In this study, 40 obese patients were investigated for the effect of bariatric surgery on the macular thickness and macular vascular density in both superficial and deep plexuses. Central macular thickness (CMT) in whole macula in our study preoperatively was 274.55±7.9 µm with mean BMI of 55.31±5.1 Kg/m2.
In 2016, Dogan et al studied a group of 67 patients defined as having morbid or class III obesity with mean BMI of 49.15 ± 7.65 kg/m2 and CMT of 240.99 ± 21.47 µm, and compared them with 29 age- and sex matched non-obese individuals with mean BMI of 22.99 ± 1.89 kg/m2 and CMT of 240.99 ± 21.47µm. No significant statistical difference of CMT was detected (p= 0.072). CMT was measured using SD-OCT (Cirrus HD OCT, Carl Zeiss Meditec, Dublin, CA, USA) .
The CMT in our study preoperatively was higher than the CMT of the obese group in Dogan’s study, although our mean BMI was higher than theirs. This could be explained by the mean age difference between both studies in addition to the ethnic difference .
In the current study, significant increase in the macular thickness areas of fovea and parafovea (average, Superior-Hemi and Inferior-Hemi) was detected 3 months after bariatric surgery (p<0.05). However, there was no significant increase in the macular thickness area and areas of perifovea (average, Superior-Hemi and Inferior-Hemi) 3 months after the surgery (p˃0.05).
Our results were similar to Brynskov et al, in which the retinal thickness of 51 patients with type 2 diabetes with no diabetic retinopathy was examined 2 weeks before and 1, 3, 6 and 12 months after bariatric surgery using Spectral domain OCT (Heidelberg Spectralis, Heidelberg Engineering GmbH, Heidelberg, Germany). Their study showed significant increase in the macular thickness (Total macula, Fovea, Parafovea and Perifovea), started at 3rd postoperative month with its peak at the 6th month then dropped back after 12 months .
OCTA is an emerging noninvasive tool for imaging and quantifying retinal vasculature at the level both superficial and deep plexuses and areas of non-perfusion such as FAZ. Utilizing standard sectors to measure the vascular density in the macular and the peripapillary regions allows the application of a uniform method to measure the VD in different ophthalmological conditions .
In normal subjects, it was found that the macular VD in the deep plexus was higher than the superficial retinal plexuses .
The current study also showed that preoperative macular VD in the deep plexus is higher than the superficial plexus in all macular regions. This finding was not far from that of Zhang et al, who studied the VD before intraocular pressure changes .
To our knowledge this research was the first to study the effect of weight loss after bariatric surgery on the blood flow of the macular region by measuring the VD in both deep and superficial capillary plexuses in different macular areas by using OCTA AngioVue system (Optovue RTVue XR Avanti; Optovue, Inc., Fremont, CA, USA).
We detected significant statistical increase in macular VD in the deep capillary plexus of all macular areas 3 months after bariatric surgery (p<0.05). However, the macular VD in the superficial capillary plexus in all macular areas did not show significant difference (p˃0.05).
Significant correlations were detected in this study between changes in the BMI, 3 months postoperatively and changes in the macular thickness in certain areas as shown in table 3.
The significant improvement in the macular VD of the deep plexus in our results can be explained by Çekiç et al who showed the effect of bariatric surgery using sleeve gastrectomy on the retrobulbar flow hemodynamic parameters. They found a significant increase in the central retinal artery and the ophthalmic artery blood flow measured by color doppler ultrasound 6 months, after a significant BMI reduction of 12.5 kg/m2 .
The insignificant improvement of the VD in the superficial plexus in all macular areas in the current study may be attributed to Takuhei Shoji et al, who stated that vascular measurements obtained by OCTA only reflect some aspects of blood flow within the detected vessels, and does not represent an estimate of real blood flow. Specifically, this modality detects vasculature based on amplitude decorrelation, which results from perfused vessels, but does not directly quantify the flow rate within the detected vessels .
This study is not free from limitations. In addition to the general limitations related to the OCTA technology itself , the short post-operative follow-up period that may prevent detection of other changes or more significant improvements in superficial plexus vascular density indices is an additional downside, hence further studies with longer follow-up are needed. Also, it represented the results of a single center only with relatively homogenous population with certain ethnic origin and it didn’t put the gender of the patients into consideration.
In conclusion, bariatric surgery had significant effect on some indices of macular VD measured by OCTA in obese patients 3 months postoperatively. OCTA can therefore be considered a valuable tool to assess the short term changes in the retinal microcirculation following significant weight reduction.