Bleb-related Porcine Lymphatic Outflow is Greater from Subconjunctival compared to Subtenon Blebs

Bleb vessel density as a predictive factor for surgical revisions after Preserflo Microshunt implantation

PURPOSE

Bleb failure is a common complication after glaucoma filtration surgery. Different bleb classification schemes incorporating filtration bleb vascularization have been proposed, but the reported correlation with intraocular pressure (IOP) has been variable, possibly because of subjective vascularization grading. The purpose of the present study was to evaluate bleb vascularization after Preserflo Microshunt (PM) implantation using anterior segment OCT-angiography (AS-OCTA) as a biomarker for bleb failure.

METHODS

Twenty-three eyes of twenty-three patients underwent PM implantation. Up to 12 months after surgery PM scleral passage-centred AS-OCTA measurements (PLEX Elite 9000) for bleb-vessel density (BVD) determination were performed and IOP as well as necessity for surgical revisions (needling and open revision) were documented. After multi-step image analysis (region of interest definition, artefact removal, binarization, BVD calculation), the predictive value of early postoperative BVD for surgical revisions was assessed using logistic regression modelling.

RESULTS

Baseline IOP (23.57 ± 7.75 mmHg) decreased significantly to 8.30 ± 2.12, 9.17 ± 2.33 and 11.70 ± 4.40 mmHg after 1, 2 and 4 week(s), and 13.48 ± 5.83, 11.87 ± 4.49, 12.30 ± 6.65, 11.87 ± 3.11 and 13.05 ± 4.12 mmHg after 2, 3, 6, 9 and 12 month(s), respectively (p < 0.001). Nine patients (39%) needed surgical revisions after a median time of 2 months. Bleb vessel densities at 2 and 4 weeks were significantly associated with future surgical revisions upon logistic regression analysis (2 W/4 W likelihood-ratio test p-value: 0.0244/0.0098; 2 W/4 W area under the receiver operating characteristics curve: 0.796/0.909).

CONCLUSION

Filtration bleb vessel density can be determined using AS-OCTA in the early postoperative period and is predictive for bleb failure after PM implantation.

VEGF-C and 5-Fluorouracil Improve Bleb Survival in a Rabbit Glaucoma Surgery Trabeculectomy Model

Purpose

To evaluate VEGF-C-induced lymphoproliferation in conjunction with 5-fluorouracil (5-FU) antimetabolite treatment in a rabbit glaucoma filtration surgery (GFS) model.

Methods

Thirty-two rabbits underwent GFS and were assigned to four groups (n = 8 each) defined by subconjunctival drug treatment: (a) VEGF-C combined with 5-FU, (b) 5-FU, (c) VEGF-C, (d) and control. Bleb survival, bleb measurements, and IOP were evaluated over 30 days. At the end, histology and anterior segment OCT were performed on some eyes. mRNA was isolated from the remaining eyes for RT-PCR evaluation of vessel-specific markers (lymphatics, podoplanin and LYVE-1; and blood vessels, CD31).

Results

Qualitatively and quantitatively, VEGF-C combined with 5-FU resulted in blebs which were posteriorly longer and wider than the other conditions: vs. 5-FU (P = 0.043 for longer, P = 0.046 for wider), vs. VEGF-C (P < 0.001, P < 0.001) and vs. control (P < 0.001, P < 0.001). After 30 days, the VEGF-C combined with 5-FU condition resulted in longer bleb survival compared with 5-FU (P = 0.025), VEGF-C (P < 0.001), and control (P < 0.001). Only the VEGF-C combined with 5-FU condition showed a negative correlation between IOP and time that was statistically significant (r = -0.533; P = 0.034). Anterior segment OCT and histology demonstrated larger blebs for the VEGF-C combined with 5-FU condition. Only conditions including VEGF-C led to increased expression of lymphatic markers (LYVE-1, P < 0.001-0.008 and podoplanin, P = 0.002-0.011). Expression of CD31 was not different between the groups (P = 0.978).

Conclusions

Adding VEGF-C lymphoproliferation to standard antimetabolite treatment improved rabbit GFS success and may suggest a future strategy to improve human GFSs.

Clinical and Optical Coherence Tomography Evidence of Aqueous Humor Flow from the Suprachoroidal Space to Conjunctival Lymphatics

A surgical technique was developed to enhance aqueous humor (AH) flow through the non-trabecular outflow pathway by rerouting it from the anterior chamber (AC) to the suprachoroidal space (SCS) without detaching the ciliary body from the scleral spur. Medium- and long-term surgical outcomes were retrospectively analyzed in a case series of 58 glaucoma patients. At 6, 12, and 24 months, the mean IOP decreased from 27.8 ± 8.3 to 14.9 ± 5.0 mmHg, median 15.0 (25th percentile (p25)13.0; 75th percentile (p75) 18.0) and 15.2 ± 3.3 mmHg, and hypotensive medication use reduced from a median (p25; p75) of 3 (2; 3) to 0 (0; 2), 0 (0; 2), and 0 (0; 1.5), respectively. Intra- and postoperative complications were few and manageable. Following surgery, no bleb formation occurred in any of the cases (as confirmed by optical coherence tomography). Conjunctival lymphatic vessels (CLVs) developed in 50% of eyes (29/58). Clinically, they developed directly from sclera and had no connection to the surgical site. Analysis further showed that the development of CLVs and their longer visibility period had poor prognostic value for IOP control. If the fluid flow from the SCS to CLVs was resistance-free, no CLV development was evident. However, if any resistance existed in the flow, the fluid accumulated in lymphatics, resulting in their engorgement. The proposed technique was safe and effective in decreasing IOP in glaucoma patients by enhancing AH flow from the SCS to CLVs via connecting intrascleral microchannels.