ME is frequently encountered in patients with uveitis17, 18 and may cause permanent vision loss. The management vary significantly among different centers. Options of local corticosteroids included periocular or intraocular injections of TA and intraocular sustained-release glucocorticoid implants11, 19. Of interest is the POINT trial which compared the effectiveness of 3 treatment modalities of local corticosteroids in UME, in particular periocular injections of 40mg TA (periorbital floor or posterior sub-Tenon’s approach), intraocular injections of 4mg TA and a 0.7 mg dexamethasone intravitreal implant15. The results showed that all treatment groups had clinically meaningful reductions in central subretinal thickness compared with baseline15. However, subconjunctival injections of TA have rarely been reported14-16.
Regarding CMT
In the first month after injection of 20mg TA, 62/71 eyes (87.32%) showed a reduction in CMT with 59/71 eyes (83.09%) by at least 20%, which is very close to the overall response rate (88%) observed in a previous study20 aiming to compare sub-tenon TA, intravitreal TA and intravitreal dexamethasone implants. Other studies, however, revealed lower levels of effectiveness. Bae and colleagues21 reported that 53.1% of the eyes treated with peribulbar injections of 40 mg TA showed reduction in CMT after 1 month. Henry A. Leder et al.22 observed that UME was clinically resolved in 53% and 57% of treated eyes 1 and 3 months respectively after a single posterior-subtenon TA (40mg) injection. Furthermore, CMT reduction was observed only in 23% eyes 2 month after a periocular injections of 40 mg TA11.
Regarding relapse
As presented previously, twenty-two (22/83, 26.51%) eyes underwent relapse of UME within 6 months. Among these eyes, 5 (22.73%), 7 (31.82%) and 10 (45.45%) eyes relapsed less than 2 months, 2 to 3 months, and 3 to 6 months after the injection, respectively. Some cases are worthy of note. In one patient, the first injection resulted in resolution of UME for 6 months, however, but the therapeutic effect of the second injection given 1.5 years later lasted only 2 months. Another patient received 7 injections with good responsiveness observed every time in a 10-year follow up period, and the longest resolution lasted for more than 6 months.
Regarding IOP
An elevated IOP was observed in 21/83 eyes (25.30%) in our study. However, Byun et al.23 reported that 18 eyes (11.3%) required glaucoma medications after a posterior-subtenon injection. Another study reported that 34.9% of the patients after a posterior-subtenon injection had elevated IOPs, and 4.7% of the patients needed trabeculectomy ultimately24.
Anterior subtenon injection of TA was found to be 2.4 times more likely (95% CI, 1.02–5.9) to cause elevated IOPs than posterior subtenon injection25, which could be explained by the notion that a higher aqueous level of TA is associated with a higher incidence of IOP elevation. However, our data showed a similar rate of IOP elevation as compared to posterior subtenon injection. In addition, Elevated IOP was observed mainly (16/21 eyes) within the first 2 months after the injection in our study. However, 5 eyes develop IOP rise later than 2 months with the latest observed up to 15 weeks after the injection. While IOP-lowering eye drops were sufficient for majority of the patients, 7 eyes (7 patients) underwent surgical removal of the subconjunctival TA deposit and IOP returned to normal within 1 month after the surgery.
Subconjunctival hemorrhage is also a well-known but trivial side effect. Other reported side effects16 of subconjunctival TA such as conjunctival ulceration26, ischemia, necrosis27 and infectious scleritis, were not observed in our patients.
From our point of view, subconjunctival injection of TA (20mg) has several advantages over other periocular injections. It is technically an easier procedure and could be safely performed in the outpatient clinic; Even though it may be more likely to cause IOP elevation, topical IOP-lowering agents are usually sufficient to control the IOP, and surgical removal of subconjunctival TA deposits is easy and effective when intractable IOP elevation occurs.
There are some limitations for our study, including inhomogeneity of the included patients, inevitable biases, missing data and the different follow-up intervals among different patients due to the retrospective nature of the study.