Purpose
To investigate the effects of an intravitreal injection of autologous plasmin enzyme for macular edema associated with a branch retinal vein occlusion (BRVO).
Design
Prospective, interventional case studies.
Methods
Twenty-six eyes of 26 patients (14 men and 12 women) with macular edema resulting from a BRVO were studied. None of the eyes had a posterior vitreous detachment (PVD). The average age at the onset of BRVO was 58.7 ± 6.6 years. The interval between onset of the macular edema and injection of autologous plasmin enzyme was 4.2 months. One international unit of autologous plasmin enzyme in 0.1 mL was injected into each vitreous. The presence of a PVD was evaluated 1 week after the injection, and the visual acuity and macular thickness were measured before and 1 week and 1, 3, 6, and 12 months after the autologous plasmin enzyme injection.
Results
After the autologous plasmin enzyme injection, a total PVD was observed in 23 eyes and no PVD was observed in 3 eyes. The visual acuity gradually recovered after the injection, improved by 2 lines or more in 23 eyes, and remained unchanged in the 3 eyes. The retinal thickness also recovered gradually at 1, 3, 6, and 12 months. The mean retinal thickness was reduced from 602.12 to 253.62 μm at 12 months after surgery. It was reduced significantly after 1, 3, 6, and 12 months ( P < .0001).
Conclusions
Intravitreal autologous plasmin enzyme may lead to an improvement of visual acuity and a reduction of macula edema in eyes with BRVO.
Branch retinal vein occlusions (BRVOs) are retinal vascular disorders that commonly lead to a decrease of vision. The visual decrease occurs by distinct mechanisms: retinal capillary nonperfusion, vitreous hemorrhage, and macular edema. The site of occlusion of a BRVO typically occurs at a crossing point between arteries and vein within the retina, where they share a common adventitial sheath.
Several investigators have reported on the value of systemic treatments with thrombolytic agents, for example, tissue plasminogen activator (tPA) and urokinase, in eyes with a CRVO or BRVO. However, because of the systemic side effects of thrombolytic agents, this approach has not been adopted widely or studied definitively. To limit the systemic side effects, investigators have delivered the thrombolytic agent locally, for example, an intravitreal injection or through retinal endovascular cannulation. Recent studies have shown that an intravitreal injection of tPA was effective and safe for CRVO and BRVO. tPA is a thrombolytic agent that has a high affinity for fibrin and splits plasminogen to plasmin almost exclusively in fibrin clots. Plasmin is a serine protease of the fibrinolytic process and is highly effective in the proteolysis of fibrin, laminin, and fibronectin. However, the amount of plasminogen in the vitreous has not been determined, and a high dosage of intravitreal tPA may be toxic to the human retina. The mechanism of action of intravitreal tPA is believed to be its thrombolytic effects and also its ability to create a posterior vitreous detachment (PVD). However, the mechanism of intravitreal plasmin action on macular edema and serous macular detachments in eyes with BRVO is not known. The purpose of this study was to evaluate the efficacy of intravitreal autologous plasmin enzyme injection for macular edema associated with BRVO.
Methods
Twenty-six eyes (14 from men, 12 from women) of 26 patients with macular edema caused by a BRVO were studied. All of the patients were referred to Juntendo University Urayasu Hospital. The mean age of the patients was 58.7 ± 6.6 years with a range of 50 to 74 years at the time of the injection. The interval between the initial symptoms to the time of treatment was 3 months or more, and no recovery of the symptoms was observed during this interval in all patients.
All patients were treated between December 2004 and January 2009 and were followed up for a minimum of 12 months. None of the patients had signs of PVD. Patients with a recent onset of the BRVO (duration of symptoms < 2 months); patients with only a slight decrease in visual acuity; patients with any sign of spontaneous resolution; patients with a BRVO complicated with anterior or posterior neovascularization; patients treated by laser photocoagulation, cataract surgery, and vitreous surgery; patients with other ocular disorders known to decrease visual acuity, for example, uncontrolled glaucoma, cataract, age-related macular degeneration, macular ischemia, and diabetic retinopathy; and patients with myopia of more than −6 diopters were excluded. Because the macular edema associated with BRVO can resolve spontaneously, we selected patients whose visual acuity had not recovered in the 3 months since the onset.
Preparation and Injection of Autologous Plasmin Enzyme
Autologous plasmin enzyme was prepared as reported. Briefly, 30 mL of each patient’s blood was drawn from the antecubital vein 3 days before the treatment. Plasminogen was purified from the autologous plasma by affinity chromatography using a lysine affinity column. The plasminogen then was eluted from the column using epsilon amino caproic acid. The amino caproic acid was removed by dialysis. The plasminogen was concentrated to a volume of 0.5 mL and converted to plasmin by addition of urokinase and then sterilized by filtering through a 0.22-μm filter. The enzyme activity was tested spectrophotometrically by measuring the change in absorbance at 405 nm after cleavage by D-val-leu-p-nitroaniline substance (S-2251; Sekisui Medical Co. Ltd, Tokyo, Japan). The plasmin was stored at 4 degrees centigrade until used. An aliquot was sent for sterility testing before the intravitreal injection, and the cultures were observed for 48 hours.
The intravitreal injection of autologous plasmin enzyme was carried out under sterile conditions in the operating room with topical anesthesia. A paracentesis was performed first, and then 1 IU autologous plasmin enzyme in 0.1 mL was injected intravitreally 4 mm posterior to the limbus just over the surface of the optic disc with a 30-gauge needle attached to a 1-mL syringe.
After the injection, patients were instructed to lie supine for 8 hours to allow the autologous plasmin enzyme to settle on the retinal surface. Topical corticosteroid and antibiotics were used daily for 1week after the injection.
Clinical Examination
Ophthalmologic examinations were performed before and on day 7, and at 1, 3, 6, and 12 months after the autologous plasmin enzyme injection. Eyes were evaluated by measuring the best-corrected decimal visual acuity, slit-lamp examination, ophthalmoscopy, fluorescein angiography, and optical coherence tomography. The foveal thickness was defined as thickness at the center of the fovea measured on the images obtained by OCT-3000 (Carl Zeiss, Dublin, California, USA). B-scan ultrasonography was performed before and on days 1 and 7 after the injection. The presence and extent of a PVD were determined by ophthalmoscopy, optical coherence tomography, and ultrasonography. Electroretinograms were recorded before and on day 7 after the injection of autologous plasmin enzyme. The diagnosis and the necessity of laser photocoagulation after the autologous plasmin enzyme were determined by fluorescein angiography.
Statistical Analyses
The results are expressed as the means ± standard deviations. The data were compared by analysis of variance and the Dunnnet post hoc test. A P value of < .05 was considered statistically significant. The decimal visual acuity was converted to the logarithm of the minimal angle of resolution (logMAR) units for statistical analyses.
Results
The clinical data of the 26 patients are summarized in the Table . The mean interval between the onset of the symptoms of BRVO and treatment was 4.2 months, and the mean follow-up period was 20.7 months (range, 12 to 32 months). One week after the injection of autologous plasmin enzyme, the VA had improved by more than 0.2 logMAR units in 10 eyes (38.5%), was unchanged in 11 eyes (42.3%), and worsened in 5 eyes (19.2%). Six months after the injection, the VA had improved in 22 eyes (84.6%), was unchanged in 4 eyes (15.4%), and had worsened in none of the eyes. Twelve months after the injection, the VA had improved in 23 eyes (88.5%), was unchanged in 3 eyes (11.5%), and had worsened in none of the eyes. The mean best-corrected decimal visual acuity improved significantly from 0.550 ± 0.298 logMAR units to 0.450 ± 0.296 logMAR units ( P = .1009) at 1 week, to 0.362 ± 0.279 logMAR units ( P = .0002) at 1 month, to 0.256 ± 0.238 logMAR units ( P < .0001) at 3 months, to 0.233 ± 0.268 logMAR units ( P < .0001) at 6 months, and to 0.175 ± 0.208 logMAR units ( P < .0001) at twelve months after the intravitreal injection of autologous plasmin enzyme ( Figure 1 ). At 12 months, the VA of all eyes had improved ( Figure 2 ).
| Case No. | Age (yrs) | Sex | Duration (mos) a | Macular Thickness (μm) | Visual Acuity | PVD | PC | Complication | Follow-up (mos) | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Before | After | Before | After | ||||||||
| 1 | 51 | Female | 5 | 609 | 168 | 20/200 | 20/60 | + | − | None | 32 |
| 2 | 58 | Female | 3 | 446 | 229 | 20/40 | 20/20 | + | + | None | 29 |
| 3 | 55 | Female | 6 | 621 | 202 | 20/120 | 20/60 | + | + | None | 27 |
| 4 | 68 | Female | 4 | 394 | 168 | 20/80 | 20//20 | + | − | None | 26 |
| 5 | 61 | Female | 4 | 544 | 289 | 20/60 | 20/60 | + | − | None | 26 |
| 6 | 51 | Male | 4 | 479 | 285 | 20/50 | 20/25 | + | + | None | 26 |
| 7 | 67 | Female | 3 | 705 | 332 | 20/60 | 20/30 | + | + | None | 25 |
| 8 | 54 | Male | 3 | 541 | 386 | 20/50 | 20/40 | + | + | None | 25 |
| 9 | 66 | Female | 4 | 548 | 212 | 20/200 | 20/50 | – | – | None | 24 |
| 10 | 56 | Male | 3 | 667 | 183 | 20/60 | 20/30 | + | + | None | 24 |
| 11 | 52 | Male | 5 | 662 | 275 | 20/200 | 20/50 | + | − | None | 24 |
| 12 | 58 | Female | 4 | 792 | 182 | 20/100 | 20/30 | + | − | None | 24 |
| 13 | 50 | Male | 4 | 417 | 210 | 20/40 | 20/15 | + | + | None | 23 |
| 14 | 57 | Female | 5 | 583 | 148 | 20/100 | 20/15 | + | − | Inflammation | 21 |
| 15 | 68 | Male | 5 | 586 | 295 | 20/100 | 20/40 | + | + | None | 20 |
| 16 | 60 | Female | 4 | 471 | 350 | 20/400 | 20/120 | + | + | None | 20 |
| 17 | 50 | Male | 3 | 583 | 128 | 20/50 | 20/25 | + | + | None | 20 |
| 18 | 74 | Male | 4 | 746 | 286 | 20/60 | 20/15 | + | − | None | 20 |
| 19 | 52 | Male | 6 | 1125 | 267 | 20/60 | 20/20 | − | − | None | 16 |
| 20 | 60 | Male | 4 | 466 | 306 | 20/200 | 20/60 | + | − | None | 14 |
| 21 | 66 | Male | 5 | 687 | 478 | 20/50 | 20/25 | − | − | None | 13 |
| 22 | 63 | Female | 5 | 466 | 190 | 20/40 | 20/30 | + | − | None | 13 |
| 23 | 54 | Male | 3 | 626 | 126 | 20/40 | 20/20 | + | − | None | 13 |
| 24 | 64 | Female | 4 | 671 | 631 | 20/60 | 20/50 | + | − | None | 12 |
| 25 | 57 | Male | 5 | 539 | 152 | 20/25 | 20/15 | + | − | None | 12 |
| 26 | 55 | Male | 3 | 681 | 125 | 20/60 | 20/15 | + | + | None | 12 |
a Duration was the duration between time of onset and autologous plasmin enzyme injection.
