Effect of breath-holding on pulsatile ocular blood flow measurement in normal subjects

The Association between Adiposity and the Risk of Glaucoma: A Meta-Analysis

Purpose

This meta-analysis was conducted to determine the potential association between adiposity and glaucoma incidence.

Materials and Methods

A comprehensive literature search was performed in PubMed and ISI Web of Science. A meta-analysis was conducted using STATA software.

Results

Fifteen eligible studies involving 2,445,980 individuals were included to investigate the association between adiposity and glaucoma incidence. The relative risks (RRs) were pooled with 95% confidence intervals (CI) by using a random-effects model. The pooled RR between adiposity and elevated intraocular pressure (IOP) was 1.73 (95% CI, 1.18–2.54), whereas that between adiposity and open-angle glaucoma (OAG) was 0.97 (95% CI, 0.83–1.13). The pooled RR between abdominal adiposity and glaucoma was 1.28 (95% CI, 1.15–1.41), whereas that between general adiposity and glaucoma was 1.09 (95% CI, 0.87–1.37). Results of subgroup analysis by sex indicated the association between adiposity and glaucoma in the female group (RR, 1.31; 95% CI, 1.05–1.64), but not in the male group (RR, 1.11; 95% CI, 0.77–1.60). The pooled RR of cohort studies and cross-sectional studies were 1.00 (95% CI, 0.84–1.20) and 1.22 (95% CI, 0.89–1.66), respectively.

Conclusions

Adiposity has a higher risk of elevated IOP, and abdominal adiposity has a positive association with glaucoma, especially in female patients.

Ocular changes during pregnancy

BACKGROUND

Most ocular changes in pregnancy are harmless. For example, 14% of pregnant women need a new eyeglass prescription. Some changes, however, are serious, such as retinal effects of hypertension, which can be a sign of pre-eclampsia. Ocular changes may give rise to uncertainty about the administration of ophthalmological drugs or the optimal method of childbirth.

METHOD

This review is based on pertinent literature retrieved by a selective search in Medline and on guidelines from Germany and abroad. Recommendations about drugs were taken from the Embryotox and Reprotox databases, the German Red List, and the United States Food and Drug Administration (FDA).

RESULTS

40% to 100% of pregnant women with high blood pressure have retinal changes whose severity is correlated with the severity of pre-eclampsia or eclampsia. Diabetic women should undergo ocular examination before and during pregnancy. Pre-existing retinal changes worsen during pregnancy in 55% of cases. Most ocular diseases can be treated with the usual drugs in pregnant women and nursing mothers, although the evidence for drug safety is derived from case series and the treatment is usually provided off label. Ocular conditions that are present before pregnancy are irrelevant to the choice of a method of childbirth.

CONCLUSION

Pregnant women and nursing mothers can undergo most types of ophthalmological examination and treatment. Recommendations about drug treatment should be checked against current information that can be found on the embryotox.de and reprotox.de websites.

[Influence of mode of delivery on pre-existing eye diseases]

Many ophthalmologists and obstetricians recommend either an assisted vaginal delivery with forceps or vacuum extraction, or a Caesarean section in cases of pre-existing eye diseases, such as myopia, retinal detachment, glaucoma or diabetic retinopathy. This is mainly based on the increase of intraocular pressure during the final stage of labor. These recommendations, however, are not evidence-based. None of the published trials have reported any retinal changes after vaginal delivery. This report provides information on the influence of physiological changes on eye diseases during the final stage of delivery. In general eye disease is not an indication for an instrumental or operative delivery provided regular eye examinations (once each trimester) have been performed.

Pulsatile ocular blood flow: relationship with flow velocities in vessels supplying the retina and choroid

BACKGROUND

Although ocular tonography measures a pulsatile component of the ocular perfusion, the retinal and/or choroidal components of this pulsatile flow remain undefined.

AIM

To compare ocular tonography with the assessment of flow velocities in arteries supplying the retina, choroid and entire orbit.

METHODS

22 normal eyes from 11 subjects were studied. Pulsatile ocular blood flow (POBF) was measured using the ocular blood flow tonograph, and flow velocities in the ophthalmic, central retinal (CRA) and temporal short posterior ciliary arteries (TSPCA) using colour Doppler imaging. The correlation between POBF and retrobulbar flow velocities was determined.

RESULTS

POBF correlated significantly with peak systolic velocity (PSV) of the CRA (r = 0.56, p = 0.007) and the TSPCA (r = 0.48, p = 0.02), and with the resistive index of the TSPCA (r = 0.45, p = 0.04). Additionally, pulse amplitude (PSV-end diastolic velocity) in the CRA and the TSPCA correlated significantly with POBF measurements (each p<0.05). However, POBF did not correlate with any flow velocity indices in the ophthalmic artery.

CONCLUSION

POBF is associated with systolic and pulsatile components of blood flow velocities in both the CRA and the TSPCA. This result suggests that POBF determinations are influenced by the pulsatile components of both choroidal and retinal perfusion.

Technical note: How many readings are required for an acceptable accuracy in pulsatile ocular blood flow assessment?

PURPOSE

Pulsatile ocular blood flow (POBF) assessment aids the diagnosis of ocular diseases with defective ocular haemodynamics, such as glaucoma. Although each successful POBF measure given by the instrument represents five 'repeatable' pulses, there has been no study verifying how repeatable they are. There is also no report on the minimal number of measurements for an acceptable accuracy.

METHODS

Forty-three healthy young subjects were recruited and each subject had five consecutive POBF measurements obtained from one randomly selected eye. The coefficient of variation was calculated from the raw data of the five 'repeatable' pulses. The average from five consecutive measurements was considered as the standard for comparison with the first, average of the first two, the first three and the first four measurements. The 95% limits of agreement were determined using the Bland and Altman approach.

RESULTS

The coefficient of variation was greater than the manufacturer's claim of within 10%. The mean (+/-S.D.) POBF calculated from five consecutive measures was 732.5 +/- 243.2 microL min(-1). The mean (+/-S.D.) difference between the standard POBF and the first, average of the first two, the first three and the first four measurements was (in microL min(-1)): 12.5 +/- 59.8, 7.8 +/- 42.1, 9.6 +/- 32.5 and 3.7 +/- 19.6 respectively. The corresponding 95% limits of agreement were (in microL min(-1)): +/-117.2, +/-82.6, +/-63.8 and +/-38.4 respectively.

CONCLUSIONS

As the five 'repeatable' pulses were not as repeatable as the manufacturer claims, practitioners should not rely on one single POBF measure. An average of three consecutive measurements will be adequate to detect the minimum reported difference in POBF between glaucoma and normal patients.

Pulsatile ocular blood flow in patients with asymmetric internal carotid artery stenosis

BACKGROUND

The pulsatile ocular blood flow (POBF) of patients with asymmetric internal carotid artery (ICA) stenosis was measured bilaterally. The purpose of this study was to investigate the sensitivity of POBF assessments in screening for ICA stenosis.

METHODS

Seventeen subjects with asymmetric ICA stenosis confirmed with carotid duplex ultrasound were recruited. The diagnoses of ICA stenosis were categorised into less than 50 per cent, 50 to 69 per cent and 70 per cent or greater. Their POBF and ocular dimensions were measured after local anaesthesia. Twenty-three normal healthy subjects were recruited as the control. All of the subjects had an inter-ocular axial length difference of less than one millimetre.

RESULTS

There were 14 males and three females in the patient group with a median age of 74 years. Fourteen patients had reduced POBF to the eye ipsilateral on the side with greater ICA stenosis. The reduction in POBF ranged from 3.1 to 49.2 per cent. Two patients had reduced POBF contralateral to the side with greater ICA stenosis. One patient had similar POBF between the eyes. The control group included six males and 17 females with a median age of 65 years. The difference in their POBF between the eyes ranged from 0.3 to 13.0 per cent.

CONCLUSIONS

Stenosis of the internal carotid artery was found to reduce the POBF ipsilateral to the side with greater stenosis. The overlap in the difference in inter-ocular POBF between the patient and control groups led to a low sensitivity (calculated as 41.2 per cent) for screening ICA stenosis from an assessment of POBF. Therefore, POBF assessment is not a good diagnostic tool for screening for ICA stenosis.