, do you mean that your nearsighedness is the only sign of
Marfan Syndrome? In this case, you do not have
Marfan Syndrome. First, do a web search for Marfan Syndrome (start with wikipedia) and educate yourself about that condition. Whether you have it or not is critical to any suggestions regarding your vision. Second, -6 myopia is only moderate myopia. People with Marfan Syndrome usually have extremely high prescriptions, often with high astigmatism. So this doesn't fit either.