Metamorphopsia Assessment before and after Vitrectomy for Macular Hole

We read with interest the article, “Metamorphopsia Assessment before and after Vitrectomy for Macular Hole.” ¹ We congratulate Krøyer et al. for describing a novel method of assessing metamorphopsia. However, we are seeking clarification regarding the methodology and the conclusions. 

1.  
   We would like to know whether the test–retest variability of the method has been validated.
2.  
   The pre- and postoperative means and standard deviations of the interocular disparities at various eccentricities have not been clearly stated. In such a scenario, it is difficult to put the significance of the P value into perspective.
3.  
   A pre- and postoperative visual disability questionnaire may have produced more informative results.
4.  
   In the original Copenhagen Macular Hole Study, 78 eyes were enrolled. ² The basis of choosing 55 of those patients for this study is not clear.
5.  
   The Mann-Whitney rank sum test, which was used to compare pre- and postoperative metamorphopsia is meant for comparing the means of two independent samples. As the pre- and the postoperative groups were dependent, the Wilcoxon signed rank test seems more appropriate. The effect of eccentricity on metamorphopsia was determined by the analysis of variance test, which is for parametric data. As the distribution is nonparametric, the Kruskal-Wallis test seems more appropriate.
6.  
   The results report that eight patients underwent reoperation to close the hole and that four patients did not show any change in metamorphopsia after surgery. Were these four patients among those who underwent reoperation?

It would be useful to the readers to have the authors clarify these points.