What can patients expect from cataract surgery?

WHEN IS IT TIME FOR SURGERY?

In general, patients with cataracts describe a gradual decline in vision over a period of months to years. Patients who present with a sudden change or decrease in vision should therefore be referred immediately to an ophthalmologist.

In rare cases, cataract surgery is necessary because the cataract causes glaucoma or uveitis. Cataract extraction is also indicated if the patient has a posterior segment condition such as diabetic retinopathy and the lens has become too opaque for the ophthalmologist to see the retina clearly.

In general, though, surgery is only performed when the patient’s visual function has declined significantly. This is assessed by asking the patient whether decreased vision has affected his or her daily activities. Several questionnaires have been developed with the goal of improving the objectivity of this assessment; these include the Visual Function Index (VF-14)¹³ and the Activities of Daily Vision Scale, but they are not routinely used by practicing ophthalmologists.

Surgery is appropriate when the problems associated with the cataract outweigh the (small) risk of a bad outcome. The situation is obviously different for a patient who works, drives, or is active in sports vs a patient with dementia who is in a nursing home. Years ago, cataracts had to reach a certain consistency or “ripeness” to maximize the chances for success, and the surgeon decided when to operate, but with current technology the procedure can be performed equally well at any point. Hence, the patient usually decides if and when to have the surgery, and the surgeon provides helpful advice.

PREOPERATIVE EXAMINATIONS AND COUNSELING

Eye examination

Before cataract surgery, the patient undergoes a comprehensive ophthalmologic examination, including measurement of refraction, measurement of intraocular pressure, slit lamp examination, and examination of the retinal fundus with the pupils dilated. Other causes of impaired vision must be ruled out, such as glaucoma, age-related macular degeneration, and diabetic retinopathy.

Visual function is assessed by use of a vision chart that displays black letters on a white background. Glare effect can be measured by determining visual acuity under conditions of increased ambient lighting. In patients with coexisting eye problems, such as age-related macular degeneration, special testing and clinical judgment are needed to assess the potential value of cataract surgery.

Medical examination

Most surgical centers require a comprehensive medical assessment and laboratory testing before eye surgery. However, the rate of serious perioperative complications requiring hospital admission and the rate of death are so low when local anesthesia with intravenous sedation is used that studies have not found routine laboratory testing to have any effect on the rates of these bad outcomes.¹⁴

In general, patients taking aspirin or other anticoagulant drugs do not need to change their regimen before undergoing cataract extraction. However, measures of control such as the international normalized ratio should be within the therapeutic range.

The surgeon should be aware of other drugs the patient may be taking, such as tamsulosin hydrochloride (Flomax), which can cause iris instability and poor pupillary dilation.

Selecting the type of intraocular lens

After obtaining preoperative informed consent, taking the medical history, and performing a physical examination, the ophthalmologist examines the patient’s eye with the specific goal of choosing the type of synthetic intraocular lens.

Modern intraocular lenses were first used by Ridley¹⁵ in 1949. Designs and materials have since been refined, and implants can now improve and even correct a patient’s refractive error. To do this, the axial length and corneal curvature of the patient’s eye must be measured. Axial length is measured using ultrasonography, and corneal power is determined with keratometry. The choice of implant power determines whether the patient will be nearsighted, farsighted, or emmetropic after surgery, and this should be discussed with the patient beforehand.

ANESTHESIA FOR CATARACT SURGERY

Nearly all cataract operations are performed with sedation, not with general anesthesia. Local and topical anesthesia are almost always more time-efficient and cost-efficient.¹⁶

Retrobulbar and peribulbar injection: Higher risk of complications

Throughout most of the 20th century, anesthesia of the eye was accomplished by injecting lidocaine (Xylocaine), bupivacaine (Marcaine), or both into the retrobulbar space, ie, behind the eyeball. This procedure demands considerable training and technical skill to perform safely, as one cannot see the tip of the needle and must avoid orbital structures such as the optic nerve and the eye itself. Complications can include brainstem anesthesia, oculocardiac reflex, perforation of the globe, and retrobulbar hemorrhage.^16–20 Of these, retrobulbar hemorrhage is the most common; the reported incidence rate has ranged from as low as 0.44% to as high as 3%.^19,20

Peribulbar injection, a second type of regional anesthesia, involves injecting lidocaine or bupivacaine outside the muscle cone. This method also provides excellent anesthesia and is thought to have a lower risk of perforating the globe or penetrating the optic nerve.