This work is supported by NIH grants EY024932, EY023295, and EY028106 to YH.

All procedures have been approved by the Institutional Animal Care and Use Committee (IACUC) of Stanford University.
1. Ocular hypertension induction by intracameral injection of SO
<ol>
	<li>Prepare a glass micropipette for intracameral SO injection by pulling a glass capillary with a pipette puller to generate a micropipette. Cut an opening at the tip of the micropipette and further sharpen the tip with a microgrinder-beveling machine to make a 35&#176;&#8722;40&#176; bevel.</li>
	<li>Polish the edges of the bevel and remove all debris by washing with water. Autoclave the micropipette before use.</li>
	<li>Prepare the paracentesis needle for the corneal entry. To do so, attach a 32 G needle to a 5 mL syringe on a Luer lock, and further secure it with tape. Bend the needle bevel tip face up at 30&#176;.</li>
	<li>Prepare the SO injector by attaching and securing a blunt end 18 G needle on a 10 mL syringe first. Then attach a plastic tube with the 18 G needle on one end and fill up with SO as needed through the other end.</li>
	<li>Attach the sterilized micropipette to the plastic tube and push the syringe plunger to fill the entire micropipette with SO.</li>
</ol>
2. Intracameral SO injection for one eye
<ol>
	<li>Place a 9&#8722;10-week-old male C57B6/J mouse into an induction chamber with 3% isoflurane mixed with oxygen at 2 L/min for 3 min.</li>
	<li>Intraperitoneally inject 2,2,2-tribromoethanol at 0.3 mg/g body weight. 
	NOTE: Unlike ketamine/xylazine, 2,2,2-tribromoethanol does not cause obvious pupil dilation.</li>
	<li>Check for the lack of response to a toe pinch and the lack of movement of the whiskers or the tail to determine the anesthetic strength.</li>
	<li>Place the mouse in a lateral position on a surgery platform. To reduce its sensitivity during the procedure, apply one drop of 0.5% proparacaine hydrochloride to the cornea before the injection.</li>
	<li>Make an entry incision with the 32 G paracentesis needle at the superotemporal quadrant, about 0.5 mm from the limbus.</li>
	<li>Tunnel through the layers of the cornea for about 0.3 mm before piercing into the anterior chamber. Be careful not to touch the lens or iris.</li>
	<li>Withdraw the needle slowly to release some aqueous humor (about 1&#8722;2 &#181;L) from the anterior chamber through the tunnel (paracentesis).</li>
	<li>Wait ~8 min to further decrease the IOP. This can be determined by measuring the contralateral, control eye.</li>
	<li>Insert the glass micropipette preloaded with SO through the corneal tunnel into the anterior chamber, with the bevel facing down to the iris surface.</li>
	<li>Push the syringe plunger slowly to inject SO into the anterior chamber until the SO droplet covers most of the iris surface, ~2.3&#8722;2.4 mm in diameter.</li>
	<li>Leave the micropipette in the anterior chamber for 10 s more before withdrawing it slowly.</li>
	<li>Gently push the upper eyelid to close the cornea incision to minimize SO leakage.</li>
	<li>Apply antibiotic ointment (bacitracin-neomycin-polymyxin) to the eye surface.</li>
	<li>Throughout the procedure, frequently moisten the cornea with artificial tears.</li>
	<li>Keep the mouse on the heating pad until fully recovered from anesthesia.</li>
</ol>
3. SO removal
<ol>
	<li>Prepare the irrigation system.
	<ol>
		<li>Prepare the irrigating solution according to the manufacturer&#8217;s instructions and place it in the irrigation bottle. Elevate the irrigating solution bottle to 110&#8722;120 cm (81&#8722;88 mmHg) above the surgery platform.</li>
		<li>Attach an IV administration set to the irrigating solution bottle. Remove air bubbles from the IV tubing. Connect a 33 G needle bent to 20&#176; face up to the IV tubing.</li>
	</ol>
	</li>
	<li>To prepare the drainage system, remove the plunger from a 1 mL syringe. Attach a 33 G needle to the syringe and bend the needle to 20&#176;.</li>
	<li>Remove SO from the anterior chamber.
	<ol>
		<li>Intraperitoneally inject 2,2,2-tribromoethanol (0.3 mg/g body weight). Check for the lack of response to the toe pinch to determine the anesthetic strength and the lack of movement of the whiskers or the tail.</li>
		<li>Place the mouse on a surgery platform and secure it in the lateral position with tape. Apply one drop of 0.5% proparacaine hydrochloride to the cornea to reduce its sensitivity.</li>
		<li>Make two incisions in the temporal quadrant of the cornea between ~2 and 5 o&#8217;clock at the edge of the SO droplet using the premade 32 G paracentesis needle.</li>
		<li>Insert a 33 G irrigation needle connected to irrigating solution through one corneal incision, maximum speed.</li>
		<li>Insert another 33 G drainage needle attached to the syringe without a plunger through the other corneal incision to allow the SO droplet to exit the anterior chamber while irrigating with irrigating solution.</li>
		<li>Withdraw the drainage needle, then the irrigation needle.</li>
		<li>Inject an air bubble into the anterior chamber to maintain its normal depth and press to close the corneal incision.</li>
		<li>Apply antibiotic ointment to both eyes.</li>
		<li>Keep the mouse on the heating recovery pad until fully recovered from the anesthesia.</li>
	</ol>
	</li>
</ol>
4. IOP measurement once a week
<ol>
	<li>Place the mouse into an induction chamber perfused with 3% isoflurane mixed with oxygen at 2L/min for 3 min.</li>
	<li>Intraperitoneally inject xylazine and ketamine (0.01 mg xylazine/g, 0.08 mg ketamine/g).</li>
	<li>Keep the cornea moist by applying artificial tears throughout the procedure.</li>
	<li>Wait about 15 min to allow the pupil to fully dilate.</li>
	<li>Measure the IOP of both eyes using a tonometer according to product instructions. Bring the tonometer near the mouse eye. Keep the distance from the tip of the probe to the mouse cornea at about 3&#8722;4 mm. Press the measuring button 6x to generate one reading. Three machine-generated readings are obtained from each eye to acquire the mean IOP.</li>
	<li>Sacrifice the animals at 8 weeks after SO injection and perform immunohistochemistry of whole-mount retina, RGC counting, optic nerve (ON) semi-thin sections, and quantification of surviving axons, which have been described before13.</li>
</ol>

<ol>
	<li>Chang, E. E., Goldberg, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glaucoma+2.0:+neuroprotection,+neuroregeneration,+neuroenhancement.">Glaucoma 2.0: neuroprotection, neuroregeneration, neuroenhancement.</a> Ophthalmology. 119 (5), 979-986 (2012).</li><li>Tham, Y. 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=Global+prevalence+of+glaucoma+and+projections+of+glaucoma+burden+through+2040:+a+systematic+review+and+meta-analysis.">Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis.</a> Ophthalmology. 121 (11), 2081-2090 (2014).</li><li>Pang, I. H., Clark, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rodent+models+for+glaucoma+retinopathy+and+optic+neuropathy.">Rodent models for glaucoma retinopathy and optic neuropathy.</a> Journal of Glaucoma. 16 (5), 483-505 (2007).</li><li>Morrison, J. C., Johnson, E., Cepurna, W. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rat+models+for+glaucoma+research.">Rat models for glaucoma research.</a> Progress in Brain Research. 173, 285-301 (2008).</li><li>McKinnon, S. J., Schlamp, C. L., Nickells, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+of+retinal+ganglion+cell+death+and+glaucoma.">Mouse models of retinal ganglion cell death and glaucoma.</a> Experimental Eye Research. 88 (4), 816-824 (2009).</li><li>Chen, S., Zhang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Rodent+Model+of+Glaucoma+and+Its+Implications.">The Rodent Model of Glaucoma and Its Implications.</a> Asia Pacific Journal of Ophthalmology (Philadelphia). 4 (4), 236-241 (2015).</li><li>Sappington, R. M., Carlson, B. J., Crish, S. D., Calkins, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+microbead+occlusion+model:+a+paradigm+for+induced+ocular+hypertension+in+rats+and+mice.">The microbead occlusion model: a paradigm for induced ocular hypertension in rats and mice.</a> Investigative Ophthalmology and Visual Science. 51 (1), 207-216 (2010).</li><li>Chen, H., 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+neuropathy+due+to+microbead-induced+elevated+intraocular+pressure+in+the+mouse.">Optic neuropathy due to microbead-induced elevated intraocular pressure in the mouse.</a> Investigative Ophthalmology and Visual Science. 52 (1), 36-44 (2011).</li><li>Cone, F. E., Gelman, S. E., Son, J. L., Pease, M. E., Quigley, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+susceptibility+to+experimental+glaucoma+among+3+mouse+strains+using+bead+and+viscoelastic+injection.">Differential susceptibility to experimental glaucoma among 3 mouse strains using bead and viscoelastic injection.</a> Experimental Eye Research. 91 (3), 415-424 (2010).</li><li>Samsel, P. A., Kisiswa, L., Erichsen, J. T., Cross, S. D., Morgan, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+method+for+the+induction+of+experimental+glaucoma+using+magnetic+microspheres.">A novel method for the induction of experimental glaucoma using magnetic microspheres.</a> Investigative Ophthalmology and Visual Science. 52 (3), 1671-1675 (2011).</li><li>Ichhpujani, P., Jindal, A., Jay Katz, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silicone+oil+induced+glaucoma:+a+review.">Silicone oil induced glaucoma: a review.</a> Graefes Archieves for Clinical and Experimental Ophthalmology. 247 (12), 1585-1593 (2009).</li><li>Kornmann, H. L., Gedde, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glaucoma+management+after+vitreoretinal+surgeries.">Glaucoma management after vitreoretinal surgeries.</a> Current Opinion in Ophthalmology. 27 (2), 125-131 (2016).</li><li>Zhang, 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=Silicone+oil-induced+ocular+hypertension+and+glaucomatous+neurodegeneration+in+mouse.">Silicone oil-induced ocular hypertension and glaucomatous neurodegeneration in mouse.</a> Elife. 8, (2019).</li><li>Kwong, J. M., Caprioli, J., Piri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+binding+protein+with+multiple+splicing:+a+new+marker+for+retinal+ganglion+cells.">RNA binding protein with multiple splicing: a new marker for retinal ganglion cells.</a> Investigative Ophthalmology and Visual Science. 51 (2), 1052-1058 (2010).</li><li>Rodriguez, A. R., de Sevilla Muller, L. P., Brecha, N. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+RNA+binding+protein+RBPMS+is+a+selective+marker+of+ganglion+cells+in+the+mammalian+retina.">The RNA binding protein RBPMS is a selective marker of ganglion cells in the mammalian retina.</a> Journal of Comparative Neurology. 522 (6), 1411-1443 (2014).</li><li>Smith, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Systematic evaluation of the mouse eye : anatomy, pathology, and biomethods. , (2002).</li></ol>

The authors have nothing to disclose.

Here we demonstrate a simple but effective procedure for inducing sustained IOP elevation in the mouse eye by intracameral injection of SO. This procedure can be learned quickly by anyone with experience in microdissection under a microscope. The primary potential risk of failure is the leakage of SO from the corneal incision. However, one of the advantages of using SO is that because the oil droplet is visible and measurable, we can easily identify mice that received droplets too small to induce stable ocular hypertensi...

The progressive loss of retinal ganglion cells (RGCs) and their axons is the hallmark of glaucoma, a common neurodegenerative disease in the retina1. It will affect more than 100 million individuals 40&#8722;80 years old by 20402. IOP remains the only modifiable risk factor in the development and progression of glaucoma. In order to explore the pathogenesis, progression, and potential treatments of glaucoma, a reliable, reproducible, and inducible experimental ocular hypertension/glaucoma model that replicates key features of human patients is imperative.
IOP depends on aqueous humor inflow to the anterior chamber from the ciliary body in the posterior chamber and outflow through the trabecular meshwork (TM) at the angle of the anterior chamber. Upon reaching a steady state, IOP is maintained. When the inflow exceeds or is less than the outflow, IOP rises or falls respectively. By decreasing the aqueous outflow either by occluding the angle of the anterior chamber or by damaging the TM, several glaucoma models have been established3,4,5,6,7,8,9,10. These models are normally associated with irreversible ocular tissue damage, and the high IOP in the anterior chamber also causes unwanted complications such as corneal edema and intraocular inflammation, which make retinal imaging and visual function assays difficult to perform and interpret.
To develop a model that overcomes these shortcomings, we focused on the well-sudocumented secondary glaucoma caused by silicone oil (SO) that occurs as a postoperative complication of human vitreoretinal surgery11,12. SO is used as a tamponade in retinal surgeries because of its high surface tension. However, SO can physically occlude the pupil because it is lighter than the aqueous and vitreous fluids, which prevents aqueous flow into the anterior chamber. The obstruction causes IOP elevation in the posterior chamber due to the aqueous humor accumulation. This motivated us to develop and characterize a novel ocular hypertension mouse model based on intracameral SO injection and pupillary block13, with key features of the secondary glaucoma: effective pupillary block, significant IOP elevation that can return to normal after SO removal, and glaucomatous neurodegeneration.
Here we present a detailed protocol for SO-induced ocular hypertension in the mouse eye, including SO injection and removal and IOP measurement.

<table><tbody><tr><td>0.5% proparacaine hydrochloride</td><td>Akorn, Somerset</td><td></td><td></td></tr><tr><td>10mL syinge</td><td>BD</td><td></td><td>Luer-Lok Tip</td></tr><tr><td>18G needle</td><td>BD</td><td></td><td>with Regular Bevel, Needle Length:25.4 mm</td></tr><tr><td>2,2,2-Tribromoethanol (Avertin)</td><td>Fisher Scientific</td><td>CAS# 75-80-9</td><td>50g</td></tr><tr><td>32G nano</td><td>BD</td><td>320122</td><td>BD Nano Ultra Fine Pen Needle-32G 4mm</td></tr><tr><td>33G ophalmology needle</td><td>TSK/ VWR</td><td>TSK3313/ 10147-200</td><td></td></tr><tr><td>5mL syinge</td><td>BD</td><td></td><td>Luer-Lok Tip</td></tr><tr><td>AnaSed Injection (xylazine)</td><td>Butler Schein</td><td></td><td>100 mg/ml, 50 ml</td></tr><tr><td>artificial tears</td><td>Alcon Laboratories</td><td>300651431414</td><td>Systane Ultra Lubricant Eye Drops</td></tr><tr><td>BSS PLUS Irrigating solution</td><td>Alcon Laboratories</td><td>65080050</td><td></td></tr><tr><td>Dual-Stage Glass Micropipette Puller</td><td>NARISHIGE</td><td>PC-10</td><td></td></tr><tr><td>EZ-7000 Classic System</td><td>EZ system</td><td></td><td></td></tr><tr><td>Isoflurane</td><td>VetOne</td><td>502017</td><td>isoflurane, USP, 250ml/bottle</td></tr><tr><td>IV Administration sets</td><td>EXELint/ Fisher</td><td>29081</td><td></td></tr><tr><td>KETAMINE HYDROCHLORIDE INJECTION</td><td>VEDCO</td><td>50989-996-06</td><td>KETAVED 100mg/ml * 10ml</td></tr><tr><td>microgrind bevelling machine</td><td>NARISHIGE</td><td>EG-401</td><td></td></tr><tr><td>Miniature EVA Tubing</td><td>McMaster-Carr</td><td>1883T4</td><td>0.05&quot; ID, 0.09&quot; OD, 10 ft. Length</td></tr><tr><td>silicon oil (SILIKON)</td><td>Alcon Laboratories</td><td>8065601185</td><td>1,000 mPa.s</td></tr><tr><td>Standard Glass Capillaries</td><td>WPI/ Fisher</td><td>1B150-4</td><td>4 in. (100mm) OD 1.5mm ID 0.84mm</td></tr><tr><td>TonoLab tonometer</td><td>Colonial Medical Supply, Finland</td><td></td><td></td></tr><tr><td>veterinary antibiotic ointment</td><td>Dechra Veterinary</td><td>1223RX</td><td>BNP ophthalmic ointment, Vetropolycin</td></tr></tbody></table>

a reversible silicon oil-induced ocular hypertension model in mice

Elevated intraocular pressure (IOP) is a well-documented risk factor for glaucoma. Here we describe a novel, effective method for consistently inducing stable IOP elevation in mice that mimics the post-operative complication of using silicone oil (SO) as a tamponade agent in human vitreoretinal surgery. In this protocol, SO is injected into the anterior chamber of the mouse eye to block the pupil and prevent inflow of aqueous humor. The posterior chamber accumulates aqueous humor and this in turn increases the IOP of the posterior segment. A single SO injection produces reliable, sufficient, and stable IOP elevation, which induces significant glaucomatous neurodegeneration. This model is a true replicate of secondary glaucoma in the eye clinic. To further mimic the clinical setting, SO can be removed from the anterior chamber to reopen the drainage pathway and allow inflow of aqueous humor, which is drained through the trabecular meshwork (TM) at the angle of the anterior chamber. Because IOP quickly returns to normal, the model can be used to test the effect of lowering IOP on glaucomatous retinal ganglion cells. This method is straightforward, does not require special equipment or repeat procedures, closely simulates clinical situations, and may be applicable to diverse animal species. However, minor modifications may be required.

Soon after the injection we can easily identify mice that do not produce stable ocular hypertension because of the SO droplets being too small (&#8804;1.5 mm)13. These animals are excluded from subsequent experiments. Following the injection procedures, more than 80% of SO injected mice end up with droplets larger than 1.6 mm. We measured the IOP of these mouse eyes once a week for 8 weeks after a single SO injection. The IOP of the eye receiving SO remained high, generally double the IOP of the c...

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A Reversible Silicon Oil-Induced Ocular Hypertension Model in Mice

Here, we present a protocol to induce ocular hypertension and glaucomatous neurodegeneration in mouse eyes by intracameral injection of silicone oil and the procedure for silicone oil removal from the anterior chamber to return elevated intraocular pressure to normal.

Elevated intraocular pressure (IOP) is a well-documented risk factor for glaucoma. Here we describe a novel, effective method for consistently inducing ...

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9.8K Views.  Stanford University School of Medicine. Glaucoom is de belangrijkste oorzaak van onomkeerbare blindheid, gekenmerkt door retinale ganglion celdood en de opto-neurodegeneratie. Verhoging van intraoculaire druk, ook wel oculaire hypertensie genoemd, is de meest erkende risicofactor voor glaucoom. Een eenvoudig maar effectief oculair hypertensiemodel bij proefdieren zoals muizen is belangrijk voor het onderzoeken van glaucometers in neurodegeneratie en het testen van de behandeling voor neuroprotectie.Zo ontwikkelen we met resu...

Video: A Reversible Silicon Oil-Induced Ocular Hypertension Model in Mice

Laser-Induced Chronic Ocular Hypertension Model on SD Rats

Glaucoma is one of the major causes of blindness in the world. Elevated intraocular pressure is a major risk factor. Laser photocoagulation induced ocular hypertension is one of the well established animal models. This video demonstrates how to induce ocular hypertension by Argon laser photocoagulation in rat.

Glaucoma is one of the major causes of blindness in the world. Elevated intraocular pressure is a major risk factor. Laser photocoagulation induced ocular hypertension is one of the well established animal models. This video demonstrates how to induce ocular hypertension by Argon laser photocoagulation in rat.

Glaucoma is one of the major causes of blindness in the world. Elevated intraocular pressure is a major risk factor. Laser photocoagulation induced ocular ...

Biology

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 ...

Experimental Glaucoma Induced by Ocular Injection of Magnetic Microspheres

Progress in understanding the pathophysiology, and providing novel treatments for glaucoma is dependent on good animal models of the disease. We present here a protocol for elevating intraocular pressure (IOP) in the rat, by injecting magnetic microspheres into the anterior chamber of the eye. The use of magnetic particles allows the user to manipulate the beads into the iridocorneal angle, thus providing a very effective blockade of fluid outflow from the trabecular meshwork. This leads to long-lasting IOP rises, and eventually neuronal death in the ganglion cell layer (GCL) as well as optic nerve pathology, as seen in patients with the disease. This method is simple to perform, as it does not require machinery, specialist surgical skills, or many hours of practice to perfect. Furthermore, the pressure elevations are very robust, and reinjection of the magnetic microspheres is not usually required unlike in some other models using plastic beads. Additionally, we believe this method is suitable for adaptation for the mouse eye.

We present a method for inducing elevated intraocular pressure (IOP), by injecting magnetic microspheres into the rat eye, to model glaucoma. This leads to strong pressure rises, and extensive neuronal death. This protocol is easy to perform, does not require repeat injections, and produces stable long-lasting IOP rises.

Progress in understanding the pathophysiology, and providing novel treatments for glaucoma is dependent on good animal models of the disease. We present ...

A Magnetic Microbead Occlusion Model to Induce Ocular Hypertension-Dependent Glaucoma in Mice

The use of rodent models of glaucoma has been essential to understand the molecular mechanisms that underlie the pathophysiology of this multifactorial neurodegenerative disease. With the advent of numerous transgenic mouse lines, there is increasing interest in inducible murine models of ocular hypertension. Here, we present an occlusion model of glaucoma based on the injection of magnetic microbeads into the anterior chamber of the eye using a modified microneedle with a facetted bevel. The magnetic microbeads are attracted to the iridocorneal angle using a handheld magnet to block the drainage of aqueous humour from the anterior chamber. This disruption in aqueous dynamics results in a steady elevation of intraocular pressure, which subsequently leads to the loss of retinal ganglion cells, as observed in human glaucoma patients. The microbead occlusion model presented in this manuscript is simple compared to other inducible models of glaucoma and also highly effective and reproducible. Importantly, the modifications presented here minimize common issues that often arise in occlusion models. First, the use of a bevelled glass microneedle prevents backflow of microbeads and ensures that minimal damage occurs to the cornea during the injection, thus reducing injury-related effects. Second, the use of magnetic microbeads ensures the ability to attract most beads to the iridocorneal angle, effectively reducing the number of beads floating in the anterior chamber avoiding contact with other structures (e.g., iris, lens). Lastly, the use of a handheld magnet allows flexibility when handling the small mouse eye to efficiently direct the magnetic microbeads and ensure that there is little reflux of the microbeads from the eye when the microneedle is withdrawn. In summary, the microbead occlusion mouse model presented here is a powerful investigative tool to study neurodegenerative changes that occur during the onset and progression of glaucoma.

Here, we present a protocol to induce ocular hypertension in the murine eye that results in the loss of retinal ganglion cells as observed in glaucoma. Magnetic microbeads are injected into the anterior chamber and attracted to the iridocorneal angle using a magnet to block the outflow of aqueous humour.

The use of rodent models of glaucoma has been essential to understand the molecular mechanisms that underlie the pathophysiology of this multifactorial ...

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 ...

Bioengineering

Inducement and Evaluation of a Murine Model of Experimental Myopia

Murine model of myopia can be a powerful tool for myopia research because of the comparatively easy genetic manipulation. One way to induce myopia in animals is to put clear minus lenses in front of eyes for weeks (lens-induced myopia, LIM). However, extant protocols for inducement and evaluation vary from laboratory to laboratory. Here, we described a highly practical and reproducible method to induce LIM in mice using newly designed eyeglasses. The method fixes the lens stably in front of the mouse eye while allows the lens to be taken off for cleaning or topical drug administration. The phenotype is robust and efficient, and the variance is small. The method described here can be applied to mice right after weaning which extends the possible duration for experiments. We also gave technical advises for achieving reproducible results in refraction and axial length measurements. We hope the step-by-step protocol described here and the detailed article can help researchers perform myopia experiments with myopia more smoothly and make the data comparable across laboratories.

In this protocol, we describe the full process of experimental myopia inducement in mice using newly designed eyeglasses and the technic needed for achieving stable and reproducible results in ocular parameter measurements.

Murine model of myopia can be a powerful tool for myopia research because of the comparatively easy genetic manipulation. One way to induce myopia in ...

Neuroscience

A Model of Glaucoma Induced by Circumlimbal Suture in Rats and Mice

The circumlimbal suture is a technique for inducing experimental glaucoma in rodents by chronically elevating intraocular pressure (IOP), a well-known risk factor for glaucoma. This protocol demonstrates a step-by-step guide on this technique in Long Evans rats and C57BL/6 mice. Under general anesthesia, a "purse-string" suture is applied on the conjunctiva, around the equator and behind the limbus of the eye. The fellow eye serves as an untreated control. Over the duration of our study, which was a period of 8 weeks for rats and 12 weeks for mice, IOP remained elevated, as measured regularly by rebound tonometry in conscious animals without topical anesthesia. In both species, the sutured eyes showed electroretinogram features consistent with preferential inner retinal dysfunction. Optical coherence tomography showed selective thinning of the retinal nerve fiber layer. Histology of the rat retina in cross-section found reduced cell density in the ganglion cell layer, but no change in other cellular layers. Staining of flat-mounted mouse retinae with a ganglion cell specific marker (RBPMS) confirmed ganglion cell loss. The circumlimbal suture is a simple, minimally invasive and cost-effective way to induce ocular hypertension that leads to ganglion cell injury in both rats and mice.

Chronic ocular hypertension is induced by applying a circumlimbal suture in rats and mice, leading to functional and structural deterioration of the retinal ganglion cells consistent with glaucoma.

The circumlimbal suture is a technique for inducing experimental glaucoma in rodents by chronically elevating intraocular pressure (IOP), a well-known ...

Full-Circle Cauterization of Limbal Vascular Plexus for Surgically Induced Glaucoma in Rodents

Glaucoma, the second leading cause of blindness worldwide, is a heterogeneous group of ocular disorders characterized by structural damage to the optic nerve and retinal ganglion cell (RGC) degeneration, resulting in visual dysfunction by interrupting the transmission of visual information from the eye to the brain. Elevated intraocular pressure is the most important risk factor; thus, several models of ocular hypertension have been developed in rodents by either genetic or experimental approaches to investigate the causes and effects of the disease. Among those, some limitations have been reported such as surgical invasiveness, inadequate functional assessment, requirement of extensive training, and highly variable extension of retinal damage. The present work characterizes a simple, low-cost, and efficient method to induce ocular hypertension in rodents, based on low-temperature, full-circle cauterization of the limbal vascular plexus, a major component of aqueous humor drainage. The new model provides a technically easy, noninvasive, and reproducible subacute ocular hypertension, associated with progressive RGC and optic nerve degeneration, and a unique post-operative clinical recovery rate that allows in vivo functional studies by both electrophysiological and behavioral methods.

The goal of this protocol is to characterize a novel model of glaucomatous neurodegeneration based on 360&#176; thermic cauterization of limbal vascular plexus, inducing subacute ocular hypertension.

Glaucoma, the second leading cause of blindness worldwide, is a heterogeneous group of ocular disorders characterized by structural damage to the optic ...

Establishment of A Mouse Model of Aqueous Deficiency Dry Eye

Dry eye disease is a prevalent condition affecting 5%-50% of the global population. Animal model investigations play a crucial role in understanding its underlying mechanisms. Therefore, we developed a mouse model of dry eye disease by surgically removing both the extraorbital lacrimal glands (ELG) and intraorbital lacrimal glands (ILG) to investigate the ocular surface pathology in the context of aqueous deficiency dry eye. Two weeks post operation, the mice exhibited severe dry eye manifestations, including reduced tear secretion, corneal epithelial irregularities, positive fluorescein sodium staining, and neovascularization. Histological examination via hematoxylin and eosin staining revealed inflammatory cell infiltration and corneal epithelium dysplasia. Immunofluorescence staining and quantitative reverse-transcription polymerase chain reaction revealed decreased expression of the normal corneal epithelial biomarkers K12 and Pax6 and increased expression of Sprr1b in the corneal epithelium. These ocular manifestations indicated abnormal corneal epithelial differentiation. Furthermore, immunofluorescence staining of Ki67 revealed the increasing cell proliferation. In conclusion, the ELG plus ILG excision model proved suitable for studying changes in the ocular surface and elucidating the mechanisms underlying aqueous deficiency dry eye.

Here, we present a method to establish a mouse model of aqueous-deficient dry eye by excising the extraorbital and infraorbital lacrimal glands and evaluate the changes in the ocular surface in aqueous deficiency dry eye.

Dry eye disease is a prevalent condition affecting 5%-50% of the global population. Animal model investigations play a crucial role in understanding its ...

 Induction of Elevated Intraocular Pressure in a Rat Model

<a href='https://app.jove.com/v/63442/full-circle-cauterization-limbal-vascular-plexus-for-surgically'>Source: Lani-Louzada, R., et al., Full-Circle Cauterization of Limbal Vascular Plexus for Surgically Induced Glaucoma in Rodents. J. Vis. Exp. (2022)</a>This video demonstrates the induction and monitoring of elevated intraocular pressure (IOP) in a rat model. The process involves cauterizing the limbal blood vessels, resulting in vessel occlusion and elevated IOP. The rat is then allowed to recover, and IOP is regularly monitored in both the experimental and control eyes for comparison.

Source: Lani-Louzada, R., et al., Full-Circle Cauterization of Limbal Vascular Plexus for Surgically Induced Glaucoma in Rodents. J. Vis. Exp. (2022)This ...

A Reversible Silicon Oil-Induced Ocular Hypertension Model in Mice

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