Ophthalmodynamometry and corticosteroids in central retinal vein occlusion

Intraocular Pressure Reduction Is Associated with Reduced Venous Pulsation Pressure

Purpose

To explore whether alterations in intraocular pressure (IOP) affect vein pulsation properties using ophthalmodynamometric measures of vein pulsation pressure.

Patients and Methods

Glaucoma patients had two retinal vein pulsation pressure (VPP) measurements from upper and lower hemiveins performed by ophthalmodynamometry at least 3 months apart. All subjects had VPP and IOP recorded at two visits, with standard automated perimetry, central corneal thickness (CCT) recorded at the initial visit. Where venous pulsation was spontaneous ophthalmodynamometry could not be performed and VPP was considered equal to IOP. Change in VPP was calculated and binarized with reduction in pressure scored 1 and no change or increase scored as 0. Data analysis used a mixed logistic regression model with change in VPP as response variable and change in IOP, visual field loss (mean deviation), CCT and time interval as explanatory variables.

Results

31 subjects (20 females) with mean age 60 years (sd 11) were examined with change in VPP being significantly associated with change in IOP (odds ratio 1.6/mmHg, 95% CI 1.2 to 2.1 in the glaucoma patients but not suspect patients (p = 0.0005).

Conclusion

Change in VPP is strongly associated with change in IOP such that a reduced intraocular pressure is associated with a subsequent reduction in VPP. This indicates that reduced IOP alters some retinal vein properties however the nature and time course of these changes is not known.

Objective detection of retinal vessel pulsation

Purpose

Retinal venous pulsation detection is a subjective sign, which varies in elevated intracranial pressure, venous obstruction and glaucoma. To date no method can objectively measure and identify pulsating regions.

Method

Using high resolution video-recordings of the optic disk and retina we measured fluctuating light absorption by haemoglobin during pulsation. Pulsation amplitude was calculated from all regions of the retinal image video-frames in a raster pattern. Segmented retinal images were formed by objectively selecting regions with amplitudes above a range of threshold values. These were compared to two observers manually drawing an outline of the pulsating areas while viewing video-clips in order to generate receiver operator characteristics.

Results

216,515 image segments were analysed from 26 eyes in 18 research participants. Using data from each eye, the median area under the receiver operator curve (AU-ROC) was 0.95. With all data analysed together the AU-ROC was 0.89. We defined the ideal threshold amplitude for detection of any pulsating segment being that with maximal sensitivity and specificity. This was 5 units (95% confidence interval 4.3 to 6.0) compared to 12 units before any regions were missed. A multivariate model demonstrated that ideal threshold amplitude increased with increased variation in video-sequence illumination (p = 0.0119), but between the two observers (p = 0.0919) or other variables.

Conclusion

This technique demonstrates accurate identification of retinal vessel pulsating regions with no areas identified manually being missed with the objective technique. The amplitude values are derived objectively and may be a significant advance upon subjective ophthalmodynamometric threshold techniques.

Heart-beat-phase-coherent Doppler optical coherence tomography for measuring pulsatile ocular blood flow

We introduce a Doppler OCT (DOCT) platform that is fully synchronized with the heart-beat via a pulse oximeter. The system allows reconstructing heart-beat-phase-coherent quantitative DOCT volumes. The method is to acquire a series of DOCT volumes and to record the pulse in parallel. The heartbeat data is used for triggering the start of each DOCT volume acquisition. The recorded volume series is registered to the level of capillaries using a cross-volume registration. The information of the pulse phase is used to rearrange the tomograms in time, to obtain a series of phase coherent DOCT volumes over a pulse. We present Doppler angle independent quantitative evaluation of the absolute pulsatile blood flow within individual retinal vessels as well as of the total retinal blood flow over a full heartbeat cycle.

Value of retinal vein pulsation characteristics in predicting increased optic disc excavation

BACKGROUND

Retinal vein pulsation is often absent in glaucoma, but can be induced by applying a graded ophthalmodynamometric force (ODF) to the eye, which is elevated in glaucoma.

AIM

To assess whether ODF has a predictive value in determining glaucoma progression.

METHODS

75 patients with glaucoma and suspected glaucoma were examined prospectively in 1996, and then re-examined at a mean of 82 months later. All subjects had intraocular pressure, visual fields, stereo optic disc photography and ODF measured on their initial visit. When venous pulsation was spontaneous, the ODF was said to be 0 g. At re-examination, central corneal thickness and blood pressure were also measured. Initial and subsequent optic disc photographs were compared and graded into those that had increased excavation and those that had remained stable. The relationship between increased excavation (recorded as a binary response) and the measured variables was modelled using a multiple mixed effects logistic regression.

RESULTS

ODF at the initial visit was strongly predictive of increased excavation (p = 0.004, odds ratio 1.16/g, range 0-60 g), with greater predictive value in women than in men (p = 0.004). Visual field mean deviation was predictive of increased excavation (p = 0.044), as was optic nerve haemorrhage in association with older age (p = 0.038). Central corneal thickness was not significantly predictive of increased excavation (p = 0.074) after having adjusted for other variables.

CONCLUSION

ODF measurement seems to be strongly predictive of the patient's risk for increased optic disc excavation. This suggests that ODF measurement may have predictive value in assessing the likelihood of glaucoma progression.

Retinal venous pulsation in glaucoma and glaucoma suspects

PURPOSE

To determine whether changes in central retinal vein pulsation characteristics occur in glaucoma, and how these are related to indices of glaucoma severity.

DESIGN

A large, consecutive, prospective, case-controlled study.

PARTICIPANTS

Ninety-four consecutive glaucoma patients and 105 glaucoma suspects seen in a tertiary referral clinic were examined. Forty-one age-matched normal subjects also were examined.

METHODS

The presence or absence of spontaneous venous pulsation was observed in these 3 groups. The ophthalmodynamometric force (ODF) required to induce venous pulsation at the optic disc was measured in those without spontaneous pulsation. Optic disc photographs were obtained and visual field testing was performed for all subjects.

MAIN OUTCOME MEASURES

The prevalence of spontaneous venous pulsation between these 3 groups was compared. The relationship between ODF and visual field mean deviation, neuroretinal rim area, age, intraocular pressure (IOP), gender, and diagnosis of glaucoma was investigated using linear mixed models fitted by Gibb's sampling.

RESULTS

Significantly fewer (chi-square, 27.7; P<0.001) glaucoma patients (54%) were observed to have spontaneous venous pulsation than suspects (75%) or normals (98%). A worse visual field mean deviation was shown to be the most significant predictor of a higher ODF (P<0.000), with younger age (P<0.000) also predictive of a higher ODF. A strong relationship between ODF and mean deviation was found in the glaucoma patients (r = 0.59; n = 52; P<0.001).

CONCLUSIONS

Spontaneous venous pulsation is less common in glaucoma. The ODF required to induce venous pulsation is increased in glaucoma, and this ODF is greater in those with more severe field loss.

Internal limiting membrane peeling for decompression of macular edema in retinal vein occlusion: a report of 14 cases

BACKGROUND

Currently, there is no proven treatment for macular edema due to central retinal vein occlusion (CRVO). Moreover, not all cases with macular edema due to branch retinal vein occlusion (BRVO) respond to laser photocoagulation. We postulated that internal limiting membrane (ILM) peeling for decompression of macular edema in cases of retinal vein occlusion would facilitate egress of blood and extracellular fluid out of the inner retinal layers, leading to reduction of macular edema and improvement in visual acuity.

METHODS

Fourteen consecutive patients with macular edema due to CRVO or selected cases of BRVO, not eligible for laser photocoagulation, underwent pars plana vitrectomy with removal of preretinal hyaloid and peeling of the ILM stained with indocyanine green dye.

RESULTS

In all cases, intraretinal blood and retinal thickening diminished within 6 weeks of surgery. Visual acuity improved in 78.6% of cases. No surgical complications occurred, although one patient developed nuclear cataract 10 months postoperatively.

CONCLUSION

Pars plana vitrectomy with ILM peeling in selected cases of CRVO and BRVO showed improvement in visual acuity in this nonrandomized, noncontrolled study. This pilot study adds support to the concept that ILM peeling may of visual benefit when compared with the natural history in these vaso-occlusive diseases.