Eye References In The Homeric Epics

With aging, the quality of vision worsens due to reasons independent of diseases of the aging eye. While there are many changes of significance in the non-diseased eye, the most functionally important changes seem to be a reduction in pupil size and the loss of accommodation or focusing capability . The area of the pupil governs the amount of light that can reach the retina. The extent to which the pupil dilates decreases with age, leading to a substantial decrease in light received at the retina. In comparison to younger people, it is as though older persons are constantly wearing medium-density sunglasses. Therefore, for any detailed visually guided tasks on which performance varies with illumination, older persons require extra lighting.

For the vertical line it says it must be at the edge of the field of view. You should position yourself in the VC so that you can see the bottom of the ND and PFD and have a good view out of the whole of the front windscreen with the right hand half of the upper frame of the front windscreen just in view. However, in the -8 aircraft you might want to position yourself slightly further back so that you can easily select the EFB/Radio hotspot without moving your seat position. The centre of your PFD should also be centered relative to the centre of your body (i.e. in the middle of your monitor screen.

The vitreous gel undergoes liquefaction and its opacities — visible as floaters — gradually increase in number. When a creature with binocular vision looks at an object, the eyes must rotate around a vertical axis so that the projection of the image is in the centre of the retina in both eyes. To look at a nearby object, the eyes rotate ‘towards each other’ , while for an object farther away they rotate ‘away from each other’ .

More detailed information about ocular albinism and oculocutaneous albinism, as well as the genetics of eye, hair, and skin color variation, is available from OMIM.org. How does the pineal perceive light, directly, by being a light sensor itself, still performing some of the functions of an eye; or indirectly, via the central nervous system? Light does penetrate bone and brain to reach the pineal in significant amounts. F. Ganong, who implanted photocells adjacent to the site of the pineal in sheep and got altered readings from his instruments depending on whether the animals were standing in direct sunlight or in shade. On the other hand, if animals are blinded, or have the nerves connecting the eye to the brain severed, some of the pineal rhythms are dampened, just as though the animals were being maintained in continual darkness.

Strong suspicion has fallen now on serotonin as being one of the principal agents of the psychedelic experience, but whatever its role, it is certain that other neurohumors are additionally involved in the chemical transactions which produce the state. It is likely that LSD itself produces certain effects quite on its own. Studies made with tracer elements and the electron microscope now reveal that LSD strikes like a chemical guerrilla, entering into receptor granules in brain cells swiftly, and then leaving swiftly after a very short time, perhaps ten or twenty minutes . This initial period coincides with the onset of the most violent symptoms of the LSD state as it is observed in test animals. But when the twenty minutes are done, and the bulk of the LSD has left the receptor granules, it is replaced by what seems to be excessive, or supernormal, amounts of serotonin. Since the LSD state lasts for some ten hours, and during this time serotonin can be measured in supernormal amounts in receptor granules, it must be considered one of the important participants of that chemical transaction which produces the state.