Cataracts
- 1.
Explain the derivation of the word cataract.
Cataract comes from the Greek word cataractos, which describes rapidly running water. Rapidly running water turns white, as do mature cataracts.
- 2.
What is the leading cause of blindness worldwide?
Believe it or not, cataracts, which are treatable, remain one of the leading causes of blindness worldwide.
- 3.
What is a nuclear sclerotic cataract?
A nuclear sclerotic cataract describes the sclerosis or darkening that is seen in the central portion of the lens nucleus. This type of cataract is typically seen in older patients. As the equatorial epithelial cells of the lens continue to divide, they produce compaction of the more central fibers and sclerosis.
- 4.
What produces the brown color seen in cataracts?
The brown color comes from urochrome pigment.
- 5.
What is “second sight?” How is it associated with nuclear sclerotic cataracts?
As patients develop nuclear sclerotic cataracts, the increased density of the lens causes the patient to become increasingly nearsighted. As a result of their nearsightedness, many patients who required spectacles to help them read find that they are able to read small print up close without glasses. In the past, this phenomenon was termed “second sight.” Of interest, patients erroneously believe that their eyes are getting stronger or better, whereas the opposite is the case. Second sight indicates progression of the cataract.
- 6.
What are the typical symptoms of nuclear sclerotic cataracts?
In general, all types of cataracts cause decreased vision. Nuclear sclerotic cataracts tend to cause problems with distance vision but preserve reading vision because of the above-mentioned nearsightedness.
- 7.
What are posterior subcapsular cataracts?
Posterior subcapsular cataracts are granular opacities seen mainly in the central posterior cortex just under the posterior capsule. They have a hyaline type of appearance.
- 8.
What are the symptoms of posterior subcapsular cataracts?
Unlike patients with nuclear sclerotic cataracts, patients with posterior subcapsular cataracts often have good distance vision but typically have blurred near vision. In addition, patients with posterior subcapsular cataracts often have extreme difficulty with glare so that in dim illumination they function well, whereas with bright illumination their vision decreases significantly.
- 9.
What are the associated systemic findings in patients with cataracts?
In general, nuclear sclerotic cataracts are seen in elderly patients, although they may occur in young patients as well. In younger patients, they are often associated with high myopia.
Posterior subcapsular cataracts are common in patients with diabetes, patients who have taken steroids, and patients with a history of intraocular inflammation, such as uveitis.
- 10.
What are the major potential causes of cataracts in infants?
Common causes of congenital cataracts include familial inheritance, intrauterine infection (e.g., rubella), metabolic diseases (e.g., galactosemia), and chromosomal abnormalities. Complete evaluation by a pediatrician is mandatory for any infant with a congenital cataract.
- 11.
What is a morgagnian cataract?
A morgagnian cataract is a mature cataract in which the cortex liquefies and the mature central nucleus can be seen within the liquefied cortex.
- 12.
What is phacolytic glaucoma?
Phacolytic glaucoma may occur with morgagnian and mature cataracts. Liquefied cortex traverses the capsular membrane and enters the posterior chamber, producing an inflammatory response that clogs the trabecular meshwork and results in elevated intraocular pressure.
- 13.
What is phacomorphic glaucoma?
As the cataract matures, the lens becomes enlarged (intumescent). As the lens enlarges, it pushes the iris root and ciliary body forward, narrowing the angle between the iris and the peripheral cornea in the region of the trabecular meshwork. If the angle becomes narrow enough, the pressure may become elevated because of angle closure. Treatment involves removal of the cataract.
- 14.
What is pseudoexfoliation? What is its relationship to cataracts?
Pseudoexfoliation is a condition in which basement membrane material from the zonules and lens capsule is liberated onto the anterior lens capsule and anterior chamber. Patients with pseudoexfoliation have a predisposition for the development of glaucoma, presumably because of clogging of the trabecular meshwork by the exfoliated material. Patients with pseudoexfoliation often present a challenge for the cataract surgeon because their pupils tend to dilate poorly, and they often have weak or loose zonules that cause intraoperative complications with disinsertion of the zonules. Because of their propensity for developing glaucoma, patients often have postoperative pressure elevations.
- 15.
A patient underwent successful and uncomplicated cataract surgery, and years after the surgery, the intraocular lens (IOL) completely dislocated. What associated ophthalmic condition would the patient be likely to have?
The patient would be likely to have pseudoexfoliation.
- 16.
What is true exfoliation syndrome as opposed to pseudoexfoliation syndrome?
True exfoliation is found in glassblowers who stand in front of hot furnaces throughout the day. Large sheets of material come off the anterior lens capsule. Such cataracts are termed glassblower’s cataracts . With modern techniques of processing glass, they are no longer seen. Because the type of material produced in pseudoexfoliation seemed similar to the material produced in a glassblower’s cataract, it was termed pseudoexfoliation to distinguish it from the exfoliative material produced by heat exposure.
- 17.
What systemic syndromes should be considered in a patient with a spontaneously dislocated natural lens?
In these patients, the zonular support system has been disrupted. Spontaneous dislocation of the lens is most common in Marfan’s syndrome and homocystinuria. Typical patients with Marfan’s syndrome are tall, thin, and lanky and exhibit arachnodactyly. The lenses in Marfan’s syndrome tend to dislocate superiorly. In homocystinuria, the lenses tend to dislocate inferiorly. Trauma also should be considered in all patients with a dislocated lens. Rarely, pseudoexfoliation can be a cause.
Key Points: Dislocated and Subluxated Lenses
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