Is it better to eliminate spherical diopters when it is too less when compared to cylindrical diopters

There is a huge difference in right and left eye for my son.
SPH- -0.50
CYL- -3.50
AXIS- 20

SPH- -2.25
CYL- -1.50
AXIS- 140

**I planned of reducing 1 diopter from his current prescription. I got this doubt of whether i can take spherical power to 0 (in his right eye) as it is just -0.5.
But, according to the sessions, we need to add 0.5 diopters to spherical if we reduce a complete 1 diopter in cylinder. So in that case, in his right eye, i need to add 0.5 diopters for reducing 1 diopter in cylindrical. But this would also not bring him a change or challenge in clearing the blur. **

Will it be right do so to take spherical to 0 ?
Please suggest.

Thanks :slightly_smiling_face:

I’d try just reducing by a quarter, as usual. Then another quarter, and you’re completely ready to work with cylinder.

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How old is he?
Has he worn this correction already? What acuity does this give him on a Snellen?

Is there anything around his study desk or phone habits that justify such a big difference between the eyes and within the eyes?
How long has he had the cyl and were all measurements always at the same axis?

Have you considered trading in some cyl for sph at least in the right eye to reduce complexity?

Are you planning a reduction for differentials or normalised?


If it’s his first reduction only reduce spherical not cylinders by 0.25.

You don’t know how his visual cortex is going to respond and making too many corrections eg. both spherical and cylinder at the same time for the first correction is going to give him too many focal plane changes that could adversely impact his vision eg. headaches, dizziness etc or in some cases his depth perception.

Have you been measuring his cms or doing a Snellan measurement first before making changes?


Thanks for your support
Planning for differentials.
He is just 15 years old.
The measurements are consistent (20/20 with glasses and 20/30 without them), same at axis and he is having glasses from 4 years, Only his cylinder seems to rise but spherical hasn’t gone up for the past 2 years.
So only i got this confusion of whether to reduce that 0.5 or not, but now i am clear, will go with a 0.25 reduction only, just to not cause strain.


With this complicated Rx a test lens kit might be in order.

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