amblyopia: often referred to as "lazy eye"; a condition caused by a lack of normal sight development in one eye during early childhood. This is a common ailment which occurs in approximately 2-3% of the population.
anti-reflective coating:thin layers of material added to the surface of a lens that reduce the amount of light refracted by the lens surface which reduces glare and improves optical quality.
astigmatism: a condition caused by an irregularity in the shape of the cornea which prevents light from focusing correctly on the retina thereby causing blurred vision. Symptoms may include headaches, fatigue, eye strain, or blurred vision at certain or all distances.
cataract: refers to a clouding or decreased transparency of the lens in the eye. Cataracts may be present at birth (congenital cataracts) or occur due to the normal aging process, disease, or environmental factors.
color blindness: an inability to distinguish between certain colors such as red and green (most common form - colors would appear as yellow). This condition is an inherited trait that occurs almost exclusively in males, but the recessive gene that causes the condition is carried by the female.
cone: nerve cells of the retina (along with rods) that transmit impulses along the optic nerve to the brain. Cones provide color vision and respond best to bright light.
conjunctivitis: commonly referred to as "pinkeye"; an infection of the mucosal membrane that both covers the eye and lines the eyelid and is caused by bacterium, viruses, or allergies. Symptoms include redness, itching, and discharge. Treatment is often performed with antibiotics or cortisone. This infection was a major cause of blindness in infants prior to the use of silver nitrate eye drops for newborns.
cornea: transparent layers of cells and proteins that cover the front of the eye and serve to both control and focus light into the eye. Most common problems with visual acuity, including hyperopia (farsightedness), myopia (nearsightedness), and astigmatism, are due irregularities in the shape of the cornea.
corneal abrasion: a cut or scratch within the cornea. This may be caused by foreign objects such as dirt, sand, wood or metal shavings, dust, fingernails, etc. that come in contact with the surface of the eye. Firm rubbing of the eyes can also cause an abrasion.
corneal ulcer: an erosion or open sore in the outer layers of the cornea caused by infection, abrasion, foreign bodies, severe allergy, severe dryness of the eye, various types of inflammatory disorders, stress, and an impaired immune system. Symptoms include eye pain, redness, blurred vision, light sensitivity, increased tearing, or a white patch on the cornea.
diabetic retinopathy: leading cause of blindness among individuals of working age; caused by complications associated with diabetes in which blood vessels of the retina become damaged and leak causing retinal swelling and the formation of deposits (non-proliferative or background retinopathy). The condition becomes more serious when new, weaker vessels form on the surface of the retina that can bleed into the vitreous causing severe visual impairment (proliferative retinopathy).
diopter: unit of measurement that describes the refractive (light-bending) power of a lens and is used in prescriptions. A negative value indicates a correction for nearsightedness (myopia), while a positive value indicates a correction for farsightedness (hyperopia).
floaters: small clumps of cells or gel in the vitreous that appear as specks or clouds moving within the field of vision. These clumps or strands are caused by a thickening or shrinking of the vitreous gel within the eye which then pulls away from the back surface of the eye (posterior vitreous detachment).
