Overview of Cataract Surgery
Cataracts are the top cause of avoidable blindness worldwide. While some cataracts might be present from birth, due to injury, or caused by medication, the majority are connected to aging. As we get older, our lenses, which are clear, curved structures in the eye, become less clear or “opaque”. These lenses help to focus light onto the back of our eye, or retina, much like the lens of a camera.
Our eye’s lens is about 10 mm across and 4 mm thick. It mainly consists of fibers that originate from the lens epithelium (a thin surface layer), a slender surrounding capsule, and zonular fibers. These zonular fibers, along with the ciliary body (the part of the eye that releases transparent fluid), enable the lens to change shape to focus on near and far objects.
As we age, our lens stiffens, which can lead to a condition known as presbyopia, or farsightedness. But the lens does more than just focusing light; it is not simply passive. The lens has a unique microcirculation pathway that helps maintain transparency by delivering nutrients to deeper fibers and removing waste, powered by sodium channels. It also acts as a shield, protecting the retina from damaging UV light. Additionally, it absorbs oxygen effectively due to the presence of a powerful antioxidant called glutathione (GSH). This antioxidant also helps to repair damage, scavenge harmful free radicals (oxidative species), and is thought to be released in the aqueous humor (the fluid in the front part of the eye between cornea and the lens) to provide nourishment to tissues like the cornea and trabecular network.
However, with age, damage from oxidation can accumulate, causing the lens to become less clear and form a cataract.
Regardless of why a cataract forms, when it begins to affect vision, the treatment is usually cataract surgery. If left untreated, cataracts can lead to other eye problems like glaucoma and uveitis. With modern techniques, cataract surgery is considered one of the most successful medical procedures, greatly improving vision and overall quality of life. However, like all surgeries, there can be complications, though these are rare. The most common issues include additional clouding of the lens and swelling of the retina.
Cataracts, marked by the clouding of the lens, are one of the most frequently diagnosed eye problems. In 2013, over 22 million people in the United States had cataracts. By 2020, this number is projected to increase to 30.1 million. As people age, the likelihood of developing cataracts increases, with the rate exceeding 70% for those over the age of 75. Cataracts are slightly more common in women than in men. In 2015 alone, about 3.7 million cataract surgeries were performed in the United States, and the number of procedures is expected to continue rising.
Anatomy and Physiology of Cataract Surgery
Most cataracts in adults occur due to aging, but other factors like exposure to ultraviolet light, smoking, diabetes, use of steroids and certain other drugs can also cause them. On the other hand, cataracts in children can be inherited or can be caused by diseases affecting multiple body systems, problems with the body’s metabolism, or infections the mother had during pregnancy.
An age-related cataract happens because of damage to the eye’s lens, which is thought to be related to oxidative damage. One part of the lens is the nucleus, and the cataract that forms here is the most common form, with about 13.1% of patients having it. Over time, as the lens ages, it compresses the nucleus, leading to a condition called nuclear sclerosis.
Secondly, we have what are known as cortical cataracts. These are the second most common form, affecting 8.2% of patients. These cataracts look like spokes in the lens’s cortex, or the outer region of it, and are the ones most likely to require surgery.
Last but not least, we have the least common type of age-related cataract, which causes cloudiness in the back part of the lens’s cortex. They only affect about 3.4% of patients.
Cataracts in newborns can also be genetic, with several genes known to play a part. These genes are primarily responsible for the development of the lens. Some cataracts may also be caused by metabolic disorders, infections the mother had during pregnancy, physical injury to the eye, and exposure to toxins. Certain medications, including steroids, could lead to this type of cataract. Trauma-induced cataracts should be treated more carefully as the injury often extends beyond the lens to other parts of the eye.
Why do People Need Cataract Surgery
The type of cataract you have can affect how it first shows up. Nuclear cataracts may cause problems with your distance vision, make it hard to recognize faces or colors. Cortical cataracts may cause glare, issues with reading, and sensitivity to light. Posterior subcapsular cataracts may result in poor vision in good light but better vision in low light. You might have trouble driving during the day and reading. If cataracts are not treated, they can get very severe (called “hyper-mature senile cataracts”) and lead to complications like eye inflammation (uveitis), increased pressure in your eyes (glaucoma), lens dislocation and could result in losing your vision.
Children can also have cataracts. Parents and pediatricians might notice a white appearance to the eye(s) or that the child isn’t interacting with the world visually as expected (for example, failure to look at light sources or make eye contact).
Doctors work to diagnose cataracts by finding out if they’re causing vision problems. They will also test to see how severe the cataract is and make sure there aren’t other conditions causing eye issues. This is done with eye exams and tests like checking vision with and without glasses, glare testing, checking how pupils react to light, assessing eye alignment and external appearance, checking the pressure within your eye, and examining the structures within your eye (like the lens, vitreous humor, macula, retina, and optic nerve) with a special microscope (‘slit-lamp’) and a device called an ophthalmoscope. They may also do other imaging like an OCT (optical coherence tomography) scan, or a B-scan ultrasound if they can’t see the back of your eye due to a cataract.
The vision problems caused by cataracts can be similar to those of other conditions, like glaucoma (pressure-related nerve damage in the eye), diabetic retinopathy (eye condition due to diabetes which causes spots in the vision, light flashes, blurred vision, or vision loss), and age-related macular degeneration (AMD) (age-related condition causing vision loss, trouble reading, driving, or seeing in low light). If you also have these other conditions, they need to be treated alongside the cataracts.
A cataract operation is usually recommended when the cataract is causing poor vision or day-to-day difficulties. Different questionnaires and tests can be used to help the doctor decide if cataract surgery is needed.
When a Person Should Avoid Cataract Surgery
Sometimes, a person might not be able to have surgery for a few specific reasons. If someone has cataracts (a clouding of the eye’s natural lens) but it’s not affecting their vision, surgery might not be necessary. Similarly, if a person has certain medical conditions related to eye health that can make surgery risky or ineffective, they might not be able to have it. The goal is always to ensure surgeries are safe and beneficial for the patient.
Equipment used for Cataract Surgery
Intraocular Lenses (IOL) are commonly used during cataract surgery as a replacement for the natural lens of the eye, which is removed during the procedure. Before these kinds of lenses were available, patients needed to use high-power glasses or contacts to see clearly after their surgery. Nowadays, the awareness and use of IOL have made it easier for patients to achieve better visual acuity after cataract surgery.
The first IOLs used were clear lenses made from polymethyl methacrylate – a type of plastic. However, as surgical techniques for cataract extraction started to evolve, new types of lenses were introduced that could be inserted through smaller incisions. Today, soft, foldable lenses made from materials like acrylic and silicone are widely used. These lenses provide the advantage of being inserted through a small incision and have a lower risk of dislocation.
To correct issues like astigmatism, and reduce the need for glasses, we now also offer Toric IOLs. There are also different designs of IOLs that help to fix the lens in place once inside your eye; they include plate-type, one-piece, and three-piece lenses. Your doctor will decide which is the best for you based on their professional judgement.
There are different types of IOLs to cater to various visual needs: monofocal, multifocal and toric lenses. Monofocal lenses just correct vision for one distance, either far or near. Some patients opt for monovision in which one eye is set for distance vision, and the other is set for near vision. Multifocal IOLs offer correction for both near and far vision, reducing the need for glasses. Bifocal diffractive lenses provide better near vision, and trifocal lenses aim to improve intermediate vision. However, the effectiveness of these lenses is still being studied.
Your eye doctor will take into consideration your eye size, shape, and overall health when determining the power of the intraocular lens needed for your surgery. They will use advanced technology to precisely measure your eye, and use these measurements in a formula to determine the most effective lens power for you. These calculations are key factors that contribute to the success of your surgery.
Preparing for Cataract Surgery
If you’re seeing an eye doctor, they will often conduct a complete eye exam. This means they’ll ask you about your vision and any other health problems you might have, and they’ll use a special tool called a slit-lamp to take a close look at your eyes. They will also measure different parts of your eye, like the depth of the front part of your eye, to figure out the strength of the artificial lens they might put in your eye during surgery.
Generally, you don’t need to have other medical tests before eye surgery unless your healthcare institution or doctor asks for it, especially if you have other serious health conditions. In these cases, your primary care doctor might need to give the clear before you have eye surgery.
There’s a small chance of bleeding during eye surgery, so patients can usually keep taking their blood thinners. However, if you’re taking medicine called alpha-1-antagonists, your eye doctor will need to know. These medicines can cause a condition during surgery called floppy iris syndrome, which can make the surgery more challenging to perform.
How is Cataract Surgery performed
The different techniques that doctors can use to treat cataracts include:
Anesthesia: In the past, doctors would use general anesthesia, which put the patient to sleep, or a nerve block around the eye during a type of cataract surgery called intracapsular cataract surgery. Today, however, as procedures have become less invasive, they often use local anesthetic which numbs only a specific part of your body, or topical anesthesia, a type of numbing medication you can apply to the eye’s surface.
Intracapsular Cataract Extraction (ICCE): This is an older method, first discovered in the 18th century, where the doctor removes the entire lens of your eye and the bag that holds it in place through one incision. Doctors use it less than before due to improved methods.
Manual Extracapsular Cataract Extraction: In this procedure, the natural lens of the eye comes out through an incision, and then an artificial one (IOL) is inserted. The cut is large, and stitches are required. However, it comes with a higher risk of cloudiness in the part of your eye that holds the lens, worsening of age-related macular degeneration, and swelling in the cornea, the clear front surface of your eye. The lower cost makes this method attractive and it remains in use worldwide; an adaptation of it called manual small incision cataract surgery has outcomes similar to the newer method, phacoemulsification.
Manual Small-incision Cataract Surgery (MSICS): Here, doctors use a smaller cut also known as a scleral tunnel. The incision is smaller on the outside (6.5 mm to 7 mm) but larger on the inside (9 mm to 11 mm), which allows it to seal itself. The lens comes out through this incision, and an IOL goes in its place. MSICS and phacoemulsification have similar long-term results, but MSICS is significantly cheaper.
Phacoemulsification: Doctors developed this method in 1967. They make a very small cut and insert a probe. This device uses sound waves to break up the lens, which is then sucked out. The small cut can close by itself, and foldable lenses were even developed for insertion through the small incision. It offers better vision, a decreased risk of astigmatism (an irregularly shaped cornea), and less inflammation after the operation. There’s also no need for stitches.
Femtosecond Assisted Laser Cataract Surgery (FLACS): This newer technique, developed in 2008, uses a laser to break up the tissue, significantly reducing the risk of damage to surrounding structures. It’s used to create the corneal cut and start the lens fragmentation, which reduces manual incisions and time, and energy needed in phacoemulsification. However, due to its high cost and marginal benefit, many doctors question its practical use at present.
Refractive Lens Exchange (RLE): Doctors use this method when laser surgery isn’t an option for people with strong glasses or contact lens prescriptions, or those who are likely to develop cataracts. It comes with all the risks of cataract surgery, and a higher risk of a detached retina at some point, especially in highly nearsighted people. Those with severe farsightedness are also more likely to develop swelling in the layer of blood vessels beneath the retina, and there’s an increased likelihood of early development of age-related macular degeneration and open-angle glaucoma.
After surgery, patients usually use eye drops that contain antibiotics, steroid, or anti-inflammatory medications for one to four weeks. Follow up visits with the doctor are scheduled for the day after the surgery, then after one week, one month, and then three months.
Possible Complications of Cataract Surgery
There are several complications that could happen during and after a cataract surgery, which doctors usually divide into three stages: during the operation (intraoperative), soon after surgery (early postoperative), and long after surgery (late postoperative).
Intraoperative complications: The most common problems that could happen during surgery include a tear in the back of the lens capsule (happens in 0.5% to 5.2% of surgeries), weak and floppy iris (0.5% to 2.0%), or injury to the iris or tissues supporting the eye (0.6%-1.2%). If the lens capsule is torn, often parts of the lens are left in the eye; this could cause swelling of the cornea (the front part of your eye) and of the macula (part of the retina at the back of your eye). These complications can increase risk of severe eye infection (endophthalmitis) by six times and retinal detachment by 19 times!
Early postoperative complications: Right after surgery, some patients can experience temporary increase in eye pressure, swollen cornea, or a toxic reaction in the front part of the eye. Serious infection (endophthalmitis), though rare due to medicines given within the eye during surgery, is one of the severest complications. Risk of getting endophthalmitis is higher if you have diabetes, are more than 80 years old, or the operation involved large incisions. Within two weeks of surgery, this can cause reduced vision, redness, and pain in your eye. Even with antibiotics, vision loss could be serious, depending on the type of bacteria causing the infection.
Late postoperative complications: Some problems don’t show up until later, such as cloudy vision due to opacification of the lens capsule (happens in 0.3% to 28.4% of surgeries), swelling in the macula, and retinal detachment (0.1% to 1.3%). The most common late complication involves the lens capsule which becomes cloudy due to leftover lens cells. This can cause blurred vision and complaints of glare; doctors often use a specific laser to correct this. Other complications like cystoid macular edema, caused by leaky blood vessels in the eye, could result in decreased vision and distorted vision. Younger patients and men have greater risk of retinal detachment, which causes flashing lights, floaters, and loss of peripheral vision.
No surgery is perfect, and despite cataract surgery increasing vision clarity and improving quality of life, some patients may still see shadows, halos and starbursts around lights even afterwards. These are known as dysphotopsias and can be quite troublesome. They are often caused by the new acrylic lens in the eye, and for some people finding their symptoms too annoying, doctors might recommend exchanging the lens with a different type.
What Else Should I Know About Cataract Surgery?
Cataract surgery is a safe and very effective way to improve vision. In fact, up to 95% of people who have this surgery will be able to see more clearly, with a visual acuity (clarity of vision) of 20/40. This is like being able to see something 20 feet away as clearly as a person with normal vision would see it from 40 feet away.
People who have had cataract surgery often report feeling happier and more emotionally balanced. They also find it easier to engage in social activities. Additionally, simple everyday tasks like reading, watching television, and recognizing faces become much easier.
Interestingly, studies show that people who have had cataract surgery are less likely to have car accidents. There’s even evidence to suggest that having this surgery can increase a person’s lifespan.
There’s also a financial advantage to having cataract surgery. Even though the surgery has an upfront cost, it pays off in the long run. This is because poor vision can lead to other costs, like having to pay for hospital stays, caretakers, and treatment for depression, not to mention the negative impact it can have on a person’s ability to work. When you add it all up, the return on investment (ROI) for cataract surgery can be as high as 833%.
