Results may represent a retinal degenerative change.
Reviewed by Kotaro Tsuboi, MD.
Location is everything, especially in the eye.
The inner fluid volume measured by optical coherence tomography (OCT) differs significantly in its size, shape, and distribution compared with the outer fluid volume and is associated with larger macular holes and poorer postoperative vision in contrast to the outer fluid volume.
Kotaro Tsuboi, MD
These findings suggest that the inner fluid volume represents a retinal degenerative change associated with more advanced macular holes, according to Kotaro Tsuboi, MD, a visiting scholar from Aichi Ika Daigaku, Nagakute, Aichi, Japan, at the Oregon Health and Sciences University.
These findings emerged from a study in which the investigators took a retrospective look at intraretinal cystoid spaces, which are often present next to macular holes, using the AngioVue OCT angiography (OCTA) and Avanti RTVue X (Optovue). All study patients had undergone a successful surgery to close a macular hole that included pars plana vitrectomy with internal limiting membrane peeling.
The OCTA software in the Avanti machine produced volumetric data and custom software, that we recently reported,1 generated volume-rendering OCT images of the intraretinal fluid spaces, Dr. Tsuboi explained.
The study included 42 eyes of 39 patients. The macular holes were classified according to the International Vitreomacular Traction Study classification as small in 11 eyes (26%), medium-sized in 11 eyes (26%), and large in 20 eyes (48%). Sixteen eyes (38%) had vitreomacular traction (VMT).
Of the 42 eyes, 39 eyes (93%) underwent combined phacovitrectomy and all eyes were pseudophakic postoperatively.
Importantly, large macular holes were associated with increased inner fluid volume compared to small macular holes, a difference that reached significance (p = 0.0030). No differences in the outer fluid volume were seen in association with the size of the macular holes, Dr. Tsuboi reported.
VMT did not seem to drive the inner and outer fluid volumes, which were similar in eyes with and without VMT.
The inner fluid volume and minimal macular hole size had a significant effect on the postoperative visual acuity (r = 0.44, p = 0.0033 and r = 0.43, p = 0.0045), while basal macular hole size (r = 0.21, p = 0.19), outer fluid volume (r = -0.17, p = 0.27) did not. The multivariate analysis found that the inner fluid volume was the only significant factor affecting the postoperative 12-month visual acuity (β = 0.41, p = 0.021).
Inner fluids are shown in green and outer fluids in red. Volume-rendering OCT shows the outer FV is greater than the inner FV. En face OCT demonstrates the different distribution pattern between inner and outer fluids. (Images courtesy of Kotaro Tsuboi, MD)
Optical coherence tomography = OCT; fluid volume = FV
The main takeaways from the study were that OCT showed that the inner fluid differed significantly in size, shape, and distribution compared to the outer fluid volume (Figure); the inner fluid volume was associated significantly with large macular holes and the postoperative vision in contrast to the outer fluid volume, which was not; and the inner fluid volume may represent dysfunction of the Mueller cells and a degenerative change associated with more advanced macular holes.