Two-port Vitrectomy Research Articles

Двухпортовая витреомакулярная хирургия в лечении пациентов с эпиретинальным фиброзом

Perpose. To present a method of two-port vitrectomy in treatment of patients with epiretinal fibrosis. Material and methods. Two-port vitrectomy method was used to treat patients with idiopathic epiretinal fibrosis. The group included 25 patients (25 eyes) – 16 (64 %) women and 9 (36 %) men. The mean age of the patients was 61 ± 6.4 years. Exclusion criteria were glaucoma and concomitant retinal pathology. The mean value of best corrected visual acuity was 0.28 ± 0.07. The mean retinal thickness in the fovea was 417 ± 70 µm. Vitrectomy was performed with installation of two ports in the opposite quadrants – in the lower half for high-flow cannula (illuminator-chandelier built with infusion cannula), in the upper half for vitrectomy cutter and instruments. The High-Flow infusion cannula (Synergetics) integrated with the mercury vapor illuminator-chandelier is connected to the Photon II illumination system (Synergetics). Surgery was performed classically: central vitrectomy, separation of posterior hyaloid membrane, staining of membranes with vitral dye, membrane removal, tamponade ⅓ of vitreous cavity with sterile air. The average operation time was 18 minutes. Results. Six months after the operative treatment all patients noted reduction of visual discomfort and severity of metamorphopsies. Best corrected visual acuity was increased – 0.58 ± 0.1 (p ≤ 0,05 vs. preoperative values). Average retinal thickness in the fovea after surgical treatment decreased to 261 ± 25 µm according to macular OCT chart (p = 0.03). FCM readings were consistent with preoperative 5.1 ± 2.3 f/ms (p ≤ 0.01). Conclusion. The method of two-port vitrectomy with the use of mercury vapor chandeleur in the treatment of vitreomacular pathology allows safe and effective macular surgery. Keywords: retinophototoxicity, vitrectomy, epiretinal fibrosis

Двухпортовая витрэктомия в лечении пациентов с макулярными разрывами

Purpose. Analysis of the first clinical and functional results of treatment of patients with macular holes using the two-port vitrectomy. Material and methods. An analysis of treatment of 15 patients with a diagnosis of macular hole, operated by the method of two-port vitrectomy, was carried out. According to the Gass classification, 7 patients were diagnosed with stage 3 macular hole, and 8 patients with stage 4. All patients underwent microinvasive vitrectomy according to the developed technique. At the beginning of the operation, two ports were installed – one for the infusion cannula with a built-in illuminator (chandelier), the second for the vitreotome. Next, the epiretinal membrane (ERM) (if any) and the internal limiting membrane (ILM) were removed, and plateletrich plasma (PRP) was used at the end of the operation. Intra- and postoperative complications were not registered. Results. The maximum period of observation of patients after treatment was 3 months. In all cases, an anatomical result was achieved – complete closure of the macular hole according to optical coherence tomography (OCT). Mean BCVA results 3 months after treatment were 0.32±0.08. In all cases, improvement in visual functions was achieved (p=0.035). Conclusion. The method of two-port vitrectomy in the treatment of macular holes allows to achieve a good anatomical result, improve visual functions, while minimizing surgical trauma. Key words: macular hole, platelet-rich plasma, two-port vitrectomy.

Двухпортовая хирургия макулярной патологии

Purpose. To evaluate the possibility of two-port surgical treatment of vitreomacular interface pathologies in standard surgical practice. Material and methods. The study included 24 patients (24 eyes) with macular pathology operated by the proposed two-port technique of vitrectomy 25G. The maximum corrected visual acuity before surgery was 0.2 ± 0.12. The minimum follow-up period after surgery is 1 month. Results. In all cases, it was possible to achieve anatomical restoration of the macular zone. The maximum corrected visual acuity after 1 month after surgery increased to an average of 0.6 ± 0.23. In all clinical cases, it was possible to successfully apply the two-port surgery technique. The need to return to traditional 3-port access was not required in any case. Conclusion. The proposed method for the surgical treatment of vitreomacular interface pathology through a two-port access is effective, technically simple and safe. Keywords: vitreomacular traction syndrome, macular hole, two-port vitrectomy 25G.

Возможности двухпортовой витрэктомии в лечении пациентов с эпиретинальным фиброзом

Aim: to evaluate the efficacy and safety of two-port vitrectomy in the treatment of patients with epiretinal fibrosis. Patients and Methods: surgical treatment using a two-port vitrectomy technique was performed in 25 patients (25 eyes) with epiretinal fibrosis. Patients with concomitant retinal pathology (e.g. diabetic or post-thrombotic retinopathy) and glaucoma were not included in the study. Of the total number of patients, 64% (n=16) were women and 36% (n=9) were men. The mean age of the patients was 61±6,4 years. The surgical procedure was based on the developed technology and conducted by the same surgeon in the same clinical setting. The surgical technique included the installation of two ports in the opposite quadrants: in the upper hemisphere for the vitreotome and instruments, and in the lower hemisphere — for the infusion cannula with a built-in endo-illuminator-chandelier as a single light source. Then, vitrectomy was performed according to the classical technique — the vitreous body was removed centrally, followed by membrane staining and membrane peeling, and partial tamponade with an air mixture. Patients were examined on day 1, one and three months after the surgical procedure. They underwent the basic ophthalmic examination, including visometry and tonometry. Optical coherence tomography with retinal image analysis was used to assess the recovery of anatomical parameters. Results: intra- or postoperative adverse events were not reported. All patients had stable anatomical results: the absence of horizontal tractions in the foveal zone and a retinal height reduction to 297±32 μm. The maximum functional effect — a decrease in metamorphopsia expression and an increase in best-corrected visual acuity by 0.48±0.1 vs. that at the baseline was observed 3 months after the surgery. Conclusion: in addition to the classical three-port vitrectomy with xenon focal illuminator, it is possible to use the two-port vitrectomy with a mercury vapor chandelier illuminator. The advantage of this method is the reduction of surgical trauma. Keywords: epiretinal fibrosis, two-port vitrectomy, phototoxicity, tyndallometry. For citation: Borisova D.V., Frolychev I.A., Pozdeeva N.A. Prospects of two-port vitrectomy in the treatment of patients with epiretinal fibrosis. Russian Journal of Clinical Ophthalmology. 2022;22(4):224–227 (in Russ.). DOI: 10.32364/2311-7729-2022-22-4-224-227.

A disposable system for rapid purification of autologous plasmin as an adjunct to vitrectomy — performance and safety profile

The generation of an atraumatic posterior vitreous detachment (PVD), a common goal in vitreoretinal surgery, is a challenge particularly in children and young trauma patients. Plasmin has been proposed as a surgical adjunct to enzymatically generate a PVD. This study assesses the performance and safety of a new system for rapid purification of plasmin as an adjunct to vitrectomy. Plasminogen was isolated from human plasma by affinity chromatography using a disposable rapid purification kit, and activated to plasmin with streptokinase. Activities were assessed spectrophotometrically. For safety studies, 38 rabbits received intravitreal injections of one of the following compounds in 0.1 ml respectively: 4.7, 12.7 and 24 IU plasmin, 15 mg dextran, 4,100 U streptokinase, 500 μg ε-aminocaproic acid, 0.1 M potassium phosphate or balanced salt solution (BSS). Thirty min after injection, a two-port vitrectomy was performed. Rabbits were followed clinically and with bright flash electroretinography (ERG) for up to 9 months. The eyes were investigated by light and transmission electron microscopy. The specific plasmin activity obtained from blood of healthy volunteers averaged 42.3 ± 6.6 IU/ml (range 21.6 IU/ml to 54.5 IU/ml). The identity and purity of the enzyme was confirmed by several methods. Clinically, a mild to moderate inflammatory response was seen in most eyes on day 1, but had disappeared by day 7. ERG showed moderate depressions of a- and b-wave amplitudes on day 2, particularly in the potassium phosphate (a: -29.16 ± 4.56, b: -21.23 ± 6.31), 4.7 (a: -34.38 ± 6.64, b: -26.66 ± 6.06) and 24 IU (a: -38.25 ± 4.05, b: -23.38 ± 4.29) plasmin groups, but also in the BSS- (a: -11.19 ± 21.78, b: -11.41 ± 15.47) and dextran- (a: -17.86 ± 14.18, b: -6.67 ± 18.14) treated eyes. ERG changes recovered during follow-up. One rabbit each from the 12.7 and the 24 IU plasmin groups showed a minimal discoloration of one medullary ray after 9 months. Histology did not reveal morphologic signs of toxicity. The isolation system generated plasmin with a high degree of purity. A failure-mode analysis did not reveal significant risks of toxicity. A single preparation can provide a maximum dose of 10.9 IU/200 μl, the likely target clinical dose being 1.88 IU. Plasmin doses of at least 12.7 IU appear be safe when injected into rabbit eyes, followed by vitrectomy.

Safety profile of the intravitreal streptokinase-plasmin complex as an adjunct to vitrectomy in the rabbit

The generation of an atraumatic posterior vitreous detachment (PVD), a common goal in vitreoretinal surgery, is a challenge, particularly in children and young trauma patients. Plasmin has been proposed as an adjunct to vitrectomy to enzymatically generate a PVD. Low doses of streptokinase-activated plasmin were tested in human pilot studies. This dose-escalation study assesses the safety range of intravitreal human streptokinase-plasmin in rabbits. Plasminogen was isolated from human plasma by affinity chromatography, followed by activation with streptokinase (1:1), to generate the streptokinase-plasmin complex. Enzyme doses from 0.1-7 activity units (AU, in 0.1 ml) were injected into the mid-vitreous of 35 eyes; six control eyes were injected with balanced salt solution (BSS, 0.1 ml). Thirty minutes after injection, a two-port vitrectomy was performed. Fundus and slit lamp examinations were performed on days 1 and 7. On days 2 and 7, bright flash electroretinography was performed and compared with preoperative recordings. Some animals receiving higher doses of streptokinase-plasmin (1-7 AU) were followed clinically and with electroretinography for up to 9 months. A mild-to-moderate inflammatory response was seen in both control and plasmin-treated eyes on day 1, but had disappeared completely by day 7 in most eyes. In the 7 AU group, inflammation was stronger and more protracted. Two of three eyes from this group developed wrinkling of the medullary rays; one of them showed discoloration and traction at the medullary rays in the late follow-up. Electroretinograms (ERGs) of vitrectomized control eyes showed the following changes from preoperative values: 48 h, a-wave -11.10% [no significant (n.s.)], b-wave -14.62% (P=0.046); 7 days, a-wave +9.18% (n.s.), b wave +11.69% (n.s.). For the enzyme-treated eyes: 48 h: a-wave -20.43% (P<0.001), b-wave -9.57% (p<0.001); 7 days: a wave -14.21% (P<0.001), b-wave +2.48% (P<0.001). There was no evidence of dose-dependent ERG changes in enzyme-treated eyes at doses up to 5 AU. Groups of up to 3 AU were investigated by light and transmission electron microscopy, without evidence of toxicity. Streptokinase-plasmin doses up to 3 AU were found to be safe when injected into rabbit eyes followed by vitrectomy.

MfERG in normal and lesioned rabbit retina

To evaluate and describe the cone function in the normal and lesioned rabbit retina using the multifocal electroretinogram (mfERG). Twelve animals underwent a two-port vitrectomy with subsequent retinectomy in one eye. The area of removed retina was located in the nasal part of the visual streak, and measured approximately 1-2 disc diameters. Both eyes were investigated with mfERG preoperatively and up to 13 weeks postoperatively. A Burian-Allen bipolar contact lens with built-in infrared emitters was used to visualize the retina during the recordings. The averages of the trace array amplitudes in the lower nasal and temporal quadrants were calculated and statistically analyzed at the different time intervals. All eyes were examined histologically with hematoxylin and eosin staining. The retina could be visualized during the mfERG examinations. Postoperatively, up to 3 weeks, amplitudes were reduced over the entire stimulated area in retinectomized eyes (2.20 microV+/-1.22 SD) as compared with preoperative examinations (3.40 microV+/-1.00 SD). After 7 weeks the amplitudes in the quadrant including the retinectomized area remained low (2.62 microV+/-1.02 SD), whereas they were higher than at earlier postoperative examinations in the lower unlesioned temporal quadrant (3.56 microV+/-0.71 SD) with a statistical difference between the quadrants. At 13 weeks this was even more pronounced. In unoperated eyes, the area corresponding to the visual streak displayed significantly higher amplitudes than the area superior to the myelinated streak, corresponding well to the cone distribution. High amplitudes were also detected in the area of the myelinated nerve fibers and optic nerve head, most likely as a result of scattering light. In histological sections, the retinectomized area had a diameter of 1-3 mm. This study shows that the mfERG technique can be used as a tool in experimental retinal research involving the rabbit eye, where retinal lesions down to at least 1 mm can be detected. One difficulty involves scattering light emanating from the relatively large optic disc and the myelinated nerve fibers, which makes the use of a mfERG system, in which the fundus can be visualized during stimulation, mandatory.

Effects of indocyanine green injection on the retinal surface and into the subretinal space in rabbits.

To evaluate the effects of indocyanine green (ICG) injection on the retinal surface and into the subretinal space of rabbit eyes. Twenty-two Dutch-belted rabbits underwent two-port vitrectomy followed by injection of ICG (5 mg/mL) on the retinal surface and into the subretinal space. Balanced salt solution (BSS) was also injected subretinally. The locations where ICG was delivered (both epiretinal and subretinal) were exposed to light from an endoilluminator for 7 minutes. The animals were examined at 1, 7, and 14 days after surgery. The eyes were studied by fluorescein angiography as well as light and electron microscopy. No damage was observed after epiretinal ICG injection, but subretinal ICG injection resulted in damage to the outer nuclear layer, photoreceptor inner and outer segments, and retinal pigment epithelium. This damage was more severe with longer follow-up. Control experiments without ICG, in which balanced salt solution was injected into the subretinal space or light was delivered on the epiretinal surface, demonstrated only damage to the photoreceptor outer segments. Subretinal delivery of ICG (5 mg/mL) in rabbits induces retinal pigment epithelium, photoreceptor inner and outer segment, and outer nuclear layer damage. These mechanisms of damage may explain the retinal pigment epithelium changes that are sometimes seen after ICG-assisted internal limiting membrane peeling in humans.

Topical exposure of mitomycin C reduces opacification of the residual anterior lens capsule and lenticular regeneration after vitrectomy and lensectomy in rabbits.

To examine the effect of topical administration of mitomycin C (MMC) on the opacification of residual anterior lens capsule in a vitrectomized/lensectomized eye. Adult Japanese albino rabbits ( n=8) received two-port vitrectomy and lensectomy with or without topical administration of MMC (0.4 mg/ml) to the residual anterior lens capsule in one eye under both general and topical anesthesia. Four eyes after vitrectomy and lensectomy were exposed to MMC for 1 min and washed out with balanced salt solution. After 1 month, the anterior segment of each globe was observed with EAS-1000 in vivo under general anesthesia and then the enucleated globes were observed through the Miyake view. Histological examination was performed. During healing intervals in eyes without MMC exposure, regenerated lens structure of Soemmering's ring or fibrous tissue was formed in peripheral or central areas of the residual capsule, respectively. Both the anterior lens capsule opacification and lens fiber regeneration were statistically significantly reduced by MMC topical exposure. Lens epithelial cells produce regenerated lenticular structure and fibrous tissue on the residual capsule following vitrectomy and lensectomy in rabbits. Exposure of the residual anterior capsule to MMC may be effective in reducing both its opacification and lens fiber regeneration after vitrectomy/lensectomy.