The causes of macular edema are numerous and different causes may be inter-related. It is commonly associated with diabetes. Chronic or uncontrolled diabetes type 2 can affect peripheral blood vessels including those of the retina which may leak fluid, blood and occasionally fats into the retina causing it to swell.
Visual C++. Visual C++ is known as a native development language, as it talks directly to the hardware for the Windows Mobile device, with no intervening layers (unlike Visual C#, for example). Programming using C++ can be challenging, as it is not a trivial language to learn.
The languages in the first cluster, Java, C, Python, and C++, are pretty much universal languages. They're not tied to a specific programming platform or focus. The most interesting clue is the second cluster, containing JavaScript, C#, PHP, and Swift. JavaScript and PHP are mainly web development languages. C# is a Microsoft-centric language. Swift is Apple's new main coding language. Fundamentally, the second cluster is platform-specific.