How is the power of an implanted lens chosen?
From measurements of the length of your eye and the curvature of your cornea, taken before surgery and entered into a formula that predicts the power needed. Because the prediction is not exact, the surgeon will usually aim for a small residual, and will tell you which direction the estimate is likely to fall.
- Subject
- Eye conditions
- Topic
- Cataract
- Kind of question
- Other questions
- Procedures
- Cataract surgery
- Last reviewed
- 22 September 2026
What this answer depends on
- The measurements themselves, and how repeatable they were
- Whether you have had previous laser surgery, which changes the calculation
- What you would prefer the residual to be used for: distance or near
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Where this answer sits
It is one of 483 answers in the vision and eye health knowledge base, filed under Eye conditions & diseases in Cataract . The subject page carries the answers either side of it, and the hub is searchable.
Subjects this question touches
The pages that answer the subject behind the question, rather than the question itself.
- Procedure Cataract surgery
- Procedure Refractive lens exchange (RLE)
- Condition Cataract
- Place Cataract surgery in Dubai
- Place Eye tests in Dubai
This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
General answers cannot tell you what is happening in your own eyes. Only an examination by a qualified ophthalmologist can do that.
Sources & further reading
We prefer primary sources. Where a claim comes from a manufacturer, a single study or a regulator, it is labelled as such below.
- Cataracts in adults: management (NG77)
Clinical guidance on when cataract surgery is indicated, what should be discussed before it, and what follow-up is expected.
Used for When cataract surgery is considered appropriate rather than cosmetic timing; What patients should be told before cataract surgery.
Link checked 23 September 2026
- Cochrane Library
Systematic reviews and meta-analyses. Useful for readers who want to know how strong the pooled evidence is, not just what one trial found.
Used for Helping readers judge the strength of the evidence base.
Link checked 22 September 2026