Lens-sparing Vitrectomy Research Articles

Early Vitreous Surgery for Aggressive Posterior Retinopathy of Prematurity

To assess the efficacy of early vitrectomy for aggressive posterior retinopathy of prematurity (ROP) to stop progression of retinal detachment. Retrospective, noncomparative, consecutive case series. Twenty-two eyes (15 patients) with aggressive posterior ROP underwent vitrectomy with or without lens sparing, because retinal photocoagulation failed to stop progression of fibrovascular proliferation, despite being performed early, densely, and with early retreatment. We assessed the status of retinal attachment and foveal formation ophthalmoscopically and the presence or absence of fixation of visual behavior. Follow-up ranged from six to 12 months (mean, 9 months). Six eyes (100%) in which a lens-sparing vitrectomy was performed developed a large tractional retinal detachment. In contrast, the retinas were completely reattached in 16 eyes (100%) in which vitrectomy with lensectomy was performed, nine eyes (56%) had foveal configuration, and 14 eyes (88%) had steady fixation. These results suggest that early vitrectomy is effective for preventing retinal detachment in aggressive posterior ROP.

INTRASCHISIS CAVITY FLUID COMPOSITION IN CONGENITAL X-LINKED RETINOSCHISIS

To describe the intraschisis cavity protein composition in congenital X-linked retinoschisis (CXLRS) from two eyes of one child. 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. 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. 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.

ANATOMICAL SUCCESS RATE AFTER PRIMARY THREE-PORT LENS-SPARING VITRECTOMY IN STAGE 5 RETINOPATHY OF PREMATURITY

To assess the anatomical success rate after three-port lens-sparing vitrectomy (LSV) in stage 5 (total) retinal detachments secondary to retinopathy of prematurity. In a retrospective, interventional, single-surgeon, consecutive case series, the records of 33 eyes of 21 patients presenting with stage 5 retinal detachment secondary to retinopathy of prematurity who underwent primary three-port LSV from February 1998 to January 2004 were evaluated. Twenty-one eyes (63.6%) had open anteriorly-open posteriorly and 12 (36.4%) had open anteriorly-narrow posteriorly in terms of anatomical configuration. The main outcome measure, retinal reattachment, was reviewed at final follow-up visits, which ranged from 6 months to 48 months (mean, 32 months) after LSV. Fifteen eyes (45.5%) maintained attachment and 18 eyes (54.5%) remained detached at the final visit. Open anteriorly-open posteriorly configuration eyes had a statistically significant higher anatomical success rate than eyes with an open anteriorly-narrow posteriorly configuration (P<0.001). Three-port LSV may achieve anatomical success in stage 5 retinopathy of prematurity-related detachments. The open anteriorly-open posteriorly configuration portends a better prognosis; thus, surgery should be performed before closure of the posterior retina into a funnel configuration, if possible.

Visual Outcomes After 3-Port Lens-Sparing Vitrectomy in Stage 4 Retinopathy of Prematurity

To assess the visual acuity of eyes successfully treated with 3-port lens-sparing vitrectomy for stage 4 retinopathy of prematurity. Of 102 consecutive eyes achieving at least posterior pole reattachment, 30 eyes of 26 patients were tested by Teller or Allen acuity measurements and were subsequently converted to logarithm of the minimum angle of resolution (logMAR). Visual outcomes were also examined as either favorable or unfavorable (Snellen equivalent >20/200). Seventy-two eyes were not tested because of either inability to perform testing (age or neurologic sequelae related to prematurity) or loss of follow-up. Of those tested, mean +/- SD logMAR visual acuity for the stage 4A and stage 4B groups was 0.51 +/- 0.09 (Snellen approximate 20/62) and 1.03 +/- 0.19 (Snellen approximate 20/200), respectively (odds ratio, 0.39; 95% confidence interval, 0.24-0.64; P = .001). Of those eyes assessed by Teller measurements, 10 of 10 stage 4A eyes and 3 (37.5%) of 8 stage 4B eyes had favorable outcomes; among eyes assessed with Allen measurements, 4 of 4 stage 4A eyes and 0 of 8 stage 4B eyes had favorable outcomes. The majority of eyes were not tested. Among eyes tested after successful 3-port lens-sparing vitrectomy, some eyes treated prior to macular detachment may be associated with a more favorable outcome and improved maintenance of functional visual acuity.

Optical Coherence Tomography Findings in Stage 4A Retinopathy of Prematurity: A Theory for Visual Variability

To report macular anatomic abnormalities in eyes with stage 4A retinopathy of prematurity (ROP) that may account for poor visual outcome despite an ophthalmoscopically normal-appearing posterior pole. Retrospective case series. Nine patients (14 eyes). Nine patients (14 eyes) diagnosed with stage 4A retinal detachments were imaged with optical coherence tomography (OCT) before repair by lens-sparing pars plana vitrectomy. One patient (2 eyes) 2 years after successful lens-sparing vitrectomy for stage 4A detachment with reduced visual acuity underwent fluorescein angiography, fundus photography, and imaging with OCT. Optical coherence tomography findings. Preoperative OCT confirmed absence of macular involvement in 12 of 14 eyes. Two eyes demonstrated diffuse intraretinal posterior pole changes. Both eyes of a 2-year-old infant demonstrated a lack of normal foveal architecture on OCT scanning and an absent foveal avascular zone on angiography. Anatomic macular abnormalities--not immediately apparent ophthalmoscopically--may explain the variability in visual outcome after lens-sparing vitrectomy for stage 4A ROP.

Lens-sparing Vitrectomy for Stage 4 and Stage 5 Retinopathy of Prematurity

PurposeTo describe the results of lens-sparing vitrectomy for the correction of retinal detachment associated with retinopathy of prematurity (ROP) and its associated complications.MethodsSeventeen patients who underwent a lens-sparing vitrectomy for stage 4 and stage 5 ROP with plus disease at Seoul National University Children's Hospital between 1999 and 2003 were enrolled in this study. The patients who had bilateral retinal detachment of ROP underwent a lens-sparing vitrectomy in one eye and a scleral buckling surgery or lensectomy-vitrectomy in the other eye. The patients who had a retinal detachment in one eye and a regressed ROP in the other eye underwent unilateral lens-sparing vitrectomies. A review of their preoperative clinical findings (including the status of retinal detachment and plus disease), post-operative results, and any complications encountered was performed.ResultsIn 17 patients, the postoperative success rate of lens-sparing vitrectomy was 58.8%. However, lens-sparing vitrectomy as a treatment for stage 5 ROP (25.0%) produced more negative post-operative results than it did when used to treat either those for stage 4a (75,0%) or 4b (66.7%) ROP. Among the 10 eyes in which the retina was attached, form vision was shown in six eyes, light could be followed by three eyes, and no light perception was present in one eye. Intra- and post-operative complications included retinal break formation, cataracts, vitreous hemorrhages, and glaucoma in patients with stages 4b and stage 5 ROP.ConclusionsLens-sparing vitrectomy resulted in encouraging surgical outcomes in the correction of retinal detachment of ROP, especially in stage 4 patients. Therefore, a lens-sparing vitrectomy for stage 4 ROP patient may be beneficial, although it is still associated with some intra- and post-operative complications.

Lens Clarity After 3-Port Lens-Sparing Vitrectomy in Stage 4A and 4B Retinal Detachments Secondary to Retinopathy of Prematurity

To assess lens clarity after 3-port lens-sparing vitrectomy for stages 4A and 4B tractional retinal detachment secondary to retinopathy of prematurity. In a retrospective, interventional, consecutive clinical case series, 108 eyes of 102 patients who underwent lens-sparing vitrectomy for stages 4A and 4B tractional retinal detachment from February 1, 1998, through January 31, 2004, were reviewed. All procedures and follow-up examinations were performed by a single surgeon. Lens clarity was assessed at the final follow-up examination. Of the 108 eyes reviewed, 102 (94.4%) maintained clear lenses at the final follow-up examination, which ranged from 6 to 48 months (mean, 32 months) after the procedure. Thirty-two eyes had stage 4A detachments and 76 eyes had stage 4B. Three-port lens-sparing vitrectomy may be performed with relatively low risk of cataract formation during the early postoperative period. Maintenance of a clear crystalline lens during the critical period of visual development may lead to better functional outcomes.

PERFLUORO-N-OCTANE AS A POSTOPERATIVE VITREORETINAL TAMPONADE IN THE MANAGEMENT OF GIANT RETINAL TEARS

Despite recent advances in giant retinal tear repair, retinal redetachment remains an issue. This may be due to inadequate retinal tamponade with silicone oil or perfluorocarbon gas that allows fluid to seep back under the edge of the tear. We propose short-term postoperative retinal tamponade with perfluoro-n-octane liquid to overcome this problem. Theoretical advantages include the reduced likelihood of proliferative vitreoretinopathy. It is easier to remove than silicone oil due to its lower viscosity, and supine posturing is more manageable from a patient perspective. A retrospective case series of 16 giant retinal tear repairs without significant proliferative vitreoretinopathy is presented. Lens-sparing vitrectomy was performed with endolaser to the edge of the tear and the entire retinal periphery. Scleral buckling was not utilized. Perfluoro-n-octane was used as a postoperative tamponade for a mean of 16.4 days (range, 6-50 days). The retina was reattached at the end of the procedure in all 16 cases. Redetachment occurred in only 1 (6.3%) of 16 cases. Postoperative tamponade with perfluoro-n-octane may decrease the rate of redetachment in giant retinal tear repair compared with silicone oil or perfluorocarbon gas alone. We found no adverse effects directly attributable to perfluoro-n-octane.

Anatomic Success Rate after 3-Port Lens-Sparing Vitrectomy in Stage 4A or 4B Retinopathy of Prematurity

To assess the anatomic success rate after 3-port lens-sparing vitrectomy (LSV) in stage 4A and 4B tractional retinal detachments (TRDs) due to retinopathy of prematurity (ROP). A chart review and data evaluation of 108 eyes of 102 consecutive patients presenting with stage 4A (32 eyes) or 4B (76 eyes) TRDs that underwent primary LSV from February 1998 to January 2004 were performed. Three-port LSV was performed on all eyes by the same surgeon (ERH). Retinal reattachment status was reviewed at final follow-up visit, which ranged from 6 to 48 months (mean, 32 months) after LSV. Ninety-two of 108 (85.2%) eyes were reattached after a single LSV and 102 of 108 (94.4%) eyes ultimately achieved at least partial posterior pole reattachment at the final follow-up visit. All 4A eyes achieved complete reattachment and 70 of 76 (92.1%) 4B eyes achieved partial or complete reattachment. Reversal or complete arrest of dragging of the macula was noted in all eyes that maintained partial or complete reattachment (94.4%). Six (5.6%) 4B eyes remained detached despite additional vitreoretinal procedures; 4 (66.7%) of these had intraoperative retinal tears. Eighty-five percent of eyes with 4A and 4B TRDs secondary to ROP were completely reattached with a single 3-port LSV procedure and nearly 95% were ultimately at least partially reattached at the posterior pole by the final follow-up visit. The development of retinal tears intraoperatively portended a poor prognosis for reattachment.

Lens-Sparing Vitrectomy for Progressive Tractional Retinal DetachmentsAssociated With Stage 4A Retinopathy of Prematurity

To describe the results of lens-sparing vitrectomy in infants with progressive, fovea-threatening, tractional retinal detachments associated with stage 4A retinopathy of prematurity. In a retrospective, interventional, consecutive clinical case series, the records of patients with stage 4A retinopathy of prematurity who underwent lens-sparing vitrectomy for progressive retinal detachments were reviewed. Retinal attachment status, reversed or arrested retinal dragging, and visual acuity were assessed after the procedure. Thirty-two eyes of 29 patients underwent lens-sparing vitrectomy at a mean postconceptional age of 43 weeks. Thirty (94%) of 32 eyes had complete retinal reattachment and arrest or reversal of retinal dragging after 1 lens-sparing vitrectomy. Visual acuity of at least central, steady, and unmaintained was observed in 17 (81%) of the 21 eyes in which it was tested and at least central, steady, and maintained vision was measured in 13 (62%) of 21 eyes, with 1 eye achieving 20/40 visual acuity. Lens-sparing vitrectomy is a safe and effective procedure for the treatment of fovea-threatening retinal detachments in patients with stage 4A retinopathy of prematurity.

Visual outcomes after lens-sparing vitrectomy for stage 4A retinopathy of prematurity

To assess the visual outcomes of patients with stage 4A retinal detachments (RDs) from retinopathy of prematurity (ROP). Retrospective review of a consecutive case series of children referred to the pediatric retina service of Associated Retinal Consultants, Royal Oak, Michigan. Forty-five eyes of 39 children. The stage of RD for each patient was determined during an examination under anesthesia. All patients underwent a lens-sparing pars plana vitrectomy (PPV) with membrane peeling. Postoperative anatomic status was determined by ophthalmoscopy either during an office examination or during an examination under anesthesia. Visual outcomes were ascertained by consulting pediatric ophthalmologists using either Teller or Allen acuities. Anatomic and visual outcomes. Formalized visual acuity (VA) measurement was performed in 23 eyes of 20 children, and was not performed in 22 eyes of 19 children. All 23 eyes that were formally tested had successful retinal reattachment. The macula appeared to be normal and without distortion in 19 of 23 eyes (83%) during the follow-up period. Average logarithm of the minimum angle of resolution VA was 20/58. Three eyes had acuities of 20/200, and 4 had acuities of 20/100. All other eyes were 20/80 or better. Average age at time of VA was 3.51 years. Patients with ROP and stage 4A RDs can be treated successfully with respect to anatomic and visual outcome utilizing lens-sparing PPV.

Lens-sparing vitrectomy for stage 4 retinopathy of prematurity

To investigate the anatomic results of lens-sparing vitrectomy for tractional stage 4 retinopathy of prematurity (ROP). Retrospective, noncomparative consecutive case series. Thirty-seven eyes (24 patients) with tractional stage 4 ROP. Lens-sparing vitrectomy. Anatomic status of the retina. Twenty-five eyes had stage 4A ROP, and 12 eyes had stage 4B ROP. With a median follow-up of 13 months (range, 6-27), 32 of 37 eyes (86%) had complete reattachment of the retina. Among eyes with 4A ROP, 21 of 25 eyes (84%) had complete retinal reattachment. Among eyes with 4B ROP, 11 of 12 eyes (92%) had complete retinal reattachment. At last follow-up, 29 of 37 eyes (78%) were able to fix and follow. These results indicate that lens-sparing vitrectomy is effective for achieving retinal reattachment in tractional stage 4 ROP. This article contains additional online-only material available at .

COMPARISON OF RETINAL OUTCOMES AFTER SCLERAL BUCKLE OR LENS-SPARING VITRECTOMY FOR STAGE 4 RETINOPATHY OF PREMATURITY

To compare anatomic outcomes after lens-sparing vitrectomy (LSV) or scleral buckle (SB) for stage 4 retinopathy of prematurity (ROP). Nonrandomized, retrospective study of infants consecutively treated for stage 4 ROP by LSV or SB. Outcomes were retinal attachment at 1 month of initial surgery and at the end of follow-up (6 months) and number of procedures to achieve retinal attachment. Exact chi2 methods determined significance, and student's t-test compared mean postmenstrual age and birthweight between the groups. After one procedure, LSV (72%) was associated with retinal attachment more often than was SB (31%). At the end of follow-up, after one or more procedures, there was no difference in retinal reattachment rate between LSV or SB as the first procedure. There were no differences between the surgical groups by mean postmenstrual age and birthweight or severity of ROP determined by zone, clock hours of ridge elevation, or quadrants of plus disease. This study supports the hypothesis that vitrectomy by LSV stops progressive stage 4 ROP. As an initial procedure, LSV was associated with retinal attachment more often than SB. Future prospective studies can determine the effects of LSV and SB on visual development in progressive stage 4 ROP.

Lens-sparing vitrectomy in predominantly posterior persistent fetal vasculature syndrome in eyes with nonaxial lens opacification.

To determine indications and document anatomic and functional outcomes for lens-sparing vitreous surgery in eyes with predominantly posterior persistent fetal vasculature syndrome and nonaxial lens opacification. Retrospective interventional clinical series. The authors performed lens-sparing vitreous surgery on nine eyes of infants with predominantly posterior persistent fetal vasculature syndrome and nonaxial lens opacification without removing the crystalline lens. Indications for surgery included primarily posterior complications of persistent fetal vasculature syndrome (localized tractional retinal detachment), a centrally clear lenticular axis, and frequently strabismus. Postoperatively, seven of nine eyes showed no evidence of increasing lens opacification with a median follow-up period of 16.8 months (range, 5-29 months). The first eye operated on developed a rapidly progressive cataract and prompted modification of the surgical technique. One additional eye also required cataract extraction for progressive lenticular opacification 23 months after surgery. No eyes developed postoperative retinal detachment, and all eyes maintained vision at the final follow-up. Of the seven eyes with strabismus, five improved after vitreous surgery alone, and two required additional strabismus surgery. This series shows that, in selected cases of persistent fetal vasculature syndrome that are predominantly posterior in nature with nonaxial lens opacification, lens-sparing vitrectomy can be of benefit.

Features associated with surgical outcome in patients with stages 4 and 5 retinopathy of prematurity.

To present ocular features associated with surgical outcomes in infants with stages 4 and 5 retinopathy of prematurity (ROP). Twenty-two infants (35 eyes) were referred for vitreoretinal surgery for stages 4 and 5 ROP. The following ocular features recorded before the development of retinal detachment requiring surgical intervention were analyzed: clock hour extent of ridge elevation, vitreous state, plus disease, prominent iris vessels, neovascularization, and the presence of exudates. Surgical procedures included scleral buckle, lensectomy-vitrectomy, and lens-sparing vitrectomy. Univariate and multivariate analyses were used to determine features associated with failure to achieve retinal reattachment as the main outcome variable. Of the 35 eyes that underwent at least one surgical procedure, nine had successful retinal reattachment after the first surgery, and 18 achieved it at the end of follow-up. After accounting for the correlation between the eyes, features significantly associated with surgical failure after the first surgery were vitreous haze, hemorrhage, or organization; plus disease; and neovascularization. The presence of exudates was significantly associated with a successful outcome. When eyes were analyzed by stage at the first procedure, vitreous organization and plus disease were associated with failed retinal reattachment in stage 4 eyes, whereas at least 6 clock hours of ridge elevation and plus disease were significant in stage 5 eyes. The need to perform a lensectomy-vitrectomy was associated with a poor surgical outcome. Neither stage nor number of procedures performed was associated with the development of phthisis. Vitreous haze, neovascularization, and plus disease are associated with a poor surgical outcome in eyes that progress after treatment for threshold ROP requiring surgical intervention for retinal detachment. When eyes were divided by stage of ROP at first surgery, plus disease remained a significant variable associated with failed retinal reattachment. Close observation of eyes after laser treatment for threshold ROP is necessary. If neovascularization and plus disease persist and progression of ROP is noted, additional laser should be considered before surgery for retinal detachment. Additional studies with a larger patient sample will be necessary to further define ocular features associated with surgical outcome for ROP.

Axial myopia associated with dense vitreous hemorrhage of the neonate

Background: Various forms of visual deprivation during infancy have been shown to cause axial myopia. Although infantile vitreous hemorrhage is associated with myopic progression, it is unknown whether this aberrant development is refractive or axial. The primary objectives of this study were to investigate this abnormal myopic development and to determine what duration of dense vitreous hemorrhage is sufficient to cause significant amblyopia in neonates. Methods: Four infants with dense unilateral vitreous hemorrhages in the first weeks of life underwent serial evaluations of the posterior segment, refractive error, and A-scan ultrasonography. Results: Three of the 4 infants underwent successful lens-sparing vitrectomy between 3 and 6 weeks after the onset of the hemorrhage, and all 3 developed axial myopia and dense amblyopia during a mean follow-up of 29.7 months (range, 16 to 38 months). At the most recent follow-up examination, the mean myopic error of the 3 eyes that required surgery was −11.42 D with a mean ocular axial length difference of 3.45 mm between the affected and the unaffected eyes. The fourth child had a dense hemorrhage soon after birth that cleared by 11 days of age. Although this patient developed amblyopia and a mild myopic error of the involved eye, there was no significant increase in axial length. Conclusions: Dense hemorrhages persisting in the neonatal vitreous for 4 weeks or longer appear to cause axial myopia and severe amblyopia. Surgical intervention before this time should be considered to avert deprivation amblyopia and to retard axial myopia. (J AAPOS 2002;6:348-53)

Lens-sparing vitreous surgery for tractional stage 4A retinopathy of prematurity retinal detachments

Purpose To assess the efficacy of lens-sparing vitrectomy in tractional 4A retinopathy of prematurity (ROP) retinal detachments in reducing progression to stage 4B or 5 ROP. Design Retrospective, noncomparative consecutive case series. Participants Forty eyes (31 patients) with stage 4A ROP at 38 to 42 weeks post-conceptional age. Intervention Lens-sparing vitrectomy. Main outcome measures Retinal attachment status and presence/absence of fixation behavior. Results The range of follow-up was 6 to 22 months (mean, 12 months). Ninety percent (36 of 40) of eyes showed retinal reattachment and fixation behavior at their last follow-up visit. Conclusions These results suggest that vitreous surgery can interrupt progression of ROP from stage 4A to stages 4B or 5.

Avoidance and treatment of retinopathy of prematurity.

Retinopathy of prematurity is a blinding eye disease of premature infants. It is increasing in incidence as more babies of lower birth weights survive. Although in the 1940s and 1950s the major predisposing factor was high oxygen exposure, the main risk factor now is birth weight less than 1,000 g. Retinopathy of prematurity can be classified into several distinct stages, which progress in a typical manner. Once the stage of threshold is reached, the eye has a 50% chance of becoming blind. At this stage, laser peripheral retinal photo ablation or peripheral cryo ablation may cause the neovascularization to regress and preserve vision. The treatment is not effective in all cases, however, and a large number of children continue to become blind each year because of this devastating disease. New microsurgical techniques such as lens-sparing vitrectomy and modified scleral buckle for tiny eyes have improved the outcome for some children. Prevention is the best hope to eradicate blindness caused by this disorder, and manipulations of the metabolic and neonatal intensive care unit environment are currently being studied.

Lens Clarity after Lens-sparing Vitrectomy in a Pediatric Population

Purpose: The purpose of the study is to assess lens clarity after pediatric lenssparing vitrectomy.Methods: The study offers a retrospective analysis of 85 eyes of 77 pediatric patients who underwent lens-sparing vitrectomy for tractional retinal detachment or opaque media, and who were observed for 10 to 55 months.Results: A total of 57 eyes maintained clear lenses at last follow-up examination. Cataract was found in 13 (15%) of the 85 eyes. Fifteen eyes (18%) had undergone lens removal as part of reoperation for progressive ocular disease.Conclusion: Sixty-seven percent of pediatric lenses remained clear after lens-sparing vitrectomy.

Lens-sparing Vitrectomy with Perfluorocarbon Liquid for the Primary Treatment of Giant Retinal Tears

To evaluate the surgical success of vitrectomy without initial lensectomy in the primary treatment of retinal detachment associated with giant tears without proliferative vitreoretinopathy. Thirty-four consecutive phakic eyes with idiopathic giant retinal tears underwent vitrectomy, injection of perfluorocarbon liquid, endolaser, and gas tamponade. Encircling scleral buckling was performed in 14 of 34 patients. Preoperative visual acuity ranged from 20/25 to hand motions. Giant tear size ranged from 90 degrees to 330 degrees. Follow-up ranged from 10 to 64 months. Anatomic retinal re-attachment was achieved intraoperatively in all eyes. The re-operation rate was 14% for eyes that underwent scleral buckling with the initial vitrectomy and 45% in eyes without primary scleral buckling. In 59% of eyes with cataract formation, 32% underwent cataract surgery with or without intraocular lens implantation. Best-corrected final visual acuity ranged from 20/15 to 20/400. Most phakic eyes with giant retinal tear not associated with proliferative vitreoretinopathy can be re-attached successfully with initial preservation of the lens.