(5) What are some of these other causes? Please explain.

There are many types of genes responsible for retinitis pigmentosa. Some are very virulent. If the patient having that type of gene, it is difficult to sustain improvement over a longer period of time and patient has to take up repeated courses of treatment every year or so but luckily these patients are very few in number. The other causes could be because of severely deranged body constitutions.