We are all familiar with glasses and how they work; that is, you don’t see things clearly, you get your eyes tested, glasses are prescribed and fitted and then you are able to see things more clearly, if not perfectly.

This is very different to hearing aids and cochlear implants and this can sometimes be perplexing to people.

Put simply, the reason why glasses can correct your vision is because the problem that requires you to need glasses is that the refraction of the image coming into the eye is to the wrong focal at the back of the eye resulting in the image being unclear.  Put on the glasses and the image lands at the correct focal point.  Similarly, if one has distorted vision due to an astigmatism, glasses can be fitted to compensate and vision becomes clear.

However, this scenario of having glasses prescribed to correct your vision to normal is only true for eye problems that have certain functional difficulties.

For eye problems that involve the nerve cells or tissue at the back of the eye (for example, Retinitis Pigmentosa, Macular Degeneration, Diabetic Retinopathy, etc.) there is no possible correction from glasses.  This is because the nerve receptors and/or the nerves are damaged or destroyed.

It is helpful to understand this because it is for a similar reason that hearing technology does not “fix” what a deaf person can hear; that is, the nerve receptors are damaged or missing.  A hearing aid or cochlear implant can only make sound more accessible; it cannot provide correction to damaged nerve cells.

At this stage, the medical world is not able to repair or replace damaged or destroyed nerves – in the eye, the ear or in any part of the human body.

It is worth noting that hearing aids and cochlear implants make sound accessible in different ways.  Hearing aids merely amplify sound to a level that the deaf person may be able to perceive the sound.  On the other hand, cochlear implants actually stimulate the auditory nerve; however, the sound that is heard by the individual is very different to the sounds that we hear.

 

 

References:

http://www.nidcd.nih.gov/health/hearing/pages/coch.aspx

http://www.scic.org.au/our-clinic/learn-about-cochlear-implants/

http://www.myeyes.com/functions-of-the-eye.shtml

http://www.afb.org/info/the-human-eye-its-functions-and-visual-impairment/5