Intracameral recombinant tissue plasminogen activator (r-tPA) for refractory toxic anterior segment syndrome

Toxic anterior segment syndrome (TASS): A review and update

Toxic anterior segment syndrome (TASS) is an acute, sterile, postoperative inflammatory reaction of the anterior segment without vitreous involvement, following an uncomplicated and uneventful ocular surgery, having broad and multiple etiologies. The symptoms of decreased visual acuity and ocular discomfort generally occur within the first 12-48 h after intraocular surgery. The clinical signs include prominent limbus-to-limbus corneal edema, anterior chamber cells, aqueous flare, fibrinous inflammation, and/or keratic precipitates. There can be sight-threatening complications of TASS, such as permanent corneal decompensation, intractable glaucoma, and cystoid macular edema. The causes of TASS are emerging and being reported, so are the newer treatment options for managing the inflammation and its complications. Prevention guidelines for TASS are being updated, and a traceability system for surgical instruments and intraocular fluids used during the surgery is being perpetually developed. It is important to recognize TASS and start treatment on an immediate effect. Hereby, we review the literature on TASS, emphasizing its etiology, pathophysiology, management, prognosis, complications, and the importance of prevention as well as prompt recognition.

Utility of Anterior Segment OCT in the Management of Uveitic Cataract Surgery: A Fibrinoid Syndrome Case Treated with rtPA

PURPOSE

To highlight the importance of swept-source anterior segment optical coherence tomography (SS-ASOCT) in the peri-surgical management of cataract in uveitis. To describe a case of fibrinoid syndrome in uveitis treated with recombinant tissue plasminogen activator (rtPA).

METHODS

SS-ASOCT was performed at each follow-up before and after cataract surgery to assess anterior chamber inflammation and assist the clinical management of the patient.

RESULTS

A patient with idiopathic autoimmune uveitis was scheduled for cataract surgery. SS-ASOCT allowed to correctly plan the surgery timing. The patient developed a severe fibrinoid syndrome. Postsurgical SS-ASOCT allowed to distinguish between anterior chamber cells and fibrin thus guiding the timing for rtPA intracameral injection. Visual acuity improved from 20/400 the day after the surgery to 20/40.

CONCLUSION

SS-ASOCT allowed a precise assessment of the inflammatory components (cellular vs fibrinoid) after cataract surgery. Intracameral rtPA was safe and effective in the treatment fibrinoid syndrome in uveitis.

Use of Intracameral Tissue Plasminogen Activator During Uveitic Cataract Surgery

PURPOSE

To report the outcomes of intracameral tissue plasminogen activator (tPA) use during uveitic cataract surgery.

DESIGN

Retrospective case series from a single United States tertiary center of 36 eyes from 31 consecutive patients with established uveitis who received intraoperative intracameral tPA during cataract surgery between 2016 and 2020.

RESULTS

Mean visual acuity (VA) improved from logMAR 1.0 ± 0.7 preoperatively to logMAR 0.7 ± 0.8 by POM12. VA improved from baseline postoperatively (POM1 p = 0.0002, POM6 p = 0.006 and POM12 p = 0.007). Minimal to no anterior chamber inflammation was achieved in 47.2% of the eyes by POW1 and 80.0% of the eyes by POM1. Mean clock-hours of posterior synechiae improved from 8.2 ± 3.8 preoperatively to 0.1 ± 0.6 by POM12. Six eyes developed hyphema and/or vitreous hemorrhage, four of which resolved spontaneously.

CONCLUSIONS

Adjunctive intracameral tPA during uveitic cataract surgery improves VA and intraocular inflammation, but risks postoperative hemorrhage. Intraoperative tPA as adjunctive anti-inflammatory therapy warrants randomized prospective studies.

Intravitreal Tissue Plasminogen Activator Injection for the Treatment of Proliferative Vitreoretinopathy in a Rabbit Model

INTRODUCTION

The purpose of this study was to evaluate the effect of intravitreal injection of tissue plasminogen activator (tPA) on proliferative vitreoretinopathy (PVR).

METHODS

PVR was induced in a rabbit model by intraocular injection of dispase (0.05 U/0.1 mL). Progression of PVR was followed by indirect ophthalmic examination. Following 6 weeks, 5 animals received intravitreal injection of 25 µg/0.1 mL tPA and four were injected with balanced salt solution (BSS). Animals were euthanized at 48 h following tPA/BSS injection, and eyes were enucleated for histological evaluation and staining with α-smooth muscle actin (αSMA) and Sirius Red.

RESULTS

Following tPA injection, one eye had a reduction in PVR from grade 2 to 1 and three eyes remained stable. Following BSS, PVR grade was unchanged in three eyes. In one eye in each group, the severity of PVR could not be assessed due to limited view. Staining with αSMA showed reduced presence of fibroblasts in eyes injected with tPA compared with those injected with BSS. Collagen type I and III, demonstrated by Sirius Red staining, was reduced in the tPA group in comparison with controls.

CONCLUSION

Our results suggest that intravitreally injected tPA may show an inhibitory effect on PVR progression. Further exploration in clinical trials is desired.

Intracameral r-tPA for the management of severe fibrinous reactions in TASS after cataract surgery

BACKGROUND

To describe the use of intracameral recombinant tissue plasminogen activator (r-tPA) in the treatment of severe fibrinous reactions in toxic anterior segment syndrome (TASS) after cataract surgery.

METHODS

A case series of 59 eyes of 59 patients with severe fibrinous anterior chamber reaction following cataract surgery who received intracameral r-tPA (25 µg/0.1 ml). The main outcome measures after intracameral r-tPA were the incidence of complete fibrinolysis, time of maximal effect, visual acuity, and complications.

RESULTS

Severe fibrinous reactions appeared 11.5 ± 5.3 days after cataract surgery. Fibrinolysis was observed 2.33 ± 2.70 days after rtPA use and 36 eyes (61%) exhibited resolution of the fibrin by the end of the first day following injection (p < 0.001). Transient corneal edema observed at 1-day after injection was the only complication reported during the injection of r-tPA or at follow-up. Eight eyes (13.6%) required a second r-tPA injection. Best-corrected visual acuity improved from 0.88 ± 0.67 logMAR units before rtPA injection to 0.48 ± 0.49 logMAR units at 1-month (p < 0.001).

CONCLUSIONS

The application of r-tPA was a quick and efficacious therapeutic approach for the management of severe fibrinous reactions in TASS after cataract surgery. In a clinical setting, intracameral r-tPA may be useful when rapid visual recovery is needed.

Successful pediatric DMEK facilitated by intracameral tissue plasminogen activator to mitigate anterior chamber fibrin reaction

Purpose

To report a case of a successful Descemet's membrane endothelial keratoplasty (DMEK) facilitated by the use of intracameral tissue plasminogen activator (tPA) in a 4-year old with posterior polymorphous corneal dystrophy (PPCD).

Observations

A 4-year old male was referred for bilateral corneal haze and blurry vision. Patient's exam and genetic testing were consistent with a diagnosis of PPCD. Patient was successfully treated with DMEK augmented by the use of intracameral tPA intraoperatively to combat the anterior chamber fibrin formation that can occur in DMEK.

Conclusions

To our knowledge, this case represents the youngest reported successful DMEK procedure and the first case describing the use of intracameral tPA intraoperatively to attenuate the anterior chamber fibrin formation that can occur in DMEK.

Intracameral tenecteplase during phacoemulsification in rabbits: clinical assessment of the anterior segment and biochemical analysis of the aqueous humor

Abstract To evaluate the use of tenecteplase in transoperative phacoemulsification in healthy rabbits, the study was carried out with fifteen New Zealand rabbits, divided into three groups: control group (CG), untreated group (UG) and treated group (TG). UG and TG were operated by phacoemulsification and TG received 50 µg / 0.3 mL of intracameral tenecteplase. The postoperative evaluations were 24 h, 72 h, 7 days, 15 days and 21 days. In TP21 the animals were submitted to euthanasia and aqueous humor samples were collected. No significant differences were observed in the clinical evaluations between CG and TG in relation to incidence rates of intraocular pressure (IOP), corneal edema, fibrin deposits, hyphema, aqueous flare and synechia. In the physicochemical evaluation of the aqueous humor, there were no significant differences between the three groups in relation to pH values and concentrations of chloride ions. The aqueous humor density values were statistically different between CG and the other groups. In the histological evaluation, there were no significant differences between the groups. The use of tenecteplase in transoperative phacoemulsification in rabbits did not present significant differences in terms of clinical, physicochemical and histological parameters.

Evaluation of D-dimer levels in aqueous humor of rabbit eyes with and without induced intraocular fibrin and fibrinolytic treatment

OBJECTIVE

To analyze D-dimer concentrations in aqueous humor (AH) of rabbit eyes under physiological conditions, after induction of fibrin clots, and following fibrinolytic therapy.

ANIMALS STUDIED

Prospective study measuring D-dimers in aqueous humor of rabbit eyes with induced fibrin clots (n = 44).

PROCEDURES

Rabbits were purchased in two groups, which led to two temporally separated experimentation groups. Different treatment protocols were compared for their efficacy in fibrin reduction (slit-lamp examination, high-resolution ultrasound). AH was taken from left eyes before clot induction (baseline, day 1), 24 hours later after clot establishment/prior to drug administration (post-induction, day 2) and 48 hours after clot induction (post-treatment, day 3). An enzyme-linked immunosorbent assay (ELISA) was performed to measure intraocular D-dimer concentrations RESULTS: D-dimer concentrations were measurable in all samples. There were no differences in D-dimer levels across time points or treatments within the arrival groups. However, a significant difference in mean D-dimer levels was observed between the two arrival groups (group 1:3.1 µg/mL; group 2:6.1 µg/mL; P < .0001), which made a direct comparison of treatment groups impossible. Clinically, all eyes displayed fibrin clots in the anterior chamber and different treatment types led to significant differences in clot resolution (clot size reduction after intracameral treatment: 98%, topical treatment: 60%, no treatment: 40%).

CONCLUSION

D-dimers were identified in all AH samples of rabbits with large variability between samples. D-dimer levels were neither predictive for differences in induced fibrin formation nor for drug efficacy.

Effect of immediate postoperative intracameral tissue plasminogen activator (tPA) on anterior chamber fibrin formation in dogs undergoing phacoemulsification

OBJECTIVE

To evaluate the postoperative effect of intracameral tPA (alteplase; Activase®, Genentech, San Francisco, CA), administered at immediate conclusion of phacoemulsification, on anterior chamber fibrin formation in dogs.

PROCEDURES

Forty-one dogs (82 eyes) undergoing bilateral phacoemulsification received 25 μg/0.1 mL intracameral tPA in one eye and 0.1 mL unmedicated aqueous vehicle in the contralateral eye immediately after corneal incision closure. Intraocular pressure (IOP) was measured, and severity of anterior chamber fibrin formation, aqueous flare, pigment precipitates on the intraocular lens (IOL) implant, posterior capsular opacification (PCO), and corneal edema were graded at approximately 1 week, 2-3 weeks, 4-6 weeks, 8-12 weeks, and greater than 3 months postoperatively.

RESULTS

Anterior chamber fibrin developed postoperatively in 68.3% of dogs (28/41) and 50% of eyes (41/82). In tPA-treated eyes, 53.7% (22/41) developed fibrin compared to 46.3% of control eyes (19/41). Some degree of postoperative ocular hypertension (POH) occurred in 53.7% of dogs (22/41) and 36.5% of eyes (30/82). In tPA-treated eyes, 34.1% (14/41) experienced POH compared to 39% of control eyes (16/41). Additional intracameral tPA injection was later required in 29.3% of both tPA-treated (12/41) and control eyes (12/41).

CONCLUSIONS

Administration of intracameral tPA at immediate conclusion of canine phacoemulsification had no clinically observable effect on anterior chamber fibrin incidence at any time point. tPA-treated eyes showed no prophylaxis against POH or secondary glaucoma compared to control eyes and received late postoperative tPA injections at the same frequency as control eyes.

Toxic anterior segment syndrome: A review

Toxic anterior segment syndrome is a surgical complication characterized by a noninfectious anterior chamber inflammatory reaction having multiple etiologies. The clinical signs (prominent limbus-to-limbus corneal edema, anterior chamber inflammation) and symptoms (decreased visual acuity, discomfort) generally occur within the first 12-48 hours after intraocular surgery. Most patients achieve good clinical and visual outcomes when there is a prompt clinical diagnosis and adequate treatment. We review the literature on toxic anterior segment syndrome, emphasizing its etiology, pathophysiology, and clinical and surgical management, as well as prognosis and sequelae. Our goal is to reduce the frequency of toxic anterior segment syndrome by highlighting the importance of prevention, early recognition, and distinguishing toxic anterior segment syndrome from infectious endophthalmitis.

Toxic anterior segment syndrome-an updated review

Background

Toxic anterior segment syndrome (TASS) can be a rare complication of anterior segment surgery. Here we reviewed the most recent advances in the understanding of TASS.

Methods

English articles related to TASS were retrieved from “PubMed” using the following keywords; “toxic anterior segment syndrome” or “TASS”. The authors of this paper reviewed all the retrieved literature and critical findings were summarized.

Results

The onset of TASS can vary from hours to months. The clinical manifestations are also variable. The causes of TASS are broad and continue to expand and could not be elucidated in over half of the reported cases. Prompt and thorough investigation to explore the causes of TASS is critical. Surgeons should be fully aware and updated regarding possible etiologies and make ceaseless efforts to prevent TASS. This effort begins with establishing TASS prevention protocols and regularly training surgical staff. Proper cleaning of surgical instruments is critical and should follow the guidelines set by The American Society of Cataract and Refractive Surgery TASS Task Force. When TASS occurs, sharing information with other ophthalmologists and reporting new causes is crucial for the prevention of outbreaks.

Conclusions

Anterior segment surgeons should be reminded that TASS is mostly preventable by the establishment of TASS prevention protocols, regular surgical staff training and thorough adherence to recommendations for cleaning and sterilizing intraocular surgical instruments.

Efficient increase of the novel recombinant human plasminogen activator expression level and stability through the use of homozygote transgenic rabbits

Expression efficacy of recombinant protein in current expression systems is generally low. Therefore, the expression levels of recombinant proteins in the breast milk of transgenic animals are typically low. In view of this, the present study aimed to construct homozygous transgenic rabbits with a high expression level of recombinant human plasminogen activator (rhPA) during the entire lactation period. Homozygous transgenic rabbits were obtained using an effective rhPA mammary‑specific expression vector PCL25/rhPA. The expression level and thrombolytic ability of rhPA in the milk of both homozygous and hemizygous rabbits were detected by enzyme‑linked immunosorbent and fibrin agarose plate assays. It was observed that the expression of rhPA was constant during the entire lactation period in homozygous rabbits, while the expression of rhPA declined slowly in hemizygote rhPA transgenic rabbits during the lactation period. In addition, the expression of rhPA in homozygous transgenic rabbit was ~950 µg/ml, which was markedly higher in comparison with that in hemizygote rabbits. Furthermore, increased gene copy number was observed to increase the expression level of rhPA at the same integration vector.

High-level expression of a novel recombinant human plasminogen activator (rhPA) in the milk of transgenic rabbits and its thrombolytic bioactivity in vitro

The human tissue-type plasminogen activator (tPA) is a key kinase of fibrinolysis that plays an important role in dissolving fibrin clots to promote thrombolysis. The recombinant human plasminogen activator (rhPA) has more thrombolytic advantages than the wild type tPA. To increase the half-life and thrombolytic activity of tPA, a mutant containing only the essential K2 fibrin-binding and P activating plasminogen domains of the wild type tPA was cloned. This fragment was then inserted into goat β-casein regulatory sequences. Then, a mammary gland-specific expression vector, PCL25/rhPA, was constructed, and the transgenic rabbits were generated. In this study, 18 live transgenic founders (12♀, 6♂) were generated using pronuclear microinjection. Six transgenic rabbits were obtained, and the expression levels of rhPA in the milk had a range of 15.2-630 µg/ml. A fibrin agarose plate assay of rhPA showed that it had strong thrombolytic bioactivity in vitro, and the highest specific activity was >360 (360 times more than that of alteplase). The results indicated that the rhPA containing only the K2 and P domains is efficiently expressed with higher thrombolytic bioactivity in the milk of transgenic rabbits. Our study also demonstrated a new method for the large-scale production of clinically relevant recombinant pharmaceutical proteins in the mammary glands of transgenic rabbits.