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J. V. Mehta, D. Newsham; Accommodative Facility: Normative Values and Its Relation to Binocular Functions. Invest. Ophthalmol. Vis. Sci. 2010;51(13):802.
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Normative data for monocular and binocular accommodative facility (MAF & BAF) has not been re-evaluated since the 1980s and there have been no reported normative MAF values for the 30-45yrs age group. Therefore, the aim of this study is to determine normative values for MAF and BAF in subjects aged 16-45 yrs of age and assess if there is a relationship between BAF and binocular functions.
Fifty subjects (age 16-45 yrs) were recruited and normative data was analysed for 35 subjects with normal accommodative amplitude (AA). MAF and BAF were tested with ± 2.00DS flipper lenses at 40cms over a 1 min period (cycles per min-cpm). The number of cycles completed in each 30 sec period was noted to check for a practice or fatigue effect. Binocular functions were assessed with prism fusion amplitude (PFA) and near point of convergence (NPC). Subjects completed a questionnaire before the examination to establish the presence of any binocular or accommodative symptoms. Subjects with reduced AA(n=15) were later included in the analysis to determine the relationship between symptoms and accommodative/binocular functions.
Median [IQR] normative values were calculated for three different age groups; 16-25yrs (n= 16, Right AF: 8cpm [2.5,12], Left AF: 11cpm[3.5,14], BAF: 10[5.5,13]), 26-35 yrs (n=10, Right AF: 6[3,10], Left AF: 7.5[3,10.5], BAF: 4[1,9]) and 36-45 yrs (n=9, Right AF: 0.5[0.5,6.5], Left AF: 4[1,8], BAF: 2.5[1,7]). A significant negative correlation was found between BAF and age (r=-0.5, p=0.001). Monocular AF tended to decline with age but was not significant (RE; r= -0.3, p=0.05 and LE; r= -0.3, p=0.07). There was no correlation (p>0.05) between BAF and PFA (r=-0.06) or NPC (r=-0.3) but BAF was significantly greater for those with normal (8cpm [3, 12.5]) than abnormal NPC (4 cpm [1, 5]; p=0.01). Comparison of the 30 sec periods showed significant differences between cycles achieved in the first and second 30 secs of MAF testing (p<0.05). There was no significant association between symptoms and reduced AF, PFA or NPC (p>0.05).
BAF significantly declined through the older age groups compared to 16-25 yr old subjects and there was a trend to show that MAF also reduced with age. Reduced BAF in patients with remote NPC suggests there is an indication for testing and exercising BAF in these patients. The variability in CPM between the two 30 sec periods highlights the need for rigorous evaluation of AF reliability before it can be recommended as a useful clinical tool. Hence, it would be prudent to consider AF as a diagnostic tool for use with other tests when diagnosing accommodative and binocular dysfunctions.
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