The Prevalence of Primary Open-Angle Glaucoma-Like Features in a Rhesus Macaque Colony from Southern China

Abstract

Purpose : To describe the ocular phenotype of spontaneous glaucoma in a primate colony.

Methods : 722 Rhesus macaque monkeys (338 male, 384 female) from the Primed Monkey Research center at Sichuan Province, China, aged 10-25 (equivalent to 30-75 human years) underwent fundus photography and manual assessment of vertical cup-disc ratio (CDR). Monkeys with CDR >95^thpercentile for the cohort (CDR≥0.5) as well as subsets of monkeys with smaller CDR underwent further testing with conscious IOP measurements using the Icare tonometer (N=108 monkeys) and retinal nerve fiber layer (RNFL) measurements with Heidelberg Ocular Coherence Tomography (OCT) (N=77). Definite glaucoma was defined as sectoral peripapillary RNFL thickness less than age-matched controls at the p<0.01 level on two separate occasions. Suspect glaucoma was similarly defined at the p<0.05 level at one time point. Unpaired t-tests were used for making various comparisons.

Results : Mean age of the colony was 14.4±3.1 years while the 13 monkeys with definite (N=8) or suspect glaucoma (N=5) were 16.4±4.3 years (p=0.29). The average CDR OD for the entire colony was 0.38±0.07 versus 0.62±0.12 in affected cases (p=2.0X10^-6) (figure 1). The mean baseline IOP OD of affected (N=13) versus unaffecteds (N=108) was 17.2±3.5 mmHg and 14.0 ± 3.0 mmHg, respectively (p=0.00015). All monkeys with glaucoma had unremarkable slit lamp exams and open angles based on anterior segment OCT. Six affected monkeys were from the same family. Three monkeys with glaucoma showed definite progressive RNFL thinning over a 2-year period based on follow-up OCT reports (figure 2). All RNFL sectors on the circumpapillary OCT OD were significantly reduced (N=13) versus scans from unaffected monkeys (N=77) (p<0.00082). Findings were similar in the left eye.

Conclusions : Members of a nonhuman primate colony exhibit several ophthalmic features of human primary open angle glaucoma (POAG), offering an unprecedented opportunity to more fully understand the natural history of POAG.

This is a 2020 ARVO Annual Meeting abstract.

 

Fundus photos of A. 15 year old non-glaucoma monkey. IOP = 13 mmHg OD and 10 mmHg OS. B. 16 year old glaucoma monkey. IOP = 23 mmHg OD and 24 mmHg OS. NFLD=nerve fiber layer defect; C=cup; D=disc

 

A. OCT report of the non-glaucoma monkey in fig. 1A showing normal RNFL thickness. B. OCT serial report of the same glaucoma monkey in fig. 1B showing progressive thinning in the superior temporal quadrant.