Assessment of a score including control and quality of life in intermittent exotropia

Intermittency of deviation in Intermittent Exotropia (IXT) is well assessed by control scores. However, they do not reflect the impact of strabismus on the patient's Quality of Life (QOL). We describe the use of a global score, including control of the deviation using the Lactose score at distance (DCS) and near (NCS), but also the impact on QoL through the assessment of functional signs (FS) and psychosocial impact (PSI). The methodology used to build this IXT Global Score (IXTGS) is described in a previous publication. The goal of this study was to judge the interobserver reliability of this score and its subscores and to evaluate trends in different types of IXT.

Ninety-eight patients aged 3 to 80 years with IXT were included, with exodeviation up to 50 prism diopters (PD). Eleven cases had convergence insufficiency type exotropia, and 87 were basic IXT. All had normal binocular vision. They were examined successively by an orthoptist and a strabismologist who both scored the beforementioned items. Interexaminator variance was evaluated using the IntraclassCorrelation Coefficient (ICC) score.

Interexaminator variations were minor for the score and its subscores, as reflected by high ICC scores. There is a strong correlation between the distance angle of deviation and DCS and PSI, and between Near angle and NCS and FS. Control scores are not correlated with QoL scores, which shows that they explore different aspects, and are complementary.

The proposed IXTGS seems reliable and reproducible. It offers a global view of the case, but it is the analysis of subscores that seems interesting in therapeutic decision-making and follow-up. We believe that the association of an abnormal Control Score and QoL score should prompt treatment. If only one of them is affected, decision of treatment should be discussed.