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Sir, Gaucher disease is the most common lysosomal storage disease with an estimated incidence of 1/57 000.1 It results from a deficiency in β-glucocerebrosidase and accumulation of glucosylceramide. Typically patients develop hepatosplenomegaly and osseous manifestations. Neuronopathic involvement is less common, but ocular manifestations including oculmotor apraxia and supranuclear gaze abnormalities are usual in Types II and III. Intraocular manifestations including corneal clouding and retinal lesions have also been reported.2, 3 However, little is known about their natural progression.

A 2-year-old boy meeting the criteria for autistic disorder was diagnosed 2 years later with a visual agnosia characterised by a combination of certain aspects of associative and apperceptive agnosia. MRI then revealed a severe encephalomalacia of the right temporal lobe and bilateral temporo-occipital areas. This association is discussed in terms of a clinical and aetiological relation between autistic disorder and visual agnosia.

To determine the ability of the Hardy-Rand-Rittler (HRR) and Ishihara colour plates to detect acquired colour vision defects in patients with nonglaucomatous optic neuropathy (NGON).Prospective study.Neuro-Ophthalmology Unit of the Wilmer Eye Institute, Baltimore.A total of 178 consecutive patients (349 eyes) referred to the Neuro-Ophthalmology Unit and the General Eye Service of the Wilmer Eye Institute and examined by two of the authors were enrolled from July 1992 to June 1993.Results of testing with HRR and Ishihara plates.Among the 202 eyes that were found to have no ocular disease on neuro-ophthalmologic testing, the HRR plates gave a normal result in 168 (83.2%), compared with 196 (97.0%) with the Ishihara plates (p0.0001). The HRR plates detected an acquired colour vision deficit in 48 (87.3%) of the 55 eyes with NGON, compared with 38 (69.1%) for Ishihara plates (p = 0.001). The values for the eyes with NGON with a visual acuity of 20/25 or better were 76.5% (13/17) and 35.3% (6/17) respectively (p = 0.008) and with a visual acuity less than 20/25, 92.1% (35/38) and 84.2% (32/38) respectively.For patients with unilateral or bilateral NGON, HRR plates are more likely than Ishihara plates to detect a colour vision defect, particularly when the visual acuity is 20/25 or better. However, neither test is sensitive enough to be used as the sole criterion for the diagnosis of NGON. The results of comparison of colour perception of the two eyes may be more useful than absolute colour vision responses, particularly in patients with unilateral disease.

A 16-year-old girl developed headaches and bilateral papilledema while taking minocycline for acne. The initial neuro-ophthalmologic evaluation was normal except for enlarged blind spots OU. An MRI scan demonstrated subtle abnormalities. A lumbar puncture was entirely normal except for an increased opening pressure. A tentative diagnosis of pseudotumor cerebri was made and the patient was treated with Diamox. A second MRI was unchanged, and a lumbar puncture performed while the patient was taking Diamox was entirely normal. The patient subsequently lost vision in both eyes, and a third MRI now revealed a supracellar enhancing mass. Biopsy and subtotal resection of the mass showed it to be a glioblastoma multiforme. This case emphasizes pitfalls in the diagnosis of pseudotumor cerebri. Careful follow-up and a high index of suspicion in pseudotumor cerebri syndromes are essential.

Bridge load and resistance parameters involve a considerable degree of uncertainty. Therefore, the reliability analysis can be used to quantify the risk. There has been a considerable research activity in the area of structural reliability in the last two decades. There are methods available for calculation of the probability of failure for components of buildings, bridges and other structures. They are summarized in several books (e.g. Thoft-Christensen and Baker 1982; Ang and Tang 1986; Madsen, Krenk and Lind 1986; Melchers 1987). For given statistical models of loads and resistance the available methodology provides accurate results. Structural safety was evaluated for bridge components (e.g. Nowak and Grouni 1990).