VPB 121: Veterinary Physiology - II (2+1)

ACCOMMODATION OF THE EYE

• Ability of the eye lens to change its focal length by changing its radius of curvature.
• In near vision contraction of ciliary muscels causes decreased tension to the suspensory ligament and causes bulging of the anterior curvature of the eye.
• To cause distant vision ciliary muscles are relaxed and causes increased tension of the suspensory ligament which flattens the anterior curvature of the eye.
• Presbopia : It is the gradual loss in the power of accommodation of eye lens due to aging.
• Refraction errors : Inability of the eye lens to adjust its focal length.
  • Myopia (short sight) : Due to abnormal increase in the anterior – posterior diameter, image fall just before the retina
  • Hypermetropia (long sight) : Due to reduction in the anterior-posterior diameter, image fall just behind the retina
• Astigmatism : No common point of focus due to difference in the radius of curvature of cornea, overlapping of images.