A pilot study of a system for grading of drainage blebs after glaucoma surgery

Evaluation of sustained release of PLC-loaded prednisolone acetate microfilm on postoperative inflammation in an experimental model of glaucoma filtration surgery

PURPOSE

To evaluate the effect of a biodegradable microfilm with sustained release of prednisolone acetate (PA) on postoperative wound healing after experimental glaucoma filtration surgery (GFS).

METHODS

Biodegradable microfilms composed of poly (D-, L-lactide-co-caprolactone) (PLC) were fabricated and then pre-loaded PA-20% total weight. Fourteen New Zealand White rabbits were randomly divided into 3 treatment groups: GFS alone (n=4), GFS with PLC microfilms (n=4) and GFS with PA-loaded microfilm (n=6). Microfilms were inserted subconjunctivally, adjacent to the filtering surgical site. We monitored all eyes with slit-lamp examination, bleb photography and anterior segment optical coherence tomography (AS-OCT). Histology with immunohistochemistry was performed to determine the presence of any inflammation.

RESULTS

Prednisolone acetate 20%-loaded microfilms exhibited steady, sustained release in vitro. Eyes implanted with PA-loaded microfilms showed a significantly better bleb survival (100% vs. 37.5%, p<0.001) and reduced bleb vascularity (58%; 95% CI 54-62% vs. 30%; 95% CI 23-37%, p=0.001) compared to the control at 30 days postoperatively. Histology and immunohistochemistry demonstrated less T-cell infiltration in the eye implanted with PA-loaded microfilms.

CONCLUSION

Subconjunctival insertion of a PA-loaded biodegradeable microfilm exhibit sustained release of PA to reduce postoperative inflammation and prolong bleb survival in rabbit GFS.

Sustained release of an anti-glaucoma drug: demonstration of efficacy of a liposomal formulation in the rabbit eye

Topical medication remains the first line treatment of glaucoma; however, sustained ocular drug delivery via topical administration is difficult to achieve. Most drugs have poor penetration due to the multiple physiological barriers of the eye and are rapidly cleared if applied topically. Currently, daily topical administration for lowering the intra-ocular pressure (IOP), has many limitations, such as poor patient compliance and ocular allergy from repeated drug administration. Poor compliance leads to suboptimal control of IOP and disease progression with eventual blindness. The delivery of drugs in a sustained manner could provide the patient with a more attractive alternative by providing optimal therapeutic dosing, with minimal local toxicity and inconvenience. To investigate this, we incorporated latanoprost into LUVs (large unilamellar vesicles) derived from the liposome of DPPC (di-palmitoyl-phosphatidyl-choline) by the film hydration technique. Relatively high amounts of drug could be incorporated into this vesicle, and the drug resides predominantly in the bilayer. Vesicle stability monitored by size measurement and DSC (differential scanning calorimetry) analysis showed that formulations with a drug/lipid mole ratio of about 10% have good physical stability during storage and release. This formulation demonstrated sustained release of latanoprost in vitro, and then tested for efficacy in 23 rabbits. Subconjunctival injection and topical eye drop administration of the latanoprost/liposomal formulation were compared with conventional daily administration of latanoprost eye drops. The IOP lowering effect with a single subconjunctival injection was shown to be sustained for up to 50 days, and the extent of IOP lowering was comparable to daily eye drop administration. Toxicity and localized inflammation were not observed in any treatment groups. We believe that this is the first demonstration, in vivo, of sustained delivery to the anterior segment of the eye that is safe and efficacious for 50 days.

The role of different VEGF isoforms in scar formation after glaucoma filtration surgery

Vascular endothelial growth factor (VEGF) plays an important role in both physiological and pathological angiogenesis. Our previous studies showed a differential role of VEGF isoforms in retinal physiological angiogenesis. We also demonstrated that non-selective inhibition of VEGF by bevacizumab had a beneficial effect on surgical outcome after glaucoma filtration surgery by reducing angiogenesis as well as fibrosis. However, the function of the VEGF isoforms in pathological angiogenesis and wound healing in the eye still remains unidentified. This study was designed to elucidate the differential roles of VEGF isoforms in scar formation after trabeculectomy. Furthermore, we also investigated whether pegaptanib (Macugen™, Pfizer), an aptamer which specifically blocks VEGF(165), could improve surgical outcome by reducing postoperative scarring. VEGF-R2 and neuropilin-1 (NRP-1) expression was analyzed in vitro by RT-PCR, and were found to be expressed at higher levels in human umbilical vein endothelial cells (HUVEC) as compared to Tenon fibroblasts (TF). The effect of the different VEGF isoforms (VEGF(121), VEGF(165) and VEGF(189)) and pegaptanib on cell proliferation was determined via WST-1 assay. Endothelial cell proliferation was stimulated after addition of VEGF(121) and VEGF(165), whereas VEGF(121) and VEGF(189) increased fibroblast growth. These effects on proliferation were associated with an activation of the ERK pathway, as revealed using the TransAM c-Myc assay. Inhibition of the ERK pathway, by PD98059 administration, significantly reduced VEGF isoform induced cell growth. A dose-dependent reduction of endothelial cell proliferation was observed after pegaptanib administration, while only the highest dose was able to inhibit fibroblast growth. Next, the in vivo effect of pegaptanib was investigated in a rabbit model of trabeculectomy. The surgical outcome was evaluated by performing clinical investigations (IOP, bleb area, height and survival), as well as histomorphometric analyses of angiogenesis (CD31), inflammation (CD45) and fibrosis (Sirius Red). A single postoperative application of pegaptanib had a beneficial impact on surgical outcome, mainly by reducing angiogenesis, but not inflammation or collagen deposition. Repeated injections slightly improved surgical outcome, but again solely by reducing angiogenesis. In summary, our results revealed that the VEGF isoforms play a differential role in ocular wound healing: VEGF(165) and VEGF(121) predominantly affect blood vessel growth, whereas VEGF(189) is rather involved in fibrosis, an important process in wound healing.

Biocompatibility and biodegradation studies of subconjunctival implants in rabbit eyes

Sustained ocular drug delivery is difficult to achieve. Most drugs have poor penetration due to the multiple physiological barriers of the eye and are rapidly cleared if applied topically. Biodegradable subconjunctival implants with controlled drug release may circumvent these two problems. In our study, two microfilms (poly [d,l-lactide-co-glycolide] PLGA and poly[d,l-lactide-co-caprolactone] PLC were developed and evaluated for their degradation behavior in vitro and in vivo. We also evaluated the biocompatibility of both microfilms. Eighteen eyes (9 rabbits) were surgically implanted with one type of microfilm in each eye. Serial anterior-segment optical coherence tomography (AS-OCT) scans together with serial slit-lamp microscopy allowed us to measure thickness and cross-sectional area of the microfilms. In vitro studies revealed bulk degradation kinetics for both microfilms, while in vivo studies demonstrated surface erosion kinetics. Serial slit-lamp microscopy revealed no significant inflammation or vascularization in both types of implants (mean increase in vascularity grade PLGA50/50 12±0.5% vs. PLC70/30 15±0.6%; P = 0.91) over a period of 6 months. Histology, immunohistochemistry and immuno-fluorescence also revealed no significant inflammatory reaction from either of the microfilms, which confirmed that both microfilms are biocompatible. The duration of the drug delivery can be tailored by selecting the materials, which have different degradation kinetics, to suit the desired clinical therapeutic application.

Prospective study of surgical outcomes and bleb morphology using indocyanine green as a surgical dye in trabeculectomy with mitomycin C

BACKGROUND

To investigate the effect of adding indocyanine green to mitomycin C in augmented trabeculectomy.

DESIGN

A prospective, non-comparative interventional case series.

PARTICIPANTS

A total of 37 eyes of 37 patients followed up for 1 year.

METHODS

A solution containing 12.5 mg/mL of indocyanine green was added to mitomycin C, resulting in an mitomycin C concentration of 0.2-0.4 mg/mL, which was applied to bare sclera and Tenon's capsule for 3 min during trabeculectomy.

MAIN OUTCOME MEASURES

Visual acuity, intraocular pressure, bleb morphology, Moorfields Bleb Grading System scores and complications.

RESULTS

Indocyanine green could be visualized on clinical examination for all eyes on the first postoperative day. Mean intraocular pressure decreased from 22.9 ± 6.2 mmHg to 12.1 ± 4.4 mmHg postoperatively (P < 0.001) at 1 year. Thirty-four eyes (91.9%) achieved an intraocular pressure of less than 21 mmHg at final visit without additional topical intraocular pressure-lowering medications. Three eyes (8.1%) developed bleb failure and required Baerveldt device implantation. There were no cases of blebitis or late bleb leak. No adverse effects attributable to indocyanine green could be identified postoperatively.

CONCLUSION

The addition of indocyanine green during trabeculectomy improves the visibility of antimetabolites intraoperatively and allows for the estimation of antimetabolite treatment area intraoperatively and postoperatively. It appears to have no adverse effect on surgical outcomes and complication rates, while improving safety of antimetabolite use.

Stratus optical coherence tomography study of filtering blebs after primary trabeculectomy with a fornix-based conjunctival flap

PURPOSE

To investigate the relationship between filtering bleb function and Stratus optical coherence tomography (OCT) images.

METHODS

We studied 72 eyes of 65 consecutive patients who had a fornix-based conjunctival flap in primary trabeculectomy with mitomycin C (MMC). Filtering blebs with various types of glaucoma were examined using Stratus OCT. Success rates were defined as intraocular pressure (IOP) < or = 15 mmHg and IOP reduction > or = 25% without medication or additional surgery. Success rates among classified groups were compared using Kaplan-Meier survival curves and the log-rank test.

RESULTS

Blebs were classified into three different categories on the basis of the following Stratus OCT patterns: cystoid type (multiple cysts inside the bleb; 17 eyes), diffuse type (low to high reflective areas that were mixed inside the bleb; 31 eyes) and layer type (medium to high reflective layer inside the bleb; 24 eyes). Success rates in the cystoid-, diffuse- and layer-type blebs were 94%, 97% and 75% (P = 0.02), respectively.

CONCLUSION

In trabeculectomy with MMC and a fornix-based conjunctival flap, there is a significant association between the success rates and the postoperative Stratus OCT findings of filtering blebs.

High-definition imaging of trabeculectomy blebs using spectral domain optical coherence tomography adapted for the anterior segment

BACKGROUND

The aim of this work was to image trabeculectomy blebs using spectral domain optical coherence tomography (SDOCT).

METHODS

In this prospective cross-sectional study, patients who had undergone trabeculectomy with at least 3 months of follow up were included. Blebs were imaged using an adapted SDOCT system (Cirrus HD-OCT, Carl Zeiss Meditec Inc., Dublin, CA, USA) and time domain anterior segment optical coherence tomography (ASOCT) (Visante OCT, Carl Zeiss Meditec Inc.). An observer masked to clinical data assessed the utility of SDOCT and ASOCT in visualizing structures in successful and failed blebs.

RESULTS

Fifty-one eyes were imaged, of which 43 (84.3%) were successful. SDOCT showed wall thickening (93.0% vs. 67.4%, P = 0.006) and discrete hyporeflective spaces in the wall (88.4% vs. 14.0%, P < 0.0001) in a greater proportion of successful blebs than ASOCT. SDOCT showed the bleb cavity (23.3% vs. 48.8%, P = 0.02), scleral flap (34.9% vs. 90.7%, P < 0.0001), subflap space (20.9% vs. 72.1%, P < 0.0001) and ostium (9.3% vs. 88.4%, P < 0.0001) in fewer successful blebs than ASOCT. The internal ostium was not visualized in any failed bleb using SDOCT, whereas ASOCT showed the ostium in 87.5% of failed blebs (P = 0.001). SDOCT showed cystic spaces in the bleb wall in a greater proportion of successful blebs than failed blebs (88.4% vs. 37.5%, P = 0.005).

CONCLUSIONS

SDOCT imaging was able to show fine superficial features in the bleb wall. However, SDOCT had limited clinical utility in that it did not provide useful information about deep features such as flap position, bleb cavity formation or patency of the subflap space and internal ostium.

Information loss in 2 bleb grading systems

PURPOSE

To assess the effectiveness of transferring descriptive information from bleb photographs to 2 recently described bleb grading systems: the Moorfields Bleb Grading System (MBGS) and the Indiana Bleb Appearance Grading Scale (IBAGS).

METHODS

Two experienced observers graded 51 clinical bleb photographs with a wide range of appearances using both the MBGS and IBAGS bleb grading systems in random order. Grading scores from the 2 observers were averaged, and these numbers used by a third investigator, who did not view the original photographs, to generate 102 sketched representations of the blebs. The sketches were labeled randomly, and 1 month later presented individually in random order, to mask which grading system was used as source data for each drawing.

MAIN OUTCOME MEASURES

The original graders then used an arbitrary 1-5 scale to rate congruity between sketches and photographs for vascularity and morphology features, and overall agreement of the bleb sketches.

RESULTS

For both the IBAGS and MBGS, interobserver agreement between the Congruity Scores (CS) of the 2 masked graders was excellent, ranging between 92% and 98% for each parameter. Overall CS results were 3.2 (good-very good) for IBAGS and 4.1 (very good-excellent) for MBGS. Vascularity CS scores from IBAGS were 3.0 (good) and those from morphology agreement averaged 3.5 (good-very good). For the MBGS, the respective results were 3.9 (good-very good) and 4.1 (very good-excellent), respectively. Photographic quality (P=0.012) and presence of a limbus-based conjunctival flap scar (P=0.012) had an influence on CS scores from IBAGS but not from MBGS.

CONCLUSIONS

Both the IBAGS and MBGS produced acceptable agreement ratings between the sketches derived from grading system data and the original bleb photographs. These grading systems seem to adequately represent the blebs that are being encoded, without significant information loss from the simplification and translation process. The MBGS tended to have higher CS, and may be less influenced by photograph quality and bleb type, suggesting that bleb photographs may be best encoded for statistical analysis in clinical studies using this system.

[Utility of the Visante OCT in the follow-up of glaucoma surgery]

PURPOSE

To evaluate the utility of the Visante OCT in the follow-up of filtering surgery.

MATERIAL

and methods: In this study, we evaluated 38 filtering blebs in 31 patients following trabeculectomy (4) and nonpenetrating deep sclerectomy (NPDS). In 11 cases, mitomycin C was used during surgery. In patients who underwent NPDS, a collagen implant was placed within the scleral site in eight eyes and seven eyes had goniopuncture during follow-up. All patients had complete ophthalmologic examination with morphological evaluation of the bleb and intraocular pressure measurement as well as Visante OCT evaluation.

RESULTS

The trabeculectomy site as well as the trabeculodescemetic membrane (in NPDS), the scleral flap, the conjunctival flap, the iris, and the relationship between these structures were analyzed. Functioning blebs had a hyporeflective and irregular conjunctival tissue associated with a route for aqueous humor under the scleral flap from the anterior chamber toward the subconjunctival space. This filtration route was also observed within nonfunctioning encapsulated blebs. Flat and encapsulated nonfunctioning blebs had dense and hyperreflective conjunctival tissue. In the particular case of nonfunctioning flat blebs, there was no route for aqueous humor filtration under the scleral flap.

CONCLUSION

The Visante OCT is a simple and noninvasive imaging technique with good resolution, allowing the analysis of morphologic changes occurring in eyes after filtering surgery.

In Vivo Confocal Microscopy of Failing and Functioning Filtering Blebs

PURPOSE

To correlate clinical filtering bleb function with characteristics as detected by in vivo confocal microscopy.

METHODS

In a case-matched cross-sectional study, 52 eyes of 48 patients were examined 1 day to 12.8 years after primary trabeculectomy (mean 375 d). The patients were examined clinically and by in vivo confocal microscopy (Rostock Cornea Module/Heidelberg Retina Tomograph II, Heidelberg Engineering, Inc, Heidelberg, Germany). Nine early and 17 late functioning blebs were pair-matched with malfunctioning blebs. Stromal fiber patterns, the number of intraepithelial and stromal cystic spaces, and the amount of cellular infiltrates were evaluated.

RESULTS

Four stromal patterns (trabecular, reticular, corrugated, compacted) invisible to slit-lamp biomicroscopy could be distinguished by in vivo confocal microscopy. The trabecular pattern occurred only in functioning blebs, particularly early postoperatively. Intraepithelial cystic spaces were associated with functioning late blebs, whereas they were equally distributed in early blebs. In contrast, stromal cystic spaces indicate function in early blebs, whereas in late blebs the number of these cavities was similar in both groups. The density of intraepithelial and stromal round cells was higher in functioning late blebs compared with malfunctioning late blebs.

CONCLUSIONS

In vivo confocal microscopy allows to assess filtering bleb structures that are invisible biomicroscopically. Some morphologic features detected by this technique seem to indicate filtering bleb function and time after surgery. The predictive value of these features deserves further clarification in a prospective longitudinal study.

[Postoperative care after glaucoma filtration surgery]

Scarring of the filtering bleb is the main complication after glaucoma filtration surgery. Postoperative care most importantly determines success or failure of the operation. Both, preoperative antiinflammatory treatment and reduction or discontinuation of topical medication have a positive effect on postoperative conjunctival wound healing. After conventional postoperative care only about 40% of patients reach target pressures in the long-term without topical medication. Intensified postoperative care (IPC) increases the success rate by 25% after 5 years. Central to the concept of IPC is a wound modulating therapy which is adapted to the phases of wound healing of the filtering bleb. Evaluation of filtering bleb morphology is a prerequisite for the application of topical steroids and 5-fluorouracil. In addition, dedicated counseling of the patient and close follow-up are mandatory. In order to further increase the success rate of penetrating glaucoma surgery and decrease the side effects of the current antimetabolite therapy more research on wound healing as well as specific therapy to prevent scarring are necessary.

Imaging of trabeculectomy blebs using anterior segment optical coherence tomography

OBJECTIVE

To image trabeculectomy blebs using anterior segment optical coherence tomography (AS-OCT).

DESIGN

Prospective cross-sectional study.

PARTICIPANTS

Fifty-five patients who had previously undergone trabeculectomy surgery.

METHODS

All blebs were imaged with a prototype of the AS-OCT. Standardized color monophotographs of blebs were also obtained. Blebs were assessed for the following qualitative features: bleb height, thickness of the conjunctiva in the bleb wall, presence of cystic spaces within the bleb wall, apposition of the scleral flap to underlying sclera, and patency of the internal ostium.

MAIN OUTCOME MEASURES

For blebs with preoperative intraocular pressure (IOP) > 18 mmHg with or without ocular hypotensive medication, success was defined as last recorded IOP< or =18 mmHg without topical glaucoma medication. For blebs with preoperative IOP< or =18 mmHg with ocular hypotensive medication, success was defined last recorded IOP< or =18 mmHg with cessation of ocular hypotensive medication. For blebs with preoperative IOP< or =18 mmHg without ocular hypotensive medication, a 20% drop in IOP with no ocular hypotensive medication was accepted as success.

RESULTS

Seventy-eight blebs in eyes of 55 patients were imaged. There were 32 (58.2%) men and the mean age was 68.9+/-11.5 years. Fifty-seven (73.1%) blebs were classified as successful. Anterior segment optical coherence tomography identified the following bleb characteristics: total bleb height, bleb cavity, bleb wall thickness, tangential and radial dimensions, scleral flap thickness, and patency of the internal ostium. The majority of successful blebs displayed thickening of the bleb wall. Failed blebs were mostly low and were characterized by ostial occlusion, apposition of conjunctiva-episclera to sclera or apposition of the scleral flap to its bed. Thickening of the bleb wall was typically absent.

CONCLUSIONS

AS-OCT is a promising tool to image trabeculectomy blebs. It was able to demonstrate features of bleb morphology not visible with the slit lamp.

Analysis of bleb morphology after trabeculectomy with Visante anterior segment optical coherence tomography

BACKGROUND

To describe the use of anterior segment optical coherence tomography (OCT) in imaging intrableb morphology after trabeculectomy.

METHODS

14 post-trabeculectomy eyes from 11 primary open angle glaucoma and 3 primary angle closure glaucoma subjects were studied. The blebs were classified with reference to slit lamp morphology and bleb function. They included diffuse filtering (n = 7), cystic (n = 2), encapsulated (n = 2) and flattened (n = 3) bleb types. One eye in each patient was imaged with the Visante anterior segment OCT. A vertical scan line of 10 mm consisting of 512 A-scans was positioned at the centre of the bleb. The images were then analysed by built-in software. Intrableb morphologies and structures, including bleb wall thickness, subconjunctival fluid collections, suprascleral fluid space, scleral flap thickness, intrableb intensity (low, medium or high) and the route under the scleral flap were characterised and measured.

RESULTS

Diffuse filtering blebs were found by subconjunctival fluid collections. Suprascleral fluid space and the route under the scleral flap were identified in four of the seven cases. Cystic blebs were composed of a large hyporeflective space with multiloculated fluid collections covered by a thin layer of conjunctiva. Encapsulated blebs had a thick bleb wall with high reflectivity and an enclosed fluid filled space. Flattened blebs demonstrated high scleral reflectivity and no bleb elevation.

CONCLUSIONS

Visante anterior segment OCT can be used for bleb imaging. The different patterns of intrableb morphology identified by OCT were related to slit lamp appearance and bleb function. This information may be useful to study the different surgical outcomes and the process of wound healing in trabeculectomised eyes.

Comparison of Two Clinical Bleb Grading Systems

PURPOSE

To evaluate 2 recently described grading systems for clinical grading of filtering surgery blebs: the Moorfields Bleb Grading System (MBGS) and the Indiana Bleb Appearance Grading Scale (IBAGS).

DESIGN

Observational comparative study.

PARTICIPANTS

Twenty-four glaucoma filtering blebs in 24 eyes of 17 patients.

METHODS

Three observers in a prospective agreement study compared MBGS with IBAGS during slit-lamp examination.

MAIN OUTCOME MEASURES

Comparison analyses were performed, including agreement, repeatability, and intraclass correlation coefficient (ICC).

RESULTS

A wide range of bleb characteristics was represented in the cohort. Acceptable levels of intrasystem agreement were found in both systems: for IBAGS, overall agreement at the 0.5- and 1.0-unit levels were 80.6% and 97.6%, respectively, and for MBGS, these were 78.4% and 97.4% for morphologic and vascularity indices. Repeatability coefficients ranged from 0.5 to 1.4 for MBGS and 0.8 to 1.2 for IBAGS. The ICC values in the MBGS ranged from 0.18 to 0.72 for single measures and 0.39 to 0.88 for average measures. For IBAGS, the single-measure ICC values were between 0.06 and 0.53, and the average-measure ICC values were between 0.16 and 0.77. The MBGS ICC values for bleb size were higher than for IBAGS.

CONCLUSIONS

Both methods are reproducible clinically and had generally high levels of interobserver agreement. Both have minor deficiencies that should be amenable to improvement. The MBGS performed similarly to the IBAGS for reproducibility, had higher ICC values for morphologic features, and captured extra vascularity data with probable clinical implications.

Recent advances in trabeculectomy technique

PURPOSE OF REVIEW

Trabeculectomy is an effective operation for lowering intraocular pressure. However, success is limited by complications such as infection, hypotony, and scarring.

RECENT FINDINGS

These complications, which are increased by antifibrotic use, can be reduced with attention to surgical technique. We highlight the benefit of sub-Tenon anaesthesia, careful choice of the surgical site, fashioning of the scleral flap to produce diffuse aqueous flow, and better intraocular pressure control, maintenance of intraocular pressure, a formed anterior chamber, with outflow control during surgery using an infusion, optimal method of antimetabolites application, new adjustable sutures, and corneal-conjunctival closure techniques.

SUMMARY

These techniques reduce hypotony, producing a diffuse noncystic bleb with long-term pressure control.