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LETTER TO EDITOR
Year : 2020  |  Volume : 58  |  Issue : 3  |  Page : 231

Visual evoked potential study in diabetic retinopathy


Emeritus Professor of Neurology, The Tamil Nadu Dr. MGR Medical University, Chennai, Tamil Nadu, India

Date of Submission18-Mar-2020
Date of Acceptance01-May-2020
Date of Web Publication14-Sep-2020

Correspondence Address:
Dr. P A Bhaskar
12 Branson Garden Road, Kilpauk, Chennai - 600 010, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_22_20

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How to cite this article:
Bhaskar P A. Visual evoked potential study in diabetic retinopathy. TNOA J Ophthalmic Sci Res 2020;58:231

How to cite this URL:
Bhaskar P A. Visual evoked potential study in diabetic retinopathy. TNOA J Ophthalmic Sci Res [serial online] 2020 [cited 2020 Oct 20];58:231. Available from: https://www.tnoajosr.com/text.asp?2020/58/3/231/294978



Sir

The article on “Evaluation of visual evoked potential as a predictive marker for diabetic retinopathy” by Chaudri et al. which appeared in the TNOA Journal (2019;57:294-8) portrays a well-planned and meticulously executed study.

However, from the neurological perspective, the following points may have to be borne in mind and clarified:

  1. While employing the checkerboard pattern reversal, the size of the individual check or the angle the check subtends at the macula needs to be specified because the smaller the check, the more the delay in the P100 latency.[1] In general, much importance is not given to the amplitude of P100 wave in routine testing for basic clinical conditions. This is because the amplitude can change with alterations made in the parameters used for the stimulation (especially luminance and reversal frequency). Variations in the pupil size may also affect the amplitude[2]
  2. The P100 latency is the measure of the composite time taken by the electrical signal to reach the cortex after the stimulus is delivered to the retina. Thus, any delay in the time taken for the signal to reach the cortex (and to be picked up as the P100 wave) can occur at the retina itself or posteriorly in the optic nerve or anywhere along the optic pathway. In the present article, the authors are trying to convey the prime message that delay in electrical conduction (viz., prolonged P100 latency) often precedes the appearance of clinical features as well as structural changes in the retina. Therefore, it would have been ideal if an electroretinogram had also been simultaneously performed on the patients (and controls). This would have revealed more precisely where the delay in the P100 had taken place as to whether it had occurred at the retinal level or more posteriorly (by calculating the “retinocortical time”).[3] This is necessary because retroretinal delay in signal conduction, leading to delayed P100, can also happen in diabetes
  3. In addition to the blood sugar levels, some authors have attempted to correlate the P100 latency with the duration of diabetes and the HbA1C level in the blood.[4] One such recent study had been reported from Chennai.[5] This can also form a good protocol while screening diabetic patients using the visual evoked potential test before the appearance of clinical and/or fundoscopic changes.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Kurita-Tashima S, Tobimatsu S, Nakayama-Hiromatsu M, Kato M. Effect of check size on the pattern reversal visual evoked potential. Electroencephalogr Clin Neurophysiol 1991;80:161-6.  Back to cited text no. 1
    
2.
Tobimatsu S, Celesia CG, Cone SB. Effects of pupil diameter and luminance changes on pattern electroretinograms and visual evoked potentials. Clin Vis Sci 1988;2:293-9.  Back to cited text no. 2
    
3.
Kaufman D, Celesia CG. Simultaneous recording of pattern electro-retinogram and visual evoked responses in neuro-ophthalmological disorders. Neurology 1985;35:644-8.  Back to cited text no. 3
    
4.
Balta O, Sungur G, Yakin M, Unlu N, Balta OB, Ornek F. Pattern visual evoked potential changes in diabetic patients without retinopathy. J Ophthalmol 2017;2017:8597629.  Back to cited text no. 4
    
5.
Venkatesh SS, Subhapriyadarshini S. Study on VEP changes in patients with type II diabetes without retinopathy. J Evid Based Med Healthc 2018;5:3092-7.  Back to cited text no. 5
    




 

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