Show DETECTING A WEAK EYE A simple by may discover the defect yes said the doctor to a writer for the jewelers review the makers of optical instruments arc turning out some wonderful appliances nowadays for discovering imperfections of vision but ill tell you of a planter testing the respective strength of your eyes that is as simple as it is trustworthy all you need is a stereoscope and a photograph that arrangement in which the picture holder slides up and down a flat frame trombone fashion is ane best sort of stereoscope for the purpose although any will do and the photograph that will give the best results is a cabinet size view of some locality with people in it the modus operand is simplicity itself put the photograph in the holder and focus it just enough so that you can see the faces clearly then close the left eye and look at the picture intently with your right eye while you count thirty slowly now close the right eye and look at the picture with your left eye for the same length of time then open both eyes and look at the picture without changing the focus something queer will happen the figures on alie one side of the picture will seem to move across the view and group themselves with those on the other side and this is the point of the experiment the figures will always move away from the weak eye moreover flioy move with a very precise relation of speed to the weakness of vision if the left eye for example is quite weak the figures will move very quickly across the plane of sight to the right side while if there is but a slight defect the movement will be gradual and so on A queer thing about this experiment is that simple as it seems it will bring out defects of vision that have never been suspected and another queer thing is that it will demonstrate on strate the cases in which both eyes arc of equal power to be surprisingly exceptional I 1 have tried it in a score of mixed gatherings and never yet without having the experimenter obi serve some movement of the figures there was ono oil lady I 1 remember up at port jefferson last summer who persisted in saying that she saw precisely with both eyes as she did with one eye and well she might for when I 1 examined her eyes more closely 1 found she ws stone blind on the left side and dian didn t know it 7 |