In order to allow players with a similar level of sight to compete sight classifications are used in sound tennis.
Details about sight classifications and how to obtain then can be found at: https://britishblindsport.org.uk/educationandresearch/classifications/.
Sight Classifications are based on acuity and field of vision. The acuity may be measured using Snellen or Logmar. below is a summary using Snellen.
This category includes: having no light perception in either eye, light perception and ability to perceive some movement in front of the eye but inability to recognise shapes.
Partially sighted B2 athletes will have limited vision in both eyes either in how far or how wide they can see.
This category includes being able to count fingers at 15 centimetres to a visual acuity of up to and including 2/60.
2/60 means somebody within this sight category would see the top letter of the vision chart at a distance of up to and including 2 metres. A normally sighted person would see that letter at a distance of 60 metres.
B2 also includes someone with a visual field of under 10 degrees even if their acuity is better than 2/60.
B3 is the highest category used for most international & Paralympic sport and includes those with a level of vision better than 2/60 and up to and including 6/60.
It also includes those with a visual field of less than 40 degrees who may have acuity better than 6/60.
Anyone with better vision than 6/60, and up to and including 6/24 would be within this sight category.