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Editor's note: A previous version of this article incorrectly described the Medicare prescription drug coverage "donut hole." The author and the Fool regret the error.

The Patient Protection and Affordable Care Act, better known as Obamacare, has changed the face of American healthcare, and despite its controversy and challenges from critics, the law has thus far stayed the course. In particular, Obamacare created benefits for many Americans, including the availability of health-insurance exchanges that allow the uninsured to obtain qualifying coverage. Yet beyond providing insurance for those of working age, there are also lesser-known Obamacare benefits for senior citizens that some Americans have no idea exist. Let's look at four of the most important benefits of Obamacare that many seniors don't know about at all.

1. Closing the "donut hole" for Medicare prescription drug coverage.
Medicare Part D provides prescription drug coverage for those seniors who are eligible for Medicare and choose to participate. Yet many seniors have faced one of Medicare Part D's biggest shortcomings: a coverage gap that most people refer to as the donut hole. Before Obamacare, Medicare Part D paid the bulk of drug costs up to a certain amount, which was $2,830 in 2010. Many people paid only 25% of that initial level of drug costs once they had paid their deductible, which in 2010 was $310, leaving the total seniors had to spend out-of-pocket at $940. Above that amount though, Medicare Part D covered nothing, leaving seniors responsible for all drug costs. Only once your total out-of-pocket spending went above a higher amount -- $4,550 in 2010 -- would coverage kick back in, and participants would bear only a tiny amount of the cost for prescription drugs above that amount.

Obamacare set up a schedule of discounts for brand-name and generic drugs within the donut hole. In 2011, Medicare participants got a 50% discount on brand-name drugs and a 7% discount on generics. For 2015, those discounts have risen to 55% and 35% respectively. Importantly, even though seniors don't pay the discounted amounts, those discounted are counted against the out-of-pocket maximum for purposes of calculating where the donut hole ends. The end goal is to leave seniors responsible for only 25% of their drug costs by 2020. That will effectively match basic coverage under the standard Part D model, making the donut hole disappear in the eyes of most policymakers.

2. Annual wellness and preventive care exams for seniors under Medicare.
Many health experts have noted that providing coverage for preventive care can head off more costly treatment for injury or illness later. That's a big motivation for Obamacare's provision of preventive services for seniors through an annual wellness exam.

The wellness visit is intended to review your medical and family history, with the goal of taking routine measurements on your physical condition and building a list of current healthcare providers and any prescription drugs you take. By providing personalized health advice, the wellness visit can establish lists of risk factors and treatment options for any conditions you have. In addition, a wide variety of screenings are available, ranging from vaccinations and cancer checks to obesity treatment and glaucoma tests. Many of these services come at no cost, although a few of the screenings require you to cover the ordinary 20% co-payment under Medicare Part B.

3. Financial assistance for covering some costs for low-income American seniors.
Low-income seniors have historically had difficulty obtaining the financial assistance they need to cover healthcare costs, despite often having coverage under both Medicare and Medicaid. Obamacare added some additional financial options for low-income seniors, including the elimination of cost-sharing provisions for prescription drug coverage for those who receive home-based or community-based care. Certain long-term care options are also designed to help low-income recipients get the care they need while staying in their homes.

4. Better information on nursing homes and other long-term care options.
Many seniors need long-term care in nursing homes and other facilities, but before Obamacare it was difficult to get certain information about such options. Under healthcare reform, seniors can get information about nursing homes, such as how much money goes toward care compared to administrative costs, as well as staff turnover rates and the hours of care provided per resident. A database of complaints and any violations also lets seniors know if a given facility has a good reputation.

Obamacare divides the nation, with strong debate from Americans on both sides of the issue. Nevertheless, one thing is clear: Obamacare has brought considerable benefits to senior citizens, and taking advantage of everything the program has to offer can help you make ends meet during your retirement years.

Dan Caplinger has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.