A retrospective analysis of heterophoria values in a clinical population aged 18 to 30 years

Abstract

Information on heterophoria values in South Africans  is  scanty. The  purpose  of  this  paper therefore, is to present information on the distribution of heterophoria in a clinical popula-tion aged 18 to 30 years, which hitherto is not available. The data presented here was obtained from  the  record  cards  of  475  black  South African  patients  examined  at  the  Optometry clinic, University of Limpopo (Turfloop cam-pus) between 2000 and 2005. The patients were examined by final year students under the supervision  of  qualified  optometrists.  Heterophoria was  measured  for  each  patient  using  the  von Graefe  method.  The  horizontal  heterophoria for distance vision (6 m) ranged from 16 prism diopters (pd) esophoria to 12 pd exophoria with a mean of 0.74 pd exophoria (SD = ± 2.84 pd). For  distance  vision,  esophoria  ranged  from 0.5 to 16 pd with a mean of 3.08 pd (SD = ± 3.09), while exophoria ranged from 0.5 pd to 12 pd with a mean of 2.21 pd (SD = 1.82 pd). For near vision (0.4 m), the horizontal phorias ranged from 17 pd esophoria to 15 pd exopho-ria with a mean of 3.84 pd exophoria (SD = ± 4.80 pd). The near esophorias ranged from 0.5 to 17 pd with a mean 4.88 pd (SD = ± 3.41), while the exophorias ranged from 1.0 to 15 pd with a mean of 6.30 pd (SD = ± 2.58). Vertical heterophoria for distance vision ranged from 5 to 3 pd right hyperphoria with a mean of 0.05 pd right hyperphoria (SD = ± 0.76) whereas at near it ranged from 4 to 6 pd right hyperphoria with a mean of 0.08 pd right hypophoria (SD =  ±  0.96).  The  distributions  of  heterophoria at distance and near were non-normal.  There was  no  significant  gender  variation  in  the horizontal  values  for  distance  vision  and  the vertical  (distance  and  near)  ones.  However, there was a statistically significant gender varia-tion  in  the  near  horizontal  values  (p  >  0.05). There  was  no  significant  variation  in  heterophoria  values  with  age.    The  data  presented here will be useful for comparison with simi-lar data from South Africa or other countries.