Low-dose intraocular tissue plasminogen activator treatment for traumatic total hyphema, postcataract, and penetrating keratoplasty fibrinous membranes

An Update on Strategies to Deliver Protein and Peptide Drugs to the Eye

In the past few decades, advancements in protein engineering, biotechnology, and structural biochemistry have resulted in the discovery of various techniques that enhanced the production yield of proteins, targetability, circulating half-life, product purity, and functionality of proteins and peptides. As a result, the utilization of proteins and peptides has increased in the treatment of many conditions, including ocular diseases. Ocular delivery of large molecules poses several challenges due to their high molecular weight, hydrophilicity, unstable nature, and poor permeation through cellular and enzymatic barriers. The use of novel strategies for delivering protein and peptides such as glycoengineering, PEGylation, Fc-fusion, chitosan nanoparticles, and liposomes have improved the efficacy, safety, and stability, which consequently expanded the therapeutic potential of proteins. This review article highlights various proteins and peptides that are useful in ocular disorders, challenges in their delivery to the eye, and strategies to enhance ocular bioavailability using novel delivery approaches. In addition, a few futuristic approaches that will assist in the ocular delivery of proteins and peptides were also discussed.

Intraoperative fibrin formation during Descemet membrane endothelial keratoplasty

Purpose

To describe Descemet membrane endothelial keratoplasty (DMEK) cases complicated by spontaneous intraoperative fibrin formation.

Methods

DMEK surgeries performed at two centers using a standardized technique were reviewed retrospectively for the occurrence of intraoperative fibrin formation. Cases were assessed for recipient medical history, donor age, best spectacle-corrected visual acuity (BSCVA), intraoperative unscrolling time, 6-month endothelial cell loss (ECL), and the course of the mate donor cornea.

Results

In this review of 868 cases of standardized DMEK surgery with surgical peripheral iridotomy, 32 eyes of 29 patients (3.7%) were complicated by the formation of intraoperative fibrin formation, including 3 patients that developed fibrin in both eyes. Three of the 32 grafts failed (9.4%). None of the mate corneas transplanted (n = 27) developed complications related to fibrin. The donor age ranged from 51 to 75 years and recipient age ranged from 49 to 82 years (median, 66 years). Unscrolling time ranged from 1 to 105 min (median, 15 min). Nine eyes required one rebubble procedure. No eyes had vision-limiting comorbidities, and the 6-month BSCVA was ≥20/40 in all eyes. Six-month ECL ranged from 19% to 73% (median, 44%).

Conclusions

We conclude that fibrin formation during DMEK surgery is an uncommon but important complication that can make graft manipulation more difficult, and may have deleterious effects on endothelial cell density and graft survival.

Low-dose tissue plasminogen activator in the management of anterior chamber fibrin formation

PURPOSE

To investigate the efficacy of tissue plasminogen activator (tPA) in the treatment of severe fibrinous anterior chamber reactions after intraocular surgery.

SETTING

Ophthalmology Department, AHEPA University Hospital, Thessaloniki, Greece.

METHODS

The study comprised routine surgical and postoperative cases selected in a nonrandomized fashion. Low-dose tPA infusion (0.2 mL of 125 microg/mL) was administered through a side-port in the anterior chamber in 25 patients with recent or long-standing fibrin formation after cataract extraction (n = 13), trabeculectomy (n = 5), combined procedure (n = 5), or penetrating keratoplasty (n = 2). Patients were treated 4 to 25 days postoperatively (mean 7 days).

RESULTS

Fibrin lysis was observed 2 to 12 hours after tPA infusion. No hemorrhage or other complications occurred, and no further treatment was necessary in any patient. Three cases of delayed partial fibrin lysis resolved with intense topical steroid treatment. There were no recurrences over the 3-month follow-up.

CONCLUSIONS

Low-dose tPA was an effective and safe method for the management of anterior chamber fibrin formation. Treatment was well tolerated and gave excellent results with no complications.

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.

Tissue plasminogen activator in the treatment of vitreoretinal diseases

Tissue plasminogen activator (tPA) is a thrombolytic agent that activates plasminogen into plasmin almost exclusively in the presence of fibrin. Intraocular injection of tPA has been proposed for the treatment of vitreoretinal diseases, such as vitreous hemorrhage, postvitrectomy fibrin formation, submacular hemorrhage, retinal vascular occlusive disorders, suprachoroidal hemorrhage and endophthalmitis. Currently, intraocular tPA is only used in the treatment of postvitrectomy fibrin formation and submacular hemorrhage. For other indications, tPA has not been shown to be safe or effective. This article reviews the use of tPA in the treatment of vitreoretinal disorders.

Intraocular recombinant tissue-plasminogen activator fibrinolysis of fibrin formation after cataract surgery in children

PURPOSE

To evaluate the efficacy and safety of intracameral recombinant tissue plasminogen activator (rt-PA) application for fibrinolysis of fibrin formation after cataract surgery in children.

SETTING

Johann Wolfgang Goethe-University, Department of Ophthalmology, Frankfurt am Main, Germany.

METHODS

This study comprised 11 eyes of 10 patients aged 3 to 13 years (mean 7.2 +/- 3.68 [SD]) who developed severe fibrin formation after cataract surgery and IOL implantation despite intensive topical steroid therapy. Under general anesthesia, fibrinolysis was performed with 10 micrograms of rt-PA 7.18 +/- 2.04 days after intraocular surgery. Follow-up included slitlamp examination, tonometry, visual acuity testing, and-ophthalmoscopy. Anterior chamber flare measurements could be performed in 6 eyes.

RESULTS

Complete resolution of fibrin formations occurred in 90% of the patients in these cases, no recurrent fibrinous reaction or adverse effects were noted. In 2 eyes of the same patient with a history of juvenile rheumatoid arthritis and chronic uveitis, fibrin clot dissolution was incomplete. A recurrent fibrinous formation could be observed after 2 and 4 weeks, respectively. A beginning band keratopathy excluding the central and limbal cornea was noted after 6 and 8 weeks, respectively.

CONCLUSION

Intraocular application of rt-PA appears to be a safe and efficacious therapeutic approach in the management of severe fibrinous reactions after pediatric cataract surgery.