Permanent Damage to Eye and Ear Cells

Permanent damage to eye and ear cells can affect vision and hearing because some sensory cells cannot be replaced. In humans, the photoreceptor cells of the eye and the sensory hair cells of the ear lack stem cells. That means these cells are unrenewable, so they cannot be replaced after they are damaged or destroyed.

In humans, two sensory structures of the body- the retinal epithelium and the auditory epithelium, lack stem cells.

In  the case of retinal epithelium, if the photoreceptors degenerate with time or are  damaged due to exposure to high beam light, the loss cannot be compensated, leading to partial or complete blindness.

Similarly, i...