Table 2. A comparison of the prevalence of anisometropia in different racial and ethnic groups. Only studies comparing prevalence in two or more groups are included.

Authors (year) (n) (country)	Anisometropia Criterion/ Examination Methods	Anisometropia Prevalence (%) for different Ethnic Groups (age)	Conclusion/Notes
*Katz et al. (1997) (n=5028) (Population-based survey of ocular disorders among non- institutionalized subjects 40 years of age and older living in east Baltimore, USA)	>1D difference in SE. Subjects underwent Subjective refraction with AO Reichert SR- TV Programmed Subjective Refractor. Refractions were refined as needed for possible overcorrection to eliminate the effect of instrument accommodation. Those who could not respond adequately to automated refraction were refracted using retinoscopy or with manual techniques. Subjects did not undergo cycloplegia.	Caucasian (40-49 yrs.) 5.9% African-American (40-49 yrs.) 3.6% Caucasian (50-59 yrs.) 5.8% African-American (50-59 yrs.) 4.6% Caucasian (60-69 yrs.) 8.4% African-American (60-69 yrs.) 6.8% Caucasian (70-79 yrs.) 14.6% African-American (70-79 yrs.) 9.3% Caucasian (80+ yrs.) 15.5% African-American (80+ yrs.) 14.0%	Caucasians had significantly greater anisometropia than African-Americans. African-Americans had lower rates of all refractive errors, except for hyperopia prevalence in women which was similar in the two groups
Borchert et al. (2010) (n=6024) (Population-based survey. 6-72 month-old subjects identified by door- to-door screening of families within 44 census tracts in/around the city of Inglewood, Los Angeles County, California USA)	≥1D difference in SE. Retinomax autorefraction was performed on all participants after cycloplegia	Hispanic (6 to 72 months) 4.3% African-American (6 to 72 months) 4.2%	Cylinder vector anisometropia more prevalent in African- American children (11.9% versus 10.4%) but no difference between groups for any other anisometropia index.
Saw et al. (2008) (n=2974) (Singapore)	>1D difference in SE.	Singapore Malay population (40 to 80 yrs) 9.9%	Figures quoted for these 3 studies represent the crude/raw figures, not those age-adjusted to Singapore census data.
Wong et al. (2000) (n=1076) (Singapore)	>1D difference in SE.	Singapore Chinese population (40 to 79 yrs) 20.0%
Pai et al. (2011) (n=2762) (Singapore) These are population-based surveys of ocular disorders among adults living in Singapore. The 1996 Singapore electoral register was used for sampling in these studies	>1D difference in SE. Objective refraction result was recorded using an autorefractor (Retinomax K-plus; Nikon, Tokyo, Japan). Manual subjec- tive refraction was then attempted to refine vision, using the results of the objective refraction,. No cycloplegia was used. Those who did not attend the clinic visit were offered an examination in their homes. These refraction were conducted using a handheld autorefractor (Retinomax K-plus; Nikon, Toyko, Japan). No manual subjective refraction was conducted on these subjects.	Singapore Indian population (40+ yrs) 9.9%
Ohlsson et al. (2001) (n=1046) (Sweden) Ohlsson et al. (2003) (n=1035) (Mexico) Population-based studies of 12-13 year old children born in Sweden (conducted in schools in Gothenburg, Sweden) or Mexico (conducted in Monterrey). Parental consent was required prior to participation.	≥1.5D difference in sphere or cylinder ≥1.5D difference in sphere or cylinder. Retinoscopy performed after installation of one or two drops of 0.5% Tropicamide.	Caucasian (12- to 13-yr. olds) 3.3% Central America (12- to 13-yr. olds) 5.3%
Macias et al. (1999) (n=5226). Not population- based. Retrospective study of self-selected adults (aged 25 to 74 year) who received vision screenings/eye examinations in a mobile eye clinic in Los Angeles, USA between 1987 and 1997.	>1D difference in SE. Retinoscopy/ subjective refraction.	Hispanic (18 to 93 years, n=2970): 2.2%* African-American (18 to 94 years, n=1028): 22.3%* Caucasian (18 to 97 years, n=1228): 26.8%*	Caucasians had higher rates of anisometropia, astigmatism and hyperopia compared to the other racial groups. Myopia was more common among African-Americans than the other racial groups.
Giordano et al. (2009) (n=2298, White, n=1030, African- American, n=1268), (Baltimore, USA) Population-based evaluation of the prevalence of ocular disorders in children aged 6 to 71.	≥2D difference in SE. ≥3D difference in SE.	White: 1.5% African-American: 1% White: 0.7% African-American: 0.2%	As well as greater anisometropia prevalence amongst whites, the prevalence of hyperopia of 3D or more in the eye with the lesser refractive error was 8.9% in white children and 4.4% in African- American children. Also, the prevalence of emmetropia (refractive correction from −1D to +1D) was 35.6% in white children and 58.0% in African- American children.

^*Prevalence figures for males and females have been averaged.