Age-related cataracts affect more than 22 million Americans, and that number may rise to 30 million by 2020.1 In the United States, almost 20% of older adults aged 65 to 74 years have cataracts that interfere with their vision.2 While cataract surgery rates are rising in all age groups between 50 and 90 years, it appears that the greatest increase is in those aged 70 to 80 years, owing in part to aging baby boomers who are working longer, desiring to be more active, and placing more demands on their vision.3 With regard to the U.S. Medicare population, cataract extraction is the most commonly performed surgical procedure, and both the annual total volume and age-adjusted rates of cataract surgery have increased substantially since the 1980s.4 Furthermore, it is estimated that at least 80% of cataract surgery in this country is performed on Medicare beneficiaries.4,5
Many individuals have no risk factors other than age; however, some cataracts are congenital and are associated with numerous syndromes and diseases, such as diabetes. Cataracts usually develop slowly over a period of years and are the leading cause of blindness worldwide.2
Pharmacists can educate patients regarding the modifiable risk factors for cataracts, which include taking systemic corticosteroids; poor control of blood glucose; the use of alcohol and tobacco; and chronic ultraviolet light exposure (TABLE 1). A diet high in vitamin C, vitamin A, and carotenoids (i.e., contained in vegetables such as spinach and kale) may protect against cataracts, and ophthalmologists often recommend ultraviolet-coated eyeglasses or sunglasses as a preventive measure.2 Furthermore, pharmacists can inform patients who are experiencing signs and symptoms of cataracts (TABLE 2) that the surgical removal and placement of an intraocular lens is usually indicated if the cataract contributes to visual loss that interferes with activities of daily living, causes bothersome glare, or reaches certain degrees of severity as determined by their eye-care physician. Additionally, while major complications of cataract surgery are rare, pharmacists should become familiar with the risks for and drug treatment of postoperative endophthalmitis.
Infectious Complication of Cataract Surgery
Postoperative endophthalmitis is defined as severe inflammation involving both the anterior and posterior segments of the eye following intraocular surgery. This complication of cataract surgery can occur within the first week; while very rare, it may result in irreversible blindness.2 Postoperative endophthalmitis is typically caused by the perioperative introduction of microbial organisms into the eye either from the patient’s normal conjunctival and epidermal flora or from contaminated instruments; other risk factors are listed in TABLE 3.6 Endophthalmitis may also manifest within 6 weeks—or even months or years after the procedure—if slow-growing organisms are involved.6 Of note, since overwhelming inflammation is likely to occur once organisms gain access to the vitreous cavity, rapid recognition, diagnosis, and treatment are critical in order to optimize therapeutic outcomes.6
Pharmacists should be aware that there are other rare complications of cataract surgery, which include intraoperative complications such as bleeding beneath the retina, vitreous prolapsing out of the incision, cystoid macular edema, bullous keratopathy (i.e., swelling of the cornea), retinal detachment, and posterior capsular opacification.2
Drug Treatment of Postoperative Bacterial Endopthalmitis
Clinicians usually obtain vitreous and aqueous samples to identify the offending organism via microbiologic laboratory studies.7 Drug therapy must be comprehensive and cover all likely pathogens in the context of this clinical setting; agents recommended for use in acute postoperative endophthalmitis following cataract surgery are used off-label as follows:
Vancomycin is indicated for treatment of serious or severe infections secondary to gram-positive organisms; this agent has been shown to be effective against more than 99% of gram-positive endophthalmitis isolates.6 The usual vancomycin dose is 1 mg/0.1 mL normal saline (NS) instilled into the vitreum; administration may be repeated, if necessary, in 2 to 3 days, usually in combination with the broad-spectrum third-generation cephalosporin ceftazidime or an aminoglycoside (e.g., amikacin).8 Intravitreal amikacin (0.4 mg/0.1 mL NS in combination with vancomycin) is useful for gram-negative coverage because approximately 90% of gram-negative isolates are susceptible to this agent.6,8 However, since ceftazidime demonstrates gram-negative sensitivity profiles similar to those of the aminoglycosides—and is not associated with retinal toxicity—it is a reasonable alternative for gram-negative coverage.6,7 Intravitreal ceftazidime is dosed 2-2.25 mg/0.1 mL NS in combination with vancomycin.8-10 Notably, in light of concerns for retinotoxicity, some clinicians have recommended the use of a lower vancomycin dose of 0.2 mg/0.1 mL; this may be repeated in 3 to 4 days if necessary.8,11
Corticosteroid use can cause profound and varied metabolic effects while modifying the body’s immune response to diverse stimuli.6 The use of intravitreal dexamethasone in the treatment of acute postoperative endophthalmitis remains controversial.7,12 Some clinicians use this short-acting corticosteroid agent to inhibit inflammation secondary to bacterial endotoxins, host factors, and antibiotics; this agent decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reducing capillary permeability.6 Currently, the available evidence does not support the routine use of adjunctive intravitreous corticosteroids in the treatment of acute endophthalmitis.13
Conclusion
With cataract surgery rates on the rise in adults between ages 50 and 90 years, pharmacists need to be aware of the risk for complications associated with this surgery. Acute postoperative endophthalmitis after cataract surgery, which involves severe inflammation, requires rapid recognition, diagnosis, and treatment to optimize outcomes. Guidance by pharmacists regarding appropriate dosing, as well as patient and caregiver education, is encouraged in all practice settings.
REFERENCES
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