Infantile esotropia is an ocular condition of early onset in which one or either eye turns inward. It is a specific sub-type of esotropia and has been a subject of much debate amongst ophthalmologists with regard to its naming, diagnostic features, and treatment. Presentation
Historically the term congenital strabismus was used to describe constant esotropias with onset between birth and six months of age. However, this term was felt to be an inadequate classification as it covered a variety of esotropias with different causes, features and prognoses. In 1988, American ophthalmologist Gunter K. Von Noorden discussed what he described as Essential Infantile Esotropia. He described the condition as: 
"early acquired, not... congenital ..., although congenital factors may favor its development between the ages of 3 and 6 months"

 and identified this squint sub-type as having the following features:
Onset between birth and six months of age. Large size (greater than 30 dioptres)
Stable size
Not associated with abnormalities of the central nervous system. Often associated with defective abduction (outward movement) and excessive adduction (inward movement) of the eyes. Also associated with oblique muscle dysfunction and Dissociated Vertical Deviation. Initial alternation of the squint present with crossed fixation, i.e. the affected individual uses the left eye to look right and the right eye to look left.
Limited potential for binocular vision.The same condition had also previously been described by other ophthalmologists, notably Cianca (1962) who named it Ciancas Syndrome and noted the presence of manifest latent nystagmus, and Lang (1968) who called it Congenital Esotropia Syndrome and noted the presence of abnormal head postures. In both cases, however, the essential characteristics were the same, but with emphasis placed on different elements of the condition. Helveston  (1993) further clarified and expanded upon von Noordens work, and incorporated the work of both Lang and Cianca into his summary of the characteristics of the condition:

Esotropia between 10 and 90 dioptres in size
Either alternation or fixation preference may be present (if the latter then amblyopia may result). Neurologically normal. Hyperopic correction does not eliminate or significantly reduce the squint size. Frequent nystagmus (latent or manifest latent). The patient may or may not have any or all of the following associated conditions: Oblique muscle dysfunction, vertical incomitance, dissociated vertical deviation, asymmetric optokinetic nystagmus, torticollis. Presence will be confirmed by six months. Best treatment results in subnormal binocular vision.The expressions congenital esotropia, infantile esoptropia, idiopathic infantile esotropia and essential infantile esotropia are often used interchangeably. Cross-fixation
Cross-fixation congenital esotropia, also called Ciancis syndrome is a particular type of large-angle infantile esotropia associated with tight medius rectus muscles. With the tight muscles, which hinder adduction, there is a constant inward eye turn. The patient cross-fixates, that is, to fixate objects on the left, the patient looks across the nose with the right eye, and vice versa.