Spectacle Debacle

The day was nigh approaching, coming sooner than I wished
When I would have to pay a visit to the local optometrist
No longer could I reason that it was the font size which was miniscule
I'd have to put on glasses and expose myself to ridicule 

She sat me on a chair and pressed a machine up to my eyes Then asked me to read letters which kept diminishing in size
We then moved onto dots placed in a circular formation
And she asked me to view them which I did with trepidation

First I had to view them through one lens and then the other
I had to compare their clarity, the sister from the brother
Many times, so many that I could barely even comprehend
Whose outline was less blurry, barely a second could I spend  

Finally she made her judgement on the parameters of my astigmatism
By weeks end, after paying a deposit, a new pair of glasses I'd be given
Proudly I picked them up in their brand new case with spiffy cloth
At last I could see my screen without my eyeballs falling off 
 
I put them on and peered through with an expectation of visual ease But instead it looked as if I had acquired an optical disease
Sure the letters looked slightly larger, a plus in anyone's book
But why did the screen now have such a strange trapezoidal look?