July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Characterization of circumlimbal suture induced chronic ocular hypertension in albino rats anaesthetised under Ketamine-Xylazine or Isoflurane
Author Affiliations & Notes
  • Yamunadevi LAKSHMANAN
    Laboratory of Experimental Optometry (Neuroscience), School of Optometry , The Hong Kong Polytechnic University, Kowloon, Hong Kong
  • Francisca Wong
    Laboratory of Experimental Optometry (Neuroscience), School of Optometry , The Hong Kong Polytechnic University, Kowloon, Hong Kong
  • Wing Yan Yu
    Laboratory of Experimental Optometry (Neuroscience), School of Optometry , The Hong Kong Polytechnic University, Kowloon, Hong Kong
  • Bing Zuo
    Laboratory of Experimental Optometry, Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong
  • Serena Zhe Chuang Li
    Laboratory of Experimental Optometry (Neuroscience), School of Optometry , The Hong Kong Polytechnic University, Kowloon, Hong Kong
    Laboratory of Experimental Optometry, Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong
  • Kai Yip Choi
    Laboratory of Experimental Optometry (Neuroscience), School of Optometry , The Hong Kong Polytechnic University, Kowloon, Hong Kong
    Laboratory of Experimental Optometry, Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong
  • Bang V Bui
    Department of Optometry & Vision Sciences, University of Melbourne, Melbourne, Victoria, Australia
  • Henry Ho-lung Chan
    Laboratory of Experimental Optometry (Neuroscience), School of Optometry , The Hong Kong Polytechnic University, Kowloon, Hong Kong
    Laboratory of Experimental Optometry, Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong
  • Footnotes
    Commercial Relationships   Yamunadevi LAKSHMANAN, None; Francisca Wong, None; Wing Yan Yu, None; Bing Zuo, None; Serena Zhe Chuang Li, None; Kai Yip Choi, None; Bang Bui, None; Henry Chan, None
  • Footnotes
    Support  Supported by the General Research Fund (PolyU 5605/13M) from Research Grants Council, HKSAR, Central Research Grant (for Research Student) and Internal Research Grants (G-TBBS, G-YBGC, Z0GF) from The Hong Kong Polytechnic University. Supported by the University Research Facility in Behavioral and Systems Neuroscience and in Life Science. Bang Bui is supported by an Australian Research Council Future Fellowship (FT130100330)
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 3700. doi:https://doi.org/
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      Yamunadevi LAKSHMANAN, Francisca Wong, Wing Yan Yu, Bing Zuo, Serena Zhe Chuang Li, Kai Yip Choi, Bang V Bui, Henry Ho-lung Chan; Characterization of circumlimbal suture induced chronic ocular hypertension in albino rats anaesthetised under Ketamine-Xylazine or Isoflurane. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3700. doi: https://doi.org/.

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

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Abstract

Purpose : The circumlimbal suture approach has been used for inducing chronic ocular hypertension (COH) in rodents. We considered whether this model also works in albino rats and if the anaesthesia at the time of model induction (ketamine-xylazine (KX) mixture and Isoflurane (ISO)) influences outcomes.

Methods : Sprague-Dawley rats (10 weeks old) anaesthetized with KX or ISO received a circumlimbal suture around both eyes. The suture on one randomly chosen eye was cut after day 1 (KX: n=16; ISO: n=12) to serve as the control. The suture on the treated COH eyes were left in place for 15 weeks (KX: n=16; ISO: n=11). IOP in awake rats was recorded twice a week (Tonolab). Changes (mean±SE) in retinal structure and function were subsequently assessed under KX (in both groups) at week 0, 4, 8, 12 and 15 using electroretinogram and optical coherence tomography, respectively.

Results : COH eyes showed significant IOP elevations of 4-8mmHg in KX and 3-5mmHg in ISO anesthetised rats between weeks 1 to 12 (p<0.05), there was a gradual reduction beyond 12 weeks. Positive scotopic threshold response (pSTR) amplitude were reduced (KX: 19+7% p>0.05; ISO: 21+9%; p=0.02) in COH eyes at weeks 8 and 12, with some recovery at week 15 in the KX group. Reductions in both b-wave (KX: 13+8% p>0.05; ISO: 19+8%; p=0.01) and a-wave responses (KX: 25+6%; ISO: 22+7%; p=0.01) at week 8 also showed recovery at week 15 in the KX group. A thinner retinal nerve fibre layer (RNFL) in the KX group was observed from week 4 (-7+3%; p=0.06) to week 12 (-6+4% from control eyes; p>0.05). As for the ISO group, RNFL thinning was noted at week 4 (-6+2%; p=0.06) and week 8 (-3+2% compared with control; p>0.05). Between weeks 12 to 15, total retinal thickness (5+1%; p<0.01) and outer retinal layer (7+1%; p<0.001) appeared to increase.

Conclusions : The circumlimbal suture model elevated IOP in albino rats regardless of the type of anaesthesia used during induction, resulting in similar structural and functional changes. There was mild RNFL thinning along with the reduction of ganglion cell function, that along with IOP reduction between weeks 12 and 15. Interestingly, a gradual thickening of outer retinal layer in sutured eyes has not been reported previously.

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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