Effect of Horizontal Strabismus Surgery on the Astigmatism
Kitthisak Kitthaweesin MD*, Sansanee Singhakul MD*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Khon Kaen University, Khon Kaen
Objective : To investigate the effect of horizontal rectus muscle surgery on astigmatism.
Materials and Methods : A prospective descriptive study was conducted between July 2004 and June 2005, we
recruited 16 strabismic patients with bilateral recession or recession of one horizontal muscle or monocular
recession and resection for this study at Srinagarind Hospital. The authors measured the patients’ best-
corrected visual acuity and ocular alignment using the prism cover test and the Modified Krimsky tests,
respectively. Auto-refraction was performed on the pre- operative and first post operative day by a technician
not apprised of the type and/or amount of surgery. Any differences between the pre-operative and post operative
astigmatism were calculated using the x-y coordinate system and the mean value for astigmatism. Descriptive
statistics were used to analyze the data.
Results : Included were 23 eyes from 16 patients who met the inclusion criteria; 8 females; 8 males; average
age 14.75 + 11.76 (range, 4-40) years. Seven patients (43.75%) had esotropia and nine (56.25%) exotropia.
For all procedures, the respective mean cylinder of the pre- operative and first post-operative day were 0.74
+ 1.20 D in 67.56° axis and 0.69 + 0.86 D in 56.30° axis, in the same direction as the cylinders for each type.
There was no statistically significant change in the refractive error between the pre- operative and first post-
operative day.
Conclusion : In contrast to previous studies, astigmatism was not significantly affected by horizontal rectus
muscle surgery; however, the present study population was small. Therefore, a larger prospective control trial
would be necessary to definitively answer this question.
Keywords : Astigmatism, Horizontal strabismus surgery
