Congenital nystagmus: Indication, results and dosage of Kestenbaum surgeryin 34 patients

Background: Abnormal. nystagmus related head postures can be treated by Kes tenbaum's procedure, if the concept of artificial divergence (Cuppers proce dure) is not expected to work. In this retrospective study, we evaluated th e effects of Kestenbaum surgery in order to establish dosage recommendation s. Patients and Methods: Solely patients who received Kestenbaum surgery (maxi mum 3 mm dosage difference between both eyes, i.e., without additional arti ficial divergence) for a horizontal head turn (HT) due to nystagmus were in cluded in this study. Exclusion criteria were previous eye muscle surgery, strabismus, lacking binocular vision, and cerebral disease. The millimetres of surgery and the pre- and 3-6 months-postoperative findings (HT and visu al acuity at 5 m distance, stereopsis) were evaluated. Results: Of the 34 patients, 21 had a HT to the left side and 20 were male. The age at surgery (median, 10%- and 90%-quantile) was 7 years (4-32), the total amount of surgery 32 mm (20-40), and the preoperative HT 30 degrees (20-40). Postoperatively (n = 31), the HT amounted to 7 degrees (0-20). The reduction of HT was 67% (25-100), the efficacy of surgery 0.8 degrees (0.3 -1.0) per millimetre total amount of surgery on both eyes together. Four pa tients needed further surgery due to residual HT. Postoperatively, the maxi mum visual acuity was available without HT or with significantly less HT th an preoperatively. Stereopsis showed a trend of improvement. Conclusions: The Kestenbaum procedure has a dose/effect ratio similar to th at of recess/resect surgery for strabismus. Due to a long term efficacy of 1.5 degrees /mm, a dosage (in millimetres) on each eye of two thirds of the HT (in degrees) can be recommended. Physiological and methodical factors ( false measurements) have to be discussed as an explanation for apparently l ow efficacy of surgery.