25 Feb RxSight LAL
Light Adjustable Lens Cataract Surgery
The RxSight light adjustable lens (LAL) is an intra-ocular lens (IOL) placed in your eye after cataract surgery that achieves a higher level of accuracy than with other IOLs. Higher accuracy equates to better vision without glasses.
A cataract occurs when the lens inside your eye becomes cloudy, making it hard to see. Cataract surgery removes the cloudy lens in your eye and replaces it with an IOL. IOLs come in a large variety of powers. Prior to cataract surgery careful measurements are made to determine the correct IOL power to help you meet your visual needs. For example, if you want to see well at distance without glasses, your surgeon will calculate the IOL power that would bring distance vision into focus without glasses.
Why Do We Need the RxSight Light Adjustable Lens?
We need the RxSight LAL to improve the accuracy of our vision after cataract surgery. Let me explain why. The formulas used to calculate the ideal IOL power are “kind of accurate” which works fine in having vision which is “kind of accurate” is OK with you. Modern IOL calculation formulas use measurements of the length of your eye and the shape of your cornea. Fortunately, modern measurement machines are quite accurate at these measurements.
Another important part of the IOL calculation is where your IOL will sit in your eye. This is a principle of optics which you may have already noticed in your life. If you move your glasses further away from your face or closer in, you will notice that your vision moves in and out of focus. The power of your glasses is the same, but where you hold them affects the focus. It is the same with the IOL that will be placed in your eye. If it sits a bit further back or further forward in your eye, it affects the focus of your eye. We don’t have a way to measure exactly where the IOL will end up in your eye. As a result, the formulas estimate where the IOL will end up based on how most people with eyes like yours heal.
Accuracy of Cataract surgery without the RxSight LAL
Since most people heal in similar ways, we attain moderate levels of accuracy with this technique. In one large data base held by Dr Hill which is the completion of data from hundreds of eye surgeons, about 78% of patients end up within 0.5 diopters of target. This means that only 78% of patients are 20/20 or 20/25 which would be considered good vision without glasses. That leaves 22% with mediocre or even worse vision. The predictability is even worse for patients with previous refractive surgery (LASIK, RK).
This leads to the discussion in the office with goes something like this. “All four of my friends can see far without glasses after cataract surgery, but I can’t see very well without glasses.” What went wrong?” Statistically, someone has to be part of the 22%, or 1 in 5 that have where the IOL position was not as predicted.
Options for those patients include glasses, contact lenses, laser vision correction, or exchanging the IOL for a different power.
Advantage of the RxSight LAL Light Adjustable Lens
The advantage of the Rx Sight LAL is that we place your IOL, wait three to five weeks until it has settled, and then adjust the power of the IOL to give you the focus you desire. In the FDA trial, 98% where within 0.5 diopter. A follow-up study by Hengerer et al found 97% were actually within 0.25 diopters which meant that 100% of patients saw 20/25 or better.1
1. Hengerer F, Dick B, Conrad-Hengerer I. Clinical evaluation of ultraviolet light adjustable intraocular lens implanted after cataract removal. Ophthalmology. 2011;118:2382-2388.
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