Comparison of Cambridge vision stimulator (CAM) therapy with passive occlusion therapy in the management of unilateral amblyopia; a randomized clinical trial

Introduction: There are limited studies on the effectiveness of Cambridge vision stimulator (CAM) therapy as a management strategy in amblyopic patients. In addition, all these studies have a low sample size. The main purpose of this study was to compare the effect of CAM therapy with passive occlusion therapy in the management of unilateral amblyopia. Methods: In this randomized clinical trial study, 110 cooperative amblyopic children, who had not been managed previously, were randomly divided into two groups of CAM therapy (n = 55) and passive occlusion therapy (n = 55). In the CAM procedure, five discs with different spatial frequencies (SF) (2, 6, 15, 20, 30 cycles/degree) were presented to the patient (30 minutes a day, twice a week). Plates with SF equal to the two lines better than the measured corrected distance visual acuity (CDVA) were chosen. During the training, the non-amblyopic eye was occluded. The standard occlusion therapy protocols were performed in the occlusion therapy group. The CDVA for all patients was measured at baseline and then at one, two, and three months after the treatment. Results: The mean age of patients in CAM and occlusion therapy groups was 7.0 +/- 2.1 and 6.9 +/- 1.9 years, respectively (p = .721). There was no significant difference in the mean CDVA between CAM and occlusion therapy groups after one (0.30 +/- 0.16 vs. 0.25 +/- 0.14, p = .079), two (0.15 +/- 0.10 vs. 0.15 +/- 0.11, p = .732) and three months (0.05 +/- 0.08 and 0.05 +/- 0.06, p = .919) from baseline. However, the mean amount of CDVA increased significantly in each follow-up in both groups (all p < .001). Regarding the amblyopia type and severity, the mean improvement of CDVA from baseline in the anisometropic patients and in moderate amblyopia was significantly higher in the CAM group than the occlusion group after two and three months (p < .05). Discussion: CAM and conventional occlusion therapies significantly improved CDVA in children with amblyopia, and the difference was not significant; therefore, they could be used as alternatives. CAM therapy requires cost and time for the amblyopic patient and parents. Thus, it can be considered as a second treatment option in amblyopic patients, especially anisometropic type and moderate amblyopia, with poor compliance to patching.