We read with interest the interesting original research article by Giocanti-Auregan et al.,
1 that looked at the functional and anatomic outcomes in patients with serous retinal detachment (SRD) in diabetic macular edema (DME) treated with ranibizumab (RBZ). The retrospective study showed that at 12 months patients with SRD (SRD +ve ) achieved similar visual gains (+11 letters) compared with patients without SRD (SRD −ve; 12 letters,
P = 0.78). The authors suggested that similar gains are achieved regardless of the SRD status of the patient.
We believe that the results of the current study can be interpreted in a different way. The mean duration of DME was 12.56 months in the SRD group. Recent results from the post hoc analysis of RISE and RIDE studies have shown that patients with SRD receiving sham injections were more likely to have a final best corrected visual acuity of 20/100 or worse.
2 Therefore, untreated SRD is more likely to have a deleterious effect on final visual outcomes compared with other types of edema. The exclusion criteria included no previous bevacizumab injections during the last 6 months. In addition, the SRD −ve group had more laser treatments (
P = 0.04), indicating that the SRD +ve group was relatively undertreated prior to the start of the study. Furthermore, there is little data about the type of SRD −ve edema, whether it was diffuse edema or cystoid macular edema, especially in the light of data showing that diffuse retinal thickening responded more effectively to bevacizumab compared with the other types of edema.
3 In addition, there are other predictors of visual response, the more robust of which being disorganization of the inner retinal layers.
4 No reference was made about any of these other factors and whether they were matched in both groups. The authors only controlled for baseline visual acuity and not baseline central retinal thickness.
It is interesting to note in their data that the mean number of injections in the SRD +ve group was 5.2 injections compared with 5.5 injections in the SRD −ve group. The protocol relied mainly on visual outcomes to guide reinjection and not anatomic optical coherence tomography outcomes. In addition, they relied on visual stability as a guideline to stop injections. With 26.5% of patients having residual SRD at the end of 12 months, it is possible that these patients might have benefited from more injections of RBZ. Furthermore, the authors disputed the post hoc data from RISE and RIDE, which relied on a monthly regimen and showed that SRD was a positive predictor for visual outcomes. Patients in RISE and RIDE received on average 12 injections compared with five in the present study. Therefore, undertreatment could have possibly affected the final visual outcomes and indirectly might indicate the requirement for more frequent injections in patients with SRD.
With regards to the anatomic outcomes, patients achieved a rapid and dramatic decrease in the central retinal thickness from 625 to 349 μm after the first three injections in the SRD +ve group, with a slight increase to 391 at the end of the 12 months. A similar trend was observed with the visual acuity in the SRD +ve group showing an increase from 45 letters to 59 letters at 3 months before dropping to 56 letters at month 12. Again, this is further indication of undertreatment. Had the authors relied on both anatomic and visual parameters, perhaps the final visual outcomes might have been different. In addition, data from large randomized clinical trials by the Diabetic Retinopathy Clinical Research Network (DRCRnet) have shown that the average number of injections in the first year is closer to nine.
5,6
Therefore, it is our belief that in a protocol addressing both visual and anatomic parameters to guide treatment, SRD might be associated with better visual outcomes. Furthermore, a study of individual parameters without consideration or controlling for other predictive factors such as disorganization of retinal inner layers or ellipsoid-zone and external limiting membrane integrity might not be entirely accurate and future studies have to put that into consideration.
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