Vitreous opacities causing artifacts in optical coherence tomography angiography.

Ocular coherence tomography angiography (OCTA) is a noninvasive imaging modality to image chorioretinal vasculature. The quality of images acquired by OCTA can be compromised by artifacts. Various artifacts include projection, motion, blink and segmentation artifact.[1] We aim to describe artifacts caused by vitreous opacities.

Case Reports

Case 1

A 51-year-old diabetic visited us for diabetic retinopathy screening. Left eye fundus examination was limited due to asteroid hyalosis (AH) [Fig. 1a]. Optical coherence tomography (OCT) of left eye demonstrated asteroid bodies with posterior vitreous detachment (PVD) [Fig. 1b]. Left eye OCTA revealed multiple black areas in all slabs resembling capillary drop out areas [Fig. 1c–e]. The black dot is seen in Fig. 1c is over the blood vessel which continues beyond that point, indicating that the vessel is patent.

Figure 1

(a) Color fundus photo of left eye showing dense asteroid hyalosis obscuring the fundus view. (b) Ocular coherence tomography of left eye demonstrating asteroid bodies with posterior vitreous detachment. (c) Left eye Ocular coherence tomography angiography (superficial retinal slab) showing multiple black areas resembling capillary drop out areas. Yellow arrow shows that, the black area which can be confused with capillary drop out is over the blood vessel which, is seen to continue beyond that point indicating, that the vessel is patent. (d) shadow artifacts in deep retinal slab. (e) shadow artifacts in choriocapillary slab

Case 2

A 46-year-old presented with floaters in the right eye. Fundus examination of the right eye was suggestive of branch retinal vein occlusion. An opening in the posterior hyaloid was noted superotemporal to the fovea [Fig. 2a]. OCT of the right eye showed a PVD with an opening [Fig. 2b]. OCTA showed an oval ring corresponding to opening in the posterior hyaloid in all slabs [Fig. 2c–e].

Figure 2

Color photograph showing a ring like opening in the posterior hyaloid (white arrows) at the macula. (b) Ocular coherence tomography in the right eye showed posterior vitreous detachment. White arrows indicate opening in the posterior hyaloid. (c) right eye Ocular coherence tomography angiography at superficial retinal slab illustrating an oval shaped shadow corresponding to the location of the oval shaped opening in the posterior hyaloid. Areas of capillary drop out are seen superotemporal to the fovea with multiple microanuerysms. (d) Ring like artifact in deep retinal slab. (e) Ring like artifact in choriocapillary slab

Discussion

AH is a degenerative disorder of the vitreous. Smith reported that 27%–70% of patients with AH are diabetic.[2] AH renders visualization of the microvascular abnormalities challenging. In such scenarios, fluorescein angiography (FA) helps us visualize retinal vasculature better.[3] The barrier filter in fundus camera used to acquire FA absorbs the scattered blue light and allows only green light, making visualization possible.[4] Meticulous evaluation of OCTA in eyes with vitreous opacity is crucial and shadows caused by vitreous opacities should be differentiated from capillary dropout.

Conclusion

Vitreous opacities such as AH and PVD can cause artifacts on OCTA. FA remains the investigation of choice in cases with AH.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.