Myopic Progression and Postoperative Exodrift in Patients with Intermittent Exotropia

Abstract

PURPOSE: To investigate the relationship between myopic progression and exodrift after surgery in patients with intermittent exotropia (X[T]). METHODS: One hundred eighteen patients who underwent bilateral lateral rectus recession for X(T) and had a follow-up of more than 1 year were recruited. Progression of myopia was determined by measuring the difference in spherical equivalent of both eyes between the initial and final refraction divided by the total follow-up time per patient. Postoperative exodrift was calculated by subtracting the deviation at postoperative 6 weeks from the deviation at the last follow-up, and the deviation at postoperative day 1 from the deviation at postoperative 6 weeks. Linear regression was conducted to determine the relationship between postoperative exodrift and myopic progression. The risk factors for recurrence, defined as exodeviation of 10 prism diopters or more at the final examination, were also analyzed. RESULTS: Sixty-eight (57.6%) subjects showed myopic progression of -0.50 diopters or more, and 53 (44.9%) had recurrence of exotropia during the mean follow-up period of 37.9 months. Patients with myopic progression showed more exotropic drift after surgery than the patients without myopic progression (P<0.001). Immediate postoperative overcorrection, oblique dysfunction, and a short follow-up period were associated with a low recurrence, whereas preoperative angle of exodeviation, sensory status, and age at the time of surgery were not. CONCLUSION: In patients who underwent bilateral lateral rectus recession for X(T), a greater myopic progression was related with greater postoperative exodrift. As the development of myopia was observed to be axial in nature, the results from the present study raises the possibility that ocular elongation may reduce the effect of recession.

간헐외사시에서 근시 진행과 수술 후 외편위 재발간의 상관관계를 알아보고자 하였다. 간헐외사시로 양안 외직근후전술을 시행받고 1년 이상 추적관찰이 가능하였던 118명의 의무기록을 후향적으로 조사하였다. 마지막 내원시와 수술 전 굴절이상의 차이를 추적관찰기간으로 나눈 값을 근시 진행량으로, 마지막 내원시와 수술 후 6주, 수술 후 첫날 외편위의 차이를 수술 후 재발한 외편위량으로 하여 이들간의 상관관계를 분석하였다. 이외에 재발과 관련된 임상적 특징도 살펴보았다. 평균 37.9개월 경과관찰 중 68명(57.6%)에서 -0.50디옵터 이상의 근시 진행이 있었고, 53명(44.9%)에서 10프리즘디옵터 이상의 외편위 재발이 있었다. 근시 진행량이 많을수록 수술 후 재발한 외편위량이 많았다(P<0.001). 수술직후 과교정이 되거나, 사근기능항진이 동반된 경우, 추적관찰기간이 짧은 경우에 외편위 재발이 적었으나, 수술 전 외편위량과 감각상태, 수술나이는 재발과 관계없었다. 간헐외사시에서 근시 진행이 많을수록 재발한 외편위량이 많았다. 이는 축성근시 진행에 따른 안축길이 증가로 외직근후전술의 효과가 상대적으로 감소하였을 가능성을 제시한다.