Printer Friendly

Contrast sensitivity function scores, choices of illuminated stand magnifiers, and reading.

Far too often, professionals focus almost solely on individuals' needs for magnification level for reading. Visual acuities are measured and decisions are made for low vision devices largely on the basis of acuity levels. Contrast sensitivity function is often overlooked as a critical need for and predictor of the selection and preference for low vision devices. This article discusses the correlation between contrast sensitivity function and illumination needs; measurements of the levels of the reflective illuminance of current illuminated stand magnifiers; and calls for further study of the relationship among contrast sensitivity function, illumination needs, and preferences for low vision devices for reading.

BACKGROUND

Christiansen and Gerritsen (2006, 2007) reported a strong correlation between a person's score on a test of contrast sensitivity function and his or her preferences for illumination with a low vision device for reading. For instance, persons with low scores, such as 25% or 10% on a test of contrast sensitivity function (such as the LEA test), manifested a strong preference for low vision devices with very bright illumination. These persons generally selected illuminated stand magnifiers with the brightest illumination and closed-circuit televisions (CCTVs) with the brightest screens. Persons with better scores (5% or 2.5% on a test of contrast sensitivity function) often did not need as high illumination with their low vision devices for reading. Persons with a high score (1.25%) on a such a test may select low vision devices with lower or no auxiliary illumination, such as microscopic reading glasses, loupes, or nonilluminated magnifiers.

In the past, the choices of illuminated magnifiers used to be simply halogen, LED, or incandescent. Now, persons with low vision may choose among at least three types of "halogen" handles (such as traditional halogen, xenon, and "kryptolux"). Also, there has been a proliferation of possibilities of LED handles. Previously, LED simply meant a "light-emitting diode," which is precisely what manufacturers of illuminated stand magnifiers used--a single diode. Then, some manufacturers began to use two or even three LEDs in a handle. Others began to use a chip, later followed by a multichip. Early multichips were generally 5 millimeters. In the past year, 8-millimeter multichips have been used, creating brightness in LED handles that outperforms even halogen handles. LED technology continues to evolve.

In Christiansen and Gerritsen's (2006, 2007) studies, no distinction was made among various types of LED handles, largely because the range of choices was much smaller than there is now. Most units usually had a single diode, with not as great a difference among various brands or options as there is now. There were various colors (blue, white, yellow, and plum) of LEDs for illuminated stand magnifiers, but not the vast difference in intensities of LED handles that there is today. Therefore, at that time, all LEDs were included together in the category of "midlevel brightness," despite slight differences in brightness. Also, no distinction was made among models that used halogen, xenon, and kryptolux bulbs.

Because of the correlation between poor scores for contrast sensitivity function and individuals' preferences for illuminated stand magnifiers or CCTVs with the brightest illumination, the quest of professionals is to help individuals find the devices with the highest illumination. This study sought to measure objectively the reflectance illumination of the most common illuminated stand magnifiers, information that can be used as a resource for practitioners and individuals. The study did not measure and compare the brightness of various CCTV monitors. However, such a study would be helpful and is encouraged.

PROCEDURE

Careful measurements of reflectance illumination were made of the most common illuminated stand magnifiers that are on the market. Reflectance illumination from an illuminated stand magnifier refers to the amount of light emanating from the top of the stand magnifier when it is pressed flat against the page and viewed at a given distance. These measurements, therefore, recorded the illumination (in foot-candles) "reflected" through the top of various illuminated stand magnifiers at given distances that persons with low vision typically use to read different types of text on different types of paper and with various degrees of contrast.

The major brands of illuminated stand magnifiers that I measured included Advantage, with 8-millimeter and 5-millimeter LED handles; Coil xenon plug-in and LED battery handles; Eschenbach halogen plug-in (with nonrheostat) and LED battery handles; a PowerMag+ SMD (surface-mounted diode) LED handle; and the Schweizer Kryptostar rechargeable. Strengths measured included the 2.8X or 3X; the 5X or 5.4X; and the 12X, 12.5X, or 13X models. These strengths represented the weaker, medium, and stronger lenses available in each brand.

Measurements were made of illuminated stand magnifiers with text on three types of paper, which represent various levels of contrast: 20-pound white copy paper, with an article from the Internet printed with black ink (high contrast), an article from the March-April 2009 issue of the AARP Magazine (medium contrast), and obituaries from a local newspaper (low contrast). Measurements were carefully taken at distances that are generally used or recommended for persons with low vision for the strength of a particular magnifier: 2.8X and 3X illuminated stand magnifiers (100 x 75 millimeter lens) at 2.5, 4, 10, and 12 inches; 5X or 5.4X illuminated stand magnifiers at 2.5, 4, and 10 inches; and 12X, 12.5X, or 13X illuminated stand magnifiers at 1, 1.5, and 2.5 inches.

Each measurement was taken by two people at once for greater accuracy. One person would carefully hold the head of the light meter at the precise distance from the text, ensuring that the meter was completely parallel to the surface of the text and not tilted. The other person would rest the rule in a steady position and read the meter.

Measurements were taken multiple times with every magnifier for each distance and for each type of text. The light meter was held in place above the text for about 30 seconds, to help provide an accurate reading.

All measurements were taken on the same paragraph and the same spot on the page for each type of paper or text that was measured and for each distance. Doing so helped ensure that there were no differences between measurements because of white spaces versus solid text.

Measurements were made in foot-candles, to a 10th of a foot-candle. They were generally recorded, however, in whole foot-candles. When there were only slight differences in recordings, they were made in 0.5 foot-candles or even in 10ths of a foot-candle. A high-quality Extech light meter--Model EA30, with precise accuracy--was used.

RESULTS

* The illuminated stand magnifiers with the highest reflective illuminance for all types of text and at all almost all distances were the Advantage brand with the 8-millimeter handle. See Table 1 for all the measurements and a comparison of the various magnifiers.

* Stand magnifiers that were also found to have high reflective illuminance included the Schweizer Kryptostar 3X rechargeable stand magnifier and the Eschenbach halogen 5X and 12.5X stand magnifiers with plug-in handles.

* Models with medium-level reflective illuminance included the Eschenbach stand magnifiers with the LED battery handle, the PowerMag + "HaloBright" with SMD LED handle, the Eschenbach 2.8X plug-in model, the Schweizer 5X Kryptostar rechargeable magnifier, the Coil 12X xenon plug-in stand magnifier, and the Advantage 12X stand magnifier with the 5-millimeter LED handle. * Models with low reflective illuminance included the Coil xenon plug-in 2.8X and 5.4X stand magnifiers. * The lowest reflective illuminance on all text and distances was with the Coil stand magnifiers with LED battery handles.

DISCUSSION

Choices are now greater than ever before for illuminated stand magnifiers because of new LED options and designs. Considering that persons with a low score on contrast sensitivity function generally need brighter illumination, it is important to have comparisons available to help identify which brands or models actually provide higher reflectance illumination, regardless of their marketing claims. An independent study and measurement seemed not only beneficial but needed.

Persons with a low score on contrast sensitivity (25% or 10%) may report difficulty reading text with an older type of LED stand magnifier that may have only a single diode or a 5-millimeter chip, yet may do well with a model with the newer, very bright 8-millimeter multichip or with multidiodes. They may also do well with a stand magnifier with a halogen or kryptolux bulb, which also provides high reflective illuminance.

A side note is the lesson that getting closer to the lens will dramatically increase the amount of illumination available to a person when reading, in addition to providing a larger field of view. This increased illumination may be vital to those with low scores on contrast sensitivity function.

This comparison of various illuminated stand magnifiers is a starting point for developing an awareness of differences in choices. It could also prompt another study of individuals' preferences in selecting reading devices with various levels of illumination compared to theft scores on contrast sensitivity function. As LED technology continues to change, further measurements of new illuminated stand magnifiers could be made to help determine the brightest solutions and appropriate illumination options for persons with poor contrast sensitivity function. Continued study is needed on the important correlation among contrast sensitivity function, illumination needs, and reading performance.

The main focus of this article has been to review the preference by many individuals with low scores on contrast sensitivity function for low vision devices with bright illumination, and to present a study of the measurements of the reflectance illumination of major illuminated stand magnifiers. It is important to note, however, that this preference for bright solutions for reading is not limited to illuminated stand magnifiers, but similarly usually includes a preference for the brightest CCTV monitors. The choice of a monitor for a CCTV may also be a critical factor for persons with poor contrast sensitivity function. Because this study did not measure the illuminance of various CCTV monitors, a separate study to do so may help persons with poor contrast sensitivity function to make informed decisions and to find the brightest solutions.

REFERENCES

Christiansen, R. M., & Gerritsen, B. R. (2006, November). Contrast sensitivity function testing and low device lighting preference for reading. Poster session presented at the meeting of the American Academy of Ophthalmology, Las Vegas, NV.

Christiansen, R. M., & Gerritsen, B. R. (2008, July). Contrast sensitivity function testing and low device lighting preference for reading: A follow-up study. Poster session presented at the Association for Education and Rehabilitation of the Blind and Visually Impaired International Conference in Chicago, IL.

Fletcher, D. C. (2006, March-April). Acuity does not equal vision. Retinal Physician, Supplement, 3-6.

Rosenthal, B. P. (2006, March). Visual acuity vs. contrast sensitivity--Which test provides the most valuable information on a patient's visual state? Optometric Management. Retrieved from http://www.optometric.com/ article.aspx?article=71599

Bryan Gerritsen, M.A., C.L.V.T., low vision therapist, Low Vision Rehabilitation Services, LC, 439 East 3100 North, North Ogden, UT 84414; e-mail: <bryangerritsen@comcast.net>.
Table I
Comparison of measurements of reflective illumination of most
common illuminated stand magnifiers (measurements are in foot-candles).

                                                       Copy paper with
                                                           article
                                                       (High contrast)

Brand and description of illuminated
stand magnifier                                        1    1.5   2.5

Low power (2.8X or 3X, 100 x 75 mm)
  Advantage 3x "large," with 8-mm LED battery handle   --   --    38
  Schweizer 3X Kryptostar, with plug-in rechargeable
    handle                                             --   --    42
  Eschenbach 2.8X, with halogen plug-in handle         --   --    32
  Eschenbach 2.8X, with LED battery handle             --   --    23
  PowerMag+ 3X "HaloBright," with SMD LED handle       --   --    32
  Coil 2.8X, with xenon plug-in handle                 --   --    21
  Coil 2.8x, w/ LED battery handle                     --   --    4.5
Medium power (5X or 5.4X)
  Advantage 5X, with 8-mm LED battery handle           --   --    58
  Eschenbach 5X, with halogen plug-in handle           --   --    48
  Eschenbach 5X, with LED battery handle               --   --    24
  Schweizer 5X Kryptostar, with plug-in rechargeable
    handle                                             --   --    35
  PowerMag+ 5X "HaloBright," with SMD LED handle       --   --    31
  Coil 5.4X, with xenon plug- in handle                --   --    18
  Coil 5.4X, with LED battery handle                   --   --    5
High power (12X, 12.5, or 13X)
  Advantage 12X, with 8-mm LED battery handle          95   56    29
  Advantage 12X, with 5-mm LED battery handle          34   22    13
  Eschenbach 12.5X, with halogen plug-in handle        72   42    21
  Eschenbach 12.5X, with LED battery handle            43   32    16
  PowerMag+ 13X "HaloBright," with SMD LED handle      40   28    14
  Coil 12X, with xenon plug-in handle                  44   26    14
  Coil 12X, with LED battery handle                    10   8     6

                                                       Copy paper with
                                                           article
                                                       (High contrast)
Brand and description of illuminated
stand magnifier                                         4     10    12

Low power (2.8X or 3X, 100 x 75 mm)
  Advantage 3x "large," with 8-mm LED battery handle   24     9     7
  Schweizer 3X Kryptostar, with plug-in rechargeable
    handle                                             22     7     6
  Eschenbach 2.8X, with halogen plug-in handle         16     6     5.5
  Eschenbach 2.8X, with LED battery handle             14     6     5
  PowerMag+ 3X "HaloBright," with SMD LED handle       18     6     4.5
  Coil 2.8X, with xenon plug-in handle                 11     4     3
  Coil 2.8x, w/ LED battery handle                     3.5    2.5   2
Medium power (5X or 5.4X)
  Advantage 5X, with 8-mm LED battery handle           31     9     --
  Eschenbach 5X, with halogen plug-in handle           23     6     --
  Eschenbach 5X, with LED battery handle               13     5     --
  Schweizer 5X Kryptostar, with plug-in rechargeable
    handle                                             18     6     --
  PowerMag+ 5X "HaloBright," with SMD LED handle       16.5   5.5   --
  Coil 5.4X, with xenon plug- in handle                10     4.3   --
  Coil 5.4X, with LED battery handle                   4      2.6   --
High power (12X, 12.5, or 13X)
  Advantage 12X, with 8-mm LED battery handle          --     --    --
  Advantage 12X, with 5-mm LED battery handle          --     --    --
  Eschenbach 12.5X, with halogen plug-in handle        --     --    --
  Eschenbach 12.5X, with LED battery handle            --     --    --
  PowerMag+ 13X "HaloBright," with SMD LED handle      --     --    --
  Coil 12X, with xenon plug-in handle                  --     --    --
  Coil 12X, with LED battery handle                    --     --    --

                                                         AARP Magazine
                                                           article
                                                           (Medium
                                                           contrast)
                                                           Distance
                                                           (inches)
Brand and description of illuminated
stand magnifier                                        1    1.5   2.5

Low power (2.8X or 3X, 100 x 75 mm)
  Advantage 3x "large," with 8-mm LED battery handle   --   --    30
  Schweizer 3X Kryptostar, with plug-in rechargeable
    handle                                             --   --    33
  Eschenbach 2.8X, with halogen plug-in handle         --   --    29
  Eschenbach 2.8X, with LED battery handle             --   --    18
  PowerMag+ 3X "HaloBright," with SMD LED handle       --   --    24
  Coil 2.8X, with xenon plug-in handle                 --   --    14
  Coil 2.8x, w/ LED battery handle                     --   --    3.5
Medium power (5X or 5.4X)
  Advantage 5X, with 8-mm LED battery handle           --   --    43
  Eschenbach 5X, with halogen plug-in handle           --   --    44
  Eschenbach 5X, with LED battery handle               --   --    19
  Schweizer 5X Kryptostar, with plug-in rechargeable
    handle                                             --   --    29
  PowerMag+ 5X "HaloBright," with SMD LED handle       --   --    27
  Coil 5.4X, with xenon plug- in handle                --   --    15
  Coil 5.4X, with LED battery handle                   --   --    4.5
High power (12X, 12.5, or 13X)
  Advantage 12X, with 8-mm LED battery handle          64   40    24
  Advantage 12X, with 5-mm LED battery handle          27   18    10
  Eschenbach 12.5X, with halogen plug-in handle        55   35    22
  Eschenbach 12.5X, with LED battery handle            38   34    14
  PowerMag+ 13X "HaloBright," with SMD LED handle      34   20    11
  Coil 12X, with xenon plug-in handle                  33   21    12
  Coil 12X, with LED battery handle                    8    6     4

                                                         AARP Magazine
                                                           article
                                                           (Medium
                                                           contrast)
                                                           Distance
                                                           (inches)
Brand and description of illuminated
stand magnifier                                         4     10    12

Low power (2.8X or 3X, 100 x 75 mm)
  Advantage 3x "large," with 8-mm LED battery handle   19     7     6
  Schweizer 3X Kryptostar, with plug-in rechargeable
    handle                                             16     6     5
  Eschenbach 2.8X, with halogen plug-in handle         14     5     5
  Eschenbach 2.8X, with LED battery handle             11     5     4
  PowerMag+ 3X "HaloBright," with SMD LED handle       13     4     3.7
  Coil 2.8X, with xenon plug-in handle                 8      3.5   3
  Coil 2.8x, w/ LED battery handle                     3      2.5   2
Medium power (5X or 5.4X)
  Advantage 5X, with 8-mm LED battery handle           25     8     --
  Eschenbach 5X, with halogen plug-in handle           19     6     --
  Eschenbach 5X, with LED battery handle               11     5     --
  Schweizer 5X Kryptostar, with plug-in rechargeable
    handle                                             15     5     --
  PowerMag+ 5X "HaloBright," with SMD LED handle       13.5   4.5   --
  Coil 5.4X, with xenon plug- in handle                9      4     --
  Coil 5.4X, with LED battery handle                   3.6    2.5   --
High power (12X, 12.5, or 13X)
  Advantage 12X, with 8-mm LED battery handle          --     --    --
  Advantage 12X, with 5-mm LED battery handle          --     --    --
  Eschenbach 12.5X, with halogen plug-in handle        --     --    --
  Eschenbach 12.5X, with LED battery handle            --     --    --
  PowerMag+ 13X "HaloBright," with SMD LED handle      --     --    --
  Coil 12X, with xenon plug-in handle                  --     --    --
  Coil 12X, with LED battery handle                    --     --    --

                                                         Newspaper
                                                         obituaries
                                                       (Low contrast)

Brand and description of illuminated
stand magnifier                                        1    1.5   2.5

Low power (2.8X or 3X, 100 x 75 mm)
  Advantage 3x "large," with 8-mm LED battery handle   --   --    23
  Schweizer 3X Kryptostar, with plug-in rechargeable
    handle                                             --   --    26
  Eschenbach 2.8X, with halogen plug-in handle         --   --    22
  Eschenbach 2.8X, with LED battery handle             --   --    12.5
  PowerMag+ 3X "HaloBright," with SMD LED handle       --   --    19
  Coil 2.8X, with xenon plug-in handle                 --   --    10
  Coil 2.8x, w/ LED battery handle                     --   --    3
Medium power (5X or 5.4X)
  Advantage 5X, with 8-mm LED battery handle           --   --    33
  Eschenbach 5X, with halogen plug-in handle           --   --    32
  Eschenbach 5X, with LED battery handle               --   --    16
  Schweizer 5X Kryptostar, with plug-in rechargeable
    handle                                             --   --    22
  PowerMag+ 5X "HaloBright," with SMD LED handle       --   --    21
  Coil 5.4X, with xenon plug- in handle                --   --    12
  Coil 5.4X, with LED battery handle                   --   --    4
High power (12X, 12.5, or 13X)
  Advantage 12X, with 8-mm LED battery handle          50   32    17
  Advantage 12X, with 5-mm LED battery handle          20   13    8.5
  Eschenbach 12.5X, with halogen plug-in handle        41   27    14
  Eschenbach 12.5X, with LED battery handle            31   23    12
  PowerMag+ 13X "HaloBright," with SMD LED handle      27   17    9
  Coil 12X, with xenon plug-in handle                  28   19    10
  Coil 12X, with LED battery handle                    7    5     3

                                                         Newspaper
                                                         obituaries
                                                       (Low contrast)
Brand and description of illuminated
stand magnifier                                         4     10    12

Low power (2.8X or 3X, 100 x 75 mm)
  Advantage 3x "large," with 8-mm LED battery handle   14     6     5
  Schweizer 3X Kryptostar, with plug-in rechargeable
    handle                                             14     5     4
  Eschenbach 2.8X, with halogen plug-in handle         10     5     4
  Eschenbach 2.8X, with LED battery handle             7      4     4
  PowerMag+ 3X "HaloBright," with SMD LED handle       10.5   4     3.6
  Coil 2.8X, with xenon plug-in handle                 7      3.3   3
  Coil 2.8x, w/ LED battery handle                     2.5    2     2
Medium power (5X or 5.4X)
  Advantage 5X, with 8-mm LED battery handle           20     7     --
  Eschenbach 5X, with halogen plug-in handle           15     5     --
  Eschenbach 5X, with LED battery handle               9      4     --
  Schweizer 5X Kryptostar, with plug-in rechargeable
    handle                                             13     4.5   --
  PowerMag+ 5X "HaloBright," with SMD LED handle       11     4     --
  Coil 5.4X, with xenon plug- in handle                7      3.4   --
  Coil 5.4X, with LED battery handle                   3.4    2.5   --
High power (12X, 12.5, or 13X)
  Advantage 12X, with 8-mm LED battery handle          --     --    --
  Advantage 12X, with 5-mm LED battery handle          --     --    --
  Eschenbach 12.5X, with halogen plug-in handle        --     --    --
  Eschenbach 12.5X, with LED battery handle            --     --    --
  PowerMag+ 13X "HaloBright," with SMD LED handle      --     --    --
  Coil 12X, with xenon plug-in handle                  --     --    --
  Coil 12X, with LED battery handle                    --     --    --

Note: The Eschenbach halogen plug--in handle was nonrheostat. All
LED battery handles used new batteries. Schweizer Kryptostar is
not available in 12X  or 13X.
COPYRIGHT 2010 American Foundation for the Blind
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2010 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Practice Report
Author:Gerritsen, Bryan
Publication:Journal of Visual Impairment & Blindness
Geographic Code:1USA
Date:Apr 1, 2010
Words:3213
Previous Article:Could specific braille reading difficulties result from developmental dyslexia?
Next Article:Education for students with visual impairments in Singapore: an overview of primary and secondary programs.
Topics:

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters