This work was supported by the Department of Veterans Affairs Rehab R&#38;D Service Career Development Awards (CDA-1, RX002111; CDA-2; RX002928) to RSA and (CDA-2, RX002342) to AJF and the National Institutes of Health (NIH-NICHD F31 HD097918 to DACT and NIH-NIEHS T32 ES012870 to DACT) and NEI Core Grant P30EY006360.

All procedures were approved by the Atlanta Veterans Affairs Institutional Animal Care and Use Committee and conformed to the National Institutes of Health guide for the care and use of laboratory animals (NIH Publications, 8th edition, updated 2011).
1. The optomotor response (OMR)
<ol>
	<li>Set up the OMR apparatus (details on apparatus and software in Table of Materials)
	<ol>
		<li>Choose the appropriate-sized platform for the rodent: mouse, rat, or large/impaired rat (Figure 1A).</li>
		<li>Open the OMR software, which should open to a window with several tabs of options and a live video feed of the inside of the OMR/virtual drum (Figure 1B). Zoom in or out with the video camera as needed so that the platform and its surroundings are visible.</li>
		<li>Note the icons along the left-hand side of the live image (Figure 1C). Click on the asterisk icon and the rotating stripes icon so that both the green asterisk and green rotating stripes disappear from the live feed.</li>
		<li>Click on the compass icon so that a green circle and two perpendicular lines appear. Stretch the green circle so that it aligns perfectly with the black circle on the platform, which will ensure that the OMR is perfectly aligned.</li>
		<li>Click on the compass icon because it is not necessary to see the circle during testing. Click on the green asterisk icon and the green rotating stripes icon to make these reappear. Note that the green stripes rotate in the same direction as the stripes in the drum, allowing the researcher to know the direction of the stripes.</li>
		<li>Click on the Testing tab. Under Testing, click on the Psychophysics tab. Under Threshold, select Frequency to measure spatial frequency. 
		NOTE: The OMR software uses a staircase paradigm to automatically calculate spatial frequency (SF). Contrast will be maintained at 100%.</li>
		<li>Under Testing, click on the Presets tab. Select the default settings for Mouse18 or Rat20.</li>
		<li>Under Testing, click on the Blanking tab. Check the Blank on Tracking box, which will pause the stripes/blank out the computer screens in the drum whenever the mouse is right-clicked.</li>
		<li>Click on the Results tab, which is where the results of the test will be displayed.</li>
	</ol>
	</li>
	<li>Evaluate spatial frequency
	<ol>
		<li>Place the rodent on the circular platform in the center of the virtual reality chamber comprising four computer monitors showing vertical sine wave gratings circling the chamber at a velocity of 12&#730;/s (Figure 1D).</li>
		<li>Note that the video camera positioned at the top of the chamber is projecting the rodent&#8217;s behavior live onto the computer monitor.</li>
		<li>Look for the presence or absence of reflexive actions by the rodent&#8217;s head as the gratings move in a clockwise or counterclockwise direction. Make sure illustrated bars are visible in the program&#8212;these will show the direction of the grating movement.
		<ol>
			<li>Watch for the rodent&#8217;s head to move in the same direction as the gratings. Wait until there is a smooth pursuit, not erratic bursts of head motion, to count it as tracking.</li>
			<li>Click on Yes or No as appropriate. Note that SF will start with 0.042 cyc/deg and adjust with each yes and no to become easier or more difficult (Figure 1E). Click on Reset if the test needs to be reset due to accidental or incorrect clicking of yes and no.</li>
		</ol>
		</li>
		<li>As the rodent is tested, make sure to keep the asterisk positioned over the rodent&#8217;s head. 
		NOTE: This has two effects: 1) It maintains the correct spatial frequency. If the asterisk is positioned between the shoulders, for example, the spatial frequency will be lower and the bars will be easier to see, resulting in a falsely high score. 2) For rodents with slight head movements, the asterisk makes it easier to gauge whether the head is actually moving.</li>
		<li>Watch for the system to say &#8220;Done&#8221; when the rodent&#8217;s spatial frequency is reached. Note that the Yes and No buttons will no longer be clickable.</li>
		<li>Click on the Results tab, which will display the spatial frequency for the left eye, right eye, and combined eyes. 
		NOTE: Sometimes the software is set such that the results are flipped, i.e., the right eye is reported as the left eye and the left eye is reported as the right eye. This was discovered when assessing rodents that had only one eye lesioned in a glaucoma model.</li>
	</ol>
	</li>
	<li>Evaluate contrast sensitivity 
	NOTE: Contrast Sensitivity testing can be performed immediately after the spatial frequency measurement step or on its own on the same day or a different day if the rodent appears fatigued after spatial frequency testing (follow steps 1&#8211;2.2 if only testing contrast sensitivity).
	<ol>
		<li>Click on the Testing tab and then on the Psychophysics tab. Under Threshold, select Contrast (single) to measure contrast sensitivity.</li>
		<li>Also using a staircase paradigm, start gratings with SF constant at the peak of the Contrast Sensitivity (CS) curve. To do this, click on the Stimulus tab and then on the Gratings tab. In the Spatial Frequency box, type 0.064 for rats and 0.103 for mice.</li>
		<li>Begin the contrast at 100% and look for the same reflexive head movements as seen during spatial frequency testing. Note that the contrast will decrease as the testing progresses until the rodent no longer has reflexive head movements in response to the stimulus (Figure 1E).</li>
		<li>Watch for the system to say &#8220;Done&#8221; and the Yes and No buttons to no longer be clickable once the rodent no longer responds to the visual stimulus and the contrast sensitivity threshold has been reached. Click on the Results tab, where the contrast sensitivity for the left eye, right eye, and combined eyes will be listed.</li>
	</ol>
	</li>
	<li>Perform post-testing analysis
	<ol>
		<li>For diabetic retinopathy studies, where both eyes are expected to have similar deficits, use the combined score (average of right and left eyes) for analysis. For models that cause differential damage to eyes (i.e., blast injury or glaucoma), keep the left and right eye data separate.</li>
		<li>For Spatial Frequency, use raw scores (the data from the Results tab) for analysis and average these scores together by group (i.e., diabetic, control, etc.).</li>
		<li>For Contrast Sensitivity, use the raw value to calculate the reported contrast sensitivity by the Michelson contrast from a previous measurement of the screen&#8217;s luminance.</li>
	</ol>
	</li>
</ol>
2. The Y-maze
<ol>
	<li>Prepare rodents for testing
	<ol>
		<li>Adapt rodents to the room for 30 min prior to testing. 
		NOTE: The researcher can remain in the room with the lights on but should remain silent during this time.</li>
		<li>Clean the Y-maze with sanitizing solution safe for animals and wipe away all sanitizing solution with paper towels. Ensure that the maze is dry.</li>
	</ol>
	</li>
	<li>Conduct the Y-maze
	<ol>
		<li>Label the initial arm of the Y-maze as B and the other 2 arms as A and C (Figure 2A). Place one rodent in the arm closest to the researcher (arm B) near the center of the Y-maze. Once the rodent has been placed, start the timer (details on maze and timer in Table of Materials).
		<ol>
			<li>Allow each rodent to explore the Y-maze for 8 min. Take recordings during this time and note any observations. Sit several feet away from the maze while keeping it in sight and avoid making any noise.</li>
			<li>Record the starting location as A, and each time the rodent makes an entry into a new arm, record the new location of the rodent (Figure 2B). Define an entry as all four limbs of the rodent being in one of the arms.</li>
			<li>Watch for rodents to hide and remain stationary in one arm of the maze. If the rodent remains in the same spot for more than 60 s and does not appear to show exploratory behavior, move the rodent toward the center of the Y-maze, and continue the trial.</li>
		</ol>
		</li>
		<li>After each rodent, remove any feces and clean the maze with sanitizing solution.
		<ol>
			<li>Ensure that all sanitizing solution is wiped away with paper towels and the maze is completely dry before placing the next rodent in the maze.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Calculate spontaneous alternation and exploratory behavior
	<ol>
		<li>Calculate exploratory behavior as the total number of entries made during 8 min.</li>
		<li>Calculate spatial cognition as measured by spontaneous alternation: 
		the number of successful alternations/(the total number of entries - 2)
		<ol>
			<li>Define a successful alternation as the rodent moves into three different locations sequentially (Example: ABC, CAB, BCA, etc.). Note each successful alternation (Figure 2B).</li>
			<li>If the movements were recorded as ACABCABABCABC, disregard the two initial starting locations when calculating spontaneous alternation (such that there are 11 movements in the denominator). Count the number of accurate movements (accurate movements = 8). Calculate the percent accuracy as: 8/(13 - 2) = 72.7%.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

The OMR and the Y-maze allow for the non-invasive assessment of visual function and cognitive function deficits in rodents over time. In this protocol, the OMR and the Y-maze were demonstrated to track visual and cognitive deficits in rodent models of diabetes.
Critical steps in the protocol
The OMR
Some important points to consider when performing the OMR to assess visual function are the testing parameters used, experim...

An erratum was issued for:&#160;<a href="https://www.jove.com/t/61806">Behavioral Assessment of Visual Function via Optomotor Response and Cognitive Function via Y-Maze in Diabetic Rats</a>. The author list was updated.
The author list was updated from:
Kaavya Gudapati*1,2, Anayesha Singh*1,3, Danielle Clarkson-Townsend1,4, Andrew J. Feola1,2, Rachael S. Allen1,2 
1Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Medical Center, 
2Department of Biomedical Engineering, Georgia Institute of Technology, 
3Department of Neuroscience, Emory University, 
4Gangarosa Department of Environmental Health, Emory University 
* These authors contributed equally
to:
Kaavya Gudapati*1,2, Anayesha Singh*1,3, Danielle Clarkson-Townsend1,4, Stephen Q. Phillips1, Amber Douglass1, Andrew J. Feola1,2, Rachael S. Allen1,2 
1Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Medical Center, 
2Department of Biomedical Engineering, Georgia Institute of Technology, 
3Department of Neuroscience, Emory University, 
4Gangarosa Department of Environmental Health, Emory University 
* These authors contributed equally

An erratum was issued for:&#160;<a href="https://www.jove.com/t/61806">Behavioral Assessment of Visual Function via Optomotor Response and Cognitive Function via Y-Maze in Diabetic Rats</a>. The author list was updated.

Erratum: Behavioral Assessment of Visual Function via Optomotor Response and Cognitive Function via Y-Maze in Diabetic Rats

Over 463 million people live with diabetes, making it one of the largest global disease epidemics1. One of the serious complications that arises from diabetes is diabetic retinopathy (DR), a leading cause of blindness for working-age American adults2. In the next 30 years, the percentage of the population at risk for DR is projected to double, so it is crucial to find new ways of diagnosing DR in its earlier stages to prevent and mitigate DR development3. DR has conventionally been thought to be a vascular disease4,5,6. However, now with evidence of neuronal dysfunction and apoptosis in the retina that precedes vascular pathology, DR is defined to have neuronal and vascular components4,5,6,7,8,9. One way to diagnose DR would be to examine neural abnormalities in the retina, a tissue that may be more vulnerable to oxidative stress and metabolic strain from diabetes than other neural tissue10.
Declines in cognitive and motor function also occur with diabetes and are often correlated with retinal changes. Older individuals with Type II diabetes portray worse baseline cognitive performance and show more exacerbated cognitive decline than control participants11. Additionally, the retina has been established as an extension of the central nervous system and pathologies can manifest in the retina12. Clinically, the relationship between retina and brain has been studied in the context of Alzheimer&#8217;s and other diseases but is not commonly explored with diabetes12,13,14,15,16. Changes in the brain and retina during the progression of diabetes can be explored using animal models, including the STZ rat (a model of Type I diabetes in which the toxin, streptozotocin or STZ, is used to damage pancreatic beta cells) and the Goto-Kakizaki rat (a polygenic model of Type II diabetes in which animals develop hyperglycemia spontaneously at around 3 weeks of age). In this protocol, a description for the Y-maze and the optomotor response to assess cognitive and visual changes in diabetic rodents, respectively, is provided. The optomotor response (OMR) assesses spatial frequency (similar to visual acuity) and contrast sensitivity by monitoring characteristic reflexive head tracking movements to gauge visual thresholds for each eye17. Spatial frequency refers to the thickness or fineness of the bars, and contrast sensitivity refers to how much contrast there is between the bars and the background (Figure 1E). Meanwhile, the Y-maze tests short-term spatial memory and exploratory function, observed through spontaneous alternations and entries through the arms of the maze.
Both tests can be performed in awake, non-anesthetized animals and have the advantage of capitalizing on innate responses of the animals, meaning that they do not require training. Both are relatively sensitive, in that they can be used to detect deficits early in the progression of diabetes in rodents, and reliable, in that they produce results that correlate with other visual, retinal, or behavioral tests. Additionally, using the OMR and the Y-maze in conjunction with tests such as electroretinogram and optical coherence tomography scans can provide information on when retinal, structural, and cognitive changes develop relative to each other in disease models. These investigations could be useful in identifying neural degenerations that occur due to diabetes. Ultimately, this could lead to new diagnostic methods that effectively identify DR in early stages of progression.
The OMR and the Y-maze systems used to develop this protocol are described in the Table of Materials. Previous research on the OMR, by Prusky et al.18, and the Y-maze, by Maurice et al.19, was used as the starting point to develop this protocol.

<table><tbody><tr><td>OptoMotry HD</td><td>CerebralMechanics Inc.</td><td></td><td>OMR apparatus &amp;amp; software</td></tr><tr><td>Timer</td><td>Thomas Scientific</td><td>810029AR</td><td></td></tr><tr><td>Y-Maze apparatus</td><td>San Diego Instruments</td><td>7001-043</td><td>Available specifically for rats</td></tr></tbody></table>

behavioral assessment of visual function via optomotor response and cognitive function via y-maze in diabetic rats

The optomotor response and the Y-maze are behavioral tests useful for assessing visual and cognitive function, respectively. The optomotor response is a valuable tool to track changes in spatial frequency (SF) and contrast sensitivity (CS) thresholds over time in a number of retinal disease models, including diabetic retinopathy. Similarly, the Y-maze can be used to monitor spatial cognition (as measured by spontaneous alternation) and exploratory behavior (as measured by a number of entries) in a number of disease models that affect the central nervous system. Advantages of the optomotor response and the Y-maze include sensitivity, speed of testing, the use of innate responses (training is not needed), and the ability to be performed on awake (non-anesthetized) animals. Here, protocols are described for both the optomotor response and the Y-maze and examples of their use shown in models of Type I and Type II diabetes. Methods include preparation of rodents and equipment, performance of the optomotor response and the Y-maze, and post-test data analysis.

The OMR is considered successful if spatial frequency and contrast sensitivity thresholds can be obtained from a rodent. Here, the use of the OMR to assess spatial frequency is illustrated in naïve control Brown-Norway and Long-Evans rats, both young (3–6 months) and aged (9–12 months). Brown-Norway rats typically show a higher baseline spatial frequency than Long-Evans rats. Additionally, an aging effect on spatial frequency was observed in the Long-Evans rats (Figure 3A). Data were an...

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Behavioral Assessment of Visual Function via Optomotor Response and Cognitive Function via Y-Maze in Diabetic Rats

Neural degeneration in both eyes and brain as a result of diabetes can be observed through behavioral tests carried out on rodents. The Y-maze, a measure of spatial cognition, and the optomotor response, a measure of visual function, both provide insight into potential diagnoses and treatments.

The optomotor response and the Y-maze are behavioral tests useful for assessing visual and cognitive function, respectively. The optomotor response is a ...

behavioral-assessment-visual-function-via-optomotor-response

Research

JoVE Journal

Behavior

5.6K Views.  Atlanta VA Medical Center. Neurale degeneratie in zowel ogen als hersenen als gevolg van diabetes kan worden waargenomen door gedragstests die worden uitgevoerd op knaagdieren. Het Y-doolhof, een maat voor ruimtelijke cognitie, en de optomotorische respons, een maat voor visuele functie, geven beide inzicht in mogelijke diagnoses en behandelingen.

Video: Behavioral Assessment of Visual Function via Optomotor Response and Cognitive Function via Y-Maze in Diabetic Rats

A Laser-induced Mouse Model of Chronic Ocular Hypertension to Characterize Visual Defects

Glaucoma, frequently associated with elevated intraocular pressure (IOP), is one of the leading causes of blindness. We sought to establish a mouse model of ocular hypertension to mimic human high-tension glaucoma. Here laser illumination is applied to the corneal limbus to photocoagulate the aqueous outflow, inducing angle closure. The changes of IOP are monitored using a rebound tonometer before and after the laser treatment. An optomotor behavioral test is used to measure corresponding changes in visual capacity. The representative result from one mouse which developed sustained IOP elevation after laser illumination is shown. A decreased visual acuity and contrast sensitivity is observed in this ocular hypertensive mouse. Together, our study introduces a valuable model system to investigate neuronal degeneration and the underlying molecular mechanisms in glaucomatous mice.

Chronic ocular hypertension is induced using laser photocoagulation of the trabecular meshwork in mouse eyes. The intraocular pressure (IOP) is elevated for several months after laser treatment. The decrease of visual acuity and contrast sensitivity of experimental animals are monitored using the optomotor test.

Glaucoma, frequently associated with elevated intraocular pressure (IOP), is one of the leading causes of blindness. We sought to establish a mouse model ...

Medicine

An Ultrasonic Tool for Nerve Conduction Block in Diabetic Rat Models

Nerve conduction block with a high intensity-focused ultrasound (HIFU) transducer has been performed in normal and diabetic animal models recently. HIFU can reversibly block the conduction of peripheral nerves without damaging the nerves while using an appropriate ultrasonic parameter. Temporary and partial block of the action potentials of nerves shows that HIFU has the potential to be a useful clinical treatment for pain relief. This work demonstrates the procedures for suppressing the action potentials of neuropathic nerves in diabetic rats in vivo using an HIFU transducer. The first step is to generate adult male diabetic neuropathic rats by streptozotocin (STZ) injection. The second step is to evaluate the peripheral diabetic neuropathy in STZ-induced diabetic rats by an electronic von Frey probe and a hot plate. The final step is to record in vivo extracellular action potentials of the nerve exposed to HIFU sonication. The method showed here may benefit the study of ultrasound analgesic applications.

This work presents the methodology of applying high intensity-focused ultrasound to block the action potentials of diabetic neuropathic nerves.

Nerve conduction block with a high intensity-focused ultrasound (HIFU) transducer has been performed in normal and diabetic animal models recently. HIFU ...

Bioengineering

In vivo Structural Assessments of Ocular Disease in Rodent Models using Optical Coherence Tomography

Spectral-domain optical coherence tomography (SD-OCT) is useful for visualizing retinal and ocular structures in vivo. In research, SD-OCT is a valuable tool to evaluate and characterize changes in a variety of retinal and ocular disease and injury models. In light induced retinal degeneration models, SD-OCT can be used to track thinning of the photoreceptor layer over time. In glaucoma models, SD-OCT can be used to monitor decreased retinal nerve fiber layer and total retinal thickness and to observe optic nerve cupping after inducing ocular hypertension. In diabetic rodents, SD-OCT has helped researchers observe decreased total retinal thickness as well as decreased thickness of specific retinal layers, particularly the retinal nerve fiber layer with disease progression. In mouse models of myopia, SD-OCT can be used to evaluate axial parameters, such as axial length changes. Advantages of SD-OCT include in vivo imaging of ocular structures, the ability to quantitatively track changes in ocular dimensions over time, and its rapid scanning speed and high resolution. Here, we detail the methods of SD-OCT and show examples of its use in our laboratory in models of retinal degeneration, glaucoma, diabetic retinopathy, and myopia. Methods include anesthesia, SD-OCT imaging, and processing of the images for thickness measurements.

Here, we describe the use of spectral-domain optical coherence tomography (SD-OCT) to visualize retinal and ocular structures in vivo in models of retinal degeneration, glaucoma, diabetic retinopathy, and myopia.

Spectral-domain optical coherence tomography (SD-OCT) is useful for visualizing retinal and ocular structures in vivo. In research, SD-OCT is a valuable ...

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.

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 ...

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 ...

Neuroscience

Alternate Immersion in Glucose to Produce Prolonged Hyperglycemia in Zebrafish

Zebrafish (Danio rerio) are an excellent model to investigate the effects of chronic hyperglycemia, a hallmark of Type II Diabetes Mellitus (T2DM). This alternate immersion protocol is a noninvasive, step-wise method of inducing hyperglycemia for up to eight weeks. Adult zebrafish are alternately exposed to sugar (glucose) and water for 24 hours each. The zebrafish begin treatment in a 1% glucose solution for 2 weeks, then a 2% solution for 2 weeks, and finally a 3% solution for the remaining 4 weeks. Compared to water-treated (stress) and mannitol-treated (osmotic) controls, glucose-treated zebrafish have significantly higher blood sugar levels. The glucose-treated zebrafish show blood sugar levels of 3-times that of controls, suggesting that after both four and eight weeks hyperglycemia can be achieved. Sustained hyperglycemia was associated with increased Glial Fibrillary Acidic Protein (GFAP) and increased nuclear factor Kappa B (NF-kB)&#160;levels in retina and decreased physiological responses, as well as cognitive deficits suggesting this protocol can be used to model disease complications.

This protocol noninvasively induces hyperglycemia in zebrafish for up to 8 weeks. Using this protocol, an in-depth study of the adverse effects of hyperglycemia can be made.

Zebrafish (Danio rerio) are an excellent model to investigate the effects of chronic hyperglycemia, a hallmark of Type II Diabetes Mellitus (T2DM). This ...

A New Optokinetic Testing Method to Measure Rat Vision

Optokinetic nystagmus (OKN) is a reflexive eye movement initiated by the motion of visual stimuli in the field of vision. The head-tracking movement associated with OKN is commonly used as a measure of visual function in rodents. To record OKN responses in normal and experimental rats, a simple and inexpensive apparatus has been developed. This setup uses two tablet screens to display the OKN visual stimulus consisting of high contrast black and white stripes generated using the OKN Stripes Visualization Web Application, a freely available software. The rat is placed inside a clear Plexiglass holder that limits&#160;movement so that the&#160;rat&#39;s head continuously faces the OKN display screen. The position of the rat holder can be changed to adjust the distance between the rat and the display screen. A micro-camera positioned above the rat holder is used to record the rat&#39;s visual activities. These recordings can be used for quantitative assessments. Based on the presence or absence of clear head-tracking, the OKN responses at different spatial frequencies can be determined. The collected data demonstrates a novel technique for reliable measurement of visual acuity in normal and retinal degenerate rats.

The Optokinetic Nystagmus (OKN) behavioral testing method is used for the assessment of visual acuity in rodents. Here a simple method is demonstrated that can be easily set up in research laboratories for a reliable assessment of visual function in both normal and experimental rats.

Optokinetic nystagmus (OKN) is a reflexive eye movement initiated by the motion of visual stimuli in the field of vision. The head-tracking movement ...

Retinal Pathophysiological Evaluation in a Rat Model

A posterior segment eye disease like diabetic retinopathy alters the physiology of the retina. Diabetic retinopathy is characterized by a retinal detachment, breakdown of the blood-retinal barrier (BRB), and retinal angiogenesis. An in vivo rat model is a valuable experimental tool to examine the changes in the structure and function of the retina. We propose three different experimental techniques in the rat model to identify morphological changes of retinal cells, retinal vasculature, and compromised BRB. Retinal histology is used to study the morphology of various retinal cells. Also, quantitative measurement is performed by retinal cell count and thickness measurement of different retinal layers. A BRB breakdown assay is used to determine the leakage of extraocular proteins from the plasma to vitreous tissue due to the breakdown of BRB. Fluorescence angiography is used to study angiogenesis and leakage of blood vessels by visualizing retinal vasculature using FITC-dextran dye.

Diabetic retinopathy is one of the leading causes of blindness. Histology, blood-retinal barrier breakdown assay, and fluorescence angiography are valuable techniques to understand the pathophysiology of the retina, which could further enhance the efficient drug screening against diabetic retinopathy.

A posterior segment eye disease like diabetic retinopathy alters the physiology of the retina. Diabetic retinopathy is characterized by a retinal ...

Novel Retina Protection Assay for Diabetic Retinopathy Pathogenesis Study

An Assay to Detect Protection of the Retinal Vasculature from Diabetes-Related Death in Mice

Diabetic retinopathy (DR) is a complex and progressive ocular disease characterized by two distinct phases in its pathogenesis. The first phase involves the loss of protection from diabetes-induced damage to the retina, while the second phase centers on the accumulation of this damage. Traditional assays primarily focus on evaluating capillary degeneration, which is indicative of the severity of damage, essentially addressing the second phase of DR. However, they only indirectly provide insights into whether the protective mechanisms of the retinal vasculature have been compromised. To address this limitation, a novel approach was developed to directly assess the retina's protective mechanisms - specifically, its resilience against diabetes-induced insults like oxidative stress and cytokines. This protection assay, although initially designed for diabetic retinopathy, holds the potential for broader applications in both physiological and pathological contexts. In summary, understanding the pathogenesis of diabetic retinopathy involves recognizing the dual phases of protection loss and damage accumulation, with this innovative protection assay offering a valuable tool for research and potentially extending to other medical conditions.

Author Spotlight: Understanding Retinal Vessel Resilience and Disease Progression

A protection assay was developed to monitor the retinal vasculature's resilience to death from diabetes/diabetic retinopathy-related insults such as oxidative stress and cytokines.

Diabetic retinopathy (DR) is a complex and progressive ocular disease characterized by two distinct phases in its pathogenesis. The first phase involves ...

Assessing Retinal Thickness and Ganglion Cell Layer Counts in Rodent Eyeballs

Preparation and Analysis of Histological Slides of Rat and Mouse Eyeballs to Evaluate the Retina

A rodent eyeball is a powerful tool for researching the pathomechanisms of many ophthalmic diseases, such as glaucoma, hypertensive retinopathy, and many more. Preclinical experiments enable researchers to examine the efficacy of novel drugs, develop new methods of treatment, or seek new pathomechanisms involved in the disease's onset or progression. A histological examination provides a lot of information necessary to assess the effects of the conducted experiments and can reveal degeneration, tissue remodeling, infiltration, and many other pathologies. In clinical research, there is rarely any chance of obtaining eye tissue suitable for a histological examination, which is why researchers should take advantage of the opportunity offered by the examination of eyeballs from rodents. This manuscript presents a protocol for the histological preparation of rodent eyeballs' sections. The procedure is presented for the eyeballs of mice and rats and has the following steps: (i) harvesting the eyeball, (ii) preserving the eyeball for further analysis, (iii) processing the tissue in paraffin, (iv) preparing slides, (v) staining with hematoxylin and eosin, (vi) assessing the tissue under a light microscope. With the proposed method, the retina can be easily visualized and assessed in detail.

This manuscript presents a protocol for the histological preparation of slides from rodent eyeballs. With the proposed method, the inner retina can be easily visualized and assessed under a light microscope. The procedure is presented for the eyeballs of mice and rats.

A rodent eyeball is a powerful tool for researching the pathomechanisms of many ophthalmic diseases, such as glaucoma, hypertensive retinopathy, and many ...

Behavioral Assessment of Visual Function via Optomotor Response and Cognitive Function via Y-Maze in Diabetic Rats

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