How long have you had this strain symptom? How does it manifest? Always, sometimes, close-up, distance, lighting, etc?
A ratio less than 20% according to the centimeters should be entirely fine. Ocular dominance range, close enough, not a big deal.
The optometrist may have just dialed up the diopters to the maximum which tends to emphasize 1) normal ocular dominance and 2) any extra uneven focal plane that is still present. If you’re at half diopter but could be in between there and 0.75, them giving you a full diopter isn’t that surprising. It’s the business model!