We thank Khanduja and associates for their interest in our work and their thoughtful comments. Our time-domain optical coherence tomography (TD OCT) study was performed using the radial lines protocol, in which 512 pixels per line were obtained. In addition to these 6 radial lines, a fast macular thickness protocol was performed, resulting in a map with the values of the retinal thickness in the central 1-, 3-, and 6-mm area. Because of the nature of the irradiating 6 radial lines, the further from the foveal center, the higher the chance of missing small retinal cysts. In spectral-domain OCT machines, scanning protocols of vertical and horizontal lines can be chosen, but in clinical practice, there is always a compromise in choosing the scan width and a chance of missing abnormalities. It is possible theoretically that some of our discrepancies were caused by missing small isolated retinal cysts in between the scanning lines in a retina of normal thickness. However, it is more probable that the FA-positive/OCT-negative discrepancies were caused by true differences in combination with the limited resolution of the TD OCT scan, although the highest resolution (512 pixels/line) was used.

In their comment, Khanduja and associates suggest that atrophic retinas with macular edema (ME) could be discovered on OCT by the presence of cysts. However, diffuse macular edema manifests without cysts. Purely relying on the presence of retinal cysts can be misleading. Retinal thickening in an already atrophic retina resulting from long-standing edema or inflammation then may remain unnoticed. Longitudinal measurements of the changes in the retinal thickness are needed to note an excess of fluid present in an atrophic retina and to make the diagnosis of ME.

The suggestion to compare the patients with a first attack, a recurrent attack, and inactive uveitis is valuable. Our study was based mainly on patients with chronic macular edema and including the patients with macular edema in its very early phase may reveal different percentages of discrepancies compared with our results. However, we assessed our population for the duration of the uveitis and ME, and we did make the difference between active versus inactive uveitis and found that the duration of the ME and the activity of uveitis did not differ between the FA-positive/OCT-negative group and the FA-positive/OCT-positive group.

We agree that, in addition to the higher-resolution OCT, the differences in the composition of the study group of Khanduja and associates and our study groups might have contributed to the differences in the prevalence of the discrepancies between FA and OCT imaging.

In conclusion, we point out that discrepancies between the FA and OCT findings occur because these 2 investigations reveal different ME characteristics, specifically morphologic and functional features. The ophthalmologists caring for the patients with ME should be aware of possible pitfalls using only 1 of these imaging methods.

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Jan 9, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Reply

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