Now, the outer segments do not regenerate the retinal back into the cis- form once it has been changed by light. Instead the retinal is pumped out to the surrounding RPE where it is regenerated and transported back into the outer segments of the photoreceptors. This recycling function of the RPE protects the photoreceptors against photo-oxidative damage and allows the photoreceptor cells to have decades-long useful lives. In birds
The bird retina is devoid of blood vessels, perhaps to give unobscured passage of light for forming images, thus giving better resolution. It is, therefore, a considered view that the bird retina depends for nutrition and oxygen supply on a specialized organ, called the "pecten" or pecten oculi, located on the blind spot or optic disk. This organ is extremely rich in blood vessels and is thought to supply nutrition and oxygen to the bird retina by diffusion through the vitreous body. The pecten is highly rich in alkaline phosphatase activity and polarized cells in its bridge portion – both befitting its secretory role. Pecten cells are packed with dark melanin granules, which have been theorized to keep this organ warm with the absorption of stray light falling on the pecten. This is considered to enhance metabolic rate of the pecten, thereby exporting more nutritive molecules to meet the stringent energy requirements of the retina during long periods of exposure to light.
Aliskiren (brand names Tekturna and Rasilez) is the first in a class of drugs called direct renin inhibitors. It is used for essential (primary) hypertension. While used for high blood pressure, other better studied medications are typically recommended due to concerns of higher side effects and less evidence of benefit.In December 2011, Novartis halted a trial of the drug after discovering increased nonfatal stroke, kidney complications, high blood potassium, and low blood pressure in people with diabetes and kidney problems.As a result, in 2012:

A new contraindication was added to the product label concerning the use of aliskiren with angiotensin receptor blockers (ARBs) or angiotensin-converting enzyme inhibitors (ACEIs) in patients with diabetes because of the risk of kidney impairment, low blood pressure, and high levels of potassium in the blood. A warning to avoid use of aliskiren with ARBs or ACEIs was also added for patients with moderate to severe kidney impairment (i.e., where glomerular filtration rate is less than 60 ml/min). Novartis decided to stop marketing Valturna (aliskiren/valsartan).Aliskiren was co-developed by the Swiss pharmaceutical companies Novartis and Speedel. Medical uses
While used for high blood pressure, other better-studied medications are typically recommended. Prescrire has stated that aliskiren is potentially more harmful than beneficial and thus list it as a drug to avoid (as of 2014).