11 Eye Tests Anyone Considering Laser Eye Surgery Should Know
More tests means more understanding. And more understanding means more detailed treatment plans, greater safety, and better outcomes.
So, when preparing for Laser Eye Surgery, you want a clinic with the most comprehensive eye examination and the longest list of eye tests you can find.
That much is clear.
But if you’re anyone other than an optometrist or specialised eye surgeon, how do you know what qualifies as comprehensive? And what exactly are these tests the process should involve?
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These are tricky questions to answer even when you consult clinics themselves. You’ll quickly find the responses vary from place to place, with some offering thorough eye examinations and being completely transparent about what they include, and others offering the bare minimum and reserving all the details until the cheque is signed.
So, to give you a better idea of what to expect from any Laser Eye Surgery clinic — according to leading experts in the field — here are eleven pre-operative eye tests every screening process should include. The list is by no means exhaustive, but it serves as a valuable starting point to finding clinics that provide a high standard of treatment.
These are arguably the most important screening tools used in refractive surgery. Topography devices measure the curvature (shape) of the front of the cornea, providing valuable information about the health of the cornea both before and after surgery. Tomography devices measure the back surface, as well as the front surface of the cornea and have added another dimension to the diagnostic tool-box. This information can help detect corneal disease before it can be seen by the clinician, most importantly keratoconus, where laser refractive surgery is not safe to perform. Tomographers are considered to be “standard-of-care” for screening refractive surgery patients due to the additional information provided by measuring both surfaces rather than only measuring the front surface.
Refractions, including manifest refraction and cycloplegic refraction
A manifest refraction test is normally given as part of a routine eye exam. It’s the typical test you imagine: looking through different strength lenses and reading letters or symbols on a chart. Cycloplegic refraction takes this a step further, measuring your full refractive error by using drops to relax the focusing muscles of the eye.
A slit-lamp exam involves using a microscope and a high-intensity light beam, to assess the cornea and look for diseases or abnormalities in the anterior portion of the eye, including the eyelids, conjunctiva, iris and lens.
Dilated eye examination
A dilated eye examination allows the optometrist to have a wider field of view at the back of the eye, to more thoroughly assess the optic nerve and retina.
Although it exhibits no warning signs, high pressure within the eye can cause serious damage to the optic nerve. Tonometry is the measurement of intraocular pressure by using either a non contact tonometer (instrument to blow a tiny puff of air onto the eye to measure the change in light reflected off the cornea) or a contact tonometer which requires the use of anaesthetic drops in the eye first.
A contrast sensitivity test involves looking at grey stripes, shapes, or letters at ever reducing contrasts, and measuring your ability to distinguish them from the colour of the background. It’s particularly important to establish how well your eyes function in situations of low light, glare, fog, or when the contrast between objects and the background is reduced.
Night vision simulation
In this test, the optometrist asks you look at a computer simulation of common night vision disturbances, such as halos and starbursts, to assess how your vision is affected by night glare. This helps them 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 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.
Pupillometry is the measurement of pupil size and reactivity. An accurate test involves using an infrared camera to measure average pupil size, variation in pupil size, and the difference between the two in different light levels, including in the dark where you pupils are largest.
The measurement of corneal thickness or pachymetry is used to determine 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.
Wavefront analysis measures the most minute imperfections (higher order aberrations) in your vision that are not even corrected by a standard glasses prescription. Clinicians do this using a wavefront aberrometer to create a 3D map of the ‘wavefront’ of your eye, and then feeding the data into your overall treatment plan.
Have a question about the screening process for Laser Eye Surgery? Ask us in the comments below or get in touch with one of our Patient Care Coordinators today.