This will probably be part 1 of my research into getting LASIK surgery to correct my hyperopia (also called hypermetropia or farsightedness) combined with some mild astigmatism.
Why are you writing this? You are not a doctor
I am strong believer in doing your own research before making any important decision and trust me LASIK (laser in situ keratomileusis) surgery can either change your life in the best case scenario or worst case you could end up blind. I am not a doctor but soon discovered that Hyperopia (farsightedness) combined with astigmatism is a complicated surgery that has a documented high number of regressions and actually worse outcomes than surgery for myopia (nearsightedness). So I have decided to put this together to share my findings and help you make an educated decision, you should do your own research and not take my word or anything I wrote here as medical advise.
Let’s review the core concepts
What is Hyperopia/Hypermetropia: It is a common type of eye refractive error (aka farsightedness) where distant objects may be seen more clearly than objects that are near. (read more facts about this from U.S. department of health)
What is Astigmatism: Astigmatism is a common type of refractive error. It is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye. (read more facts about this from U.S. department of health)
Reading your eye prescription you may have come across the following terms:
- OD = right eye (“oculus dexter” in latin)
- OS = left eye (“oculus sinister” in latin)
- SPHERE = This indicates the amount of lens power, measured in diopters (D), prescribed to correct nearsightedness or farsightedness. If the number appearing under this heading has a minus sign (–), you are nearsighted; if the number has a plus sign (+) or is not preceded by a plus sign or a minus sign, you are farsighted.
- CYL = This indicates the amount of lens power for astigmatism. If nothing appears in this column, either you have no astigmatism, or your astigmatism is so slight that it is not really necessary to correct it with your eyeglass lenses.
- AXIS = This describes the lens meridian that contains no cylinder power to correct astigmatism. Axis is a number between 1 to 180, 90 corresponds to the vertical meridian of the eye and 180 corresponds to the horizontal. If your prescription has CYL power it must also include an axis value.
A diopter (D) is a measure for the refractive (light-bending) power of a lens, Sphere and Cyl are measured in diopters for vision correction/prescription. To illustrate this better:
Some additional acronyms relevant to this topic and clinical trials of LASIK:
- UCVA = Uncorrected visual acuity (vision with no glasses or contacts)
- BSCVA = Best spectacle-corrected visual acuity (what’s the best results you can get when wearing eyeglasses or contacts)
Let’s talk about 20/20
You may have heard about having the perfect vision is to have 20/20, the fact is that there is actually better vision than 20/20. Some animals like eagle have five times better vision than humas, meaning they have 20/5 or 20/4 vision under ideal viewing conditions. But let’s not talk about eagles and talk about the numbers. Where the heck did 20/20 come from? The answer is the Snellen chart.
You may have seen this chart before at the DMV when you go get your drivers license. As long as you are able to read up until the line 8 on the chart above you would be considered to having 20/20 vision without need for glasses. If you can read the smaller lines at the bottom of that chart congratulations, you have better vision than most of us.
20/20 vision means that you are able to see the same line of letters at 20 feet that a person with normal vision sees at 20 feet (thus 20/20). Having 20/40 vision means you see at 20 feet what a person with normal vision sees at 40 feet.
Now that the core concepts are out the way, I will continue my LASIK discussion on the next page.