Aqueous outflow is crucial to ocular health, and a prime target of glaucoma therapy. However, visualizing this process can be challenging, despite today’s advanced diagnostic tools. Most in vivo techniques are static, invasive or involve some manipulation of physiological parameters. An international team of researchers from the UK and Australia has developed a non-invasive technology that might help: hemoglobin video imaging (HVI).

To test the technology, they added HVI to a typical clinical visit for patients at the Addenbrookes Hospital Glaucoma clinic. They viewed 30 eyes for a prospective observational study to characterize aqueous veins, and eight eyes slated for selective laser trabeculoplasty (SLT) for a pilot prospective interventional feasibility study. The team assessed the change in cross sectional area of the aqueous column within the episcleral veins and compared that with both intraocular pressure (IOP) reduction and change in visual field mean deviation before and after intervention.

HVI provided the researchers direct visualization of the aqueous flow. They noted the flow is “pulsatile” and fluctuates based on globe pressure and compression of the aqueous vein.

After SLT, HVI revealed an increase in the aqueous column, which correlates with a decrease in IOP and an improvement in the visual field mean deviation.

The researchers conclude the new technology could be added to a routine examination, allowing clinicians the ability to assess and quantify aqueous outflow in real time. “It has the potential to be used to help target therapeutic interventions to improve aqueous outflow and further advance our understanding of aqueous outflow dysregulation in the pathogenesis of glaucoma,” they concluded in their paper on the work.

Khatib TZ, Meyer PAR, Lusthaus J, et al. Haemoglobin video imaging provides novel in vivo high-resolution imaging and quantification of human aqueous outflow in glaucoma patients. Ophthalmology Glaucoma. April 5, 2019. [Epub ahead of print].