Ocular rigidity and outflow facility in nonproliferative diabetic retinopathy.

PURPOSE: To compare ocular rigidity (OR) and outflow facility (C) in patients with nonproliferative diabetic retinopathy (NPDR) and control subjects. METHODS: Twenty-four patients with NPDR (NPDR group) and 24 controls (control group) undergoing cataract surgery were enrolled. NPDR group was further divided into patients with mild NPDR (NPDR1-group) and patients with moderate and/or severe NPDR (NPDR2-group). After cannulation of the anterior chamber, a computer-controlled device was used to infuse saline and increase the intraocular pressure (IOP) in a stepping procedure from 15 to 40 mmHg. Ocular rigidity and outflow facility coefficients were estimated from IOP and volume recordings. RESULTS: Ocular rigidity was 0.0205 µL(-1) in NPDR group and 0.0202 µL(-1) in control group (P = 0.942). In NPDR1-group, OR was 0.017 µL(-1) and in NPDR2-group it was 0.025 µL(-1) (P = 0.192). Outflow facility was 0.120 µL/min/mmHg in NPDR-group compared to 0.153 µL/min/mmHg in the control group at an IOP of 35 mmHg (P = 0.151). There was no difference in C between NPDR1-group and NPDR2-group (P = 0.709). CONCLUSIONS: No statistically significant differences in ocular rigidity and outflow facility could be documented between diabetic patients and controls. No difference in OR and C was detected between mild NPDR and severe NPDR.

Ocular rigidity, outflow facility, ocular pulse amplitude, and pulsatile ocular blood flow in open-angle glaucoma: a manometric study.

PURPOSE: To compare ocular rigidity (OR) and outflow facility (C) coefficients in medically treated open-angle glaucoma (OAG) patients and controls, and to investigate differences in ocular pulse amplitude (OPA) and pulsatile ocular blood flow (POBF) between the two groups. METHODS: Twenty-one OAG patients and 21 controls undergoing cataract surgery were enrolled. Patients with early or moderate primary or pseudoexfoliative OAG participated in the glaucoma group. A computer-controlled system, consisting of a pressure transducer and a microstepping device was employed intraoperatively. After cannulation of the anterior chamber, IOP was increased by infusing the eye with microvolumes of saline solution. IOP was recorded after each infusion step. At an IOP of 40 mm Hg, an IOP decay curve was recorded for 4 minutes. OR coefficients, C, OPA, and POBF were estimated from IOP and volume recordings. RESULTS: There were no differences in age or axial length in the two groups. The OR coefficient was 0.0220 ± 0.0053 µl(-1) in the OAG and 0.0222 ± 0.0039 µl(-1) in the control group (P = 0.868). C was 0.092 ± 0.082 µL/min/mm Hg in the glaucoma group compared with 0.149 ± 0.085 µL/min/mm Hg in the control group at an IOP of 35 mm Hg (P < 0.001) and 0.178 ± 0.133 µL/min/mm Hg vs. 0.292 ± 0.166 µL/min/mm Hg, respectively, at an IOP of 25 mm Hg (P < 0.001). There were no differences in OPA or POBF between the two groups in baseline and increased levels of IOP (P > 0.05). CONCLUSIONS: Manometric data reveal lower C in OAG patients and increased C with increasing IOP. There were no differences in the OR coefficient, OPA, and POBF between medically treated OAG patients and controls, failing to provide evidence of altered scleral distensibility and choroidal blood flow in OAG.

Ocular rigidity, ocular pulse amplitude, and pulsatile ocular blood flow: the effect of axial length.

PURPOSE: Previous studies have shown a negative correlation between axial length (AL) and pulsatile ocular blood flow (POBF). This relation has been questioned because of the possible confounding effect of ocular volume on ocular rigidity (OR). The purpose of this study was to investigate the relation between AL, as a surrogate parameter for ocular volume, and OR, ocular pulse amplitude (OPA), and POBF. METHODS: Eighty-eight cataract patients were enrolled in this study. A computer-controlled device comprising a microdosimetric pump and a pressure sensor was used intraoperatively. The system was connected to the anterior chamber and used to raise the intraocular pressure (IOP) from 15 to 40 mm Hg, by infusing the eye with a saline solution. After each infusion step, the IOP was continuously recorded for 2 seconds. Blood pressure and pulse rate were measured during the procedure. The OR coefficient was calculated from the pressure volume data. OPA and POBF were measured from pressure recordings. RESULTS: Median AL was 23.69 (interquartile range 3.53) mm. OR coefficient was 0.0218 (0.0053) µL(-1). A negative correlation between the OR coefficient and AL (ρ = -0.641, P < 0.001) was documented. Increasing AL was associated with decreased OPA (ρ = -0.637, P < 0.001 and ρ = -0.690, P < 0.001) and POBF (ρ = -0.207, P = 0.053 and ρ = -0.238, P = 0.028) at baseline and elevated IOP, respectively. CONCLUSIONS: Based on manometric data, increasing AL is associated with decreased OR, OPA, and POBF. These results suggest decreased pulsatility in high myopia and may have implications on ocular pulse studies and the pathophysiology of myopia.