Retinal image quality for peripheral as well as central visual field locations has been investigated in humans and an animal model (Columba livia) with wide- angle, panoramic vision because of its laterally oriented eyes. The goal was to determine whether the retinal image is maintained at a higher quality away from the fovea in pigeons as compared to humans. In this thesis, the HSWFS (Hart- mann Shack Wavefront Sensor) has been implemented with the correspondent validation and application for measuring ocular aberrations in the human and avian eye. Using a modified HSWFS, the refractive error and total amount of ocular aberra- tions were measured for 20 pigeons along the horizontal meridian and for another 8 pigeons in the vertical meridian at three positions along the horizontal meridian. The HOA( High order aberrations) of 10 humans were measured at peripheral locations (±35 ◦) in the upper visual field and along the horizontal meridian. The anaesthetized animal’s head position was controlled by a stereotaxic head holder capable of horizontal and vertical rotation. Measured eccentricities were(±60◦) from the fovea in the horizontal meridian and +35 ◦ and -25 ◦ along each of the three vertical meridians. In pigeons, the LOA (astigmatism) on the horizontal meridian increase slightly from the center towards the far periphery but are relatively constant for ±20◦ around the fovea, whereas defocus remains almost constant. Vertical meridian measurements are consistent with the previously reported myopia in the lower visual field. Compared with measurements in human subjects, the overall values of RMS are much lower in the pigeon at all corresponding eccentricities. Off-axis vision is generally dominated by defocus and astigmatism. In pigeons, however, defocus along the horizontal meridian does not change dramatically whereas, along the vertical meridian, the presence of a lower field myopia is confirmed. Astigmatism of the eye for increasing eccentricity (horizontally and vertically) is consistently lower then expected theoretically and when compared with humans. This demonstrates that the visual optics of the pigeon are more fully corrected for peripheral vision than in humans.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:567444 |
| Date | January 2012 |
| Creators | Garcia Sanchez, Yaiza |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/41966/ |
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