|Title||Near Phoria and Near Point of Convergence in Deaf Children|
|Author, Co-Author||Mariza Mavroidis, Baskar Theagarayan, Anuradha Narayanan, Jameel Rizwana Hussaindeen|
Near Phoria and Near Point of Convergence in Deaf Children
Mariza Johansson Mavroidis, Baskar Theagarayan, Anuradha Narayanan, Jameel Rizwana Hussaindeen
Department of Medicine and Optometry, Linnaeus University, Kalmar, Sweden and
Elite School of Optometry, Unit of Medical Research Foundation, Sankara Nethralaya, Chennai, India
Purpose: Deaf people not only use their eyes for seeing; but also for communication, through sign language and facial expressions. Therefore it is extra important to assess and remediate any visual defects. Compared with the general population, increased prevalence of visual defects such as refractive errors and ocular abnormalities among deaf has been reported in literature. The aim of this study was to investigate the parameters of near phoria (NP) and near point of convergence (NPC) among deaf children (group one) and among children with normal hearing (group two).
Methods: A total of 145 subjects in the age of 6 to 15 years were enrolled through school vision screening programmes. Children having uncorrected refractive errors, visual acuity lower than 20/30, N6 and ocular abnormalities other than non-strabismic binocular vision abnormalities, were excluded from this study. In group one (n= 101) and two (n= 43), NPC and NP were measured, in group one with a non-accommodative target and in group two with an accommodative target.
Results: Mean age in group one was 10.8 ± 2.8 years respectively 11.3 ± 2.4 years in group two. Statistical analyses showed a significant difference between the two groups, in both NPC break and recovery (NPC break in group one: 9.69 ± 7.26 cm and in group two: 5.32 ± 4.90 cm, p < 0.01). 55% of the children in group one had a receded NPC of > 10 cm, whilst it was only 16 % in group two. In near phoria, there was no significant difference between the two groups (NP in group one was -4.96 ± 7.59 Δ, and in group two -2.77 ± 5.57 Δ, p= 0.087).
24 % of the children in group one had an exophoria larger than 6Δ, whilst it was only 7 % in group two. In group one, 5.9 % were esophoric, 69.3 % were exophoric and 24.8 % orthophoric. In group two, 54.5 % of the children were exophoric and 45.5 % orthophoric.
A regression analysis was performed to correlate the NPC break with near phoria, combined in the two groups, and it was statistically significant (r = 0.64 and p < 0.01 ).
Conclusion: The results of this study show that deaf school children have a significantly higher prevalence of a receded NPC compared to children without any impairment. Understanding visual symptoms and appropriate remediation is recommended to enhance the quality of life of this special population.
Support: Minor Field Studies grant to Linnaeus University from Sida.
|Affiliation of Co-Authors||Dept Medicine & Optometry, Linnaeus University, Elite School of Optometry, Elite School of Optometry|