Os estudos de Thomas Young sobre a acomodação ocular: análise do episódio e tradução comentada do texto “Observations on vision” (1793)

Neste artigo, apresentamos uma tradução comentada para o português do texto “Observations on vision” (1793), de Thomas Young (1773-1829), seu primeiro trabalho publicado nas Philosophical Transactions da Royal Society. Nesse texto, Young discutiu algumas teorias e ideias sobre a acomodação visual existentes até sua época. Após apontar diversas falhas nessas teorias, ele propôs a sua, baseada na existência de uma musculatura no cristalino responsável especificamente por esse mecanismo. A tradução é precedida por três seções, em que aspectos da história da anatomia ocular e das teorias anteriores para a acomodação visual são abordados, a fim de contextualizar a leitura do material traduzido.Thomas Young’s studies on visual accommodation: an analysis of the episode and a commented Portuguese translation of his “Observations on vision”(1793)AbstractIn this paper, we present a commented Portuguese translation of Thomas Young’s (1773-1829) “Observations on vision” (1793), his first published paper in Royal Society’s Philosophical Transactions. In this article, Young discussed some previous theories and ideas on visual accommodation up to his days. After pointing out the flaws of these theories, he proposed his own: muscles in the crystalline lens were responsible for this mechanism. The translation is preceded by three sections in which we comment on aspects of the history of eye anatomy and of the previous theories for visual accommodation, in order to contextualize the reading of the translated material.Keywords: Visual accommodation; Optics; Vision; Thomas Young; Light.

Is Regular Physical Activity Practice During a Submarine Patrol an Efficient Coping Strategy?

Introduction: A nuclear-powered ballistic missile submarine (SSBN) is a singular professional environment, exposing personnel to isolation and confinement amidst sophisticated technology for the duration of a mission. Submariners see their mood and cognition deteriorate as their mission progresses. With regard to the benefits of physical activity (PA) on mental health, this study evaluates the impact of regular PA on the maintenance of thymia and sensory functioning during patrols.Method: This pragmatic exploratory cohort follow-up study included 29 volunteer submariners before, during and 1 month after return from patrol. PA practice was evaluated by a daily self-questionnaire. This allowed submariners to be classified into two groups according to the median of the total duration in minutes of a sport practiced during the patrol (PA practicing submariners and non-practicing). Changes in mood and psychological activation, health (including sleep), unipodal stability, and accommodation distances were compared between the two groups over the period of the patrol.Results: Overall thymic functioning deteriorated during the patrol. Submariners who practice PA maintain a stable level of activation unlike non-practicing PA submariners, but they exhibited both worse general health and sleep at recovery. For these personnel, postural control is better at the end of the patrol and far visual accommodation tends to be preserved.Conclusion: PA during patrol alone is not sufficient to compensate for the thymic dysregulation induced by the SSBN environment. Nevertheless, it seems to help in maintaining an exteroceptive functioning. This exploratory study suggests directions for possible future research on physical activity associated with sensory stimulation amongst submariners, and more generally amongst people working in isolated and confined environments.

Visual accommodation and active pursuit of prey underwater in a plunge-diving bird: the Australasian gannet

Australasian gannets ( Morus serrator ), like many other seabird species, locate pelagic prey from the air and perform rapid plunge dives for their capture. Prey are captured underwater either in the momentum (M) phase of the dive while descending through the water column, or the wing flapping (WF) phase while moving, using the wings for propulsion. Detection of prey from the air is clearly visually guided, but it remains unknown whether plunge diving birds also use vision in the underwater phase of the dive. Here we address the question of whether gannets are capable of visually accommodating in the transition from aerial to aquatic vision, and analyse underwater video footage for evidence that gannets use vision in the aquatic phases of hunting. Photokeratometry and infrared video photorefraction revealed that, immediately upon submergence of the head, gannet eyes accommodate and overcome the loss of greater than 45 D (dioptres) of corneal refractive power which occurs in the transition between air and water. Analyses of underwater video showed the highest prey capture rates during WF phase when gannets actively pursue individual fish, a behaviour that very likely involves visual guidance, following the transition after the plunge dive's M phase. This is to our knowledge the first demonstration of the capacity for visual accommodation underwater in a plunge diving bird while capturing submerged prey detected from the air.

Simultaneous measurement of visual accommodation and convergence during 3D sickness

It is generally explained to the public that, ‘During stereoscopic vision, accommodation and convergence are mismatched and this is the main reason for the visual fatigue and the visually induced motion sickness caused by 3D’. The aim was to compare fixation distances between accommodation and convergence in young subjects while they viewed 3D video clips on a liquid crystal display (LCD). According to stabilometry and subjective items, we also analyzed the severity of motion sickness induced by viewing the above-mentioned 3D films. As results, statistical comparisons revealed that viewing the 3D film significantly affected body sway. Moreover, the accommodative power is similar to the distance of convergence without eyestrain in the phase component.

Effectiveness of New Technology to Compose Stereoscopic Movies

The most widely known theory of motion sickness and asthenopia are based on the concept of sensory conflict, a disagreement between vergence and visual accommodation while viewing stereoscopic images. Visually induced motion sickness (VIMS) can be measured by using psychological and physiological methods. We quantitatively measured vergence, visual accommodation, head acceleration, and body sway before and during exposure to conventional and new stereoscopic movies. Sickness symptoms appeared with exposure to stereoscopic images. We found that some analytical index for stabilograms increased significantly when the subjects viewed a 3D movie. VIMS could be detected by using these indices. While lateral sway is dependent on the transverse component of head movement while watching the conventional stereoscopic movie, we examine whether this tendency is reduced by Power 3D.