Melatonin is effective for macular degeneration according to current research.
As the leading cause of sight degeneration among Americans over the age of 60, center vision blurriness or blinds spots caused by macular degeneration are a serious problem.(1) As researchers continue to try and find an effective cure, some headway has been made in recent years with the use of the hormone melatonin.
In 2005, an article published in the Annals of the New York Academy of Sciences showed that melatonin, a sleep-inducing hormone produced by the human brain, had also had positive impact when administered to people with macular degeneration. A nightly dose of 3 milligrams was shown to have stabilized the vision of study participants and reduced visible signs of the disease. 
More recently, a speculative 2010 study argued that melatonin helps the cells of the retina repair themselves after damage caused by ailments such as macular degeneration. The researcher, Dr. Reza Rastmanesh, also posited that melatonin might be an agent that helps mitigate the presence of nitric oxide as well as vascular endothelial growth, two contributing factors to macular degeneration. 
The list of conditions that melatonin has been shown to positively impact is long and impressive, everything from anxiety and diabetes to stroke and Tinnitus.(4) Separate research classifies the hormone as a possible generator of anti-oxidant effects when it comes to macular degeneration.
But each and every scientific analysis of this use of melatonin ends with the warning that more exhaustive and clinically sound data is needed to conclusively prove the hormone’s reversing power on the most common eye disease among older Americans.
At this stage, though, the good news for those dealing with macular degeneration is that melatonin is a cheap, over-the-counter solution.(5) Most of the tablet forms of the hormone are marketed as a treatment for sleep deficiencies, however, rather than retina problems. But as more eye-specific findings are tabulated to go along with the impressive broader sampling of macular degeneration patients done by a Chinese team in 2005, it appears likely the miraculous reach of melatonin will soon have one more fully confirmed domain.(6)
Macular Degeneration Association – Melatonin for Prevention of Macular Degeneration, Retrieved June 13,
[!] Annals of the New York Academy of Sciences, CHANGXIAN YIEffects of Melatonin in Age-Related Macular Degeneration2005, Volume: 1057, pages: 384-392
- [@] Medical Hypotheses, Rastmanesh
Potential of melatonin to treat or prevent age-related macular degeneration through stimulation of telomerase activity
2010, Volume: 76, Issue: 1, pages: 79-85
(4) Mayo Clinic – Melatonin: Evidence, Retrieved June 13, 2011 from http://www.mayoclinic.com/health/melatonin/NS_patient-melatonin/DSECTION=evidence
(5) GNC – Melatonin, Retrieved June 13, 2011 from http://www.gnc.com/product/index.jsp?productId=4238831&lmdn=Ingredient&camp=PPC%3A733240082&002=2269848&004=2022896114&005=379079783&006=6382496954&007=Search&008=&cp=3703246#showReviews
 National Institutes of Health – Effects of Melatonin in Age-Related Macular Degeneration, Retrieved June 13, 2011 from http://www.ncbi.nlm.nih.gov/pubmed/16399908