I had a call from a gentleman the other day who has a very high spectacle correction for astigmatism. In his left eye he requires a power of -3.00/ -12.00 x 45. Now that is VERY high astigmatism. A lens of that power being displaced off axis by only one degree will cause intolerable blurriness to the wearer. So this poor gentleman had had glasses made at an optometry practice near his home in Melbourne, however upon taking delivery of the glasses he realised that he could see much better if he lifted up the left temple so that it sat 25mm above his ear. He went back to the practice that made them, however even after a couple of attempts at having the glasses re-made they were never correct and he always had to do the same thing to see clearly. Eventually he made a prop from a piece of cardboard which he stuck under the tip of the left temple so that the glasses sat at a permanent angle allowing him clear vision. The optometry practice in question (also frustrated no doubt at the laboratory’s inability to manufacture the lens with sufficient accuracy) basically put up their hands and told the gentleman that that is the best that can be done. Now the original prescription called for the lens to be made with an axis of 45 degrees, however it had been made to 40 degrees, which clearly indicated to me that the lens had swung off axis during the edgeing (shaping) process.
After finding us on the internet and some phone discussion, the gentleman travelled the one hour to come and visit us in Rosebud. One of the problems with the job was that the frame was oblong in shape with very square corners, which allows for absolutley no axis alteration once the lens has been cut and mounted in the frame! My suggestion to him was to choose a round or near round frame so that when we mounted the lenses we had some”wriggle room” to swing them around to the appropriate axis. Also, a small frame would cut down on the lens thickness considerably giving a better aesthetic result.
So I started the process by checking the axis at which he was wearing his lenses with the cardboard prop. I found this to be 50 degrees. So I marked up the new (uncut) lenses at 50 degrees and had him hold the lens and check the vision. Sure enough, 50 degrees gave the clearest vision, so I proceeded to make the lenses to his newly chosen round eye frame to an axis of 50 degrees.
Normally this would be easy, but this lens has a -12.00 cylinder, so what I found was that the blocking machine which attaches the block to the lens at the right angle kept skewing it off axis by 10 degress or so. After a number of attempts I managed to get the block on perfectly on axis. I cut the job very gently so as to avoid any axis swing which proved successful and the job ended up absolutely perfect.
Next was to try it on the patient and check his vision. Bingo! Perfect vision with glassses sitting straight on his head. I now have a very happy customer and I feel great having given this man’s vision back without the funny looking tilted glasses. A great result all round!
Posted by Murray O'Brien on January 30, 2013