Advances in biometrics of the morphology of Schlemm canal / 中华实验眼科杂志

Schlemm canal is an important part of the aqueous humor outflow pathway and a circular canal around the angle of anterior chamber.Its inner wall was separated by a layer of endothelial cells with trabecular meshwork, and its outer wall was drained by 25-30 collector channels.At present, it is considered that Schlemm canal is the main part of resistance to aqueous humor outflow and plays a vital role in the regulation of intraocular pressure.The collapse of Schlemm canal will cause the increase of intraocular pressure, which will lead to the damage of fundus oculi and the occurrence of glaucoma.With the development of minimally invasive glaucoma surgeries, Schlemm canal has become a significant part in anti-glaucoma surgery.Therefore, the morphological observation of Schlemm canal is particularly important.With the development of imaging technology, mainly ultrasound biomicroscope and optical coherence tomography, the study on the morphology of Schlemm canal has developed from the initial histological study of isolated eye by light microscope and electron microscope in vitro to the imaging observation in vivo.In this review, the morphology and physiological function of Schlemm canal in aqueous humor outflow pathway and the biometrics of its morphology were described.

The Effect of Interleukin-1alpha on Trabecular Outflow Resistance in Rat Eyes

It was investigated if regulation of the trabecular extracellular matrix tumover rate and remodeling plays an important role in decreasing outflow resistance by determining the effect of intracamerally given interleukin-1alpha a known stimulator of the expression of trabecular matrix metallopro-teinases, on outflow facility of albino rat eyes. Forty normal albino rats (Sprague dawley) weighing 250 to 300gm were studied. Rats were anesthetized by intraperitoneal pentobarbital sodium(30mg/kg) injection. The rats were grouped into 4 groups and given 5, 10, 25, 50 units of interleukin-1alpha injected intracamerally in one eye of each rat. Bovine serum albumin in phosphate buffered saline, which was used to dissolve the interleukin-1alpha, was injected in the other eye as a control. Outflow facility was measured by two level constant pressure perfusion at 1, 3, and 7 days after injection. The eyes treated with 50 units of interleukin-1alpha showed a statistically significant increase of outflow facility by 37% compared to the contralateral control eyes at 3 days after injection, but retumed to normal level in 7 days. The eyes treated with 5, 10, 25, 50 units of interleukin-1alpha increased the outflow facility, supporting the hypothesis that regulation of trabecular meshwork extracellular matrix plays a role in trabecular outflow resistance.

The Effects of Topical Cyclosporin A on Glaucoma Drainage Implant Surgery in Rabbits

To assess the effects of topical cyclosporin A(Csa) on the function of fibrous capsule and fibroblast proliferation after glaucoma drainage implant surgery in rabbits, we compared intraocular pressure(IOP), outflow resistance through the capsule and fibroblast density in capsule and fibroblast density in capsule among three groups: group A(12 eyes) that received implant surgery only, group B(11eyes) trated with topical 2% CsA twice a day for 2 weeks after implant surgery, and group C(14 eyes) with intraoperative subcon-junctival soaking of 2% CsA for S minutes and postoperative topical 2% CsA twice a day for 2 weeks. There was significant postoperative IOP decreases at 2, 4 and 8 weeks in group B(7.3 +/- 2.0. 7.1 +/- 1.7, and 6.6 +/- 1.8 mmHg, respectively) and group C(7.8 +/- 2.6, 7.1 +/- 1.7, and 6.8 +/- 1.6 mmHg, respectively) compared with group A(5.1 +/- 1.7, 5.0 +/- 1.0, and 4.8 +/- 1.5 mmHg, respectively)(p0.05 for each). Fibroblast density was not significantly lower in group B and Group C than in group A(n=3, p=0.08). These results suggest adjunctive topical CsA may enhance the effectiveness of glaucoma drainage implant surgery.

Review of Constant Infusion Method of Cerebrospinal Fluid Outflow Resistance Study

The author has performed the experimental study to define the validity of the constant infusion technique used in determining the outflow resistance(Ro) of cerebrospinal fluid(CSF). The reduced formula of the constant infusion technique in clinical setting assume that the initial resing Ro and the post-infusion equilibrium Ro are equal, which means that the Ro value is constant regardless of CSF pressure or infusion rate. Although this assumption allows such measurement to be simply and readily applicable in clinical situation, these two Ro values are practically different. So the effect such assumption on calculated Ro data has been investigated. Using 2 different methods Ro was measured simultaneously on each of 20 adult cats;one method was clinically using reduced formula(RoFc) and the other derived from the data of CSF formation rate which was calculated by modified Masserman's method(RoFm). Constant infusion was performed with varying state of infusion(0.01 to 0.2 m/min). Mean values of resting CSF pressure and superior sagittal sinus pressure were 8.8+/-2.9 mmHg and 5.7+/-1.2 mmHg respectively. Mean calculated rate of CSF formation of integrative modifiying Massereman method was 0.0183+/-0.003 ml/min. The maximum Ro was achieved between the rate of infusion of 0.02 and 0.03 ml/min achieved between the range of CSF pressure of 14 and 18 mmHg. Either in level of low CSF pressure or in rate of low infusion, RoFc showed remarkable higher values than RoFm. But this difference did not distinguished in the higher range of CSF pressure or infusion rate. The minmum and maxmum value of RoFc differed the more and RoFm, the less. These findings suggest that in order to obtain more accurate Ro data with constant infusion technique, it must be corrected in low range of CSF pressure or the rate of infusion should be increased several times as that of CSF formation at the risk of possibility of induction of a pressure wave.