CATARACTS

Cataract Overview

Cataracts are changes in clarity of the natural lens inside the eye that gradually degrade visual quality. The natural lens sits behind the colored part of the eye (iris) in the area of the pupil, and cannot be directly seen with the naked eye unless it becomes extremely cloudy. The lens plays a crucial role in focusing unimpeded light on the retina at the back of the eye. The retina transforms light to a neurologic signal that the brain interprets as vision. Significant cataracts block and distort light passing through the lens, causing visual symptoms and complaints.
The term cataract is derived from the Greek word cataractos, which describes rapidly running water. When water is turbulent, it is transformed from a clear medium to white and cloudy. Keen Greek observers noticed similar-appearing changes in the eye and attributed visual loss from "cataracts" as an accumulation of this turbulent fluid, having no knowledge of the anatomy of the eye or the status or importance of the lens.
Cataract development is usually a very gradual process of normal aging but can occasionally occur rapidly. Many people are in fact unaware that they have cataracts because the changes in their vision have been so gradual. Cataracts commonly affect both eyes, but it is not uncommon for cataracts in one eye to advance more rapidly. Cataracts are very common, affecting roughly 60% of people over the age of 60, and over 1.5 million cataract surgeries are performed in the United States each year.
Experts have estimated that visual disability associated with cataracts accounts for over 8 million physician office visits a year in the United States. This number will likely continue to increase as the proportion of people over the age of 60 rises. When people develop cataracts, they begin to have difficulty doing activities they need to do for daily living or for enjoyment. Some of the most common complaints include difficulty driving at night, reading, participating in sports such as golfing, or traveling to unfamiliar areas; these are all activities for which clear vision is essential.

Cataract Causes

The lens is made mostly of water and protein. Specific proteins within the lens are responsible for maintaining its clarity. Over many years, the structures of these lens proteins are altered, ultimately leading to a gradual clouding of the lens. Rarely, cataracts can present at birth or in early childhood as a result of hereditary enzyme defects, and severe trauma to the eye, eye surgery, or intraocular inflammation can also cause cataracts to occur earlier in life. Other factors that may lead to development of cataracts at an earlier age include excessive ultraviolet-light exposure, diabetes, smoking, or the use of certain medications, such as oral, topical, or inhaled steroids. Other medications that are more weakly associated with cataracts include the long-term use of statins and phenothiazines.

Types of Cataracts

All cataracts are fundamentally a change in the clarity of the overall lens structure; however, cataracts may result either early in life or as a result of aging, and different portions of the lens may be more affected than others. Cataracts that occur at birth or present very early in life (during the first year of life) are termed congenital or infantile cataracts. These cataracts require prompt surgical correction or they may prevent the vision in the affected eye from developing normally. When the central portion of the lens is most affected, which is the most common situation, these are termed nuclear cataracts. The outside of the lens is called the lens cortex, and when opacities are most visible in this region, the cataracts are called cortical cataracts. There is an even more specific change that occasionally happens, when the opacity develops immediately next to the lens capsule, either by the anterior, or more commonly the posterior, portion of the capsule; these are called subcapsular cataracts. Unlike most cataracts, posterior subcapsular cataracts can develop rather quickly and affect vision more suddenly than either nuclear or cortical cataracts.

Cataract Symptoms

Having cataracts is often compared to looking through a foggy windshield of a car or through the dirty lens of a camera. Cataracts may cause a variety of complaints and visual changes, including blurred vision, difficulty with glare (often with bright sun or automobile headlights while driving at night), dulled color vision, increased nearsightedness accompanied by frequent changes in eyeglass prescription, and occasionally double vision in one eye. Some people notice a phenomenon called "second sight" in which one's reading vision improves as a result of their increased nearsightedness from swelling of the cataract. A change in glasses may help initially once vision begins to change from cataracts; however, as cataracts continue to progress and opacify, vision becomes cloudy and stronger glasses or contact lenses will no longer improve sight.
Cataracts are usually gradual and usually not painful or associated with any eye redness or other symptoms unless they become extremely advanced. Rapid and/or painful changes in vision are suspicious for other eye diseases and should be evaluated by an eye-care professional.

When to Seek Medical Care

Eye-care professionals may mention during a routine eye exam that you have early cataract development even if you are not yet experiencing visual symptoms.
Although your doctor will be able to tell when you first begin to develop cataracts, you will generally be the first person to notice changes in your vision that may require cataract surgery. Clouding of the lens may start to be seen at any age, but it is uncommon before the age of 40. However, a large majority of people will not begin to have symptoms from their cataracts until many years after they begin to develop.
Since cataract development rarely causes any long-term damage to the eye, cataract surgery should be considered only when visual symptoms begin to develop. Whenever significant vision problems are noted, you should schedule an exam by an eye-care professional. Typical symptoms may include blurry vision, difficulty with glare or night vision, poor color vision, or frequent changes in eyeglass prescription.
For an early cataract changes, vision may be improved by simply changing your eyeglass prescription, using a magnifying lens, or increasing lighting when you do visually demanding tasks. Eventually, cataracts get to a point where the only effective intervention is surgery. This decision is made based mainly on the degree of visual limitation the patient is experiencing.

Exams and Tests

To detect a cataract, the eye-care provider examines your lens. A comprehensive eye examination usually includes the following:

• Visual acuity test: An eye chart test is used to measure your reading and distance vision.
  
  
• Refraction: Your eye doctor should determine if glasses would improve your vision.
  
  
• Glare testing: Vision may be significantly altered in certain lighting conditions and normal in others; in these circumstances, your doctor may check your glare symptoms with a variety of different potential lighting sources.
  
  
• Potential acuity testing: This helps the ophthalmologist get an idea of what your vision would be like after removal of the cataract. Think of this as the eye's vision potential if the cataract was not present.
  
  
• Contrast sensitivity testing: This checks for your ability to differentiate different shades of gray, which is often this limited by cataracts.
  
  
• Tonometry: a standard test to measure fluid pressure inside the eye (Increased pressure may be a sign of glaucoma.)
  
  
• Pupil dilation: The pupil is enlarged with eye drops so that the ophthalmologist can further examine the lens and retina. This is important to determine if there are other conditions which may ultimately limit your vision besides cataracts

• Cataract Treatment

  
  

  Surgery

  The standard cataract surgical procedure is typically performed in either a hospital or in an ambulatory surgery center. The most common form of cataract surgery today is a process called phacoemulsification. With the use of an operating microscope, your surgeon will make a very small incision in the surface of the eye in or near the cornea. A thin ultrasound probe is inserted into the eye that uses ultrasonic vibrations to dissolve (phacoemulsify) the clouded lens. These tiny fragmented pieces are then suctioned out through the same ultrasound probe. Once the cataract is removed, an artificial lens is placed into the same thin capsular bag that the cataract occupied. This intraocular lens is essential to help your eye focus after surgery.
  There are three basic techniques for cataract surgery:
  
  • Phacoemulsification: This is the most common form of cataract removal as explained above. In this most modern method, cataract surgery can usually be performed in less than 30 minutes and usually requires only minimal sedation and numbing drops, no stitches to close the wound, and no eye patch after surgery.
    
    
  • Extracapsular cataract surgery: This procedure is used mainly for very advanced cataracts where the lens is too dense to dissolve into fragments (phacoemulsify) or in facilities that do not have phacoemulsification technology. This technique requires a larger incision so that the cataract can be removed in one piece without being fragmented inside the eye. An artificial lens is placed in the same capsular bag as with the phacoemulsification technique. This surgical technique requires a various number of sutures to close the larger wound, and visual recovery is often slower. Extracapsular cataract extraction usually requires an injection of numbing medication around the eye and an eye patch after surgery.
    
    
  • Intracapsular cataract surgery: This surgical technique requires an even larger wound than extracapsular surgery, and the surgeon removes the entire lens and the surrounding capsule together. This technique requires the intraocular lens to be placed in a different location, in front of the iris. This method is rarely used today but can be still be useful in cases of significant trauma.

  • What are the different types of intraocular lenses implanted after cataract surgery?

    As the natural lens plays a vital role in focusing light for clear vision, artificial-lens implantation at the time of cataract surgery is necessary to yield the best visual results. Because the implant is placed in or near the original position of the removed natural lens, vision can be restored, and peripheral vision, depth perception, and image size should not be affected. Artificial lenses are intended to remain permanently in place, require no maintenance or handling, and are neither felt by the patient nor noticed by others.
    There are a variety of intraocular lens styles available for implantation, including monofocal, toric, and multifocal intraocular lenses.
    
    1. Monofocal lens: These lenses are the most commonly implanted lenses today. They have equal power in all regions of the lens and can provide high-quality vision at a single focal point (usually at distance). They usually require only a light pair of spectacles for optimal distance vision correction. However, monofocal lenses do not correct astigmatism, an irregular oblong corneal shape that can distort vision at all distances, and require corrective lenses for all near tasks, such as reading or writing.
    
    2. Toric lens: Toric lenses have more power in one specific region in the lens (similar to spectacles with astigmatism correction in them) to correct astigmatism, which can further improve unaided distance vision for many individuals. Due to the difference in lens power in different areas, the correction of astigmatism with a toric lens requires that the lens be positioned in a very specific configuration. While toric lenses can improve distance vision and astigmatism, they still require corrective lenses for all near tasks, such as reading or writing.
    
    3. Multifocal lens: Multifocal intraocular lenses have a variety of regions with different power within the lens that allows individuals to see at a variety of distances, including distance, intermediate, and near. While promising, multifocal lenses are not for everyone. They can cause significantly more glare than monofocal or toric lenses. Further, multifocal lenses cannot correct astigmatism, and some patients require additional surgery such as LASIK to correct astigmatism and maximize their unaided vision.
     

    What should one expect prior to and on the day of surgery?

    Prior to the day of surgery, your ophthalmologist will discuss the steps that will occur during surgery. Your ophthalmologist or a staff member will ask you a variety of questions about your medical history and perform a brief physical exam. You should discuss with your ophthalmologist which, if any, of your routine medications you should avoid prior to surgery. Prior to surgery, several calculations will be made to determine the appropriate power intraocular lens to implant. A specific artificial lens is chosen based on the length of the eye and corneal curvature (the clear portion of the front of the eye).
    It is important to remember to follow all of your preoperative instructions, which will usually include not eating or drinking anything after midnight the day prior to your surgery. As cataract surgery is an outpatient procedure, arrangements should be made with family or friends to transport you home after the surgery is complete. Most cataract surgery occurs in either an ambulatory surgery center or a nearby hospital. You will be required to report several hours before the scheduled time for your surgery. You will meet with the anesthesiologist who will work with the ophthalmologist to determine the type of sedation that will be necessary. Most cataract surgery is done with only minimal anesthesia and numbing drops without having to put you to sleep.
    During the actual procedure, there will be several people in the operating room in addition to your ophthalmologist; these include anesthesiologists and operating-room nurses and technicians. While cataract surgery does not involve a significant amount of pain, medications are used to maximize your comfort. The actual removal of the clouded lens will take approximately 20-30 minutes in most instances.
    After leaving the operating room, you will be brought to a recovery room where your doctor will prescribe several eye drops that you will need to take for a few weeks postoperatively. While you may notice some discomfort, most patients do not experience significant pain following surgery; if you do you experience decreasing vision or significant pain, you should contact your ophthalmologist immediately. Depending on the type of anesthesia used, you may or may not have a patch on your eye that will remain in place for the first day and night after surgery.
    
    

    What should one expect after the surgery?

    Following surgery, you will need to return for visits within the first few days and again within the first few weeks after surgery to assure your eye is healing properly. During this time period, you will be using several eye drops which help protect against infection and inflammation, and you will have some restrictions on activities such as lifting heavy objects and bending forward or stooping to the ground. Within several days, most people notice that their vision is improving, and they are able to return to work. During the several office visits that follow, your doctor will monitor for complications, and once vision has stabilized, will fit you with glasses if needed. The type of intraocular lens you have implanted will determine to some extent the type of glasses required for optimal vision.
    
    

    What are potential complications of cataract surgery?

    While cataract surgery is one of the safest procedures available with a high rate of success, rare complications can arise. Your ophthalmologist will discuss the specific potential complications of the procedure that are unique to your eye prior to having you sign a consent form. The most common difficulties arising after surgery are persistent inflammation, changes in eye pressure, infection, or swelling of the retina at the back of the eye, and retinal detachment. If the delicate bag the lens sits in is injured, then the artificial lens may need to be placed in a different location. In very rare cases, the intraocular lens moves or does not function properly and may need to be repositioned, exchanged, or removed. All of these complications are extremely rare but can lead to significant visual loss if left untreated; thus, close follow-up is required after surgery.
    In some cases, within months to years after surgery the thin lens capsule may become cloudy, and you may have the sensation that the cataract is returning because your vision is becoming blurry again. This process is termed posterior capsule opacification, or a "secondary cataract." To restore vision, a laser is used in the office to painlessly create a hole in the cloudy bag. This procedure takes only a few minutes in the office, and vision usually improves rapidly.
    
    

    Prevention

    At present, there is no real effective way to prevent the formation of cataracts, so secondary prevention involves controlling other eye diseases that can cause cataracts and minimizing exposure to factors that promote cataracts.
    
    • Wearing sunglasses outside during the day might reduce your chances of developing cataracts or having problems with the retina. Some sunglasses can filter out UV light, reducing exposure to harmful UV radiation and might slow the progression of cataracts.
      
      
    • Some people take vitamins, minerals, and herbal extracts to decrease cataract formation. No scientific data prove that these remedies are effective. No topical or oral medications or supplements are proven to decrease the chance of developing cataracts.
      
      
    • A healthy lifestyle might help, just as a healthy lifestyle helps prevent other diseases in the body. Eat a proper diet, get regular exercise and rest, and do not smoke.
      
      
    • If you have diabetes, tight blood-sugar control can delay the otherwise accelerated development of cataracts.
    • sOURCE:EMEDICINEHEALTH