RESUMO
PURPOSE: To determine the percentage of contribution of the magnitude of posterior corneal astigmatism to total corneal astigmatism using Scheimpflug imaging. METHODS: This prospective cross-sectional study was conducted on 356 eyes of 356 patients, where the total corneal astigmatism was calculated by addition of anterior and posterior corneal astigmatism using vector analysis and then the percentage of posterior to total corneal astigmatism was calculated. RESULTS: The percentage of contribution of posterior to total corneal astigmatism was about 30% in patients with With The Rule astigmatism and about 8% in patients with Against The Rule astigmatism. CONCLUSION: Posterior corneal astigmatism should not be neglected during calculation of total corneal astigmatism as neglecting posterior corneal astigmatism can result in errors during calculation and correction of astigmatism.
RESUMO
PURPOSE: To evaluate pattern collapse and torsional changes following vertical transposition of horizontal recti in patients with V-pattern exotropia and no oblique dysfunction. METHODS: A prospective study was performed on patients who had V-pattern exotropia and no oblique dysfunction. Lateral recti were transposed upward half-tendon width in V-pattern of 25 prism diopters (PD) or less (n = 14) and full-tendon width in V-pattern of greater than 25 PD (n = 10). Amblyopic patients had unilateral lateral rectus recession with upward transposition and medial rectus resection with downward transposition (n = 8). Ductions, versions, pattern strabismus, disc foveal angle, and astigmatic axis were analyzed before and 6 months after surgery. RESULTS: In the 32 patients (21 females), the mean age was 8.25 ± 1.23 years. Only amblyopic patients showed preoperative fundus extorsion (mean disc foveal angle = 16.9°, P < .01). Mean pattern collapse was 13.1 ± 3.8 PD with half-tendon transposition, 35.6 ± 13.7 PD with full-tendon transposition, and 13.8 ± 7.9 PD in the unilateral group. Pattern collapse increased gradually so that pattern normalization occurred after 6 months in most patients. There was a statistically significant correlation between the preoperative V-pattern and the magnitude of pattern collapse after surgery (r = 0.80, P < .01). There were no significant changes in the mean disc foveal angle (< 0.5°) or axis of astigmatism (< 0.5°) in all three groups. CONCLUSIONS: Vertical transposition of horizontal muscles can correct V-pattern exotropia, although the effect might not be immediate. Torsional changes are minimal. Amblyopic patients with V-pattern exotropia showed a preoperative extorsion that did not change after surgery. [J Pediatr Ophthalmol Strabismus. 2019;56(2):107-115.].
