What Is ReLACS? Laser-Assisted Cataract Surgery Explained
Medically reviewed by Dr. Sohel Somani, Co-Medical Director, U Vision Group.
Many people arrive at a cataract consultation having searched for “laser cataract surgery” online, unsure what the term actually describes. At Uptown Eye Specialists we call the procedure by its proper name, ReLACS — short for Laser-Assisted Cataract Surgery. It is a way of performing parts of cataract surgery with a computer-guided femtosecond laser rather than entirely by hand. This guide explains what ReLACS is, which steps the laser performs, how it differs from traditional manual surgery, and where its real advantages and limits lie. Our aim is not to sell you a technology but to help you understand it well enough to ask good questions and make a decision that fits your eyes and your priorities.
What ReLACS actually is
A cataract is the clouding of the eye’s natural lens, which sits behind the coloured iris. Cataract surgery removes that cloudy lens and replaces it with a clear artificial lens, called an intraocular lens or IOL. In traditional surgery, the surgeon makes the entry incisions, opens the front of the lens capsule, and softens the cataract using handheld instruments and ultrasound. ReLACS uses a femtosecond laser — an extremely fast, precise laser guided by detailed imaging of your eye — to perform several of those steps before the surgeon completes the operation.
It is worth being clear that ReLACS is not a different operation. It is the same fundamental procedure, with a laser handling certain steps that were historically done by hand. The surgeon remains fully in control throughout, and the laser is a tool that adds precision and reproducibility to specific, well-defined tasks.
The “femtosecond” in femtosecond laser refers to the extraordinarily short bursts of energy it delivers — pulses measured in quadrillionths of a second. That speed is what allows the laser to work with great accuracy while transferring very little heat to the surrounding tissue. Before the laser is used, the surgeon captures a detailed three-dimensional image of your eye, which maps the cornea, the lens, and the structures around them. The laser then works to a plan built from those measurements, rather than to a freehand judgement made in the moment. This combination of imaging and laser precision is the heart of what distinguishes ReLACS from manual surgery.
Which steps the laser performs
The femtosecond laser is used for three main steps. First, it can create the corneal incisions through which the surgery is performed, mapping their length and depth to a plan built from images of your eye. Second, it performs the capsulotomy — the circular opening in the front of the lens capsule through which the cataract is removed and the new lens is placed. A laser-made opening is consistently round and centred, which helps the new lens sit in a stable, predictable position. Third, the laser softens and segments the cataract itself, so that less ultrasound energy is needed to break it up and remove it.
For patients with astigmatism — a cornea shaped more like a rugby ball than a sphere — the laser can also place precise relaxing incisions to reduce that astigmatism during the same procedure. Our team has published on how these incisions are planned; you can read the underlying nomogram work in the peer-reviewed literature.
How it differs from traditional manual surgery
The honest comparison is one of precision and consistency rather than a dramatic difference in the final visual result for most routine cataracts. Both manual surgery and ReLACS are excellent, well-established procedures performed many thousands of times a year. What the laser changes is how predictably certain steps are completed. A laser capsulotomy is more uniform than a hand-made one, and laser softening of the cataract can reduce the amount of ultrasound energy delivered inside the eye.
Our own research speaks to this directly. In a published study of more than 3,000 cases comparing ReLACS with manual surgery, the team examined safety and outcomes across a very large group of eyes — one of the reasons Uptown Eye Specialists is recognised as Canada’s #1 ReLACS volume centre, with more than 100,000 cataract surgeries completed across our team. Evidence of this kind is what allows us to describe the technique honestly rather than promotionally.
One detail patients often ask about is comfort. Because the laser softens the cataract in advance, some people find the overall experience gentler, and the patient experience has been examined formally; a study comparing pain perception between manual and laser-assisted approaches looked at exactly this question. The broader point is that our recommendations rest on data we have generated and published, not on the assumption that newer must mean better. That research-led posture is also why we are comfortable telling some patients that manual surgery is the better fit for their particular eye.
Who tends to benefit most
ReLACS is not automatically the right choice for everyone, and a good consultation will say so. The patients who benefit most are often those having astigmatism corrected, those choosing a premium or specialty lens where lens position matters a great deal, and those with certain anatomical features that make the laser steps especially valuable. For a straightforward cataract with a standard lens, excellent results are routinely achieved with manual surgery, and you should never feel that choosing it is settling for less.
Cost is also part of the picture. The elective part of cataract care is the premium refractive lens upgrade some patients choose to reduce their dependence on glasses, and many people are very well served without it. We explain these options plainly during your assessment so that the choice is yours, made with full information rather than pressure.
It also helps to know who ReLACS is not aimed at. Some eyes have features — very small pupils, certain corneal scars, difficulty staying still, or other conditions — that make the laser steps less suitable, and in those cases manual surgery is simply the right tool. A thorough pre-operative assessment is what sorts this out. The goal is never to fit your eye to a technology, but to fit the technique to your eye. If, after examining you, your surgeon recommends manual surgery, that is a recommendation made in your interest, and the excellent outcomes of manual cataract surgery are well established.
What recovery looks like
Recovery after ReLACS is similar to recovery after manual cataract surgery. Most people notice clearer vision within a few days, with continued improvement over the following weeks as the eye settles. You will use eye drops for a period to control inflammation and prevent infection, and you will avoid rubbing the eye and heavy lifting in the early days. Some people experience temporary dryness or grittiness after surgery; if that is bothersome, it can be assessed and managed, and our colleagues at the U Dry Eye Institute focus specifically on this area when it is more than transient.
A common worry is whether the laser makes recovery longer or more uncomfortable, and the honest answer is that it does not change the overall recovery timeline meaningfully. The healing of the eye depends mostly on the underlying surgery and your own eye, not on which steps were laser-assisted. Whichever approach you choose, attending your follow-up visits and using your drops as directed are the most important things you can do to support a smooth recovery.
Making an informed decision
ReLACS is a precise, well-studied way of performing several steps of cataract surgery with a femtosecond laser. It offers consistency in the capsulotomy and incisions and can reduce ultrasound energy, and it pairs naturally with astigmatism correction and premium lenses. It is not a miracle upgrade that makes manual surgery obsolete, and it is not necessary for every eye. The right decision depends on your cataract, your eye’s anatomy, the lens you choose, and your own priorities. If you would like a clear, no-pressure assessment, you can begin your cataract journey with us or read more about the procedure on our Laser-Assisted Cataract Surgery page. Patients who hope to reduce their dependence on glasses afterward may also wish to explore options with our laser vision colleagues at U Eye Laser Cosmetic.
Frequently asked questions
Is “laser cataract surgery” the same as ReLACS? Yes. “Laser cataract surgery” is the term many people search for, but the proper name is ReLACS, or Laser-Assisted Cataract Surgery. It uses a femtosecond laser to perform several steps of the operation, while the surgeon completes the procedure and remains in control throughout.
Does ReLACS give better vision than manual surgery? For most routine cataracts, both approaches achieve excellent vision. ReLACS adds precision and consistency to specific steps and pairs well with astigmatism correction and premium lenses. It is not automatically superior for every eye, which is why the choice should be made together with your surgeon.
What part of the decision is optional? The premium refractive lens upgrade — the option some patients choose to reduce their dependence on glasses — is elective, and many people are very happy without it. We explain the options plainly during your assessment so the decision is yours.
How long does recovery take? Most people notice clearer vision within a few days and continue improving over several weeks. You will use eye drops for a period and avoid rubbing the eye and heavy lifting early on. Any persistent dryness can be assessed and managed.
Medical disclaimer. This article is for general educational purposes only and is not medical advice. It is not a substitute for a professional assessment, diagnosis, or treatment from a qualified eye care provider. Every patient is different — individual circumstances vary, and the information here may not apply to your situation. Any outcomes described are general and are not a guarantee of results. If you have questions or concerns about your eyes or vision, please speak with a qualified eye care professional or book an assessment with us.