Name: using retinal imaging to study dementia
Uploaded: 2017-11-06T17:00:00
Description: Watch this Scientific Journal Video about Using Retinal Imaging to Study Dementia at JoVE.com

We would like to express our appreciation to the School of Computing, National University of Singapore for technical support and the Health and Medical Research Fund (04153506), Hong Kong for funding support.

All methods described here have been approved by a local clinical research ethics committee in Hong Kong.
Note: For simplicity, the equipment listed in the Table of Materials is used to illustrate the procedures of retinal imaging and subsequent analysis. Measurement of retinal vascular parameters is illustrated using the Singapore I Vessel Assessment program (SIVA) 17 (Version 4.0, National University of Singapore, Singapore). However, it should be not...

This protocol describes the procedures of quantifying neuronal and vascular changes in the retina in vivo. As the retina shares similar embryological origins, anatomical features and physiological properties with the brain, these retinal changes may reflect similar changes of vasculature and neuronal structure in the brain. &#160;
As shown in Figure 10 and Table 1, the AD subject showed decreased vessel calibers when compared to the healt...

Owing to increases in life expectancy, dementia has become a major medical problem, contributing to significant social and economic health burden globally1,2,3,4,5. Today, a person in the United States develops Alzheimer&#8217;s Disease (AD), the most common form of dementia, every 66 s6. It has been estimated that by the year 2050, 115 million people will be affected by AD7.&#160; &#160;
The retina offers a unique &#8220;window&#8221; to study dementia due to its similar anatomical and physiological properties with the brain. In terms of vasculature, the retinal arterioles and venules, measuring 100 to 300 &#181;m in diameter, share similar features with cerebral small vessels, such as end arterioles without anastomoses, barrier function, and auto-regulation8,9. In terms of neuronal structure, retinal ganglionic cells (RGCs) share typical properties with neurons in the central nervous system (CNS)10. The RGCs are prominently connected with the brain as they form the optic nerve and project visual signals from the retina to the lateral geniculate nuclei and the superior colliculus. The optic nerve, similar to many neuronal fibers in the CNS, is myelinated by oligodendrocytes and is ensheathed in meningeal layers. Notably, an insult to the optic nerve can result in similar responses observed in other CNS axons, such as retrograde and anterograde degeneration of the axon, scar formation, myelin destruction, secondary degeneration, and an abnormal level of neurotrophic factors and neurotransmitters11,12,13,14. The appearance of visual symptoms in some AD patients may also be explained by the robust associations between the retina and the brain15,16. As a result, it has been suggested that the retina may reflect the pathological processes of dementia in the brain and retinal imaging can be used to study dementia.
The retinal vasculature and neuronal structure can now be visualized non-invasively using retinal imaging techniques. For instance, retinal fundus photographs can be captured using fundus cameras, and characteristics of the retinal vasculature (e.g., vessel caliber, tortuosity, and fractal dimension) can then be quantified using computer-assisted analysis programs. In addition, parameters of the retinal neuronal structure (such as the thickness of ganglion cell-inner plexiform layer [GC-IPL] and retinal nerve fiber layer [RNFL]) can also be measured using optic coherence tomography (OCT) and quantified using the built-in analysis algorithms.
In view of the importance of retinal imaging to studying dementia, this protocol aims to describe a method of imaging and analyzing retinal vasculature and neuronal structure in vivo using retinal imaging techniques. This protocol also provides examples of retinal changes in subjects with dementia, and discusses technical issues and current limitations of retinal imaging.

<table border="0" cellpadding="0" cellspacing="0" width="783">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">Non-mydriatic Retinal Camera&#160;</td>
			<td style="width:188px;">Topcon, Inc, Tokyo, Japan</td>
			<td style="width:119px;">TRC 50DX&#160;</td>
			<td style="width:271px;">N/A</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">Singapore I Vessel Assessment Program</td>
			<td style="width:188px;">National University of Singapore</td>
			<td style="width:119px;">Version 4.0</td>
			<td style="width:271px;">N/A</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">CIRRUS HD-OCT&#160;</td>
			<td style="width:188px;">Carl Zeiss Meditec, Inc, Dublin, CA</td>
			<td style="width:119px;">Model 4000</td>
			<td style="width:271px;">N/A</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">Mydriatic Agents&#160;</td>
			<td style="width:188px;">N/A</td>
			<td style="width:119px;">N/A</td>
			<td style="width:271px;">Prepared from 1% tropicamide and 2.5% phenylephrine hydrochloride</td>
		</tr>
	</tbody>
</table>

using retinal imaging to study dementia

The retina offers a unique &#8220;window&#8221; to study pathophysiological processes of dementia in the brain, as it is an extension of the central nervous system (CNS) and shares prominent similarities with the brain in terms of embryological origin, anatomical features and physiological properties.&#160; The vascular and neuronal structure in the retina can now be visualized easily and non-invasively using retinal imaging techniques, including fundus photography and optical coherence tomography (OCT), and quantified semi-automatically using computer-assisted analysis programs. Studying the associations between vascular and neuronal changes in the retina and dementia could improve our understanding of dementia and, potentially, aid in diagnosis and risk assessment.&#160; This protocol aims to describe a method of quantifying and analyzing retinal vasculature and neuronal structure, which are potentially associated with dementia. This protocol also provides examples of retinal changes in subjects with dementia, and discusses technical issues and current limitations of retinal imaging.

<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/56137/56137fig10.jpg" /> 
Figure 10: An example to show the differences in retinal vasculature between a normal subject and an AD subject. When compared to the normal subject, fundus photograph of the AD subject showed narrower vessel calibers (CRAE of Zone B, 116.4 &#181;m vs. 156.4 &#181;m; CRVE of Zone B, 186.9 &#181;m vs. 207.5 &#181;m; CRAE of Zone C, 138....

Watch this Scientific Journal Video about Using Retinal Imaging to Study Dementia at JoVE.com

Using Retinal Imaging to Study Dementia

The retina shares prominent similarities with the brain and thus represents a unique window to study vasculature and neuronal structure in the brain non-invasively. This protocol describes a method to study dementia using retinal imaging techniques. This method can potentially aid in diagnosis and risk assessment of dementia.

The retina offers a unique &#8220;window&#8221; to study pathophysiological processes of dementia in the brain, as it is an extension of the central ...

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