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

Summary

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.

Abstract

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.

Protocol

Procedures

C57BL/6J mice (Jackson Laboratory, Bar Harbor, ME) are raised at Northwestern University's Animal Care Facility. All animals are used in accordance with protocols approved by Northwestern University Institutional Animal Care and Use Committee and conformed to the guidelines on the Use of Animals in Neuroscience Research from the NIH.

1. Laser Photocoagulation

The procedure of laser photocoagulation is modified from previously published protocols ^5-7.

1. Anesthetize a 40-60 day old mouse by an intraperitoneal injection of ketamine (100 mg/kg, Butler Schein An....

Results

As described in the Procedures, laser illumination is aimed at the trabecular meshwork in the limbal region to photocoagulate the aqueous outflow, inducing angle closure (Figure 1). Most lasered eyes exhibited no significant physical damage, pigment detachment or infection, consistent with previous findings ⁶. When a small group of mice (less than 5% of all lasered animals) exhibited physical signs of severe damage such as deflated eye balls, severe cataract, significant pigment detachment, or.......

Discussion

We report above that sustained ocular hypertension can be induced by laser illumination in mouse eyes. Compared to the saline injection model ¹⁸ and the vein cautery model ¹¹ both of which require extensive microsurgical skills, the laser illumination is relatively simple and easy to perform. Usually we can perform the laser illumination for 4-6 mice in 2-3 hr. The critical steps to achieve sustained IOP elevation are the anterior chamber flattening before laser and the parameters for laser illumina.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Reagent
moxifloxacin	Alcon Labs, Inc.	NDC 0065-4013-03	0.5 %, Rx only
Proparacaine Hydrochloride	Bausch Lomb	NDC 24208-730-06	0.5 %, Rx only
Ophthalmic Solution USP	Bausch Lomb	NDC 24208-730-06	.5 %, Rx only
ketamine	Butler Schein Animal Health	NDC 11695-0550-1	100 mg / kg
xylazine	LLOYD Inc. of Iowa	NADA 139-236	10 mg / kg
atropine sulfate solution	Alcon Labs, Inc.	NDC 61314-303-02	1 %, Rx only
Equipment
Slit Lamp, TOPCON	Visual Systems Inc	SL-3E	powered by PS-30A
OptoMotry 1.8.0 virtual	CerebralMechanics Inc.
opto-kinetic testing system	CerebralMechanics Inc.
Tonometer, TonoLab, for mice	Colonial Medical Supply
Heating pad	Sunbeam Products Inc	722-810
Argon laser	Coherent Inc	Ultima 2000SE
DECAPICONE Plastic cone holder	Braintree Sci Inc.	MDC-200	for mouse