Evaluation of leakage resistance improvement in transconjunctival sutureless vitrectomy sclerotomies closed with adhesives. an experimental study.

BACKGROUND: The purpose of this paper is to study the utility of adhesives (artificial-cyanoacrylate and biological-fibrin glue) for improving transconjunctival sutureless vitrectomy (TSV) sclerotomy closure competency. METHODS: Experimental and observer-masked study in which after performing TSV in cadaveric pig eyes, different adhesives were tested on sclerotomy entrances in order to determine if they improved closure competency in face of progressive intraocular pressure increase. In 76 eyes cyanoacrylate-treated sclerotomies were compared with sclerotomies in which no additional manoeuvre to aid closing was performed; in 76 eyes fibrin glue with no manoeuvre; and in the last 76 eyes, cyanoacrylate-treated sclerotomies were compared with fibrin glue-treated sclerotomies. RESULTS: A total of 228 eyes had a 23-gauge TSV performed. Both cyanoacrylate and fibrin glue treated sclerotomies achieved higher mean opening pressures when compared with nontreated sclerotomies in the same eye (p < 0.002). When cyanoacrylate was compared with biological adhesive in the same eye, no statistically significant differences were obtained (p = 0.216). DISCUSSIONS: This experimental study provides support for the possible role of adhesives in improving TSV sclerotomy closure competency in clinical practice.

Evaluation of mechanical closure resistance of sutureless vitrectomy sclerotomies after conjunctival cauterization with bipolar diathermy forceps.

BACKGROUND: Suturing is the most widely used technique to close leaking sclerotomies after transconjunctival sutureless vitrectomy (TSV). However, with the aim of avoiding the disadvantages caused by conjunctival stitches, there have been described other closure techniques, such as the cauterization of the conjunctiva placed over the incisions. To continue advancing knowledge of the incisional occlusion effect achieved by conjunctival diathermy, it would be also interesting to study the wound closure resistance obtained under intraocular pressure (IOP) changes, given that in the early postoperative period eyes are subjected to pressure stress. In our study, we compare the mechanical resistance observed in sclerotomies treated with bipolar diathermy after TSV compared to that found in incisions in which cauterization was not performed. METHODS: This was an experimental, randomized, and observer-masked study in which 23-gauge TSV was performed in 80 cadaveric pig eyes. Once each vitrectomy was finished, cauterization was performed with bipolar diathermy forceps on the conjunctiva placed over one of the superior sclerotomy sites; no maneuver was performed over the other superior incision. IOP was gradually increased by means of the vitrectomy system (Accurus; Alcon Laboratories, TX) until one of the superior sclerotomies opened, allowing internal ocular solution to escape. RESULTS: In 35 % of cases (28 of 80 eyes), sclerotomies subjected to diathermy allowed intraocular fluid escape first (p = 0.01). When comparing opening pressure values, cauterized incisions leaked at significantly higher pressure levels than those in which diathermy was not applied (p < 0.001). CONCLUSIONS: Bipolar diathermy on sutureless sclerotomies has demonstrated to be, in our experimental model, an effective method for increasing the sclerotomy closure resistance. Although its use in vitrectomized eyes has previously been described, our study is the first to analyze the response of cauterized sclerotomies to IOP increases.

Assessment of Closure Competency of Sutureless Vitrectomy Sclerotomies After Scleral Hydration.

PURPOSE: To assess the influence that hydration applied on the sclerotomy edges may have on incisional closure resistance after transconjunctival sutureless vitrectomy (TSV). METHODS: Experimental, randomized and observer-masked study in which 23-gauge TSV was performed in 80 cadaveric pig eyes. Once each vitrectomy was finished, hydration with balanced salt solution (BSS) was applied on the sclerotomy edges of one of the superior incision sites; no maneuver was performed on the other superior sclerotomy. Intraocular pressure (IOP) was gradually increased by means of the vitrectomy system (Accurus; Alcon Laboratories, TX) until one of the superior sclerotomies opened, allowing internal ocular solution to escape. RESULTS: In 45% of cases (36 of 80 eyes), sclerotomies subjected to hydration allowed intraocular fluid escape (p = 0.43). There were no differences when comparing opening pressure values of hydrated and non-hydrated sclerotomies (p = 0.19). CONCLUSIONS: Scleral hydration did not demonstrate increase in the sclerotomy closure resistance in our experimental model. Given the widespread use of sutureless TSV around the world, the results obtained in our research, in spite of being negative, may contribute to the knowledge of the behavior of sutureless sclerotomies.

Association between macular perfusion and photoreceptor layer status in diabetic macular edema.

PURPOSE: To evaluate the relationship between the photoreceptor layer status (inner segment ellipsoid band and external limiting membrane) and the foveal avascular zone size, as a result of macular perfusion, in patients with diabetic macular edema. METHODS: This observational case series study included 151 eyes of 118 patients with naive diabetic macular edema. The length of the disrupted photoreceptor layer was assessed by optical coherence tomography. The foveal avascular zone diameter was measured on fluorescein angiogram. RESULTS: No significant association was found between the foveal avascular zone size and the mean lengths of the disrupted inner segment ellipsoid band nor the external limiting membrane in patients with naive diabetic macular edema. CONCLUSION: Macular ischemia, which lengthens the distance from the perifoveal vessels to the center of the fovea and may disrupt the normal flow of nutrients by simple diffusion to the photoreceptor line, does not seem to influence on inner segment ellipsoid band nor external limiting membrane integrity. Future studies may evaluate the effect of choroidal vascularization on the photoreceptor layer status to enhance the knowledge about the photoreceptor layer nutrients source.

Influence of the source of incisional vitreous incarceration on sclerotomy closure competency after transconjunctival sutureless vitrectomy.

PURPOSE: To evaluate the influence that the origin of incisional vitreous incarceration may have on the presence of postoperative conjunctival blebs over sclerotomies after transconjunctival sutureless vitrectomy (TSV). Blebs are formed by incisional leakage due to incompetent closure. METHODS: Twenty-three-gauge TSV was performed in 83 cadaveric pig eyes. Once each vitrectomy was finished, ultrasound biomicroscopy (UBM) was used to assess the presence of postoperative conjunctival blebs over the sclerotomy sites, as well as the existence of vitreous incarcerated in incisions. Vitreous strands may come from the perisclerotomy area, running parallel to the sclera toward the inner hole of the sclerotomies, or may radiate from the core of the vitreous cavity. RESULTS: Vitreous entrapment was found in 73.9% of the sclerotomies; 43.4% of the incisions showed vitreous strands coming parallel to the sclera (12.9% of them showed conjunctival bleb), 19.7% of the wounds presented vitreous aiming toward the core of the vitreous cavity (2% of them had conjunctival bleb) and 10.8% of the entrances presented both vitreous incarceration sources (none of them showed bleb). Incisions with vitreous entrapment parallel to the sclera were associated with a significantly greater sclerotomy leakage rate. CONCLUSIONS: Sclerotomies with vitreous incarceration coming from the core of the vitreous cavity showed a greater incisional closure competency than that observed in incisions with vitreous entrapment coming from the pericannular area; if these results were confirmed in humans, different postoperative suture rates may be expected on sclerotomies according to the vitrectomy degree performed in different areas of the vitreous cavity.

Evaluation of conjunctival bleb detection after vitrectomy by ultrasound biomicroscopy, optical coherence tomography and direct visualization.

PURPOSE: To compare ultrasound biomicroscopy (UBM), anterior-segment optical coherence tomography (AS-OCT), and direct visualization for detecting conjunctival blebs in sutureless sclerotomies after vitrectomy. Conjunctival blebs are formed by sclerotomy leakage due to incompetent closure. METHODS: Experimental, randomized, and observer-masked study in which 23-gauge vitrectomies were performed in cadaveric pig eyes. Postoperative conjunctival blebs were assessed by UBM, AS-OCT, and direct visualization. No conjunctival blebs were classified as Grade 0 (G0), thin blebs (less than or equal to one-half of scleral thickness) as Grade 1 (G1) and thick blebs (greater than one-half of scleral thickness) as Grade 2 (G2). RESULTS: Fifty pig eyes were included. Conjunctival blebs were found in 13.3% (8% G1, 5.3% G2) of the incisions analyzed by UBM, in 20% (14.7% G1, 5.3% G2) of the sclerotomies studied by AS-OCT, and in 7.3% (2% G1, 5.3% G2) of the wounds evaluated by direct visualization. AS-OCT was the most sensitive method for identifying conjunctival blebs when compared with UBM and direct visualization (p<0.001). In turn, UBM was better than direct visualization for observing sclerotomy blebs (p=0.004). CONCLUSIONS: AS-OCT is the most sensitive technique for detecting subclinical blebs (G1) and thus, it may be useful in research for studying the influence that surgical factors and maneuvers may exert on sclerotomy closure capacity after vitrectomy. Direct visualization, that is used in routine clinical practice to determine which sclerotomies should be sutured, is useful only to identify thick blebs (G2) after vitrectomy.

Influence of sclerotomy use on vitreous incarceration in an experimental model of vitrectomized eye.

PURPOSE: To evaluate the influence of sclerotomy use during vitrectomy (vitreous cutter, illumination probe, or infusion-line entrance) on postoperative vitreous incarceration using an experimental model of vitrectomized eye. MATERIALS AND METHODS: Experimental, randomized, and observer-masked study in which 23-gauge transconjunctival sutureless vitrectomy was performed in cadaveric pig eyes. Postoperative incisional vitreous entrapment was evaluated by direct visualization. No vitreous incarceration was classified as grade 0 (G0), thin vitreous entrapment was classified as grade 1 (G1), and thick vitreous strands as grade 2 (G2). RESULTS: A total of 46 eyes were included. Vitreous incarceration was detected in 91.3% (43.5% G1, 47.8% G2) of the sclerotomies used by the vitreous cutter probe, 95.7% (45.7% G1, 50% G2) of the illumination-pipe entrances, and 93.5% (45.7% G1, 47.8% G2) of the infusion-line incisions. No statistical differences were found when comparing incisional vitreous incarceration after vitrectomy according to sclerotomy use. CONCLUSION: Different manipulation of the sclerotomies, depending on their use, does not seem to influence postvitrectomy vitreous entrapment in our experimental model.

Influence of incisional vitreous incarceration in sclerotomy closure competency after transconjunctival sutureless vitrectomy.

PURPOSE: To evaluate the influence that vitreous incarceration may exert on the presence of postoperative conjunctival blebs over sclerotomies after transconjunctival sutureless vitrectomy (TSV). Blebs are formed by incisional leakage due to incompetent closure. METHODS: Experimental study in which 23-gauge TSV was performed in 146 cadaveric pig eyes. Once the vitrectomy was finished, triamcinolone was injected inside the vitreous cavity for staining residual vitreous, one of the superior cannulas was extracted over the light probe, and the other cannula was removed with the plug inserted. Postoperative conjunctival blebs in superior sclerotomies were assessed by anterior-segment optical coherence tomography (AS-OCT) in a masked fashion; nondetectable blebs were classified as grade 0 (B0), thin bleb (≤half scleral thickness) as grade 1 (B1), and thick bleb (>half scleral thickness) as grade 2 (B2). Postoperative incisional vitreous entrapment was evaluated by slit-lamp photographs in a masked way; no incarceration was classified as grade 0 (V0), thin incarceration as grade 1 (V1), and thick incarceration as grade 2 (V2). RESULTS: Conjunctival blebs were found in 13.7% of the sclerotomies (11.3% bleb-B1, 2.4% bleb-B2). Vitreous incarceration was found in 96.5% of the sclerotomies without bleb (B0), 81.8% of the incisions with bleb-B1, and 14.3% of the wounds with bleb-B2. Vitreous incarceration was significantly associated with the absence of conjunctival bleb (P < 0.001). CONCLUSIONS: Vitreous incarceration in sclerotomies is related to less incisional leakage in our experimental model. Maneuvers that reduce vitreous entrapment, such as the interposition of a nonhollow probe during the cannula extraction, could decrease the sclerotomy closure competency.

Influence of the interposition of a nonhollow probe during cannula extraction on sclerotomy vitreous incarceration in sutureless vitrectomy.

PURPOSE: To evaluate the effect of the cannula removal technique on postoperative vitreous incarceration using an experimental model of vitrectomized eye. METHODS: In a prospective, experimental, randomized, and observer-masked study, 118 cadaveric pig eyes were vitrectomized through 23-gauge transconjunctival sclerotomies. Once vitrectomy was finished, one of the superior cannulas was extracted with the illumination probe inserted through it, and the other cannula was removed with a cannula plug inserted. Postoperative incisional vitreous entrapment was evaluated by direct visualization. No vitreous incarceration was classified as grade 0 (G0), thin vitreous entrapment was classified as grade 1 (G1), and thick vitreous strands as grade 2 (G2). RESULTS: Considering the sclerotomies whose cannulas were extracted with the light probe inside, vitreous incarceration was detected in 93.2% (73.7% G1, 19.5% G2) of the incisions. In turn, vitreous entrapment was observed in 95.8% (43.2% G1, 52.6% G2) of the entry sites whose cannulas were extracted with the plug inserted. Statistical analysis showed significant differences when comparing postvitrectomy vitreous incarceration grades in sclerotomies according to the cannula extraction technique (P < 0.0001). CONCLUSIONS: Interposing the light probe through the cannula during its removal reduces vitreous incarceration grade in our experimental model. This simple maneuver may decrease complications related to vitreous entrapment, such as peripheral retinal tears and acute endophthalmitis.

Assessment of vitreous incarceration in sclerotomies with OCT, ultrasound biomicroscopy, and direct visualization.

BACKGROUND AND OBJECTIVE: To compare anterior-segment optical coherence tomography (AS-OCT), ultrasound biomicroscopy (UBM), and direct visualization for detecting vitreous incarceration in sutureless sclerotomies. MATERIALS AND METHODS: Prospective, randomized, and observer-masked experimental study in which 23-gauge vitrectomy was performed in pig eyes. Postoperative incisional vitreous incarceration was evaluated by AS-OCT, UBM, and direct visualization. RESULTS: One hundred eighteen pig eyes were included. Vitreous entrapment was found in 7.9% (28 of 354), 59.6% (211 of 354), and 95.5% (338 of 354) of the sclerotomies analyzed by AS-OCT, UBM, and direct visualization, respectively. Direct visualization was the most sensible method for identifying incisional vitreous when compared with UBM and AS-OCT (P < .0001). In turn, UBM was superior to AS-OCT for observing vitreous incarceration (P < .0001). CONCLUSION: Direct visualization is the most effective method for detecting vitreous entrapment. Regarding the imaging techniques, UBM was superior to AS-OCT for identifying vitreous incarceration.

Effect of interposition maneuver during cannula removal on vitreous incarceration rate in vitrectomized eyes measured by ultrasound biomicroscopy.

PURPOSE: To evaluate the influence of the cannula removal maneuver on the postoperative incisional vitreous incarceration using an experimental model of vitrectomized eye. METHODS: Prospective, experimental, randomized and observer-masked experimental study in which 23-gauge transconjunctival sutureless vitrectomy was performed through oblique sclerotomies in cadaveric pig eyes. Once the vitrectomy was finished, one of the superior cannulas was removed with the light probe introduced through it, and the other cannula was extracted with the cannula plug inserted. Postoperative incisional vitreous incarceration was evaluated by ultrasound biomicroscopy (UBM). RESULTS: 60 eyes included. Considering the 60 superior sclerotomies whose cannulas were extracted with the light pipe inserted, vitreous incarceration was observed in 35% of them. On the other hand, 71.6% of the incisions whose cannulas were removed with the cannula plug inserted showed vitreous incarceration (p = 0.00013). CONCLUSIONS: Interposing the light probe through the cannula when it is removed seems to reduce the postoperative wound vitreous incarceration rate in our experimental model.

Influence of the sclerotomy use on mechanical incision competency in experimental model of vitrectomized eyes.

PURPOSE: To evaluate the influence of superior sclerotomy use (vitreous cutter or illumination probe entrance) on the postoperative sclerotomy closure competency using an experimental model of vitrectomized eye. METHODS: Prospective, experimental, randomized and observer-masked experimental study in which 23 and 25-gauge transconjunctival sutureless vitrectomy was performed through oblique sclerotomies in the same cadaveric pig eye. Closure competency was determined by the resistance to intraocular fluid leak through the superior incisions in face of a progressive intraocular pressure (IOP) rise. RESULTS: 120 eyes included. In 52.5% of cases, the vitreous cutter probe sclerotomy showed intraocular fluid leakage first (p = 0.65). When comparing opening pressure values, there were no significant differences (p = 0.77) between the leakage pressure level of both sclerotomies depending on their use. CONCLUSIONS: Different uses of superior sutureless oblique sclerotomies do not seem to influence on TSV incision mechanical resistance to IOP rise in our experimental model.

Experimental model to evaluate mechanical closure resistance of sutureless vitrectomy sclerotomies using pig eyes.

PURPOSE: The purpose of this study was to report a novel model for comparing mechanical resistance to intraocular pressure (IOP) increases with 23-gauge (23G) and 25G transconjunctival sutureless vitrectomy (TSV) sclerotomies in the immediate postoperative period using an experimental model of a vitrectomized eye. METHODS: This was a prospective, experimental, randomized, and observer-masked experimental study in which TSV 23G and 25G oblique sclerotomies, performed in same cadaveric pig eye, were subject to an increase in IOP. Mechanical resistance was determined by the resistance to intraocular fluid leak through the sclerotomy. The simultaneous use of the different sclerotomy diameters in the same eye avoided interindividual scleral resistance differences. RESULTS: This animal model allowed comparison of the effect of different sclerotomy diameters (23G and 25G) on incisional mechanical resistance. One hundred twenty eyes were included. In 60.7% of cases, the 23G sclerotomy first allowed intraocular fluid escape (leaked; P = 0.02). When comparing opening pressure values, 23G sclerotomies leaked at significantly lower pressure levels than 25G sclerotomies (P < 0.0001); 53% of the 25G incisions but only 16% of 23G incisions opened at pressure levels greater than 120 mm Hg. CONCLUSIONS: Oblique 23G sutureless sclerotomies offer less mechanical resistance to increases in IOP than do 25G sclerotomies. This animal model may become the basis for future studies to evaluate the advantages of using other types of incision or other surgical tools on sclerotomy closure capacity.

Effect of intravitreal ranibizumab on corneal endothelium in age-related macular degeneration.

PURPOSE: To determine the effect of intravitreal injection of ranibizumab on the corneal endothelium in patients with choroidal neovascularization in age-related macular degeneration. METHODS: Observational prospective case series study. Fifty-two eyes of 52 consecutive patients (29 men, 23 women; age range, 61-80 years) were evaluated. All participants received monthly intravitreal injections of (0.05 mL, 0.5 mg) ranibizumab for 3 consecutive months; the follow-up period was 6 months. Central corneal specular microscopy was performed before injection and at 7 days and 6 months after the first intravitreal injection. The endothelial cell density, coefficient of variation of cell size, and percentage of hexagonal cells were analyzed, and the central corneal thickness was measured. RESULTS: There were no significant differences in the endothelial cell densities, coefficient of variation of cell sizes, and percentage of hexagonal cells values before injection and at 7 days and 6 months after the first intravitreal ranibizumab injection (P = 0.987, P = 0.822, and P = 0.918, respectively). There was also no significant difference in central corneal thickness measurements before injection and at 7 days and 6 months after the first intravitreal ranibizumab injection (P = 0.325). CONCLUSION: Repeated intravitreal injections of 0.5 mg of ranibizumab do not seem to cause substantial changes in the corneal endothelium at 6 months.

Simple maneuver for unfolding giant retinal tear inverted flap trapped under perfluorocarbon bubble.

Inverted retinal detachments secondary to giant retinal tears are sometimes difficult to unfold with the perfluorocarbon (PFC) bubble even after complete epiretinal dissection due to the tendency of the flap to maintain its inverted configuration. The following maneuver has been performed in two cases. After reducing the PFC bubble volume to the level of the border of the flap, the tip of the same perfluorocarbon injection cannula is used to capture the inverted retinal flap with gentle suction. The flap is lifted and brought centripetally to "cover" the PFC bubble and then released by stopping suction. Then bubble volume can be increased to reapply the entire retina, allowing for continuation of surgery. This simple maneuver allows, in one quick surgical step and without the introduction of new instruments, unfolding of persistently inverted giant retinal tears.

Intraoperative mitomycin C and corneal endothelium after pterygium surgery.

PURPOSE: To determine the effect of mitomycin C (MMC) on the corneal endothelium after primary pterygium surgery. METHODS: This prospective, interventional, nonrandomized, observer-masked study included 46 consecutive patients (51 eyes) with primary pterygium. The bare sclera technique with 1-minute application of 0.02% MMC intraoperatively was used in all cases. The follow-up period was 3 months. Preoperative and postoperative central corneal specular microscopy was performed. The endothelial cell density, coefficient of variation of cell size, and percentage of hexagonal cells were analyzed, and the corneal thickness was measured. RESULTS: The mean endothelial cell densities preoperatively and 3 months postoperatively were 2382.35 +/- 342.07 cells per square millimeter (range, 1020-3129) and 2385.02 +/- 356.83 cells per square millimeter (range, 1001-3151), respectively (P = 0.96). The mean coefficients of variation of cell size preoperatively and 3 months postoperatively were 34.31 +/- 5.62 (range, 22-49) and 35.29 +/- 7.50 (range, 22-55), respectively (P = 0.17). The mean percentages of hexagonal cells values preoperatively and 3 months postoperatively were 52.98 +/- 7.32 (range, 32-71) and 51.61 +/- 8.98 (range, 32-67), respectively (P = 0.48). The mean pachymetry measurements preoperatively and 3 months postoperatively were 506.65 +/- 36.87 microm (range, 411-583) and 502.08 +/- 41.33 microm (range, 411-593), respectively (P = 0.99). CONCLUSIONS: One intraoperative application of 0.02% MMC for 1 minute after primary pterygium surgery does not seem to cause substantial changes in the corneal endothelium at 3 months.