Thomas F. Mauger, MD
I. Why Should You Know About Cataracts and Cataract Surgery?
A. Cataracts are the most common cause of treatable blindness in the world.
B. Cataract surgery is the most common surgery performed in the U.S., with 1 million cataract surgeries being performed each year.
C. Cataracts may be confused with other more urgent causes of loss of vision.
D. You may have to evaluate a patient who needs, or you suspect needs cataract surgery.
E. You or your family may require cataract surgery some day.
Laymen will often use the term cataract to signify any loss of vision. Many times patients will infer blindness when told of the diagnosis of cataract. The aware physician can allay these fears and reassure them that effective treatment is usually available.
II. Diagnosis of Cataract
Symptoms
Along with the cornea, the crystalline lens provides the optical focusing of the light onto the retina. A cataract is an opacity or irregularity in this otherwise clear structure. While some cataracts are present at birth (congenital) or early in life (juvenile), most cataracts occur later in life (senile).
Cataracts may form in the center (nuclear sclerosis), in the peripheral lens material (cortical), or directly under the capsule of the lens (subscapular). The typical symptoms associated with cataract surgery are directly related to the location of the cataract (See Figure 1).
A. The most common symptom of cataract is gradual reduction in vision. This almost always occurs over years or months. A rapid reduction in vision can occur with a unilateral cataract which was not previously recognized by patients until they closed their other eye. This is called “discovery.”
Many patients will be able to function well with reduced vision in one eye as long as the other eye is still seeing well. When both eyes are affected, the patient will complain of inability to read fine print (phone book, stock quotations) and will have difficulty seeing objects at a distance (road signs).
Magnifiers and other vision aids can allow continued function, but many patients will present when they cannot pass the drivers’ exam due to poor vision. In most states, magnifiers and telescopes are not allowed to augment vision to allow driving due to their restricted field of view, and the patient may request cataract surgery to improve vision.
Figure1: Anatomic Location of Cataracts
With retroillumination media, opacities (cornea and lens) will appear as shadows. Axial nuclear cataracts will usually look like a muddy haze while subcapsular opacities will appear dark and well demarcated.
*Cortical cataracts may sometimes occur in an axial position, looking similar to subcapsular cataracts.
B. Refractive error may change with cataracts. Nuclear sclerosis is associated with increased refractive index of the central lens, which increases the power of the lens, causing myopia. Patients, who for years required bifocals in order to read, may now be able to read without glasses. This phenomenon is termed “second vision.”
With time the myopia will increase, making it difficult for the patient to read. New lens correction will improve vision temporarily. Sooner or later the lens substance will opacify and cause uncorrectable loss of vision.
C. If the increase of refractive index in the nucleus is abrupt enough, the lens will become bifocal or multifocal, having more than one discrete focal point. The result for the patient is monocular diplopia. This may appear as distinct double vision or a ghost image. Double vision that disappears when either eye is covered is binocular and secondary to strabismus.
D. Blinding glare in bright light or while driving at night is characteristic of a plaque-like cataract located in the posterior lens which may even be beneath the posterior capsule (posterior subcapsular cataract). These cataracts may be associated with excellent measured visual acuity, which precipitously drops with light glare. Many of these patients are so debilitated by this glare that they will require cataract surgery, with measured vision of 20/20 in our exam rooms, but vision worse than 20/400 when bright headlights are coming toward them.
III. Sudden Visual Loss
The gradual development of a unilateral cataract may go unnoticed by the patient until it is severe, causing a seemingly sudden loss of vision. A true sudden loss of vision is NEVER caused by a cataract. Other possibilities must be considered, including retinal detachment, central retinal artery or vein occlusion, macular or vitreous hemorrhage, or optic neuropathy. Sudden, severe loss of vision ALWAYS demands immediate evaluation to rule out these potentially treatable conditions.
A. Examination
The slit lamp is the best instrument to evaluate a cataract; however, the ophthalmoscope is a readily available alternative to view media opacities. Good dilation of the pupil assists in the diagnosis. Study of red reflex from about 20 cm is done with a 5D lens.
Nuclear sclerosis causes a gradually increasing central density as compared with discrete wedge-shaped cortical opacities and plaque-like subcapsular opacities. It is difficult to locate the anterior-posterior extension of the opacity using the red reflex, but the general shape and extent can be ascertained.
Attempting to use the direct ophthalmoscope to view the retina is an excellent way to evaluate the visual loss caused by the cataract. If the patient’s vision is limited due to a cataract, the examiner’s view of the retina should be similarly blurred.
Exceptions to this rule are the view through a pharmacologically dilated pupil with a central opacity and double focus cataracts. The view may be remarkably good around the cataract while the actual vision through an undilated pupil may be dismal. Poor vision with an excellent view of the retina is not due to a cataract.
Pupillary examination is useful in differentiating optic nerve and extensive retinal disease from media opacities such as cataracts. The afferent input to the pupillary system is light via IIcn. Light striking either eye will lead to equal constriction of the pupils in normal circumstances. If the afferent system of one eye is abnormal (ex., optic neuritis), both pupils will relatively dilate when the light is shined in that eye vs. the other eye.
The swinging flashlight test involves directing the light first at one eye, directly to the other, and then back and forth. Both pupils will constrict when the light is directed at the normal eye and then dilate when directed at the eye with significant optic nerve or extensive retinal damage.
This is called an afferent pupillary response or Marcus Gunn pupil. A positive afferent pupillary response in that eye with a cataract (even a very dense cataract) means the visual loss is probably due to optic nerve and/or retinal problems and the prognosis for visual improvement with cataract surgery is guarded (see Figure 2).
B. Types of Cataracts
1. Development cataract: lens opacities may occur due to adverse conditions during development. The time during development that the stimulus occurs will determine the location of the cataract. A well-known congenital cataract occurs with congenital rubella syndrome. This is also associated with glaucoma and retinopathy. Another cause of developmental cataracts is galactosemia.
2. Traumatic cataract: a penetration or blunt injury of the eye may lead to dislocation or opacification of the lens. Rupture of the lens capsule usually leads to a localized or complete cataract. The cataract may immediately occur after injury or any time up to many years later.
Acute swelling of the traumatized lens may lead to angle closure glaucoma and extremely high intraocular pressure. Other ocular injuries must be searched for, including ruptured globe, glaucoma, retinal detachment, and muscular damage.
Figure 2: The Afferent Pupillary Response (Marcus Gunn Pupil)
Causes of a Marcus Gunn Pupil
- Optic Nerve Lesion
- Ischemia
- Inflammation
- Trauma
- Asymmetric glaucoma
- Extensive Retinal Pathology
- Large retinal detachment
- Central retinal artery occlusion
Causes of Visual Loss That Do Not Generally Cause a Marcus Gunn Pupil
- Media Opacities
- Cataract
- Corneal scar
- Vitreous opacity
- Bilateral, Symmetric
- Optic nerve pathology
- Lesions to the visual pathway posterior to the optic chiasm
3. Age-related cataracts – Lens opacities are much more common after age 40. These cataracts may be nuclear sclerotic, subcapsular, or cortical. These cataracts may progress rapidly (months) or slowly (decades). Some asymmetry is the rule and the progression of one cataract will usually be duplicated in the second.
4. Corticosteroid cataract – Cataracts secondary to prolonged corticosteroid use are the most common endocrine and drug-related cataracts. These cataracts occur after several years of use at relatively high drug doses. These cataracts are almost always posterior subcapsular in location. They may progress to become debilitating within several months. They may stabilize if steroid use is stopped.
5. Uveitis-related cataract – Severe, prolonged uveal inflammation usually results in extensive ocular damage, including cataract formation. It is essential that the inflammation be controlled before attempting surgical correction of the cataract.
C. Management of Cataract
1. Nonsurgical: early in the treatment of a cataract, any reassurance is necessary that other more serious ocular problems are not present (ex., glaucoma). Early refractive changes are easily made. Larger changes may require complex spectacle correction.
Adjustments in lighting to increase contrast and eliminate glare can often increase visual efficiency. It is truly amazing how many patients who were once told that they have a cataract request removal, even though their vision is perfect.
Prevention of cataract is very difficult and most of the important genetic factors cannot be altered. Long-term exposure to sunlight and cigarette smoking have been associated with a greater incidence of nuclear sclerosis. Vitamin supplements have been advocated, but never shown to prevent cataract.
Theoretically, dilation of the pupil will improve vision with axial opacities. In reality, the excess light allowed into the eye creates discomfort and is of little practical utility.
2. Surgical: almost 100% of laymen (and some physicians) believe incorrectly that lasers can be used to remove cataracts. This confusion results from the use of a laser (YAG) AFTER cataract surgery to remove the opacity of the remaining lens capsule.
In healthy eyes, cataract surgery is successful in over 95% of cases. This high rate is diminished in otherwise diseased eyes. Conditions complicating the result of cataract surgery include: glaucoma, macular degeneration, diabetic retinopathy, retinal detachment and optic nerve injury.
Corneal dystrophy is a pre-existing condition which can progress to corneal transplantation after the added trauma of surgery. The need for preoperative discussion of risk/benefit ratios and outcome predictions is the most important thing a physician can do to ensure a satisfied patient.
The surgery itself begins in the office after obtaining informed consent by making the measurements necessary to choose the intraocular lens implant power (see Figure 3). The corneal curvature (keratometry) and axial length of the eye are necessary for the calculation.
In most cases the surgery is performed under local anesthetic. After proper sedation, a combination of short-acting (lidocaine) and long-acting (marcaine) anesthetic is injected around the eye to eliminate eye movement and sensation.
The surgery itself takes 30–60 minutes. Modern cataract surgery is extracapsular in technique, leaving the posterior lens capsule intact. The lens implant is then placed in the capsular bag behind the iris. Intraoperative complications include rupture of the lens capsule, loss of the lens into the vitreous, and expulsive choroidal hemorrhage.
Postoperative visits are usually at one day, one week, and one, two, and three months. Visual acuity, intraocular pressure, refractor, slit lamp exam, and retinal exams are performed at each visit. Glasses are given at the two-month visit. Postoperative complications include glaucoma, corneal edema, retinal detachment, macular edema, and endophthalmitis.
In 25–50% of cases the posterior capsule opacifies, causing symptoms identical to the original cataract. This secondary cataract may be eliminated by using the YAG laser to ablate it in the office.
D. Customs of Cataract Surgery
Benefits of cataract surgery are innumerable. Restoring the ability to work and enjoy life are foremost among these. Reading, driving, golfing, sewing, quilting, reading music, cooking, and seeing a new grandchild are all appreciated by the postoperative patient.
Postoperative care includes topical steroids, antibiotics, mydriatics, and avoidance of direct trauma to the operative eye. Routine activities within reason may be continued.
E. Role of Non-Ophthalmologist Physician
A basic minimum knowledge about cataracts is of value to most physicians and of benefit to their patients. Cataract is by far the most common cause of the onset of visual disability in the elderly; fortunately, a dramatic cure is available. Perhaps the most important fact for the physician to know about cataracts is that glaucoma affects at least 5% of persons in the cataract age group.
Glaucoma is an insidious and invisible blinding disorder usually unrecognized by both patient and physician until too late to restore irreversible loss of sight. An individual patient who has symptoms of possible cataract must be evaluated to determine whether the symptoms are caused by cataract or by glaucoma or by both conditions together (or by something else, such as diabetes).
Accurate ocular differential diagnosis is exactly comparable to the same process of differential diagnosis of any other body system. This fact seems too obvious to mention; however, ophthalmology is an elective subject in many medical schools, with the consequence that many physicians are relatively unfamiliar with the great variety of eye disorders.
Giving advice and counseling is the all-important role of the primary physician with respect to cataract. Patients respect primary MD’s and rely upon their recommendation as to the detection, meaning and management of symptoms and problems. Whether a patient even visits an ophthalmologist and which ophthalmologist is selected can be greatly influenced by the trusted primary physician.
As an ophthalmologist, I am also a physician and can make appropriate medical judgments myself. Nevertheless, I find that patients fortunate enough to enjoy a long relationship with a primary physician friend are greatly helped by that friend’s concurrence in decisions to have any major health care intervention, such as a cataract operation.
Figure 3: The Correction of Aphakia
Optimal control of chronic disease problems is helpful prior to cataract surgery. This is particularly important with respect to any disorder that could interfere with the patient’s lying down during the operation. For example, a severe chronic cough or cardiac decompensation requires attention before elective surgery.
The decision as to whether surgery is justified will be modified by a patient’s life expectancy, which is not always evident during an ophthalmology visit. A practical issue for the patient may be a managed health care plan requiring referral by the primary M.D. before reimbursement to the patient is allowed.
With certainty, many of the 1 million elderly patients undergoing cataract surgery annually will visit other physicians for other problems during their postoperative period. Although convalescent eye care is the responsibility of the surgeon, patients will often want their primary physician to verify the proper progress of the eye surgery recovery and may volunteer ocular complaints. The following criteria may be used to evaluate recently performed cataract surgery:
1. General Behavior – Postoperative cataract patients should behave fairly normally. They should not remain constantly in bed, refuse to eat, or otherwise withdraw from activity. Such behavior may be due to mental changes, anesthesia or medications, or may indicate serious surgical complication (or injury). Altered behavior should alert the family and the physician to the presence of a problem requiring evaluation.
2. Vision – Generally, visual activity should improve progressively following surgery. Conversely, progressive loss of vision during convalescence is most unusual and would justify prompt evaluation by the surgeon.
Intraocular lens implantation restores vision much more rapidly than otherwise possible. In most cases, vision will be improved over the preoperative status on the first day after surgery. Maximum vision will be attained within one to three months. Almost always, eyeglasses are helpful in achieving the best possible vision. Final refraction should be done several months after surgery, when healing is complete.
3. Pain – Because of the well-known great sensitivity of the eye to even minor abrasions or tiny surface foreign bodies, many people falsely assume that a penetrating wound or a cataract operation will always be quite painful. In fact, after cataract extraction (which entails about a half-hour of manipulation—far more trauma than the entry of a 1 mm foreign body into the eye), most patients will have only slight discomfort. This usually occurs several hours after surgery, when the anesthetic has worn off. The pain is usually relieved by one or two aspirins and should never require narcotics such as meperidine.
A few patients complain much more, some less. The amount of complaint induced by minor pain is usually related to its implications to the patient. Expected pain is tolerated well by most persons. Apprehension that discomfort may signify a major complication will almost always be distressing.
If the eyelids open easily and comfortably, the recently operated eye is usually healing well. Involuntary squeezing shut of the lids upon examination is due to light sensitivity or apprehension and is not alarming. Persistent resistance to opening of eyelids after cataract extraction is unusual and deserves evaluation. However, do not force open the eyelids to examine a recently operated on or injured eye lest damage result.
4. Discharge – Small amounts of adherent mucus and crusts on the eyelid margins and the eyelashes result from the normal defensive secretion of mucus in response to the irritation of surgery. Sticking together of the eyelashes with mucus is common at first postoperative dressing. Persistent and abundant discharge signifies surface infection, which requires attention.
Abundant watering of the eye represents reflex tearing from minor irritation. Slight red discoloration of tears or mucus, staining the first dressing eye pad, is from incision and is insignificant.
5. Conjunctiva – For a week or more after eye surgery, the conjunctiva will be reddened, either because of capillary dilation or because of minor subconjunctival hemorrhage. The location of the incision site (the superior limbus, in most cataract surgery) will be the reddest part of the eye. Chemosis (marked conjunctival redness and swelling that may be so severe as to protrude between the lids) never develops after uncomplicated cataract surgery. A combination of unexpected findings, such as conjunctival swelling and persistent pain, deserves much more concern than one symptom alone and must not be ignored.
6. Cornea – Following uncomplicated cataract extraction, the cornea should always be perfectly transparent and clear. Cloudiness of the cornea is a sign of significant damage, which might result from injury, infection, or glaucoma. Do not confuse this with mucus debris adherent to the corneal surface, recognizable because it moves freely with each blink of the eyelids.
7. Anterior Chamber – The anterior chamber MUST be formed (filled with aqueous). If the iris bows forward to touch the cornea (flat chamber), either the incision is leaking or the normal flow of aqueous through the pupil is blocked. Each of these is an extremely serious problem requiring immediate action!!
Blood and pus are heavier than aqueous and settle to the bottom of the anterior chamber with a gravity-oriented flat top. Look carefully at the bottom of the anterior chamber to rule out the presence of a red or a white deposit (called hyphema or hypopyon, respectively). Either one is of a very serious import.
8. Iris – If the details of the iris cannot be clearly seen, either the cornea or the anterior chamber have lost their normal transparency, definitely an abnormal circumstance. The pupil should be rounded and central.
Upward displacement of the pupil may mean prolapse of the iris through a ruptured incision or vitreous loss through the incision (both are major surgical complications). A small black spot on the upper iris may be a peripheral iridectomy, which is often performed as a routine step in the cataract operation.
The pupil and the iridectomy appear jet black on inspection with a flashlight, but glow with the red reflex when observed through an ophthalmoscope (the same black or red appearance results from a traumatic perforation of the iris).
Absence of the red reflex means a loss of vitreous transparency, as from blood, pus, or other debris suspended within the eye. Gray or white discoloration of the pupil is caused by retained cataract fragments or masses of purulent debris.
9. Incision – To view the incision site at the upper limbus, lift up the eyebrow by pressure upon the bony orbital rim and ask the patient to look down. The conjunctiva above a recent incision is normally reddened and slightly edematous. Tiny radial sutures are usually visible. The edges of the incision should be perfectly opposed with no visible separation anywhere.
A ruptured incision is recognizable as a separation of the edges between which dark iris or transparent vitreous may protrude. An eye with faulty closure of the incision is vulnerable to destruction by only the slightest external pressure or even by contraction of the extraocular muscles, such as in eye movement.
10. Fundus – Because of the sensitivity to the light and a tendency to collection of mucus debris on the corneal surface, the ophthalmoscopic view of the fundus of a freshly operated on eye may not be very good. A good red reflex should be easily seen.
11. General advice – Please don’t meddle with a recently operated on or obviously injured eye unless you know how to handle it and what to look for. NEVER press upon it. If you are not sure what to do, DON’T do it. Upon recognition of a ruptured incision or penetrating wound, STOP manipulating the eyelids, apply a SHIELD securely, and immediately call your ophthalmologist.
From the preceding descriptions, you know that abnormalities of the cornea, anterior chamber, iris, pupil, and incision are the most important signs of serious trouble in a recently operated on or injured eye. You will see these best with side illumination from a bright flashlight.
You will understand what you see better if you have studied a normal eye (and perhaps some diseased ones also) with a slit lamp microscope and are familiar with the anatomy and normal appearance. Please do this in the eye clinic.
F. Summary
A cataract causes reduction of vision comparable to the blur of the ophthalmoscopic view. Its presence is usually identifiable by a history of glare or of increasing myopia in adult life. Ophthalmoscopic recognition of the opacity confirms the diagnosis. Because other disorders commonly exist in an eye old and sick enough to have a cataract, referral to an ophthalmologist is proper even though it is too early for surgery.
Surgery, the only effective therapy for cataract, should not be performed until the patient’s vision is sufficiently reduced to warrant the discomfort, inconvenience, time, expense, and risk that will inevitably accompany the operation.
