This is a focusing error which causes image distortion and irregular blur.The object being viewed may appear distorted in one direction.
There are three reasons for the astigmatism to appear. The first and by far most common is buckling and distortion of the front surface of the eye called the cornea. The front tissue may resemble the shape of a football, rather than the soccer ball. There are many triggers which can cause this to occur spanning from hereditary expression through to hormonal variations.
The second reason for astigmatism, is tilting of the lens inside the eye. This may be seen in individuals after frontal eye trauma or who have certain connective tissue disorders .
The third reason, is tilting of the retinal elements at the back of the eye. The retinal photo receptors point up a little like fibers on a velvet, and their mis-orientation can induce astigmatic distortion.
Astigmatism can be corrected quite accurately with spectacles, contact lenses, lenticular implants, and with variable degree of success ; refractive laser surgery, namely, LASIK, PRK and SMILE procedures utilizing careful vector planning.
Discuss your finding with Chris.