- 1.
What are the indications for cataract surgery?
In general, the decision to have cataract surgery is elective. It is based on a patient’s personal needs and the physician’s judgment as to the probability of vision improvement. For some people, even a slight loss of vision is unacceptable. Others may choose to delay surgery because their cataracts do not seriously interfere with their lives. The key question is whether the patient perceives the cataract as interfering with his or her quality of life. Of course, the physician must be aware of state visual acuity requirements for driving.
- 2.
What are two nonsurgical methods of managing a cataract?
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Refraction: Patients with a cataract may experience a myopic (nearsighted) shift or so-called second sight. Occasionally, glasses can compensate for such shifts. However, if the shift is large and unilateral, binocular vision may be compromised by image size differences between the two eyes. This anisometropia may push patients to have surgery.
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Pupillary dilation: An expanded pupil allows light rays to enter around a central cataract (such as a posterior subcapsular cataract) rather than be blocked by light rays that attempt to pass through a hazy cataract.
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- 3.
What preoperative tests are used to gauge visual impairment?
No single test adequately describes the effect of cataracts on a patient’s visual functioning, but the most widely used tests are:
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Snellen visual acuity (i.e., 20/20).
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Potential acuity testing. This test estimates postoperative visual acuity by projecting a Snellen acuity chart through the patient’s cataract. Most often, it is used to determine whether a patient’s visual symptoms are due more to cataract or to retinal disease.
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Glare/contrast sensitivity testing. This test simulates lighting conditions outdoors and determines a patient’s vision when functioning under more normal conditions. The high-contrast situation in a Snellen test can overestimate a patient’s abilities. A patient may have 20/40 acuity in a dark room but may have 20/100 with glare testing, which could significantly impair driving.
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- 1.
Snellen visual acuity
- 2.
Potential acuity testing
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Glare testing
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Contrast sensitivity testing
- 4.
What are the basic steps in removing a cataract?
- 1.
The pupil is dilated with medications.
- 2.
The eye and eyelids are disinfected with an antiseptic, usually iodine based.
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The eye and eyelids are anesthetized, and a speculum is placed to keep the eyelids open.
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An incision is made into the anterior chamber (AC).
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A viscoelastic (viscous, protective gel) is injected into the AC.
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The anterior capsule is opened with a capsulotomy or capsulorrhexis to gain access to the lens mass.
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The nucleus is removed manually or by phacoemulsification.
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The residual cortex is removed.
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An intraocular lens (IOL) is inserted.
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The wound is closed.
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- 5.
How is the eye anesthetized for surgery?
Most surgeons prefer local rather than general anesthesia for adult cataract surgery. Less commonly, facial akinesia with a short-acting agent such as lidocaine or hyaluronidase (a diffusion enhancer) may be given to prevent squeezing of the eyelids during surgery. There are three types of local anesthesia:
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Retrobulbar: Anesthetic (usually a combination of a short- and a long-acting agent with hyaluronidase) is injected inside the muscle cone to achieve akinesia and anesthesia of the globe ( Fig. 22-1 ).
Figure 22-1
Retrobulbar injection. If the tip of the needle strikes the floor of the orbit as it is inserted (see 1 above), it is withdrawn slightly and directed more superiorly (see 2 above).
(From Jaffe NS, Jaffe MS, Jaffe GF: Cataract surgery and its complications. St. Louis, Mosby, 1990.)
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Peribulbar: Anesthetic is injected outside the muscle cone. Although this block takes longer to take effect (12–25 minutes), there are fewer potential complications because a shorter needle is used.
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Topical: Advances in technology have allowed skilled surgeons to perform the cataract procedure in 10–15 minutes. With such short operative times, prolonged anesthesia and akinesia become less critical. Topical drops or gels of short-acting agents such as lidocaine or tetracaine may be used to anesthetize the eye sufficiently to complete the procedure. The advantage to the patient is instantaneous binocular vision postoperatively without the risk of injection-related, potentially sight-threatening complications.
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Intracameral: As an adjunct to or substitute for topical anesthetics, intraocular administration of preservative-free lidocaine with or without dilating agents is being adopted by many surgeons.
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- 6.
What are the disadvantages of topical anesthesia for cataract surgery?
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Because there is no akinesia, the eye can move during surgery.
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Patient selection is crucial. Patients need to be able to follow the commands of the surgeon.
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- 7.
What is couching?
Couching is one of the most ancient surgical procedures and it was the first known technique of cataract removal. Although, the technique was first described by the Indian physician Susruta ca. 800 BC, copper surgical instruments that could have been used for couching have been found in the tomb of the Egyptian king Khasekhemwy ca. 2700 BC 11 . Popular in the United States until the 1850s, couching involves piercing the eye with a needle, then dislocating the entire lens backward and downward into the posterior chamber. Although it may seem crude by modern surgical standards and prone to myriad complications, it is still performed in the Third World where advanced technology is not available.
- 8.
What are the two most common ways to remove a cataract?
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Intracapsular surgery was the procedure of choice from its discovery by Jacques Daviel in 1752 until the early 1970s. It is accomplished with a cryoprobe, an instrument that freezes the tissue. Intracapsular surgery is rarely performed in the United States today except in cases of dislocated lenses.
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Extracapsular cataract extraction (ECCE) is the most popular technique. There are two types—manual extraction and phacoemulsification. Both methods require the use of an operating microscope that permits magnification. In extracapsular surgery the anterior capsule of the lens is removed, the hard nucleus is expressed, and the remaining soft cortical fragments are removed with either an automated or a manual device ( Fig. 22-2 ). The advantage of extracapsular surgery is preservation of the posterior capsule, which permits a pocket for an intraocular lens. This method also minimizes the complications associated with vitreous loss.
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