Understanding Cataracts

By David F. Chang MD


Because cataracts are so common, and because cataract surgery is my specialty, I have written this booklet for patients to answer commonly asked questions about cataracts. Although each individual’s condition may differ, advances in cataract surgery continue to benefit more patients than ever before. We are proud to offer premier cataract treatment to our clients throughout the San Jose and Los Altos areas!

I hope that this information will help you to better understand your situation, and to view it with less apprehension.

What is a cataract?

A cataract is a clouding of the normally transparent lens within the eye. It is not a growth or a film that can be peeled off. Located inside the eye, cataracts cannot be seen without a special microscope. Thus, they do not change the appearance of the eye; they do not cause discomfort. Changes may be so gradual that you are not aware of a cataract’s effect at first.

Cataracts are the most common cause of blurred vision over the age of 50. Although there is no medicine or diet to cure cataracts, surgical removal of the cataract and replacement with a permanent artificial lens implant can restore lost vision.

How does the eye work?

The eye functions very much like a camera. Light enters through the cornea – the clear front “window” of the eye. In order to reach the back of the eye, it passes through the pupil, which is the hole in the iris. The color of our eyes (blue, brown, hazel) is really the color of the iris seen through the transparent cornea.

Immediately behind the pupil is the natural lens of the eye. Just as a camera lens focuses onto film at the back of the camera, the human lens focuses light onto the retina, the thin layer of tissue lining the back of the eye. Like camera film, the retina forms the “picture” which is then relayed to the brain along the optic nerve.

What causes blurred vision?

Just as fingerprints on a camera lens cause blurred pictures regardless of our efforts to focus, a cloudy lens within the eye causes blurred vision. When the human lens becomes cloudy or hazy enough to interfere with vision, it is called a cataract. Changing glasses (focus) will not help the blur that is caused by a cataract.

Just as defective film will spoil photographs, a weak retina (as in a condition called macular degeneration) will cause blurred vision in eyes despite a clear lens and proper focus (glasses). Good vision always requires (1) optimal focus – usually with glasses, (2) a clear lens, and (3) a healthy retina.

What are the symptoms?

Cataracts cause visual symptoms only; they do not cause pain, discomfort, tearing, or redness. The visual symptoms can vary. Blurriness, hazy vision, or increased glare from sunlight and headlights may be present. Some cataracts turn yellow, causing fading of color. Reading may take more effort, and you may tire prematurely. Vision progressively worsens over a period of years or sometimes after only a few months.

What causes cataracts?

Some cataracts are caused by birth defects, injuries, diabetes, or prolonged use of certain medications, such as steroids. Highly nearsighted patients may develop cataracts at a young age. However, most cataracts result simply from the natural aging process of the human lens. Like gray hair, cataracts are not a disease, nor do they occur at the same age or rate in everyone.

When should cataracts be removed?

The decision to have cataracts removed is elective. Because cataracts do not harm other parts of the eye, nothing needs to be done if you are not significantly bothered by symptoms. However, as activities such as driving and reading become increasingly affected by cataracts, surgery becomes a logical option to consider.

With the success of the modern implant, waiting for cataracts to “ripen” is no longer necessary. Since cataracts will not improve and will eventually worsen, there is no advantage in delaying treatment if vision is sufficiently affected and the prognosis of surgery is good. You are never “too old” to have cataract surgery, just as you are never “too old” to enjoy better vision.

What is a “lens implant”?

To take the place of the clouded human lens, a tiny, delicately engineered artificial lens is implanted into the eye. The modern intraocular lens “implant” does not change the appearance or sensation of the eye. The implant is permanent. Unlike a contact lens, it cannot fall out and does not require cleaning.

The “prescription” or power of each patient’s implant is selected based on computer calculations that use a series of precise eye measurements performed in the office prior to surgery. The distance between the front of the eye and the retina can be measured precisely using medical sonar (ultrasound). This painless test is called the “A scan”.

How is surgery performed?

Cataract surgery is microsurgery; it utilizes an operating microscope and is performed inside the eye through an incision. One can think of the human lens as having a thin, transparent “wrapper” which holds the lens in the center of the eye. This delicate, cellophane-like skin is called the lens “capsule”. A hole is made in the front of this wrapper, and the cloudy lens is removed in several delicate stages, leaving behind an empty clear capsule. The implant is then inserted into this empty wrapper, occupying the original place of the natural lens.

What is “small incision” cataract surgery?

Removing the solid core of the cataract as a single piece requires a large incision with multiple sutures. Physical activities must be limited to avoid straining the large incision, which takes several months to stabilize. Since 1983, Dr. Chang has routinely performed the more advanced technique of “small incision surgery” using specialized technology called phacoemulsification.

The firm cataract core is fragmented into small particles that can be gently sucked out through a tiny three mm incision (1/8 inch). Modern foldable lens implants can fit through incisions this small, and sutures are not required. Physical activities are not restricted after small incision surgery, and the vision stabilizes faster than with the conventional large incision method.

Is the surgery performed with a laser?

For small incision surgery, the primary microsurgical tool used to ultrasonically remove the cataract is called a “phacoemulsifier”. Lasers may be an appropriate adjunct in some cases. The YAG laser is sometimes employed months to years following cataract surgery for a non-surgical treatment. Although the cataract cannot recur, the capsule behind the implant may later cloud and affect vision. This is not a complication. Thanks to the YAG laser, this can be painlessly corrected in the office without surgery.

What are the risks of cataract surgery?

There is some risk with any surgical procedure. For each patient, I carefully weigh the risk/benefit ratio by imagining what I would do if I were in your place. Fortunately, in experienced hands, severe complications that could worsen the vision are rare. The chances of eyelid, cornea, retina, and ocular pressure problems may depend on individual circumstances, but all may occur even without surgery – i.e. with aging alone. With modern advances in technique, more than 98% of patients with otherwise healthy eyes will gain significant visual improvement following surgery.

What is the experience of surgery like?

Your outpatient surgery will be performed at the Peninsula Eye Surgery Center, 1128 W. El Camino Real in Mountain View, CA 650-964-3200. This is the only surgery center from San Francisco to San Jose that specializes in eye surgery only, and performs one of the highest volumes of cataract surgery in Northern California.

Dr. Chang was among the first in the Bay Area to employ topical or “needle-free” anesthesia for cataract surgery. The eye is numbed by anesthetic drops, rather than the conventional shot of novocaine. Thanks to light sedation, you will feel calm and relaxed, but awake. Since your lids are gently held open, you will see light, but not the operation itself. This most advanced method eliminates sutures, anesthetic injections, eye bandages, and postoperative restrictions for most patients. Since the surgery takes less than 30 minutes, even patients in poor health can successfully undergo cataract surgery.

What is the recovery like following surgery?

You will receive detailed written instructions on care after the operation. An eye bandage is not necessary when topical anesthesia is used. The eye surface may feel scratchy at first. With small incision surgery, you may resume everyday activities and physical exercise as soon as you like.

As with any surgery, the healing period will vary with each individual. Use of the eye is not harmful, but the vision is normally blurry at first. Your eyeglass prescription will be different after surgery and will be changed approximately one month later.

In Conclusion:

Helping patients regain vision they have lost is one of my most gratifying experiences. Thanks to the many advances in ocular microsurgery, we can safely restore excellent vision to most people with cataracts. More than 1.5 million Americans enjoy the benefits of renewed sight through cataract surgery annually. I hope this material has been both interesting and reassuring to you. If you should have any further questions please ask us.

FAQ about artificial lens implants

How long will the lens implant last?

The lens implant is permanent and, unlike an artificial joint or heart valve, there are no moving parts in the lens that could wear out over time. Artificial lenses are even placed in children following congenital cataract surgery because they will last a lifetime.

Does having a lens implant mean that I won’t need glasses anymore?

Not exactly. While we are young, our internal eye muscles can change and control the shape of the natural human lens. This alters the lens power, and allows us to shift our focal distance, from far to near. It is so fast and automatic (like an auto-focus camera) that we aren’t even aware that it is occurring. Whether the eye has good distance focus with or without glasses, it is this accomodation of our natural lens that then enables us to focus closer up to read.

Presbyopia is the natural and unavoidable process by which everyone slowly loses the ability to accomodate over time. This is due to a loss of lens flexibility with age. As we progress from our forties through to our sixties, everyone gradually loses the ability to focus in the direction from far to near. This function is instead replaced with reading glasses (for the person who sees distance well without glasses) or bifocals and trifocals (for the person who needs eyeglasses to see distance).

The artificial lens is a single, fixed focus lens. It cannot give distance focus one moment, and near focus the next. Following cataract surgery, patients will therefore choose from the same options available to every other person over the age of 50 without cataracts or implants. They can wear separate glasses for help at distance (if needed); separate glasses for reading and near focus; or combine the two functions into bifocals. They can wear contact lenses if they choose to. No one is “required” to wear eyeglasses. Rather, depending upon the activity and at what distance their eye is in natural focus already, patients can pick and choose when they want to wear glasses to enhance their vision further.

Since there is no opportunity for trial and error in the IOL selection process, there is no guarantee that the targeted focal distance will be attained following surgery. Fortunately, eyeglasses can be used to provide clear focus, just as they do for any other patient whose eyes do not have perfect focus naturally.

Does the artificial lens replace the need for sunglasses?

Sunglasses provide two benefits. Their darker tint reduces the brightness of our surroundings by decreasing the amount of light that reaches the eye. The major health benefit is that they contain a transparent UV coating which blocks out the invisible ultraviolet rays of the sun. Ultraviolet rays are what cause sunburn, and are present even on overcast days. Because of the potential for cumulative damage to the retina over time, it is advisable to block out ultraviolet light. Modern artificial lens implants are permanently coated so as to provide this UV protection at all times. Since the implant is not darkly tinted, patients may still choose to wear sunglasses for comfort, just as they did before their cataract surgery.

Can the IOL be removed and replaced?

Although it is rarely necessary, the IOL can be removed and replaced. Although the need to remove the lens is very unusual, the most common reason would be that the power is incorrect, despite all of the preliminary calculations. Another reason would be if the IOL shifted out of position inside the eye. This is very rare. Because the artificial lens is designed to be permanent, it is not a simple task to remove the IOL.

If I previously had LASIK, R.K., or other refractive surgery, can I still have an IOL?

Yes. However, prior refractive surgery significantly impairs the IOL power selection process [link to IOL power selection]. Because of the significant surgical alteration in the corneal shape, the corneal measurements used to calculate the necessary IOL power become very inaccurate. One must often rely upon prior records from exams immediately before and after the refractive surgery. Even so, it is still very difficult to estimate the required IOL power. The further off this calculation is, the stronger the postoperative eyeglasses for distance focus will need to be.

IOL power selection:

After the age of 50, most patients no longer have perfect natural focus for distance. However, no eye over the age of 50, with or without an IOL, can shift the focus between far and near without glasses. Thus, optimal distance focus without glasses may not be everyone’s preference. If the overriding priority is to be able to read up close without glasses, a patient may prefer to remain nearsighted after cataract/IOL surgery. For others, a slight amount of myopia (nearsightedness) may represent a good compromise between being either very blurred for distance or very blurred for near without glasses.

All optical lenses – whether eyeglasses, contact lenses, or IOLs – are manufactured in a large range of different powers. The process of determining one’s eyeglass prescription – a refraction – is really a trial and error exercise. After the examiner narrows down the choices to several lens powers, the patient selects which one best focuses their vision by repeatedly comparing different pairs of lenses … “Which is better – one or two?” In this way, the patient ultimately ends up receiving that one contact lens or one spectacle lens that best corrects their vision for the distance. Vision without glasses is called “uncorrected” vision.

Each IOL model is also manufactured in a large range of powers. Of the 40 to 50 available IOL powers to choose from, there is only one that will be the single perfect lens for far distance focus. Three or four others will be very close, and the rest will result in significant blur for distance without glasses. Regardless of what the uncorrected vision is after surgery, eyeglasses can always be prescribed to provide excellent distance vision for an otherwise healthy eye.

With the patient’s input, the surgeon must decide what general distance (far/near/or intermediate focus) to target for the patient’s uncorrected vision after IOL surgery. The patient’s lifestyle, the prescription of the other eye, and the patient’s prior eyeglass prescription are factors to consider. A specific lens power for the IOL is then selected with the goal of achieving this target.

The surgeon uses a computer program to determine the appropriate IOL power in advance of the surgery. The calculations are based upon those dimensions of the eyeball, which determine the unique optical properties of that individual eye. These painless measurements are taken preoperatively. The most important are 1) the amount of corneal curvature, which correlates with the cornea’s optical power and 2) the distance from the cornea to the retina. Since this distance cannot be determined with a ruler, ultrasound (medical sonar) or similar technology is used to measure this distance in tenths of millimeter accuracy.

Let us assume that the surgeon is seeking to optimize distance focus without glasses postoperatively. The IOL power selected is an estimate derived from these calculations. However, without the benefit of trial and error (as is employed in prescribing glasses or contacts), perfect distance focus is not assured. Since one cannot try out different IOL powers, the hope is to pick one of the two to three IOL powers that will get the patient into the right “ballpark”. Eyeglasses can then be worn as an option to fine-tune and achieve best distance focus.

Every individual’s situation may be different. Although there is a wide range of targeted results, a very common outcome following IOL surgery is that the patient can see reasonably well indoors and around the house without glasses. They will utilize reading glasses to read comfortably. They will pick and choose when to don distance glasses to enhance their far focus. This might be for driving, for example. Many patients will continue to choose bifocals out of habit or for convenience. In essence, the patient will have the same focusing options that all other patients over the age of 50 have. As with any other patient, contact lenses or refractive surgery are available options as well.


Written by David F. Chang, M.D.

762 Altos Oaks Drive, Los Altos, CA

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