July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Controlled Elevation of Intraocular Pressure (CEI): Physiologic and Ocular Responses in the Mouse
Author Affiliations & Notes
  • John C Morrison
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • David Simons
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Tiffany Choe
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Katherine Delf
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • William Cepurna
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Diana C Lozano
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Hari Jayaram
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
    Ophthalmology, NIHR Moorfields Biomedical Research Centre, London, United Kingdom
  • Shandiz Tehrani
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Elaine C. Johnson
    Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, United States
  • Footnotes
    Commercial Relationships   John Morrison, None; David Simons, None; Tiffany Choe, None; Katherine Delf, None; William Cepurna, None; Diana Lozano, None; Hari Jayaram, None; Shandiz Tehrani, None; Elaine Johnson, None
  • Footnotes
    Support  NIH-R01EY010145, NIH-R01EY010145-S1, NIH-T32EY023211, NIH-K08EY024025, RPB Career Development Award, The US-UK Fulbright Commission in conjunction with Fight for Sight and The Special Trustees of Moorfields Eye Hospital, NIH-P30EY01572, and an unrestricted grant from Research to Prevent Blindness.
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 3697. doi:
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      John C Morrison, David Simons, Tiffany Choe, Katherine Delf, William Cepurna, Diana C Lozano, Hari Jayaram, Shandiz Tehrani, Elaine C. Johnson; Controlled Elevation of Intraocular Pressure (CEI): Physiologic and Ocular Responses in the Mouse. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3697.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To develop a protocol for prolonged anesthesia in mice and evaluate optic nerve axon injury in response to 4 hours of controlled elevation of intraocular pressure (CEI).

Methods : C57BL/6NCrl male retired breeder mice (8 – 10 months old) were anesthetized with 1.5% isoflurane with 100% O2 for 4 hours, using active evacuation of expired gas and anesthetic, hydrated with intraperitoneal, warm lactated ringers (0.5 ml) with 5% dextrose at the start and end of the anesthesia, and temperature maintained with a warm water therapy pad. Oxygen saturation (O2), heart rate (HR) and respiratory rate (RR) were monitored throughout the experiment with a Mouse Ox Plus and blood pressure (BP) with a CODA tail cuff manometer. For CEI, one eye was cannulated with polyurethane tubing (tip diameter, 0.006 inch) connected to a reservoir containing balanced salt solution and elevated to 60 mmHg, verified by rebound tonometry.Ten days after exposure, mice were perfusion-fixed with glutaraldehyde to optimize morphology. Six masked observers graded optic nerve cross sections for injury on a scale from 1 (normal) to 5 (>50% of axons degenerating). Mean grades for 4 groups of eyes [(1) experimental CEI; (2) fellow; (3) anesthesia alone; and (4) naïve (no anesthesia or cannulation)] were calculated and compared by ANOVA.

Results : Mean physiologic values over the course of anesthesia (N= 13) were: O2 = 91 ± 2% (SEM), HR = 571 ± 7 and RR = 156 ± 13. Systolic, diastolic and mean BPs (N = 4) were 92± 14, 71±11 and 77 ± 12 mmHg, respectively. One animal died during the experiment and one failed to recover following anesthesia. Mean (± SEM) optic nerve injury grades were: 2.03 ± 0.41 for CEI eyes (N=7); 1.23 ± 0.16 for fellow eyes (N = 7); 1.09 ± 0.03 for naïve eyes (N = 8); and 1.06 ± 0.03 (N = 6) for anesthesia only eyes. ANOVA analysis identified the CEI group as the only one to have a significantly higher injury grade (CEI vs naïve, P = 0.02). No significant differences were noted between control, anesthesia only and naïve groups (p>0.99, all comparisons). Physiologic parameters in animals with greater CEI injury were similar to those with minimal injury.

Conclusions : Prolonged anesthesia in mice requires careful attention to animal physiology. With this, a 4-hour exposure to elevated IOP can produce variable, but significant optic nerve injury.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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