NEW TABLET HALOMETER

A new tablet-based device, the Aston Halometer, provides a sensitive, repeatable and objective quantification of disabling glare, according to James S Wolffsohn OD, PhD, of Aston University, Birmingham, UK. 
The new halometer is designed to measure aspects of dysphotopsia commonly encountered with multifocal intraocular lenses, Prof Wolffsohn told the XXXIII Congress of the ESCRS in Barcelona, Spain. 
“Some people are more prone to report dysphotopsia than others. And we need to be able to support people when we feel that they have these symptoms,” he commented.
The Aston Halometer consists of a bright light-emitting-diode (LED) glare source in the centre of a modern iPad tablet computer (Apple) placed at 2.0m from the patient. 
When undergoing halometry with the device, patients identify letters subtending 0.21° on the iPad screen as they move centrifugally from the LED in 0.05° steps, in orientation separated by 45° for each change in the level of contrast. An iPhone is used to control the eccentricity and the randomisation of the letters. 
“This halometer is very simple. You can detect light scatter and it also has what we call face validity. Patients are used to describing glare for example around car headlights so this test minics this effect,” Prof Wolffsohn said.
He noted that in a validation study involving 20 patients with a mean age of 27.7 years, halo size as measured with the Aston Halometer increased with the different target contrasts (F=29.564, p<0.001) ranging from 1,000 to 25 Weber contrast units (Cw), as expected, and in a similar pattern to stray light measures (F=80.655, p<0.001). 

BEST COMPROMISE
He added that lower contrast letters showed better sensitivity to glare effects, but larger glare-obscured areas resulted in ceiling effects due to the screen’s field-of-view, with 500 Weber contrast units being the best compromise. 
Intra-observer and inter-observer repeatability of the Aston Halometer was good, at 0.84-0.93 and 0.53-0.73, respectively, at 500Cw, and were similar to the stray light measurements with the CQuant (OCULUS). Moreover, unlike the CQuant, the new halometer differentiates between the glare effects of monofocal, concentric diffractive multifocals and segmented multifocal lenses.
The findings of the Aston team were published in the November 2015 issue of the Journal of Cataract & Refractive Surgery. Prof Wolffsohn added that he and his associates are in the process of commercialising their new device.
“The Aston Halometer provides a sensitive, repeatable way of objectively quantifying subjectively reported glare discomfort,” Prof Wolffsohn added. 

James S Wolffsohn: j.s.w.wolffsohn@aston.ac.uk