The eye is a highly complex organ, susceptible to a multitude of diseases and other problems.
Conditions such as nearsightedness and farsightedness are structural problems in the eyeball while diseases result from infections, ageing, or as the result of other diseases such as diabetes.
Astigmatism occurs when the cornea--the clear outer portion of the eye--is irregularly shaped, causing the light that enters the eye to be focused erratically. Double vision (diplopia) produces a second image and can occur temporarily or it can be a permanent condition. Higher-order aberrations (HOAs) result in difficulty with night vision, glare and halos, starburst patterns, or diplopia.
Hyperopia (farsightedness) affects close vision, causing it to be blurred while distant images are clear. Hyperopia occurs when the eyeball is too short and light focuses in back of the retina. Myopia (nearsightedness) patients can see close objects but have trouble with distance vision. The condition results when the eyeball is too long, causing the light to focus in front of the retina, producing a blurry image.
Peripheral vision problems are caused by such conditions as glaucoma and retinitis pigmentosa and result in decrease in side vision while central vision remains clear. Presbyopia is an age-related condition that begins in the 40s and gradually diminishes close vision.
Regular eye examinations are important to detect any developing eye issues or diseases before they show symptoms. Such symptoms as sudden loss of vision in one eye, sudden blurred vision, "floaters" or black spots, and halos around lights can indicate a serious eye problem such as a detached retina and demand immediate attention.
Eye care specialists are ophthalmologists, optometrists, and opticians. An ophthalmologist is a medical doctor (M.D.) or doctor of osteopathy (D.O.) who can perform eye evaluations, diagnose and treat eye disorders, prescribe medication, and prescribe eyeglasses and contact lenses. They can also perform eye surgery.
An optometrist has a doctor of optometry (O.D.) degree and can evaluate vision, prescribe lenses, and diagnose common eye problems. An optometrist can diagnose and treat eye disease and prescribe medications. More complex eye conditions require treatment by an ophthalmologist.
An optician is not an eye doctor but is a specialist who can fill eyeglass prescriptions from an ophthalmologist or optometrist.