There are two types of eye doctors: optometrists and ophthalmologists. Both specialize in eyes and vision but have different qualifications.
Optometrists are Doctors of Optometry (OD) but not MDs. They can perform eye and vision exams and prescribe glasses and contact lenses. They can detect other eye diseases and problems but have to refer to an MD for treatment. They cannot perform surgery.
Ophthalmologists are eye doctors that are also medical doctors. They are MDs and can treat all eye diseases such as glaucoma, cataracts, and macular degeneration. They can perform surgery including LASIK.
There are several common eye diseases that can lead to loss of vision or blindness. Cataracts is blurry vision caused by the eye lens becoming cloudy. Glaucoma is optic nerve damage caused by high pressure in the eye. Symptoms include eye pain, headaches, and blurry vision. Macular degeneration is a damaged macula that prevents clear central vision. Treatments include medication, eye drops, and surgery.