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Glaucoma is a group of disorders in which increased pressure within the eyeball (intraocular pressure) can damage the eye and cause impaired vision, ranging from slight impairment to complete blindness. The pressure is caused by an imbalance between production and drainage of the intraocular fluid (aqueous humor). The goal of treatment is to lower the abnormal pressure, which often can be accomplished with medication . The drugs commonly used for this purpose include beta-blockers, which decrease intraocular fluid production by opposing certain actions of the sympathetic nervous system.
Many patients taking beta-blocking drops to control their glaucoma spend much more than is necessary. The true cost depends not only on the ingredients, but also on the volume of fluid in the product, the frequency of use, and the design of the bottles in which they are sold. Several studies have found significant differences. A key difference appears to be the design of the bottles. Some bottles deliver an adequate and accurately metered small drop, whereas others dispense drops that are larger than necessary. The difference can result in spending up to twice as much money for the same benefit.
The amount of fluid in the film of tears covering the eyeball is 7 to 10 microliters (µl). Pharmacologic studies have shown that maximal concentration of medication can achieved by administering a 20 µl drop. Commercial beta-blocking eyedrops usually contain 50 to 70 µl. Other studies have shown that the size of the drop can be reduced by modifying the eyedropper tip .
The most commonly used beta-blocking products contain either timolol or levobunolol, which are equally effective in reducing intraocular pressure . However, several studies have have found timolol products less expensive to use.
A comparison of the 1991 retail cost of timolol, levobunolol, metipranolol, and two other commercially available beta-blockers found that variations in bottle volumes and drop size combined to yield up to a 48% differential in number of drops per bottle. The investigators also found average retail price variations were 28% within brands (between pharmacies), 29% between brands, and 29% between regions and that yearly costs were consistently less with larger bottles. Factoring drops-per-bottle, cost of brand, and cost by pharmacy, the cost of a year's supply of beta-blocker in 5-ml bottles in the least expensive region (New Orleans) ranged from $52.25 for metipranolol to $278.91 for levobunolol . A subsequent study found that Merck's 5-milliliter bottles of 0.5% timolol maleate lasted an average of 36.6 days, while bottles of Allergan's 0.5% levobunolol lasted an average of 28.9 days, a 21% difference .
Another study compared several sizes of bottles of timolol and levobunolol by having patients dispense drops into a cylinder. The researchers concluded that the cost of use would depend on the size of the drop, the volume of medication in the bottle, and the frequency of administration. The timolol products, which yielded smaller drops, could save patients from $44 to $87 per year . Yet another study found that nongeneric timolol averaged 193 drops and nongeneric levobunolol averaged 220 drops per 10-ml bottle .
In 1997, an ophthalmologist compared three timolol products, one levobunolol product, and four products containing other beta-blockers and found that the cost per day ranged from 29¢ to 76¢ when the dropper was held at a 45° angle and from 30¢ to 79¢ per day when the dropper was held at a 90° angle. The most expensive product by far was Betagan, the original brand of levobunolol marketed by Allergan . Betagan's patent expired in 1991, which means that other companies could market generic versions. However, it had been aggressively promoted to physicians through journal ads, free dinners, and other means -- and, as a result, was commonly prescribed even though it cost more per milliliter and delivered fewer drops per bottle.
If Betagan is prescribed for you, shop for a less-expensive generic whose bottle delivers smaller drops, and hold the dropper at a 45° angle when dispensing them. If a newer medication is prescribed, keep track of the number of drops the bottle yields so you can compare the cost of competing products.
Dr. Nevyas, an ophthalmologist who specializes in refractive surgery, is also Clinical Professor of Ophthalmology at the Medical College of Pennsylvania. His main office and ambulatory surgical center are located in the Philadelphia area at Two Bala Plaza, Bala Cynwyd, PA 19004. Telephone: (610) 668-2777.