Vaya, veo que al final hemos doblado el post, root.
Si queréis podéis borrar el otro, ya que creo que este está más completo.
Si no conocéis PloS One os la recomiendo. Es una revista gratuita y completamente online, con un índice de impacto de más de 4, por lo que publicar es bastante dificil. Se me olvidó decir que el artículo está online en
http://www.plosone.org/article/info%3Ad ... ne.0040239
Volviendo al artículo de la miopía nocturna, la introducción creo que permite centrar el problema:
"The magnitude of night myopia appears to be very variable among individuals and across different studies. Values ranging from negligible to as much as −4 D of myopic shift have been reported. Average values in most studies are around −1.5 D, a significant figure that would severely degrade the quality of the retinal image. Over more than a century, there was an open debate on the causes of night myopia because different experiments provided often conflicting results. From early on, spherical aberration was suggested as being mainly responsible [7]. The rationale was that under low luminance, the pupil dilates and the natural positive spherical aberration in the eyes [8], [9] would induce a myopic shift. Chromatic aberration was another proposed candidate to explain night myopia [10]. The typical values of longitudinal chromatic aberration in the eye [11], [12] in combination with the Purkinje effect could explain a measurable myopic shift, although most estimates suggested this effect could only play a partial role [4]. Other competing hypotheses included the error in accommodation occurring in dim light [13]. The eye would not have a relaxed accommodation for distant objects under low luminance, producing an apparent myopic shift which would explain night myopia [14]. A large number of experiments have been carried out to isolate these factors and to explain their actual contribution to night myopia. Unfortunately, in many cases the results were contradictory and none of the hypotheses clearly stands out as the key explanation. Other possible explanations proposed include the use of peripheral areas of the retina under low luminance that may have a distinct (and more myopic) refraction [15]. It has often been suggested that a combination of all the factors would actually produce the effect with different relative contributions for each subject."
El problema siempre ha sido el mismo: aislar los diversos componentes que podían estar detrás de la miopía nocturna: iluminación, acomodación pero sobretodo la aberración esférica. Y para ello es encesario un sistema que pueda medir y manipular esa aberración. En este caso utilizaron un sistema de óptica adaptativa que llaman "simulador visual".
Yo creo que la conclusión a la que llega el trabajo son "good news", porque demuestran que aunque es cierto que puede existir un cambio miópico, si sucede es sólo para luminancias muy muy bajas, así que e realidad no hay mucho motivo para pensar que al conducir o hacer tareas convencionales nos hagamos "miopes".
"We found that night myopia is a more elusive phenomenon than generally recognized. Despite the large body of evidence presents in the literature, our experiments performed under controlled conditions showed a large variability in our group of subjects and modest values of myopic shift at low luminance. In half of the subjects a myopic shift was not evident and the maximum shift was around −2 D in one subject with an average of −0.8 D. Inter-subject variability and dispersion of the results were common in previous studies. In some of them [24], a large number of subjects were tested providing up to 6 D range in myopic shifts in the dark. The conditions for that experiment were however very different. Based on our results, it seems that the practical importance of the phenomenon is more limited than was commonly believed. The small values reported in most subjects were only noticeable under very low luminance conditions, which are uncommon in ordinary conditions. In addition, dark adaptation was required for at least 20–30 minutes in complete darkness. For example, at luminance levels even lower than those occurring during night driving tasks (0.02 cd/m2), we did not find a defocus shift (−0.02 D, SD = 0.82 D). The inherent subjective nature of measuring refraction and the number of factors that may affect these determinations could provide an explanation to the variability and dispersion of the results in the studies of this problem. It should be noted that especially for the lowest luminance stimulus the task of finding the best focus was difficult for all subjects. However, the average standard deviation in the defocus estimates was 0.25 D in all subjects. It should be also mentioned that our measurements could be affected by some type of instrumental myopia. However, all the experiments were performed following the same procedure and within the same instrument. As we only compared differences, this should reduce most of the possible effect. In addition, the baseline subjective refraction results at high luminance were in good agreement with the purely objective measurements, not presenting any significant myopic bias."
Espero que os resulte interesante.
SAludos.
