Evaluation of Refractive State in Patients with Unilateral Congenital Nasolacrimal Duct Obstruction

To evaluate refractive state in patients with unilateral congenital nasolacrimal duct obstruction. In this descriptive prospective study, patients with unilateral congenital nasolacrimal duct obstruction scheduled for surgery were enrolled over a period of two years (2007-2009). Cycloplegic refractive error in both eyes was measured under anesthesia before surgery (probing, silicon intubation or dacryocystorhinostomy). When more than one procedure was required, only the first refraction was considered for analysis. Anisometropia greater than 0.5 diopter was defined as clinically significant. Ninety-four patients with mean age of 25.4±20.4 months (range: 6 month to 10 years) entered the study. In older ages the prevalence of clinical signs secondary to nasolacrimal obstruction such as discharge and epiphora increased, however, this was not statistically significant (r=0.115 & P=0.270). Spherical equivalent refractive error in 78 (83%), 8 (8.5%) and 8 (8.5%) affected eyes was hyperopic, myopic and emmetropic, respectively. Corresponding figures in unaffected eyes were 67 (71.3%), 22 (23.4%) and 5 (5.3%), respectively. The prevalence of anisometropia greater than 0.5 D was 25% and that of less than 0.5 D was 43%. Anisometripia was not present in 32% of patients. Each month increase in patient's age was associated with 0.007 D higher difference in spherical refractive error between two eyes (P=0.019). For cylindrical refractive error, this change was negative and non-significant (P=0.291) and for spherical equivalent it was positive but non-significant (P=0.137). In older ages, more surgeries were needed (r=0.297, P=0.004). Anisometropia increase with age and more time is necessary to relieve the obstruction during surgery. Anisometropia specially anisohyperopia in older subjects becomes more common and also difficult to treat. Early refraction and intervention help to prevent amblyopia and may reverse the anisometropia.