How vegetarian will get Omega 3 and Vitamin B12 that are so essential to brain development and eyesight
Omega 3 is not limited to only non vegetarian diet. Flax seed, nuts and so many other plant foods contain Omega 3.
Same with vitamin B 12. It is found in milk, which is one of the main food of vegetarian people. Cow ghee is another source of fatty acids, which is required for brain development. Glucose and fatty acids are playing main role in brain development. Glucose is obligatory source for brain function.
Brain development is not only related to food. Learning Sanskrit hymns, memorizing prayers, solving mathematical problems doing calculations related to astrology can also develop your brain. If you are using a particular part of body, it develops over the time, including brain.
Weekly once you should do fasting which now a days we are calling as Calorie Restrictions (CR).
Mix grain or Multigrain concept. Where you get a good variety of food and all possible vitamins.