A Study of Aqueous Humor Dynamics in Keratoconus

Goodman, W.T.; Mathers, William D.; Munden, Paul M.; Ossoinig, Karl C.; Daley, Thomas E.

doi:10.1006/exer.1996.0011

Cited by 7 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Goodman et al hypothesized that an increased aqueous humor outflow (i.e., vitreous body outflow in Fig. 1(a)) is the reason for reduced intraocular pressure in keratoconic eyes (Goodman et al, 1996). The increase in outflow is most certainly caused by the reported changes in structure and composition.…”

Section: Mechanical Parametersmentioning

confidence: 96%

The effect of keratoconus on the structural, mechanical, and optical properties of the cornea

Ambekar

Toussaint

Johnson

2011

Journal of the Mechanical Behavior of Biomedical Materials

117

View full text Add to dashboard Cite

Section: Mechanical Parametersmentioning

confidence: 96%

The effect of keratoconus on the structural, mechanical, and optical properties of the cornea

Ambekar

Toussaint

Johnson

2011

Journal of the Mechanical Behavior of Biomedical Materials

117

View full text Add to dashboard Cite

“…Previous studies investigating IOP in keratoconus using applanation tonometric techniques have highlighted the potential inaccuracies of these measures in keratoconus and typically note that patients with keratoconus exhibit lower than normal IOP (Brooks et al. 1984; Swann & Waldron 1986; Edmonds 1993; Goodman et al. 1996; Böhm et al.…”

Section: Introductionmentioning

confidence: 99%

Intraocular pressure in keratoconus

Read

Collins

2011

Acta Ophthalmologica

View full text Add to dashboard Cite

ABSTRACT.Purpose: This study aimed to investigate intraocular pressure (IOP) measurements taken using the dynamic contour tonometer (DCT) and the non-contact tonometer (NCT) in subjects with keratoconus. Methods: Intraocular pressure was measured in 20 keratoconus subjects and 20 age-matched control subjects using the DCT and NCT instruments. Central and off-centre measures were taken with the DCT in order to highlight any systematic errors associated with corneal biomechanical factors. Measures of anterior and posterior corneal topography and thickness were also taken in each subject. Results: No significant difference was found between the central and off-centre DCT IOP readings for the keratoconus subjects and age-matched controls (p > 0.05). The average DCT IOP was 14.2 ± 1.4 mmHg in the keratoconus subjects and 14.2 ± 1.6 mmHg in the controls. However, the average NCT readings differed significantly (p < 0.001) between the keratoconus subjects (9.2 ± 1.5 mmHg) and the controls (12.9 ± 2.4 mmHg). Intraocular pressure measurements taken with the DCT showed no significant (p > 0.05) correlation with the severity of keratoconus as determined through measures of corneal topography and thickness. Equivalent IOP measurements taken with the NCT correlated significantly with certain measures of corneal curvature and thickness in the keratoconus population. The difference between DCT and NCT IOP was strongly correlated with measures of corneal topography and thickness, with differences increasing in more advanced keratoconus. Conclusions: The measurements obtained with the DCT do not appear to be dependent upon corneal factors, unlike those taken with the NCT. The presence or severity of keratoconus was not correlated with DCT IOP values.

show abstract

“…The aqueous humor (AqH) fills entirely the anterior chamber of the human eye. It is continuously exchanged at the rate 2.2–2.8 μL min −1 (1,2) supplying nutrients to the nonvascularized cornea, lens and trabecular meshwork (3). Normally, the AqH is well protected against oxidative stress that may occur in this anterior segment of the eye, by antioxidant enzymes (4), chelating proteins, amino acids (9 μ m l ‐cysteine and l ‐tyrosine) and antioxidants such as 1.9–16 μ m glutathione (5) and 0.8–2.5 m m ascorbate (4,6–9).…”

Section: Introductionmentioning

confidence: 99%

Ascorbate Enhances Photogeneration of Hydrogen Peroxide Mediated by the Iris Melanin^†

Wielgus

Sarna²

2008

Photochem & Photobiology

View full text Add to dashboard Cite

The iris in the human eye is exposed to UV and visible light transmitted by the cornea. This pigmented tissue is bathed with the aqueous humor (AqH), which contains high concentration of ascorbate. It has been postulated that the presence of ascorbate in AqH can contribute to increased photoproduction of H2O2 mediated by the iris melanin. In this study, we monitored generation of H2O2 induced by UV-VIS irradiation of bovine irides, bovine and human iris homogenates and iris melanin. Our data show that exogenous ascorbate significantly amplified the rate of H2O2 photoformation in all melanotic samples. Deactivation of endogenous catalase with NaN3 in bovine irides increased the level of the accumulated H2O2 in the bathing solution following sample irradiation. Photoformation of H2O2 in samples with exogenous ascorbate was accompanied by its photo-oxidation. Both photoprocesses exhibited significant wavelength dependence. EPR spectroscopy measurements showed that ascorbyl radical is an intermediate product of the ascorbate photo-oxidation. The photoproduction of H2O2 and photo-oxidation of ascorbate appear to be stoichiometric processes. No significant differences in the photoreactivity of iridial melanin from donors of different age and iris color was found. We postulate that also in vivo ascorbate increases the rate of iris melanin-mediated photoformation of H2O2 and its steady state concentration in AqH.

show abstract

A Study of Aqueous Humor Dynamics in Keratoconus

Cited by 7 publications

References 0 publications

The effect of keratoconus on the structural, mechanical, and optical properties of the cornea

The effect of keratoconus on the structural, mechanical, and optical properties of the cornea

Intraocular pressure in keratoconus

Ascorbate Enhances Photogeneration of Hydrogen Peroxide Mediated by the Iris Melanin^†

Contact Info

Product

Resources

About

A Study of Aqueous Humor Dynamics in Keratoconus

Cited by 7 publications

References 0 publications

The effect of keratoconus on the structural, mechanical, and optical properties of the cornea

The effect of keratoconus on the structural, mechanical, and optical properties of the cornea

Intraocular pressure in keratoconus

Ascorbate Enhances Photogeneration of Hydrogen Peroxide Mediated by the Iris Melanin†

Contact Info

Product

Resources

About

Ascorbate Enhances Photogeneration of Hydrogen Peroxide Mediated by the Iris Melanin^†