Most people who have radial keratotomy (RK) surgery gradually become more farsighted for at least 8 to 10 years after surgery. This is called the hyperopic shift. It is not yet clear what causes the shift, how long it may continue, or how significant it may become.

The effect of the hyperopic shift depends on the person's age and whether the person is nearsighted or farsighted after the surgery:

• People who are still slightly nearsighted after surgery (undercorrected) may find that their distance vision improves gradually as the hyperopic shift occurs.
• People younger than 35 may not notice the hyperopic shift, because their eye can adjust to the change.
• People older than 35 may develop presbyopia sooner as a result of the hyperopic shift and may need reading glasses by age 40 to 45.