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Diabetic Retinopathy.  Several studies published in the last five years have 
provided evidence that risk factors for diabetic retinopathy (DR) deserve further 
study.  Estimates of the prevalence of DR among youth with T1D vary from 4.6% 
(39)
 to 20% (mean duration 6.8 yr) 
(40)
.  Interestingly, the prevalence of retinopathy 
among Australian youth with T1D declined significantly over three time periods 
(1990-1994, 1995-1998, 1999-2002) from 49% in the first time period to 24% in 
the second time period 
(41)
, despite matching these cross-sectional analyses on age 
and diabetes duration (median duration, 7.5 yr) with no difference over time in 
HbA
1c
.  The authors postulated that a much higher proportion of youth were on 
more intensive insulin regimens in later years, and this may have contributed to 
the decline in DR prevalence.  Cheung et al 
(42)
 reported incidence of DR among 
645 initially retinopathy-free T1D youth age 12-20 yrs of 14.8 per 100 person 

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Section 4B - Study Objectives/Background and Significance (Phase 3 - 12/2010) 
Section 4B - Page 7 
 Cohort 
Study
 
 
years, over a median follow-up of 2.5 yr.  Longer duration of T1D, lower BMI, 
and higher A1c were significantly associated with incidence of DR, as was larger 
retinal arteriolar caliber.  Differences in mean arterial blood pressure, gender, and 
albumin excretion rate did not significantly predict DR.  
The literature on youth with T2D is even more limited.  From the Australian 
cohort, prevalence was 4%, however only 25 youth with T2D were evaluated for 
retinopathy (mean duration 1.3 yr).  Among 15 youth with T2D (mean duration 
2.1 yr), no retinopathy was detected; however several retinal abnormalities were 
detected that were absent among non-diabetic control youth 
(43)
.  Associations of a 
variety of measurements of retinal vascular caliber to the incidence and 
progression of DR are an active area of research 
(42-45)
. 
There are no data available to enable evaluation of risk factors for early DR in a 
contemporary multi-ethnic cohort of adolescents with T1 and T2D in the US.  In 
Year 5 of SEARCH 2, we initiated a pilot study of the feasibility of obtaining 
retinal photos as part of the SEARCH follow-up visit protocol.  To date, 325 
SEARCH DR pilot participants have had retinal photos completed and 20% of 
these have evidence of DR in at least one eye.  SEARCH is uniquely positioned to 
obtain critical information on the prevalence of and risk factors for DR among 
youth by diabetes type and race/ethnicity as well as by risk factor data obtained 
from earlier study visits.