Michael Hartzer

A new approach to stage 3 macular holes.

PURPOSE The purpose of this article is to demonstrate the feasibility of a surgical approach that might be possible in an office setting for idiopathic stage 3 macular holes. The posterior hyaloid of the vitreous and perihole tissue is enzymatically manipulated to create an atraumatic posterior vitreous separation and may stimulate cell proliferation to close macular holes. DESIGN Prospective noncomparative interventional case series. PARTICIPANTS Nine eyes of eight patients with idiopathic stage 3 macular holes were treated. METHODS The patients were treated with an injection of 0.4 IU of autologous plasmin enzyme into the midvitreous cavity and lavage of the vitreous cavity with an infusion light pipe and vitreous cutter followed by filling 70% to 80% of the vitreous cavity with 14% C3F8 and head-down positioning. MAIN OUTCOME MEASURES Posterior vitreous detachment, macular hole closure, and vision improvement. RESULTS Eight of nine eyes showed a spontaneous posterior vitreous detachment. One eye required minimal suction of less than 50 mmHg to elevate the posterior hyaloid off the retinal surface. Eyes were followed for a minimum of 6 months. All holes closed, and there was an average visual acuity improvement of four lines. The average surgical time for this procedure was 20 minutes. CONCLUSIONS Autologous plasmin enzyme-assisted vitreous surgery techniques can reduce operative time, expense, and patient inconvenience while maintaining excellent surgical results, which may allow office-based vitreous surgery for idiopathic stage 3 macular holes.

Autologous plasmin enzyme in the surgical management of diabetic retinopathy.

PURPOSE This is a pilot study to assess the use of autologous plasmin enzyme (APE) as an adjunct to vitreous surgery in eyes with advanced diabetic retinopathy. DESIGN Prospective noncomparative interventional case series. PARTICIPANTS Seven patients with advanced diabetic retinopathy selected at random from our practice population. METHODS Seven eyes were treated with APE as an adjunct to standard vitreous surgery. Six eyes had macular tractional retinal detachments, and one eye had refractory macular edema. Three fellow eyes had standard vitreous surgery performed for macular tractional retinal detachments without APE. All 10 eyes had macular edema and background diabetic retinopathy. MAIN OUTCOME MEASURES The main outcome measures included induction of a posterior vitreous detachment, retinal reattachment, improvement in visual acuity, and resolution of macular edema. RESULTS All seven APE-treated eyes achieved spontaneous or easy removal of the posterior hyaloid including one eye that had vitreoschisis over areas of detached retina. All eyes treated with APE had resolution of intraretinal edema. Retinas of all eyes treated with APE were reattached. The three fellow eyes were treated by vitreous surgery without APE. Two of the three fellow eyes had reattached retinas, but none had resolution of intraretinal edema without further focal photocoagulation treatment. Mean visual acuity improvement was 0.7 logarithm of the minimum angle of resolution (LogMAR) units in APE-treated eyes and 0.1 LogMAR units in eyes without APE. The average follow-up period was 14 months. CONCLUSIONS This pilot study suggests that APE may be beneficial in the surgical management of diabetic retinopathy.

Treatment of ligneous conjunctivitis with topical plasmin and topical plasminogen.

Purpose To describe treatment of a child with recalcitrant ligneous conjunctivitis secondary to a systemic plasminogen deficiency. Design Interventional case report. Methods A seven-year-old boy developed severe unilateral membranous conjunctivitis recalcitrant to surgical debridement and treatment with topical prednisone, topical cyclosporine, and oral prednisone. Systemic evaluation revealed a severe plasminogen deficiency. Results Treatment with surgical debridement and topical plasmin was ineffective and resulted in prompt recurrence of dense conjunctival membranes. Treatment with topical plasminogen resulted in dramatic improvement and complete resolution of the membranes. Conclusions Ligneous conjunctivitis is secondary to a systemic plasminogen deficiency. Treatment with topical plasminogen resulted in prompt resolution of the membranes. Treatment with topical plasmin was ineffective.

Localization of the Norrie disease gene mRNA by in situ hybridization.

Norrie disease is a rare X-linked recessive neurodevelopmental disorder. The affected males manifest congenital blindness, which is often associated with hearing loss, mental retardation and psychiatric problems. Genetic linkage studies have localized the gene to the short arm of the X-chromosome and the gene has been isolated recently. The encoded protein is a member of the superfamily of growth factors containing a cystine knot motif and may be involved in cell adhesion and neurodevelopment. Molecular genetic analysis revealed a large number of missense, nonsense, deletion, and splice-site mutations among Norrie patients. In order to further determine the role of the Norrie disease gene, we studied the distribution pattern of its mRNA in the retina and in brain by in situ hybridization. The results show abundant hybridization signals in outer nuclear, inner nuclear, and ganglion cell layers of the retina in all three species (mice, rabbit, and human) examined. There was no significant expression in the vitreous body, lens, and rod outer segment. High expression levels were also observed in the cerebellar granular layer, hippocampus, olfactory bulb, cortex, and epithelium of the rabbit brain. These data suggest that the Norrie disease gene could play a critical role in the differentiation or maintenance of the differentiated state of the retina.

AN OVERVIEW OF POTENTIAL APPLICATIONS OF HEPARIN IN VITREORETINAL SURGERY

Heparin is a naturally occurring complex polysaccharide with properties that lend themselves to the potential treatment of proliferative ocular disorders. The biochemistry of heparin and its effects on the eye and cultured ocular cells under varied experimental conditions are discussed.

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°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.

A comparison of 5-fluorouridine and 5-fluorouracil in an experimental model for the treatment of vitreoretinal scarring.

5-Fluorouridine (5-FUR), a ribonucleotide metabolite of 5-Fluorouracil (5-FU), is a more potent inhibitor of cellular proliferation and cell-mediated contraction in vitro than 5-FU. We compared the efficacy of these two drugs in a cell injection model of proliferative vitreoretinopathy using New Zealand albino rabbits. Forty-five eyes were divided into three groups and injected intravitreally with homologous fibroblasts. Eyes were examined at the time of injection and 7, 14, 21 and 28 days thereafter. By day 28, 70.5% (12 of 17) of 5-FUR treated eyes demonstrated no appreciable proliferative or tractional activity compared with 41.7% (5 of 12) of 5-FU treated eyes and 10% (1 of 10) of control eyes (p < 0.006). Medullary ray puckers developed in 29.4% (5 of 17) and 25% (3 of 12) of 5-FUR and 5-FU treated eyes respectively. No 5-FUR treated eye developed extensive tractional or combined tractional and rhegmatogenous retinal detachment compared with 33.3% (4 of 12) of 5-FU treated eyes and 80% (8 of 10) of control eyes (p < 0.001). These results suggest that 5-Fluorouridine may be more effective than 5-FU for the treatment of vitreoretinal scarring.

Intraocular extracellular cyclic nucleotide concentrations: the influence of vitreous surgery

Levels of cAMP (23.1 pmol/ml) and cGMP (22.6 pmol/ml) are nearly equal in normal rabbit vitreous, although aqueous CAMP levels (29.9 pmol/ml) are 10 times higher than aqueous cGMP levels (2.6 pmol/ml) (P<0.01). Intravitreal cAMP values decrease slightly 1 week after vitrectomy and lensectomy and return to normal whether the retina is attached, detached, or surgically removed. In contrast, intravitreal cGMP levels are profoundly depressed at 7 days (approximating normal aqueous levels) and are more than 50% lower than normal 30–42 days after surgery. The presence of these cyclic nucleotides in intraocular fluid and their responsiveness after surgery may signify a potential regulatory role in the physiologic responses of the eye to retinal detachment and its repair.

Uptake and clearance of 5-fluorouridine following subconjunctival and intravitreal injection.

Described are some pharmacokinetic parameters for 5-fluorouridine, a potentially useful intermediate metabolite of 5-fluorouracil (5-FU), following subconjunctival and intravitreal injection in the pigmented rabbit. Immediately following a 500 microgram intravitreal injection of 3H-5-fluorouridine, a peak ipsilateral vitreous concentration of 308 micrograms/ml was measured. This decreased to 199 micrograms/ml at 2 hours, 33 micrograms/ml at 12 hours and 4.4 micrograms/ml at 24 hours, indicating that 5-fluorouridine is cleared from the vitreous at a rate similar to 5-fluorouracil. Aqueous concentrations in the ipsilateral eye reached a maximum at 6 hours (9.6 micrograms/ml) and decreased to 0.8 micrograms/ml at 24 hours. Following subconjunctival injection of 5 mg 3H-5-fluorouridine (0.5 ml), peak ipsilateral anterior chamber concentration of 10.7 micrograms/ml was measured 1 hour after injection and decreased to 2.4 micrograms/ml after 12 hours. Maximum vitreal concentrations of 1.7 micrograms/ml were measured 12 hours after injection.

Intraschisis cavity fluid composition in congenital X-linked retinoschisis.

Purpose: To describe the intraschisis cavity protein composition in congenital X-linked retinoschisis (CXLRS) from two eyes of one child. Methods: The authors present a child with complex, Type 3 CXLRS who underwent bilateral surgical repair with autologous plasmin enzyme-assisted lens-sparing vitrectomy. Undiluted samples of intraschisis fluid and vitreous fluid from two eyes (one child) were obtained and used for protein analysis. Results: The patient underwent successful schisis repair with plasmin-assisted lens-sparing vitrectomy and silicone oil. Two unique protein bands were identified in the intraschisis cavity sample of each eye by gel electrophoresis. The proteins were identified as tenascin-C, an extracellular matrix protein involved in wound healing, and cystatin C, a ubiquitous cysteine protease inhibitor implicated in inflammation. Conclusions: Tenascin-C has previously been described in its complex relationship with decorin and fibronectin in normal wound healing. Tenascin’s upregulation in sites of inflammation and tenascin’s role as an antiadhesive molecule may contribute to the pathogenesis of CXLRS. To the authors’ knowledge, this is the first description of intraschisis cavity fluid.