Final answer:
All degrees of hypermetropia can affect the vision of aphakic dogs, with more significant vision challenges arising from moderate and high hypermetropia. This is due to the inability of the hyperopic eye to properly converge rays from close objects on the retina, causing blurry near vision.
Step-by-step explanation:
In aphakic dogs (dogs without a lens in their eye), all degrees of hypermetropia, aka hyperopia or farsightedness, can potentially affect their vision to varying degrees.
Low hypermetropia may cause minimal to no vision impairment, while moderate and high hypermetropia might cause significant challenges, particularly with near vision. This is because the hyperopic eye is unable to converge the rays from a close object by the time they strike the retina, producing blurry close vision.
This can be caused by insufficient power in the lens, which in aphakic dogs is non-existent, or by the eye being too short. No hypermetropia, indicating no farsightedness, in normal circumstances would not cause any visual issue to the dog. However, in aphakic dogs, even without the condition of hypermetropia, vision can still be impaired as they lack the eye's natural lens.
Learn more about Aphakic Dogs and Hypermetropia