In what way can i reduce my eye sight of 0.5?

Depends on cause: If you are describing your visual acuity in decimal form (0.5) for 20/40 vision, then it depends on the cause of the reduced vision, for which there are many possibilities. If you are stating you refractive error (+0.50 or -0.50), then there is little you can change your refractive error. Glasses or contacts will correct it. Lasik will also correct it, but 0.50 is likely too small for surgery.