Article

Outcomes of extraocular muscle surgery for infantile nystagmus syndrome

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Abstract

Purpose: To report outcomes of extraocular muscle surgery to improve visual acuity or correct abnormal head posture(AHP) in patients with infantile nystagmus syndrome(INS). Subject and Methods: Twenty-two patients who underwent extraocular muscle surgery when less than 15 years old(average age at time of surgery, 7.5 years) and were followed up for at least 6 months at Hyogo College of Medicine Hospital from 2006 to 2015 were recruited. The mean followup period was 3.7 years. Large recession of all four horizontal rectus muscles was performed to reduce nystagmus. The Anderson or modified Kestenbaum methods were used to correct AHP. We retrospectively analyzed the surgical methods used to treat INS and the effects on visual acuity, AHP, and binocularity. Results: Twelve patients with a null zone, six without a null zone and jerky nystagmus, three with periodic alternating nystagmus, and one with pendular nystagmus were included. No significant improvement in postoperative binocular visual acuity was observed; however, visual acuity in the more affected eye improved significantly after surgery(p = 0.0001). Of the 11 patients with AHP, five(45%) were free from AHP and three(27%) showed improvement after surgery. Two patients exhibited recurrence of AHP. One patient with albinism and macular hypoplasia was unaffected by treatment. Binocularity did not demonstrate improvement for any type of nystagmus(near, p = 0.0845; distance, p = 0.8516). Conclusion: Extraocular muscle surgery for INS was effective in improving visual acuity in the more affected eye and AHP. However, there is a possibility that AHP could persist in patients with poor vision accompanied by macular hypoplasia.

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Background: Infantile nystagmus syndrome (INS) is a type of eye movement disorder that can negatively impact vision. Currently, INS cannot be cured, but its effects can potentially be treated pharmacologically, optically, or surgically. This review focuses on the surgical interventions for INS. Despite the range of surgical interventions available, and currently applied in practice for the management of INS, there is no clear consensus, and no accepted clinical guidelines regarding the relative efficacy and safety of the various treatment options. A better understanding of these surgical options, along with their associated side effects, will assist clinicians in evidence-based decision-making in relation to the management of INS. Objectives: To assess the efficacy and safety of surgical interventions for INS. Search methods: We searched CENTRAL, MEDLINE Ovid, Embase Ovid, ISRCTN registry, ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) to 3 July 2020, with no language restrictions. Selection criteria: We included randomised controlled trials (RCTs) studying the efficacy and safety of surgical options for treating INS. Data collection and analysis: Our prespecified outcome measures were the change from baseline in: binocular best-corrected distance visual acuity; head posture; amplitude, frequency, intensity, and foveation period durations of the nystagmus waveform; visual recognition times; quality of life and self-reported outcome measures; incidence of adverse effects with a probable causal link to treatment; and permanent adverse effects after surgery. Two review authors independently screened titles and abstracts and full-text articles, extracted data from eligible RCTs, and judged the risk of bias using the Cochrane tool. We reached consensus on any disagreements by discussion. We summarised the overall certainty of the evidence using the GRADE approach. Main results: We only identified one eligible RCT (N = 10 participants), undertaken in India. This trial randomised participants to receive either a large retro-equatorial recession of the horizontal rectus muscle of 9 mm on the medial rectus and 12 mm on the lateral rectus, or a simple tenotomy and resuturing of the four horizontal rectus muscles. We did not identify any RCTs comparing a surgical intervention for INS relative to no treatment. In the single eligible RCT, both eyes of each participant received the same intervention. The participants' age and gender were not reported, nor was information on whether participants were idiopathic or had sensory disorders. The study only included participants with null in primary position and did not explicitly exclude those with congenital periodic alternating nystagmus. The study did not report funding source(s) or author declaration of interests. The evaluation period was six months. We judged this study at low risk for sequence generation and other sources of bias, but at high risk of bias for performance and detection bias. The risk of bias was unclear for selection bias, attrition bias, and reporting bias. There is very uncertain evidence about the effect of the interventions on visual acuity and change in amplitude, frequency, and intensity of the nystagmus waveform. We were unable to calculate relative effects due to lack of data. None of the participants in either intervention group reported adverse effects at six-month follow-up (very low-certainty evidence). There was no quantitative data reported for quality of life, although the study reported an improvement in quality of life after surgery in both intervention groups (very low-certainty evidence). Change in head posture, foveation period durations of the nystagmus waveform, visual recognition times, and permanent adverse effects after surgery were not reported in the included study. We judged the certainty of the evidence, for both the primary and secondary efficacy outcomes, to be very low. Due to a lack of comprehensive reporting of adverse events, there was also very low-certainty of the safety profile of the evaluated surgical interventions in this population. As such, we are very uncertain about the relative efficacy and safety of these interventions for the surgical management of INS. Authors' conclusions: This systematic review identified minimal high-quality evidence relating to the efficacy and safety of surgical interventions for INS. The limited availability of evidence must be considered by clinicians when treating INS, particularly given these procedures are irreversible and often performed on children. More high-quality RCTs are needed to better understand the efficacy and safety profile of surgical interventions for INS. This will assist clinicians, people with INS, and their parents or caregivers to make evidence-based treatment decisions.
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