Doyne Lecture. The pathology of the outflow system in primary and secondary glaucoma

Evaluation of Schlemm's canal with swept-source optical coherence tomography in primary angle-closure disease

PURPOSE

To perform an in vivo evaluation of the changes in Schlemm's canal (SC) among patients with primary angle-closure disease (PACD) using swept-source optical coherence tomography (SS-OCT).

METHODS

Patients diagnosed with PACD who had not undergone surgery were recruited. The SS-OCT quadrants scanned herein included the nasal and temporal sections at 3 and 9 o'clock, respectively. The diameter and cross-sectional area of the SC were measured. A linear mixed-effects model was performed to analyze the effects of parameters on the SC changes. The hypothesis of interest was related to the angle status (iridotrabecular contact, ITC/open angle, OPN), which was further explored with pairwise comparisons of the estimated marginal means (EMMs) of the SC diameter and SC area. In the ITC regions, the relationship between the trabecular-iris contact length (TICL) percentage and SC parameters was also studied by a mixed model.

RESULTS

A total of 49 eyes of 35 patients were included for measurements and analysis. The percentage of observable SCs in the ITC regions was only 58.5% (24/41), whereas it was 86.0% (49/57) in the OPN regions (χ² = 9.44, p = 0.002). ITC was significantly associated with a decreasing SC size. The EMMs for the diameter and cross-sectional area of SC at the ITC and OPN regions were 203.34 μm versus 261.41 μm (p = 0.006) and 3174.43 μm² versus 5347.63 μm² (p = 0.022), respectively. Sex, age, spherical equivalent refraction, intraocular pressure, axial length, extent of angle closure, history of acute attack and treatment with LPI were not significantly associated with SC parameters. In the ITC regions, a larger TICL percentage was significantly associated with a decrease in SC diameter and area (p = 0.003 and 0.019, respectively).

CONCLUSIONS

The morphologies of SC could be affected by the angle status (ITC/OPN) in patients with PACD, and ITC was significantly associated with a decreasing SC size. These changes in SC as described by OCT scans might help to elucidate the progression mechanisms of PACD.

Bionic eye system mimicking microfluidic structure and intraocular pressure for glaucoma surgery training

Among increasing eye diseases, glaucoma may hurt the optic nerves and lead to vision loss, the treatment of which is to reduce intraocular pressure (IOP). In this research, we introduce a new concept of the surgery simulator for Minimally Invasive Glaucoma Surgery (MIGS). The concept is comprised of an anterior eye model and a fluidic circulatory system. The model made of flexible material includes a channel like the Schlemm’s canal (SC) and a membrane like the trabecular meshwork (TM) covering the SC. The system can monitor IOP in the model by a pressure sensor. In one of the MIGS procedures, the TM is cleaved to reduce the IOP. Using the simulator, ophthalmologists can practice the procedure and measure the IOP. First, considering the characteristics of human eyes, we defined requirements and target performances for the simulator. Next, we designed and manufactured the prototype. Using the prototype, we measured the IOP change before and after cleaving the TM. Finally, we demonstrated the availability by comparing experimental results and target performances. This simulator is also expected to be used for evaluations and developments of new MIGS instruments and ophthalmic surgery robots in addition to the surgical training of ophthalmologists.

Association of peripheral anterior synechiae with anterior segment parameters in eyes with primary angle closure glaucoma

To investigate the association of peripheral anterior synechiae (PAS) with intraocular pressure (IOP) and anterior-segment parameters in subjects with primary angle-closure glaucoma (PACG). A total of 267 subjects with PACG were recruited and underwent gonioscopy and anterior-segment optical coherence tomography (ASOCT). Customized software was used to measure ASOCT parameters, including angle opening distance (AOD750) and trabecular-iris-space-area (TISA750) at 750 µm from the scleral spur, anterior chamber depth, width, area and volume (ACD, ACW, ACA, ACV), iris thickness (IT750), iris area (IAREA), and lens vault (LV). Presenting IOP was defined as the first IOP reading before the initiation of IOP-lowering treatment. The mean age of the 267 subjects was 67.0 ± 8.9 years, 140 (52.4%) were male, and 246 (92.1%) were of Chinese ethnicity. PAS was present in 122 (45.7%) subjects, and was most frequently found in the superior quadrant (79.5%). Subjects with PAS had greater presenting IOP (28.7 ± 12.9 vs 22.4 ± 9.7 mmHg, p < 0.001), narrower AOD750 (p < 0.001), smaller TISA750 (p < 0.001), ACD (p = 0.04), ACA (p = 0.02), ACV (p = 0.01) and larger LV (p = 0.01) compared to PACG eyes without PAS. No significant differences were noted for iris parameters. A multivariate logistic regression analysis showed that higher presenting IOP (β = 0.20, p < 0.001), worse visual field mean deviation (β = - 0.20, p = 0.01) and narrower AOD750 (β = - 0.25, p = 0.03) were the only parameters that significantly correlated with the extent of PAS in clock hours. Almost one-half of the subjects with PACG demonstrated PAS; these eyes were associated with higher presenting IOP, smaller anterior segment dimensions and more severe disease.

Ab interno trabeculotomy combined with cataract extraction in eyes with primary open-angle glaucoma

OBJECTIVE

To investigate the efficacy and safety of ab interno trabeculotomy using the VISCO360® Viscosurgical System (Sight Sciences, Inc., Menlo Park, CA, USA) combined with cataract extraction in the treatment of primary open-angle glaucoma (POAG).

METHODS

Patients with POAG who underwent ab interno trabeculotomy combined with cataract extraction were retrospectively analyzed. Best-corrected visual acuity (BCVA), intraocular pressure (IOP), the number of antiglaucomatous medications, and complications were recorded preoperatively and 1 week, 1 month, 3 months, 6 months, 1 year, and 2 years postoperatively.

RESULTS

Thirty-four patients (40 eyes) with POAG were included in this study, including 20 men (22 eyes) and 14 women (18 eyes). Compared with the preoperative IOP, the postoperative IOP was significantly lower at each time point. The greatest reduction in IOP was 60.7% at 1 month after surgery. The BCVA was also significantly improved at each postoperative time point. The number of antiglaucomatous medications used by the patients was significantly lower postoperatively than preoperatively.

CONCLUSION

Ab interno trabeculotomy combined with cataract extraction is effective and safe for treatment of POAG.

Development of a Spherical Model with a 3D Microchannel: An Application to Glaucoma Surgery

Three-dimensional (3D) microfluidic channels, which simulate human tissues such as blood vessels, are useful in surgical simulator models for evaluating surgical devices and training novice surgeons. However, animal models and current artificial models do not sufficiently mimic the anatomical and mechanical properties of human tissues. Therefore, we established a novel fabrication method to fabricate an eye model for use as a surgical simulator. For the glaucoma surgery task, the eye model consists of a sclera with a clear cornea; a 3D microchannel with a width of 200–500 µm, representing the Schlemm’s canal (SC); and a thin membrane with a thickness of 40–132 µm, representing the trabecular meshwork (TM). The sclera model with a clear cornea and SC was fabricated by 3D molding. Blow molding was used to fabricate the TM to cover the inner surface of the sclera part. Soft materials with controllable mechanical behaviors were used to fabricate the sclera and TM parts to mimic the mechanical properties of human tissues. Additionally, to simulate the surgery with constraints similar to those in a real operation, the eye model was installed on a skull platform. Therefore, in this paper, we propose an integration method for fabricating an eye model that has a 3D microchannel representing the SC and a membrane representing the TM, to develop a glaucoma model for training novice surgeons.

Assessment of Schlemm's canal in acute primary angle closure: an anterior segment optical coherence tomography study

PURPOSE

To image and quantitatively evaluate the Schlemm's canal (SC) dimensions in the eyes with acute primary angle closure (APAC) with anterior segment optical coherence tomography (AS-OCT), and compare it with the SC measurements taken after the control of intraocular pressure (IOP) and in the normal age-matched controls.

MATERIALS AND METHODS

Seventeen eyes of 14 patients with the newly diagnosed APAC and 59 age-matched normal subjects underwent AS-OCT to image SC. SC cross-sectional area, SC meridional and coronal diameters were measured in the temporal and nasal regions at 3 and 9 o'clock position. After laser iridotomy and control of the IOP, all SC parameters were measured again at a week later, in APAC eyes. Intrasession intraobserver reliability of the SC measurements was assessed with intraclass correlation coefficient.

RESULTS

Mean SC-SCA (10,600 ± 2691 µm²), SC meridional (682 ± 125 µm) and coronal diameters (21.2 ± 8.2 µm) showed a significant increase in the APAC eyes at presentation, when compared to the SC parameters measured at a week later (6499 ± 1754 µm², 450 ± 169 µm and 15.75 ± 8.6 µm, p = < 0.0001, < 0.0001 and 0.01, respectively) and in the normal controls (7192 ± 1022 µm², 499.2 ± 179.8 µm, 15.43 ± 4.35 µm, p = 0.02, < 0.0001, 0.01, respectively). There was no difference in the measured SC parameters between the normal controls and APAC eyes, when the parameters were measured at a week, after resolution of the acute attack (all p > 0.05).

CONCLUSION

A significant expansion of SC was observed in the APAC eyes at presentation, when compared to the normal controls and after the acute attack resolved. SC parameters may provide a useful research tool for evaluating morphological changes in the SC in APAC eyes, during an acute attack.

Feasibility of laser trabeculoplasty in angle closure glaucoma: a review of favourable histopathological findings in narrow angles

Selective laser trabeculoplasty (SLT) has been indicated as a safe and efficient treatment for primary open-angle glaucoma; however, recent studies have also shown positive results with the use of SLT in some clinical conditions related to primary angle-closure glaucoma (PACG). Despite the potential benefits of SLT in selected cases of PACG, the mechanisms underlying the modifications in the trabecular meshwork tissue of patients with PACG are poorly understood. This narrative review approached both the current, limited knowledge about the histological changes observed in different forms of PACG and the clinical results of SLT treatment for PACG. Favourable outcomes of SLT in patients with PACG, specifically in areas of non-occluded angle, need further substantiation through large controlled clinical trials. A deeper understanding of the biomolecular changes of those areas is essential to improve both laser technical details and the clinical efficacy of SLT therapy.

Selective laser trabeculoplasty for glaucoma secondary to emulsified silicone oil after pars plana vitrectomy: a pilot study

Background. To investigate the efficacy of selective laser trabeculoplasty (SLT) for lowering intraocular pressure (IOP) in patients with open angle glaucoma (OAG) secondary to emulsified silicone oil (SO). Methodology/Principal Findings. Prospective, interventional, consecutive case series of 11 eyes with sustained elevation of IOP after SO removal. The mean IOP at baseline, week 1, month 1, month 3, and month 6 was evaluated. The mean baseline IOP was significantly decreased from 25 ± 2.7 mmHg to 18.4 ± 5.5 mmHg at week 1 (P = 0.01), 17.9 ± 3.1 mmHg at month 1 (P = 0.008), 15.8 ± 3.9 mmHg at month 3 (P = 0.003), and 16.2 ± 4.7 mmHg at month 6 (P = 0.004). IOP < 21 mmHg was achieved in 91% of the eyes without a significant complication at month 6. Conclusion/Significance. SLT may be successful for lowering IOP in patients with OAG secondary to emulsified SO which was not controlled with maximum antiglaucomatous medical treatment.

Scanning electron microscopy of the trabecular meshwork: understanding the pathogenesis of primary angle closure glaucoma

PURPOSE

To study ultrastructural changes of the trabecular meshwork in acute and chronic primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) eyes by scanning electron microscopy.

MATERIALS AND METHODS

Twenty-one trabecular meshwork surgical specimens from consecutive glaucomatous eyes after a trabeculectomy and five postmortem corneoscleral specimens were fixed immediately in Karnovsky solution. The tissues were washed in 0.1 M phosphate buffer saline, post-fixed in 1% osmium tetraoxide, dehydrated in acetone series (30-100%), dried and mounted.

RESULTS

Normal trabecular tissue showed well-defined, thin, cylindrical uveal trabecular beams with many large spaces, overlying flatter corneoscleral beams and numerous smaller spaces. In acute PACG eyes, the trabecular meshwork showed grossly swollen, irregular trabecular endothelial cells with intercellular and occasional basal separation with few spaces. Numerous activated macrophages, leucocytes and amorphous debris were present. Chronic PACG eyes had a few, thickened posterior uveal trabecular beams visible. A homogenous deposit covered the anterior uveal trabeculae and spaces. Converging, fan-shaped trabecular beam configuration corresponded to gonioscopic areas of peripheral anterior synechiae. In POAG eyes, anterior uveal trabecular beams were thin and strap-like, while those posteriorly were wide, with a homogenous deposit covering and bridging intertrabecular spaces, especially posteriorly. Underlying corneoscleral trabecular layers and spaces were visualized in some areas.

CONCLUSIONS

In acute PACG a marked edema of the endothelium probably contributes for the acute and marked intraocular pressure (IOP) elevation. Chronically raised IOP in chronic PACG and POAG probably results, at least in part, from decreased aqueous outflow secondary to widening and fusion of adjacent trabecular beams, together with the homogenous deposit enmeshing trabecular beams and spaces.

Auditing orthopaedic audit

INTRODUCTION

Clinical audit plays an important role in the drive to improve the quality of patient care and thus forms a cornerstone of clinical governance. Assurance that the quality of patient care has improved requires completion of the audit cycle. A considerable sum of money and time has been spent establishing audit activity in the UK. Failure to close the loop undermines the effectiveness of the audit process and wastes resources.

PATIENTS AND METHODS

We analysed the effectiveness of audit in trauma and orthopaedics at a local hospital by comparing audit projects completed over a 6-year period to criteria set out in the NHS National Audit and Governance report.

RESULTS

Of the 25 audits performed since 1999, half were presented to the relevant parties and only 20% completed the audit cycle. Only two of these were audits against national standards and 28% were not based on any standards at all. Only a third of the audits led by junior doctors resulted in implementation of their action plan compared to 75% implementation for consultant-led and 67% for nurse-led audits.

CONCLUSIONS

A remarkably large proportion of audits included in this analysis failed to meet accepted criteria for effective audit. Audits completed by junior doctors were found to be the least likely to complete the cycle. This may relate to the lack of continuity in modern medical training and little incentive to complete the cycle. Supervision by permanent medical staff, principally consultants, and involvement of the audit department may play the biggest role in improving implementation of change.

Melanin in the trabecular meshwork is associated with age, POAG but not Latanoprost treatment. A masked morphometric study

We wished to conduct a light and electron microscopic investigation of pigmentation within the trabecular meshwork of normals and primary open angle glaucoma (POAG) patients. In particular we wished to get a precise determination of whether there was a relationship between pigmentation and age. In addition we wanted to know if there was a difference between normals and POAGs and whether trabecular meshwork hyperpigmentation was associated with topical latanoprost medication. A total of 25 sham trabeculectomies conducted on post mortem donor eyes provided the age-matched normals and there were 62 trabeculectomy specimens from POAG patients. These were masked and the meshwork subjected to qualitative and quantitative morphological investigation. Light and electron microscopy confirmed that most of the trabecular meshwork melanin was phagocytosed and within meshwork cells. The granules were measured and found to be of the large iris epithelial type. Light microscopic morphometric analysis showed that the number of meshwork cell profiles that contained melanin increased both in normals and POAGs with age. However there was nearly three times more pigmented meshwork cells in the POAGs than the normals. The POAGs were divided into three groups of (1) minimal or no medication prior to surgery, (2) maximal medical therapy and (3) maximum medical therapy including latanoprost (12 specimens). All groups were significantly greater that the normals but of the three it was the maximal medical therapy group (without latanoprost) that had the highest pigmentation. We concluded that pigmentation of the meshwork is age-related and it is elevated in POAG by mechanisms unknown. The melanin accumulation seems to be partly due to the disease process, partly as a consequence of chronic antiglaucoma medication but interestingly not due to latanoprost even in patients where there is iris darkening (four specimens).

An intravital and confocal microscopic study of the distribution of intracameral antigen in the aqueous outflow pathways and limbus of the rat eye

In a previous investigation into the fate of fluorescently labelled antigen (Ag) injected into the anterior chamber (AC) of the rat eye, a large number of Ag+ cells were noted in the conventional and non-conventional aqueous humour outflow pathways together with the external limbus. The aim of this study was to investigate the precise distribution and phenotype of these cells and compare their ability to capture fluorescent-labelled protein (bovine serum albumin, BSA, and ovalbumin, OVA) and polysaccharides (dextran, Dx) injected into the AC. The density of Ag+ cells in the iris and limbus was investigated using in vivo video fluorescence microscopy 24 hr post-injection. The distribution and phenotype of Ag+ cells in ocular tissues was analysed by confocal microscopy of frozen sections and in iris and corneoscleral/limbal wholemounts from animals sacrificed 24 hr post injection. The general distribution of labelled Ag was equivalent in OVA, BSA and Dx injected animals. Antigen-bearing cells were observed within the iris, iridocorneal angle, pre-equatorial choroid and around limbal/episcleral vessels. Localization of Ag+ cells and free Ag in the anterior segment suggests that substances of these molecular weights (40-70 kDa) leave the eye through the conventional and non-conventional aqueous outflow pathways. The cells that internalized BSA, OVA or Dx in ocular tissues were of a similar phenotype, namely, ED1+, ED2+, occasionally ED3+ and predominantly MHC class II-, thus suggesting that they are of the macrophage phenotype. However, a few Ag+ MHC class II+ dendriform cells (putative DC) were also observed in the iris, trabecular meshwork, choroid and episclera. In conclusion our data reveal that the majority of intracamerally injected soluble Ag retained in the eye is taken up by resident macrophages not only in the iris but in all tissues lining the AC of the eye.

Histology and fine structure of the iris and outflow system following latanoprost therapy

Latanoprost therapy can lead to iris darkening in susceptible individuals, particularly those with hazel eyes. Concerns have been raised about whether latanoprost, and for that matter other prostanoids, may have a harmful effect on the iris. In addition, it is unknown whether latanoprost causes increased pigmentation of the outflow pathways that might eventually lead to blockage and a type of pigmentary glaucoma. The present study summarizes findings from the authors' own laboratories on the effects of latanoprost as seen by light and electron microscopy of the iris and outflow tissues and reviews the as yet limited, relevant literature. The findings support the proposal that latanoprost-induced eye color change is likely to be due to an increased amount of melanin within iris stromal melanocytes rather than any increase in melanocyte numbers, although many aspects of the darkening process remain obscure. No marked pathological changes were found in the latanoprost-treated iris; however, the numbers of specimens examined by us to date are still small (40 specimens in all) and those with latanoprost-induced darkening are even fewer (18). In the authors' experience, pigmentation of the outflow system in latanoprost-treated eyes was no greater than in eyes with primary open-angle glaucoma without prostanoid treatment, but there have been only limited numbers of trabeculectomy specimens examined. Concerns about latanoprost producing meshwork hyperpigmentation and pigmentary glaucoma are discussed.

An audit of audits: are we completing the cycle?

Clinical audit plays an important part in the drive to improve quality of patient care and thus forms a cornerstone of clinical governance. We evaluated the standard of clinical audits conducted by all departments in a teaching hospital between 1996 and 1997. Of a total of 213 audits carried out, 102 (48%) were 'partial' and only 29 (14%) were 'full'. Recommendations for improvement emerged from 134 (63%) of the audits performed. In only 51 audits (24%) was the cycle completed by re-auditing, during the subsequent 3 years. Most departments undertake clinical audits but failure to close the loop undermines their effectiveness and wastes resources.

Morphological variability of the trabecular meshwork in glaucoma patients: implications for non-perforating glaucoma surgery

BACKGROUND/AIMS

Morphological variability of the trabecular meshwork could be of considerable importance for the proper intraoperative outcome of non-perforating antiglaucomatous surgery, such as deep sclerectomy and viscocanalostomy. The aim of this study was therefore to assess qualitative and quantitative characteristics of the trabecular meshwork in glaucoma patients undergoing trabeculectomy.

METHODS

Trabeculectomy specimens from 177 glaucoma patients were prepared for light microscopy; 100 specimens were found to be suitable for qualitative assessment and quantitative computerised image analysis; measurements were taken of the meridional diameter of Schlemm's canal as well as the thickness of the trabecular meshwork at different positions.

RESULTS

The mean meridional diameter of Schlemm's canal was 290 microm with the smallest values in the young patients with infantile and secondary glaucomas. the thickness of the trabecular meshwork ranged between 50-70 microm in the anterior region and between 100-130 microm for the posterior portion. The thickness of the anterior meshwork significantly decreased with age. The pigmentation of excised trabecular meshwork was found to be weak or even lacking in 68 patients. In 20 glaucoma patients the uveal meshwork was covered by an endothelial layer.

CONCLUSIONS

From the morphological point of view the risk of inadvertent perforation during deep sclerectomy in older, white glaucoma patients should be taken into account even by an experienced surgeon, because the anterior meshwork in these cases is very thin and trabecular pigmentation that can be used as a topographic landmark is often lacking. The functional success of non-perforating glaucoma surgery in many patients may be limited by endothelial covering of the trabecular meshwork.

Repair in the rabbit outflow system

An in vivo study was conducted to study repair processes in the injured rabbit outflow system. A uniform injury was produced by raising intraocular pressure (IOP) manometrically to 70 mmHg for 1 h. The recovery process, which was followed clinically for 8 weeks and morphologically for 6 weeks, led to the re-establishment of normal meshwork architecture within this period. The morphological studies included light microscopy, autoradiography and electron microscopy. The initial lesion consisted of large deficits in the meshwork with breakdown of cell-to-cell connections, loss of extracellular materials and disruption of the vessels of the aqueous plexus. There was a significant lowering of IOP in the first week of recovery, which thereafter climbed back to normal. Also in the first week the meshwork became infiltrated with inflammatory cells which cleared by 4 weeks. There was some meshwork cell death by either necrosis or apoptosis. The majority of meshwork cells became activated within the first few days and remained activated for at least the first 2 weeks. Tritiated proline incorporation was maximal between 1 and 2 weeks. Tritiated thymidine labelling was seen throughout, but only after the inflammation subsided was it clear that meshwork cells in all regions of the meshwork were proliferating. Our study provided no evidence that normal meshwork cells have a basal proliferative turnover level. Our injury model involved complete repair of the outflow tissues and that required meshwork cells to become activated, mobilise, undertake synthetic activity and proliferate. This is the first example, other than argon laser trabeculoplasty, where meshwork cells in vivo have been induced to divide. Possible therapeutic implications for glaucoma are discussed.

Secondary glaucoma

PURPOSE: To review the common causes of secondary glaucoma. METHODS: Review of current literature. RESULTS: Secondary open and closed angle glaucomas are an important cause of ocular morbidity and vision loss in our community. Secondary glaucoma occurs with acquired ocular diseases (pigment dispersion, pseudoexfoliation, intraocular infection, intraocular inflammation and retinal vascular disease), blunt anterior segment injury, intraocular surgery (especially corneal grafting and congenital cataract surgery) and topical corticosteroid use. The medical treatment of secondary glaucoma is different from that of primary open angle glaucoma and must be tailored for the individual patient. Surgical treatment of secondary glaucoma carries a higher risk of complications and a lower rate of success than does surgical treatment of primary open angle glaucoma. CONCLUSIONS: Secondary glaucoma occurs with a variety of intraocular conditions and after a variety of intraocular insults. Awareness of patients at high risk should enable early detection and referral for appropriate management.

Effect of trabecular aspiration on intraocular pressure in pigment dispersion syndrome and pigmentary glaucoma

OBJECTIVE

Recently, we described a new form of nonfiltering glaucoma surgery-trabecular aspiration-designed to increase trabecular outflow in pseudoexfoliation glaucoma. This study was carried out to investigate whether trabecular aspiration is equally safe and effective in the treatment of pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG).

STUDY DESIGN

Prospective, nonrandomized comparative trial with historical control.

PARTICIPANTS

Twenty eyes of 20 patients with medically uncontrolled intraocular pressure (IOP) caused by PDS or PG were treated by trabecular aspiration.

INTERVENTION

Trabecular pigment particles were cleared with a pressure of 100 to 200 mmHg using a specially designed aspiration probe.

MAIN OUTCOME MEASURES

The IOP and number of medications before and after surgery were measured. Intraoperative and postoperative complications were analyzed. Surgical success was defined as IOP < or = 21 mmHg with no more than one topical medication. Results were compared with those previously reported with similar treatment of pseudoexfoliative glaucoma.

RESULTS

Mean pretreatment IOP averaged 27.0 (standard deviation [SD], 3.3) mmHg and was significantly reduced to 23.7 (SD, 3.9) mmHg at last follow-up (20.1 +/- 8.6 months). However, the cumulative life-table success rates were only 42% and 15% at 3 and 12 months, respectively. Considering both groups separately, the success rates in the PDS group were 63% and 18% at 3 and 12 months compared with a success rate of 12% in the PG group as early as 1 month after surgery.

CONCLUSIONS

Eyes with PDS responded better to trabecular aspiration than do those with PG, indicating that PDS and PG are two successive stages of the same disease process. Altogether, trabecular aspiration failed to achieve long-term pressure control in either of the two groups.

Ab interno infrared laser trabecular ablation: preliminary short-term results in patients with open-angle glaucoma

BACKGROUND

Outflow obstruction of trabecular drainage structures results in elevation of intraocular pressure (IOP) in various forms of chronic open-angle glaucoma. In vitro studies have shown that laser trabecular ablation (LTA) with opening of Schlemm's canal can be reproducibly performed by use of infrared lasers with minimal damage to collateral tissue structures.

METHODS

In order to investigate the clinical applicability and efficacy of ab interno contact laser photoablation of trabecular meshwork in the surgical treatment of human glaucoma, we conducted a pilot study using an erbium: YAG laser (2.94 microns) with a quartz fiber endoprobe (320 microns core diameter) applying 10-20 single laser pulses (5-7 mJ) to the trabecular meshwork.

RESULTS

Under goniocopic visualization trabecular tissue was photovaporized in eight patients with primary or secondary chronic open-angle glaucoma. Intraoperatively, moderate reflux bleeding occurred from laser-induced craters. No major intra- or postoperative complications occurred. Preoperative and postoperative gonioscopy of the treated area demonstrated successful removal of trabecular tissue. Mean IOP was reduced from 36.1 mmHg ot 21.3 mmHg at a limited follow-up of 3 months.

CONCLUSION

With modifications this technique may have clinical potential in the surgical management of glaucoma. Prospective long-term studies with more patients are warranted to evaluate the outcome of LTA.

Neovascular tissue in the intertrabecular spaces in eyes with neovascular glaucoma

AIMS/BACKGROUND

To investigate histological changes in the trabecular meshwork in eyes with neovascular glaucoma.

METHODS

Light and electron microscopic studies were carried out on the trabecular meshwork of three enucleated eyes with neovascular glaucoma. The presence and distribution of factor VIII in the trabecular meshwork was assessed using the ABC method.

RESULTS

Peripheral anterior synechiae covering the trabecular meshwork were detected in two eyes, which would explain the rise in intraocular pressure. In the third the angle was not completely closed by peripheral anterior synechiae. The spaces between the trabecular beams were lined by a single layer of vascular endothelium, and were filled with red blood cells in this patient. Factor VIII was positively stained in the endothelial cells, lining both these spaces and Schlemm's canal. A basal lamina and microfibrils were detected just beneath the newly formed vascular endothelial cells.

CONCLUSION

The neovascular tissue found in the trabecular spaces might be one of the factors responsible for intraocular pressure elevation in eyes with neovascular glaucoma.