- The same eye cannot have myopia and hyperopia at the same time, but it can have either one coupled with astigmatism.
There are many doubts regarding the compatibility of the different refractive errors because only some of them can occur simultaneously in the same eye.
On the one hand, myopia occurs when the eye is too long, when the cornea is more curved than normal or when crystalline lens has too much dioptric power. These changes cause distant objects to be focused in front of the retina instead of on the retina. This makes distant objects looks blurry but close-up objects look clear.
Hyperopia, on the other hand, also produces an inability to correctly focus images on the retina. However, unlike myopic people, hyperopic people have blurred vision up close, since the eye is shorter and focuses nearby objects behind the retina.
In this way, you cannot have myopia and hyperopia in the same eye, since they are opposite refractive defects. It would be possible for the same patient to develop hyperopia in one eye and myopia in another, although this is very rare and happens scarcely ever.
However, astigmatism can be associated with both myopia and hyperopia, since this refractive error consists of vertical and horizontal light rays having different points of focus on the retina. The vision for both near and far objects is blurry or distorted as light rays aren’t refracted properly and images focus in front of and beyond the retina. Objects may appear extended or wider, sometimes letters and numbers are confused, and even sometimes shadows can appear next to objects.
Dr. José Lamarca, ophthalmologist in the areas of Cornea and ocular surface, Refractive Surgery and Cataracts at the Barraquer Ophthalmology Centre.