Our present study highlights the presence of macular changes as a common finding in Eales disease patients presenting to a tertiary care eye hospital. Macular involvement has been previously described in literature. In a study conducted in patients with Eales disease between 1989 and 1997, on SLB and FA, macular involvement was found in 28% of cases. The same authors, in a retrospective analysis, reported macular involvement seen in 32% cases in patients with Eales disease. Another study has reported macular involvement in 35.4% patients [11]. A recent study reported that 58.2% eyes of Eales disease patients had macular involvement as assessed with SD-OCT [8]. Thus, they noted macular changes to be a frequent finding. Macular oedema was the most common (35.4%) followed by ERM (11.4%) and macular thinning (11.4%). Other macular changes reported were hard exudates (6.3%), macular hemorrhages (5%), internal retina or internal limiting membrane folds (3.8%), pre macular hemorrhages (2.5%) and macular holes (1.2%). It has been reported that macula is usually not involved primarily in Eales disease despite extensive peripheral non-perfusion. But when it does get involved, it is termed central Eales disease. In this condition, all the classic mid-peripheral lesions appear at the posterior pole and cause decreased vision in the early stage of the disease, often due to cystoid macular oedema [12]. 51.6% of our patients had macular changes as seen on all modalities together. Many of our patients had classic Eales lesions at macula, thus suggestive of central Eales.
Macular changes in Eales disease have been increasingly reported in recent literature. We feel that one of the reasons for this is the advent of newer modalities like OCT and OCTA which give exact enface and cross-sectional images of the retina.
The age range reported in our study is in accordance with other studies which report the age range to be between 20 to 40 years [8, 12]. The male preponderance (87.1%) as seen in our study, has been reported previously [3].
The comparison of mean BCVA in patients with and without macular involvement diagnosed on FA, OCT and OCTA has scarcely been done before. We noted that the mean BCVA was less in patients with macular changes compared to those without macular changes (p < 0.05). This has been previously reported [8]. Though the p value was significant on all three modalities separately, however, FA missed some macular involvement patients which were picked up on OCT and OCTA. Thus, OCT and OCTA are very sensitive tools for analysis of macular changes in Eales disease and also predictors of visual acuity.
OCTA of Eales disease patients has scarcely been done [10]. In our study, SCP and DCP area was enlarged on OCTA in patients with macular involvement. The deep plexus area and macular involvement was highly significantly correlated (p 0.00). We concluded that the deep capillary plexus enlargement has more association with foveal involvement. The FAZ area calculation in Eales disease patients has never been reported before and since normative database of Indian eyes is not yet available, comparison of our data with normal could not be done. We also noted that RPE and choroid level OCTA scans were normal, thus suggestive of a retinal vascular pathology since it affected only the retinal layers.
It has been demonstrated that OCTA can be a better modality for macular changes, especially in the perifoveal area, than FA, since it distinguishes the different layers of retina and choroid, which cannot be done on FA. It also differentiates the superficial from deep plexus which is not possible on FA. Quantification of capillary plexuses can be done for follow up on OCTA and also visual prognostication. Pooling and leakage which can hamper macular analysis are not seen on OCTA thus making it a good modality for macular analysis. The adverse events related to dye injection are also averted on OCTA. However, periphery evaluation for neovascularization and capillary non-perfusion needs FA since it has a wider field of view [9, 10].
In our study, SLB and IO missed the finding in 8 patients (50%) out of the total patients with macular involvement. In another study [8], 28.3% were noted to have no macular changes based on SLB though they were noted on OCT. FA missed macular findings in 3 (18.8%) patients in our study. OCT and OCTA demonstrated the findings in 100% patients.
We noted that FA was able to identify vasculitis and leakage at macula accurately. However, macular changes in the form of capillary non perfusion, distorted FAZ especially at the deep capillary plexus were missed in 6 out of total 11 patients on FA. One patient with unexplained loss of vision with normal SLB and FA actually showed changes in DCP which explained the visual loss. DCP enlargement disproportionate to SCP enlargement was noted in 8 patients. These patients also had visual loss, thus, highlighting the importance of DCP involvement in Eales disease patients and its effect on their vision (Figs. 4 and 5). There have been previous reports highlighting the changes in DCP selectively in retinal venous occlusion corresponding with vision. It has also been reported that FA can identify SCP changes but not DCP changes separately since it is a two dimensional imaging modality [13,14,15,16,17,18].
We classified our cases according to Eales’ disease classification system [7] and observed that all the groups except stage 1b had macular involvement. Stage 2b had the highest number of macular involvement patients.
On comparison of CMT in eyes with macular involvement versus eyes without macular involvement, CMT of eyes with macular involvement was higher than eyes without it, but this finding was not statistically significant (p 0.09). This is in accordance with other studies [8]. The qualitative macular changes noted on OCT were diffuse retinal thickening, cystoid macular oedema, sub-foveal detachment, epiretinal membrane, retinal thinning, hard exudates at macula, sub-internal limiting membrane bleed and FTMH. Macular oedema as the commonest finding in Eales has been reported recently [7, 8, 11, 19]. Other changes have scarcely been reported, especially FTMH [8, 19]. Premacular haemorrhage and retinal thinning are also rare [8].
Our study included multimodal analysis of macular changes in Eales disease with SLB, IO, FA, OCT and OCTA which has never been done before. This, we feel, is the strength of our study. Our limitation is the small number of patients included. Eales disease being a rare entity and a diagnosis of exclusion, it is difficult to conduct large sample studies on these patients. Some patients in whom media is not clear, the above investigations cannot be conducted. This fact limits the number of study patients. A larger study may be able to establish the results demonstrated by our pilot study.