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.

Inmunohistoquímica de factores de crecimiento en trabéculos de pacientes glaucomatosos: resultados preliminares en pacientes con glaucoma primario de ángulo abierto / Growth factors' immunohistochemistry in trabecular tissue of glaucoma patients: preliminar results in patients with primary open angle glaucoma

Las alteraciones ultraestructurales en el glaucoma primario de ángulo abierto (GPAA) se relacionan con cambios a nivel celular y de la matriz extracelular en el tejido trabecular y pericanalicular. Los factores de crecimiento (FC) actúan como señales químicas que difunden desde las células produciendo cambios en la composición, estructura y función de la matriz extracelular. El propósito de este estudio fue describir, con la ayuda de la inmunohistoquímica, la presencia de factores de crecimiento y sus receptores en el tejido trabecular. Nuestras observaciones son sugerentes de la presencia de factor de crecimiento fibroblástico (FGF) y de su receptor (FGFr) en células trabeculares de pacientes con GPAA

Intraocular pressure following peritomy and wet-field coagulation

The changes in intraocular pressure (IOP) following peritomy and wet-field coagulation of 10 rabbit eyes and 7 human cataractous eyes were investigated. The IOP difference before and after 180-degree and 360-degree wet-field coagulation on rabbit eyes showed an average increase of 11.0 +/- 5.8 mmHg and 25.8 +/- 7.1 mmHg(mean +/- SD), respectively (p < 0.05, p < 0.01). The IOP of both groups in rabbit eyes were elevated for 2 to 3 days postoperatively and then became normal by the 7th postoperative day. The IOP difference before and after 180-degree peritomy and wet-field coagulation in human cataractous eyes showed an average increase of 8.4 +/- 5.8 mmHg(mean +/- SD)(p < 0.05). The outflow facility was poor immediately following wet-field coagulation but then improved gradually by means of tonography and concentration changes of anterior chamber neutral-red. Histologically, there was endothelial cell damage, congestion, and red blood cell extravasation of the episcleral and intrascleral vessels at one day after wet-field coagulation in the light microscopic findings. Recanalization of the episcleral and intrascleral capillaries was noted 3 days after wet-field coagulation and was completed 3 weeks after wet-field coagulation. There was poor plastic infusion through the trabecular spaces in the one-day postoperative group compared to the control group by scanning electron micrograph. In conclusion, we have to bear in mind the possibility of an IOP rise after wet-field coagulation following peritomy for cataract and retinal surgery.

Early effect of argon laser trabeculoplasty on human meshwork: an electron microscopic study

An electron microscopic study, using transmission electron microscopy, was performed on trabeculectomy specimens obtained from human phakic eyes scheduled for trabeculectomy for uncontrolled primary open angle glaucoma, few hours to one week after Argon Laser Trabeculoplasty [ALT]. The early results showed disruption of trabecular beams, coagulative necrosis within the beam core, rupture of the endothelial cells covering the beam and heavy dispersion of tissue dibris and pigment granules. The one week specimens showed collagen fiber deposition as well as decrease in tissue debris. The cornea! endothelium nearby the laser site was damaged. No inflammatory cells were seen in any of the specimen examined

Análisis ultraestructural de las poblaciones celulares del trabéculo en la aniridia / Ultrastructural analysis of the celular population of the trabeculo in aniridia

El glaucoma que complica a la aniridia se debe generalmente a cambios post natales que se agregan a alteraciones determinadas congénitamente. Menos frecuente es el glaucoma congénito asociado a la aniridia. El principal cambio post natal es el cierre angular progresivo que finalmente termina adosando el muñón iridiano a la pared interna del trabéculo, alterando su función y determinando glaucoma. La patogenia que determina esta modificación morfológica y cierre angular es desconocida. El presente trabajo describe la proliferación de melanocitos en la superficie interna del trabéculo, espacios trabeculares, tejido yuxtacanalicular, pared externa del conducto de Schlemm y conductos colectores esclerales. Esta proliferación no ha sido descrita previamente en la aniridia y podría explicar las modificaciones angulares que llevan al glaucoma por cierre angular secundario en estos casos. Es probable que este mecanismo patogénico sea responsable de la refractariedad a los distintos tipos de tratamiento descritos en el glaucoma asociado a aniridia desde que el aspecto de las trabéculas, el conducto de Schiem y conductos colectores son aparentemente normales

Microscopia electrónica del trabéculo en la aniridia / Electron microscopy of the trabecular in aniridia

El glaucoma que complica a la aniridia se debe generalmente a cambios post natales que se agregan a alteraciones determinadas congénitamente. Menos frecuentemente el glaucoma es congénito. El principal cambio post natal observado es el cierre angular progresivo que finalmente termina adosando el muñón iridiano a la pared interna del trabéculo alterando su función y determinando el glaucoma. La patogenia que determina esta modificación morfológica y cierre angular es desconocida. El presente trabajo describe la proliferación de melanocitos en la superficie interna del trabéculo, espacios trabeculares, tejido yuxtacanalicular, pared externa del canal de Schlemm y canales colectores esclerales. Esta proliferación no ha sido descrita previamente en la aniridia y podría explicar las modificaciones angulares en la aniridia que llevan al glaucoma por cierre angular secundario. Es probable que este mecanismo patogénico exista en el glaucoma asociado a aniridia y sea responsable de la refractariedad a los distintos tipos de tratamientos descritos. Los espacios trabeculares existen al igual que trabéculas normales, canal de Schlemm y canales colectores