Appendix 1
1. Appendix I: Visual Standards
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Standards for evaluating visual impairment have been provided for many years by the (AMA) in its Guides to the Evaluation of Permanent Impairment, also reproduced in the Physicians' Desk Reference for Ophthalmology. Standards are also set forth in the International Classification of Diseases, in sections relating to blindness and low vision.
ASSESSMENT OF VISUAL IMPAIRMENT
Three equally important criteria are used to assess visual impairment: visual acuity, visual field, and ocular motility. The percentage impairments of the three criteria are summed to produce an overall assessment of impairment of the visual system. This can then be converted to a percentage of whole-person impairment, to which 10% impairment can be added for cosmetic deformities of the eyes or orbits.
Visual Acuity
In line with improvements in test optotype design, the most acceptable charts for testing visual acuity for distance, such as the ETDRS chart (
Figure 22-1), utilize the ten equally difficult block letters (D, K, R, H, V, C, N, Z, S, and O) developed by Louise L. Sloan. Also acceptable are Snellen test charts with block (sans serif) letters or numbers, illiterate E charts, or Landolt ring charts. Acceptable near vision charts have print similar to the Sloan optotypes, Revised Jaeger Standard print, or American point-type notation. Test distance is 35 cm (14 inches). Both distance and near acuity should be tested with best spectacle correction, or with contact lenses if the subject wishes.
The AMA Standards assign to acuities a percentage loss (Table 1). The percentage losses for distance and near vision are averaged to determine the overall loss of visual acuity. Allowance is also made for monocular pseudophakia or aphakia.
Visual Field
The traditional standard method of assessing visual field impairment uses kinetic perimetry, with the III4e stimulus of the Goldmann perimeter, to determine the full extent of the visual field of each eye. For each of eight principal meridians, the amount in degrees by which the visual field is reduced compared with a standard normal field is then calculated and an overall percentage loss is derived for each eye. The cumulative total of the maximum allowed extent of the standard normal visual field along the eight principal meridians is 500 degrees (Figure 1). Thus, the percentage visual field loss equals the total difference between the test and normal fields divided by 5. If the boundary of the visual field coincides with a principal meridian, the mean of the values of the ends of the boundary along the meridian is used. Furthermore, the extent of any scotoma lying across a meridian is deducted. Owing to the greater functional importance of inferior compared with superior field loss, the percentage field loss is further increased by 5% for inferior quadrantanopic and 10% for inferior hemianopic loss.
Ocular Motility
The extent of diplopia on ocular excursion up to 40 degrees-or, conversely, the field of binocular single vision within this area-is usually determined with a bowl (eg, Goldmann) or arc perimeter, using a III4e or equivalent target and with the subject viewing binocularly. A tangent screen can also be used. The presence or absence of diplopia at 10-degree intervals along the eight principal meridians is then determined and the meridian of maximum impairment is identified. Diplopia on excursion of less than 20 degrees is considered 100% impairment. Diplopia between 20 and 30 degrees looking upward-or upward and to either side-is 10% impairment; between 20 and 40 degrees looking laterally-or down and to either side-corresponds to 20% (20-30 degrees) or 10% (30-40 degrees) impairment. Diplopia on looking downward is functionally most disabling and thus corresponds to 50% impairment if between 20 and 30 degrees or 30% if between 30 and 40 degrees of ocular excursion.
ICD-9-DM STANDARDS
The International Classification of Diseases defines visual impairment as distinct from visual disability and visual handicap. Visual impairment is a functional limitation of the eye. Disability is the resulting limitation of the individual's ability to read or do close detailed work. A visual handicap is the impact on personal or socioeconomic independence (restricted mobility, unsuitable employment) and has been classified into various levels by the World Health Organization (
Table 23-1), though definitions of blindness do still vary between countries.
VISUAL STANDARDS FOR DRIVERS' LICENCES, AIRCRAFT PILOTS, & THE ARMED SERVICES ACADEMIES
Visual standards for persons applying for drivers' licences vary between states, and some allow driving using telescopic low-vision aids. The visual standards for commercial drivers, for aircraft pilots, and for admission to service academies are listed in the Physicians' Desk Reference for Ophthalmology.
EDUCATION OF VISUALLY IMPAIRED CHILDREN
The education of visually impaired children has changed since passage of the Individuals with Disabilities Education Act of 1990 (IDEA-P.L. 101-476, amended by the individuals with disabilities education act (IDEA) Amendments of 1991, P.L. 102-119), which reads in part: "Each State and its public agencies must ensure that all children with specified disabilities have available to them a free appropriate public education." Because of the scattered nature of the provisions throughout the document for visually impaired children, the American Foundation for the Blind in 1993 prepared a summary of the pertinent sections. For example, subchapter II (Part B) covers special class settings and subchapter III (Part C) covers centers and services to meet unique needs.
Each child's needs must be evaluated before placement so that decisions can be made about whether to provide print or braille education, orientation and mobility, social interaction skills, career education, etc.
Placement options to be considered by a group "knowledgeable about the child" can be (1) in a regular classroom with needed support services by a special teacher in or outside of the classroom, (2) in a self-contained classroom in a regular school, or (3) in a special school with residential option.
Part B provides that a due process hearing may be initiated by the parents "when an agreement cannot be reached on important educational decisions."
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10.1036/1535-8860.appendix1