Abstract
Purpose::
Retinal vein pulsation is absent in 46% glaucoma patients, and present in 98% of age matched controls. When absent it can be induced by applying a graded ophthalmodynamometric force (ODF) to the eye. The magnitude of this force is associated with greater glaucomatous field loss. We wished to measure the predictive value of ODF and IOP in determining glaucoma progression. In this study we used increasing optic disk excavation as our index of glaucoma progression.
Methods::
136 eyes of 75 glaucoma and suspects had IOP, visual fields, stereo optic disc photography and ODF measured. Where venous pulsation was spontaneous, the ODF was said to be 0g. At re-examination at mean 83 months later the same tests as well as central corneal thickness and blood pressure measurements were performed. Initial and subsequent optic disk photographs were compared and graded into those which had excavated and those that had remained stable. All IOP measurements between the 2 photographic sessions were used to calculate the time averaged IOP and IOP standard deviation. Stereo-flicker chronoscopy was used to determine whether increased excavation had occurred. The relationship between increased disk excavation and the measured variables was modeled using a multiple mixed effects logistic regression.
Results::
Mean age was 68.0 years (± 12·2) at the final visit. 36 were female (mean age 68·7 ± 11·0) and 39 were male (mean age 67·3 ± 13·3). Mean time averaged IOP was 17.6mmHg (± 3.5, range 9 - 26mmHg) ODF at the initial visit was strongly predictive of increased excavation (p = 0.0000, odds ratio 1.18/g, range 0 to 60g) as was the change in ODF (p = 0.0001, odds ratio 1.09/g). Central corneal thickness was also found to be predictive of change (p=0.043, odds ratio 0.97/micron) as well as disk rim haemorrhage (p=0.0000). Mean IOP, IOP standard deviation, visual field mean deviation and blood pressure were not independently predictive of excavation.
Conclusions::
Initial ODF measurement is strongly predictive of patient's risk for further optic disk excavation in this set of glaucoma suspects and tightly controlled glaucoma patients. Additionally, the change in ODF is independently associated with increased disk excavation. Measurement of venous pulsation characteristics may be useful in clinical practice.
Keywords: optic disc • blood supply • intraocular pressure