Ocular haemodynamics in cataractous eyes. A pilot study

Optic nerve head microvascular changes after phacoemulsification surgery

BACKGROUND

To determine optic nerve head (ONH) microvascular changes detected by optical coherence tomography angiography (OCTA) and intraocular pressure changes (IOPs) after uncomplicated phacoemulsification surgery.

METHODS

The study was designed as a prospective observational study. Twenty-four eyes were included. Eyes with retinal vascular pathology, any type of age-related macular degeneration, IOP more than 21 mmHg, axial length less than 20 mm and more than 24 mm, corneal edema and cataracts that can disrupt images, and history of ocular surgery were excluded. Patients underwent OCTA imaging and IOP measurement preoperatively (baseline) and postoperatively (weeks 1 and 4). Vessel density % (VD) in the total disc, peripapillary, and inside disc were measured. IOP was measured with the applanation tonometer. Comparison of VD and IOP and correlation between VD and İOP change were determined.

RESULTS

VD was significantly increased in all quadrants in week 4 compared to those in week 1. In terms of VD and IOP, although there was no significant difference between week 1 and baseline, week 4 results were significantly different from baseline (p < 0.05 and p < 0.001, respectively). The IOP was significantly lower in week 4 (14.8 mmHg) than in week 1 (16.0 mmHg) (p < 0.001). There was a significant negative correlation between the inside disc and total VD and IOP at weeks 1 and 4.

CONCLUSION

Phacoemulsification surgery can result in a decrease in IOP and an increase in VD of the ONH.

Effects of phacoemulsification surgery on ocular hemodynamics

AIM

To evaluate the possible effects of phacoemulsification cataract surgery on ocular hemodynamics.

METHODS

In this prospective study, intraocular pressure (IOP), pulsatile ocular blood flow (POBF), and ocular pulse amplitude (OPA) were measured pre-operatively (baseline) and at 1 week and 3 weeks postoperation in 52 eyes of 26 patients (mean age 63.15±10.25 years) scheduled for unilateral phacoemulsification cataract surgery with intraocular lens implantation. In all of the eyes, a blood flow analyzer (Paradigm DICON; Paradigm Medical Industries Inc.; USA) was used to obtain measurements of IOP, POBF, and OPA. The data obtained from operated eyes were compared statistically to untreated fellow phakic eyes of the patients.

RESULTS

For operated eyes, the mean baseline IOP, POBF, and OPA values were 15.9±4.64mmHg, 17.41±4.84µL/s, and 2.91±1.12mmHg, respectively. The IOP, POBF, and OPA values were 17.19±4.34mmHg, 17.56±6.46µL/s, and 3.12±1.1mmHg, respectively, in the nonoperated control eyes. Statistically significant differences from baseline measurements were not observed 1 week and 3 weeks postoperation for the operated or nonoperated eyes. There were also no statistically significant differences in any measurements between the operated and nonoperated eyes in all the examination periods (P>0.05 for all).

CONCLUSION

Uncomplicated phacoemulsification surgery does not affect ocular hemodynamics in normotensive eyes with cataracts.

Effects of Transient Mild Systemic Hypoxia on the Pulsatile Choroidal Blood Flow in Healthy Young Human Adults

PURPOSE

To investigate the effects of transient mild systemic hypoxia on the pulsatile ocular blood flow (POBF) in the healthy young adult.

METHODS

Two measurements of the intraocular pressure (IOP) pulses, used to derive the POBF, were recorded from 19 subjects before, during, and after breathing 12% oxygen in nitrogen. Many physiological variables were also assessed throughout testing.

RESULTS

Transient mild systemic hypoxia decreased the hemoglobin oxygen saturation and end-tidal carbon dioxide, increased the heart rate, but did not change the respiratory rate, systemic blood pressure, or ocular perfusion pressure. Mild systemic hypoxia decreased the intraocular pulse volume and the systolic and diastolic times but did not alter the pulse amplitude or the POBF. The IOP was not altered during mild systemic hypoxia.

CONCLUSIONS

The absence of change in the POBF during transient mild systemic hypoxia indicated that the global pulsatile choroidal blood flow was not vulnerable to the effects of this transient mild systemic hypoxic stress in the healthy young adult.

Ocular blood flow measurement

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The effect of posture on intraocular pressure and pulsatile ocular blood flow in normal and glaucomatous eyes

While an increase in the intraocular pressure on assumption of the supine position from the seated or upright position has been known for decades, the recent introduction of a means to quantify the pulsatile ocular blood flow has led to studies indicating a postural decrease in the pulsatile ocular blood flow. The factors contributing to the postural response of the intraocular pressure are reviewed, and those proposed for the postural response of the pulsatile ocular blood flow are discussed.

Differences in the longterm effect of timolol and betaxolol on the pulsatile ocular blood flow

In the past several years the effect of longterm glaucoma therapy on ocular hemodynamics has taken on increased interest. This interest has been sparked by studies demonstrating differential effects of various beta-blockers on visual function, and the possible contributory role of ocular blood flow. In the present study, the pulsatile ocular blood flow (POBF), as derived by the Langham OBF system, was measured prior to treatment and then tracked throughout a one-year period of beta-blocker therapy (betaxolol 0.5% or timolol 0.5%) in 25 glaucoma patients. Results of the two treatments were compared, and indicated that, whereas both betaxolol- and timolol-treated patients had similar significant reductions in the IOP, the effect of the two treatments on the POBF differed. In timolol-treated patients, the POBF decreased significantly over the 12-month observation period, whereas in betaxolol-treated patients it remained stable.