Within our eye we have a clear lens that allows light to be focused clearly onto the retina. Whenever this lens becomes cloudy, it becomes what is known as a cataract. This loss of transparency results in blurring of our vision, and may interfere with our ability to work, read, or perform activities that we enjoy.
Cataracts normally progress slowly over time, and cause a slow deterioration in our visual acuity and sharpness. Symptoms associated with cataracts include: blurry vision, declining color and object detail, double vision, glare off sunlight or headlights, difficulty reading, and poor night vision. While cataracts are in the early stages of formation, our vision can often be improved with changes in our glasses prescription. However, once our vision deteriorates to a certain level due to cataracts, your doctor will likely recommend a definitive treatment such as cataract surgery.
As mentioned in the previous description of cataract surgery, intraocular lenses (IOLs) are placed within the eye during cataract surgery to provide correction of our vision. The first IOL was successfully placed in the 1940's in England, and since this time IOLs have continued to evolve into the precise implants that we know today. If no replacement lens was placed within the eye, we would need extremely thick glasses to correct our vision after surgery. Thankfully, due to modern medical technology we have lens implants that correct our vision and decrease our dependence on glasses.
When contemplating cataract surgery, we do have some options with regards to the IOLs. Before we discuss the IOL options further, we need to discuss two separate eye definitions. One is astigmatism and the other is presbyopia. Astigmatism is a term that describes a cornea that is curved in one direction more than the other. This leads to a decrease in the sharpness of your uncorrected vision. Just envision the difference between a basketball and a football. When looking down on a basketball, all directions basically slope away evenly from a central point. When looking down on a football from above, one axis is sloped more than the other. Therefore, people with astigmatism have a cornea that is shaped somewhat like a football. It is estimated that around 20 percent of the population has some degree of astigmatism since birth.
Cataract extraction is the most commonly performed surgery in the United States. The surgeries are done on an outpatient basis, meaning you go home on the same day of your procedure. For the cataract procedure, your eye is numbed with either drops only or a small injection of anesthetic medicine around your eye. Once your eye is numbed for surgery, the eye is cleaned with a sterilizing wash and the face is draped with sterile towels. A speculum is then placed to hold the eyelids open during surgery. A small incision which is less than 3mm is made in the cornea to allow for access to the cataract. An ultrasound machine is then used to break the cataract into tiny fragments which are then vacuumed out of the eye. A new lens implant is then passed into the eye through the corneal incision, and is placed within the capsule that surrounded your old lens. This ensures that your new lens implant is held securely in place. After surgery your eye may be patched or shielded, and you will be taken to the recovery area. After a brief stay in recovery, you will be allowed to go home with your friends and family.
The second term to discuss is presbyopia. This is a normal part of life and usually starts around age 45. With aging, our lens becomes less pliable and we lose the ability to read small print up close. You may recognize the onset of presbyopia as the time that you started wearing "reading glasses", had to add bifocals to your normal glasses, or noticed that your arms were not "long enough" to read comfortably.
When having cataract surgery, you may have the option of different IOLs depending on your type of cataract and overall eye health. If you have preexisting astigmatism, you have two options with cataract surgery. One option is a traditional lens implant that will provide excellent correction of your vision, but you may need a minor glasses prescription after surgery to provide correction of your corneal astigmatism to allow for maximum clarity. The second option is placement of a newer Toric IOL which acts to counteract the corneal astigmatism. The implant is placed into the eye and results in less dependence on glasses for correction of corneal astigmatism.
With traditional lens implants and Toric lens implants, you will need glasses to assist with close up reading tasks. There are types of "presbyopia-correcting" IOLs that may allow independence from glasses for up close and at distance. If you are interested in any of these lens technologies, your doctor would be happy to discuss the lens options further and help you determine whether you are a candidate.