Results of my Saturday test, from the CostCo Santa Cruz Optomotrist:
Eyeglass Prescription
O.D. (Oculus Dexter, my right eye):
- SPH: plano (no refractive error)
- CYL: -1.00
- AXIS: 070
- PRISM/BASE: n/a
- ADD: n/a
O.S. (Oculus Sinister, my left eye):
- SPH: -1.00
- CYL: -0.75
- AXIS: 089
- PRISM/BASE: n/a
- ADD: n/a
RESULTS, TRENDS OVER EIGHT YEARS
First eye exam, in about five years--well overdue...surprised how fast time has gone by.
Overall, my new optometrist did not seem concerned. After obtaining my current prescription (by measuring my current eyeglasses), she noted my left eye had a small astigmatism increase, but remains low.
Nearsightedness seems flat, to me, since 2011. Each eye has changed astigmatism direction, by ten degrees, in opposite directions.
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| Refractive Power - Nearsightedness (Myopia), 2008-2016 |
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| Astigmatism - Amount, 2008-2016 |
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| Astigmatism - Direction, 2008-2016 |
BACKGROUND
All measurements represented in units of
dioptres, a unit that represents focusing power. More dioptres mean more focusing power--so if the numbers get big, that means you need a "stronger" prescription to see clearly.
SPH means sphere--a positive number represents farsightedness and a negative number represents nearsightedness. Why? In a farsighted eye, the curve of the cornea is flatter than the curve of a normal cornea, so the correction involves "adding" to the farsighted eye to get it back to normal. In a nearsighted eye, the curve of the cornea extends farther than the curve of the normal cornea, so the correction involves "subtracting" from that curve to bring it back to a normal curvature. The point being to get the cornea back to focusing light on the retina like a normally curved cornea does. The larger the number (positive or negative) the larger the deviation from the normal curvature of the cornea, and the blurrier the vision.
CYL means cylinder, and represents the amount of power needed to correct a cornea with astigmatism (a cornea that's oval-shaped, which causes blurring (see the picture at the top), as opposed to a normal cornea that's symmetrically round like a basketball)--DS means no astigmatism.
AXIS, for astigmatic eyes, represents a line passing through the middle of the oval-shaped cornea--in my case through the longer side. In my right eye, I need minus-one dioptre of correction along the axis specified (see the
Wikipedia article for an explanation of why it's not "078" like the prescription says). I believe reducing the focusing power of the longer part of the oval-shaped cornea helps the cornea focus in a more spherical manner.
20/20 vision means the ability to read a character 8.84 mm high at a distance of 20 feet.
Lanna's suggestions on glasses frame colors: navy, light blue, plum.
Pupillary Distance:
I don't think this changes, over time: In 2011, CostCo staff measured my PD for me: 32.5 for each eye, for a total of 65.
Previously:
