Randomized Trial of Effect of Bifocal and Prismatic Bifocal Spectacles on Myopic Progression

Abstract

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 Ն1.00 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) ϩ1.50-D executive bifocals (n = 48), or (3) ϩ1.50-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 (PϽ.001) and both bifocal groups had less axial elongation (0.21 mm) than the singlevision lens group (P Ͻ.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.

Emmetropisation and the aetiology of refractive errors

“…[71][72][73] If the human eye remains sensitive to defocus why does the later phase of eye growth lead to refractive errors, in particular myopia? An intriguing suggestion is that, as shown in tree shrews, the older eye loses the ability to respond to myopic defocus that might slow or halt eye growth but continues to be sensitive to hyperopic defocus that promotes axial elongation.…”

Myopia, an underrated global challenge to vision: where the current data takes us on myopia control

“…These optical strategies appear to slow the progression of myopia by B30-55% and without adverse effects. [38][39][40][41][42] It has been suggested that reducing the progression of myopia by as little as 33% would reduce the number of highly myopic eyes (4 À 5.00 D) by as many as 75%. 43 Data from a longer term clinical study, involving the use of contact lenses to reduce the hyperopic defocus at the peripheral retina, showed that the ability of these lenses to slow the progression of myopia was a consistent 40% per year over the study period of 43 months.…”

Practical applications to modify and control the development of ametropia

“…58 A more recent trial involving children with myopia randomised to wear single-vision spectacles or executive bifocals with þ 1.50 D add or þ 1.50 D add with 3D base in prism found that over a period of 24 months, myopia progression was on average À 1.55 D for those wearing single-vision spectacles, À 0.96 D for those with executive bifocals, and À 0.70 D for those with executive bifocals with base in prisms. 59 Although the spherical equivalent data showed a greater benefit with executive bifocals incorporating prisms, axial length change showed similar changes with and without prisms (0.62 mm increase with single vision vs 0.41 mm with bifocals and 0.41 mm with bifocals and prism). Even after taking into account the differences in efficacy for axial length and spherical equivalent measures, the slowing of progression is substantial and of significance.…”