Applicant Last Name:
2015 Standard Research Grant Application
Submission must be delivered to the ISPB Office,
211 W. Wacker Drive, Suite 1700, Chicago, IL 60606
by 12:00 Noon, Tuesday, May 5, 2015
Submit one (1) original application and attachments (paper clipped)
and 12 copies of both the application and the attachments (stapled)
Research Project Title: Adaptive Optics Imaging of Micro-aneurysms and Photoreceptor Layer in
Early Diabetic Retinopathy and Predictors of Disease Progression
Funding Request: $ 5,000
CONTACT INFORMATION
PROPOSAL
Eye Disease Subspecialty or Discipline: Diabetic Retinopathy
Project Abstract
Diabetic retinopathy (DR) is the most common microvascular complication of diabetes mellitus (DM)
and the leading cause of blindness in the working-age population in the United States. Early
pathologic changes, including micro-aneurysms (MA) and subclinical retinal ischemia, often go
undetected as vision is typically preserved. Development of vision threatening complications,
including retinal bleeding, swelling and abnormal blood vessel growth, follow progression of these
early microvascular changes, but little is known regarding why some progress while others stay quiet.
A major limitation of studying microvascular and cellular level changes has been their miniscule sizes
and our inability to image with the necessary resolution in the living eye. Emerging adaptive optics
(AO) retinal imaging techniques, which compensate for ocular wavefront aberrations and greatly
improve imaging resolution, allow for highly detailed, noninvasive in vivo study of retinal
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microvascular changes and photoreceptor density.1 In our study, noninvasive AO imaging will be
used to measure and characterize MAs, grade MA internal blood flow turbulence, and measure
photoreceptor density in patients with early DR (Figure 1 and 2). Findings will be correlated with
disease progression and need for treatment at 6 and 12 month follow-up visits. As preventative DR
treatment advances, identification of MA rupture or leakage risk characteristics, related to dimension,
morphology and fluid dynamics, is becoming increasingly valuable. Furthermore, identification of AO
imaging findings that correlate with DR disease progression may allow for selection of early
intervention candidates.
Figure 1. AO retinal imaging performed at Northwestern University Department of Ophthalmology
A) Single frame from video depicting fusiform micro-aneurysms and internal blood flow. B) Single,
non-averaged frame depicting healthy perifoveal photoreceptor outer segments.
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Figure 2. Perifoveal photoreceptor loss in a diabetic patient. Optical coherence tomography B-scan
with adaptive optics images from corresponding photoreceptor outer segment regions.
Purpose of Project or Hypothesis Being Tested
Micro-Aneurysms
MAs develop in early DR, and their rate of formation has been associated with progression to
clinically significant macular edema, but individual leakage or rupture risk parameters of MAs have
not been established, mainly due to their minuscule size and lack of high-resolution imaging.2 MA
anatomical morphology has recently been characterized based on fluorescein angiography
appearance, however little is known regarding the relationship between MA dimensions and
morphology and association with leakage risk and disease progression. 3 Our AO imaging system
allows for noninvasive, detailed measurement and classification of MAs. Additionally, internal MA fluid
dynamics is suspected to drive MA enlargement and leakage, however in vivo evidence in human
eyes is lacking.4 Monitoring blood flow and turbulence in the retinal microvasculature is made
possible with AO imaging videos due to the RBC/plasma reflectance gradient.5,6 Development of a
turbulence grading criteria may aid in the identification of high risk MAs and facilitate patient selection
for preventative treatment studies. Finally, in patients that do have disease progression and require
therapy with anti-vascular endothelial growth factor (VEGF) agents, additional imaging and analysis
following treatment completion will identify any MA treatment responses.
Photoreceptor Density
3
Retinal ischemia, and resultant oxidative stress and VEGF production, is another early DR change
that leads to disease progression, this time in the form of neovascularization. Photoreceptors have
been identified as the major producer of superoxide and inflammatory proteins involved in this
process.7 A recent study found a decrease in parafoveal cone density in some early DR patients,
however the prognostic value of this finding is unknown.8 AO has proven to be a reliable method of
high-resolution photoreceptor imaging and has reproduced photoreceptor density and distribution
measurements reported by histology.9 Therefore, AO imaging and semi-automated photoreceptor
quantification will allow us to compare photoreceptor density in early, nonproliferative DR to healthy
control retinas. Furthermore, as photoreceptor loss may be a marker of disrupted blood flow and
ischemia, a correlation between photoreceptor density and disease progression, including
neovascularization, will be investigated.
Our long term goal is to define early, noninvasive predictors of DR progression. The purpose of
this project is to measure MA metrics and photoreceptor density using AO imaging in diabetic
patients with mild and moderate nonproliferative retinopathy and collect follow up clinical data
regarding disease progression and treatment need.
Hypothesis 1: AO imaging can be used to measure MA dimensions, classify MA morphology and
grade MA internal blood flow turbulence in DR.
Hypothesis 2: Photoreceptor density will be decreased in diabetic patients with mild and moderate
non-proliferative retinopathy compared to healthy controls.
Hypothesis 3: MA characteristics and photoreceptor density will correlate with DR disease
progression and treatment need at 6 and 12 month follow-up visits.
Who Will Benefit from this Research?
This work aims to benefit researchers, clinicians and patients with DM by providing a better
understanding of early DR pathophysiology and identifying correlations between AO imaging based
measurements and disease progression and future treatment need. Furthermore, identifying “high
risk” MAs and the significance of early photoreceptor loss will facilitate the future study of earlier
treatment intervention.
Specific Goals/Outcomes of Research Project
Specific Aim 1: Use non-invasive AO imaging to measure MA dimensions, classify MA morphology
and grade MA internal blood flow turbulence in early DR patients as well as in DR patients who have
completed anti-VEGF treatment courses.
Specific Aim 2: Use AO imaging to compare photoreceptor density in early DR patients to healthy
controls.
Specific Aim 3: Correlate MA characteristics and photoreceptor density with DR disease progression
and treatment need at 6 and 12 month follow-up visits.
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Materials and Methods to Be Used
Retinal Imaging and Analysis
Adaptive Optics Scanning Laser Ophthalmoscopy (AO-SLO) is an imaging system that allows for
highly detailed, non-invasive in vivo study of retinal microvasculature and photoreceptor
microstructure. Components of the AO system include a wavefront sensor that measures ocular
aberrations and a deformable mirror to compensate for these aberrations. Patients with DM identified
as having mild or moderate nonproliferative retinopathy, as well as healthy, age-matched controls, will
be imaged with the AO-SLO system. MA dimensions will be measured and morphology will be
categorized according to the retinal MA anatomical classification described by Dubow et al.3
Noninvasive video visualization of blood flow dynamics, made possible with AO-SLO, will be used to
grade internal MA blood flow turbulence.5,6 MA blood flow turbulence will be graded as mild,
moderate or severe based on the AO-SLO captured video; two graders will grade all videos and interrater reliability will be calculated. In vivo measurement of photoreceptor density in the diabetic cohort
and healthy controls will be performed using a semi-automated algorithm validated by Liu et al.10 As
axial length affects photoreceptor density, patient and control axial lengths will be measured using an
IOL Master optical biometry machine and integrated into the density calculations.11 In patients that
have disease progression, AO-SLO images will be repeated after completion of a treatment course to
assess the response of MAs to anti-VEGF therapy.
Clinical Data
Clinical data, including diagnosis of DM-type 1 or 2, currently used hypoglycemic agents and level of
recent glycemic control (A1C) will be obtained from the patient’s electronic medical record.
Ophthalmologic follow up at 6 and 12 months will be performed to assess for disease progression,
including development of MA leakage, macular edema and neovascularization, and to assess for
current treatment need.
Statistical Evaluation to Be Used
SPSS software will be used to analyze and determine level of significance in our findings.
Comparisons of photoreceptor density in diabetic patients and healthy controls will be analyzed using
student’s t-test. Correlations between MA dimensions, classifications, blood flow dynamics and
photoreceptor density and disease progression and treatment need will be analyzed using student’s ttest or Pearson correlation coefficient. Sub analysis of patients with DM-type 1 or 2 as well as
calculation of partial correlation coefficients to control for A1C will be performed.
Human Subjects
No
x
Yes
Approval Date: 2/12/15
Enclose copy of Approval Letter
Animal Subjects
No
x
Yes
Approval Date __________ or Pending anticipated date ________
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Is this a sole project or an aspect of a larger research project?
Sole
If part of a larger project, what are the other funding sources and amounts?
NA
BUDGET
Funds cannot be used for major equipment, computers, software (may consider software specialized
to the research), indirect costs, institutional administrative fees, salaries, statisticians, manuscript
preparation, publication costs, phone usage or travel.
Budget Category
Budgeted Cost
(Provide in detail “Supplies” or “Other”
will not be considered)
(Round numbers)
AO-SLO imaging fee
Subject compensation
$ 3,375
$ 1,500
$
$
$
$
$
$
$
$150 scientific poster
allowance and ARVO dues
(optional)
TOTAL
$ 125
$
$ 5,000
Budget Narrative
(Provide detail and justification for budgeted items.)
AO-SLO imaging fee: Technical and equipment use in the photography division will cost $45 per
subject. Based on 75 subjects, we have budgeted for $3375
Subject compensation: Subjects will be compensated $20 for their time and participation. Based on
75 subjects, we have budgeted for $1500
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CURRICULUM VITAE
AUTHORIZATION
ATTACHMENTS
REFERENCES
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10.
11.
Seyedahmadi BJ, Vavvas D. In vivo high-resolution retinal imaging using adaptive optics.
Seminars in ophthalmology. Sep-Nov 2010;25(5-6):186-191.
Nunes S, Pires I, Rosa A, Duarte L, Bernardes R, Cunha-Vaz J. Microaneurysm turnover is a
biomarker for diabetic retinopathy progression to clinically significant macular edema: findings
for type 2 diabetics with nonproliferative retinopathy. Ophthalmologica. Journal international
d'ophtalmologie. International journal of ophthalmology. Zeitschrift fur Augenheilkunde.
2009;223(5):292-297.
Dubow M, Pinhas A, Shah N, et al. Classification of human retinal microaneurysms using
adaptive optics scanning light ophthalmoscope fluorescein angiography. Investigative
ophthalmology & visual science. Mar 2014;55(3):1299-1309.
Ezra E, Keinan E, Mandel Y, Boulton ME, Nahmias Y. Non-dimensional analysis of retinal
microaneurysms: critical threshold for treatment. Integrative biology : quantitative biosciences
from nano to macro. Mar 2013;5(3):474-480.
Arichika S, Uji A, Hangai M, Ooto S, Yoshimura N. Noninvasive and direct monitoring of
erythrocyte aggregates in human retinal microvasculature using adaptive optics scanning laser
ophthalmoscopy. Investigative ophthalmology & visual science. Jun 2013;54(6):4394-4402.
Sulai YN, Scoles D, Harvey Z, Dubra A. Visualization of retinal vascular structure and
perfusion with a nonconfocal adaptive optics scanning light ophthalmoscope. Journal of the
Optical Society of America. A, Optics, image science, and vision. Mar 1 2014;31(3):569-579.
Du Y, Veenstra A, Palczewski K, Kern TS. Photoreceptor cells are major contributors to
diabetes-induced oxidative stress and local inflammation in the retina. Proceedings of the
National Academy of Sciences of the United States of America. Oct 8 2013;110(41):1658616591.
Lombardo M, Parravano M, Lombardo G, et al. Adaptive optics imaging of parafoveal cones in
type 1 diabetes. Retina (Philadelphia, Pa.). Mar 2014;34(3):546-557.
Muthiah MN, Gias C, Chen FK, et al. Cone photoreceptor definition on adaptive optics retinal
imaging. The British journal of ophthalmology. Aug 2014;98(8):1073-1079.
Liu BS, Tarima S, Visotcky A, et al. The reliability of parafoveal cone density measurements.
Aug 2014;98(8):1126-1131.
Park SP, Chung JK, Greenstein V, Tsang SH, Chang S. A study of factors affecting the human
cone photoreceptor density measured by adaptive optics scanning laser ophthalmoscope.
Experimental eye research. Mar 2013;108:1-9.
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