Efficacy of TonoLab in detecting physiological and pharmacological changes in rat intraocular pressure: comparison of TonoPen and microneedle manometry.
OBJECTIVE
To assess the efficacy of two noninvasive tonometers, TonoLab and TonoPen-XL, in detecting physiological or pharmacological changes of intraocular pressure (IOP) in rat eyes, by comparing them with the microneedle method.


METHODS
Sprague Dawley rats, bred under a 12-h light-and-dark cycle, were used. Under systemic anesthesia, eyes were cannulated by a microneedle connected to a transducer and a water reservoir. Variable intracameral pressure was attained by changing the reservoir height, and the resulting tonometer readings were compared. Then, the daytime and nighttime IOP, and the effect at 2 h after latanoprost instillation, were measured with the three devices.


RESULTS
TonoLab and TonoPen-XL readings (y) were strongly correlated with microneedle tonometer readings (x) (y=0.96x-4.3, r2=0.985, and y=0.48x+3.9, r2=0.985, respectively), but TonoPen-XL readings were only half those of the microneedle tonometer. Nocturnal elevation of IOP was significant both with TonoLab and with the microneedle tonometer (P<0.001), but not with TonoPen-XL. Latanoprost significantly elevated IOP by 3.0+/-2.1 with TonoLab and by 1.1+/-1.1 mmHg with the microneedle tonometer (P<0.05), but not with TonoPen-XL.


CONCLUSIONS
TonoLab provides readings similar to those of a microneedle tonometer, and diurnal variations and drug effects were detectable. TonoLab promises to be a noninvasive and useful method for physiological and pharmacological studies in rat eyes.
Ohashi
Masaaki
M
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan.
Aihara
Makoto
M
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan. aihara-tky@umin.ac.jp.|Department of Ophthalmology, University of Tokyo School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. aihara-tky@umin.ac.jp.
Saeki
Tadashiro
T
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan.
Araie
Makoto
M
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan.
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects; D007429:Intraocular Pressure / Q000187:drug effects* / Q000502:physiology*; D000077338:Latanoprost; D008297:Male; D011461:Prostaglandins F, Synthetic / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014065:Tonometry, Ocular / Q000295:instrumentation / Q000379:methods*
D000959:Antihypertensive Agents; D011461:Prostaglandins F, Synthetic; D000077338:Latanoprost