Search

Purpose: This study was designed to investigate if the use of different target types or the RAF rule affected the measurement of near point of convergence (NPC)., Methods: The subjects comprised three groups: (1) 20 children aged 6-9 years (2) 17 children aged 11-13 years (3) 14 adults aged 20-30 years. Five targets were used to measure the NPC: (1) pencil tip, (2) fingertip, (3) penlight, (4) N5 letter and (5) vertical line target on the RAF rule., Results: There was no significant difference in NPC measurements between the pencil tip, fingertip and N5 target in free space. The penlight resulted in significantly more remote NPC break and recovery points compared with the fingertip and pencil tip (p < 0.05). The RAF rule influences the NPC obtained (p < 0.001). The greatest difference in NPC measurements was observed when comparing the RAF line target and the finger in free space; the former resulted in NPC values of 1.9 times (95% CI 1.6-2.2 times) as much as those obtained with the finger., Conclusions: Use of the penlight and RAF rule resulted in a more distant NPC break point compared with other targets. The effect of the RAF rule was more apparent for more receded NPC points.

Purpose: Over 75% of children with Down's syndrome fail to accommodate accurately on near targets. This deficit must result in optically blurred images for near work. This present study set out to evaluate the controlled use of bifocal spectacles as an aid to near focusing. Although sometimes used clinically, no systematic studies of bifocals for children with Down's syndrome have been reported., Methods: This was a comparative non-randomised interventional study. Thirty-four children with Down's syndrome of primary school age (5-11 years) took part, assigned in equal numbers to form two matched groups. All children received a full optometric assessment prior to entering the study. The treatment group was prescribed bifocal spectacles with a +2.50 addition, and the control group provided with single vision lenses to correct any clinically significant refractive error. Three follow-up visits were made over a 5-month period after spectacle provision., Results: The treatment group showed consistently more accurate accommodation than the control group both through the bifocal segment, and, unexpectedly, through the distance part of the lens (p < 0.05). Compliance with new spectacles was high in both groups (>82% fully compliant)., Conclusions: Bifocals confer benefit to children with Down's syndrome who under-accommodate, both directly (better focusing through the bifocal) and indirectly (by encouraging improved accommodation through the distance part of the lens). Based on the results of this study, eye examinations of children with Down's syndrome should routinely include a measure of accommodation at near, and bifocal spectacles should be considered for those who show under-accommodation.