Spark ImageWise 18 – Retina

Structural assessment of branch retinal vein occlusion using imaging techniques

Dr. Shashank Somani, Dr. Sarang Lambat, Dr. Prabhat Nangia, Dr. Vinay Nangia 
Suraj Eye Institute, 559 New Colony, Nagpur 

Case Description
 A female, 51 years of age, presented with   diminution of vision in right eye since 3 months. Her best corrected visual acuity was counting fingers at 3 meters, N36 in right eye (RE) and 6/6, N6 in left eye (LE). Anterior segment examination was normal. Intraocular pressure recorded by Goldmann applanation tonometer was 11 mmHg in RE and 13 mmHg in LE.

Figure 1: Fundus photograph of right eye with healthy disc and vertical cup disc ratio of 0.4:1. The veins along the superotemporal quadrant are dilated and tortuous (Yellow arrow). There are multiple superficial intra-retinal haemorrhages (blue arrow), and few cotton-wool spots (black arrow) along the superotemporal quadrant of the macula. Collateral vessels are seen temporal to the fovea. (green arrow)
Figure 2: Fundus photograph of left eye with healthy disc and vertical cup disc ratio of 0.3:1. Macula, blood vessels, and periphery are normal.
Figure 3a: SDOCT horizontal line scan through fovea of right eye shows multiple hypo-reflective cystic spaces in the inner retinal layers (red arrow), diffuse hypo-reflective space in outer nuclear layer (yellow arrow) distorting the normal foveal contour, suggestive of cystoid and spongy macular edema involving the fovea. Loss of external limiting membrane and ellipsoid zone can be visualised ( green arrow) along with an adjacent  localised patch of hyper reflectivity of the RPE – Bruch’s membrane complex (blue arrow). 
Figure 3b:
SDOCT horizontal macular line scan left eye with normal foveal contour. 
Figure 4: FFA of RE, late arteriovenous phase showing blocked fluorescence (yellow arrow) in the areas of haemorrhages seen on the colour fundus photograph. There is also presence of tortuous collateral vessels and small vascular abnormalities, temporal to the fovea (green arrow). The foveal avascular zone is distorted and its margins are not clearly delineated. (Red  arrow)
Figure 5:
FFA of LE, recirculation phase with normal vascular architecture.
Figure 6: Optical coherence tomography – angiography scan of RE centred at macula with a slab of superficial capillary plexus (SCP) showing capillary dropout (red arrows) and increased vessel signal and tortousity in the foveal and parafoveal region (green arrows) suggestive of collaterals. The foveal Avascular zone was measured using the inbuilt tool and was found to be 0.65mm2 in area with a significantly narrowed horizontal diameter and an increased vertical width.
Figure 7:
Optical coherence tomography Angiography scan of LE centred at macula with a slab of superficial capillary plexus showing a normal foveal avascular zone which was found to be 0.58mm2 in area.
Figure 8: Optical coherence tomography Angiography scan of RE centred at macula with a slab of deep capillary plexus (DCP) showing capillary dropout (red arrows) and increased vessel signal along the temporal and  inferotemporal quadrant possibly due to enhanced flow in these draining channels along the collaterals (green arrows). The foveal Avascular zone was measured using the inbuilt tool and was found to be 1.32mm2
Figure 9:
Optical coherence tomography Angiography scan of LE centred at macula with a slab of deep capillary plexus showing normal appearance and an oval Foveal avascular zone which was found to be 0.54mm2

The patient was advised Anti-VEGF injection for the right eye. On 1 month follow up the macular edema was reduced and the BCVA was 6/60 in the right eye and patient is under follow up. 

Discussion
Optical coherence tomography angiography (OCTA) is a new imaging modality that allows noninvasive visualisation of retinal blood flow without use of exogenous dyes. The layer-specific imaging capabilities of OCTA have the potential to simultaneously visualise both superficial and deep retinal capillaries by segmentation of each layer. In the normal human retina, the main branches of the central retinal artery and the central retinal vein lie horizontally within the retinal nerve fiber layer (RNFL). The arterial branches then supply a total of four (two superficial and two deep) layers of the capillary networks in the perifoveal region, that is, (1) the RNFL, (2) the retinal ganglion cell layer (GCL) and superficial portion of IPL, (3) the deep portion of IPL and superficial portion of inner nuclear layer (INL), and (4) the deep portion of INL. The SCP in the OCTA represents the retinal arterioles, venules, and capillary networks in the first through third of these. The DCP in the OCTA indicates the capillary networks at the deep portion of inner nuclear layer (INL) which seem to be important for nutritional and oxygen support of the synaptic connections responsible for transmission of visual signals. Hypo-perfusion in the DCP may cause acute nutritional deficiency in the synaptic connections, resulting in decreased VA.

In this case, macular OCT showed presence of significant edema and fluid filled spaces in the inner and outer retinal layers  and photoreceptor loss in the fovea. On FFA there is a very small FAZ which was due to the presence of collaterals invading the FAZ. These collaterals were also present in the superficial and the deep capillary plexus of the OCT angiography. On SCP the size of FAZ in right eye was marginally larger than the that of left eye, however it was distorted, vertically elongated in shape, with reduced horizontal width. Whereas the size of FAZ on DCP was significantly larger in right eye as compared to the left eye. The difference in the area of right eye and left eye FAZ in SCP was 0.07mm and that on the DCP was 0.78mm2. The exact significance of a relatively smaller FAZ in the SCP versus that in the DCP is not well understood. It may be noted that vascular changes may be more signifiant in the DCP and or that the collateral vascular response may be more aggressive in the SCP. At the same time, we also keep in mind that sections of the SCP and DCP on OCTA in such patients pass through the fluid filled spaces that constitute the macular oedema  and play a role in distorting the FAZ on OCTA. Findings on OCTA give a greater understanding of the vascular changes in venous occlusion. The OCT gives us a detailed view of the structural changes and enables us to plan further management and follow up of  these subjects. 

ReadWise

  1. Wakabayashi T, Sato T, Hara-Ueno C, Fukushima Y, Sayanagi K, Shiraki N, Sawa M, Ikuno Y, Sakaguchi H, Nishida K. Retinal microvasculature and visual acuity in eyes with branch retinal vein occlusion: imaging analysis by optical coherence tomography angiography. Investigative ophthalmology & visual science. 2017 Apr 1;58(4):2087-94. doi:https://doi.org/10.1167/iovs.16-21208
  2. Tsai G, Banaee T, Conti FF, Singh RP. Optical coherence tomography angiography in eyes with retinal vein occlusion. Journal of ophthalmic & vision research. 2018 Jul;13(3):315. doi: 10.4103/jovr.jovr_264_17
  3. Kadomoto S, Muraoka Y, Ooto S, Miwa Y, Iida Y, Suzuma K, Murakami T, Ghashut R, Tsujikawa A, Yoshimura N. Evaluation of macular ischemia in eyes with branch retinal vein occlusion: an optical coherence tomography angiography study. Retina. 2018 Feb 1;38(2):272-82. doi: 10.1097/IAE.0000000000001541

Dr. Sarang Lambat
MS, FRF
Consultant
Vitreoretinal services
Suraj Eye Institute
Nagpur
Email – education@surajeye.org

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