- hold spectacles horizontally at arm’s length, front of lenses pointing upwards
- remember where the door is (this bit is to a large extent dependent on your prescription strength)
- open door and quickly thrust arm out as far as you can reach – note no upward sweeping movements of arm
- have independent timekeeper count to five seconds – recommend the one thousand and one, one thousand and two etc method
- outstretched arm must be free of all interference – ensure no collateral precipitation occurs from guttering, pub sign above door etc. artificial drips play havoc with the measurements and lessen the accuracy of results. if (more…)