Question about new sphere values

April 2023 eye exam results:

Right Eye --- Sphere: +1.25 / Cylinder: -2.75 / Axis: 20

Left Eye --- Sphere: +0.50 / Cylinder: -1.50 / Axis: 180

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December 2023 eye exam results:

Right Eye --- Sphere: PL / Cylinder: -2.50 / Axis: 24

Left Eye --- Sphere: PL / Cylinder: -1.50 / Axis: 171

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Sphere values have dropped considerably to Plano. I suspect this may have something to do with the fact that I misplaced my glasses with April's prescription over a month before December's exam, and therefore adjusted without them. I mentioned this to my doctor and he chalked it up to "natural variations". I'm concerned the sphere values from December's exam are not accurate, owing to my eyes having adjusted considerably. Any advice appreciated.