Atendendo a algumas respostas apreciativas e inúmeras ignorativas, aqui está......

15 maio 2009

Estigmático, ortoscópico, e aplanético

As everybody knows, a centered optical system is said to be ideal if it is estigmatic, orthoscopic, and aplanetic. Maybe not everybody knows, but folks who went to Colégio Bandeirantes in my time have heard the phrase. My eyes have never been an ideal optical system, so when the lenses got clouded because of protein degeneration there would not have been much benefit in replacing them by newfangled variable-focus lenses. I chose older and simpler spherical lenses over astigmatism-correcting torical ones out of control-theoretic robustness considerations: if the spherical lenses move, nothing changes in the vision, due to symmetry. Toric lenses must be placed in a particular orientation to correct for corneal asymmetry, and they tend not to move. However at age 45 I would like to wear the artificial lenses for as long as I have worn glasses, and prefer not to deal with the possibility of a new surgery in few decades, however remote.

The cataract surgery was succesful, although I must have flirted with the anesthesiologist's girlfriend. I don't remember ever meeting her, though I was conscious and talking to the doctor the whole time. The ruskie left me with a black eye anyway.

The choice of lens seems to have worked. The focal lens of my left eye's new optical system is roughly 80cm, with image magnification 1.25 with respect to the right eye, which was not changed. The operated eye seems to be one F-stop brighter, with colder, white-bluish tint like fluorescent light. One may say that the right eye has a yellow tint, as the right one had before surgery, but the brain compensates for these things so I had never noticed. The eye is probably still astigmatic but it's harder to tell. According to Dr Fraioli my eyesight is back to somewhat-better-than-average-when-wearing-glasses, 25/20 in American nonmetric jargon. I will still require glasses because now the optical apparatus is fixed-focus. Also, I lost the ability to observe minute details of an object by looking at it from a few centimeters away without glasses, a useful skill I shall miss.

For now the cortex can't make the images from both eyes match, because of the size difference. Walking home I saw two Indian couples, one very tall and one very short, wearing the same clothes. It will not be very easy to correct that before surgery on the right eye - contact lenses might help somewhat but I've never been fond of them. So I popped out the left lens on my old glasses, and now close one eye for reading, and the other for walking. Careful on stairs, and no driving! Instead I will listen to the complete cycle of Beethoven piano sonatas, and dream of differential geometry.
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