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.

Keratoconus

keratoconus in 中文(中华人民共和国)

Related Terms

  • Corneal Ectasia
  • KC

Differential Diagnosis

  • Astigmatism
  • Corneal dystrophy
  • Corneal erosion
  • Hyperopia
  • Myopia
  • Presbyopia

Specialists

  • Ophthalmologist

Comorbid Conditions

  • Immune system disorders

Factors Influencing Duration

Length of disability will be affected by severity of symptoms, effectiveness of treatment, individual response to treatment, recurrence of the condition, and recovery time needed.

Medical Codes

ICD-9-CM:
371.60 - Keratoconus, Unspecified
371.61 - Keratoconus, Stable Condition
371.62 - Keratoconus, Acute Hydrops

Overview

Keratoconus is a condition in which the cornea thins and becomes cone-shaped, distorting the shape of the eye as well as interfering with vision. The cornea is the anterior one-third supportive layer of the eyeball that focuses light rays into a sharp image. In a normal, healthy eye, the cornea is round and dome-shaped. When the cornea thins and distorts into a cone shape, the inability to focus light discretely on the center of the macula (fovea centralis) results in significant vision loss.

Increasing evidence may link keratoconus to hereditary factors, although definite causes of the condition remain unclear. Contact lens wear, eye rubbing and eye allergies may be associated with injury to eye tissue and resulting degeneration that may contribute to the condition.

Keratoconus is characterized by progressive thinning and distortion of the cornea occurring over 5 to 10 years, at which point the progression stops.

Incidence and Prevalence: Keratoconus affects approximately 1 in every 2,000 individuals in the general population (Lembach).

Source: Medical Disability Advisor



Causation and Known Risk Factors

Most cases of keratoconus are diagnosed at puberty, although the disease can develop when an individual reaches the 30's or 40's (Lembach). The condition occurs more often in women than men. Keratoconus is associated with diseases such as Down syndrome and genetic disorders affecting connective tissue (Ehlers-Danlos syndrome, Marfan's syndrome). Individuals who wear contact lenses or who have eye allergies may be more prone to develop the condition.

Source: Medical Disability Advisor



Diagnosis

History: The individual will complain of blurred and / or distorted vision. Vision changes generally are gradual, although some individuals may report a sudden change. Those who report a sudden clouding of vision may have advanced disease and a complication causing light sensitivity, pain, and tearing (acute hydrops).

Physical exam: The cornea will appear thin, and its shape will be distorted. Scars may be present at the tip of the bulging cornea.

Tests: A test to measure the individual's ability to see clearly is conducted. Corneal topography produces an image of the surface characteristics of the eye, which can help confirm the diagnosis and aid in assessing the severity and progression of the disease.

Source: Medical Disability Advisor



Treatment

In the early stages of keratoconus, ordinary eyeglasses generally will be used to correct vision. As the disease progresses, hard (gas permeable) contact lenses are needed to adequately correct vision. Because keratoconus tends to progress gradually over a period of several years, frequent, regular visits to the eye doctor are necessary to ensure that the glasses or contact lenses are the appropriate prescription.

Different treatment options for keratoconus that reaches advanced stages have become available in recent years. The most common involves removing the distorted cornea and replacing it with a healthy cornea from a donor (corneal transplant or penetrating keratoplasty). The Eye Bank Association of America reports that keratoconus is the third most common reason for corneal transplant (Lembach). A technique using plastic ring implants (Intrastromal Corneal Ring Segments or Intacs) to reshape the cornea has shown promise as a new therapy for keratoconus.

Source: Medical Disability Advisor



Prognosis

Overall, the prognosis is very good. Use of eyeglasses or contact lenses is very effective in correcting the vision in most cases, although there may be an accompanying condition caused by the abnormal shape of the cornea (irregular astigmatism) that causes some visual distortions. In those cases where corneal transplant is indicated, the procedure is usually successful. Recurrence of keratoconus in the transplanted cornea can occur, but is very rare. It may take up to a year for vision to be restored following a corneal transplant (Brown). Blindness is a remote possibility.

Source: Medical Disability Advisor



Complications

Because the cornea is thin and distorted, the individual is more prone to eye injuries (scratches, abrasions) and eye infections. Distorted vision caused by an abnormally shaped cornea (irregular astigmatism) may develop. In advanced cases, a condition in which the fluid that normally fills the front part of the eye (aqueous humor) accumulates in the cornea (acute corneal hydrops) may occur, making vision difficult or impossible. Very rarely, permanent vision loss can occur.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

Because individuals with keratoconus are more prone to eye infections or injuries, protective eye wear may be indicated. In cases where glasses or contact lenses can't correct vision completely, those whose jobs require keen vision may need to be reassigned. If surgery is required, extended sick time may be needed. For several weeks after surgery, flexibility to return for frequent eye exams may be necessary.

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:

  • Does individual complain of blurred and / or distorted vision?
  • Were changes gradual or sudden?
  • On physical exam, did the cornea appear thin, and its shape distorted?
  • Were scars present at the tip of the bulging cornea?
  • Did the individual have a visual acuity test?
  • Was a corneal topography done?
  • Have conditions with similar symptoms been ruled out?

Regarding treatment:

  • Do ordinary eyeglasses correct the individual's vision?
  • Has it become necessary to use gas permeable contact lenses to correct vision?
  • Does the individual require a corneal transplant?
  • Is the individual a candidate for corneal ring implants (if the procedure is available)?

Regarding prognosis:

  • Is individual's employer able to accommodate any necessary restrictions?
  • Does individual have any conditions that may affect the ability to recover?
  • Has individual had more eye injuries or infections?
  • Does individual have acute corneal hydrops?
  • Does individual have permanent loss of vision?

Source: Medical Disability Advisor



References

Cited

Brown, Donald J. "Searching for the Clue to Keratoconus." National Keratoconus Foundation. 2 Jul. 2004. 29 Dec. 2004 <http://www.nkcf.org>.

Lembach, Richard G. "Use of Contact Lenses for Management of Keratoconus." Ophthalmology Clinics of North America 16 3 (2003): 383-394. MD Consult. Elsevier, Inc. 29 Dec. 2004 <http://home.mdconsult.com/das/journal/view/38740730-2/N/14071835?sid=280607402&source=MI>.

Source: Medical Disability Advisor






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