If you are considering vision correction surgery, you may already know your current glasses or contact lens prescription. But one number matters almost as much as the prescription itself: how long it has stayed stable.
At Valley Laser Eye Centre, we look beyond what your prescription is today. We want to understand how your eyes have changed over time. For many forms of refractive surgery, a stable prescription helps us plan treatment accurately and reduces the likelihood that natural prescription changes will affect your results soon after surgery.
As a general guide, we often want to see that your prescription has remained reasonably stable for approximately 12 months before certain vision correction procedures. However, there is no single rule that applies to every patient or every surgery.
Your age, eye health, type of refractive error, corneal measurements and the procedure being considered all matter.
What Does A Stable Prescription Mean?
A stable prescription does not necessarily mean that the numbers on two eye exams have to be absolutely identical.
Small variations can occur because of testing conditions, dry eyes, contact lens wear and other temporary factors. What we are primarily looking for is evidence that your underlying refractive error is no longer changing significantly.
Your prescription may include measurements for:
- Sphere, which represents nearsightedness or farsightedness
- Cylinder, which represents the amount of astigmatism
- Axis, which describes the orientation of astigmatism
For procedures such as Implantable Contact Lens surgery, a commonly used benchmark is no more than approximately 0.50 dioptres of refractive change over one year.
This is a guideline rather than a substitute for a full assessment. We review your prescription history alongside detailed measurements of your eyes before determining whether surgery is appropriate.
Why Does Prescription Stability Matter?
Vision correction surgery is planned using measurements taken before your procedure.
If your underlying prescription is still changing, surgery can successfully correct the prescription you have today while your eyes continue to change afterward. That could leave you with some degree of nearsightedness, farsightedness or astigmatism again in the future.
For example, myopia occurs when the eye’s focusing system causes light to come to a focus in front of the retina, commonly because the eye is too long or the cornea is relatively steep. If the eye is still developing and the myopia is increasing, treating too early may not provide the long-term stability we want.
Similarly, hyperopia occurs when light would naturally focus behind the retina, often because the eye is shorter or its focusing power is insufficient.
Our goal is not simply to correct today’s numbers. We want to develop a vision plan that makes sense for your eyes over the longer term.
How Long Should Your Prescription Be Stable?
For many younger adults considering refractive surgery, approximately one year of prescription stability is an important starting point.
That does not mean everyone becomes a surgical candidate as soon as 12 months have passed. We also consider:
- Your age
- The size and direction of previous prescription changes
- Corneal thickness and shape
- Eye surface health
- Your degree of myopia, hyperopia or astigmatism
- The health of the retina and other internal eye structures
- Your natural lens
- Your lifestyle and visual priorities
Someone whose prescription changed substantially 13 months ago and has only recently settled may require a different approach from someone whose prescription has been almost unchanged for several years.
A comprehensive vision correction consultation allows us to put those numbers into context.
Why Are Younger Patients More Likely To Have Changing Prescriptions?
Refractive errors frequently develop or progress while the eyes are still growing.
Myopia in particular can continue to change through the teenage years and sometimes into the early twenties. For that reason, reaching adulthood alone does not automatically mean your prescription is ready for surgery.
Some people reach a stable prescription relatively early. Others continue noticing changes into their twenties.
This is one reason we ask about previous glasses and contact lens prescriptions rather than relying entirely on your latest eye examination.
Regular examinations are also important. If you have several years of records available through your optometrist, they can help demonstrate how your vision has changed over time. Valley Laser Eye Centre works with a trusted network of optometrists throughout British Columbia to support assessment and follow-up care.
Does Prescription Stability Matter For Every Procedure?
Yes, but the way we interpret prescription stability depends on the treatment.
PRK
PRK corrects refractive error by precisely reshaping the cornea with an excimer laser after the surface epithelium has been removed.
Because treatment is calculated from your refractive measurements, we want confidence that those measurements represent a stable prescription.
PRK can be considered for patients with myopia, hyperopia or astigmatism when their corneal structure and other measurements support treatment. It is also a tissue-conscious option that can be considered for some patients whose corneal characteristics make other approaches less suitable.
Recovery is more gradual than with some procedures. The surface epithelium heals first, while visual clarity continues to improve and stabilize over the following weeks and months. Our article about PRK recovery and long-term stability explains this process in greater detail.
Valley Laser Eye Centre no longer performs LASIK because of concerns about its long-term safety profile. You can learn more about that decision and the alternatives we use on our LASIK information page.
Implantable Contact Lens Surgery
An Implantable Contact Lens works differently from PRK. Instead of removing corneal tissue, we place a prescription lens inside the eye while leaving your natural lens in place.
ICL can be particularly useful for moderate to high myopia and for some patients whose corneas are not well suited to laser correction.
Prescription stability is still important because the power of the implanted lens is selected according to your refractive needs.
Your prescription is only one part of ICL candidacy. We also take precise measurements inside the eye and evaluate whether there is adequate space for the lens.
Refractive Lens Exchange
Refractive Lens Exchange removes the eye’s natural lens and replaces it with a carefully selected artificial lens.
RLE is often considered in adults experiencing presbyopia, the age-related loss of the natural lens’s ability to focus at close distances. It may also be appropriate for certain stronger prescriptions or age-related lens changes.
Because RLE replaces the natural lens itself, its candidacy considerations differ from those for corneal procedures in younger patients. Age, focusing ability, lens health, prescription and visual goals are all considered together.
What If Your Prescription Is Still Changing?
A changing prescription does not necessarily mean vision correction will never be an option. It may simply mean that now is not the right time for a particular procedure.
If we identify continuing refractive changes, we may recommend monitoring your eyes until there is enough history to determine that they have settled.
Waiting can be frustrating when you are eager to become less dependent on glasses or contacts, but accurate timing is an important part of responsible surgical planning.
We believe in transparency and personalized vision planning, not rushing someone toward a procedure.
What About Prescription Changes After Age 40?
Not every change in vision after 40 means your distance prescription has become unstable.
One of the most common changes is presbyopia. The natural lens inside the eye gradually becomes less flexible, making it harder to focus on close objects. You may notice yourself holding menus farther away, increasing the font size on your phone or relying increasingly on reading glasses.
Presbyopia is different from the eye growth that can cause progressive myopia in younger people.
Later in life, changes to the natural lens can also be associated with cataracts. A cataract develops when the natural lens becomes cloudy and can sometimes cause prescription changes before other symptoms become obvious.
In these situations, the appropriate solution may be Refractive Lens Exchange or, when a cataract is present and affecting vision, cataract surgery rather than corneal vision correction.
How Do We Determine Whether Your Eyes Are Ready?
Prescription stability is one part of a much larger assessment.
During your consultation, we evaluate your prescription history and perform detailed diagnostic testing to understand the structure and health of your eyes. We also discuss your work, hobbies, driving needs and expectations for vision after treatment.
You can read more about the process in our guide to what happens at a vision correction consultation.
This detailed approach helps us determine not only whether surgery is appropriate, but which procedure makes the most sense for your individual eyes.
Take The Next Step With Confidence
You do not need to determine on your own whether your prescription is “stable enough.”
Bring your current prescription and, when available, information from previous eye examinations. We can review how your vision has changed, complete the necessary measurements and explain your options clearly.
At Valley Laser Eye Centre, our approach is built around careful diagnostics, evidence-based treatment and personalized surgical planning. If your eyes are ready for vision correction, we will explain which options may be appropriate. If waiting is the safer choice, we will explain that too.
Book a consultation with Valley Laser Eye Centre to find out whether your prescription is stable and explore the vision correction options that may be right for you.
