The Reason For Loss Of Near Vision After Cataract Surgery
Having cataracts removed can lead to beautiful changes in vision. But at the same time, cataract surgery can really muddle with the prescription of the eye. For many, this means the wonderful ability to see off in the distance without glasses. But this may come with a cost of the loss of reading vision after cataract surgery.
After cataract surgery, a new artificial lens is placed within the eye to replace the function of the natural lens turned cataract. Typically calculations set the focus of this new lens for the distance. While there are some lenses which can provide up close vision, the standard single focus or monofocal variety of lenses are incapable of providing both distance and up close vision.
This rigid lens just doesn't function the exact same way that our natural lens used to be. Because of this, most people will need reading glasses after cataract surgery in order to read up close.
What Determines The Prescription Of The Eye
Some people are naturally nearsighted. These individuals are able to see up close their entire life, they just have trouble seeing off in the distance.
Some people are naturally farsighted. When young, these individuals typically can see well both in the distance and even up close. How? For those farsighted individuals, the natural lens inside the eye is able to focus through that farsighted prescription and also focus up close at the same time.
Eventually, as that natural lens becomes inflexible through a process called presbyopia, that up close vision first becomes blurry and then even the distance vision can become blurry.
Even the nearsighted folk notice the effects of presbyopia. Those that wear contact lenses will notice their up close vision becoming more blurry and those that wear glasses will start to have to wear progressive glasses (or just simply look underneath the glasses).
The natural lens starts out in life very flexible and allows us to see up close. As this lens becomes inflexible, our up close vision becomes blurry.
Fast Forward To Cataract Surgery
After the natural lens becomes inflexible, it becomes cloudy and turns into a cataract. It is this natural lens (now cataract) which is removed during cataract surgery.
Because the lens contributes approximately one third of our ability to focus light and see, this lens must be replaced with a new artificial lens to achieve the same goal.
But here is the thing: surgeons have the option to choose an artificial lens of ANY prescription or power. So if you were nearsighted before cataract surgery, the surgeon can choose an artificial lens to correct your nearsighted vision and allow you to have great distance vision.
Types of artificial lenses
The biggest difference between artificial lenses and our natural lens is that an artificial lens is made out of a hard biocompatible material such as silicone or acrylic that doesn't change shape. When young, the natural lens can change shape and this allows the natural lens to focus up close.
Not all artificial lenses are created equal. Artificial lenses have been developed to get around this limitation of not being able to change shape. To paint a very broad picture, there are two main types of artificial lenses:
- Monofocal Lenses
- Lifestyle Lenses
Monofocal lenses are the standard option for cataract surgery. These lenses are fully covered by insurance providers (unless you opt for the toric variety to correct astigmatism; see also This Is The Best Cataract Surgery For Astigmatism).
But monofocal lenses are only capable of correcting a single focus. If the surgeon calculates this lens to focus off in the distance, this lens will ONLY focus off in the distance. If the surgeon calculates this lens to focus up close, this lens will ONLY focus up close.
Thus, with monofocal lenses corrected for distance vision, reading glasses are necessary to see up close after cataract surgery.
Generally having the distance vision corrected with these lenses works well and tends to be the default option for cataract surgery. It especially works well for those farsighted individuals who had a hard time with both up close and distance vision prior to cataract surgery.
But for someone who can see fine up close before cataract surgery, exchanging that up close vision for distance vision can be quite jarring.
Some people don't want to wear glasses after cataract surgery. So to fix the issue with monofocal lenses only focusing light one way, lifestyle lenses were invented. These lenses include multifocal lenses and extended focal lenses. Unlike the standard monofocal lenses, these lenses come with out of pocket expenses.
These lenses still can't change shape, so different optical properties were baked into the lens in order to extend our vision without glasses after cataract surgery. Multifocal lenses work by splitting light for distance, intermediate or computer vision and up close vision all simultaneously. Extended depth of focus lenses work by bending light instead. This allows extended depth of focus lenses to cover distance and intermediate vision well with a little bit of up close vision (but not as much as the multifocal lenses).
Each of these variety of lenses has their pros and cons.
Multifocal lenses will have some extra halos, night time vision symptoms and a small reduction in contrast as a result of the splitting of light. These generally improve over the first few months after the procedure. And multifocal lenses can provide full glasses independence.
Extended depth of focus lenses improve upon the night time vision symptoms of multifocal lenses but these lenses don't provide enough reading vision to function completely without reading glasses.
Options To Correct Up Close Vision After Cataract Surgery
By far the easiest option is to run out to the drugstore and pick up some over the counter reading glasses. Reading glasses are cheap and you don't need to wait anytime at all after the surgery before you can wear them. The glasses will come in different powers. See What Is The Best Reading Glasses Prescription After Cataract Surgery? to learn which power is best for you.
Beyond reading glasses, there are still other ways to correct that reading vision
- Bifocals or progressive glasses can be prescribed to cover both distance and reading at the same time. These glasses can be made even if you don't need any prescription to see off in the distance. It's typical to wait at least a month before prescribing glasses to be sure the prescription stabilizes.
- Contact lenses can be used after cataract surgery. Either multifocal contact lenses can be worn to provide the distance and up close correction or a single contact can be used in one eye for up close vision (known as monovision). Again, it is optimal to wait about a month after cataract surgery to use contact lenses.
- Similar to how a single contact lens can be used to focus up close (monovision), the same can be done with laser eye surgery such as lasik or PRK.
- Lastly, it is technically possible to exchange the monofocal lens to a lifestyle lens. However, this lens exchange surgery does carry additional risks and is rarely done to correct up close vision.
The standard monofocal lenses used in cataract surgery are only capable of focusing at a single distance. For most people after cataract surgery, the calculations allow for an improvement in distance vision. But optimized distance vision comes at a cost of blurry up close vision. The optimal way to correct this after surgery is by using simple over the counter reading glasses.
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