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LETTER TO EDITOR
Year : 2004  |  Volume : 52  |  Issue : 2  |  Page : 175

The Sweep-VEP: A faster estimation of visual acuity in preverbal children



Correspondence Address:
V Vedantham


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Source of Support: None, Conflict of Interest: None


PMID: 15283233

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How to cite this article:
Vedantham V, Ratnagiri PK. The Sweep-VEP: A faster estimation of visual acuity in preverbal children. Indian J Ophthalmol 2004;52:175

How to cite this URL:
Vedantham V, Ratnagiri PK. The Sweep-VEP: A faster estimation of visual acuity in preverbal children. Indian J Ophthalmol [serial online] 2004 [cited 2020 Feb 23];52:175. Available from: http://www.ijo.in/text.asp?2004/52/2/175/14594

Dear Editor,

We read with that interest the article by Sharma et al[1], on "Comparative evaluation of Teller and Cardiff acuity tests in normals and unilateral amblyopes in under-two-year-olds". The authors deserve to be congratulated for their scientific comparison of the two methods of visual acuity estimation in the preverbal age group. In this context, we woul like to draw attention towards another equally effective method employed in testing preverbal children, handicapped patients or those in whom communication difficulties preclude other kinds of behavioural tests.

The Sweep technique described in 1985 by Norcia et al,[2] allows Visually Evoked Potental (VEP) to be measured in only a few seconds. Similar to conventional VEP-testing, filtering and Fourier data analysis are performed. The short examination time guarantees a great reduction in the problems pertaining to the maintenance of attention and stable fixation, even in newborns. Some S-VEP programs contain movie clips that could be played to capture the infant's attention. After achieving this, the pattern stimulator is turned on. The S-VEP employs vertical stripes for testing and the feature size is simply the width of the stripe. The inbuilt S-VEP program then computes the acuity from the VEP data. This represents a great advantage over other methods such as preferential looking and the routine pattern Visually Evoked Potentials (p-VEPs). The latter are dependent on good cooperation, since the presented patterns have to be fixated for several minutes by the children. Additionally the sweep-VEP method could also be modified to test contrast sensitivity[3] and colour vision in infants.[4]

Whether visual acuity estimation using Teller acuity cards is superior to S-VEP is unclear at present. There is only one study that has compared both in infants.[5] The expected maturational changes between 4 and 8 months of age were readily detectable by all the methods that also provided valid and reliable test-retest data. There was however, poor correlation between the testing methods suggesting that each test assesses a different aspect of vision.

We have recently started employing the technique of S-VEP in our institute and have found it to work reasonably well. The disadvantage, of course, is that it needs good, but expensive electrophysiologic equipment.



 
  References Top

1.
Sharma P, Bairagi D, Sachdeva MM, Karu K, Khokhar S, Saxena R. Comparative evaluation of Teller and Cardiff acuity tests in normals and unilateral amblyopes in uder-two-year-olds. Ind J Ophthalmol 2003; 51: 341-45  Back to cited text no. 1
    
2.
Norcia AM, Tyler CW. Spatial frequency sweep VEP: visual acuity during the first year of life. Vision Res 1985;25: 1399-408.   Back to cited text no. 2
    
3.
Norcia AM, Tyler CW, Hamer RD. Development of contrast sensitivity in the human infant. Vision Res 1990;30:1475-86   Back to cited text no. 3
    
4.
Ver Hjoeve JN, France TD, Bousch GA. A sweep VEP test for color vision deficits in infants and young children. J Pediatr Ophthalmol Strabismus 1996;33:298-302.   Back to cited text no. 4
    
5.
Prager TC, Zou YL, Jensen CL, Fraley JK, Anderson RE, Heird WC. Evaluation of methods for assessing visual function of infants. J AAPOS 1999;3: 275-82  Back to cited text no. 5
    




 

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