11 Eye Tests You Should Know if You’re Considering Laser Eye Surgery

If you’re considering Laser Eye Surgery for the correction of your refractive error, you may well be wondering what happens during your pre-operative screening appointment. More specifically, you may be curious about the level of testing that will be required to determine your eligibility and allow us to create your personalised treatment plan.

At London Vision Clinic, we strongly believe in the importance of transparency and education in the Laser Eye Surgery field. That’s why we strive to make as much information available as possible, both through our comprehensive blog, and your in-clinic appointments.

We also know that more testing means more understanding. Implementing a thorough examination stage allows us to create more detailed treatment plans in addition to improving safety and securing the best possible outcomes. So, when it comes to pre-operative examinations, you want to find a Laser Eye Surgery clinic with the most comprehensive list of eye tests you can find.

But let’s face it: if you’re not an optometrist or specialised eye surgeon, it can be difficult to know exactly what qualifies as “comprehensive”. And that’s without even considering what each of these tests involves and what they’re for!

To give you a better idea of what to expect from your pre-operative Laser Eye Surgery clinic visit — according to leading experts in the field – here are 11 eye tests that every Laser Eye Surgery screening process should include. 


Possibly the most important screening tools used in refractive surgery, topography and tomography are used to take crucial measurements of the eye. While they might sound very similar, there are actually important distinctions between these two tests:

Topography devices are used to measure the curvature of the front of the cornea. This provides your surgeon with valuable information about the health of the cornea both before and after surgery. Abnormal corneal topography is the most important identifiable risk factor for corneal ectasia, a rare complication that can occur following Laser Eye Surgery. Topography is therefore a mandatory pre-operative test.

Tomography devices add another dimension to our diagnostic toolbox. They are used to measure the back surface of the eye, in addition to the cornea. This information can help your doctor to identify corneal disease – such as keratoconus – before it can be detected by a clinician. Tomography is considered to be the standard of care in the screening of refractive surgery patients due to the additional information it provides about both surfaces of the eye.

Refraction Test

A key part of your screening for Laser Eye Surgery is the refraction test. You will likely be familiar with the Manifest Refraction test, which is conducted as part of a routine eye exam to measure your refractive error – e.g., how long-sighted, short-sighted, or astigmatic you are. This typically involves testing out different strength lenses and reading letters or symbols on a chart.

The Cycloplegic Refraction test takes this a step further. It involves the use of eye drops to relax the focusing muscles in the eye, allowing your doctor to measure your full refractive error.

Slit-lamp Examination

A slit-lamp examination is a common test that helps to determine the general health of your eyes. Using a microscope and a high-intensity light beam, your doctor will be able to assess the anterior portion of the eye – including the eyelids, conjunctiva, iris, and lens – enabling them to identify any signs of disease or other abnormalities.

Dilated Eye Examination

A dilated eye exam is performed to increase the size of the pupils to allow your optometrist a wider field of view to the back of the eye. This allows them to more thoroughly assess the health of the optic nerve and the retina. This part of testing is vital for identifying potential eye conditions that could lead to vision loss.

Intraocular Pressure

Despite exhibiting no warning signs, high pressure inside the eye can cause serious damage to the optic nerve. This can be linked to glaucoma. As part of your comprehensive testing, your eye pressure (intraocular pressure) will be measured with a tonometry check.

This involves either a non-contact tonometer (an instrument that blows a tiny puff of air onto the eye to measure the change in light reflected off the cornea) or a contact tonometer which involves using another device to apply pressure directly to the eye. Anaesthetic eye drops are required when conducting a contact tonometer test.

Contrast Sensitivity

A contrast sensitivity test measures your ability to distinguish between ever-reducing increments of contrast (light vs. dark). This is an important measure of visual function and allows your optometrist to establish how well your eyes function in situations of low light, glare, fog, or other instances where the contrast between objects and background is reduced.

Night Vision Simulation

This test provides your surgeon with an insight into how your vision is affected at night. It involves observing your eyes as you look at a computer simulation of common nighttime disturbances, such as halos and starbursts, to assess how your vision is affected by night glare.

This is important as nighttime disturbances, may be induced by Laser Eye Surgery. Night vision simulation allows your surgeon to understand any pre-existing night vision symptoms you may have and to design a treatment plan that maintains or even enhances your quality of night vision after Laser Eye Surgery.

Dry Eye Exam

The Schirmer test, also known as a dry eye or tear test, is used to diagnose dry eye syndrome and test how well your eyes produce tears. It works by simply placing a small strip of paper in the lower eyelid and measuring the amount of moisture gathered on it over a period of a few minutes. Having dry eye syndrome may be a contraindication for Laser Eye Surgery as dry eyes are a common side effect of treatment.


Pupillometry is used to measure the average size of your pupils, the variation in pupil size over a fixed period, and the difference in pupil size between two eyes in different light levels. Accurate pupillometry is crucial for successful Laser Eye Surgery because lasers are only capable of treating a defined area of the eye.

Pachymetry for Corneal Thickness

Pachymetry is conducted to determine the thickness of your corneas to ensure the depth of the thinnest part of the cornea is within safe limits for surgery. The most accurate measurements can be obtained through OCT scanners or very high-frequency digital ultrasound. This provided 3D thickness profiles of the individual layers of the cornea, improving diagnostic capabilities for both pre-operative and post-operative analysis.

Wavefront Analysis

Wavefront analysis, or wavefront aberrometry, allows your doctor to measure the most minute imperfections (higher-order aberrations) in your vision that are not correctable with glasses alone. A wavefront aberrometer detects irregularities that affect the finer quality aspects of your vision, beyond refractive errors. A 3D map of the ‘wavefront’ of your eye can then be fed into the laser during your treatment to achieve even better outcomes.

Why does testing vary from clinic to clinic?

It may come as a surprise to discover that pre-operative testing can vary significantly between clinics. For example, at some clinics, you may be advised to set aside just one hour for the screening appointment. Meanwhile, at other clinics, you may spend the best part of an afternoon undergoing rigorous testing. So, why is this?

Well, sadly, the bottom line is usually cost. Generally, the cheaper the quoted treatment price, the less thorough the screening process. This can lead to a lower standard of safety and less successful outcomes.

When deciding on a Laser Eye Surgery provider, assessing each clinic’s approach to pre-operative testing can be extremely helpful. This can give a clear indication of the clinic’s dedication to providing the best possible treatment.

If you’d like to learn more about pre-operative testing at London Vision Clinic, don’t hesitate to get in touch with one of our friendly clinic coordinators – we’re always on hand to help. Alternatively, Book a Consultation to kickstart your journey to clear vision today.