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William Lang, Dr Alison LaVoy, Dr Brian Lewis, Dr Elliot Liff, Dr Martin Mass, Dr Charles McDonald, Dr Robert Mithun, Dr Michael Pawlik, Dr Lester Solomon, and Dr Frederick Whinery who referred patients to the

study. REFERENCES

1. Horsburgh CR Jr. Mycobacterium avium complex infection in the acquired immunodeficiency syndrome. N Engl J Med 1991; 324: 1332-38. et al. Quadruple-drug therapy for Mycobacterium avium-intracellulare bacteremia in AIDS patients. J Infect Dis 1990; 161: 801-05. 3. Benson CS, Kessler HA, Pottage JC Jr, et al. Successful treatment of acquired immunodeficiency syndrome-related Mycobacterium avium complex disease with a multiple drug regimen including amikacin.

2. Hoy J, Mijch A, Sandland M,

Arch Intern Med 1991; 151: 582-85. AE, Girard D, English AR, et al. Pharmacokinetic and in vivo studies with azithromycin (CP-62,993), a new macrolide with an extended half-life and excellent tissue distribution. Antimicrob Agents Chemother 1987; 31: 1948-54. 5. Gladue RP, Snider ME. Intracellular accumulation of azithromycin by cultured human fibroblasts. Antimicrob Agents Chemother 1990; 34: 1056-60. 6. Inderlied CB, Kolonoski P, Wu M, et al. In vitro and in vivo activity of azithromycin (CP 62,993) against the Mycobacterium avium complex. J Infect Dis 1989; 159: 994-97. 7. Inderlied CB, Young LS, Yamada J. Determination of in vitro susceptibility of Mycobacterium avium complex isolates to antimycobacterial agents by various methods. Antimicrob Agents Chemother 1987; 31: 1697-702. 8. Crowle AJ, Dahl R, Ross E, et al. Evidence that vesicles containing living, virulent Mycobacterium tuberculosis or Mycobacterium avium in cultured human macrophages are not acidic. Infect Immun 1991; 59: 1823-31. 9. Black CM, Bermudez LEM, Young LS, et al. Co-infection of macrophages modulates interferon gamma and tumor necrosis factorinduced activation against intracellular pathogens. J Exp Med 1990; 172: 977-80. 4. Girard

ADDRESSES: Kuzell Institute for Arthritis and Infectious Diseases, Medical Research Institute of San Francisco, San Francisco, California, USA (Prof L. S Young, MD, M. Wu, BA, P. Kolonoski, BA, R Bolan, MD, C. B. Inderlied, PhD); Pacific Presbyterian Medical Center, San Francisco (L. S. Young, L. Wiviott, MD, M Wu, R Bolan); and Department of Pathology and Laboratory Medicine, Children’s Hospital, University of Southern California, Los Angeles, California (C. B. Inderlied). Correspondence to Prof Lowell S. Young, Kuzell Institute, 2200 Webster Street, Suite 305, San Francisco, California 94115, USA

Yellow spectacles to improve vision in children with binocular

amblyopia

Yellow spectacles were given to 20 children who had binocular amblyopia. Immediately, their vision improved. Furthermore, in the younger children, after they had worn the yellow lenses for up to nine months, this improvement persisted even when they were not wearing the spectacles. Yellow filters may help these children with binocular amblyopia because they remove the blue fringes that are due to chromatic aberration of the eye.

Binocular amblyopia is said

suppression, amblyopia,

to be rare. Cortical which is the usual cause of monocular is unlikely if both eyes are equally

disadvantaged. At the orthoptic department, Royal Berkshire Hospital, we see about 600 new children aged between 6 and 14 years each year; 400 are referred for learning difficulties and 200 for squints, blurred vision, and other visual disorders. In view of the rarity of binocular amblyopia, we were surprised to find that we were seeing about 1 child every two months (ie, 1 % of these referrals) with reduced vision in both eyes without a clear cause. There have been claims that tinted lenses alleviate a wide range of visual disorders. Yellow filters cut out the short (ultraviolet and blue) wavelengths which not only are potentially damaging but also cause the blurring effects of chromatic aberration. The wearing of yellow filters improves several aspects of vision, including the contrast sensitivity in normal individuals, especially at lower spatial frequencies,2,3 and the apparent brightness of large targets under daylight conditions.4 Furthermore, Kinney et al5 showed that the response to the appearance of a black and white striped grating stimulus was faster when subjects were wearing yellow filters. We therefore decided to investigate whether coloured filters, especially yellow, might benefit children with binocular amblyopia. 20 children (9 boys, 11 girls) with binocular amblyopia were referred from 1988 to 1990. Full medical and ophthalmological histories were taken, with special attention to possible psychological influences. Each child was refracted by an ophthalmologist, with cycloplegics if necessary. Fundi were also carefully inspected; no abnormalities were seen. In 3 children flash electroretinograms were recorded, these were also normal. A full orthoptic examination consisted of: (1) monocular and binocular visual acuities (Snellen chart with and without pinholes); (2) binocular function (cover test); (3) monocular and binocular accommodation and near-point for convergence ("RAF rule"), and

convergence eye movements (infrared eye movement recorder); (4)

depth perception (Randot test); (5) contrast sensitivity function (Vistech chart and, in 3 children, a ’Joyce’ screen [p4 phosphor] by which contrast sensitivities were measured through neutral density, yellow and blue filters, which were carefully matched to transmit the same amount of light); (6) colour vision (Ishihara plates [all children], ‘Farnsworth-Munsell 100 Hue Colour Vision Test’ [10], Rayleigh colour matching [7]). Various methods were used to exclude the possibility that symptoms were psychosomatic. For example, the children were asked to look through a magnifying lens, which was then cancelled out with one of opposite power. In no instance did a child’s vision improve. Each child was then asked to attempt to read normal print through four coloured overlays presented in a random order: yellow (Wratten filter 4), green (Wratten filter 58), red (Wratten filter 25), and blue (Wratten filter 47). A neutral density filter which cut out 50% of the light at all wavelengths was also presented. The children were asked which condition they found clearest. The mean visual acuity for our group was 6/10-5 (range 6/5-6/18). 6/6 is ’normal’, but 6/4 is common for children of this age. 4 children had acuities as low as 6/18. Pinholes did

improve acuity. In 17 children acuity was reduced equally in both eyes; in the other 3 the difference between the eyes was only one line. Although all children had reduced acuity, no child had a refractive error greater than ± 0-5 dioptres. All the children had normal binocular single vision (bifoveal fixation, no squint, and normal fusion), not

normal binocular function, and normal binocular control. The accommodation of all the children was reduced. With N5 or N8 sized print, depending on acuity, the near-point for clear vision averaged 17-8 cm (range 8-28; normal 6) on the RAF rule. In the Randot test, 7 children could not even detect the largest disparity used (400 arc") and the other showed reduced responses (mean 171", range 40-400;

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spectacles, acuity remained higher and near-point of accommodation closer, contrast sensitivity function approached normal, and stereoacuity was higher. Furthermore, in the 6 youngest (< 10 years) children, this improvement was now permanent, even when they were not wearing the spectacles, and the improvements were sustained for a further six months of follow-up. During the next six months, 13 more children stopped requiring the spectacles as their vision became more normal. It is claimed that bilateral amblyopia may improve spontaneously. We doubt that this happened in our group

Spatial frequency (cycles Contrast

per

degree)

sensitivity functions.

Contrast sensitivity is measured by determining the contrast threshold, which is the percentage difference between black and white bars that observers can just detect Open circles=mean contrast threshold of this group of children; closed circles = improvement in mean contrast threshold with yellow filters. Normal range is shown by shaded area.

normal < 20"). The contrast sensitivity of each child was at least one point lower than normal at all spatial frequencies. Hence the mean contrast sensitivity function for the children together was significantly lower than the normal range for children (figure). 5 children gave normal responses in the Ishihara colour vision test. The other 15 had unusual responses but none could clearly be classed as standard red/green colour blind. Children tested with the Farnsworth-Munsell 100 Hue test showed a high variability, a common finding in children of this age. All 7 children who did Rayleigh colour matches were normal. Thus, there was no evidence that the children had any degree of colour blindness that could play a part in amblyopia. There was no family history of colour blindness, and in contrast to hereditary colour blindness there were as many girls as boys. When asked to read through the coloured or neutral density overlays, all the children said that the yellow overlay improved their vision greatly; none of them preferred any other colour. They disliked blue most, but found that red, green, and neutral density made little difference. Therefore we retested visual acuity, near-point of accommodation, Randot stereoacuity, and contrast sensitivity while the children were wearing yellow spectacles that had the same transmission spectrum as the yellow overlay. All visual functions improved when the children wore the yellow spectacles. Average visual acuity improved by about 5-5 m from 6/10-5 to 6/5 and 2 of the children went from 6/18 to 6/4. The mean accommodative near-point improved from 18 to 9 cm. The disparity that they could detect in the Randot depth perception test improved from 171 to 55". All these differences were statistically significant

(p

Yellow spectacles to improve vision in children with binocular amblyopia.

Yellow spectacles were given to 20 children who had binocular amblyopia. Immediately, their vision improved. Furthermore, in the younger children, aft...
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