[Intermittent exotropia]

The efficacy of part-time patching treatment for intermittent exotropia on different age groups

BACKGROUND

Intermittent exotropia (IXT) is one of the most common forms of strabismus usually seen in the pediatric age group, the prevalence of IXT is higher in Africa and the Middle East. IXT treatment strategies include both surgical and non-surgical methods, non-surgical management is preferred in general as it is less invasive and avoids the risks associated with surgery and anesthesia.

AIMS

This study aims to determine the effectiveness of patching therapy for the treatment of IXT in different age groups and to compare the success of patching therapy in preventing surgery in IXT patients in different age groups.

METHODOLOGY

A retrospective chart review was conducted from September 2022 until February 2023 at King Abdulaziz University Hospital in Riyadh. The data was collected retrospectively from electronic medical records from 2016 to 2021 of all patients diagnosed with IXT and were managed by patching therapy fitting the inclusion criteria.

RESULTS

A total of 76 patients with IXT enrolled in the study with 56.5% of the participants were older than 7 years old. Overall, there was no improvement in the angle of deviation but 34% of patients had improved control over the follow-up period. 55.3% of the participants didn't require surgery. Younger age, longer duration of patching per month, and good compliance were significantly associated with treatment success.

CONCLUSION

Younger age groups were more likely to benefit from patching therapy than older age groups, and good compliance to patching therapy is an important factor in preventing the need for surgery.

Surgical outcomes of bilateral lateral rectus recession versus unilateral recession and resection for the divergence excess type of intermittent exotropia

Purpose

To compare bilateral lateral rectus recession (BLR) with unilateral recession and resection (RR) for divergence excess intermittent exotropia (IXT).

Methods

Retrospective analysis of 66 patients with divergence excess IXT who underwent either BLR or RR from January 2013 to December 2020 was conducted. Data on demographics, pre- and postoperative deviations, fusion, stereopsis, control, and accommodative convergence/accommodation ratio were collected. Success was defined as esodeviation ≤5 PD (prism diopter) to exodeviation ≤10 PD with a follow-up time of at least 8.0 ± 2.0 weeks.

Results

BLR (42 cases) and RR (24 cases) groups had the same success rate (83.3%, P = 0.688) and similar reduced postoperative deviations both in distance and at near (P > 0.05). Near-distance disparity decreased significantly in both groups (P = 0.000) with no intergroup difference (P = 0.193).

Conclusion

BLR and RR were equally effective for divergence excess IXT with comparable outcomes of both distance and near deviations.

Functional changes in fusional vergence-related brain areas and correlation with clinical features in intermittent exotropia using functional magnetic resonance imaging

To explore the functional changes of the frontal eye field (FEF) and relevant brain regions and its role in the pathogenesis of intermittent exotropia (IXT) children via functional magnetic resonance imaging (fMRI). Twenty-four IXT children (mean age, 11.83 ± 1.93 years) and 28 normal control (NC) subjects (mean age, 11.11 ± 1.50 years) were recruited. During fMRI scans, the IXT children and NCs were provided with static visual stimuli (to evoke sensory fusion) and dynamic visual stimuli (to evoke motor fusion and vergence eye movements) with binocular disparity. Brain activation in the relevant brain regions and clinical characteristics were evaluated. Group differences of brain activation and brain-behavior correlations were investigated. For dynamic and static visual disparity relative to no visual disparity, reduced brain activation in the right FEF and right inferior occipital gyrus (IOG), and increased brain activation in the left middle temporal gyrus complex (MT+) were found in the IXT children compared with NCs. Significant positive correlations between the fusional vergence amplitude and the brain activation values were found in the right FEF, right IPL, and left cerebellum in the NC group. Positive correlations between brain activation values and Newcastle Control Scores (NCS) were found in the left MT+ in the IXT group. For dynamic visual disparity relative to static visual disparity, reduced brain activation in the right middle occipital gyrus, left cerebellum, and bilateral IPL was found in the IXT children compared with NCs. Significant positive correlations between brain activation values and the fusional vergence amplitude were found in the right FEF and right cerebellum in the NC group. Negative correlations between brain activation values and NCS were found in the right middle occipital gyrus, right cerebellum, left IPL, and right FEF in the IXT group. These results suggest that the reduced brain activation in the right FEF, left IPL, and cerebellum may play an important role in the pathogenesis of IXT by influencing fusional vergence function. While the increased brain activation in the left MT+ may compensate for this dysfunction in IXT children.

Comitant strabismus etiology: extraocular muscle integrity and central nervous system involvement-a narrative review

Strabismus is not a condition in itself but the consequence of an underlying problem. Eye misalignment can be caused by disease, injury, and/or abnormalities in any of the structures and processes involved in visual perception and oculomotor control, from the extraocular muscles and their innervations to the oculomotor and visual processing areas in the brain. A small percentage of all strabismus cases are the consequence of well-described genetic syndromes, acquired insult, or disease affecting the extraocular muscles (EOMs) or their innervations. We will refer to them as strabismus of peripheral origin since their etiology lies in the peripheral nervous system. However, in most strabismus cases, that is comitant, non-restrictive, non-paralytic strabismus, the EOMs and their innervations function properly. These cases are not related to specific syndromes and their precise causes remain poorly understood. They are generally believed to be caused by deficits in the central neural pathways involved in visual perception and oculomotor control. Therefore, we will refer to them as central strabismus. The goal of this narrative review is to discuss the possible causes behind this particular type of eye misalignment and to raise awareness among eyecare professionals about the important role the central nervous system plays in strabismus etiology, and the subsequent implications regarding its treatment. A non-systematic search was conducted using PubMed, Medline, Cochrane, and Google Scholar databases with the keywords "origins," "causes," and "etiology" combined with "strabismus." A snowball approach was also used to find relevant references. In the following article, we will first describe EOM integrity in central strabismus; next, we will address numerous reasons that support the idea of central nervous system (CNS) involvement in the origin of the deviation, followed by listing several possible central causes of the ocular misalignment. Finally, we will discuss the implications CNS etiology has on strabismus treatment.

Efficacies of preoperative prism adaptation test and monocular occlusion for detecting the maximum angle of deviation in intermittent exotropia

Background

The efficacies of prism adaptation test (PAT) and monocular occlusion (MO) and their optimal test durations to detect the maximum angles of deviation at near and distance in eyes with intermittent exotropia (IXT) were assessed and compared.

Methods

We retrospectively reviewed the medical records of 72 patients with IXT. All the patients had undergone the initial strabismus surgery between April 2015 and October 2018 and had been preoperatively tested by both PAT and MO performed on different days for 30 and 60 min. Near and distance deviations after 30 and 60 min of PAT and MO were compared to their baseline measurements obtained immediately after prism wear and before occlusion by alternate prism cover test. The near/distance measurements and required test duration to reveal the maximum deviation angle were also compared between PAT and MO.

Results

Compared with the baseline, the near deviation by PAT significantly increased after 30 (P < 0.05) and 60 (P < 0.01) minutes but not the distance deviation. However, the increase after 30 min was not significant. By MO, neither near nor distance deviation showed a significant difference from the baseline after 30 and 60 min. PAT showed a significantly larger near deviation than MO at 30 and 60 min, but a larger distance deviation by PAT was only observed at 30 min.

Conclusions

In patients with basic and convergence insufficiency types of IXT, a 30-minute PAT appears to be more effective than MO in revealing the maximum angle of deviation before strabismus surgery.