Eye Conditions and Refractive Errors
The conditions behind the symptoms people search for, and the refractive errors laser surgery is meant to correct.
Quick answer
An eye condition is what is happening to the eye; a refractive error is how well it focuses light. Short sight, long sight and astigmatism are refractive errors, and conditions such as cataract, glaucoma and keratoconus are structural. Some of them change whether refractive surgery is appropriate.
These pages describe conditions in general. They cannot tell you what is happening in your own eye, and several of the conditions listed here are detected only during a dilated examination.
- Pages in this family
- 11
- Guides covering them
- 4
- Questions linked
- 8
11 pages in this family
- Myopia (short sightedness)
The eye focuses light in front of the retina, so near objects are clear and distant ones are blurred. It is the refractive error most commonly treated with laser vision correction.
- Hyperopia (long sightedness)
The eye focuses light behind the retina. Younger eyes often compensate without noticing, which is why it tends to present later than short sightedness and is assessed more cautiously for surgery.
- Astigmatism
The cornea is curved unevenly, so light is focused differently across different axes and the blur is not the same in every direction. It commonly occurs alongside short or long sightedness.
- Presbyopia
The natural lens stiffens with age and can no longer change focus enough for close work. It is a change in the lens, not in the cornea, which is why corneal laser treatment alone does not remove it.
- Dry eye
The tear film is unstable or insufficient, so the surface of the eye is uncomfortable and the vision can fluctuate. It matters before surgery because it is also one of the things refractive surgery can temporarily make worse.
- Cataract
The natural lens becomes cloudy, so vision loses contrast and sharpness. It is treated by replacing the lens, and the lens chosen at that point is what decides reading and distance correction afterwards.
- Glaucoma
Progressive damage to the optic nerve, usually associated with eye pressure. It is silent for a long time, which is why it is found by examination rather than by noticing something.
- Keratoconus
The cornea thins and becomes irregular, so vision is distorted in a way glasses do not fully correct. It changes which refractive options are open, and it is usually the reason a laser procedure is ruled out.
- Retina and macula conditions
Conditions affecting the layer at the back of the eye, including macular degeneration and retinal detachment. They are a reason for a fuller examination rather than a refraction test.
- Diabetic eye disease
Changes in the retina caused by diabetes. It changes both how often eyes should be screened and how a refractive result is likely to behave, so it is asked about before surgery.
- Eye infections, allergies and injuries
Conjunctivitis, styes, allergic eye disease and injury to the surface of the eye. Most are not refractive questions, and some of them need to be seen urgently rather than booked.
Subject pages in the knowledge base
- Eye conditions & diseases
Dry eye, cataract, glaucoma, keratoconus, retinal and diabetic eye disease explained: what each condition is, how it is diagnosed, and why some of them change which vision correction options are open to you.
- Vision problems & prescriptions
Short sightedness, long sightedness, astigmatism and presbyopia explained in plain language, including why each one happens, how it is measured, and which of them laser vision correction can and cannot change.
Questions answered on these subjects
Guides that cover these subjects
- The eye examination before surgery
What each test measures, and why a refraction on its own is not enough.
- Am I a candidate for SMILE Pro?
The factors an assessment settles, and why no page can decide suitability for a particular eye.
- Risks and side effects
A balanced account of what can go wrong, from the common and temporary to the rare and serious.
- The vision knowledge base
Every question the site answers about eyes and vision, grouped by subject, with a search box.
Rare inherited retinal dystrophies, paediatric syndromes and neuro-ophthalmological conditions are outside the coverage of these pages. Where a symptom can be caused by something serious that is not covered here, the page says so and sends you to urgent care instead.
These pages describe subjects, not people. Nothing here is a diagnosis, and none of it replaces an examination by a qualified ophthalmologist.