Understanding Eye Reports

The opthamologist wrote a report about Marcus' vision. He said:

Marcus is a 10 year old boy with Stargardt's Disease. His visual acuity with both eyes open is 6/36. His central vision is continuing to deteriorate while his peripheral vision remains intact.

Eye reports can be very confusing. Let's have a look at what Marcus' eye report means.

Eye Condition

Stargardt's Disease is an eye condition which can run in the family. Marcus' cousin Kim has it too. It affects the nerves in the central part of each retina (called the macula), causing central vision loss. That is the part of our vision we use for focusing on things, for reading and looking at people's faces.

Marcus doesn't need to have any medicine for his eyes. Surgery can't fix the problem. Glasses won't help either. Marcus' central vision will get worse over time.

Visual Acuity

Visual acuity describes how clearly a person can see. Marcus can't see objects or words very well if he looks straight at them. He says it looks as though someone has rubbed out the middle.

Visual acuity is recorded as a fraction (the Snellen Fraction). It is measured with an eye chart showing different sized letters.

• The first number in the Snellen Fraction is always the distance between the eye and the chart. The second number shows which is the smallest line on the chart the eye can see.
• 6/6 is normal vision. This means you can see at 6 metres what a person with normal vision can see at 6 metres.
• 6/36 means that Marcus has to come as close as 6 metres to see what a person with normal vision can see at 36 metres. Marcus can read the big E at the top of the chart, but he can't read the next line.

Visual Field

Visual field describes how widely a person can see. Your visual field is a combination of your central vision and your peripheral vision.

Central vision helps you to see colour and fine details (like ants and specks of dust). Peripheral vision helps you to see in the dark, detect movement (like someone creeping up beside you) and notice big things (like the outline of a building). It is not very useful for fine detail.

Visual field is recorded in degrees of a circle.

• People with normal vision can see about 180° from one side to the other when they are looking straight ahead.
• Marcus' vision loss affects the central 10° of his vision field.

Although his central vision is getting worse, Marcus' peripheral vision still works very well. He can nearly always see the soccer ball coming towards him from the side!

Legal Blindness

Legal blindness means that a person has less that 6/60 visual acuity or less than 10° visual field remaining in their better eye. This does not necessarily mean that they are blind. Legally blind people over the age of 16 can get a government pension and travel on public transport for free. Marcus is not legally blind.