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Mark Vezina, Kelly Tenneson, Martin Bussieres; Background Biometric and Morphometric Anterior Ocular Changes in the Juvenile Dutch-Belted Rabbits Compared to the Adult. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2654. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
An increasing number of ocular therapies are being targeted to children as well as adults. As such there is an increasing demand for the use of juvenile animals to support human clinical trials. The purpose of this evaluation is to characterize background anterior ocular changes in juvenile Dutch Belted Rabbits commencing at the age of 6 weeks for comparison to adults.
Eyes were evaluated by slit lamp biomicroscopy (with fluorescein staining), pachymetry (corneal thickness) using a handheld ultrasound device, and tonometry (intraocular pressure-IOP) using a handheld rebound tonometer. Assessments were conducted at 6 weeks (n= 104 eyes), 10 weeks (n=24 eyes) and 14 weeks (n=24 eyes) of age and compared to existing background data from young adults of approximately 24 weeks of age.
At 6 weeks of age, slit lamp observations were minimal with only 3/104 (2.8%) eyes showing multifocal corneal opacities, 1 eye with slight +ve fluorescein staining and focal lens opacities in 2 eyes (one nuclear and one cortex). This incidence of multifocal corneal opacities increased to approximately 13% by 14 weeks. Comparatively, the adult eyes at 24 weeks (n=212 eyes) predominantly had nuclear lens opacities (13%) followed by a minor incidence of prominent lens suture, focal corneal opacity and persistent pupillary membrane.Corneas at 6 weeks were thinner than the lower limit of the instrument for the majority of eyes (< 300 um). By 10 weeks, most of the corneas were in the 310-330 um thickness range and by 14 weeks, the majority were in the range of 330-350 um. The CRL reference range for the adult rabbits using ultrasound pachymetry is 378 ± 27 um. IOP was similar for each age group, ranging from approximately 12-17 mm Hg with the CRL background range in adults using a handheld rebound tonometer averaging 14.8 ± 1.6 mm Hg.
The primary difference between the juvenile Dutch Belted rabbit eyes and adult eyes was the corneal thickness which could be an important consideration when administering a drug formulation to the ocular surface. Early ocular observations were sparse in rabbits aged 6-14 weeks and were primarily corneal in nature. In contrast the adult animals had fewer corneal observations and more lens opacities. IOP was similar between juveniles and adults.
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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