• Light is bent or refracted as it passes through the cornea and lens of the eye
• Refractive errors exist when light rays are not focused appropriately on the retina of the eye
A. MYOPIA
B. HYPEROPIA
C. ASTIGMATISM
• Optical correction is important to distinguish between visual loss caused by disease and visual loss caused by refractive error
• Refractometry is the measurement of refractive error
• Refraction is the method used to determine which lens or lenses will most benefit the client
MYOPIA
• Nearsightedness
• A condition in which the light rays come into focus in front of the retina
• The refractive power of the eye is too strong
• A concave, or minus, lens is used to focus light rays on the eye
• In most cases, it is caused by an eyeball that is longer than normal, a familial trait
• Transient myopia may occur with administration of a variety of medications: sulfonamides, acetazolamide, salicylates, and steroids
• Maybe associated with certain diseases: influenza, typhoid fever, severe dehydration, stomach ulcers after intake of antacids
HYPEROPIA
• Farsighted
• Eye is deficient in its ability to focus light rays
• The focal point falls behind the eye, subsequently, the image falls on the retina is blurred
• Vision maybe brought into focus by placing a convex, or plus, lens in front of the eye
• The lens supplies the magnifying power that the eye is lacking
• May be caused by an eyeball that is shorter than normal, or a cornea that has less curvature than normal
• Because children have greater ability to accommodate, they are less often affected than adults
• Demands for close work and reading usually bring on manifestations of headache or eyestrain
• Correction is based on a person’s age and individual needs and complaints
ASTIGMATISM
• A refractive condition in which rays of light are not bent equally b y the cornea in all directions, so that a point of focus is not attained
• In most instances, it is caused by the imperfect spherical form of the cornea
• This is the cause of poor vision for both distant and near objects
Surgical Management
• In 1990s, several techniques and methods of surgical correction for myopia and hyperopia
• Short-wavelength, high-energy ultraviolet radiation lasers are being to reshape the corneal surface
• In photorefractive keratectomy (PRK):
• For myopia, the central cornea is flattened with excimer laser
• For hyperopia, it is used to reshape the cornea by steepening the central curvature
• Laser in situ keratomileusis (LASIK)
• A procedure in which an extremely thin layer of the cornea is peeled back for the laser reshaping in the middle layer of the cornea and then put back in place
• Although a difficult procedure, there is less post-operative discomfort, a more rapid recovery of clear vision, and quicker stabilization of refractive change
Nursing Management of the Surgical Client
• Assess for the degree of myopia or astigmatism preoperatively
• Inform client that surgery is performed on an outpatient basis with local anesthesia
• Treatment with steroid eye drops
• Educate about a period of adjustment during which visual acuity waxes and wanes
• Inform that reduced contrast sensitivity in night vision and daytime glare is common
• Some clients require re-treatment for scarring that is unresponsive to topical steroids
