Effects of muscarinic receptor modulators on ocular biometry of guinea pigs.
OBJECTIVE
This study investigated whether pilocarpine and cyclopentolate induce changes in ocular biometry of guinea pigs, in order to understand if guinea pigs have a similar response to these two agents as humans do.


METHODS
Under general anaesthesia, refraction, axial components and surface curvature in various optical interfaces of the eye were measured in 10 guinea pigs (age of 2 weeks) at baseline (0 min) and different time points (5, 10, 20, 30, 60, 90 min) after topical administration of pilocarpine or cyclopentolate. The interval between the two drug treatments for the same animals was at least 24 h.


RESULTS
Eyes treated with pilocarpine developed approximately 6D myopia (p < 0.001 from 0 to 90 min) with a decrease in anterior lens radius of curvature (ALRC) (p < 0.001 from 0 to 90 min, repeated measures anova). This myopic shift was moderately correlated to the decreased ALRC (r(2)  = 0.48, p < 0.001). Furthermore, a small but significant increase in the VCD (p < 0.001 from 0 to 30 min, repeated measures anova) with an unchanged AL (p = 0.85 from 0 to 90 min, repeated measures anova) after the drug treatment suggested a transient and mild forward movement of the lens. Cyclopentolate dilated the pupil in all eyes (p < 0.001 from 0 to 90 min, repeated measures anova) but did not change other ocular parameters.


CONCLUSIONS
The muscarinic agonist, pilocarpine induced a myopic shift mainly due to a decrease in ALRC, suggesting that guinea pigs have an accommodative mechanism similar to that in humans. The minimal changes produced by cyclopentolate could be due to the use of general anaesthesia, which may have reduced the susceptibility of the eye to topical cyclopentolate in the induction of cycloplegia.
School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Zhejiang, China; State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Ministry of Health P.R. China, Zhejiang, China.
Fang
F
Fang
Furong
F
Huang
Ruozhong
R
Xie
Cheng
C
Li
Yin
Y
Liu
Ying
Y
Zhu
Jia
J
Qu
Xiangtian
X
Zhou
D000065:Accommodation, Ocular / Q000187:drug effects; D000287:Administration, Topical; D000704:Analysis of Variance; D000818:Animals; D000867:Anterior Chamber / Q000187:drug effects; D003519:Cyclopentolate / Q000494:pharmacology*; D004195:Disease Models, Animal; D005123:Eye / Q000187:drug effects*; D006168:Guinea Pigs; D007908:Lens, Crystalline / Q000187:drug effects; D008916:Miotics / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009184:Mydriatics / Q000494:pharmacology; D009216:Myopia / Q000139:chemically induced; D010862:Pilocarpine / Q000494:pharmacology*; D011680:Pupil / Q000187:drug effects; D012029:Refraction, Ocular / Q000187:drug effects; D014822:Vitreous Body / Q000187:drug effects
D008916:Miotics; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D009184:Mydriatics; D010862:Pilocarpine; D003519:Cyclopentolate
accommodation; cyclopentolate; guinea pigs; muscarinic receptors; ocular biometry; pilocarpine