Someone with esotropia will squint with either the right or the left eye but never with both eyes simultaneously. In a "left esotropia", the left eye 'squints,' and in a "right esotropia" the right eye 'squints.' In an "alternating esotropia", the patient is able to alternate fixation between their right and left eye so that at one moment the right eye fixates and the left eye turns inward, and at the next the left eye fixates and the right turns inward. This alteration between the left and right eye is mostly spontaneous, but may be voluntary in some cases. Where a patient tends to consistently fixate with one eye and squint with the other, the eye that squints is likely to develop some amblyopia. Someone whose squint alternates is very unlikely to develop amblyopia because both eyes will receive equal visual stimulation. It is possible to encourage alternation through the use of occlusion or patching of the 'dominant' or 'fixating' eye to promote the use of the other. Esotropia is a highly prevalent congenital condition.