Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Astigmatism


Related Terms

  • Irregular Astigmatism
  • Refraction Error

Differential Diagnosis

Comorbid Conditions

  • Endocrine disorders

Factors Influencing Duration

Some severe forms of astigmatism may not be fully treatable. Disability (depending on the extent of visual acuity needed for tasks) may be indefinite.

Medical Codes

ICD-9-CM:
367.20 - Astigmatism, Unspecified

Overview

Astigmatism is a common visual defect resulting from distortions in the curved shape of the front surface of the eye (cornea) and/or on the eye's natural lens (crystalline lens). Deviations in eye contour alter the path of light rays, which fail to focus at the appropriate spot on the back of the internal eye (retina), where the image is processed and sent to the brain. This results in blurred or ghost-like vision.

Distortions in the cornea where light rays enter the eye may be flat or steep, creating corneal astigmatism. Distortions in the eye's natural lens behind the cornea, where light rays focus onto the retina, cause lenticular astigmatism. Severe astigmatism may result from some type of eye surgery such as corneal transplants, cataract surgery, refractive vision correction, or repair of a corneal laceration.

Astigmatism tends to occur in individuals who either have undergone eye surgery or have other existing visual defects, including nearsightedness (myopia) or farsightedness (hyperopia). It may also develop in one (unilateral) or both eyes (bilateral). Almost all individuals have some astigmatism, but most cases are not severe enough to require corrective lenses or surgery. When correction is required, astigmatism can sometimes be very difficult to address with contact lenses, spectacles, or surgery because of the complex nature of the visual defects the condition creates.

Incidence and Prevalence: As many as 95% of individuals have some astigmatism, which is measured in units of refractive power needed to provide correction (diopters). About 15% of adults have astigmatism greater than 1 diopter; an additional 2% have more severe astigmatism greater than 3 diopters.

Source: Medical Disability Advisor



Diagnosis

History: The individual may report blurry or distorted vision, along with an inconsistent ability to focus on objects either near or far.

Physical exam: The individual may or may not squint when trying to see objects.

Tests: A visual acuity test and a standard ophthalmic examination with refraction test may be done. The individual may be examined with an instrument that measures refracted light from the cornea surface to detect contours (keratometer). Other instruments for measuring corneal surface curvature may be used (keratoscope, videokeratoscope).

Source: Medical Disability Advisor



Treatment

Astigmatism may be corrected with eyeglasses, contact lenses, or surgery. Contact lenses can correct both corneal and lenticular types of astigmatism. Hard contact lenses that temporarily reshape the eye (orthokeratology) may be recommended for wearing several hours daily. Spectacle and contact lenses have varying shapes curving inward (concave) or outward (convex) or both to offset distortions in the eye.

Astigmatic (or incisional) keratotomy surgery was commonly used for individuals with severe astigmatism or those who cannot tolerate glasses or contact lenses. Astigmatic or radial keratotomy (RK) involves making small incisions across the axis of greatest corneal curve to flatten its shape. It has been associated with complications such as farsightedness (hyperopia) that progressively worsens.

Newer surgical options have almost replaced astigmatic keratotomy. A preferred surgical treatment now involves cutting a thin, hinged flap in the cornea, lifting the flap, and reshaping the cornea underneath with a laser (laser-assisted in-situ keratomileusis or LASIK). The flap is replaced for protection and faster healing of the eye. A second option is photorefractive keratectomy (PRK), a similar procedure in which a flap is not created. In PRK, the cornea's outer layer is scraped away or removed with alcohol in preparation for laser reshaping of the eye.

Surgical procedures for astigmatism are often combined with corrections for nearsightedness (myopia) or farsightedness (hyperopia). Astigmatism correction may be further enhanced by newly developing technology that precisely measures irregularities within the entire vision system (wavefront).

Source: Medical Disability Advisor



Prognosis

In less severe cases, astigmatism is corrected fully. Astigmatism caused by scarring and some disorders affecting the cornea may not improve with eyeglasses but will correct with rigid contact lenses or surgery. Astigmatic keratotomy or incisional keratotomy can have a variable outcome.

Newer surgical techniques such as LASIK often significantly reduce the degree of astigmatism with stable results. Individuals undergoing LASIK or PRK often have significant improvement with very little discomfort. Some may experience only a foreign body sensation or dryness in the eye, whereas others may suffer from visual defects such as glare, halos, starbursts, and diminished night vision or from unusually dry eyes. Complications such as corneal scarring are unusual with newer surgical techniques but can lead to even worse visual defects.

Source: Medical Disability Advisor



Complications

Complications such as corneal scarring are unusual with newer surgical techniques but can lead to even worse visual defects. More than one angle of light may need adjustment in the same eye, which may make it more difficult or impossible to correct vision completely. Contact lens wearers may develop corneal abrasions.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

If keen visual acuity is an important aspect of the job, the individual's vision needs to be tested periodically. Even if individuals undergo vision correction surgery because keen vision is required for duties, eyeglasses or contact lenses may still be needed. Similarly, when eye protection is required while on the job, some individuals may need prescription safety glasses or goggles for astigmatism correction. Contact lens wearers may be more sensitive to dust and fumes. If astigmatic keratotomy is performed, vigorous exercise should be restricted for 30 days, and the individual must protect the eye(s) for 3 months. Individuals undergoing LASIK generally need only 1 day off for the day of surgery. Vision may fluctuate for about a week, and individuals whose tasks require keen eyesight may need to be temporarily assigned to other duties.

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Did individual report distortion of both near and far vision or other visual disturbances?
  • Was a visual acuity test done? Was an examination for refractory errors performed?
  • Did individual undergo vision correction surgery for another condition with complications that might have caused astigmatism?
  • Was diagnosis of astigmatism confirmed?

Regarding treatment:

  • Were eyeglasses or contact lenses effective in correcting the astigmatism?
  • If correction was not satisfactorily achieved with contact lenses or glasses, is individual a candidate for laser vision correction?

Regarding prognosis:

  • Are there occupational or other circumstances that prevent individual from wearing contact lenses or prescription glasses? If so, have alternative treatments such as LASIK been considered?
  • Following LASIK or PRK, was the correction less than optimal? Is the condition further correctable with addition of contact lenses or glasses?
  • Was wavefront-guided technology used in laser vision correction?
  • Does individual have a severe or uncorrectable astigmatism? Does individual have conditions such as advanced age or poor wound healing that would affect the recovery and outcome from laser vision surgery?
  • Did any complications associated with laser vision correction, such as corneal scarring, occur that may affect recovery?
  • How much do complications affect individual's ability to function in his or her present occupation?
  • Have accommodations been made to allow individual to return to work safely?

Source: Medical Disability Advisor



References

General

Hardten, David R., Ahmad M. Fahmy, and Scott G. Hauswirth. "Astigmatism, LASIK." eMedicine. Eds. Daniel S. Durrie, et al. 29 Dec. 2004. Medscape. 19 May 2005 <emedicine.com/oph/topic655.htm>.

Mayo Clinic Staff. "Astigmatism." MayoClinic.com. 19 Jan. 2005. Mayo Foundation for Medical Education and Research. 19 May 2005 <http://www.mayoclinic.com/invoke.cfm?id=DS00230&dsection=4>.

Source: Medical Disability Advisor






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