1040-5488/15/9202-e60/0 VOL. 92, NO. 2, PP. e60Ye61 OPTOMETRY AND VISION SCIENCE Copyright * 2014 American Academy of Optometry

CORRESPONDENCE

Letter to the Editor: Changes in Macular Function after Ozurdex for Retinal Vein Occlusion We congratulate Querques et al.1 for their study entitled ‘‘Changes in Macular Function after Ozurdex for Retinal Vein Occlusion.’’ The authors investigated the relationship between the changes in macular morphology and function after intravitreal dexamethasone implant (Ozurdex) for retinal vein occlusion. The study reports important results especially in terms of ocular electrophysiology and retinal morphology. The authors reported that at 1 month, mean best-corrected visual acuity, retinal sensitivity, and central macular thickness (CMT) improved significantly. Improvement remained significant for retinal sensitivity and CMT at the third month. However, these improvements were no longer significant at the fourth month. In addition, the changes in multifocal electroretinogram (mfERG) were not significant at any of the time points. The authors reported significant correlations between functional (except mfERG) and morphological measures. The authors did not perform the correlations between mfERG and morphological measures. Although there was no reported significant difference in mfERG, we wonder about the possible correlation between mfERG and morphometric parameters at the pretreatment point. We know that mfERG is primarily a function of cone photoreceptors.2 For this reason, it might be more reasonable to correlate mfERG changes with cone outer segment tip (COST) thickness. We previously found similar results in that CMT was not significantly correlated to mfERG in patients with diffuse diabetic macular edema after intravitreal triamcinolone injection. 3 However, in our study, we did not have COST thickness of the patients. We would be particularly interested in any correlations the authors found between mfERG and COST thickness. This new

statistics will clarify whether COST thickness alone may be used as a biomarker for objective retinal function as assessed by mfERG in patients with retinal vein occlusion.

3. Durukan AH, Memisoglu S, Gundogan FC. Is multifocal ERG a reliable index of macular function after triamcinolone acetonide injection in diffuse diabetic macular edema? Eur J Ophthalmol 2009; 19:1017Y27.

Ahmet Tas$, MD Agr{, Turkey Salih Altun, MD ¨ mer Faruk S$ahin, MD O Ankara, Turkey Abdullah Ilhan, MD Erzurum, Turkey Fatih C. Gundogan Ankara, Turkey

REFERENCES 1. Querques G, Cascavilla ML, Cavallero E, Triolo G, Querques L, Lattanzio R, Cicinelli MV, Preziosa C, Borrelli E, Bandello F. Changes in macular function after ozurdex for retinal vein occlusion. Optom Vis Sci 2014;91:760Y8. 2. Gundogan FC, Sobaci G, Bayraktar MZ. Intra-sessional and inter-sessional variability of multifocal electroretinogram. Doc Ophthalmol 2008;117:175Y83.

Authors’ Response We thank Dr. Tas et al. for their interest on our recent article describing the relationship between the changes in macular morphology and function after intravitreal dexamethasone implant (Ozurdex) for retinal vein occlusion.1 In our study, we found significant correlations between several functional and morphological measures. However, as correctly pointed out by the authors, we did not report the correlations between multifocal electroretinogram (mfERG) (which did not change significantly after treatment) and morphological measures; indeed, this analysis, which was performed along with all other calculations, has been omitted because of the absence of significant correlations (both before and after treatment). Particularly, we did not find any correlation between mfERG changes

TABLE 1.

Correlation analysis (Pearson) at each time point among functional and morphological parameters COST

mfERG P1R1 mfERG P1R2 mfERG N1R1 mfERG N1R2

R p R p R p R p

Baseline (n = 19)

1 mo (n = 19)

3 mo (n = 19)

4 mo (n = 17)

5 mo (n = 13)

6 mo (n = 7)

j0.197 0.434 0.07 0.784 j0.007 0.978 j0.117 0.644

j0.018 0.943 j0.268 0.283 0.119 0.638 0.038 0.881

0.354 0.15 j0.133 0.598 j0.175 0.488 0.109 0.666

j0.238 0.341 j0.219 0.382 j0.036 0.886 0.252 0.313

j0.261 0.296 j0.11 0.664 0.174 0.491 0.127 0.615

0.045 0.858 0.368 0.133 0.267 0.284 j0.198 0.432

R, Pearson correlation coefficient; COST, cone outer segment tip thickness; mfERG P1R1-R2/N1R1-R2, amplitude relative of the first positive (P1)/negative (N1) peek in ring 1 (R1) and ring 2 (R2) on multifocal electroretinography.

Optometry and Vision Science, Vol. 92, No. 2, February 2015

Copyright © American Academy of Optometry. Unauthorized reproduction of this article is prohibited.

Letter to the editor: Changes in macular function after ozurdex for retinal vein occlusion.

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