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ELAINE HOLYOAK KITCHEL, Research Scientist
1990

Abstract

Choices of UV filters and NoIR filters from 60 low-vision subjects were obtained from clients receiving services within Indiana Blind and Visually Impaired Section, Indiana Vocational Rehabilitation Services, Bosma Industries for the Blind and persons at large. Another group of 20 subjects was selected among non-visually impaired employees who worked for those institutions to provide a comparison. Subjects were asked to select for eye comfort, and contrast from among the following filters provided by NoIR Medical technologies: U50 (yellow), U81 (medium plum), U80 (dark plum), U21 (medium grey), U70 (pink), 102 (medium grey green), U10 (clear), U93 (red), U60 (orange), U22 (dark grey), 101 (amber), 708 (dark grey green). Twenty-eight percent of the experimental group chose medium plum filters, 25% chose yellow, with pink being chosen at a rate of 13%. Clients had been asked to select filters in standard indoor light and medium-to-bright outdoor light and judge filters according to the following criteria:

  1. Best contrast achieved and;
  2. Eye comfort

Determinations were then made about which persons most often chose which filters based on statistical frequency. Subjects performed a daily task while wearing the filters in order to determine if the filters actually helped improve contrast or eye comfort. It was found that the subjects who suffered from macular degeneration, glaucoma, retinitis pigmentosa most often chose yellow filters. Persons with histoplasmosis, toxoplasmosis and the category of "other" which consisted mostly of refractive errors and retinopathy most often chose plum, with plum being the most chosen color overall. Filters of red, green, orange and clear all were chosen by at least one subject. Grey was preferred by the control group overwhelmingly. Dark grey, amber, and dark grey green were not selected by any subjects with visual impairments.

Introduction

For many years now experts in low vision have been aware that persons with low-vision often suffer super-sensitivity to light and glare. In 1985, Joseph H. Maino, O.D., and Timothy T. McMahon, O.D., did a study determining their patient's preferences for the NoIR series of light filters. NoIRs are filters which incorporate infrared and ultraviolet absorbers, as well as blue light absorbers in some models. They then determined patient preferences for filters based upon ocular disease and visual acuity.

Drs. Maino and McMahon determined that more than 50% of the patients chose the #101, or medium amber filter. These were mostly patients with dry macular degeneration, glaucoma, and retinitis pigmentosa. About a third of their subjects chose the #102 or grey green in medium tone. This color was preferred by subjects with eye diseases other than those named above. But it should be noted that the Maino-McMahon study included five colors of NoIRs only and did not include the broad color range and the greater light transmissions of the newer NoIR and UV filters available today. This researcher could find no literature which sought to determine the types of UV shields preferred by low-vision persons, especially in colors other than grey-green and amber.

Greater range of color is an important distinction because colored filters have improved greatly since the 1985 study. Traditionally the older NoIRs were very dark and did not allow for much of a color range. In fact, the Main-McMahon study used only five shades, medium amber, medium grey-green, dark amber, dark grey-green, and very dark green. But filters produced now by NoIR Medical Technologies have a wide range of color, shade, and light transmission.

This study uses a wide range of color and light transmission using the new filters produced by NoIR Medical Technologies. This provides for consistent color, shade and light transmission throughout the study:

  • Model U50 medium yellow, transmits 54% of available light.
  • Model U81 medium plum, transmits 20% of available light.
  • Model U80 dark plum, transmits 4% of available light.
  • Model U21 medium gray, transmits 32% of available light.
  • Model U70 light pink, transmits 44% of available light.
  • Model 102 medium gray-green, transmits 18% of available light.
  • Model U10 clear, transmits 90% of available light.
  • Model U93 dark red, transmits 4% of available light.
  • Model U60 medium orange, transmits 49% of available light.
  • Model U22 dark gray, transmits 13% of available light.
  • Model 101 medium amber, transmits 10% of available light.
  • Model 708 dark gray-green, transmits 1% of available light.

All these filters were used in the study.

Methods

The study was conducted on 60 low-vision subjects within the State of Indiana.

These subjects were recruited from among people being served through Vocational Rehabilitation Services, Services for the Blind and Visually Impaired Section and Bosma Industries for the Blind. Another group of 20 persons was recruited from among persons who were not visually impaired who were working or serving in those same agencies to see if their selections were different from those of persons with low vision. Each visually impaired person had been certified as visually impaired by a qualified physician.

The subjects were asked to try on each of the 12 pair of filters mentioned in the introduction in typical indoor light, and medium-to-bright outdoor light and to select a single pair of filters based upon:

  1. Best overall contrast achieved and;
  2. Overall eye comfort.

Each subject was then asked to wear the filters to perform one of his usual tasks and to report whether or not the filters actually provided better contrast or eye comfort. All but one of the subjects reported that the chosen filter actually helped either to achieve better contrast, or helped achieve more eye comfort. Information was obtained on the filter chosen, and primary ocular disease.

Results

Sixty visually impaired subjects presented with 13 different eye diseases or conditions, visual acuity ranged from 20/70 to less than 20/800. Individual conditions which constituted less than 2% of the cases were placed in the "other" category. Persons with Stargaardt's disease were placed in macular degeneration category, Usher's syndrome placed in retinitis pigmentosa category.

TABLE 1: Ocular Disease Represented in the study
Disease/Conditon# of Subjects% of Total

Macular Degeneration

16

27% (includes Stargaard's)

Diabetic Retinopathy

6

10%

Glaucoma

6

10%

Retinitis Pigmentosa

6

10% (includes Usher's)

Histo-Toxoplasmosis

6

10%

Uveitis

4

6%

Other

13

21%

Subjects preferences for the filters in descending order were:

  1. Medium Plum 28%
  2. Yellow 25%
  3. Pink 13%
  4. Medium Grey-Green 10%
  5. Orange 10%
  6. Medium Grey 7%
  7. Red 3%
  8. Clear 2%
  9. Dark Plum 2%
  10. Dark Grey 0%
  11. Amber 0%
  12. Dark Grey-Green 0%

Typical Vision Group Preferences for the Filters in descending order were:

  • Medium Grey 85%
  • Orange 5%
  • Pink 5%
  • Medium Plum 5%

Persons with macular degeneration generally preferred yellow, but plum ran a close second place in this group at a ratio of 5:3. Persons with diabetic retinopathy preferred plum at a ratio of 3:1. Persons with glaucoma preferred yellow at a ratio of 3:1. Persons with retinitis pigmentosa preferred yellow over other colors at a ratio of 2:1. Persons with histoplasmosis and toxoplasmosis preferred plum over other colors at a ratio of 4:1 and persons with uveitis preferred grey over other colors at a ratio of 2:1. Persons in the category of "other" preferred plum at a ratio of almost 6:1. And the typical vision group preferred grey over other colors at a ratio of 17:1.

Discussion

It is interesting to make a few comparisons of the different disease groups within the study and their choices of filters. In general, the groups in which visual field was a main complaint, i.e., macular degeneration, glaucoma and retinitis pigmentosa, tended to choose the filter which let in the greatest amount of light while still affording good elimination of blue and ultraviolet light. This was demonstrated by their preference for the yellow filter with 54% light transmission.

This information tends to support the results of Maino and McMahon who discovered that their patients with dry macular degeneration, open-angle glaucoma, and retinitis pigmentosa preferred filters #101 (light amber) by 2:1 in the cases of macular degeneration and glaucoma, and 17:1 in the cases of the retinitis pigmentosa patients. One could argue this is because the filter #101 in that study was the one which let in the greatest amount of light.

In our study the model U50 or yellow filter lets in light of the same part of the spectrum as the #101 amber filters, but lets in 54% of total available light as compared to 10% in the #101. This underscores the need for maximum light for people with macular degeneration, glaucoma, and retinitis pigmentosa while shielding them from the irritating ultraviolet and blue end of the visible light spectrum.

Persons with Diabetic retinopathy, histo-and toxoplasmosis in which the field is not necessarily small or peripheral, but rather scattered with scotomas preferred less light as afforded by their choice of the medium plum filter, 20% TLT (total light transmission) while still allowing good ultraviolet and blue light protection. Many cited "eye comfort" as their primary consideration.

Persons in the "other" group which consisted of those with refractive errors, cataracts, malformations, and brain injuries preferred the plum also, but there again, narrow or peripheral field is not usually a consideration.

The typical vision group overwhelmingly preferred medium grey, demonstrating that since improving their vision is not a consideration, they prefer to stay with a color they are comfortable with and have traditionally used in the past. Many of the typical vision group stated that they were resistant to change.

It is also notable that no one chose the filters with less than 18% light transmission in the grey, amber or grey-green colors. One person did select the 4% dark plum. But overwhelmingly all groups chose filters with at least 20% TLT.

These choices eliminated virtually all of the NoIR choices, in favor of the UV filters with more light transmission. Yet, oddly, many optometrists and opthalmologists still favor dark green, gray-green and dark amber when they prescribe or dispense a filter.

Conclusion

Given a choice, persons with low vision in this study will choose filters to promote maximum contrast and eye comfort. Persons with macular degeneration glaucoma, and retinitis pigmentosa demonstrated a need for more light than other persons with other diseases, as demonstrated by their choices of the yellow U50 in 60-75% of those cases. Persons with diabetic retinopathy, histo and toxoplasmosis and other eye diseases, prefer plum filters in a clear majority of the cases, 80-91%. The IR only filters were not preferred by any group. A few subjects did choose the medium grey-green NoIR, but not with enough frequency to be statistically important. We can conclude that people, both Visually Impaired and those with good vision, seem to prefer filters which eliminate ultraviolet over those which eliminate only infra-red. Of the UV filters tested, Plum U81, was the one most preferred, with yellow U50 running a close second. U21, medium grey was preferred by the typical vision group. Thus we may conclude that the choices of filters made by persons with low vision, do differ from those made by persons with typical vision. These choices are greatly impacted by the eye pathology of the person doing the selecting. This information implies that the color and wavelength of light entering and light reflected in the environment of the person with visual impairment affects his/her eye comfort and ability to detect visual contrasts. These results could be helpful to those designing environments for persons with low vision, and those recommending solutions to lighting problems.

TABLE 2: OCULAR DISEASES REPRESENTING 2% OR LESS OF TOTAL CASES STUDIED
Photophobia of unknown etiology 1
Severe Myopia 2
Retinal Detachment 2
Retinopathy of Prematurity 2
Papilledema 1
Brain Injury 2
Congenital Malformation 1
Cataract 2
TABLE 3: COLOR CHOICES IN DESCENDING ORDER USING TOTAL SAMPLE
FREQUENCYCOLOR CHOSENFILTER #TOTAL LIGHT TRANSMISSION
28% Medium Plum U81 20% TLT
25% Yellow U50 54% TLT
13% Pink U70 44% TLT
10% Orange U60 49% TLT
10% Med Grey Green 102 18% TLT
7% Medium Grey U21 32% TLT
3% Red U93 4% TLT
2% Dark Plum U80 4% TLT
2% Clear U10 90% TLT
0% Amber 101 10% TLT
0% Dark Grey U22 13% TLT
0% Dark Grey Green 708 1% TLT

Resources

  1. Legge, G.E. & Rubin, G.S. (1986). Psychophysics of reading. IV. Wavelength effects in normal and low vision. Journal of the Optical Society of America, A3, 40-51.
  2. Maino, Joseph H. and Timothy T. McMahon, O.D., "NoIRs and Low Vision," JOURNAL OF AMERICAN OPTOMETRIC ASSOCIATION, Vol.57, Num.7, July, 1986.
  3. "Light Transmission Curves of the UV Shield," NoIR Medical Technologies, South Lyon, MI.
  4. "Light Transmission Curves of the NoIR," NoIr Medical Technologies, South Lyon, MI.