We thank He and Huang
1 for the opportunity to discuss the findings of our study.
2 We evaluated, in a large series of patients, the changes in the subfoveal choroidal thickness (SFCT) after cataract surgery, using the spectral-domain optical coherence tomography (SD-OCT) technique. We found that the SFCT increased at day 1, month 1, and month 3 after surgery. Our results reached statistical significance. We also observed that, in three patients who presented with a diagnosis of pseudophakic macular edema, the SFCT increased greatly at month 1 (+60%, +24%, and +13%) though the central retinal thickness increased only at month 2 after phacoemulsification.
There may be three different posterior boundaries for the measurement of subfoveal choroidal thickness: the posterior vessel border, inner border of the suprachoroidal layer, and inner border of the sclera.
3 Using different posterior boundary definitions in the same study would impact SFCT measurements and jeopardize the interpretation of the results. In our study, SFCT was measured from the outer surface of the hyperreflective line ascribed to the retinal pigment epithelium to the hyperreflective line of the inner sclera border, as described by Margolis and Spaide,
4 and more recently by Mrejen and Spaide.
5 The inner border of the sclera was determined manually by the observer. We did not use the hyporeflective band corresponding to the suprachoroidal layer as our posterior boundary in any of our patients.
In our study, all SFCT measurements were performed in the morning, between 9 AM and 12 AM. However, we did not take into account the diurnal variation of SFCT. Indeed, studies that have reviewed diurnal variations of SFCT are not numerous and still have demonstrated contrasting results.
6
The reproducibility of SFCT measurements has been evaluated in various studies.
5 There is a very good interobserver and intervisit reproducibility despite the lack of automated software.
5 In our study, SFCT measurements were done in triplicate by two independent trained examiners. We paid attention to choose the same OCT scan position at each visit.
The ANOVA was not used in our study. The department of statistics found it more accurate to use a paired Student's t-test for overtime comparison of SFCT measurements of the same patient.