Abstract
PurposeTo evaluate the effect of Prism adaptation test (PAT) on the angle of squint in decompensated esophoria (decEPH) and decompensated microesotropia (decMET).MethodsIn this single-center retrospective study we reviewed the medical records of patients with the diagnosis of decEPH or decMET, aged at least 12 years, who were treated by strabismus surgery for the first time. The maximum Angle of squint (AOS) for far (F) and near (N) fixation and PAT results before surgery, as well as AOS (F) and AOS (N) after surgery and results of binocular function tests were considered. PAT included wearing a prism based on the largest angle for over 60 min.Results100 patients (mean age 37 ± 17 years) were included in the decEPH group, 82 patients (mean age 30 ± 13 years) in the decMET group. For decEPH, before surgery AOS was 25.5 ± 8.8 pdpt (F) and 23.5 ± 9.8 pdpt (N). During PAT the AOS increased significantly by 2.7 ± 4.3 to 28.2 ± 8.6 pdpt (F) and by 4.9 ± 4.5 to 28.3 ± 9.5 pdpt (N). Altogether, in 82% of decEPH patients AOS (F) and/ or AOS (N) in- or decreased by at least 3 pdpt. For decMET, before surgery AOS was 28.6 ± 10.8 pdpt for far (F) and 30.9 ± 11.8 pdpt for near fixation (N). During PAT the AOS increased significantly by 4.2 ± 5.8 to 32.5 ± 9.5 pdpt (F) and by 3.7 ± 6.1 to 34.4 ± 9.5 pdpt (N). Altogether, in 51% of decMET patients, AOS (F) and/ or AOS (N) increased by at least 10 pdpt, therefore more than 5° which would have been maximally expected from mictrotropia, or decreased by at least 3 pdpt.ConclusionsThe Prism adaptation test (PAT) showed remarkable changes in AOS in both decEPH and decMET. In patients with decEPH, the preoperative assessment of the “true AOS” under PAT reflects a pivotal requirement for successful strabismus surgery, as 82% had dose relevant angle changes ≥ 3 pdpt. For patients with decMET the preoperative prism adaptation test is especially of diagnostic value, but also 51% of decMET patients had changes in AOS beyond the expected microtropic angle (≥ 10 pdpt) or even a dose relevant angle decrease (≥ 3pdpt).
Highlights
The Prism adaptation test (PAT) is widely used in Europe as a means to preoperatively evaluate the maximum Angle of squint (AOS) and determine the necessary dosing of strabismus surgery [1, 2]
The results differed remarkably depending on the type of strabismus: While for intermittent exotropia, decompensated exophoria, and decompensated esophoria 90–98% of surgeons answered to perform PAT prior to strabismus surgery, in patients with infantile esotropia only 49% stated to perform PAT prior to surgery [1]
The aim of this study was to evaluate the effect of PAT on the AOS in decompensated esophoria and decompensated microesotropia
Summary
The Prism adaptation test (PAT) is widely used in Europe as a means to preoperatively evaluate the maximum Angle of squint (AOS) and determine the necessary dosing of strabismus surgery [1, 2]. Evidence from the literature suggests that for acquired esotropia, so-called augmented surgery, in which the surgery was planned according to the prismadapted angle of squint, leads to significantly better results than surgery which was planned without PAT [3]. It remained unclear, whether the increased success was really due to the prism adaptation test or due to an increased total amount of surgery [4] or there might have been other bias to the study [5]. The aim of this study was to evaluate the effect of PAT on the AOS in decompensated esophoria (decEPH) and decompensated microesotropia (decMET)
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