PubMed · 1366036
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P U Koskela. 1992. [Capricious ocular accommodation and convergence].. https://pubmed.ncbi.nlm.nih.gov/1366036/
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Unusual ocular symptoms observed during intravenous treatment with anti-disialoganglioside antibody (Ab) in children suffering from neuroblastoma were analyzed and the results reported. Within the framework of the German Collaborative Neuroblastoma Study NB97, 85 children with high-risk neuroblastoma received anti-GD2 monoclonal antibody ch14.18 intravenously. Side effects were regularly reported to the study center. Ocular symptoms were recorded in clinical detail, duration and development over time. Symptoms of a parasympathetic deficit corresponding to internal ophthalmoplegia, i.e. mydriasis and accommodation deficit, were found in 10 patients. They were uni- or bilateral, began after the termination of Ab infusion and improved or disappeared in all surviving children. They did not reappear or worsen upon repeated Ab infusions. The pathophysiology of these disorders remains poorly understood. It is concluded that during systemic treatment with the anti-GD2 antibody ch14.18, reversible symptoms of parasympathetic denervation of the eye may occur which, however, do not warrant termination of this treatment.
Children with Down's syndrome are at increased risk of ocular manifestations, which is confirmed by a study in Uppsala, Sweden. Sixty percent of the children were wearing glasses and/or had other ocular problems. However, lapses were found in follow-up and referral to the eye clinic. Good visual function is an important prerequisite for optimal quality of life of children and adults with Down's syndrome. Since this group does not always spontaneously get in touch with the health care system including ophthalmologists, the infant must be referred by the pediatrician immediately after birth. The number of individuals with Down's syndrome in Sweden is large (3,500-5,000), and an ophthalmological follow-up program, as presented in this paper, is of key importance.
The function of the accommodation system is to provide a clear retinal image of objects in the visual scene. The system was previously thought to be under simple continuous (i.e., single mode of operation) feedback control, but recent research has shown that it is under discontinuous (i.e., two stimulus-dependent modes of operation) feedback control by means of fast and slow processes. A model using MATLAB/SIMULINK was developed to simulate this dual-mode behavior. It consists of fast and slow components in a feedback loop. The fast component responds to step target disparity with an open-loop movement to nearly reach the desired level, and then the slow component uses closed-loop feedback to reduce the residual error to an acceptable small level. For slow ramps, the slow component provides smooth tracking of the stimulus, whereas for fast ramps, the fast component provides accurate staircase-like step responses. Simulation of this model using a variety of stimuli, including pulse, step, ramp, and sinusoid, showed good agreement with experimental results. Thus, this represents the first dynamic model of accommodation that can accurately simulate the complex dual-mode behavior seen experimentally. The biological significance of this model is that it can be used to quantitatively analyze clinical deficits such as amblyopia and accommodative insufficiency.