In order for me to explain that, I would need to give you a bit of my history.
The eye that I am speaking of is double+ that of the other eye. I am myopic. It didn’t develop like the ‘good’ eye did. I am a bit amblyopic in it (also have strabismus), so the acuity is not all there. I also have a Scleral Buckle in place (from a previous RD (Mac off) incident), which adds to the myopia there. My eyes don’t work together in the traditional sense. I have to actively encourage this eye to synchronize with the other, to keep double vision at bay. My brain relinquished some supervisory control over to me quite a long time ago, so I am able to perform micro / macro adjustments all day every day to keep things fairly in sync when it tears apart.
Since standard soft contact lenses dont go past -20, I usually have been wearing a -18.5 there (perhaps a bit less at times over the course of decades). This was just to get rid of a blob I see and allowed me to keep it tucked under the other eye’s image. I also now have metamorphopsia in it, due to the RD (Mac off) event, so the image is not really dependable nor reliable. I can’t use the eye like the other, because its a bit of a shell of an eye, hehe. It was purely to provide some backing to the overall image I primarily depend on the other eye for and perhaps some light periphery work. When all was working decent (aside from the micro / macro adjustments I have to make for synchronization with the other eye), I don’t really notice the eye’s image.
Flash forward and I eventually get a cataract in the eye (due to vitrectomy and prolonged steroid use from the RD event) that has progressed enough to remove. They implanted a power which gets closer to the other eye, uncorrected, for balance.
Now I am ready to put a contact lens in there to take it the rest of the way forward and do not have a -20 restriction (the IOL provides me half the power, out of the gate).
In my quest to provide more factual data to my brain to create a better visual illusion to me, I decided to try and boost the power more closer to what can potentially be more usable, instead of my brain performing too much estimation. I would very much like to have this eye ready to take over (a dream perhaps, hehe), in case the good eye goes awall . I would also like more depth data from two eyes rather then from one and like a quarter from the other eye, ha. I put a -10.5 in there (may change it slightly up / down after some time adjusting / observation, etc.). Final current prescription: ~-22.0. However, in doing so, this made me feel a bit of vertigo / dizziness. True, I have the illusion of more depth now, but it was making me feel a bit off here / there. This lasted for some time. I don’t really notice any ill effects of this particular sort any more.
Apologies for the wall of text. I hope this provides an explanation for that first sentence.