Intraocular fluid dynamics and retinal shear stress after vitrectomy and gas tamponade.

PURPOSE: To evaluate fluid dynamics and fluid shear stress on the retinal wall in a model eye after vitrectomy and gas tamponade in relation to saccadic eye movements and sudden head movements and to correlate the results with gas fill fraction (GF). Methods. Analyses was undertaken using high-resolution computational fluid dynamic software. The fluid volume within the eye was discretized using 6 × 10(5) elements and solved with a volume-of-fluid METHOD: The eye was abstracted to a sphere. Vertical and horizontal saccades and sudden rectilinear displacement of the head were examined. GF was varied from 20% to 80% of the eye height filled with gas. RESULTS: Maximum shear stress during horizontal and vertical saccades was 1.0 Pa (Pascal) and 2.5 Pa, respectively, and was dependent on GF. Rapid rectilinear acceleration of the head caused a maximum shear stress of 16 Pa, largely independent of GF. Fluid sloshing within the eye decayed within 0.1 second. Stresses were maximum at the contact line and equator of the eye and were parallel to the direction of motion. CONCLUSIONS: This study predicts that saccadic eye movements and normal head movements after vitrectomy and gas tamponade generate only small fluid shear stresses on the retina that are below published norms for retinal adhesion strength. Sudden, jerking head movements generate fluid shear forces similar to retinal adhesion strength that localize to the area of gas-fluid interface. Fluid sloshing occurs after movement, but rapidly decays on cessation of movement. These results suggest that restrictive posturing after vitrectomy and gas tamponade may be unnecessary. Patients should avoid sudden head movements.

A theoretical model for predicting interfacial relationships of retinal tamponades.

Purpose. To establish a theoretical model to determine the relationship between retinal coverage and tamponade shape in relation to tamponade volume, for a variety of tamponades, and to test these relationships with a physical analogue of the human eye. Methods. The theoretical model was based on a static balance between buoyancy forces and surface tension forces, for an axisymmetrically shaped bubble or droplet. In the laboratory experiments, two hemispheres were cut into an acrylic block. The acrylic was soaked with bovine serum for 10 minutes to ensure that the wetting properties were similar to the human retina. Photographic images of various fractions of lighter-than-water (gas, silicone) and heavier-than-water (Oxane HD) tamponades were analyzed by using algorithms written in commercial image-processing software and compared with the theoretical predictions and published data. Results. The theoretical predictions of tamponade shape and retinal coverage agree closely with the results obtained from the analogue experiments. Conclusions. The theoretical model was validated against measurements in a human eye analogue and published data. The three key parameters that characterize the retinal coverage of any given tamponade are the bond number, the contact angle of the tamponade, and the volume used. The model may be used to predict the static properties of new tamponades without in vivo tests.

Long-term visual and microperimetry outcomes following autologous retinal pigment epithelium choroid graft for neovascular age-related macular degeneration.

BACKGROUND: To describe the 2- to 4-year visual and microperimetry outcomes of autologous retinal pigment epithelium (RPE)-choroid graft in patients with neovascular age-related macular degeneration (AMD). METHODS: In this retrospective cohort study, 12 patients with subfoveal neovascular AMD who had undergone autologous RPE-choroid graft between August 2004 and June 2005 were reviewed. Change in visual acuity (VA), contrast sensitivity (CS), fixation stability and retinal sensitivity on microperimetry after 2-3 years and the rates of late postoperative complications were examined. RESULTS: Patients were followed for 26-48 months (mean, 39). Median preoperative VA (logMAR) was 0.87 but declined to 1.43 (1 year), 1.46 (2 years) and 1.38 (3 years), P = 0.001. Median CS (logCS) was 0.75 preoperatively but declined to 0.45 at 2 years. Six patients had serial microperimetry. Fixation stability declined in 1 but improved in 2 patients. All 6 had decline in retinal sensitivity over the graft during follow up. Retinal detachment did not occur after 12 months but 8 developed epiretinal membrane, 12 had cystic retinal change over the graft and 4 developed recurrent choroidal neovascularization. However, 10 grafts retained autofluorescence signal at 18-48 months of follow up. CONCLUSIONS: Autologous RPE-choroid graft can maintain VA, stable fixation and retinal sensitivity in some patients for over 3 years. The spatial correlation between graft autofluorescence, outer retinal structures on optical coherence tomography and retinal sensitivity are consistent with photoreceptor cell rescue. However, we caution the use of this technique as there is high complication rate and delayed loss of retinal function.

Dye extrusion technique (DE-TECH): occult retinal break detection with subretinal dye extrusion during vitrectomy for retinal detachment repair.

OBJECTIVE: To investigate the effectiveness of a new technique for the identification of occult retinal breaks in vitrectomy retinal detachment repair. Dye Extrusion Technique involves injection of sub retinal dye and extrusion through the unidentified breaks using perfluorocarbon liquid. METHOD: Retrospective case note analysis. MAIN OUTCOME MEASURES: rate of break detection, rate of use of local retinopexy, and short-term gas tamponade alone; SECONDARY OUTCOMES: anatomical success at 3 months with no long-term tamponade, final visual acuity, progression of proliferative vitreoretinopathy. RESULTS: Thirty-eight percent of eyes had proliferative vitreoretinopathy of grade C1 or worse. Twenty-five percent underwent primary retinal detachment repair surgery. The remainder underwent repeat operations for previously failed surgery. Breaks were found in 89% of eyes and 81% underwent only local retinopexy and gas tamponade. The overall anatomical success rate was 85% (40/47) which included four cases in which the retina was fully attached awaiting removal of silicone oil. No cases had unexplained loss of vision. No progression of proliferative vitreoretinopathy was noted. CONCLUSIONS: Results suggest that Dye Extrusion Technique may be an effective technique for the identification of occult retinal breaks and may facilitate simple techniques of detachment repair. No evidence of retino-toxicity from the use of trypan blue was found but the study had limited power to detect adverse effects.

A comparison of macular translocation with patch graft in neovascular age-related macular degeneration.

PURPOSE: To compare the long-term outcomes of macular translocation (MT) and autologous RPE-choroid patch graft (PG) in patients with neovascular age-related macular degeneration (AMD). METHODS: This is a retrospective review of the first 12 patients who underwent MT and the first 12 patients who underwent PG. Visual acuity (VA), contrast sensitivity (CS), clinical findings, and complications were recorded. Microperimetry and fundus imaging were reviewed. Outcome measures were the change in VA and CS over 3 years in each group and rates of complication. Microperimetry and fixation in three best cases from each group were described. RESULTS: The two groups were matched for age and VA. Median follow-up durations were 41 (MT) and 38 (PG) months. Median VA (logMAR) was maintained in the MT group: 0.90 at baseline and 0.69 at 3 years (P=0.09) whereas in the PG group, median VA declined from 0.87 to 1.38 at 3 years (P<0.001). Both surgical modalities had high rates of detachment and macular edema. Although more extensive RPE damage occurred in PG, the graft resisted growth of recurrent choroidal neovascularization toward the fovea. Near normal VA was achievable by each technique but macular sensitivity and fixation stability were superior in the MT group. CONCLUSIONS: In the present cohort, MT maintained VA for 3 years but PG did not. This outcome may be related to the differences in surgical approach, source of RPE, and choroidal perfusion. The authors recommend MT in preference to PG for treatment of patients with the second eye affected by neovascular AMD unsuitable for other treatment.

Prophylaxis for retinal detachment: evidence or eminence based?

PURPOSE: Prophylactic laser treatment of peripheral retinal lesions to prevent retinal detachment enjoys widespread use. However, clinical and scientific evidence for such treatment only exists for a few particular clinical situations. The aim of the present study was to delineate the current practice patterns for such prophylaxis among some European retinal specialists. METHODS: A postal survey was conducted among all members of BEAVRS (British and Eire Association of Vitreoretinal Surgeons; n = 236), all members of the German Retinological Society (n = 396), and Swiss retinal surgeons (n = 12) using a questionnaire with 6 case scenarios. The retinal specialists were asked to choose between three different options for each case: treat retinal lesion prophylactically, clinical follow-up, and other options. RESULTS: The return rates of the questionnaire were 36% in the United Kingdom, 42% in Germany, and 83% in Switzerland. There was a general tendency to apply laser prophylaxis to peripheral retinal lesions despite the absence of evidence in the medical literature. CONCLUSIONS: Nonevidence-based prophylactic laser treatment of peripheral retinal lesions remains a clinical and economic issue that must be addressed, and more evidence-based data are needed to establish clear clinical guidelines. Swiss retinal specialists are particularly conscientious in sending back a medical questionnaire.

Two-year results of surgical removal of choroidal neovascular membranes related to non-age-related macular degeneration.

PURPOSE: To present the 2-year outcomes of surgical removal of non-age-related macular degeneration (AMD)-related choroidal neovascular membranes and to evaluate any association between visual outcome and baseline clinical factors. METHODS: Retrospective consecutive case series. All patients who had surgery for non-AMD-related choroidal neovascularisation (CNV) between November 1997 and March 2003 under the care of a single surgeon (WA) were included in the study. Baseline data including patient age, duration of subfoveal CNV, preoperative visual acuity (VA), lesion size, lesion components and aetiology were collected. The primary outcome was VA change with secondary outcomes retinal detachment, operative peripheral retinal break formation, CNV recurrence and cataract. RESULTS: A total of 52 eyes were included in the study. The aetiology of CNV was: punctate inner choridopathy 21 (40%); idiopathic 8 (15%); pathologic myopia 6 (12%); ocular histoplasmosis syndrome 1 (2%); and other 16 (31%). The mean age of patients was 41(range 14-72) years. 24-month follow-up was available for 41 (80%) eyes. The mean logMAR equivalent baseline acuity was 1.1 and mean lesion size 1.2 disc areas. An improvement in VA >1 Snellen line was noted in 26 (63%) eyes, whereas 10 (24%) eyes remained the same (within 1 line) and 5 (12%) lost >1 line of acuity. Improvement in VA was associated with worse baseline VA (84% for eyes with VA 6/36, p=0.001). No evidence of association between 2-year visual outcome and any other baseline factor under study was observed. Peripheral retinal breaks were noted in 5 (10%) eyes at the time of surgery, and 3 (5.8%) eyes developed postoperative retinal detachments. Persistent/recurrent CNV was noted in 17 (33%) eyes. The median time to presentation of CNV in these eyes was 27 (range 2-172) weeks. Five eyes underwent cataract surgery during the follow-up period. The mean age of these patients was significantly higher than the mean age of those who did not require cataract surgery (57 vs 37 years, p=0.014). CONCLUSIONS: Surgical excision of non-AMD-related CNV resulted in improvement of VA in the majority of eyes. Worse presenting acuity was associated with better visual improvements.

Autologous transplantation of the retinal pigment epithelium and choroid in the treatment of neovascular age-related macular degeneration.

PURPOSE: To assess excision of choroidal new vessels (CNV) combined with autologous transplantation of the equatorial retinal pigment epithelium (RPE) as a means of restoring vision for patients with acute neovascular age-related macular degeneration (AMD). DESIGN: Prospective interventional cohort study. PARTICIPANTS: Twelve patients were recruited into an ethics committee approved trial with informed consent between 2004 and 2005. All had <6 months of acute visual loss owing to subfoveal neovascular AMD and were ineligible for photodynamic therapy. METHODS: Patients underwent submacular removal of CNV through a single retinotomy. A full-thickness patch graft of RPE, Bruch's membrane, and choroid was harvested from the superior equatorial retina and transplanted into the subfoveal space. The graft was flattened under heavy liquid, before silicone oil exchange. Removal of silicone oil and cataract surgery were performed 3 months later. All patients underwent cataract grading, full refraction, optical coherence tomography, fundus autofluorescence, and fluorescein and indocyanine angiography preoperatively and again 6 months postoperatively. Retinal pigment epithelium samples from 3 patients were tested for ex vivo gene transfer using a recombinant lentiviral vector. MAIN OUTCOME MEASURES: Six months after surgery, successful transplantation was determined by the presence of a pigmented subfoveal graft showing RPE autofluorescence and choroidal reperfusion. Visual outcome was assessed by subjective refraction and microperimetry of the retina overlying the graft. RESULTS: Successful viable grafts were seen in 11 patients. Three patients had good visual function on the grafts, with mean logarithm of the minimum angle of resolution (logMAR) improving from 0.88 to 0.79 and maintained beyond 1 year. Operative complications occurred in 8 patients, including retinal detachment in 5 patients and hemorrhage affecting the graft in 4 patients. The mean visual acuity over the whole cohort fell from logMAR 0.82 to 1.16. The excised RPE choroid could also be genetically modified outside the eye with a viral vector applied within the time frame of the operation. CONCLUSIONS: Autologous RPE transplantation can in principle restore vision in neovascular AMD, but surgical complications remain high. The possibility for ex vivo gene transfer to the free graft of RPE may widen the scope of this procedure to include gene therapy or adjunctive molecular treatments for AMD.

Intraretinal and periretinal pathology in anterior proliferative vitreoretinopathy.

OBJECTIVES: To determine the intraretinal and periretinal pathological changes in early anterior proliferative vitreoretinopathy (APVR). DESIGN: Observational case series. PARTICIPANTS: Eighteen patients undergoing retinectomy for APVR. METHODS: Retinectomy specimens removed at vitrectomy surgery were analysed by (a) semithin light microscopy, (b) immunohistochemistry and (c) electron microscopy. RESULTS: The specimens showed consistent outer retinal degenerative changes, marked Muller cell hypertrophy and glial continuity to epiretinal membranes. Photoreceptor outer and inner segments were markedly disrupted and occasional photoreceptor nuclear had pyknosis and chromatin clumping consistent with apoptosis. Muller cells expressed upregulated levels of glial fibrillary acid protein (GFAP) and extended through glial bridges to complex epiretinal membranes which in some areas had a bilaminar structure with a glial-negative inner lamina. CONCLUSION: Retinal degeneration and photoreceptor apoptosis occur in retinal detachment complicated by proliferative vitreoretinopathy (PVR), although during the early stages of the process neural retinal cells remain present, suggesting potential for recovery. The intraretinal glial response appears to be centrally involved in the formation of contractile epiretinal membranes. The retina retains the capacity for a degree of functional recovery following surgery for PVR. Surgical separation of anterior epiretinal membranes in PVR may be difficult and incomplete and alternative surgical strategies may be necessary to prevent recurrence.

Long-term results of submacular surgery combined with macular translocation of the retinal pigment epithelium in neovascular age-related macular degeneration.

PURPOSE: To provide long-term (> or =5 years) follow-up data on patients who had previously undergone macular retinal pigment epithelium (RPE) translocation surgery for choroidal new vessels (CNVs) associated with age-related macular degeneration. DESIGN: Retrospective interventional case series. PARTICIPANTS: Four of 9 patients who originally underwent surgery and whose results were reported after 2 years of follow-up were reviewed again 5 to 6 years after surgery. METHODS: All surviving patients from the original trial were contacted, and those who consented to full ocular examination were called in for review. Examination included best-corrected visual acuity (VA), optical coherence tomography (OCT), fundus autofluorescence, fluorescein angiography (FA), and indocyanine green angiography. MAIN OUTCOME MEASURES: Long-term success of RPE translocation was assessed by VA, imaging, angiography, and maintenance of overlying foveal fixation. Comparisons were made to the original 2-year follow-up data previously published. RESULTS: Over the long term, VA had declined further in 3 patients and improved slightly in 1 patient. Significantly, all 4 patients had lost foveal fixation and autofluorescence of translocated RPE, which had been present at the original 2-year follow-up assessment. The RPE graft, however, seemed viable when assessed by OCT, FA, and indocyanine green angiography, and no patient had suffered a recurrence of CNVs. CONCLUSIONS: In these 4 patients, RPE choroidal grafts had survived in the subfoveal space for at least 5 to 6 years, but rescue of visual function had been transient. The long-term loss of foveal fixation and graft autofluorescence might be explained by chronic photoreceptor apoptosis, initiated by either surgery or the disease process itself. Caution should be applied when drawing firm conclusions from similar studies that provide data after only 2 years' follow-up.

A randomized controlled trial of combined 5-fluorouracil and low-molecular-weight heparin in management of established proliferative vitreoretinopathy.

OBJECTIVE: To determine the efficacy of a combination of 5-fluorouracil and low-molecular-weight heparin (LMWH) to improve the outcome of surgery for established proliferative vitreoretinopathy (PVR). DESIGN: Double-masked, prospective, randomized, placebo-controlled clinical trial. SETTING: Three tertiary-referral teaching hospital vitreoretinal surgical units. PATIENTS: One hundred fifty-seven patients with established PVR (grade C, anterior or posterior) undergoing vitrectomy surgery. INTERVENTION: All patients underwent vitreoretinal surgery and silicone oil exchange with or without membrane peeling and/or retinectomy. Patients were randomly allocated to perioperative infusion with or without 5-fluorouracil (200 microg/ml) and LMWH (5 IU/ml) in Hartmann's solution for 1 hour. OUTCOME MEASURES: The primary outcome measure was defined as posterior retinal reattachment after removal of silicone oil without any reoperations at 6 months. Secondary outcome measures recorded were posterior retinal reattachment, localized/tractional retinal detachment, visual acuity, macular pucker, hypotony, glaucoma, keratopathy, and cataract. Removal of silicone oil and reoperations were also recorded. RESULTS: Overall, at 6 months 84% of patients had full retinal reattachment and 94% had stable posterior retinal reattachment. There was no significant difference in success in the primary outcome measure (56%, treatment group; 51%, placebo group; P = 0.59) or in secondary outcome measures or rates of complications. Secondary macular pucker occurred less often in the treatment group (6% vs. 17% at 6 months, P = 0.068). CONCLUSIONS: A perioperative infusion of combined 5-fluorouracil and LMWH does not significantly increase the success rate of vitreoretinal surgery for established PVR.

Basement membrane-dependent modification of phenotype and gene expression in human retinal pigment epithelial ARPE-19 cells.

PURPOSE: To use porcine lens capsule (PLC) as basement membrane for ARPE-19 cells and to characterize its effects on cell differentiation and gene expression. METHODS: Postconfluent cultures of ARPE-19 cells were established on either porous polyester filters or PLC membranes and characterized by electron microscopy, immunocytochemistry, and transepithelial electrical resistance measurements. Metabolic activity was assessed by measuring phagocytosis of rod outer segments. mRNA populations of ARPE-19 cells grown on polyester and PLC membranes were compared by suppressive subtractive hybridization. Differentially regulated messages were subsequently identified by DNA sequencing and their altered expression confirmed by Northern or virtual Northern blot analysis. RESULTS: Culture of ARPE-19 cells on PLC membrane induced the formation of apical microvilli and the ability to phagocytose rod outer segments. These culture conditions also led to enhanced junctional distribution of ZO-1 and occludin, the formation of polarized membrane domains, and a significant increase in transepithelial resistance. Gene expression was significantly altered by growth on PLC membranes and 29 differentially expressed transcripts were identified. CONCLUSIONS: Culture of ARPE-19 cells on PLC membranes resulted in a more differentiated phenotype and in expression of a specific set of transcripts encoding protein products that may affect epithelial differentiation, polarity and survival.

Prophylactic 360 degrees cryotherapy in fellow eyes of patients with spontaneous giant retinal tears.

PURPOSE: To assess the effect of prophylactic 360 degrees peripheral retinal cryotherapy in fellow eyes of patients with spontaneous giant retinal tears (GRTs) on the incidence of retinal detachment. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Forty-eight consecutive patients (31 male, 17 female) with spontaneous GRTs were included. The average age was 41 +/- 2 years. The average refraction of the fellow eye was -4.0 +/- 0.8 diopters (D). INTERVENTION: Patients underwent vitrectomy and silicone oil tamponade in the affected eye and 360 degrees peripheral cryotherapy in the unaffected fellow eye during the same anesthetic. MAIN OUTCOME MEASURE: Attachment of the retina in the fellow eye was determined clinically by indirect ophthalmoscopy. RESULTS: During a mean follow-up of 84 +/- 10 months after cryotherapy, one patient (2%) experienced a retinal tear without retinal detachment, and three patients (6%) experienced a retinal detachment in the fellow eye. These occurred 18 +/- 9 months after prophylactic treatment and were the result of a small retinal break in two cases and a GRT posterior to the treated area in one case. CONCLUSIONS: Prophylaxis of fellow eyes with 360 degrees cryotherapy appears to be associated with a lower incidence of retinal detachment than that reported in natural history studies. A prospective, randomized clinical trial of such prophylaxis is desirable but would require a sample size of at least 645 patients in each arm of the study, as well as long-term follow-up of at least 5 years to show an unequivocal difference in outcome.

Vitreoretinal management of posteriorly dislocated plate haptic silicone intraocular lenses.

PURPOSE: To report the vitreoretinal management of posteriorly dislocated plate haptic silicone intraocular lenses (PHSIOLs) and to present a surgical algorithm for this problem. METHODS: A retrospective analysis of 12 cases of immediate and delayed posterior dislocation of a PHSIOL after phacoemulsification was performed. RESULTS: The ages of the patients ranged from 26 years to 82 years (mean, 68 years); six of the patients were male. Delayed posterior dislocation of the PHSIOL occurred in 7 eyes (after Nd:YAG laser capsulotomy in 4 cases), while intraoperative dislocation occurred in 5 eyes. Defects of the anterior capsulorhexis rim or posterior capsule were present in nine eyes. The mean time from PHSIOL dislocation to definitive treatment was 4.8 months (range, 0.25-13 months). All patients underwent pars plana vitrectomy and implant exchange or repositioning. The dislocated PHSIOL was removed through the transpupillary route in 8 cases, while it was segmented and delivered through the pars plana in 3. Two patients underwent implant repositioning in the ciliary sulcus, although subsequent redislocation in one case required transpupillary removal and exchange. The mean follow-up period was 6.5 months (range, 2-18 months), with a final best corrected visual acuity of 6/12 or better in 10 eyes. CONCLUSIONS: Delayed and immediate dislocation of PHSIOL can occur in eyes with a defect in capsular integrity. The implant may be repositioned or exchanged following vitrectomy with either transpupillary or pars plana removal, resulting in generally excellent postoperative visual acuity and minimal complications.

Is prophylactic 360-degree laser retinopexy protective? Risk factors for retinal redetachment after removal of silicone oil.

OBJECTIVES: To identify risk factors for retinal redetachment after removal of silicone oil. To determine the effectiveness of prophylactic laser in preventing retinal redetachment after removal of silicone oil. DESIGN: A nonrandomized retrospective comparative interventional trial. PARTICIPANTS: Three hundred seventy-six patients undergoing vitrectomy with silicone oil tamponade for rhegmatogenous retinal detachment at one institution over a 4-year period. Two hundred eighty-seven patients with fully attached retinas subsequently underwent removal of silicone oil. One hundred thirty-eight cases had undergone prophylactic 360 degrees laser retinopexy before removal of silicone oil, either at the time of their final retinal reattachment procedure (n = 36) or as a separate supplementary procedure (n = 102). METHODS: A retrospective case note review was performed to identify clinical and demographic factors associated with increased or reduced odds of retinal redetachment after removal of silicone oil. Both univariate and multiple variable analysis were used to identify significant risk factors. MAIN OUTCOME MEASURES: Incidence of retinal redetachment after removal of silicone oil. RESULTS: Median follow-up after removal of silicone oil was 272 days. Three hundred sixty-degree prophylactic laser retinopexy was associated with a reduction from 26% to 14% in the incidence of redetachment after removal of silicone oil (adjusted odds ratio, 0.42; 95% confidence interval, 0.22-0.78; P = 0.006). Patients requiring further retinal reattachment surgery after their first oil procedure were at twice the odds of re-detachment after oil removal (adjusted odds ratio, 2.10; 95% confidence interval, 1.03-4.26; P = 0.04). CONCLUSIONS: The need for retinal reattachment surgery subsequent to a first silicone oil procedure was associated with twice the odds of retinal redetachment after removal of silicone oil. Prophylactic laser retinopexy may halve the incidence of retinal redetachment after removal of silicone oil.