Presbyopia occurs as a result of the following
Presbyopia (eyesight of old age) is not an error of refraction but a condition of physiological insufficiency of accommodation leading to a progressive fall in near vision. The cause of presbyopia is believed to be due to thickening and loss of flexibility of the lens in the eye. Reference: AK khurana 7th edition
Shoening of eye ball
Hardening of lens
Thinning of the lens
Lengthening of eye ball
Optics and refraction