History
Parents of the patient may notice an inward or upward deviation of one eye relative to the other eye especially when the child is focusing at near or is tired. In younger children, they may rub their eyes, squint, and complain of headaches or diplopia. The patient may see either a single blurred image or a double image in which one image is clear and one image is blurred. Family history of strabismus or related diseases is common. The age of onset of strabismus should be noted.
Physical
Carefully examine visual acuity in a manner appropriate for the patient's age. For patients younger than 2 years of age, visual acuity is measured by subjective means. For older patients, objective methods, such as Allen or LEA pictures, HOTV matching, tumbling E, and Snellen letter chart, can be used.
Determine stereo acuity using polarized glasses and Titmus test or Randot stereogram.
Check extraocular movements to ensure that the eye movements are full. Versions and ductions may be normal or include over elevation in adduction consistent with inferior oblique overaction.
Measure or estimate the angle of deviation. The easiest method to evaluate ocular alignment is observation of the centration of the corneal light reflex in each eye, while the patient fixes on objects at distance or near (Hirschberg method) and neutralize this light reflex with prism (Krimsky method). In some cases, it is possible to perform the alternate prism cover test. The patient is first asked to fixate on an object. By alternately covering and uncovering each eye while the patient maintains fixation, the examiner can detect a shift in the eye's position with refixation and measure the objective amount of this misalignment with prism. In esotropia, as an eye is uncovered, it turns out to fixate. In true accommodative esotropia, the angle of deviation is the same when measured at distance and near fixation and usually is 20-40 prism diopters (PD).
Measure AC/A ratio. If this ratio is high, then the deviation measured at near will be significantly greater than that at distance, usually with a threshold of 10 PD used to signify a difference. In pure accommodative esotropia, the AC/A ratio should be normal; distance and near measurements should be similar.
Perform a complete eye examination. Examine the anterior segment to assess the cornea, anterior chamber, and lens. Examine the fundus with both direct and indirect ophthalmoscopes. Note the appearance of the macula and the optic nerve.
Perform cycloplegic refraction on all children by using the retinoscope and loose lenses or the phoropter to neutralize the retinoscopic light reflex. The patient usually will have hyperopia in the range of +3.00 to +10.00 diopters, with an average of +4.00 diopters in refractive accommodative esotropia and +2.25 diopters in high AC/A accommodative esotropia.
Complications
As previously mentioned, accommodative esotropia is frequently associated with amblyopia. Many children experience rapid suppression as their visual system tries to avoid diplopia and confusion. It is extremely important to catch these findings early in infants/children due to their shorter critical period and plasticity of their cells in the primary visual cortex in response to visual stimulation. Therefore, timely detection and intervention is needed to promote use of the amblyopic eye (ie with cataract removal, refractive correction, occlusion therapy) before visual defects become permanent.{ref 12}
