Understanding sight loss


  1. Definitions
  2. Types of Sight loss
  3. Common Causes
  4. Summary

In this guide we will cover definitions, common causes of sight loss and how they affect vision. While it can be helpful for sight guides to have a basic understanding of some of the causes of visual impairments it’s not something to get hung-up on. Understanding what a person’s vision is like is much more relevant than the exact condition(s) they have.


You may hear people use the term registered VI (visually impaired), SSI (severely sight impaired), partially sighted or blind. Historically, people would register as blind. In more recent times this has changed to severely sight impaired because few people registered SSI are completely blind. Some people may see light and dark, shadows, or may even be able to read. People may use any of the terms mentioned here to describe their sight loss.

Types of sight loss

There are many different conditions that can cause sight loss. Some people with sight loss are born blind. Some people have a condition that gets progressively worse overtime. For other’s it could be a complication of an illness or an injury. The cause isn’t that important in climbing most of the time.

Some conditions affect peripheral vision, others central vision and some are a bit more random. Sometimes people have a very small field of vision which can be quite clear. Others may be able to see a wide area with very little detail. It’s always best to have a chat to try and gain an understanding of what somebody’s vision is like but be mindful it’s not always easy to explain or understand.

It’s possible for people to have more than one condition affecting their eyes; for example, John has Retinitis Pigmentosa (RP) and Cataracts. The RP restricts his field of vision to a narrow tunnel and the cataracts makes that remaining vision cloudy.

The quality of light will also affect what many people can see. As a result, people’s vision may change on a day-to-day basis.

A craggy rocky view.
A representation of John's vision. Most of the image is black, with a small circle of blurry vision visible in the middle.

A view of The Roaches. The first picture is what somebody with typical vision may see. The second picture is a representation of Retinitis pigmentosa.

Common causes


Glaucoma is a common eye condition where the optic nerve becomes damaged. It’s usually caused by fluid building up in the front part of the eye, which increases pressure inside the eye.


Cataracts is when the lens inside the eye develops cloudy patches. Over time these patches usually become bigger causing blurry, misty vision and eventually (when untreated) blindness.

Macular Degeneration

Macular degeneration is a common condition that affects central vision. It doesn’t usually result in total blindness.

Diabetic Retinopathy

Diabetic retinopathy is a complication of diabetes, caused by high blood sugar levels damaging the back of the eye (retina)

Retinitis Pigmentosa

RP causes progressive loss of night & peripheral vision. It is usually inherited.


Here are some things it would be useful for a sighted guide to understand:

  • What useful vision does the climber have and if so, is the central or peripheral vision better?
  • How clear is any remaining vision and how far ahead can they see?
  • How does light affect the climbers vision? Will a bright light at the top of the wall help, or cause problems?
  • Have they had sight previously? This may affect their understanding of the sport, task or venue.