Plasmin-assisted vitrectomy for management of proliferative membrane in proliferative diabetic retinopathy: a pilot study. Retina. 2007;27:1074-1078. [PMID: 18040248 DOI: 10.1097/iae.0b013e3180592beb]

Surgical strategy and outcome in patients with bilateral proliferative diabetic retinopathy

OBJECTIVES

To investigate the current surgery strategies for bilateral proliferative diabetic retinopathy (PDR), as well as the surgical outcomes of patients with bilateral PDR who underwent pars plana vitrectomy (PPV).

MATERIALS

Patients undergoing bilateral vitrectomy for PDR from January 2019 to December 2020 at The Eye Hospital of Wenzhou Medical University were enrolled. Clinical data were collected from the electronic medical records. Factors associated with the time interval between the surgeries on two eyes and postoperative visual outcomes were analyzed.

RESULTS

In total, 152 patients with bilateral PDR who underwent bilateral PPV were included in this analysis. Mean age was 53.7 ± 11.4 years. Compared with second-surgery eyes, 60.5% of first-surgery eyes had worse preoperative best-corrected visual acuity (BCVA). The overall PPV time (median, quartile range) between first and second surgeries eye was 1.40 (0.70, 3.15) months. Multivariate analysis showed that the preoperative BCVA of the second-surgery eye had a significant effect on the inter-surgery time interval (P = 0.048). First-surgery eyes had greater vision improvement than second-surgery eyes (Difference of the logarithm of the minimum angle of resolution [LogMAR] BCVA: - 1.00 [- 1.48, - 0.12] versus 0.00 [- 1.30, 0.00], respectively, P < 0.001), especially when eyes with poorer BCVA underwent PPV first (- 1.15 [- 1.87, - 0.54] versus 0.00 [- 0.70, 0.00], respectively, P < 0.001).

CONCLUSIONS

Visual acuity is a significant factor that influences surgical strategies, including both surgery order and interval, for patients with bilateral PDR. The eyes operated upon first show more vision improvement due to prompt surgery.

Untangling the Extracellular Matrix of Idiopathic Epiretinal Membrane: A Path Winding among Structure, Interactomics and Translational Medicine

Idiopathic epiretinal membranes (iERMs) are fibrocellular sheets of tissue that develop at the vitreoretinal interface. The iERMs consist of cells and an extracellular matrix (ECM) formed by a complex array of structural proteins and a large number of proteins that regulate cell–matrix interaction, matrix deposition and remodelling. Many components of the ECM tend to produce a layered pattern that can influence the tractional properties of the membranes. We applied a bioinformatics approach on a list of proteins previously identified with an MS-based proteomic analysis on samples of iERM to report the interactome of some key proteins. The performed pathway analysis highlights interactions occurring among ECM molecules, their cell receptors and intra- or extracellular proteins that may play a role in matrix biology in this special context. In particular, integrin β1, cathepsin B, epidermal growth factor receptor, protein-glutamine gamma-glutamyltransferase 2 and prolow-density lipoprotein receptor-related protein 1 are key hubs in the outlined protein–protein cross-talks. A section on the biomarkers that can be found in the vitreous humor of patients affected by iERM and that can modulate matrix deposition is also presented. Finally, translational medicine in iERM treatment has been summed up taking stock of the techniques that have been proposed for pharmacologic vitreolysis.

The effect of intravitreal recombinant tissue plasminogen activator injection on diabetic tractional fibrovascular membranes: Proposed criteria using optical coherence tomography

PURPOSE

To evaluate the effect of intravitreal recombinant tissue plasminogen activator (tPA) on diabetic tractional fibrovascular membranes (FVM) using proposed optical coherence tomography (OCT) criteria.

METHODS

This prospective, interventional case series enrolled eyes with tractional retinal detachment who were candidates for pars plana vitrectomy. OCT images were obtained to evaluate the border of the attached-detached retina and overlying FVP at baseline and 1 week post-intravitreal tPA injection using the follow-up scan acquisition protocol. Two independent graders assessed retinal detachment (RD) height, FVM height, and retinal thickness at the site of membrane attachment.

RESULTS

Thirteen eyes from 13 individuals were included. Assessment of RD height, FVM height, and retinal thickness at membrane attachment point were feasible at both visits in 10/13 (77%), 10/13 (77%), and 8/13 (62%) of eyes, respectively. There was excellent agreement between the two graders for all measurements (all ICC > 0.94). Release of the retina-membrane attachment point was not observed in any eyes. No statistically significant change was found in any of the measured parameters.

CONCLUSIONS

Excellent agreement was achieved between the graders for quantitative assessment of diabetic FVM using our proposed OCT criteria. We did not observe a significant change in the FVM measurements, 1-week after intravitreal tPA injection.

Surgical management of diabetic tractional retinal detachments

Tractional retinal detachment is an end-stage form of diabetic retinopathy that occurs when contractile forces in the vitreous and neovascular tissue lead to the detachment of the neurosensory retina. We review the literature related to the management of this disease. Preoperative planning includes appropriate patient selection, diagnostic and prognostic imaging, and medical optimization with reduction of systemic risk factors. Use of antivascular endothelial growth factor for preoperative treatment has had significant benefits for tractional retinal detachment repair in improving surgical efficiency and outcomes. Advances in microsurgical instrumentation are discussed, with attention to small-gauge vitrectomy with improved flow dynamics, viewing strategies, and lighting allowing bimanual surgery. Special emphasis is placed on bimanual surgical technique, choice of tamponade, and the avoidance of iatrogenic damage. Complications and special considerations are further explored. Based on our compilation of relevant literature, we propose a surgical algorithm for the management of these complex patients.

Pharmacotherapy for Choroidal Neovascularization Due to Uncommon Causes

BACKGROUND

Choroidal neovascularization (CNV) in adults is most commonly associated with neovascular age-related macular degeneration (AMD) and pathologic myopia. Though less common, CNV can also develop from other conditions such as uveitis, central serous chorioretinopathy, angioid streaks, intraocular tumors, hereditary chorioretinal dystrophies, or can be idiopathic in origin. If left untreated, CNV may cause visual loss because of exudation of intraretinal or subretinal fluid, retinal or subretinal hemorrhage, or fibrosis involving the macula. It is well known that one of the main drivers of angiogenesis in CNV development is vascular endothelial growth factor (VEGF) and therefore inhibitors of VEGF might be an effective treatment for CNV.

METHODS

The goal of this review is to provide an overview and summary in the use of pharmacotherapy especially anti-VEGF therapy, in the treatment of CNV due to uncommon causes.

RESULTS

Results from uncontrolled case series and controlled clinical trials have reported good efficacy and safety in using anti-VEGF agents including bevacizumab, ranibizumab, aflibercept and ziv-aflibercept in the treatment of CNV due to uncommon causes. Anti-VEGF has also been used in combination with verteporfin PDT and anti-inflammatory agents for treating CNV of various causes.

CONCLUSION

Pharmacotherapy with anti-VEGF agents is an effective treatment option for CNV due to uncommon etiologies.

Pharmacologic vitreolysis: New strategy for treatment of anomalous vitreo-macular adhesion

Persistent anomalous vitreo-macular adhesion (VMA) is a well-known factor, associated with a variety of sight threatening diseases - including macular hole, vitreo-macular traction syndrome, cystoid and diabetic macular edema, exudative age- related macular degeneration, myopic traction maculopathy and others. With the advent of optical coherence tomography our understanding of these pathologies and the ability of their early diagnosis has gone much far in the past two decades. The release of macular traction has been of exclusive surgical capability. Notwithstanding good results, vitrectomy is hampered by the inability of complete vitreo-retinal separation (i.e., smooth, bare internal limiting membrane), compulsory postoperative positioning in macular hole cases, surgical complications, and high costs. With aim to offer less invasive and safe treatment modality for anomalous VMA, investigators have made enormous progress in the past decade. Leading among the studied nonsurgical measures is the intravitreal application of pharmacologic agents for the induction of vitreo-retinal separation and vitreous liquefaction, a method termed pharmacologic vitreolysis. Several vitreolytic agents have been studied to date, the most potent among them proved to be plasmin. Recently, ocriplasmin (formerly known as microplasmin) - a more stable than plasmin recombinant product, proved to be safe and efficient in releasing VMA in large studies, and consequently received FDA approval. It’s role in clinical practice is now in the process of being determined. This paper aims to review and summarize the current knowledge and status of investigation on this new approach for the treatment of VMA.

Intravitreal autologous plasmin prepared by urokinase for vitreolysis: a pilot study

PURPOSE

To evaluate the effects of intravitreal autologous plasmin injection (IVAP) on vitreoretinal diseases and vitreolysis.

METHODS

In this interventional, prospective, case series pilot study, 8 eyes were assigned to IVAP. Plasminogen as centrifuged from the patients' plasma was converted to plasmin by adding urokinase. A total of 0.2 mL extracted plasmin was injected intravitreally. Posterior vitreous detachment (PVD) and potential injection-related complications at week 4 were the primary outcome measures. Secondary outcomes included changes in best-corrected visual acuity (VA) (logMAR) and central macular thickness (CMT).

RESULTS

Mean age of the patients was 54.35 years. Two patients had complete PVD and 3 patients had partial PVD. Four patients had decrease in CMT. The VA was not changed in 6 patients, improved in 1 patient, and decreased in 1 patient. No uveitis, endophthalmitis, or postinjection vitreous hemorrhage was observed.

CONCLUSIONS

This pilot study demonstrated the efficacy of urokinase-prepared IVAP injection on releasing vitreomacular traction and inducing vitreolysis.

Profile of ocriplasmin and its potential in the treatment of vitreomacular adhesion

The recent approval by the US Food and Drug Administration of ocriplasmin for the treatment of symptomatic vitreomacular adhesion (VMA), often associated with vitreomacular traction (VMT) and macular hole (MH), has brought new attention to the field of pharmacologic vitreolysis. The need for an enzyme to split the vitreomacular interface, which is formed by a strong adhesive interaction between the posterior vitreous cortex and the internal limiting membrane, historically stems from pediatric eye surgery. This review summarizes the different anatomic classifications of posterior vitreous detachment or anomalous posterior vitreous detachment and puts these in the context of clinical pathologies commonly observed in clinical practice of the vitreoretinal specialist, such as MH, VMT, age-related macular degeneration, and diabetic macular edema. We revisit the outcome of the Phase II studies that indicated ocriplasmin was a safe and effective treatment for selected cases of symptomatic VMA and MH. Release of VMA at day 28 was achieved by 26.5% of patients in the ocriplasmin group versus 10.1% in the placebo group (P<0.001). Interestingly, for MHs, the numbers were more remarkable. Predictive factors for successful ocriplasmin treatment were identified for VMT (VMA diameter smaller than 1,500 μm) and MH (smaller than 250 μm). In comparison with the highly predictable outcome after vitrectomy, the general success rate of ocriplasmin not under clinical trial conditions has not fully met expectations and needs to be proven in real-world clinical settings. The ocriplasmin data will be compared in the future with observational data on spontaneous VMA release, will help retina specialists make more accurate predictions, and will improve outcome rates.

Surgical management of diabetic retinopathy

Surgery for late complications of proliferative diabetic retinopathy remains the cornerstone of management even in patients who have received optimal laser photocoagulation and medical therapy. With improvisation in the surgical techniques and development of micro-incision surgical techniques for vitrectomy, the indications for surgical intervention are expanding to include diabetic macular edema with a greater number of patients undergoing early intervention. This review describes the current indications, surgical techniques, adjunctive anti-vascular endothelial growth factor therapy, surgical outcomes, and postoperative complications of pars plana vitrectomy for proliferative diabetic retinopathy and macular edema.

Evolving strategies in the management of diabetic retinopathy

Diabetic retinopathy (DR), the most common long-term complication of diabetes mellitus, remains one of the leading causes of blindness worldwide. Tight glycemic and blood pressure control has been shown to significantly decrease the risk of development as well as the progression of retinopathy and represents the cornerstone of medical management of DR. The two most threatening complications of DR are diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR). Focal/grid photocoagulation and panretinal photocoagulation are standard treatments for both DME and PDR, respectively. Focal/grid photocoagulation is a better treatment than intravitreal triamcinolone acetonide in eyes with DME. Currently, most experts consider combination focal/grid laser therapy and pharmacotherapy with intravitreal antivascular endothelial growth factor agents in patients with center-involving DME. Combination therapy reduces the frequency of injections needed to control edema. Vitrectomy with removal of the posterior hyaloid seems to be effective in eyes with persistent diffuse DME, particularly in eyes with associated vitreomacular traction. Emerging therapies include fenofibrate, ruboxistaurin, renin-angiotensin system blockers, peroxisome proliferator-activated receptor gamma agonists, pharmacologic vitreolysis, and islet cell transplantation.

[Pharmacological vitreolysis]

Posterior vitreous detachment (PVD) is a physiological ageing process. In many cases PVD is incomplete and pathological adhesions of vitreous collagen may be associated with tractional forces in the periphery where they can cause retinal breaks and lead to detachment of the neurosensory retina. In the macular area such tractional forces at the vitreoretinal interface can contribute to the formation of specific entities such as vitreomacular traction syndrome and macular holes which are associated with an impairment of visual acuity and disturbing metamorphopsia. Currently, pars plana vitrectomy with induction of PVD, peeling of epiretinal membranes and the ILM represents an effective and safe treatment option for these conditions. Pharmacological vitreolysis is a new and alternative, non-surgical approach to release tractional forces at the vitreoretinal interface by injecting an enzyme with proteolytic activity against fibronectin and laminin into the vitreous cavity. Certain forms of vitreomacular traction and smaller macular holes can be successfully treated in this way without surgical manipulation of the retinal surface. The role of the concept of pharmacological vitreolysis as a treatment option even for exudative macular diseases or as an adjunct to assist vitreoretinal surgical procedures is currently under investigation.

Review and perspectives on pharmacological vitreolysis

The vitreous is involved in multiple diseases when an incomplete posterior vitreous detachment (PVD) occurs. An incomplete PVD can lead to several pathological conditions. Such visually threatening conditions are traditionally of exclusive surgical interest. In contrast, pharmacological vitreolysis is the effort to reduce or eliminate the pathogenetic role of the vitreous solely by means of drug delivery. Here we aim to review and summarize the evidence available to date about this challenging new approach.

Ocriplasmin for vitreoretinal diseases

Fibronectin and laminin are clinically relevant plasmin receptors in the eye. Located at the vitreoretinal interface, they are cleaved by ocriplasmin (Microplasmin, ThromboGenics, Iselin, NJ), a novel ophthalmic medication. A series of clinical trials to study ocriplasmin for the treatment of vitreoretinal diseases such as vitreomacular traction, macular hole, and exudative age-related macular degeneration are underway. The results are promising and may impact patient care.

Emerging nonsurgical methods for the treatment of vitreomacular adhesion: a review

With the dissemination of optical coherence tomography over the past two decades, the role of persistent vitreomacular adhesion (VMA) in the development of numerous macular pathologies - including idiopathic macular hole, vitreomacular traction syndrome, cystoid and diabetic macular edema, neovascularization in diabetic retinopathy and retinal vein occlusion, exudative age-related macular degeneration, and myopic traction maculopathy - has been established. While invasive vitreoretinal procedures have long been utilized to address complications related to these disorders, such an approach is hampered by incomplete vitreoretinal separation and vitreous removal, surgical complications, and high costs. In light of such limitations, investigators have increasingly looked to nonsurgical means for the treatment of persistent pathologic VMA. Chief among these alternative measures is the intravitreal application of pharmacologic agents for the induction of vitreous liquefaction and/or vitreoretinal separation, an approach termed pharmacologic vitreolysis. This article aims to review the available evidence regarding the use of pharmacologic agents in the treatment of VMA-related pathology. In addition, a discussion of vitreous molecular organization and principles of physiologic posterior vitreous detachment is provided to allow for a consideration of vitreolytic agent mode of action and molecular targets.

Advances in the treatment of diabetic retinopathy

Diabetic retinopathy, the most common long-term complication of diabetes mellitus, remains one of the leading causes of blindness worldwide. Strict metabolic control, tight blood pressure control, laser photocoagulation, and vitrectomy remain the standard care for diabetic retinopathy. Focal/grid photocoagulation is a better treatment than intravitreal triamcinolone acetonide in eyes with diabetic macular edema and should be considered as the first-line therapeutic option. The current evidence suggests that intravitreal triamcinolone acetonide or anti-vascular endothelial growth factor agents result in a temporary improvement of visual acuity and a short-term reduction in central macular thickness in patients with refractory diabetic macular edema and are an effective adjunctive treatments to laser photocoagulation or vitrectomy. However, triamcinolone is associated with risks of elevated intraocular pressure and cataract. Vitrectomy with the removal of the posterior hyaloid without internal limiting membrane peeling seems to be effective in eyes with persistent diffuse diabetic macular edema, particularly in eyes with associated vitreomacular traction. Emerging therapies include islet cell transplantation, fenofibrate, ruboxistaurin, pharmacologic vitreolysis, rennin-angiotensin system blockers, and peroxisome proliferator-activated receptor gamma agonists.

Efficacy of plasmin, microplasmin, and streptokinase-plasmin complex for the in vitro degradation of fibronectin and laminin- implications for vitreoretinal surgery

PURPOSE

Plasmin enzyme generates vitreoretinal separation by degradation of laminin and fibronectin in the vitreoretinal interface. It can be activated from plasminogen by urokinase, tissue plasminogen activator, or by formation of a 1:1 complex with streptokinase. The latter is then converted into a streptokinase-plasmin-complex (SK-P), which displays fibrinolytic activity and can generate free plasmin by proteolysis of plasminogen. We compared the efficacy of SK-P, SK-P activated plasmin, urokinase activated plasmin (UK-P), and microplasmin, a truncated form of plasmin, in cleaving laminin and fibronectin.

METHODS

Streptokinase (SK) was added to human plasminogen in molar ratios between 1:100 and 2:1, generating SK-P at ratios > 1:1, and mixtures of SK-P and free plasmin (SK-P/plasmin) at lower ratios. SK-PL, SK-P/plasmin, UK-P, and microplasmin were added to laminin and fibronectin, incubated at 37 degrees C for 30 min-22 hr and processed for SDS-PAGE.

RESULTS

Proteolysis using SK-activated plasminogen increased when the SK/plasminogen ratio was decreased, generating increasing amounts of free plasmin. Microplasmin and urokinase-activated plasmin displayed similar proteolysis of both laminin and fibronectin as SK/plasminogen at ratios of 1:10 or lower.

CONCLUSION

The mode of plasminogen activation influences the efficacy of proteolysis for laminin and fibronectin and should be considered when plasmin is used in vitreoretinal surgery.

Pharmacotherapy for diabetic retinopathy

BACKGROUND

Diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) continue to cause significant visual loss among patients with diabetes mellitus. In some patients unresponsive to standard laser techniques, as well as improved control of blood pressure and blood sugar, pharmacologic treatment may be beneficial. Although no agent is now approved by the FDA for this purpose, many agents are now being studied in randomized clinical trials (RCTs).

OBJECTIVE

To review concisely the chief pharmacotherapies for diabetic retinopathy available at present.

METHODS

Literature review and synopsis.

RESULTS

Used alone, intravitreal triamcinolone acetonide (IVTA) seems to have some short-term efficacy against DME, but longer-term outcomes (< or = 3 years) using IVTA monotherapy showed a lesser benefit than focal/grid laser treatment in a prospective RCT done by the Diabetic Retinopathy Clinical Research Network. Intravitreal anti-VEGF agents have demonstrated some short-term efficacy against DME, and continuing RCTs will evaluate combination therapies (anti-VEGF and laser) for both DME and PDR. Other agents are being evaluated in pilot studies and Phase II RCTs.

CONCLUSION

Pharmacotherapies for DME and PDR have potential for vision stabilization or improvement. Continuing RCTs will provide evidence-based data on their role in clinical practice. A potential role for pharmacotherapy in the prevention of DME and PDR is also emerging.

Effect of intravitreal plasmin on vitreous removal through a 25-gauge cutting system in the rabbit in vivo

PURPOSE

Intravitreal plasmin creates a posterior vitreous detachment, but may also liquefy the vitreous. This study measures the rate of vitreous removal from rabbit eyes after plasmin injection in vivo.

METHODS

Intravitreal injections of 150 IU hyaluronidase (n = 5), 0.5 activity units (AU, n = 6) or 0.9 AU of streptokinase-activated human plasmin (n = four groups of 6) in 0.1 ml were performed in rabbits, the fellow eyes received 0.1 ml BSS. After 30 min (hyaluronidase), 30 min, 4 h, 12 h or 24 h (0.9 AU plasmin) or 24 h (0.5 AU plasmin), 1 ml of vitreous was removed from each eye without infusion, using a 25-gauge cutter and a standardized protocol. Animals were sacrificed after surgery.

RESULTS

Compared to fellow eyes, the average rate of vitreous removal was increased by hyaluronidase by 68.9 +/- 6.3% (p < 0.05) and by 0.5 AU plasmin (24 h) by 26.8 +/- 3.3% (p < 0.05). 0.9 AU of plasmin increased removal rates by 0.8 +/- 10% (n.s.), 15.4 +/- 6.3% (p < 0.05), 40.3 +/- 3.1% (p < 0.05), and 71.9 +/- 32.4% (p < 0.05) after 30 min, 4 h, 12 h and 24 h incubation respectively. The ratios of removal rates of treated/control eyes in the 0.9 AU groups showed a linear correlation with incubation time (r = 0.783, p < 0.0001).

CONCLUSION

Intravitreal plasmin increases the rate of vitreous removal in rabbits.

Bevacizumab pretreatment and long-acting gas infusion on vitreous clear-up after diabetic vitrectomy

PURPOSE

To evaluate the effects of bevacizumab pretreatment combined with intravitreal infusion of C3F8 10% on the clearance speed of early postoperative vitreous hemorrhage in diabetic vitrectomy for eyes with active fibrovascular proliferation.

DESIGN

Prospective, nonrandomized, comparative case study.

METHODS

Sixteen eyes (15 patients) that underwent primary pars plana vitrectomy for active proliferative diabetic retinopathy (PDR) were prospectively enrolled with a follow-up period of six months or more. These cases received an intravitreal injection of bevacizumab (1.25 mg/0.05 ml) one week prior to surgery and intravitreal C3F8 10% infusion during surgery. The severity of intraoperative bleeding, vitreous clear-up time, percentage of prolonged vitreous clear-up (> or = three weeks), and recurrent hemorrhage respectively were compared with those in a control group (24 eyes in 24 patients) that received gas infusion alone.

RESULTS

The severity of intraoperative bleeding was significantly lower in the study group than in the control group. Vitreous clear-up time for the study group and the control group was 7.2 +/- 5.6 days and 15.2 +/- 11.4 days, respectively (P = .04). Prolonged vitreous clear-up time (> or = three weeks) was observed in one of 16 (6.3%) and nine of 24 (37.5%) of the cases, respectively (P = .03). Early recurrent vitreous hemorrhage rates in the two groups were zero of 16 (0%) and one of 24 (4.2%), respectively (P = .41). Multiple logistic regression analyses showed that bevacizumab pretreatment reduced vitreous clear-up time.

CONCLUSIONS

Bevacizumab pretreatment combined with C3F8 10% infusion could be an effective adjunct to vitrectomy in accelerating postoperative vitreous clear-up for eyes with active PDR.