Risk factors for keratoconus in Israel: a case-control study.
OBJECTIVE
Keratoconus (KC) is a progressive corneal thinning disorder with an uncertain aetiology. Environmental and genetic factors, including consanguinity, eye rubbing and possibly sun exposure, play a role in the aetiology of KC. Here we test for risk factors for KC in an Israeli population with particular emphasis on sun exposure.


METHODS
This case-control study included KC patients who were diagnosed at Care Laser Medical Group, a refractive surgery clinic with branches throughout Israel. The control group included age, sex and ethnicity matched individuals who were randomly selected from patients presenting at the clinic for refractive surgery, but without KC. Study subjects were asked to fill out a self-administered questionnaire that included demographic and geographic details, questions on ocular and general health and sun exposure. Conditional logistic regression was used to analyse univariable and multivariable data to identify risk factors for KC.


RESULTS
Seventy-three KC patients and 146 controls participated in the study. Univariable analyses demonstrated that eye rubbing [odds ratio (OR) = 3.76], positive family history of KC (OR = 6.10) and parents' education (<12 years, OR = 0.27, 0.23 for father's and mother's education respectively) were significant risk factors for KC. Univariable analyses of sun exposure behaviour during teenage years proved equivocal with some behaviours emerging as protective for KC (wearing a hat outdoors, OR = 3.13) or as risk factors (spending time in the shade, OR = 0.45), while others showed no association [limiting time in the sun (p = 0.51), and wearing sunglasses (p = 0.20)]. Most of the factors that were significant in the univariable analyses, also emerged as statistically significant in the multivariable model (OR = 3.37, 9.68, 0.35, 5.51 for eye rubbing, family history, parental education, wearing a hat outdoors, with the exception of spending time in the shade (p = 0.88).


CONCLUSIONS
Eye rubbing, parents' education (as a measure of socio-economic status) and having family members with KC emerged as significant risk factors for KC. The role of sun exposure in KC remains equivocal and warrants further research.
Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel.
Ariela
A
Gordon-Shaag
School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales.
Michel
M
Millodot
CARE Laser Medical Group, Tel Aviv, Israel.
Igor
I
Kaiserman
CARE Laser Medical Group, Tel Aviv, Israel.
Tzahi
T
Sela
Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel.
Guy
G
Barnett Itzhaki
Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel.
Yaffa
Y
Zerbib
Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel.
Efrat
E
Matityahu
Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel.
Shira
S
Shkedi
Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel.
Svetlana
S
Miroshnichenko
Department of Optometry and Vision Science, Hadassah Academic College, Jerusalem, Israel.
Einat
E
Shneor
D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D019781:Corneal Topography; D004522:Educational Status; D005260:Female; D006801:Humans; D007557:Israel / Q000453:epidemiology; D007640:Keratoconus / Q000453:epidemiology / Q000209:etiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D013472:Sunlight / Q000009:adverse effects
Case-control; cornea; epidemiology; keratoconus