Quality vision with LASIK surgery

Aberrations after a LASIK eye surgery still one of the most controversial topic to study. However, some time can be prevented!

Today successful procedures are beyond medical outcomes, in fact some physicians take patient satisfaction into consideration to determine whether it was a successful surgery or not. Since the advent of Wavefront technology to LASIK industry many doctors feel so confidants performing this procedure, that some of them have begun to guarantee 20/20 vision. The main reason is because they can now correct not only Lower-order aberrations but also High-order aberrations, delivering superior results and increasing patient satisfaction.

The vast majority of LASIK physicians agree that technology matters; because the latest tech provides access to more data details, therefore better outcomes in the end. But certainly it is hard to be always on top of the tech because due to the high demand of this procedure new medical devices appear often into the market, leaving "obsolete" the previews generation of devices. But for many reasons not every surgeon want to be on top with the latest tech, in fact remains a large percentage of doctors in the country who do not have the latest technology. But how important is this from patient perspective? When many patients who have had LASIK surgery they never knew what kind of technology was used with their surgeries. I believe it could be caused by the lack of patient interest! But over the years people want to know more details about LASIK surgery particularly because they have heard many bad rumors and in some cases even myths. In fact there are many websites providing a wrong message to the respective potential patient, which in the end creates fear and distrust.

20/20 is more than number or more than you can read at 20 feet a letter that most human beings should be able to read at 20 feet. 20/20 means quality vision means sharp and clear, and as you know 20/20 is part of a metric vision scale. In this scale we can find 20/10, 20/15, 20/20, 20/25, 20/30, 20/40, 20/50, 20/70, 20/100 and 20/200, as appears on the following vision chart shown below:

eye chartBut in order to understand better this metric vision scale, we will stop briefly to complement this information with the following:
When a interested person become an "official LASIK patient", the doctors must complete with accurate information patient's chart in order to provide the right treatment and eventually patient's follow up. And so eventually (a day after the procedure) the patients need to read the eye chart to determinate his/her visual acuity, they may receive the good news of 20/20 vision achievement in the end, but what about if the patient misread one letter in that line, would that be considered 20/20 vision? Yes it would, even though the patient did not read well the entire 20/20 line, however in the chart would be written as (20/20 -1).
Now if the patient misread two letters; that would be written in his/her medical chart as (20/20 -2). In case that misread three or more letters the patient will be move to the line above, in this case (20/25).
This practice could be applied backwards too, in other words if the patient can read well the 20/20 line but also one letter below the line 20/20, in this case (20/15), that could be written as (20/20 +1), if can read two letter would be written as (20/20 + 2) but if he/she can read more than two letters would be moved to the line below, in this case (20/15). And so all these number; 20/20 -1, 20/20 -2, 20/20 +1, 20/20 +2 are considered as a 20/20 vision. The most common misread in the metric vision scale chart are on C, G, O, E, B, F and P. Hence, the eye chart should be considered not only as a tool to measure patient's visual acuity but also to transcribed patient's vision quality.

Let's talk about quality vision!

Patient education as well as patient expectations have a very important role in the entire process, in fact most of the people who are complaining about loss quality vision, they compare inappropriately two different things, showing deficiency in one of the two previous points. For instance; a patient that has a refraction of -2.00 -1.25 x 90, means sphere is -2.00, cylinder is -1.25 and axis is 90. Which means the patient is myopic, in other words he/she has blurry vision to see distance but also distorted vision, and we can guarantee that this patient can not "recognize a person" 5 steps away from him/her with out glasses or contact lenses, in fact any body who have two or more diopters in their glasses, are technically unable to recognize a face 5 steps away from them. But most patients who live with this reality can certainly be corrected with glasses or contact lenses up to 20/20, or even better.

Now in some cases some patients who are complain about loss quality vision after a LASIK procedure, compare their previews quality vision with glasses or contact vs. quality vision after LASIK surgery, instead of comparing before LASIK surgery quality vision and after LASIK surgery quality vision, and both with out glasses. So lets say that the same patient after the surgical treatment has a refraction of -0.25 -0.75 x 130 instead of -2.00 -1.25 x 90, that means the patient definitely improves his/her quality vision, but if he/she compares his/her glasses or contact lens quality vision, which is probably 0 0 0 vs. -0.25 -0.75 x 130, it wont show any improvement.

Now if any doctor said "you vision will be exactly the same than when you wear glasses or contact lenses", simply is not true, especially those patients who have astigmatism, because astigmatism is located on the cornea but also could be on the intraocular lens, that means the laser corrects the surface but nothing inside of the eye. In other words if the patient has a total astigmatism of -1.75, and -1.50 is in the cornea, but -0.25 is in the intraocular lens, that means patient will still having astigmatism after a LASIK procedure any how. But it is important to recognize that in some cases residual astigmatism does not mean blurry vision, especially when it comes to minor astigmatism, in fact many patients with minor residual astigmatism can read 20/20 vision line without problem. Even though glasses correct most of the time total astigmatism not part of it, makes sense to achieve better quality vision with glasses rather than achieved it with LASIK.

Excimer Laser Calibration and its consequences

The most important steps previous to LASIK surgery is the calibration of the Excimer Laser. This critical step is ignored by most of the patient but it is not overlooked by professionals for sure. Actually it is considered as important as the same procedure because no matter how good the physician skills are, if the laser is not calibrated properly, the patient could experience unsatisfactory outcomes any how. The simple reason is because the calibration provides the essential information to guide the Excimer laser in the power of the pulses within a certain distance.

The following video will show the calibration of an EC-5000CX III Excimer Laser. This Excimer machine is approved by the FDA to treats: Myopia, Hypermetropia and Astigmatism, however it is important to mention that regardless of what kind of Excimer Laser is used to perform the procedure all of them has in common this critical step.

Video Interpretation: First of all, there is a device connected to the Excimer Laser machine with a flat surface, which allow the technologist to put a square surgical plastic in order to deliver Excimer Laser pulses, the surface has to be perfectly level for optimal results. Once the surface is level, the professional can proceed to point the laser to the square plastic located in the same surface, and try to align the two light lines and make them one, only then the pulses should be delivered to the surgical plastic plate. As soon as the laser finish its process, the technologist can proceed to remove the plastic and read it with a device called Lensometer, to determinate how accurate were the laser pulses, then base on what the lensometer shows, the technologist must to introduce the information to the Excimer Laser computer, in order to tell the machine how to make the arrangements to power those pulses, this process needs to be repeated as many time as necessary in order to have accurate and optimal surgical outcomes. A job well done, can certainly reduce over-correction and under-correction risk!

It is important to mention that a few other factors need to be consider for an optimal surgery performance, in other words more than surgical skills and experience of the physician, technology also plays an important role which can not be ignored.

Simulating 20/20 vision quality

vision simulation

Other Excimer Laser calibration examples

Bottom Line

Quality vision and satisfaction makes a big impact on final consumers, hence still considered a challenge due to the lack of the latest Tech called (Wavefront) on many practitioners. In other words they are able to treat only the most common refractive errors called Lower-order aberrations such as (Myopia, Hyperopia and Astigmatism) but not High-order aberrations which are unique to every eye, such as (halos, starbursts and glare). At the same time the lack of patient's educative interest complement also to this challenge, that is why many resources encourage to potential patients to take a step back for a moment and see the all picture of the entire process for better understanding and additional confidence.

Page updated March 14, 2011