AAVE is an infrequent presentation of esotropia, nonaccommodative or minorly partial accommodative esotropia with acute onset, with an accompanying diplopia or visual confusion, occurs more common in older children that previously regarded to have straight eyes. The onset age of AAVE is generally older than that of V-pattern esotropia. On account of immediate detection of esotropia, and no tendency for spontaneous resolution under our observation, the duration between onset and surgery of AAVE was short with a medium interval of 6 months, to reduce the symptoms of diplopia and preserve binocular vision.
In comparison with VE, the preoperative esodeviation of AAVE was significantly greater, perhaps because of the low proportion of accommodative factor. The mean MRc done in either eye of AAVE was 6.0 mm, giving a mean dose-response effect of 4.24 PD/ mm of medial rectus recession, which was bigger than that of VE. However, in terms of severity of IOOA and extent of V pattern, there was no statistical difference between two groups.
IOOA was reported in 34% of accommodative esotropia patients[15], it was identified as a significant factor in the deterioration of accommodative esotropia[16–18]. Oblique dysfunction is uncommon in the diagnosed population, and the mechanism of deterioration of accommodative esotropia has not well been explained. One possible explanation is that the incomitant deviation of oblique dysfunction with or without A or V pattern would cause some intermittent suppression, which increases the instability of control of the alignment in primary position, eventually the gradual contracture of medial rectus muscles would lead to the deterioration of accommodative esotropia[17]. We conjecture that AAVE patients may have had latent vertical deviation or related anatomical bases. Contracture of medial rectus muscles muscle related to the instability of control caused by IOOA with V pattern appears to be the possible explanation for the acute onset of AAVE.
Highly favorable surgical outcomes were achieved in AAVE group, accompanied by alleviation of diplopia if present preoperatively. Overall surgical success rate was 73.3%. The stereoacuity was obviously improved postoperatively at their last follow-up visit, of which 8 (66.7%) patients recovered to “good stereoacuity” status, demonstrating good binocular potential in spite of disruption before surgery. One patient underwent reoperation because of larger angle of consecutive exotropia. We reviewed the records in great detail, finding that she was the youngest child of the group, suffered from esotropia for 6 months, and was combined with amblyopia.
It is not clear whether AAVE is a subtype of AACE. They do have similarities in some aspects. Such as the sudden onset of esotropia with diplopia, and occurring in older children. Burian and Miller[5] subclassified AACE into three subtypes, of which type III (Bielschowsky type) occurs in those with mild to moderate myopia, due to intensive near viewing, especially the excessive use of tablet or smartphone[19–21]. Some cases of AACE were associated with neurological disorders[10, 22–24].
Let us return to the case reported by Tracey[4], the esotropia and inferior oblique dysfunction resolved spontaneously after tumor excision. In our study, only one patient had a history of febrile convulsion and generalized seizures, with bilateral occipital local malacia, cerebral atrophy and peripheral gliosis radiographically. After resolution of the neurological symptoms, her esotropia and bilateral IOOA did not resolve. None of others had any neurological signs or symptoms at the time of presentation or any time until their last follow-up visit. IOOA with A or V pattern in acute esotropia has been proposed for the potential presence of neurological disease[10, 11]. However, overaction of the inferior oblique in patients with intracranial tumors was not a significant risk factor in another study[8]. But comprehensive neurological and neuroradiological examinations are still indispensable in the presence of neurological indications (e.g., headache, weakness, clumsiness, papilledema, cerebellar imbalance, poor motor coordination) or accompanying nystagmus[24, 25].
Spontaneous recovery of AACE is unusual, and the botulinum toxin type A (BTXA) injection is an alternative choice; however, it is not as effective as conventional extraocular muscle surgery[26, 27], calculating an accurate BTXA dose is challenging due to individual response, and is associated with a higher recurrence rate at follow-up[28, 29]. In view of the uncertainty of BTXA treatment and the presence of inferior oblique dysfunction, surgical intervention was our primary option for AAVE when conservative treatment or observation was ineffective.
We acknowledge the limitations of the retrospective design of this study. The number of cases in our study was small. In addition, stereoacuity was not recorded consistently in all patients both preoperatively and postoperatively. Also, we did not conduct a case-control study between AAVE and AACE, although some similarities were found, specific differences between them were not known.