Help me choose where to start
Four ways in, depending on whether you are curious, have a diagnosis, need support or are helping someone else.
Understand how sight works, what eye conditions mean and where to get help in the UK
Interactive demonstrations, 26 plain-English condition guides and a support directory for all four UK nations. Every page links to the official source behind the text.
Start here
Something has changed suddenly
Who to contact for sudden sight loss, pain, flashes, floaters and new double vision.
I have the name of a condition
Read what the name means, what changes in daily life and what to ask at your appointment.
I need support near me
Hospital eye services and sight-loss charities across 12 UK areas.
Colour blindness explained
Compare the main types and see what makes everyday information easier to read.
Four ways in
Vision explorer
Compare an ordinary street, a living room and a page of text with 13 visual effects and 26 named conditions. Change one thing at a time and see what happens.
OpenVision labs
Seven short experiments on focus, contrast, side vision, light, colour, depth and the retina. Each one links to the conditions where the idea matters.
OpenEye conditions
Plain-English guides with everyday examples, a question to take to your appointment and the official source for every page.
OpenUK support
Urgent help, NHS eye care in each nation, local services and charities you can call.
OpenTools you can try
Colour studio
Protan, deutan and tritan models on the same travel board, with and without labels.
Room illustrations
Three teaching pictures of one living room.
Compare two guides
Two conditions side by side, with the parts of vision each one involves.
Search the site
Guides, labs, glossary terms, charities and areas in one search.
Quick answers
Is a change in my sight an emergency?
If you suddenly cannot see from one or both eyes, or you have sudden severe eye pain, call 999 or go to A&E. New flashes, floaters, a shadow or sudden blur need an urgent optometrist appointment or NHS 111 the same day.
Who should I see first about my eyes?
For most problems, an optometrist (at an opticians) is quicker to see than a GP and can refer you to hospital. A pharmacist can help with dry, gritty or crusty eyes.
Is my sight test free?
In England you qualify if you are under 16, aged 16 to 18 in full-time education, 60 or over, have diabetes or glaucoma, or meet other criteria. Scotland offers free NHS eye examinations to everyone who usually lives in the UK. Wales and Northern Ireland have their own rules.
Do these demonstrations show what someone else sees?
No. They show one visual idea at a time on a screen. Real sight varies with the person, the task, the lighting and the day. Ask the person what helps them.
Where does the information come from?
Every guide links to its NHS, hospital or charity source. All links were checked on 4 October 2026. The site is funded by Medstack Ltd and carries no advertising. The site has not yet been clinically reviewed.
Seven vision labs
Sharpness is only part of sight. The labs cover contrast, side vision, light, colour, depth and how the retina works.
Focus and refraction
Why can the same eye see a book and a distant building differently?
The cornea and lens bend light towards the retina. See what happens when the focus and the back of the eye do not line up.
LabDetail and contrast
Can something be sharp and still hard to make out?
Small detail and low contrast are different demands on vision. Change one at a time to see why a letter chart cannot describe every part of useful sight.
LabCentral and side vision
What do you miss when a different part of the view is hidden?
Central vision handles fine detail. Side vision is the surrounding view. Compare the same scene with a central patch and with the outer field restricted.
LabLight and glare
Why can a bright lamp make a task harder?
A direct reflection can wash out detail. Explore the difference between how much light there is and where the light falls.
LabColour and information
Can you follow a route when colour is no longer the only clue?
Colour vision differences usually affect particular colour pairs. Labels, symbols and patterns make information readable without relying on colour.
LabTwo eyes and depth
Why do nearby objects shift more between two viewpoints?
Each eye has a slightly different view. The brain uses the difference, along with other clues, to judge depth.
LabRods and cones
Why does the order of rods and cones matter?
Explore the different contributions of light-sensitive cells and the terminology of inherited retinal conditions.
LabEye care in the UK, explained
Sight tests, screening, children, eye drops, registration and surgery, in plain English with the NHS page behind each one.
What happens at an NHS sight test
What the optometrist checks, how long the test takes, what the results mean and how often to go back.
GuideDiabetic eye screening explained
Who is invited, what happens at the appointment, what the result letters mean and why you should still have ordinary sight tests.
GuideChildren's eye care on the NHS
The checks every child gets, the signs to watch for, free glasses and what happens if a problem is found.
GuideHow to use eye drops
A step-by-step method, what to do if you miss a dose, how long bottles last and aids which make drops easier.
GuideBeing registered as sight impaired
How certification (CVI) and registration work, what the two levels mean and the help registration opens up.
GuideCataract surgery on the NHS
When surgery is offered, what the operation involves, recovery, and the questions to ask before you agree.
Guide