This work was supported by Inserm, Universit&#233; Montpellier, Retina France, Union National des Aveugles et D&#233;ficients Visuels (UNADEV), Association Syndrome de Wolfram, Fondation pour la Recherche M&#233;dicale, Fondation de France, and the Laboratory of Excellence EpiGenMed program.

The experimental protocol was approved by the Institut national de la sant&#233; et de la recherche m&#233;dicale (Inserm; Montpellier, France), is consistent with the European directives, and complies with the ARVO Statement for the Use of Animals in Ophthalmic Research. It was carried out under the agreement of the Languedoc Roussillon Comity of Ethics in Animal Experimentation (CEEALR; nuCEEA-LR-12123).
1. Equipment Setup and Pre-imaging Preparation
NOTE: Here, OCT was performed on mouse retinas using the spectral domain (SD) ophthalmic imaging system (Figure 1A). The SD-OCT apparatus consists of a base and an animal imaging mount (AIM) with a rodent alignment stage (RAS) (Figure 1B). The base includes the computer, the OCT engine, the SD-OCT probe, and the mouse-specific lens. The probe is mounted onto the AIM, which includes the Z-translator. The RAS is used for mouse positioning thanks to the table with the X- and Y-translator, the cassette that can be rotated and swiveled, and the removable bite bar with the nose band. The software provided by the manufacturer allows for the acquisition and analysis of OCT files, although the latter may also be done with an open-source image processing program.
<ol>
	<li>Firmly place the probe in the AIM.</li>
	<li>Connect the mouse-specific lens to the probe.</li>
	<li>Adjust the reference arm settings for the specific lens (here, power at 086 and position at 964).</li>
	<li>Making sure that the mouse-specific lens is sufficiently distant from the cassette, attach the bite bar with the nose band onto the cassette. 
	NOTE: The distance between the lens and the cassette may be adjusted with the Z-translator screw, located at the back of the AIM. The nose band is a commercially available elastic band, and its tension should be adjusted depending upon the size of the mouse.</li>
	<li>Turn on the power supply (lower right corner of the cart) and then the computer.</li>
	<li>To launch the imaging program, double-click on the appropriate shortcut on the screen. 
	NOTE: This depends on the type of lens; here, Mouse Retina.</li>
	<li>Create a new Clinical Study and add the desired Protocols. Otherwise, use the existing Clinical Study and/or Protocols.
	<ol>
		<li>Add a new study by choosing the &#34;Study Name&#34;; &#34;ID&#34;; &#34;Treatment Arm Specifications&#34; (here, &#34;Uncategorized&#34;); and predefined &#34;Scan Protocols&#34;, if they exist.</li>
	</ol>
	</li>
	<li>Choose an &#34;Examiner&#34; in the &#34;Clinical Study&#34; section. 
	NOTE: For a new &#34;Examiner&#34;, go to &#34;Setup Examiners &#38; Physicians&#34; to define it.</li>
	<li>Add a new Patient in the Patient/Exam section by click on Add Patient; entering the &#34;ID&#34;, &#34;name&#34;, &#34;surname&#34;, &#34;sex&#34;, and &#34;date of birth&#34; (optional). 
	NOTE: Do this just before testing each mouse, if more convenient. Make sure that the ID is no longer than 10 characters. For the mouse, the refractive error for both eyes is 0 and the axial length is 23.0.</li>
	<li>Click on &#34;Add Exam&#34; and select the desired &#34;Protocol&#34; by adding &#34;Preset Scans&#34; from the list, starting with the eye that will be measured first (here, the right eye), or by customizing the scans.</li>
	<li>To customize a scan, either use an existing scan as a template and edit it, or create it from scratch through the &#34;Add Custom Scan&#34; option. After adding all the scans to the list, define a new protocol using the &#34;Enter &#34;New Protocol Name&#34; option (OS: oculus sinister, left eye; OD: oculus dexter, right eye). 
	NOTE: Here, the protocol involves three scans: (i) a radial scan, with a 1.4 mm diameter, 0 mm horizontal and vertical offsets, 1,000 lines of A-scans/B-scan, 100 B-scans/volume, 1 frame/B-scan, 80 lines of inactive A-scans/B-scan, and 1 volume; (ii) a rectangular scan, with a 1.4-mm length and width, 0&#176; angle, 0-mm horizontal and vertical offsets, 1,000 lines of A-scans/B-scan, 100 B-scans, 1 frame/B-scan, 80 lines of inactive A-scans/B-scan, and 1 volume; and (iii) an annular scan, with a 0.4-mm minimum and 0.6-mm maximum diameter, 0-mm horizontal and vertical offsets, 1,000 lines of A-scans/B-scan, 3 B-scans/volume, 48 frames/B-scan, 80 lines of inactive A-scans/B-scan, and 1 volume.</li>
</ol>
2. Mouse Preparation
<ol>
	<li>Eye dilation and immobilization
	<ol>
		<li>At least 15 min before data acquisition, instill 10% phenylephrine eye drops into the mouse eyes, remove the excess, and instill 0.5% tropicamide eye drops. 
		NOTE: The first dilatation can be done at once for all the mice that will be tested in the session. Make sure that the liquids are at room temperature.</li>
		<li>Immediately after inducing general anesthesia (step 2.2), administer 0.4% oxybuprocaine hydrochloride eye drops, keeping them in place for 3 s to anesthetize and immobilize the eyes. Afterwards, wipe off the drops and repeat the instillation of 10% phenylephrine and 0.5% tropicamide to ascertain that the eyes are well dilated. 
		NOTE: Make sure that the liquids are at room temperature and that the mouse does not swallow the oxybuprocaine.</li>
	</ol>
	</li>
	<li>General anesthesia
	<ol>
		<li>Prepare an anesthetic solution of ketamine (20 mg/mL) and xylazine (1.17 mg/mL) in saline. Store at 4 &#176;C for a maximum of 2 weeks.</li>
		<li>Approximately 5 min before testing, intraperitoneally inject 5 - 10 &#181;L of anesthetic solution per 1 g of body mass, depending upon the age and size of the mouse. 
		NOTE: Young and/or thin mice need less anesthetic, take less time to anesthetize, but also awaken faster. Here, 8 &#181;L/g (160 mg/kg of ketamine, 9.33 mg/kg of xylazine).</li>
		<li>Optionally, lubricate the eyes with viscous eye drops or an ophthalmic gel to avoid corneal dryness.</li>
	</ol>
	</li>
</ol>
3. Mouse Positioning
<ol>
	<li>Lubricate the eyes with viscous glycol-based eye drops to provide corneal hydration. 
	NOTE: If the eyes seem dry during the exam, re-apply the eye drops.</li>
	<li>Wrap the mouse in a sheet of surgical gauze to keep it warm.</li>
	<li>Using a sponge or cotton wick, apply a thin layer of an ophthalmic gel with 0.3% hypromellose onto each eye, to minimize light refraction, avoid opacities, and secure corneal hydration. While doing so, move the eyelashes and whiskers aside.</li>
	<li>Position the mouse in the cassette, with the head straight and pointing forward.</li>
	<li>Gently open the bite bar clamp and place the bar in the mouth; use the nose band to secure the position. 
	NOTE: Ensure that the bite bar is in the middle of the cassette.</li>
	<li>Place a cotton roll under the right (left) side if the right (left) eye is being tested.</li>
	<li>While keeping the clip-on aiming tip on the mouse-specific lens, bring it towards the eye by rotating the Z-translator screw counterclockwise.</li>
	<li>By rotating and swiveling the cassette and by turning the bite bar and the X-translator screws, pre-set the position of the mouse; the goal is to have the right eye look directly into the lens, and thus to align the optical axes of the eyes and the lens. 
	NOTE: If the mouse is too high or too low, the Y-translator screw should be used first.</li>
	<li>Choose the first scan in the &#34;Exam&#34;, click on &#34;Start Aiming&#34;, and make any further manual adjustments for retinal imaging.
	<ol>
		<li>Using the Z-translator screw, move the retina vertically on the left panel (Figure 2, Horizontal B-scan Alignment) and horizontally on the right panel (Figure 2, Vertical B-scan Alignment).</li>
		<li>Rotate the cassette to bring the ONH in the middle of the right panel by moving the ONH up or down. Use the bite bar screw to straighten the retina on the right panel. Swivel the cassette to position the ONH in the middle of the left panel.</li>
		<li>Use the X-translator screw to level the retina on the left panel. Keeping in mind the major function of each modulator, further adjust the position of the retina to centralize the ONH. 
		NOTE: Use the Y-translator screw to move the ONH up and down on the right panel, if necessary. The position may be refined at any time between scans.</li>
	</ol>
	</li>
</ol>
4. SD-OCT Imaging of the ONH and Retina
<ol>
	<li>Once content with the adjustments, click on &#34;Start Snapshot&#34; to begin SD-OCT scanning.
	<ol>
		<li>If a 3D imaging is not required, uncheck the OCU option.</li>
	</ol>
	</li>
	<li>Save the scan and the report.</li>
	<li>Proceed with the next scans.</li>
	<li>To image the second eye, after retracting the lens, turn the cassette accordingly and repeat steps 3.6 - 4.3.</li>
</ol>
5. Acquisition Completion
<ol>
	<li>When the acquisition is complete, remove the mouse from the cassette, apply ophthalmic gel with 0.3% hypromellose to each eye, and place the mouse on a heating plate to wake up.</li>
	<li>After the last acquisition, close the software and switch off the computer and the OCT machine (power supply button).</li>
	<li>Clean the cassette with disinfectant.</li>
</ol>
6. Analysis
<ol>
	<li>For the retinal layer thickness measurement, use the automated segmentation software provided by the manufacturer.
	<ol>
		<li>Click on the &#34;Patient&#34;, choose the desired &#34;Exam&#34; from then list, and click on the &#34;Review Exam&#34; option.</li>
		<li>Load the desired OCT data onto the OCT software by right-clicking on the folder icon in the desired scan.</li>
		<li>Right click on the B-scan; configure the calipers by enabling up to 10 measuring calipers; and enter their names, angles, and colors.</li>
		<li>Choosing the desired caliper by a right-clicking on the B-scan; place it accordingly onto the retina for measurement. 
		NOTE: For the scans centered on the ONH, set 5 calipers on each side of it, equidistant from each other. For the peripapillary analysis, make sure that the caliper is not placed too far from the ONH. For radial scanning, analyze 10 pictures per scan that were chosen by the OCT software. Their numbers may be found in the &#34;Reports&#34; folder.</li>
		<li>Save the results for analysis in a spreadsheet software program by right-clicking on the B-scan and clicking &#34;Save results&#34;. 
		NOTE: The results can be found in the same folder as the scanning data.</li>
	</ol>
	</li>
	<li>Alternatively, use the homemade caliper macro, &#34;MRI Retina Tool&#34;, developed for an open-source image processing program (see the Table of Materials).
	<ol>
		<li>Make sure that the &#34;MRI Retina Tool&#34; and the &#34;Modify Polygon Section Tool&#34; macros are active. Load the image. Click on the m button to start the measurement. 
		NOTE: The macro automatically creates one 0.2 mm-long measuring cassette on both sides of the ONH. Each cassette contains 5 measuring points that function as calipers. Their lateral position is unchangeable and is customized for the peripapilla in the radial scans. The horizontal position of the cassettes is predefined to measure the RNFL/GCL thickness, but it is easily modifiable to measure the GC complex layer instead. If the scan quality is poor, the horizontal position needs to be adjusted, or the picture needs to be excluded from the analysis.</li>
		<li>For horizontal adjustment, click on the e button. In the newly opened &#34;ROI Manager&#34; window, choose the first cassette.</li>
		<li>Click on the blue polygon button and adjust the position of the first cassette by clicking on the borders of the measured layer in the picture.</li>
		<li>Repeat for the second cassette by first choosing it in the &#34;ROI Manager&#34; window and then clicking on the appropriate image. Click on the r button to re-measure. View the results in the &#34;Measurements&#34; window. 
		NOTE: The results may be copied to a spreadsheet software program at any time. They contain the following values for the right cassette (r), left cassette (l), and total: Intden - integrated density within the cassette; Area: area of the measurement, in mm2; Len: length of the caliper within the cassette, in mm; Mean: mean intensity of the signal within the cassette; and Std: standard error of the mean intensity of the signal.</li>
		<li>Proceed with the next image.</li>
		<li>Further analyze the data in a spreadsheet software program. 
		NOTE: To find the mean thickness of the layer, take the ten Len values.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Drexler, W., Fujimoto, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=State-of-the-art+retinal+optical+coherence+tomography.">State-of-the-art retinal optical coherence tomography.</a> Prog Retin Eye Res. 27 (1), 45-88 (2008).</li><li>Grenier, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=WFS1+in+Optic+Neuropathies:+Mutation+Findings+in+Nonsyndromic+Optic+Atrophy+and+Assessment+of+Clinical+Severity.">WFS1 in Optic Neuropathies: Mutation Findings in Nonsyndromic Optic Atrophy and Assessment of Clinical Severity.</a> Ophthalmology. 123 (9), 1989-1998 (2016).</li><li>Zmyslowska, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+thinning+as+a+marker+of+disease+progression+in+patients+with+Wolfram+syndrome.">Retinal thinning as a marker of disease progression in patients with Wolfram syndrome.</a> Diabetes Care. 38 (3), e36-e37 (2015).</li><li>Fischer, M. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive,+in+vivo+assessment+of+mouse+retinal+structure+using+optical+coherence+tomography.">Noninvasive, in vivo assessment of mouse retinal structure using optical coherence tomography.</a> PLoS One. 4 (10), e7507 (2009).</li><li>Grieve, K., Thouvenin, O., Sengupta, A., Borderie, V. M., Paques, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Appearance+of+the+Retina+With+Full-Field+Optical+Coherence+Tomography.">Appearance of the Retina With Full-Field Optical Coherence Tomography.</a> Invest Ophthalmol Vis Sci. 57 (9), OCT96-OCT104 (2016).</li><li>Chang, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+degeneration+mutants+in+the+mouse.">Retinal degeneration mutants in the mouse.</a> Vision Res. 42 (4), 517-525 (2002).</li><li>Mustafa, S., Pandit, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Approach+to+diagnosis+and+management+of+optic+neuropathy.">Approach to diagnosis and management of optic neuropathy.</a> Neurol India. 62 (6), 599-605 (2014).</li><li>Sarzi, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+human+OPA1delTTAG+mutation+induces+premature+age-related+systemic+neurodegeneration+in+mouse.">The human OPA1delTTAG mutation induces premature age-related systemic neurodegeneration in mouse.</a> Brain. 135 (Pt 12), 3599-3613 (2012).</li><li>Sarzi, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+steroidogenesis+promotes+early-onset+and+severe+vision+loss+in+females+with+OPA1+dominant+optic+atrophy.">Increased steroidogenesis promotes early-onset and severe vision loss in females with OPA1 dominant optic atrophy.</a> Hum Mol Genet. 25 (12), 2539-2551 (2016).</li><li>Delettre-Cribaillet, C., Hamel, C. P., Lenaers, G., Pagon, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optic+Atrophy+Type+1.">Optic Atrophy Type 1.</a> Gene Reviews. 7 (2007), (2007).</li><li>Lenaers, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dominant+optic+atrophy.">Dominant optic atrophy.</a> Orphanet J Rare Dis. 7 (46), (2012).</li><li>Delettre, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+gene+OPA1,+encoding+a+mitochondrial+dynamin-related+protein,+is+mutated+in+dominant+optic+atrophy.">Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy.</a> Nat Genet. 26 (2), 207-210 (2000).</li><li>Liu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+retinal+morphologic+and+functional+changes+in+mice+following+optic+nerve+crush.">Monitoring retinal morphologic and functional changes in mice following optic nerve crush.</a> Invest Ophthalmol Vis Sci. 55 (6), 3766-3774 (2014).</li></ol>

The authors have nothing to disclose.

The OCT system, a non-invasive in vivo imaging method, provides high-resolution retinal cross-section-like scans. Thus, its main advantage is its potential for detailed analysis, with the wonderful opportunity to transpose protocols routinely applied to humans to mouse models.
In the example of Opa1delTTAG mutant mice, SD-OCT results showed an increase of RNFL and GC complex layer thickness, which allowed for further exploration of DOA pathophysiology<sup class="xr...

OCT is a diagnostic tool that facilitates the examination of retinal structures1, including the optic nerve head (ONH). Over the years it has become a dependable indicator of disease progression in humans2,3, as well as in rodents4,5. It uses interferometry to create cross-sectional images of retinal layers at a 2-&#181;m axial resolution. The innermost layer is the retinal nerve fiber layer (RNFL), containing RGC axons, which is followed by the ganglion cell layer (GCL), containing mostly RGC bodies. Next is the inner plexiform layer (IPL), where RGC dendrites meet bipolar, horizontal, and amacrine cell axons. These, together with horizontal cells, form the inner nuclear layer (INL), and their protrusions connect with photoreceptor axons in the outer plexiform layer (OPL). This is followed by the outer nuclear layer (ONL), with photoreceptor cell bodies, and is separated from the photoreceptor layer by the outer limiting membrane (OLM), also called the inner segment/outer segment (IS/OS) layer. Finally, the last observable layers in the mouse retina are the retinal pigment epithelium (RPE) and the choroid (C). The RNFL alone is normally too thin to be measured in mice; thus, analyzing the RNFL/GCL instead is preferable4,5. Another possibility is the GC complex layer, which contains the latter in addition to the IPL, making it thicker and thus even easier to measure on OCT scans4. Consequently, OCT can provide insight into the pathological status of the retina, such as in OPNs. 
Alternatively, the thickness of the mouse retina is often analyzed with post mortem histology. However, this technique faces limitations relating to tissue collection, fixation, cutting, staining, mounting, etc. Hence, some defects, such as subtle thickness changes, cannot be detected. Finally, because the same mouse cannot be tested at several time points, the number of animals per study greatly increases, unlike for OCT. All in all, the non-invasiveness, high-resolution, possibility for repetition, time monitoring in time, and ease of use of the OCT technology make it the method of choice in retinal disease studies.
Mouse models are used to identify gene defects and to elucidate molecular mechanisms underlying retinopathies6. OPN is a form of retinopathy with substantial damage to the optic nerve (ON), which is made up of approximately 1.2 million RGC axons. OPN can be focused on the ON or can be secondary to other disorders, inborn or not7, leading to visual field loss and later, blindness. Characteristic traits of OPN are RGC loss and ON damage, which can be observed in human OCT as RNFL and GCL thinning2,3. Meanwhile, the pathophysiology of OPN is still poorly understood, and hence the need to test mouse retinas remains. 
This manuscript describes the imaging and quantification of retinal layer thickness, using the example of the Opa1delTTAG mouse line8,9, a model of dominant optic atrophy (DOA)10. To assess RGC pathophysiology, radial, rectangular, and annular scans were quantified. This was done either with standard calipers provided by the OCT software or with a homemade macro developed for an open-source image processing program. The standard calipers are difficult to manipulate and often thicker than the RNFL/GCL, while the homemade calipers are easy to use, reproducible, and more precise. The macro performs a measurement for an automatically detected layer, in 5 points and at fixed positions, on both sides of the ONH in the peripapillary region. The goal of the presented protocol is to describe OCT scan acquisition to specify retinal positioning, with a focus on RGCs.

<table border="0" cellpadding="0" cellspacing="0" width="1619">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">Mice</td>
			<td style="width:324px;"></td>
			<td style="width:91px;"></td>
			<td style="width:909px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Opa1delTTAG mouse</td>
			<td style="width:324px;">Institute for Neurosciences in Montpellier, INSERM UMR 1051, France</td>
			<td style="width:91px;">-</td>
			<td>Opa1 knock-in mice carrying&#160; OPA1 c.2708_2711delTTAG mutation on C57Bl6/J background</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:296px;">Name</td>
			<td style="width:324px;">Company</td>
			<td style="width:91px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Equipment</td>
			<td style="width:324px;"></td>
			<td style="width:91px;"></td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">EnVisu R2200 SD-OCT Imaging System</td>
			<td style="width:324px;">Bioptigen, Leica Microsystems, Germany</td>
			<td style="width:91px;">-</td>
			<td>Spectral-Domain Optic Coherence Tomography system</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">EnVisu R2200 SD-OCT Imaging System Software</td>
			<td style="width:324px;">Bioptigen, Leica Microsystems, Germany</td>
			<td style="width:91px;">-</td>
			<td>Software for OCT acquisition and analysis</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">ImageJ 1.48v</td>
			<td style="width:324px;">Wayne Rasband, National Institutes of Health, USA</td>
			<td style="width:91px;">-</td>
			<td>Software for analysis, requires downloading and installing two hommade macros: http://dev.mri.cnrs.fr/projects/imagej-macros/wiki/Retina_Tool</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">Self-regulating heating plate</td>
			<td style="width:324px;">Bioseb, France</td>
			<td>BIO-062</td>
			<td>Protection against hypothermia</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:296px;">Name</td>
			<td style="width:324px;">Company</td>
			<td style="width:91px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Supplies</td>
			<td style="width:324px;"></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Nose Band</td>
			<td style="width:324px;">-</td>
			<td style="width:91px;">-</td>
			<td>Elastic band</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">Gauze pads 3&#34;x3&#34;</td>
			<td style="width:324px;">Curad, USA</td>
			<td>CUR20434ERB</td>
			<td>Protection against hypothermia</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">Dual Ended Cotton tip applicator</td>
			<td style="width:324px;">Essence of Beauty, CVS Health Corporation, USA</td>
			<td style="width:91px;">-</td>
			<td>Gel application</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">Cotton Twists</td>
			<td style="width:324px;">CentraVet, France</td>
			<td style="width:91px;">T.7979C.CS</td>
			<td>Mouse positioning</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:296px;">Name</td>
			<td style="width:324px;">Company</td>
			<td style="width:91px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Reagents and Drugs</td>
			<td style="width:324px;"></td>
			<td style="width:91px;"></td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:296px;">N&#233;osyn&#233;phrine Faure 10%</td>
			<td style="width:324px;">Laboratoires Europhtha, Monaco</td>
			<td style="width:91px;">-</td>
			<td>Eye dilatation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">Mydriaticum 0.5%</td>
			<td style="width:324px;">Laboratoires Th&#233;a, France</td>
			<td style="width:91px;">3397908</td>
			<td>Eye dilatation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">Cebesine 0.4%</td>
			<td style="width:324px;">Laboratoire Chauvin, Bausch&#38;Lomb, France</td>
			<td style="width:91px;">3192342</td>
			<td>Local anesthesia</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">Imalgene 1000</td>
			<td style="width:324px;">Merial, France/CentraVet, France</td>
			<td style="width:91px;">IMA004</td>
			<td>General anesthesia</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">Rompun</td>
			<td>Bayer Healthcare, Germany/CentraVet, France</td>
			<td style="width:91px;">ROM001</td>
			<td>General anesthesia, analgesia, muscle relaxation</td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:296px;">NaCl 0,9%</td>
			<td style="width:324px;">Laboratoire Osalia, France&#160;</td>
			<td style="width:91px;">103697114</td>
			<td>Physiological serum</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">Systene Ultra</td>
			<td style="width:324px;">Alcon, Novartis, USA</td>
			<td style="width:91px;">-</td>
			<td>Hydration of eyes</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">GenTeal&#39;</td>
			<td style="width:324px;">Alcon, Novartis, USA</td>
			<td style="width:91px;">-</td>
			<td>Ophtalmic gel to minimize light refraction and opacities</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:296px;">Aniospray Surf 29</td>
			<td style="width:324px;">Laboratoires Anios, France</td>
			<td>59844</td>
			<td>Desinfectant</td>
		</tr>
	</tbody>
</table>

optical coherence tomography: imaging mouse retinal ganglion cells in vivo

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in vivo&#8212;rapidly, repetitively, and at a high resolution. This protocol describes OCT imaging in the mouse retina as a powerful tool to study optic neuropathies (OPN). The OCT system is an interferometry-based, non-invasive alternative to common post mortem histological assays. It provides a fast and accurate assessment of retinal thickness, allowing the possibility to track changes, such as retinal thinning or thickening. We present the imaging process and analysis with the example of the Opa1delTTAG mouse line. Three types of scans are proposed, with two quantification methods: standard and homemade calipers. The latter is best for use on the peripapillary retina during radial scans; being more precise, is preferable for analyzing thinner structures. All approaches described here are designed for retinal ganglion cells (RGC) but are easily adaptable to other cell populations. In conclusion, OCT is efficient in mouse model phenotyping and has the potential to be used for the reliable evaluation of therapeutic interventions.

The SD-OCT technology enables retinal imagining and thickness analysis that is comparable to histology, but is faster and more detailed (Figure 3). As presented with wildtype C57Bl/6 mice, even though the quality of an SD-OCT scan (Figure 3A, right) is not as good as that of an image of a retinal cross-section (Figure 3A, left), it visualizes more layers (e.g., OLM). Moreover, it takes only ...

Watch this Scientific Journal Video about Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo at JoVE.com

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

This manuscript describes a protocol for the in vivo imaging of the mouse retina with high-resolution spectral domain optical coherence tomography (SD-OCT). It focuses on retinal ganglion cells (RGC) in the peripapillary region, with several scanning and quantifying approaches described.

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

Structural changes in the retina are common manifestations of ophthalmic diseases. Optical coherence tomography (OCT) enables their identification in ...

optical-coherence-tomography-imaging-mouse-retinal-ganglion-cells

Research

JoVE Journal

Neuroscience

19.1K Views.  INSERM U1051, Institut of Neurosciences of Montpellier. This manuscript describes a protocol for the in vivo imaging of the mouse retina with high-resolution spectral domain optical coherence tomography (SD-OCT). It focuses on retinal ganglion cells (RGC) in the peripapillary region, with several scanning and quantifying approaches described.

Video: Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

An Isolated Retinal Preparation to Record Light Response from Genetically Labeled Retinal Ganglion Cells

The first steps in vertebrate vision take place when light stimulates the rod and cone photoreceptors of the retina 1. This information is then segregated into what are known as the ON and OFF pathways. The photoreceptors signal light information to the bipolar cells (BCs), which depolarize in response to increases (On BCs) or decreases (Off BCs) in light intensity. This segregation of light information is maintained at the level of the retinal ganglion cells (RGCs), which have dendrites stratifying in either the Off sublamina of the inner plexiform layer (IPL), where they receive direct excitatory input from Off BCs, or stratifying in the On sublamina of the IPL, where they receive direct excitatory input from On BCs. This segregation of information regarding increases or decreases in illumination (the On and Off pathways) is conserved and signaled to the brain in parallel.
The RGCs are the output cells of the retina, and are thus an important cell to study in order to understand how light information is signaled to visual nuclei in the brain. Advances in mouse genetics over recent decades have resulted in a variety of fluorescent reporter mouse lines where specific RGC populations are labeled with a fluorescent protein to allow for identification of RGC subtypes 2 3 4 and specific targeting for electrophysiological recording. Here, we present a method for recording light responses from fluorescently labeled ganglion cells in an intact, isolated retinal preparation. This isolated retinal preparation allows for recordings from RGCs where the dendritic arbor is intact and the inputs across the entire RGC dendritic arbor are preserved. This method is applicable across a variety of ganglion cell subtypes and is amenable to a wide variety of single-cell physiological techniques.

This article provides a description of how to dissect and record from the isolated retinal preparation in mouse. In particular, we describe how to record light responses from a fluorescently labeled ganglion cell population and subsequently identify and analyze its morphology.

The first steps in vertebrate vision take place when light stimulates the rod and cone photoreceptors of the retina 1.  This information is then ...

Optical Imaging of Neurons in the Crab Stomatogastric Ganglion with Voltage-sensitive Dyes

Voltage-sensitive dye imaging of neurons is a key methodology for the understanding of how neuronal networks are organised and how the simultaneous activity of participating neurons leads to the emergence of the integral functionality of the network. Here we present the methodology of application of this technique to identified pattern generating neurons in the crab stomatogastric ganglion. We demonstrate the loading of these neurons with the fluorescent voltage-sensitive dye Di-8-ANEPPQ and we show how to image the activity of dye loaded neurons using the MiCAM02 high speed and high resolution CCD camera imaging system. We demonstrate the analysis of the recorded imaging data using the BVAna imaging software associated with the MiCAM02 imaging system. The simultaneous voltage-sensitive dye imaging of the detailed activity of multiple neurons in the crab stomatogastric ganglion applied together with traditional electrophysiology techniques (intracellular and extracellular recordings) opens radically new opportunities for the understanding of how central pattern generator neural networks work.

Here we present the methodology for fast and high resolution fluorescent voltage-sensitive dye imaging of detailed activity of neurons in the crab stomatogastric ganglion.

Voltage-sensitive dye imaging of neurons is a key methodology for the understanding of how neuronal networks are organised and how the simultaneous ...

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural connectivity form during development. In mice, retinofugal projections are arranged in a topographic manner and form eye-specific layers in the Lateral Geniculate Nucleus (dLGN) of the thalamus and the Superior Colliculus (SC). The development of these precise patterns of retinofugal projections has typically been studied by labeling populations of RGCs with fluorescent dyes and tracers, such as horseradish peroxidase1-4. However, these methods are too coarse to provide insight into developmental changes in individual RGC axonal arbor morphology that are the basis of retinotopic map formation. They also do not allow for the genetic manipulation of RGCs.
Recently, electroporation has become an effective method for providing precise spatial and temporal control for delivery of charged molecules into the retina5-11. Current retinal electroporation protocols do not allow for genetic manipulation and tracing of retinofugal projections of a single or small cluster of RGCs in postnatal mice. It has been argued that postnatal in vivo electroporation is not a viable method for transfecting RGCs since the labeling efficiency is extremely low and hence requires targeting at embryonic ages when RGC progenitors are undergoing differentiation and proliferation6. 
In this video we describe an in vivo electroporation protocol for targeted delivery of genes, shRNA, and fluorescent dextrans to murine RGCs postnatally. This technique provides a cost effective, fast and relatively easy platform for efficient screening of candidate genes involved in several aspects of neural development including axon retraction, branching, lamination, regeneration and synapse formation at various stages of circuit development. In summary we describe here a valuable tool which will provide further insights into the molecular mechanisms underlying sensory map development.

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

We demonstrate an in vivo electroporation protocol for transfecting single or small clusters of retinal ganglion cells (RGCs) and other retinal cell types in postnatal mice over a wide range of ages. The ability to label and genetically manipulate postnatal RGCs in vivo is a powerful tool for developmental studies.

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural ...

Thinned-skull Cortical Window Technique for In Vivo Optical Coherence Tomography Imaging

Optical coherence tomography (OCT) is a biomedical imaging technique with high spatial-temporal resolution. With its minimally invasive approach OCT has been used extensively in ophthalmology, dermatology, and gastroenterology1-3. Using a thinned-skull cortical window (TSCW), we employ spectral-domain OCT (SD-OCT) modality as a tool to image the cortex in vivo. Commonly, an opened-skull has been used for neuro-imaging as it provides more versatility, however, a TSCW approach is less invasive and is an effective mean for long term imaging in neuropathology studies. Here, we present a method of creating a TSCW in a mouse model for in vivo OCT imaging of the cerebral cortex.

Thinned-skull Cortical Window Technique for In Vivo Optical Coherence Tomography Imaging

We present a method of creating a thinned-skull cortical window (TSCW) in a mouse model for in vivo OCT imaging of the cerebral cortex.

Optical coherence tomography (OCT) is a biomedical imaging technique  with high spatial-temporal resolution. With its minimally invasive approach OCT  has ...

Implementing Dynamic Clamp with Synaptic and Artificial Conductances in Mouse Retinal Ganglion Cells

Ganglion cells are the output neurons of the retina and their activity reflects the integration of multiple synaptic inputs arising from specific neural circuits. Patch clamp techniques, in voltage clamp and current clamp configurations, are commonly used to study the physiological properties of neurons and to characterize their synaptic inputs. Although the application of these techniques is highly informative, they pose various limitations. For example, it is difficult to quantify how the precise interactions of excitatory and inhibitory inputs determine response output. To address this issue, we used a modified current clamp technique, dynamic clamp, also called conductance clamp 1, 2, 3 and examined the impact of excitatory and inhibitory synaptic inputs on neuronal excitability. This technique requires the injection of current into the cell and is dependent on the real-time feedback of its membrane potential at that time. The injected current is calculated from predetermined excitatory and inhibitory synaptic conductances, their reversal potentials and the cell's instantaneous membrane potential. Details on the experimental procedures, patch clamping cells to achieve a whole-cell configuration and employment of the dynamic clamp technique are illustrated in this video article. Here, we show the responses of mouse retinal ganglion cells to various conductance waveforms obtained from physiological experiments in control conditions or in the presence of drugs. Furthermore, we show the use of artificial excitatory and inhibitory conductances generated using alpha functions to investigate the responses of the cells.

This video article illustrates the set-up, the procedures to patch cell bodies and how to implement dynamic clamp recordings from ganglion cells in whole-mount mouse retinae. This technique allows the investigation of the precise contribution of excitatory and inhibitory synaptic inputs, and their relative magnitude and timing to neuronal spiking.

Ganglion cells are the output neurons of the  retina and their activity reflects the integration of multiple synaptic inputs  arising from specific neural ...

Retrograde Labeling of Retinal Ganglion Cells in Adult Zebrafish with Fluorescent Dyes

As retrograde labeling retinal ganglion cells (RGCs) can isolate RGCs somata from dying sites, it has become the gold standard for counting RGCs in RGCs survival and regeneration experiments. Many studies have been performed in mammalian animals to research RGCs survival after optic nerve injury. However, retrograde labeling of RGCs in adult zebrafish has not yet been reported, though some alternative methods can count cell numbers in retinal ganglion cell layers (RGCL). Considering the small size of the adult zebrafish skull and the high risk of death after drilling on the skull, we open the skull with the help of acid-etching and seal the hole with a light curing bond, which could significantly improve the survival rate. After absorbing the dyes for 5 days, almost all the RGCs are labeled. As this method does not need to transect the optic nerve, it is irreplaceable in the research of RGCs survival after optic nerve crush in adult zebrafish. Here, we introduce this method step by step and provide representative results.

We introduce an efficient method to retrograde label retinal ganglion cells (RGCs) in adult zebrafish.

As retrograde labeling retinal ganglion cells (RGCs) can isolate RGCs somata from dying sites, it has become the gold standard for counting RGCs in RGCs ...

Single-cell RNA-Seq of Defined Subsets of Retinal Ganglion Cells

The discovery of cell type-specific markers can provide insight into cellular function and the origins of cellular heterogeneity. With a recent push for the improved understanding of neuronal diversity, it is important to identify genes whose expression defines various subpopulations of cells. The retina serves as an excellent model for the study of central nervous system diversity, as it is composed of multiple major cell types. The study of each major class of cells has yielded genetic markers that facilitate the identification of these populations. However, multiple subtypes of cells exist within each of these major retinal cell classes, and few of these subtypes have known genetic markers, although many have been characterized by morphology or function. A knowledge of genetic markers for individual retinal subtypes would allow for the study and mapping of brain targets related to specific visual functions and may also lend insight into the gene networks that maintain cellular diversity. Current avenues used to identify the genetic markers of subtypes possess drawbacks, such as the classification of cell types following sequencing. This presents a challenge for data analysis and requires rigorous validation methods to ensure that clusters contain cells of the same function. We propose a technique for identifying the morphology and functionality of a cell prior to isolation and sequencing, which will allow for the easier identification of subtype-specific markers. This technique may be extended to non-neuronal cell types, as well as to rare populations of cells with minor variations. This protocol yields excellent-quality data, as many of the libraries have provided read depths greater than 20 million reads for single cells. This methodology overcomes many of the hurdles presented by Single-cell RNA-Seq and may be suitable for researchers aiming to profile cell types in a straightforward and highly efficient manner.

Here, we present a combinatorial approach for classifying neuronal cell types prior to isolation and for the subsequent characterization of single-cell transcriptomes. This protocol optimizes the preparation of samples for successful RNA Sequencing (RNA-Seq) and describes a methodology designed specifically for the enhanced understanding of cellular diversity.

The discovery of cell type-specific markers can provide insight into cellular function and the origins of cellular heterogeneity. With a recent push for ...

Using Optical Coherence Tomography and Optokinetic Response As Structural and Functional Visual System Readouts in Mice and Rats

Optical coherence tomography (OCT) is a fast, non-invasive, interferometric technique allowing high-resolution retinal imaging. It is an ideal tool for the investigation of processes of neurodegeneration, neuroprotection and neuro-repair involving the visual system, as these often correlate well with retinal changes. As a functional readout, visually evoked compensatory eye and head movements are commonly used in experimental models involving the visual function. Combining both techniques allows a quantitative in vivo investigation of structure and function, which can be used to investigate the pathological conditions or to evaluate the potential of novel therapeutics. A great benefit of the presented techniques is the possibility to perform longitudinal analyses allowing the investigation of dynamic processes, reducing variability and cuts down the number of animals needed for the experiments. The protocol described aims to provide a manual for acquisition and analysis of high quality retinal scans of mice and rats using a low cost customized holder with an option to deliver inhalational anesthesia. Additionally, the proposed guide is intended as an instructional manual for researchers using optokinetic response (OKR) analysis in rodents, which can be adapted to their specific needs and interests.

A detailed protocol for the assessment of structural and visual readouts in rodents by optical coherence tomography and optokinetic response is presented. The results provide valuable insights for ophthalmologic as well as neurologic research.

Optical coherence tomography (OCT) is a fast, non-invasive, interferometric technique allowing high-resolution retinal imaging. It is an ideal tool for ...

Retinal Vascular Reactivity as Assessed by Optical Coherence Tomography Angiography

The vascular supply to the retina has been shown to dynamically adapt through vasoconstriction and vasodilation to accommodate the metabolic demands of the retina. This process, referred to as retinal vascular reactivity (RVR), is mediated by neurovascular coupling, which is impaired very early in retinal vascular diseases such as diabetic retinopathy. Therefore, a clinically feasible method of assessing vascular function may be of significant interest in both research and clinical settings. Recently, in vivo imaging of the retinal vasculature at the capillary level has been made possible by the FDA approval of optical coherence tomography angiography (OCTA), a noninvasive, minimal risk and dyeless angiography method with capillary level resolution. Concurrently, physiological and pathological changes in RVR have been shown by several investigators. The method shown in this manuscript is designed to investigate RVR using OCTA with no need for alterations to the clinical imaging procedures or device. It demonstrates real time imaging of the retina and retinal vasculature during exposure to hypercapnic or hyperoxic conditions. The exam is easily performed with two personnel in under 30 min with minimal subject discomfort or risk. This method is adaptable to other ophthalmic imaging devices and the applications may vary based on the composition of the gas mixture and patient population. A strength of this method is that it allows for an investigation of retinal vascular function at the capillary level in human subjects in vivo. Limitations of this method are largely those of OCTA and other retinal imaging methods including imaging artifacts and a restricted dynamic range. The results obtained from the method are OCT and OCTA images of the retina. These images are amenable to any analysis that is possible on commercially available OCT or OCTA devices. The general method, however, can be adapted to any form of ophthalmic imaging.

This article describes a method for measuring retinal vasculature reactivity in vivo with human subjects using a gas breathing provocation technique to deliver vasoactive stimuli while acquiring retinal images.

The vascular supply to the retina has been shown to dynamically adapt through vasoconstriction and vasodilation to accommodate the metabolic demands of ...

In vivo Calcium Imaging of Mouse Geniculate Ganglion Neuron Responses to Taste Stimuli

Within the last ten years, advances in genetically encoded calcium indicators (GECIs) have promoted a revolution in in vivo functional imaging. Using calcium as a proxy for neuronal activity, these techniques provide a way to monitor the responses of individual cells within large neuronal ensembles to a variety of stimuli in real time. We, and others, have applied these techniques to image the responses of individual geniculate ganglion neurons to taste stimuli applied to the tongues of live anesthetized mice. The geniculate ganglion is comprised of the cell bodies of gustatory neurons innervating the anterior tongue and palate as well as some somatosensory neurons innervating the pinna of the ear. Imaging the taste-evoked responses of individual geniculate ganglion neurons with GCaMP has provided important information about the tuning profiles of these neurons in wild-type mice as well as a way to detect peripheral taste miswiring phenotypes in genetically manipulated mice. Here we demonstrate the surgical procedure to expose the geniculate ganglion, GCaMP fluorescence image acquisition, initial steps for data analysis, and troubleshooting. This technique can be used with transgenically encoded GCaMP, or with AAV-mediated GCaMP expression, and can be modified to image particular genetic subsets of interest (i.e., Cre-mediated GCaMP expression). Overall, in vivo calcium imaging of geniculate ganglion neurons is a powerful technique for monitoring the activity of peripheral gustatory neurons and provides complementary information to more traditional whole-nerve chorda tympani recordings or taste behavior assays.

Here we present how to expose the geniculate ganglion of a live, anesthetized laboratory mouse and how to use calcium imaging to measure the responses of ensembles of these neurons to taste stimuli, allowing for multiple trials with different stimulants. This allows for in depth comparisons of which neurons respond to which tastants.

Within the last ten years, advances in genetically encoded calcium indicators (GECIs) have promoted a revolution in in vivo functional imaging. Using ...