Intraocular tissue plasminogen activator in a rabbit model of traumatic hyphema

Use of recombinant tissue plasminogen activator (rTPA) for treatment of fibrin in the anterior chamber of the horse

BACKGROUND

Recombinant intracameral tissue plasminogen activator (rTPA) administration can aid clearance of fibrin from the anterior chamber.

MATERIALS AND METHODS

In this retrospective multicentre case series, the effect of intracameral rTPA administration to treat fibrin in the anterior chamber resulting from trauma or inflammatory ocular disease was evaluated. Clinical data from 30 treatments in 29 horses were obtained from medical records from 2003 to 2022. Association between time from onset of clinical signs and time for rTPA treatment to effect was studied with regression analysis.

RESULTS

Twenty-seven horses (93.1%) had no previous history of ophthalmic disease; one had an iridic cyst, and another had equine recurrent uveitis. The majority of cases were related to trauma (79.3%). Median time from the onset of clinical signs to treatment was 12 h (IQR = 4-48 h). rTPA (72% 20 µg; 24% 25 µg; 3.3% 40 µg) was administered once in all but one eye, which was treated twice. Resolution of fibrin was seen in 96.9% (29/30) of treatments. Fibrin accumulation recurred in one case but resolved 14 days after the second treatment. Complications were seen in four treatments (13.3%): moderate pain for 24 h, intracameral debris and mild intracameral haemorrhage in a horse that received 40 µg of tissue plasminogen activator. Recurrence of fibrin accumulation was absent in 96.7% of cases. Median time to effect was 20 min (IQR = 10-45 min). Time for rTPA treatment to effect was not associated with time from fibrin formation (R2 = 0.09; p = 0.11).

CONCLUSION

Intracameral rTPA treatment can be considered at 20-25 µg in 0.1 mL solution to aid resolution of fibrin accumulation.

Resolution of hyphaema following intracameral injection of tenecteplase in a Stock Horse

Intracameral injection of tissue plasminogen activator has been suggested as a means of hastening the clearance of blood from the anterior chamber and reducing the risk of synechia and fibrotic membrane formation in horses with hyphaema. The following report describes a case of ocular trauma in which intracameral injection of tenecteplase (TNK), a new-generation plasminogen activator, resulted in rapid resolution of hyphaema and successful outcome. However, a large dose (1 mg) was administered and may have been associated with retinopathy and keratopathy. TNK may be an effective treatment for equine hyphaema and further controlled clinical or experimental studies are required to determine its efficacy and safety profiles.

Management of traumatic hyphema

Hyphema (blood in the anterior chamber) can occur after blunt or lacerating trauma, after intraocular surgery, spontaneously (e.g., in conditions such as rubeosis iridis, juvenile xanthogranuloma, iris melanoma, myotonic dystrophy, keratouveitis (e.g., herpes zoster), leukemia, hemophilia, von Willebrand disease, and in association with the use of substances that alter platelet or thrombin function (e.g., ethanol, aspirin, warfarin). The purpose of this review is to consider the management of hyphemas that occur after closed globe trauma. Complications of traumatic hyphema include increased intraocular pressure, peripheral anterior synechiae, optic atrophy, corneal bloodstaining, secondary hemorrhage, and accommodative impairment. The reported incidence of secondary anterior chamber hemorrhage, that is, rebleeding, in the setting of traumatic hyphema ranges from 0% to 38%. The risk of secondary hemorrhage may be higher in African-Americans than in whites. Secondary hemorrhage is generally thought to convey a worse visual prognosis, although the outcome may depend more directly on the size of the hyphema and the severity of associated ocular injuries. Some issues involved in managing a patient with hyphema are: use of various medications (e.g., cycloplegics, systemic or topical steroids, antifibrinolytic agents, analgesics, and antiglaucoma medications); the patient's activity level; use of a patch and shield; outpatient vs. inpatient management; and medical vs. surgical management. Special considerations obtain in managing children, patients with hemoglobin S, and patients with hemophilia. It is important to identify and treat associated ocular injuries, which often accompany traumatic hyphema. We consider each of these management issues and refer to the pertinent literature in formulating the following recommendations. We advise routine use of topical cycloplegics and corticosteroids, systemic antifibrinolytic agents or corticosteroids, and a rigid shield. We recommend activity restriction (quiet ambulation) and interdiction of non-steroidal anti-inflammatory agents. If there is no concern regarding compliance (with medication use or activity restrictions), follow-up, or increased risk for complications (e.g., history of sickle cell disease, hemophilia), outpatient management can be offered. Indications for surgical intervention include the presence of corneal blood staining or dangerously increased intraocular pressure despite maximum tolerated medical therapy, among others.

Congenital cataracts and persistent hyaloid vasculature in a llama (Lama glama)

A 9-month-old llama was evaluated for apparent blindness. Bilateral cataracts were diagnosed and cataract surgery was performed on the right eye. At the time of surgery persistent hyperplastic primary vitreous, persistent hyperplastic tunica vasculosa lentis, and a persistent hyaloid artery were observed. Prior to surgery Power Doppler ultrasound revealed a patent tunica vasculosa lentis OS. Despite reports of a poor success rate for llama cataract surgery, through use of careful tissue handling, phacoemulsification, viscoelastic endothelial protectants, anti-inflammatories, and BSS-Plus irrigating solution, vision was successfully restored in both eyes of the llama.

Management of postvitrectomy diabetic vitreous hemorrhage with tissue plasminogen activator (t-PA) and volume homeostatic fluid-fluid exchanger

The incidence of recurrent vitreous hemorrhage of proliferative diabetic retinopathy following posterior vitrectomy ranges from 29% to 75% in reported series. Fluid-gas exchange and vitreous cavity lavage are the popular methods of treating this kind of recurrent hemorrhage. The fluid-gas exchange cannot offer clear vision immediately after the procedure. To improve the function of the classic vitreous cavity lavage, we designed a volume homeostatic fluid-fluid exchanger - Chen's I/A device. Tissue plasminogen activator (t-PA) is a protease that preferentially converts fibrin-bound plasminogen to the active proteolytic enzyme, plasmin. It has been clinically and experimentally proven effective in lysis of postvitrectomy blood clot and fibrin formation. When the blood clot is formed in the vitreous cavity, intravitreal injection of t-PA can convert plasminogen to plasmin and remove the clot. From July 1999 to January 2000, ten eyes of postvitrectomy diabetic vitreous hemorrhage (PDVH) were collected. In each case, 4 days after intravitreal injection (IVI) of t-PA (30 microg), vitreous cavity lavage was performed with Chen's I/A device. Of these cases, 8 eyes (80%) experienced an immediate clearing of the vitreous cavity. Early complications included anterior hyaloid fibrovascular proliferation (2 eyes) and postoperative intraocular pressure elevation (3 eyes). On the basis of the results of this study, our conclusion is that volume homeostatic vitreous cavity lavage, combined with intravitreal injection of t-PA, is an excellent method for treatment of postvitrectomy diabetic vitreous hemorrhage but, in cases of PDVH with iris rubeosis, the advantage of this procedure is uncertain.

The use of tissue plasminogen activator in post-traumatic total hyphaema

BACKGROUND

We wanted to evaluate whether intracameral injection of tissue plasminogen activator (tPA) is useful in managing traumatic hyphaema.

METHODS

Two eyes with total hyphaema after a severe penetrating injury were treated with a single intracameral injection of 25 micrograms of tPA 5 and 14 days after the injury, respectively.

RESULTS

Most of the blood coagulum dissolved within 24 h, and in one of the two eyes the intraocular pressure decreased from 45 to 8 mmHg. The other eye was hypotonic. No re-bleeding or complications related to the use of tPA were noticed.

CONCLUSION

The results in these two cases suggest that tPA is a useful adjunct in managing total hyphaema.

Topical treatment of postvitrectomy fibrin formation with tissue plasminogen activator

Tissue plasminogen activator (tPA) is able to dissolve any fibrin material that forms in the anterior chamber or vitreous humor. This property has been reported by various experimental studies performed in rabbits. The authors demonstrate the tPA eye drops administered to patients with postoperative hyphema, which did not respond to traditional therapy, gave rapid clearance of the clot. Following its topical administration for the first time in patients, the harmless nature of the drug is emphasized as well as its efficacy. This study indicates the promising features of this drug which deserve further investigation.

The use of recombinant tissue plasminogen activator for intracameral fibrinolysis following cataract surgery

In a prospective study performed between June 1992 and March 1994 19 eyes of 19 patients with dense fibrinous pupillary membranes following cataract surgery were treated with intracameral injections of 25 micrograms recombinant tissue plasminogen activator (r-tPA). Injections were performed between the second and twenty-third postoperative day (mean 5.6 +/- 6.9 days). Complete fibrinolysis within one to 4 hours (mean: 3.3 +/- 0.89 hours) was observed in 18 (94.7%) eyes. In one (5.3%) eye fibrinolysis was incomplete despite a second injection. In 2 (10.5%) eyes. No recurrence of a distinct fibrinous membrane was noted which then cleared spontaneously with topical treatment. A small hyphema developed in 2 (10.5%) eyes and intraocular pressure exceeded 25 mmHg in 2 (10.5%) eyes. No increase of keratopathy nor any toxic intraocular side effect of 25 micrograms intracameral r-tPA was observed throughout the study. The intracameral injection of r-tPA clinically proved to safely accelerate the resorption of dense fibrinous membranes following cataract surgery and thus enhance visual recovery minimizing subsequent complications and systemic or subconjunctival anti-inflammatory treatment.

The use of tissue plasminogen activator in postvitrectomy cases

The study concerns 17 eyes which, following vitrectomy, were given an injection of 25 micrograms of tissue plasminogen activator (tPA). Of these 17 cases, ten showed a severe fibrin formation in the anterior chamber, 3 cases showed vitreous hemorrhage (one of them with hyphema), 2 had fibrin formation and cellular proliferation, while in one case tPA was injected at the end of the vitrectomy because of perisilicone proliferation and in one case because of fibrin depositions on the intraocular lens. The tPA was injected into the anterior chamber (10 eyes) or into the vitreous cavity (7 eyes). The follow-up period ranged from 4 to 15 months (mean period 9 1/2 months). Fibrinolysis was noted in the 10 cases with fibrin formation in the anterior chamber. Fibrin dissolution was achieved within 3-4 hours. None of these cases presented a recurrence throughout the follow-up period. Positive results were observed also in the case with perisilicone proliferation. On the contrary in 3 cases with postvitrectomy hemorrhage the hemorrhage persisted unchanged. Also in 2 cases with fibrin formation and cellular proliferation on the anterior and posterior surface of the iris the tPA injection proved ineffective. Both cases developed traction retinal detachment (TRD) due to anterior proliferative vitreoretinopathy (PVR). In the case with fibrin depositions on the intraocular lens the situation remained unchanged. Any complications observed in our case proved to be mild and transitory.