ASTIGMATISM    

85-90% of all eyeglass prescriptions contain some correction for astigmatism. The eye, like a camera, has an outer curved lens, the cornea, to focus light. Most commonly, astigmatism occurs when this front surface has more than one curvature, rather than a perfectly round shape. With astigmatism, the shape of the cornea is asymmetrical, or somewhat "egg" shaped, rather than uniformly round like a ball. As a result, an astigmatic eye requires a special two-power lens to precisely focus light.  

Since astigmatism causes two different focuses per eye, and especially if astigmatism exists in both eyes, the brain has much to contend with. As a result, uncorrected or incorrect prescriptions for astigmatism cause blurred and distorted vision, as well as, annoying symptoms of eyestrain such as headaches, eye fatigue, sensitivity to light, loss of visual achievement and poor visual concentration.

It is expected that first correction or large changes in correction of astigmatism may cause objects or straight lines to appear tilted or distorted. This perception of distortion will decrease steadily with time. As with most prescriptions, it is common for the degree of astigmatism to change naturally over time. Eyeglasses, and/or, special astigmatic (toric) contact lenses are available to correct astigmatism.

HYPEROPIA or FARSIGHTEDNESS     

The medical term for farsightedness is hyperopia. As with most refractive errors, farsightedness is commonly caused by the shape of the eye. Farsighted eyes are generally shorter from front to back or because the front curvature of the eye is flatter than normal. An uncorrected farsighted eye must use the near focusing system of the eye, normally only used for close-range tasks, to assist distance vision. As a result, this places an even greater focusing effort on close-range vision. Uncomfortable symptoms and fatigue are common for the uncorrected or under-corrected farsighted eye since the visual system is in a constant state of over effort.

Clarity and comfort of vision for the farsighted person depends on their degree of farsightedness and the efficiency of their focusing system. In general, farsighted eyes always see better at far distance than at closer distances. Farsighted adults gradually see less clearly at all distances due to a natural and expected decline in the eyes close-range focusing ability over time.

Farsightedness is most commonly corrected with eyeglasses or contact lenses. If adults require different prescriptions for distance and near, special dual-focus contact lenses are now available. Less commonly, refractive surgery techniques such as LASIK, or lens replacements are also treatment options for adults.

MYOPIA or Nearsightedness     

The medical term for nearsightedness is myopia. When you are nearsighted, your distance vision is blurred. Close range vision is generally clear at some near distance without correction, thus the term "nearsighted." As with most refractive errors, nearsightedness is simply caused by the shape of the eye. In this case, the eye is longer front to back, or has a steeper curve to the front lens of the eye, the cornea. Genetic, environmental or functional factors can also play a role in the development of nearsightedness.

Nearsightedness is generally corrected with eyeglasses or contact lenses. For adults, refractive surgery such as LASIK, or lens replacements are additional options.

PRESBYOPIA (prez-bee-O-pee-ah)     

Presbyopia is a normal decline in close-range focusing ability of our eyes with time. Presbyopia seems to present close-range issues suddenly but actually it does not. Our eyes have maximum focusing ability in our teens, about 50% at age 40, and we gradually decline to a fixed non-variable focus around the age of 70. The average person requires a different prescription for distance vs. reading tasks around the age of 42.  

Most people falsely think that muscles inside the eye weaken over time causing this gradual loss of close-range focus. To the contrary, presbyopia is a loss of elasticity of the focusing lens inside the eye. In addition, many falsely believe that if eyeglasses are worn often it will weaken the eyes' further. It is important to understand that wearing appropriate eyeglasses or multi-focus contact lenses full-time or part-time will not weaken or change your future visual status in any way. All humans experience this unavoidable and fully correctable visual condition.

Serving clients in Northwest Metro Minnesota including the communities of Albertville • St. Michael • Otsego • Hannover • Wright County

Albertville Eye Care, 2011