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Evaluation of focal retinal function using multifocal electroretinography in patients with x-linked retinoschisis (CJO Vol. 45, No. 5)
Letters to the Editor
Evaluation of focal retinal function using multifocal electroretinography in patients with x-linked retinoschisis (CJO Vol. 45, No. 5) Dear Editor, In an article published in CJO in October 2010, Sen et al. evaluated focal retinal function using a multifocal electroretinogram (mfERG) in patients with x-linked retinoschisis (XLRS).1 The authors studied 18 eyes in 9 patients with XLRS. We want to make contribution and ask a question that may further increase the value of the mfERGs obtained from the patients. The authors reported that peripheral retinoschisis was seen in 9 of 18 eyes (50%). However, in full-field electroretinograms (ffERGs), all eyes have prolonged implicit times of a and b waves in all 5 responses. Because ffERG is the mass response of the retina to a flash of light, this finding functionally shows the subclinical peripheral retinoschisis. In addition, as the authors noted, a multiarea amplitude decrease in eyes with XLRS shows the dysfunction which is beyond the macula. These 2 findings show the value of ffERG and mfERG in the evaluation of patients with XLRS. As the authors stated, the inconsistent N1 implicit time findings in the inner 3 rings of mfERG in previously published studies is possibly related to the inaccurate marking of the N1 peak by the automated recording system. This is
Author’s Response Dear Editor, We thank Gundogan et al for taking interest in our study. As correctly pointed out abnormal ffERG points towards the fact that XLRS is a global retinal dysfunction. This is explained by the underlying pathophysiology of the disease as well as the characteristic negative response on ffERG seen in most of the patients with XLRS with or without the presence of peripheral retinoschisis. Hence, both ffERG and mfERG have a role to play in the management of these patients. As mentioned by the authors the N1 and P1 amplitudes are best marked manually. The same has been followed through out the present study. Statistical analyses in order to explore the relationship (correlation analyses) between the disease history (time of onset of defective vision) and mfERG P1/N1 amplitude/ implicit times and ffERG amplitude/implicit times could
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an important issue in the evaluation of ocular electrophysiologic tests. The physician is responsible for the accurate marking of the peak. Sometimes amplitudes can be so small that accurate markings may be impossible in routine clinical testing. We kindly ask the authors to perform statistical analyses (correlation analyses) in order to explore the relationship between the disease history (time of onset of defective vision) and the mfERG P1/N1 amplitude/implicit times and ffERG amplitude/implicit times. The results of these statistics will show us the best way to follow-up patients with XLRS—mfERG or ffERG. Fatih C. Gundogan*, Ahmet Tas†, Omer Faruk Sahin* *
Department of Ophthalmology, Etimesgut Military Hospital, Ankara, Turkey; and †Department of Ophthalmology, Mevki Military Hospital, Ankara, Turkey Correspondence to: Fatih C. Gundogan, MD: [email protected] REFERENCE 1. Sen P, Roy R, Maru S, Ravi P. Evaluation of focal retinal function using multifocal electroretinography in patients with x-linked retinoschisis. Can J Ophthalmol. 2010;45:509-13. Can J Ophthalmol 2012;47:192
0008-4182/11/$-see front matter © 2012 Published by Elsevier Inc on behalf of the Canadian Ophthalmological Society. doi:10.1016/j.jcjo.2012.01.016
be useful in follow up of these patients. However because of the small sample size, the correlation and regression is not possible. Also, all 9 patients in our study were approximately in the second decade of life (Average age of the patients was 14.7 years with a range of 9-21 years). A study group with subjects in different age groups would probably be more apt for such an analysis. Parveen Sen Senior Consultant Shri Bhagwan Mahavir Vitreo-Retinal Services Sankara Nethralaya, Medical Research Foundation Correspondence to: Parveen Sen, MS: [email protected] Can J Ophthalmol 2012;47:192
0008-4182/11/$-see front matter © 2012 Published by Elsevier Inc on behalf of the Canadian Ophthalmological Society. doi:10.1016/j.jcjo.2012.03.002
Evaluation of focal retinal function using multifocal electroretinography in patients with x-linked retinoschisis (CJO Vol. 45, No. 5) Dear Editor, In an article published in CJO in October 2010, Sen et al. evaluated focal retinal function using a multifocal electroretinogram (mfERG) in patients with x-linked retinoschisis (XLRS).1 The authors studied 18 eyes in 9 patients with XLRS. We want to make contribution and ask a question that may further increase the value of the mfERGs obtained from the patients. The authors reported that peripheral retinoschisis was seen in 9 of 18 eyes (50%). However, in full-field electroretinograms (ffERGs), all eyes have prolonged implicit times of a and b waves in all 5 responses. Because ffERG is the mass response of the retina to a flash of light, this finding functionally shows the subclinical peripheral retinoschisis. In addition, as the authors noted, a multiarea amplitude decrease in eyes with XLRS shows the dysfunction which is beyond the macula. These 2 findings show the value of ffERG and mfERG in the evaluation of patients with XLRS. As the authors stated, the inconsistent N1 implicit time findings in the inner 3 rings of mfERG in previously published studies is possibly related to the inaccurate marking of the N1 peak by the automated recording system. This is
Author’s Response Dear Editor, We thank Gundogan et al for taking interest in our study. As correctly pointed out abnormal ffERG points towards the fact that XLRS is a global retinal dysfunction. This is explained by the underlying pathophysiology of the disease as well as the characteristic negative response on ffERG seen in most of the patients with XLRS with or without the presence of peripheral retinoschisis. Hence, both ffERG and mfERG have a role to play in the management of these patients. As mentioned by the authors the N1 and P1 amplitudes are best marked manually. The same has been followed through out the present study. Statistical analyses in order to explore the relationship (correlation analyses) between the disease history (time of onset of defective vision) and mfERG P1/N1 amplitude/ implicit times and ffERG amplitude/implicit times could
192
CAN J OPHTHALMOL—VOL. 47, NO. 2, APRIL 2012
an important issue in the evaluation of ocular electrophysiologic tests. The physician is responsible for the accurate marking of the peak. Sometimes amplitudes can be so small that accurate markings may be impossible in routine clinical testing. We kindly ask the authors to perform statistical analyses (correlation analyses) in order to explore the relationship between the disease history (time of onset of defective vision) and the mfERG P1/N1 amplitude/implicit times and ffERG amplitude/implicit times. The results of these statistics will show us the best way to follow-up patients with XLRS—mfERG or ffERG. Fatih C. Gundogan*, Ahmet Tas†, Omer Faruk Sahin* *
Department of Ophthalmology, Etimesgut Military Hospital, Ankara, Turkey; and †Department of Ophthalmology, Mevki Military Hospital, Ankara, Turkey Correspondence to: Fatih C. Gundogan, MD: [email protected] REFERENCE 1. Sen P, Roy R, Maru S, Ravi P. Evaluation of focal retinal function using multifocal electroretinography in patients with x-linked retinoschisis. Can J Ophthalmol. 2010;45:509-13. Can J Ophthalmol 2012;47:192
0008-4182/11/$-see front matter © 2012 Published by Elsevier Inc on behalf of the Canadian Ophthalmological Society. doi:10.1016/j.jcjo.2012.01.016
be useful in follow up of these patients. However because of the small sample size, the correlation and regression is not possible. Also, all 9 patients in our study were approximately in the second decade of life (Average age of the patients was 14.7 years with a range of 9-21 years). A study group with subjects in different age groups would probably be more apt for such an analysis. Parveen Sen Senior Consultant Shri Bhagwan Mahavir Vitreo-Retinal Services Sankara Nethralaya, Medical Research Foundation Correspondence to: Parveen Sen, MS: [email protected] Can J Ophthalmol 2012;47:192
0008-4182/11/$-see front matter © 2012 Published by Elsevier Inc on behalf of the Canadian Ophthalmological Society. doi:10.1016/j.jcjo.2012.03.002