WHAT IS A CATARACT?
The lens in the eye can become cloudy and hard (over time in adults), a condition known as a cataract. Cataracts are more commonly known as a cause of poor vision in older adults, but cataracts can also occur in babies and children. Cataracts may be present at birth (congenital). They can be visually obstructive at birth or insignificant at birth and worsen significantly during childhood. More commonly, cataracts develop from aging, an eye injury, or medications, such as steroids, but they may be hereditary, caused by tumors, or associated with an eye condition or systemic disease. An affected child may need to have a workup regarding the etiology of the cataract(s).
When a cataract is present in both eyes, family members can usually tell that there is a problem with the child’s vision. When only one eye is affected, the child may appear to see normally.
Congenital cataracts are usually diagnosed by the pediatrician during the first few days or weeks of life. Infants are typically referred to a pediatric ophthalmologist. Infants with congenital cataracts may develop profound amblyopia (lazy eye). In the case of a significant opacity, cataract surgery must usually be performed very soon if useful vision is to be obtained.
CATARACTS IN INFANTS AND OLDER CHILDREN
Cataracts in children may adversely affect visual development particularly if a central opacity is greater than or equal to 3 mm in diameter. A bulge in the front or more commonly back membrane of the lens can cause distortion in addition to obstruction if it contains an opacity. The potential for visual development spans the period from birth to approximately age nine. The younger the child, the more detrimental to visual development an obstructive cataract will be. Dense cataracts at an early age cause deprivational amblyopia, the most severe form of amblyopia (or lazy eye). If the view of the back of the eye is inadequate, the patient should see a retina specialist for a b-scan ultrasound of the eye to rule out posterior segment pathology, including a mass or retinal detachment, which could have led to the cataract.
Although the natural lens has some distinct advantages over an artificial lens, if the cataract adversely affects visual development (and there is not a problem in the back of the eye to preclude cataract surgery), the child should have the cataract removed as soon as possible. If a cataract, which can also cause blurry or dull vision, sensitivity to light, and glare, interferes with the activities of daily life for a child or an adult, the patient will most often benefit from its removal. Surgery is the only way to remove a cataract. Without the surgery, vision loss from the cataract will likely worsen, possibly irreversibly in a child. The child may need to have a workup to determine the cause of the cataract(s).
REFRACTIVE CORRECTION FOR PEDIATRIC CATARACT SURGERY PATIENTS
Most ocular growth occurs in the first two years of life, but refractive growth continues approximately up to age 20, which has significant optical implications.
Because the majority of ocular growth takes place in the first two years of life, and thus the refractive power of the eye changes most during this time period, Dr. Shin usually leaves children under two without an intraocular lens (aphakic), and he/she wears contact lenses. As the child becomes a little older, he/she would need bifocal (and later progressive) glasses over contact lenses to see at near. If the child is left aphakic, cataract surgery will be followed preferably by an examination under anesthesia and a contact lens fitting.
Even with excellent cataract surgery and correction of the refractive error, the child may still be amblyopic, particularly if there has been a delay in the removal of the cataract(s). Even with minimal delay, a child may still have significant amblyopia, especially if the cataract is of significant size from birth, there is other ocular pathology, or there is noncompliance with amblyopia treatment following surgery. Children with congenital monocular cataracts are, in general, more prone to dense amblyopia than children with cataracts in both eyes.
If an intraocular lens is to be implanted, often by age three or sooner in the case of contact lens noncompliance, then the patient needs measurements of his/her eye (taken with an IOL Master machine in the office or during an examination under anesthesia in the operating room) to help calculate the power of the intraocular lens to order prior to cataract surgery. Over time, pseudophakic children progress toward myopia, often excessively so, compared to other children. If the patient is less than five and Dr. Shin implants an intraocular lens, Dr. Shin aims to leave the patient farsighted with glasses to correct for distance (so the patient has a better chance of having a refractive error closer to zero when he/she grows older) and bifocal (or later progressive) glasses to help with near vision (since a monocular intraocular lens, which is most commonly implanted in the children, does not focus at near).
HOW REMOVING THE CATARACT AFFECTS THE CHILD’S VISION
The goal of cataract surgery is to correct the decreased vision caused by the cataract. During the surgery, Dr. Shin removes the cataract and may implant an artificial lens called an intraocular lens or IOL. The IOL is permanently left in the eye. Cataract surgery does not correct other causes of decreased vision, such as malformation of other eye structures or intraocular inflammation. Most children still need to wear glasses and/or a contact lens after cataract surgery for near and/or distance vision. It is also important, however, to monitor and correct for the child’s refractive error over time for optimal visual development.
Prior to cataract surgery, to the extent possible, Dr. Shin performs a full eye examination and staff member(s) complete ancillary testing in the office or Dr. Shin completes it in the operating room under anesthesia. This may include an examination to determine an eyeglass prescription (refraction), measurement of vision with and without glasses (visual acuity), measurement of the pressure inside the eyes (tonometry), measurement of the curvature of the corneas (keratometry), measurement of the length of the eyes (axial length), intraocular lens calculation (biometry) to determine the best estimate of the power of the implanted IOL for the desired refractive error, microscopic examination of the front part of the eye (slit-lamp examination), and examination of the optic nerve and retina with the pupils dilated. Some of this information may need to be obtained with the child under general anesthesia for the best accuracy and thoroughness.
NEED TO STOP WEARING CONTACT LENSES PRIOR TO SURGERY (TEENAGERS)
For teenagers with cataracts which become visually significant, contact lenses, if worn, must not be worn for a period of time before the preoperative eye examination and before surgery. Because the contact lens rests on the cornea and distorts its shape, it can affect the accuracy of the measurements of the eye taken to calculate the desired IOL power. Without contact lenses for a specified period (which depends upon the kind of contact lenses and the total number of years they have been worn), the corneas can return to their natural shape. For rigid contact lenses wearers, vision will usually vary as the corneas change shape. The patient may need to remain contact lens free until the vision and cornea stabilize.
MORE INFORMATION ABOUT MEASURING FOR YOUR CHILD’S IOL
Although the method used to calculate the power of the IOL is very accurate in most patients, the final result may be different from what was planned or expected. As the eye heals, the IOL can shift very slightly toward the front or the back of the eye. The amount of this shift is not the same in everyone, and it may affect vision differently than predicted. Patients who are highly nearsighted or highly farsighted have the greatest risk of difference between the planned and actual outcome. If the visual power (refractive error) of the child’s eye after surgery is considerably different than what was anticipated, then the difference would usually be taken care of in glasses (or rarely contact lenses). Surgical replacement of the IOL or refractive surgery would only be considered in extenuating circumstances.
ALTERNATIVES FOR NEAR VISION AFTER CATARACT EXTRACTION WITH IOL
The natural lens usually changes shape to shift focus to different distances, for example from distance to near. Monofocal or single focus IOLs, which are most commonly implanted in children to see at distance, do not change shape to focus at near, so monofocal intraocular lens implant individuals require bifocals or reading glasses in order to see clearly at close range.
There is another option available to achieve both distance and near vision after cataract surgery provided the remaining eye health is excellent, but THE OPTION BELOW IS NOT USUALLY RECOMMENDED FOR CHILDREN BECAUSE THEIR REFRACTIVE ERROR CHANGES SIGNIFICANTLY AS THEIR EYES GROW.
Multifocal IOLs with (toric) or without astigmatism correction are premium IOLs which provide distance vision AND restore some or all of the eye’s ability to focus in the intermediate and near ranges. Choosing this option involves higher out-of-pocket expenses since most insurance companies only pay for a monofocal (single focus) lens.
INFORMATION ABOUT TREATING ASTIGMATISM
Patients with nearsightedness and/or farsightedness often also have astigmatism. Astigmatism is caused by an irregularly-shaped cornea; instead of being round like a basketball, the cornea is shaped like a football. Less frequently, astigmatism can be due to the curvature, position, or index of refraction of the lens. Astigmatism can make vision distorted or blurry. Treatment options for astigmatism in children include: 1) an IOL for distance vision and glasses for astigmatism and near correction, 2) a toric or astigmatism-correcting IOL with glasses for near vision, or) multifocal toric IOLs in rare cases, such as a hearing-impaired teenager with visually significant cataracts of both eyes (of unknown onset since the patient did not present until he was a teenager) and significant astigmatism who would not wear glasses in addition to hearing aids.
ANESTHESIA, PROCEDURE, AND POSTOPERATIVE CARE
The preoperative nurse instills drops to dilate and temporarily paralyze the pupil. An anesthesiologist places the child under general anesthesia.
An incision, or opening, is then made in the cornea of the eye. Dr. Shin usually leaves the incision site sutureless in adults because the wound is designed to be self-sealing, but she places very fine sutures in the wound of children because their eyes are softer after surgery, and they are more prone to press on the eye. An opening is made in the front membrane of the lens and the natural lens contents are then removed by aspiration or phacoemulsification, a technique which involves using an ultrasonic vibrating probe to break the lens up into small pieces. These pieces are gently suctioned out of the eye through a narrow, hollow tube inserted through the small incision into the eye.
For children from infancy to approximately age three, an opening is then made in the posterior capsule (the outer coating on the back side of the lens) and some of the natural gel (vitreous) behind the membrane is removed because they both usually whiten postoperatively in this age group if left intact. For children four and older, the portion of the gel close to the posterior capsule usually is less likely to opacify, but the posterior capsule can become cloudy as it can for adults. Depending on the child’s level of cooperation, a cloudy posterior capsule can be lasered open. If the child is unlikely to be able to sit still at a laser, then the posterior capsule may be opened at the time of surgery without disturbing the gel behind it. If the child has an intraocular lens implanted, it will be placed between the two circular openings of the front and back natural lens membranes (in children approximately age two to three or four) or behind the front opening and in front of the intact posterior capsule (in children five and older depending upon cooperation level). If cooperation for the laser was anticipated but not possible, the laser can be completed under general anesthesia. In rare cases, it may not be possible to implant the desired IOL or any IOL at all.
In children under two years of age, it is preferable not to insert an intraocular lens and keep up with the frequent refractive error changes as the eye grows with contact lens changes. A contact lens is chosen to correct most of the necessary focusing power because lenses in glasses would be excessively thick, heavy, and cause a Jack-in-the-box effect when the child looks to the sides. Glasses may be prescribed to help fine tune the refractive correction of the eye.
Dr. Shin examines the eye the day after surgery and at appropriate intervals thereafter. During the recovery period, drops should be instilled on the eye at varying intervals as recommended by Dr. Shin for approximately 4 weeks, depending on the individual rate of healing. Normal activity may be resumed in a day, and the eye will usually be stable postsurgically within 3 to 4 weeks, at which time glasses and/or a contact lens is/are prescribed.