Which term refers to a refractive error in which images do not focus properly on the retina?

The term that refers to a refractive error in which images do not focus properly on the retina is ametropia. Ametropia encompasses various types of refractive errors, such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, all of which result from the eye not properly bending light to focus images correctly on the retina. This improper focusing can lead to blurred vision, making it a central concept in the understanding of vision and ocular health.

In contrast, aphakia denotes the absence of the lens in the eye, leading to a specific type of visual impairment. Anisometropia refers to a condition where the two eyes have significantly different refractive power, which can cause issues with binocular vision. Aniseikonia describes a condition where there is a significant difference in the perceived size of images in each eye, impacting depth perception and visual comfort. These terms describe specific conditions and variations within refractive errors but do not capture the broader category of improper image focus that ametropia represents.