Ophthalmology ( or ) is the branch of medicine that deals with the anatomy, physiology and diseases of the eyeball and orbit. An ophthalmologist is a specialist in medical and surgical eye disease. Their credentials include a doctorate degree in medicine, followed by an additional four years of Ophthalmology residency training. Additional training may be sought through a fellowship in a particular specialty of eye pathology. Ophthalmologists are allowed to medically treat eye disease, prescribe glasses or contact lenses, implement laser therapy, and perform surgery when needed. Ophthalmologists may participate in academic research on the diagnosis and treatment for eye disorders.