What does this mean and what difference is considered significant?
The optical power of the eye is measured in diopters and consists of the refractive power of the cornea, lens and the length of the eyeball. If these parameters differ in two eyes, the refraction also differs. A difference of approximately one diopter is usually not felt. When the discrepancy reaches one and a half to two diopters or more, the visual system begins to experience difficulties: images differ not only in clarity, but also in size, and combining them into one three-dimensional image becomes difficult.
- Simple - one eye with normal vision, the other with impaired vision
- Complex - both eyes with the same type of disorder, but of different strength
- Mixed - myopia in one eye, farsightedness in the other
- Axial - due to different lengths of the eyeballs
- Refractive - due to different strengths of the cornea or lens
Reasons
Most often, anisometropia is congenital: the eyes grow at different rates, and by school age the difference becomes obvious. A separate group of causes are conditions that prevent one eye from developing normally: congenital cataracts, drooping upper eyelid, orbital hemangioma. Acquired anisometropia occurs after injury, eye surgery, keratoconus, or removal of the lens in only one eye. Often combined with a hereditary predisposition to myopia.
- Uneven growth of eyeballs
- Hereditary predisposition
- Congenital cataracts and corneal opacities
- Ptosis of the upper eyelid, covering the pupil
- Keratoconus, trauma, eye surgery
- Prematurity and retinopathy of prematurity
Symptoms and dangers
An adult usually complains of rapid eye fatigue, headaches in the forehead and temples, difficulties reading and working at the computer, as well as impaired depth perception: it is difficult to judge distances, pour tea, or park a car. The child does not complain at all, because the healthy eye fully copes with the task. The brain stops using the signal from the weak eye, and it gradually loses the ability to see even with glasses. This is amblyopia.
- Eye fatigue and headache
- Impaired judgment of distances and three-dimensional vision
- Squinting, tilting or turning the head
- Double vision and discomfort with prolonged visual strain
- In children - amblyopia and strabismus
- Imperceptible loss of vision in one eye for the child
What examinations are needed
The examination begins with checking visual acuity separately for each eye - with and without correction. Autorefractometry quickly shows the objective refraction of each eye. In children, it must be performed under conditions of medicinal dilation of the pupil, otherwise the strain of accommodation distorts the result. The doctor also examines the fundus and anterior segment of the eye to find the cause: cataracts, corneal opacities, retinal changes. The position of the eyes and the nature of binocular vision are assessed.
- Checking visual acuity of each eye separately
- Autorefractometry, in children - with pupil dilation
- Examination of the fundus and anterior segment
- Assessment of binocular vision and eye position
- Measuring eye length if necessary
- Selection of trial correction with assessment of tolerability
Correction and treatment
The main way is to choose the right optics. The glasses are simple and affordable, but when the difference is large, they create images of different sizes that are difficult to align and may not be tolerated well by a person. In such cases, contact lenses come to the rescue: they are placed directly on the cornea and almost do not change the size of the image. In children, along with correction, amblyopia is treated: the best eye is temporarily closed to make the weak one work, and hardware exercises are added. For adults with stable refraction, laser correction may be suitable - the decision is made by the ophthalmologist after an examination.
- Wearing properly fitted glasses at all times
- Contact lenses with large diopter differences
- Occlusion of a healthy eye in children according to a doctor’s scheme
- Hardware treatment of amblyopia
- Elimination of the cause: surgery for cataracts, ptosis
- Preventive examinations of the child at 1, 3 and 6 years old and annually thereafter