Cataracts are something we will all have to deal with at some point in our lives. While cataract surgery is not required, the vast majority of individuals will opt to have cataract surgery to improve their vision.
With cataract surgery being so common, it is beneficial to know what different options exist for cataract surgery and what to expect with surgery.
What are Cataracts?
To begin, it may be helpful to have some idea as to how vision works. In order to have clear vision light rays must come from a source (whatever you are looking at) and be bent (refracted) so that the light rays converge as a point source on the back most structure of the eye called the retina.
There are two major contributors used to refract light—the cornea (the front most structure of the eye) and the crystalline lens.
The crystalline lens is located roughly at the center of the eye. The lens is surrounded by a capsular bag, which is held in place by thin fibers called lens zonules.
This arrangement makes the lens flexible, allowing for a process called accommodation.
Accommodation is important because it allows us to see clearly at a variety of distances. If the lens was not flexible (i.e. no accommodation) light would only be focused properly at one set distance; we would then need an outside source to focus light at different distances.
In the natural state looking at a distance object, the lens zonules are held taught. When looking at an object up close, the lens zonules are relaxed, allowing the lens to expand forward. When the lens expands forward it becomes more powerful, thus refracting the light from the near object correctly onto the retina for clear near vision.
For example, in an individual with no accommodation, his or her vision may be perfectly clear for a distance of 10 feet. If this individual wanted to read a book at 25 inches from his or her face, they would be unable to do so, as the incoming light rays from the book would be coming to a focus point “behind” the retina.
Unfortunately, as we age the lens loses its flexibility in a process called presbyopia. Presbyopia begins around the age of 45 and progresses until reaching 0 around the age of 65. At this time, presbyopia cannot be avoided nor corrected, and individuals will need reading glasses to see up close.
Another age-related change that occurs to the lens is the development of cataracts.
The lens is shaped similar to an onion. Since we cannot have cells shedding off and floating around the inside of the eye (this would interfere with vision) the cells of the lens are withheld for life. The center of the lens is called the lens cortex and is formed during fetal development.
However, new lens cells are also constantly being made. Lens cells are called lens fibers. They grow from the equator of the lens and elongate outward to encompass the cortex. This process occurs continuously throughout life, creating more and more layers.
Over the years, the original lens cortex hardens, opacifies, and can take on a yellowish hue. This change is called a nuclear sclerosis, which is the most common type of cataract.
Cataracts interfere with vision. Cataracts make colors look yellower, can decrease vision, change glasses prescription, increase glare and halos around lights, and even make thinks appear duller or darker in general.
Cataracts are typically slow growing. Therefore, many individuals may not notice the gradual cataract-induced vision changes mentioned above and can go many years prior to needing treatment.
Like presbyopia, there is currently no way to prevent cataracts from forming. Fortunately, however, there is a treatment for cataracts—cataract surgery!
What is Cataract Surgery?
During cataract surgery, an ophthalmologist removes the natural lens and replaces it with an artificial one.
The surgeon starts by opening the front lens capsule (the bag that holds the natural lens). He or she then uses a special tool that vibrates at a high frequency to break apart the cataract-ed lens into small fragments. This technique is called phacoemulsification.
Once the lens is broken into small pieces, a button is pushed on the tool and it turns into a small vacuum, which collects the lens fragments and sucks them out of the eye.
Once all pieces of the natural lens are removed, the artificial lens is placed into the capsular bag.
The artificial lens chosen to replace the natural lens varies in power and therefore is chosen to best correct the patient’s vision.
One important note to make with cataract surgery is that, no matter what type of lens is chosen to replace the natural lens, post-cataract surgery the patient will have no accommodation left.
Individuals who have cataract surgery prior to reaching presbyopia should be warned about this, as once accommodation is gone, it cannot be returned.
Types of Artificial Lenses
There are currently many different options for cataract surgery. Your surgeon will take several different measurements and tell you what options may be best suited for you as not everyone qualifies for all types of lens implants. Prescription, ocular anatomy, visual needs/expectations, and co-morbidities must all be taken into account when selecting a lens implant.
To date, there are two major categories of artificial lenses—monofocals and multifocals.
Monofocal lenses create one clear focal point. Glasses or contacts are then needed to see at other distances.
Many individuals choose to have their distance vision corrected with monofocal lenses and then wear reading glasses for near work. However, near vision or an intermediate working distance (computer work) can be chosen instead, and distances glasses worn when needed.
Monovision is another option that can be accomplished with monofocal lens implants. In monovision, one eye is set to see well at distance and the other eye is set to see well up close.
Monovision is not for everyone, however. Some individuals complain of headaches or simply cannot adapt to the difference in prescription between the two eyes. For this reason, if monovision is something a patient is potentially interested in, the surgeon will likely recommend simulating the situation with contact lenses first.
Multifocals, on the other hand, have multiple focal points. This means they can have a range in clear vision—typically decent distance vision and some near.
There are many different types of Multifocals available. The type of multifocal determines exactly how wide the range of vision is. Generally speaking, one can expect a range of vision that is good at distance up to about 60 cm away (computer distance). Reading glasses will likely still be needed for when reading a book or using a cell phone with small font.
While Multifocals can be very helpful, they are also not perfect. It is good to have realistic expectations with them. With Multifocal lenses some give-and-take is expected. You will not have crystal clear vision at distance, intermediate, and near. You will have good vision at these distances, but it likely will not be as good at these individual distances as it would be in a monofocal setup.
Thus, if crystal clear vision is important to you at distance—say you’re an airplane pilot or baseball game announcer—a monofocal lens set to distance with reading glasses for up close may be a better option for you. This goes vice versa for those who need impeccable near vision. For example engineers, architects, or seamstresses, may prefer monofocal lenses set for near with distance glasses to wear when not at work.
However, new artificial lenses are being approved each and every year. While the “perfect” multifocal lens implant may not yet exist, they do seem to approve with each new generation of production.
Whatever the case, there are many different options for lens replacement. If you or someone you know suffers from cataracts, be sure to talk with your eye doctor as he or she would be happy to help discuss different options with you.