The authors investigate the short and long-term postoperative refractive effects of medial rectus recession on the involved eye and explain the detectable effects in detail by the results of vector analysis in 52 eyes and 32 patients. The subjects had a mean age of 8.6 years ±7.8. The results showed a significant difference between the preoperative and one month postoperative spherical equivalent values and the one month and one year values. There was a significant difference between the one month and one year postoperative values of cylinder dioptres and significant differences for surgically induced astigmatism, magnitude of error, flattening effect and astigmatism axis. A myopic shift of approximately 0.5D was seen at one month postoperative and a hypermetropic shift of 0.32D seen at one year postoperative. Changes at one month were considered to be associated with alterations in tension applied by the recessed muscle on the cornea. The effect disappeared by one year.