Scopo dello studio è determinare se le lenti bifocali hanno la capacità di rallentare l’evoluzione della miopia nei soggetti giovani con un alto grado di progressione miopica (>/= 0,5 D per anno).
Centotrentacinque soggetti affetti da miopia con progressione nell’ultimo anno >/= 0,5 D, sono stati assegnati a 3 gruppi di studio: 1) lenti normali (n=41); 2) lenti bifocali (n=48); 3) lenti bifocali prismatiche (n=46).
I risultati hanno evidenziato come nel gruppo dei soggetti che hanno utilizzato sia lenti bifocali sia lenti prismatiche bifocali, si sia avuta a 24 mesi una progressione della miopia minore rispetto al terzo gruppo (progressione media -0,70 D/-0,96 D per le lenti bifocali prismatiche e lenti bifocali) che ha impiegato lenti correttive normali.
La miopia costituisce uno dei più frequenti problemi refrattivi, con una prevalenza riportata, nei soggetti giovani con più di 12 anni, tra il 50% e il 60%. /em/em
Cheng D, Schmid KL, Woo GC, Drobe B.
Archives of Ophthalmology
2010 Jan;128(1):12-9
Objective To determine whether bifocal and prismatic bifocal spectacles could control myopia in children with high rates of myopic progression.
Methods This was a randomized controlled clinical trial. One hundred thirty-five (73 girls and 62 boys) myopic Chinese Canadian children (myopia of ≥1.00 diopters [D]) with myopic progression of at least 0.50 D in the preceding year were randomly assigned to 1 of 3 treatments: (1) single-vision lenses (n = 41), (2) +1.50-D executive bifocals (n = 48), or (3) +1.50-D executive bifocals with a 3–prism diopters base-in prism in the near segment of each lens (n = 46).
Main Outcome Measures Myopic progression measured by an automated refractor under cycloplegia and increase in axial length (secondary) measured by ultrasonography at 6-month intervals for 24 months. Only the data of the right eye were used.
Results Of the 135 children (mean age, 10.29 years [SE, 0.15 years]; mean visual acuity, −3.08 D [SE, 0.10 D]), 131 (97%) completed the trial after 24 months. Myopic progression averaged −1.55 D (SE, 0.12 D) for those who wore single-vision lenses, −0.96 D (SE, 0.09 D) for those who wore bifocals, and −0.70 D (SE, 0.10 D) for those who wore prismatic bifocals. Axial length increased an average of 0.62 mm (SE, 0.04 mm), 0.41 mm (SE, 0.04 mm), and 0.41 mm (SE, 0.05 mm), respectively. The treatment effect of bifocals (0.59 D) and prismatic bifocals (0.85 D) was significant (P < .001) and both bifocal groups had less axial elongation (0.21 mm) than the single-vision lens group (P < .001). Conclusions Bifocal lenses can moderately slow myopic progression in children with high rates of progression after 24 months.
Applications to Clinical Practice Bifocal spectacles may be considered for slowing myopic progression in children with an annual progression rate of at least 0.50 D.
Trial Registration clinicaltrials.gov Identifier: NCT00787579