Here, we report a rare case of SO following uncomplicated SB surgery accompanied by cryoretinopexy and SRFD. In this regard, it is recommended that SO be taken into consideration in any case of bilateral panuveitis associated with multiple SRD and a history of penetrating ocular surgery.
In several studies, the occurrence of SO has been reported after vitreoretinal surgery.2, 4-6 It is postulated that trauma to the uveal tract in the context of inadvertent perforation, SRFD, or cryotherapy during SB surgery might be related to deliberate uveal antigens, melanin or outer photoreceptor antigens resulting to access to the lymphatic systems of the conjunctival tissue. This process may associated to exciting of delayed hypersensitivity reaction inside the eye.4-6 The mechanism of hypersensitivity in the sympathizing eye may be due to the exposure of the uveal tissue to the conjunctival lymphatic system leading to a cell-mediated immune response.6 This mechanism, owing to more uveal incarceration, can explain the relationship between an increase in the trend of transconjunctival sutureless vitrectomy application and a growth in the incidence of SO following vitreoretinal surgery.6 In our case, SRFD seemingly increased the risk of uveal exposure to conjunctival lymphatic tissue. In a study conducted by Kilmartin et al., it was reported that RRD surgery was the most common procedure associated with the development of SO, with the risk of SO after vitrectomy being as twice as that of external scleral buckling, without any gender predilection.7
The onset of SO symptoms after the operation usually occurs between 3 weeks and 6 months after surgery due to delayed hypersensitivity.8 Regarding the subject in this study, SO was developed 6 weeks later. In a case series study carried out by Ozbek et al.9, three cases of SO incidence occurred following SB; however, two patients had combined vitrectomy with SB. In the aforementioned research, SO occurred only in one case after encircling buckle combined with 360 indirect retinal photocoagulations and SRFD, in contrast to our case that had only one cryoretinopexy spot and one drainage site. In another similar case report by Parvaresh and Falavarjani, SO was found in a case with a history of SB revision after 4 years. In this case, the second surgery was combined with SRFD and cryoretinopexy.10 Nonetheless, in our case, SO happened in the first operation without any surgical history.
In a recent study performed by Tyagi et al., the incidence of SO following vitreoretinal surgery was estimated at 0.038% of all vitrectomy cases, and vice versa, 9% of all cases of SO had vitreoretinal surgery.6 In this research, 75% of cases underwent multiple ocular surgeries before the development of SO.6 Furthermore, the most common anterior segment was non-granulomatous uveitis in 50% of subjects, in contrast to SRD occurring in 62.5% of cases.6 In our case, it was found that anterior segment inflammation was less severe than the posterior segment chorioretinal findings.
Most of the cases presented in studies5-10 had simultaneous SB and vitrectomy, previous trauma, or multiple surgeries. Nevertheless, the subject of our report had no extensive retinal or uveal tissue manipulation and no combined surgery or previous surgery, highlighting the importance of this report. One of the underlying reasons for this susceptibility might be related to the Asian ethnicity and higher prevalence of Vogt-Koyanagi-Harada (VKH) in this region.
One of the most important differential diagnoses of our case is related to VKH which is a common uveitis etiology with similar clinical and imaging findings with SO.1,11 Although sympathizing eye in SO presents clinically with nongranulomatous uveitis at first, it progresses to granulomatous uveitis afterward.8 shows three successive stages: posterior uveitis, anterior segment involvement associated with posterior uveitis, and finally anterior granulomatous uveitis. Both anterior and posterior uveitis are present in SO patients within 2 weeks of disease onset.8 Generally, the main differentiating clue between SO and VKH is the history of prior surgery or trauma in SO. Considering this, in our case, clinical features were more similar to SO than to VKH, as our patient had no systemic sign or symptom attributed to VKH or other systemic diseases causing choroiditis.
The results of SO imaging, based on FAG, revealed multiple hyperfluorescent pinpoints leakages associated with late pooling resembling VKH and hypofluorescent foci during the early phase of angiography. Moreover, the late phase of FAG showed hyperfluorescence similar to acute posterior multifocal placoid pigment epitheliopathy.11 In our case, apparently due to the performance of FAG 4 days after the steroid therapy, hyperfluorscence was less prominent than hypofluorescence that was compatible with the location of granuloma and cellular infiltration. The most common features of ICGA imaging are multiple hypocyanescent spots. In the acute phase of SO, EDI-OCT discloses multiple SRD associated with hyperreflective septa, massive choroidal thickening, and loss of normal choroidal vascular architectures, as well as irregular photoreceptor outer segments similar to what was observed in the acute phase of VKH. The visual outcome is worse in SO as compared with VKH disease.8 Moreover, BCVA was improved in our case due to early diagnosis and prompt, aggressive, and adequate treatment.
In conclusion, the diagnosis of sympathetic ophthalmia should be taken into account in any case of bilateral uveitis or bilateral SRD following scleral buckling with uveal tract violation, such as cryopexy or SRFD.