Along with dry eyes, night vision problems are another side effect you may experience following laser eye surgery. Issues typically decline over the first 6 months following your surgery and the vast majority of people manage without any difficulties. The problem is more likely if you’ve been treated for high prescription strength.

Night vision problems are caused by higher-order aberrations which can be made worse during laser eye surgery.

Higher-Order Aberrations Explained:

During a standard eye test, your optician’s equipment will typically only measure your low order aberrations which include short-sightedness (myopia) long-sightedness (hypermetropia) and astigmatism. These account for about 90% of your prescription (blurriness) and are easily corrected using contact lenses, glasses or standard laser eye surgery.

However, virtually every eye also suffers from other types of optical errors (blurriness) called higher-order aberrations (the other 10%). These optical errors are not measured during a normal eye test.

These higher-order aberrations are typically responsible for vision problems such as glare, starbursts and haloes around lights. They cause problems especially in low light situations such as driving at night. Some people’s eyes will naturally have a greater amount of higher-order aberrations than others and this is the reason some people suffer from night vision problems. Generally speaking, higher-order aberrations have very little effect on your day time vision. This explains why you could have perfect vision yet really struggle with night time driving. Your optician will tell you that your vision is perfect (remember your optician is only checking your lower-order aberrations) yet you find that you struggle with night vision.

How Are Higher-Order Aberrations Related To Laser Eye Surgery?

As explained above, higher-order aberrations result in problems with night vision and night vision problems are associated with laser eye surgery. But how are the two connected?

During laser eye surgery the central part of your cornea )(the optical ablation zone) is reshaped to eliminate your prescription but it is not practical to reshape your entire cornea as this would involve removal of too much tissue and cause potential weakness in the surface of your eye.

Beyond this central zone, your cornea reverts back to its full prescription (what it was before your surgery) and this can become a problem in low light levels. During the day your pupils are small and so your vision will be perfect, however as the light levels reduce your pupils enlarge. If your pupils dilate beyond the optical ablation zone, you will experience night vision problems.

LASEK v LASIK: Night Vision Problems

It is generally accepted that LASEK patients experience slightly less night vision problems compared with LASIK patients, although the differences are not major. The reasons why this is the case are:

• LASIK can cause night vision problems by the mild swelling of the corneal flap. There is no flap created with LASEK. This is less of a problem with Intralase LASIK as the flap created is more accurate and thinner.
• With LASEK, a larger area can sometimes be treated as you are not confined to the size of the flap. This is better for people with larger pupils.
• LASEK is considered to be a surface treatment whereas during LASIK the laser treats deeper layers of the cornea. Surface treatments (LASEK) can sometimes result in less night vision problems.

These factors should be discussed at your consultation. Your surgeon will help you make the best decision on the most beneficial treatment for you based on your pupil size, prescription and corneal thickness.

Wavefront Laser Eye Surgery & Night Vision Problems:

Recent developments now mean that your laser eye surgeon can accurately measure your higher order aberrations using a Wavefront aberrometer. If you are found to already have a large amount of higher-order aberrations or if you have large pupils your surgeon may insist that you have Wavefront laser eye surgery.

The measurements taken from the Wavefront aberrometer can be used when your eyes are being lasered. So as well as correcting your long-sightedness, short-sightedness or astigmatism (as with standard laser eye surgery) the laser is programmed to deliver a much more complex laser pattern. This surgery will greatly reduce or eliminate your higher-order aberrations as well as your normal prescription. For more information on Wavefront, you can click here.

* It is important to mention that the latest generation of lasers has used this acquired Wavefront data when developing their laser ablation profiles. This means that in many cases the results of laser eye surgery can be just as good with standard treatment as they are with Wavefront surgery.

How Does Wavefront Reduce Your Higher Order Aberrations?

• It can minimise the normal increase in higher-order aberrations that frequently accompanies standard laser eye surgery.
• It can reduce the higher-order aberrations that your eye already had prior to laser eye surgery.

Summary:

The vast majority of people notice very little difference in their night vision following laser eye surgery and those that do typically find it disappears over the 3-6 months following the procedure. Any issues with larger pupils and current night vision problems can be discussed during your consultation with your Surgeon.