentence in advance, we asked whether patterns of fixations on the sentence and on the second inspection of the picture would reflect prior knowledge of the focus of the sentence. Providing advance information did not influence eye movements while reading the sentence. It did, however, increase the number of fixations in the initial inspection of the picture, and it also reduced the number and duration of the fixations on the pictures overall. The results suggest that cueing participants to the object allowed increased coding in the initial inspection of the picture, though the benefit of such coding only becomes apparent when the picture is inspected for the second time.

Measurement of alpha-glucosidase activity on dried blood spots has been the main method to screen for Pompe disease, but a paradigm shift has been observed in recent years with the incorporation of gene panels and exome sequencing in molecular diagnostic laboratories. An 89-gene panel has been available to Canadian physicians since 2017 and was analyzed in 2030 patients with a suspected muscle disease. Acid alpha-glucosidase activity was measured in parallel in dried blood spots from 1430 patients. Pompe disease was diagnosed in 14 patients, representing 0.69% of our cohort. In 7 other patients, low enzyme activities overlapping those of Pompe disease cases were attributable to the presence of pseudodeficiency alleles. Only two other patients had enzymatic activity in the Pompe disease range, and a single heterozygous pathogenic variant was identified. It is possible that a second variant could have been missed; we suggest that RNA analysis should be considered in such cases. With gene panel testing increasingly being performed as a first-tier analysis of patients with suspected muscle disorders, our study supports the relevance of performing reflex enzymatic activity assay in selected patients, such as those with a single GAA variant identified and those in whom the observed genotype is of uncertain clinical significance.

Our data indicate that bilateral optic neuropathy is nonepidemic in The Gambia. Rare vitamin B12 and folate deficiencies reported in rural Gambians may explain the low prevalence because previous epidemics were due to nutrient deficiency. Our study is the only available estimate of epidemic optic neuropathy in The Gambia and, as such, provides an important contribution to our knowledge in identifying characteristics that may cause specific populations to be more susceptible to this public health burden.

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