Patient characteristics

Our cohort included 76 eyes and 58 patients who underwent 0.19-mg fluocinolone acetonide (FAi) implantation. In total, 44 patients (52 eyes) completed the 12-month observation period. Detailed baseline patient characteristics are depicted in Table 1. In total, 67 eyes (88.2%) had a history of periorbital or intravitreal corticosteroid injections. In our cohort 52 eyes (68.4%) received steroids for remission induction before FAi: either an intravitreal 0.7 mg dexamethasone implant (n = 35; 46.1%) or a periorbital injection of 40 mg triamcinolone acetonide (n = 17; 22.4%). We observed a significant reduction in CRT, intraocular inflammation (SUN grade), and a consecutive increase in BCVA upon remission induction therapy (Supplemental Fig. 1). In total, 24 eyes (31.6%) did not receive any induction therapy. Table 2 summarizes FAi patients’ characteristics with and without remission induction therapy within the 12-month observation period.

Table 1 Baseline patient characteristicsTable 2 Comparison of patients with and without remission induction therapy before 0.19-mg fluocinolone acetonide implantationBest-corrected visual acuity outcome

Overall, the BCVA remained stable upon FAi implantation during the 12-month observation period (63.21 vs. 62.95 letters, mean difference 0.26 letters, 95% CI: − 6.31 to 6.84, p > 0.9) (Fig. 2A). The initial BCVA improvement within the first six months (63.21 vs. 68.78 letters, mean difference − 5.57 letters, 95% CI: 10.3 to − 0.84, p = 0.014) was not retained. The baseline BCVA differed in phakic and pseudophakic eyes (70.3 vs. 64.89 letters, difference − 5.41, 95% CI: − 17.21 to 6.39, p = 0.72). However, no significant BCVA change was observed within both groups over time (12 months compared to baseline in phakic eyes, 70.3 vs. 75.29 letters, difference − 4.99, 95% CI: − 14.71 to 4.72, p = 0.79; pseudophakic eyes, 64.14 vs. 63.18; difference 0.96, 95% CI: − 4.94 to 6.86, p > 0.9) (Fig. 2B). Both remission induction therapy and additional systemic therapy did not significantly affect BCVA outcome after 12 months (64.73 vs. 64.49 letters, difference 0.24, 95% CI: − 15.66 to 16.13, p > 0.9; 68.59 vs. 63.83, difference 4.77, 95% CI: − 6.69 to 16.23, p = 0.81) (Fig. 4A; Table 2).

Fig. 2

Mean change in best-corrected visual acuity (BCVA) after FAi implantation. (A) Mean BCVA change of all eyes included. (B) Comparison of mean BCVA change of pseudophakic and phakic eyes. *p < 0.05

Macular edema

The mean central retinal thickness (CRT) significantly improved after FAi at three months compared to baseline (362.7 vs. 308.7 μm, difference 54.01 μm, 95% CI: 8.86 to 99.16, p = 0.01) and remained stable throughout the observation period (12 months compared to baseline, 362.7 vs. 309.1, difference 53.57 μm, 95% CI: 1.55 to 105.6, p = 0.04) (Fig. 3A). The change in CRT (ΔCT = baseline CRT – CRT after 3 months) did not significantly correlate with BCVA change (ΔBCVA = baseline BCVA – BCVA after 3 months; r =  − 0.099, p = 0.5) (Supplemental Fig. 2). Baseline CRT did not differ in FAi patients with or without remission induction therapy (364.5 vs 361.9 μm, difference 2.62 μm, 95% CI: − 85.79 to 91.02, p > 0.9). After 9 months, CRT was significantly reduced in patients without remission induction therapy compared to those with remission induction therapy (262.5 vs. 341.9 μm, difference − 79.4 μm, 95% CI: − 130 to − 28.75, p = 0.0007); however, this effect was not retained up to month 12 (278.8 vs. 322.9 μm, difference − 44.14 μm, 95% CI: − 99.36 to 11.08, p = 0.17) (Fig. 4B). No significant CRT difference in patients with additional systemic anti-inflammatory therapy was observed after 12 months (307.9 vs. 293.3 μm, difference 14.59 μm, 95% CI: − 55.51 to 84.68, p = 0.98).

Fig. 3

Control of inflammation after FAi implantation. (A) Mean change in central retinal thickness (CRT). (B) Overall intraocular inflammation according to SUN grading. *p < 0.05, **p < 0.01

Fig. 4

Comparison of patients with and without remission induction therapy before FAiimplantation. (A) Mean change of BCVA. (B) Mean change of CRT. ***p < 0.001

Inflammation

The overall intraocular inflammation assessed by SUN score initially improved after FAi at three months (0.83 vs. 0.18, difference 0.65, 95% CI: 0.26 to 1.04, p = 0.0001) (Fig. 3B) and remained stable until nine months of follow-up (0.83 vs. 0.3, difference 0.53, 95% CI: 0.11 to 0.95, p = 0.007). However, a slight, but not significant increase was observed after 12 months (0.83 vs. 0.55, difference 0.28, 95% CI: − 0.23 to 0.79, p = 0.53). Neither remission induction nor additional systemic therapy significantly affected intraocular inflammation (0.47 vs. 0.59, difference − 0.12, 95% CI: − 0.78 to 0.55, p = 0.9; 0.54 vs. 0.57, difference − 0.03, 95% CI: − 0.62 to 0.55, p > 0.9). It is noteworthy that intraocular inflammation was not the justifying indication for FAi in our cohort.

Adjunctive immunosuppressive treatment

Overall, 36 eyes (47.4%) received adjunctive immunosuppressive treatment at baseline. In seven eyes (19.4% of all eyes that received adjunctive treatment and five patients in total), systemic adjunctive therapy was either stopped or reduced within the 12-month observation period. In three eyes, systemic adjunctive treatment was escalated. Some patients suffered from a systemic autoimmune disease requiring immunosuppressive therapy. Therefore, treatment was adjusted according not only to the ocular disease, but also to systemic activity.

Recurrence rate

Within the 12-month observation period, seven recurrences (9.2%) with the need for subsequent treatment either with a 0.7 mg dexamethasone intravitreal implant (n = 6) or periorbital 40 mg triamcinolone acetonide were recorded (n = 1). Two eyes relapsed within three months after the implantation of FAi, suggesting that the initial disease activity exceeded the implant’s anti-inflammatory effect. Notably, recurrences were only reported in eyes that had undergone previous remission induction therapy (Table 2).

Intraocular pressure and cataract formation

IOP did not significantly increase upon FAi treatment after 12 months; however, a tendency was observed (13.68 vs. 15.6 mmHg, difference − 1.92, 95% CI: − 3.85 to 0.004, p = 0.0507). An IOP rise of > 25 mmHg occurred in three eyes. Filtering procedures were performed in two eyes within the 12-month observation period (2.6%). IOP-lowering medication was administered in 26.3% of all eyes at the time of FAi implantation, and this increased to 31.6% after 12 months. The mean number of IOP-lowering medications slightly increased from 0.5 to 0.6 at baseline and after 12 months, respectively. Cataract surgery was required in 4 of the 20 phakic eyes. One eye underwent cataract surgery shortly after FAi implantation.

Implantation-associated adverse events

Major implantation-associated adverse events included hypotony in seven cases (9.2%), which was reversible in all affected eyes, one vitreous hemorrhage (1.3%), and two anterior chamber dislocations (2.6%). Both affected eyes had a history of vitreoretinal surgery. One patient previously underwent replacement of the intraocular lens (IOL) with an iris-fixated IOL. In one case, FAi was explanted after recurring anterior chamber dislocation.