Creating a complete posterior vitreous detachment (PVD) is important to manage vitreoretinal disorders including macular hole, vitreomacular traction, proliferative diabetic retinopathy, and proliferative vitreoretinopathy. In most patients, PVD can usually be induced by active aspiration of the vitreous gel from the nasal retina around the optic disc. With the assistance of triamcinolone acetonide, a better visualization of the vitreous can be achieved, which facilitates and ensures complete separation of the vitreous cortex from the retina.1 However, to induce an atraumatic PVD is particularly challenging in young children whose posterior hyaloid is tightly attached to the retina.2 Despite the improvement of instruments and techniques for vitreoretinal surgery in recent years, surgical removal of the vitreous cortex still carries the great risk of retinal tear or retinal detachment.3 Enzymatic vitreolysis thus may offer a less traumatic way for inducing PVD, especially in pediatric patients.4,5
Tissue plasminogen activator (tPA) is an enzyme that catalyzes the conversion of plasminogen to plasmin. Because plasminogen is rich in serum, we hypothesize that co-administration of tPA and autologous serum in the vitreous cavity may generate plasmin locally and facilitate the enzymatic cleavage of posterior hyaloid from the retina. For eyes with preexisting vitreous hemorrhage, injection of tPA alone may induce PVD. In this study, we review our clinical results of six pediatric cases to see whether intravitreal injection of tPA along with autologous serum in eyes without preexisting vitreous hemorrhage and intravitreal injection of tPA in eyes with preexisting vitreous hemorrhage preoperatively may help PVD induction during vitrectomy.
Patients and Methods
A retrospective chart review was done of pediatric patients who received intravitreal injection of tPA and autologous serum to induce PVD 3 days before vitrectomy from January 2011 to December 2014 at Changhua Christian Hospital, Taiwan. The study was approved by the institutional review board of Changhua Christian Hospital. Patients younger than 10 years who had undergone intravitreal injection of tPA with or without autologous serum 3 days before vitrectomy were included. All patients underwent a complete ophthalmologic evaluation, including slit-lamp examination, indirect ophthalmoscopy, intraocular pressure measurement, and visual acuity. Optical coherence tomography was performed in some cases. Data extracted from the chart included the age and gender of the patient, the presence of retinal pathologic features, preoperative visual condition, postoperative visual condition, surgical methods, complications, and length of follow-up.
Informed consent was obtained before performing the procedures. For preparation of autologous serum, 5 to 10 mL of blood was taken by venipuncture. The blood was allowed to clot for 15 minutes at room temperature. After centrifugation at 2,500 revolutions per minute for 15 minutes, the serum was extracted. Twenty-five micrograms of tPA (Actilyse; Boehringer Ingelheim, Ingelheim am Rhein, Germany) and 0.1 mL of autologous serum were injected through the pars plana with a 30-gauge needle under sterile conditions in clinic. Antibiotic drops were given for 3 days after the injection. Three days after intravitreal injection, each patient had 23-gauge vitrectomy under general anesthesia. All surgeries were performed by one experienced surgeon (S-NC). After core vitrectomy, PVD was induced with a vacuum of 300 mm Hg at the nasal aspect of the optic disc. A PVD was considered to be present if a Weiss ring was seen to be freely detached from the retina.
Four boys and 2 girls were included. Ages ranged from 39 weeks' postmenstrual age to 8 years. The indications for pars plana vitrectomy were traumatic macular hole (cases 1 and 2); retinopathy of prematurity with vitreous hemorrhage (case 3); abusive head trauma with premacular, subinternal limiting membrane hemorrhage and macular hole (case 4); traumatic dense vitreous hemorrhage (case 5); and dense vitreous hemorrhage without known cause (case 6). The patient data are shown in Table 1. All patients received intravitreal injection of 25 µg of tPA 3 days before vitrectomy. For cases without preexisting vitreous hemorrhage (cases 1 and 2), 0.1 mL of intravitreal autologous serum was co-administered. All cases had PVD induced successfully with a vacuum of 300 mm Hg during vitrectomy. A Weiss ring was observed as freely detached from the retina intraoperatively in all cases.
The follow-up period ranged from 12 to 45 months. The final visual acuity improved in 3 cases (cases 1, 2, and 6) and could not be checked preoperatively in the other patients. The macular hole was closed successfully in 3 of 3 cases (cases 1, 2, and 4) (Figures 1–2).
(A) Before vitrectomy, a giant macular hole and retinal pigment epithelium alteration around the fovea in the left eye were noted in case 1. (B) After vitrectomy, visual acuity improved from counting fingers to 20/200 and the macular hole was closed.
(A) Before vitrectomy, indirect funduscopy and optical coherence tomography in the right eye revealed a macular hole in case 2. (B) After vitrectomy, the visual acuity recovered to 20/50 and the macular hole was closed.
No complications occurred with the use of tPA and autologous serum in this cohort of patients. No surgical complications were noted. There was no evidence of retinal toxicity related to tPA injection or postoperative increase in intraocular pressure. In addition, no intraretinal or vitreous bleeding was observed, and postoperative anterior segment inflammation was minimal.
The induction of PVD is difficult in children. Because of the strong adherence between the vitreous and retina in children, mechanical peeling of the vitreous is likely to be lamellar and tends not to result in complete vitreous removal. PVD is important in vitreomacular surgeries.6 Therefore, how to detach the posterior vitreous without trauma to the retina is a major but challenging goal in pediatric vitrectomy.
Enzymatic adjuncts that can create an atraumatic and complete vitreoretinal separation are considered a good choice before pediatric vitrectomy. Sebag proposed a classification of the enzymatic adjuncts based on the biologic effect on the vitreous, including “liquefactants” that refer to the ability to liquefy vitreous and “interfactants” that cause disruption of the vitreoretinal interface.7 A purely liquefactant compound, such as hyaluronidase, results in vitreous liquefaction without PVD formation due to the absence of an interfactant effect.7,8 Chondroitinase and dispase are examples of interfactants. Although chondroitinase breaks down chondroitin sulfate, its ability to induce PVD is inconsistent.9 Dispase cleaves collagen type IV and fibronectin to induce PVD in animal and human cadaveric eyes,10,11 but its harmful effects on retinal vessels and diminution of electroretinogram amplitude precludes clinical use.12–14 On the other hand, plasmin, which is a nonspecific serine protease,15 has both interfactant and liquefactant properties.7 The hydrolysis of laminin and fibronectin by plasmin enzyme spontaneously creates a PVD or allows for a relatively atraumatic peeling of the posterior hyaloid from the retinal surface.16
Plasmin has been used in humans most commonly in the form of autologous plasmin enzyme.17 Before ocular administration, inactive human plasminogen isolated from blood requires conversion in vitro to enzymatically active plasmin by streptokinase.18 However, autologous plasmin enzyme is relatively unstable19; the isolation of autologous plasmin is also a costly and time-consuming process, and the necessary facilities are not readily available everywhere. Hesse et al. thus applied cryopexy followed by intravitreal injection of tPA in rabbit eyes to induce PVD: by temporally breaking down the blood retinal barrier with cryotherapy, plasminogen activator from the blood was able to influx into the vitreous cavity, which was then converted to plasmin, resulting in the subsequent induction of PVD.20
More recently, microplasmin (ocriplasmin), a biologically produced recombinant enzyme, has been evaluated in Phase II19,21 and Phase III randomized controlled trials.4 Ocriplasmin has a smaller molecular mass (28 vs 88 kDa) than human plasmin22,23 and theoretically penetrates the vitreoretinal interface more effectively than human plasmin.24 Ocriplasmin also has a half-life in blood several times longer than human plasmin25 and is therefore able to more effectively induce vitreous liquefaction and separation from the retina. Unfortunately, ocriplasmin is expensive and is not covered by the national health insurance in Taiwan.
Autologous plasmin enzyme has been used as an adjunct to pediatric vitrectomy in a variety of clinical conditions, such as traumatic macular hole,26,27 congenital x-linked retinoschisis,28 and stage 5 retinopathy of prematurity.29,30 In addition to direct injection of purified plasmin into the vitreous cavity,17,31–35 several methods have been previously used to achieve sufficient plasmin concentration in the vitreous, including injection of tPA in proliferative diabetic retinopathy36 and cryopexy followed by tPA injection.20 In the former method, plasminogen was present in the vitreous cavity because of the loss of the blood–retinal barrier in eyes with proliferative diabetic retinopathy; in the latter method, cryopexy induced the breakdown of the blood–retinal barrier with a subsequent influx of plasminogen into the vitreous cavity. In proliferative diabetic retinopathy, the use of 25 µg of tPA by intravitreal injection 15 minutes before vitrectomy did not improve the results of the number of perioperative iatrogenic tears, the gain in visual acuity, and the reattachment rate of tractional retinal detachments.36 The failure could be attributed to a short delay between tPA injection and beginning of surgery, an insufficient dose, or an insufficient quantity of plasminogen in the vitreous at the beginning of the intervention.36 We hypothesized that 3 days in our series was a long enough time interval to make tPA and autoserum to produce plasmin.
In our series, we used the co-administration of both autologous serum and tPA in eyes without vitreous hemorrhage and only injected tPA in eyes with preoperative vitreous hemorrhage 3 days before vitrectomy in 6 consecutive pediatric patients. We did not inject autologous serum in eyes with preexisting vitreous hemorrhage because we hypothesized that it contained plasminogen in vitreous hemorrhage. PVD was successfully induced in every eye. A Weiss ring was visualized intraoperatively in all cases. Three of 3 patients had macular hole closure after surgery, and all patients with dense vitreous hemorrhage had the vitreous hemorrhage removed without any complications related to the PVD procedures. The outcomes of our study indicate that intravitreal tPA in the presence of serum could probably produce a sufficient amount of plasmin to cleave the vitreoretinal interface by converting plasminogen in serum to plasmin. Further studies are required to validate this preliminary study.
It has been reported that retinal toxicity has followed intravitreal tPA.37–39 Endophthalmitis from intravitreal injection of tPA and autologous serum is another possible complication. However, even though we did not observe any related complications in our study, these complications may still be a major concern.
The limitations of this study include the small case number and its retrospective nature. There was no retrospective control group in this study because this method was used in all pediatric vitrectomy cases. There was no direct evidence to quantify increased plasmin levels in the vitreous after intravitreal injection of tPA and autologous serum.
Intravitreal tPA in the presence of intravitreal serum, either co-administered or preexisting within the vitreous cavity, is an alternative approach to help induce PVD in pediatric vitrectomy. No prior pre-clinical or clinical studies have tested this approach. This was a hypothesis-driven approach sought by the authors. This is a preliminary study and further studies are required prior to definitive recommendations.
- Peyman GA, Cheema R, Conway MD, Fang T. Triamcinolone acetonide as an aid to visualization of the vitreous and the posterior hyaloid during pars plana vitrectomy. Retina. 2000;20:554–555. doi:10.1097/00006982-200005000-00024 [CrossRef]
- Sebag J. Age-related differences in the human vitreoretinal interface. Arch Ophthalmol. 1991;109:966–971. doi:10.1001/archopht.1991.01080070078039 [CrossRef]
- Hikichi T, Kosaka S, Takami K, et al. Incidence of retinal breaks in eyes undergoing 23-gauge or 20-gauge vitrectomy with induction of posterior vitreous detachment. Retina. 2012;32:1100–1105. doi:10.1097/IAE.0b013e3182349449 [CrossRef]
- Stalmans P, Benz MS, Gandorfer A, et al. Enzymatic vitreolysis with ocriplasmin for vitreomacular traction and macular holes. N Engl J Med. 2012;367:606–615. doi:10.1056/NEJMoa1110823 [CrossRef]
- Chen W, Huang X, Ma XW, Mo W, Wang WJ, Song HY. Enzymatic vitreolysis with recombinant microplasminogen and tissue plasminogen activator. Eye (Lond). 2008;22:300–307. doi:10.1038/sj.eye.6702931 [CrossRef]
- Steel DH, Lotery AJ. Idiopathic vitreomacular traction and macular hole: a comprehensive review of pathophysiology, diagnosis, and treatment. Eye (Lond). 2013;27(suppl 1):S1–S21. doi:10.1038/eye.2013.212 [CrossRef]
- Sebag J. Pharmacologic vitreolysis–premise and promise of the first decade. Retina. 2009;29:871–874. doi:10.1097/IAE.0b013e3181ac7b3c [CrossRef]
- Hikichi T, Kado M, Yoshida A. Intravitreal injection of hyaluronidase cannot induce posterior vitreous detachment in the rabbit. Retina. 2000;20:195–198. doi:10.1097/00006982-200002000-00014 [CrossRef]
- Hermel M, Schrage NF. Efficacy of plasmin enzymes and chondroitinase ABC in creating posterior vitreous separation in the pig: a masked, placebo-controlled in vivo study. Graefes Arch Clin Exp Ophthalmol. 2007;245:399–406. doi:10.1007/s00417-006-0388-1 [CrossRef]
- Oliveira LB, Tatebayashi M, Mahmoud TH, Blackmon SM, Wong F, McCuen BW 2nd, . Dispase facilitates posterior vitreous detachment during vitrectomy in young pigs. Retina. 2001;21:324–331. doi:10.1097/00006982-200108000-00005 [CrossRef]
- Tezel TH, Del Priore LV, Kaplan HJ. Posterior vitreous detachment with dispase. Retina. 1998;18:7–15. doi:10.1097/00006982-199801000-00003 [CrossRef]
- Wang F, Wang Z, Sun X, Xu X, Zhang X. Safety and efficacy of dispase and plasmin in pharmacologic vitreolysis. Invest Ophthalmol Vis Sci. 2004;45:3286–3290. doi:10.1167/iovs.04-0026 [CrossRef]
- Jorge R, Oyamaguchi EK, Cardillo JA, Gobbi A, Laicine EM, Haddad A. Intravitreal injection of dispase causes retinal hemorrhages in rabbit and human eyes. Curr Eye Res. 2003;26:107–112. doi:10.1076/ceyr.22.214.171.12416 [CrossRef]
- Zhu D, Chen H, Xu X. Effects of intravitreal dispase on vitreoretinal interface in rabbits. Curr Eye Res. 2006;31:935–946. doi:10.1080/02713680600932142 [CrossRef]
- Gandorfer A. Microplasmin-assisted vitrectomy. Dev Ophthalmol. 2009;44:26–30. doi:10.1159/000223942 [CrossRef]
- Uemura A, Nakamura M, Kachi S, et al. Effect of plasmin on laminin and fibronectin during plasmin-assisted vitrectomy. Arch Ophthalmol. 2005;123:209–213. doi:10.1001/archopht.123.2.209 [CrossRef]
- Williams JG, Trese MT, Williams GA, Hartzer MK. Autologous plasmin enzyme in the surgical management of diabetic retinopathy. Ophthalmology. 2001;108:1902–1905. doi:10.1016/S0161-6420(01)00720-5 [CrossRef]
- Rhéaume MA, Vavvas D. Pharmacologic vitreolysis. Semin Ophthalmol. 2010;25:295–302. doi:10.3109/08820538.2010.518865 [CrossRef]
- de Smet MD, Gandorfer A, Stalmans P, et al. Microplasmin intravitreal administration in patients with vitreomacular traction scheduled for vitrectomy: the MIVI I trial. Ophthalmology. 2009;116:1349–1355. doi:10.1016/j.ophtha.2009.03.051 [CrossRef]
- Hesse L, Nebeling B, Schroeder B, Heller G, Kroll P. Induction of posterior vitreous detachment in rabbits by intravitreal injection of tissue plasminogen activator following cryopexy. Exp Eye Res. 2000;70:31–39. doi:10.1006/exer.1999.0772 [CrossRef]
- Benz MS, Packo KH, Gonzalez V, et al. A placebo-controlled trial of microplasmin intravitreous injection to facilitate posterior vitreous detachment before vitrectomy. Ophthalmology. 2010;117:791–797. doi:10.1016/j.ophtha.2009.11.005 [CrossRef]
- Shi GY, Wu HL. Isolation and characterization of microplasminogen: a low molecular weight form of plasminogen. J Biol Chem. 1988;263:17071–17075.
- Nagai N, Demarsin E, Van Hoef B, et al. Recombinant human microplasmin: production and potential therapeutic properties. J Thromb Haemost. 2003;1:307–313. doi:10.1046/j.1538-7836.2003.00078.x [CrossRef]
- Gandorfer A, Rohleder M, Sethi C, et al. Posterior vitreous detachment induced by microplasmin. Invest Ophthalmol Vis Sci. 2004;45:641–647. doi:10.1167/iovs.03-0930 [CrossRef]
- de Smet MD, Valmaggia C, Zarranz-Ventura J, Willekens B. Microplasmin: ex vivo characterization of its activity in porcine vitreous. Invest Ophthalmol Vis Sci. 2009;50:814–819. doi:10.1167/iovs.08-2185 [CrossRef]
- Margherio AR, Margherio RR, Hartzer M, Trese MT, Williams GA, Ferrone PJ. Plasmin enzyme-assisted vitrectomy in traumatic pediatric macular holes. Ophthalmology. 1998;105:1617–1620. doi:10.1016/S0161-6420(98)99027-3 [CrossRef]
- Wu WC, Drenser KA, Trese MT, Williams GA, Capone A. Pediatric traumatic macular hole: results of autologous plasmin enzyme-assisted vitrectomy. Am J Ophthalmol. 2007;144:668–672. doi:10.1016/j.ajo.2007.07.027 [CrossRef]
- Wu WC, Drenser KA, Capone A, Williams GA, Trese MT. Plasmin enzyme-assisted vitreoretinal surgery in congenital X-linked retinoschisis: surgical techniques based on a new classification system. Retina. 2007;27:1079–1085. doi:10.1097/IAE.0b013e31806196d0 [CrossRef]
- Tsukahara Y, Honda S, Imai H, et al. Autologous plasmin-assisted vitrectomy for stage 5 retinopathy of prematurity: a preliminary trial. Am J Ophthalmol. 2007;144:139–141. doi:10.1016/j.ajo.2007.03.020 [CrossRef]
- Wu WC, Drenser KA, Lai M, Capone A, Trese MT. Plasmin enzyme-assisted vitrectomy for primary and reoperated eyes with stage 5 retinopathy of prematurity. Retina. 2008;28(suppl 3):S75–S80. doi:10.1097/IAE.0b013e318158ea0e [CrossRef]
- Gandorfer A, Putz E, Welge-Lüssen U, Grüterich M, Ulbig M, Kampik A. Ultrastructure of the vitreoretinal interface following plasmin assisted vitrectomy. Br J Ophthalmol. 2001;85:6–10. doi:10.1136/bjo.85.1.6 [CrossRef]
- Hikichi T, Yanagiya N, Kado M, Akiba J, Yoshida A. Posterior vitreous detachment induced by injection of plasmin and sulfur hexafluoride in the rabbit vitreous. Retina. 1999;19:55–58. doi:10.1097/00006982-199901000-00009 [CrossRef]
- Li X, Shi X, Fan J. Posterior vitreous detachment with plasmin in the isolated human eye. Graefes Arch Clin Exp Ophthalmol. 2002;240:56–62. doi:10.1007/s004170100351 [CrossRef]
- Trese MT, Williams GA, Hartzer MK. A new approach to stage 3 macular holes. Ophthalmology. 2000;107:1607–1611. doi:10.1016/S0161-6420(00)00210-4 [CrossRef]
- Wang ZL, Zhang X, Xu X, Sun XD, Wang F. PVD following plasmin but not hyaluronidase: implications for combination pharmacologic vitreolysis therapy. Retina. 2005;25:38–43. doi:10.1097/00006982-200501000-00005 [CrossRef]
- Le Mer Y, Korobelnik JF, Morel C, Ullern M, Berrod JP. TPA-assisted vitrectomy for proliferative diabetic retinopathy: results of a double-masked, multicenter trial. Retina. 1999;19:378–382. doi:10.1097/00006982-199909000-00002 [CrossRef]
- Hrach CJ, Johnson MW, Hassan AS, Lei B, Sieving PA, Elner VM. Retinal toxicity of commercial intravitreal tissue plasminogen activator solution in cat eyes. Arch Ophthalmol. 2000;118:659–663. doi:10.1001/archopht.118.5.659 [CrossRef]
- Irvine WD, Johnson MW, Hernandez E, Olsen KR. Retinal toxicity of human tissue plasminogen activator in vitrectomized rabbit eyes. Arch Ophthalmol. 1991;109:718–722. doi:10.1001/archopht.1991.01080050134044 [CrossRef]
- Johnson MW, Olsen KR, Hernandez E, Irvine WD, Johnson RN. Retinal toxicity of recombinant tissue plasminogen activator in the rabbit. Arch Ophthalmol. 1990;108:259–263. doi:10.1001/archopht.1990.01070040111042 [CrossRef]
|Case||Age||Gender||Eye||Basic Data and Eye Findings||Surgical Methods||Preoperative Visual Condition||Postoperative Visual Condition and Eye Findings||Follow-up (mo)|
|1||6 (y)||M||OS||Traumatic MH||PPV, ICG-assisted ILM peeling and 13% C3F8||BCVA: counting fingers||BCVA: 20/200; MH was closed; RPE alteration around fovea||12|
|2||8 (y)||M||OD||Traumatic MH||PPV, ICG-assisted ILM peeling and 13% C3F8||BCVA: 20/100||BCVA: 20/50; MH was closed; ring-shaped fibrosis around the fovea||13|
|3||39 weeks' PMA||F||OS||Prematurity (GA: 28 weeks, BBW: 1,120 g, ROP stage 3, zone I s/p IVI bevacizumab); dense VH||PPV and peripheral retinal photocoagulation||Unchecked||BCVA: 20/50; AR: −9.50/−2.50 × 0; tessellated fundus||45|
|4||6 (mo)||F||OS||Abusive head trauma, premacular hemorrhage, sub-ILM hemorrhage, and MH||PPV, ICG-assisted ILM peeling and 30% SF6||Unchecked||AR: −9.50/−3.00 × 46; tessellated fundus||27|
|5||1 (y)||M||OD||Trauma with dense VH; Berlin's edema||PPV||Unchecked||BCVA: 20/200; AR: −1.25/−0.75 × 165; macular RPE atrophy, disc mild pallor, and mild esotropia||34|
|6||2 (y)||M||OS||Dense VH; unknown cause||PPV||BCVA: counting fingers||BCVA: 20/200; AR: −12.00/−2.50 × 13; tessellated fundus and esotropia||37|