The effect of intraocular pressure on resistance to outflow

Moses, Robert A.

doi:10.1016/0039-6257(77)90088-1

Cited by 84 publications

(47 citation statements)

References 87 publications

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“…The perfusion pressure was adjusted to be between 6 and 23 mmHg (see Table I). In early experiments, the perfusion needle was placed into the posterior chamber of the eye to avoid artificially deepening the anterior chamber and thus decreasing outflow resistance (Moses, 1977) : however, since no significant difference was seen in the percentage of microspheres passing through the aqueous outflow system with the needle in the anterior chamber versus the posterior chamber (Johnson, 1987), most of the later experiments had the infusion needle in the anterior chamber. Details can be found in Table 1.…”

Section: Methodsmentioning

confidence: 99%

The filtration characteristics of the aqueous outflow system

Johnson

Kamm

et al. 1990

Experimental Eye Research

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To determine the filtration characteristics of the aqueous outflow system, microspheres (0.18 pm-l.1 pm) were perfused through enucleated human and bovine eyes. The microspheres were smaller than morphologically determined flow dimensions, and yet a significant fraction of all sizes of microspheres were captured. The bovine (calf) aqueous outflow system was found to be a far more efficient filter than was the human outflow system.Combining the experimental results with morphological observations and theoretical calculations leads to the conclusion that 'sticky wall' interactions are responsible for much of the microsphere capture, and that the site of filtration may be distinct from the site of flow resistance. Consequently, the dimension of the sites generating flow resistance cannot be determined from filtration studies.

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Section: Methodsmentioning

confidence: 99%

The filtration characteristics of the aqueous outflow system

Johnson

Kamm

et al. 1990

Experimental Eye Research

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“…There is evidence that outflow resistance increases as a function of pressure in living animal eyes or enucleated human eyes (Moses, 1977). Van Buskirk (1982) found that pressure-dependent outflow obstruction was related to the collapse of Schlemm's canal (SC) under pressure.…”

Section: Living Monkey Eyesmentioning

confidence: 99%

Factors affecting outflow facility calculations

Tian

Gabelt

et al. 2006

Experimental Eye Research

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Outflow facility (C), a ratio of outflow rate (F) to relevant pressure, is an important indication of outflow resistance in the ocular drainage pathway. The higher the C, the lower the outflow resistance. According to the classic Goldmann equation, C=F/(IOP-P e )(IOP, intraocular pressure; P e , episcleral venous pressure). Since anterior chamber (AC) perfusions directly measure outflow and are less affected by scleral creep and rigidity or changes in uveal blood content than repeated tonography in living eyes, they are widely used to determine C in living animals or cultured anterior segments from enucleated eyes. Bárány (1964) initially developed the 2-level constant pressure perfusion technique for living monkey eyes to avoid possible influences of changes in eye parameters (e.g., P e , spontaneous IOP [P 0 ] or aqueous humor formation [AHF]) on C measurements. However, since these eye parameters do not exist in cultured anterior segments, 1-level constant pressure perfusion (Erickson-Lamy et al., 1991) and constant flow rate perfusion (Johnson and Tschumper, 1987) are typically used to determine C in organ culture. Based on different perfusion techniques, two basic formulas derived from the Goldmann equation are used to calculate C: (A) C=(F 2 -F 1 )/(P 2 -P 1 ), which is usually used in 2-level constant pressure perfusion either in living animals or in cultured anterior segments (F 1 or F 2 represents F at P 1 [lower perfusion pressure] or P 2 [higher perfusion pressure]); (B) C=F/P, which is usually used in 1-level constant pressure perfusion or constant flow rate perfusion in cultured anterior segments (P, perfusion pressure; P e is ignored in this formula because it is assumed to be zero in the cultured anterior segments). A comparison of C values calculated using Formula B and the data obtained during 2-level constant pressure perfusion in vivo or in vitro requires the following modifications: C=F 1 /(P 1 -P 0 ) or C=F 2 /(P 2 -P 0 ) where F 1 or F 2 is due to the change in pressure from P 0 to P 1 or P 2 (P 0 is assumed to be stable during short-term perfusions in vivo and is zero in vitro). C values from the same eye and the same perfusion are often quite different when calculated by the two formulas, since Formula A calculates C for the change in pressure from P 1 to P 2 , whereas Formula B calculates C either for the change in pressure from P 0 to P 1 or P 2 in living eyes or for a given pressure (P 1 or P 2 ) in cultured segments. However, the difference has not been clearly stated in previous studies, so that confusion might occur when comparing C values obtained by the two formulas. Additionally, C at different pressures may also be affected by factors physiologically unrelated to the formulas. To determine factors that may affect C values and to evaluate the significance of these factors in aqueous humor dynamics research, we compared C values calculated by Formulas A and B based on some previous perfusion experiments.

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“…Primary open angle glaucoma (POAG) is a late-onset disease commonly accompanied by elevated intraocular pressure (IOP) that results from the progressive failure of the trabecular meshwork (TM)-Schlemm's canal (SC) conventional outflow pathway tissue to maintain normal levels of aqueous humor outflow resistance (Moses, 1977). Although it is believed that POAG results from a combination of genetic and environmental factors (Wang et al, 2001;Klein et al, 2004), the specific causes of the malfunction of the outflow pathway in POAG have not yet been determined.…”

Section: Introductionmentioning

confidence: 99%

Cellular senescence in the glaucomatous outflow pathway

Liton

Challa

Stinnett

et al. 2005

Experimental Gerontology

166

106

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The mechanisms responsible for the progressive malfunction of the trabecular meshwork (TM)-Schlemm's canal (SC) conventional outflow pathway tissue in primary open angle glaucoma (POAG) are still not fully understood. To determine whether POAG is characterized by an accumulation of senescent cells, similar to what has been described in other diseases, we have compared the levels of the senescence marker senescence-associated-β-galactosidase (SA-β-gal) in the outflow pathway cells of POAG and age-matched control donors. POAG donors demonstrated a statistically significant fourfold increase in the percentage of SA-β-gal positive cells. These results suggest a potential role for cellular senescence in the pathophysiology of the outflow pathway.

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The effect of intraocular pressure on resistance to outflow

Cited by 84 publications

References 87 publications

The filtration characteristics of the aqueous outflow system

The filtration characteristics of the aqueous outflow system

Factors affecting outflow facility calculations

Cellular senescence in the glaucomatous outflow pathway

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