Very-high-frequency ultrasound corneal imaging as a new tool for early diagnosis of ocular surface toxicity in rabbits treated with a preserved glaucoma drug.
OBJECTIVE
To evaluate very-high-frequency (VHF) ultrasound imaging as a new method to detect and quantify early corneal epithelium changes induced by chronic exposure to a benzalkonium-chloride-containing antiglaucoma drug.


METHODS
Timolol preserved with 0.01% benzalkonium chloride solution was applied b.i.d. in 1 eye of 10 rabbits for 56 days. Unpreserved timolol solution was used as control. Ocular surface changes were assessed weekly combining clinical examinations, in vivo 60-MHz ultrasound imaging and ex vivo histological analysis.


RESULTS
VHF ultrasound imaging allowed quantitative measurement of corneal epithelium thickness and qualitative imaging of toxic epithelial damage. It revealed significantly decreased epithelial thickness in vivo as early as the 21st day of treatment (40.75 +/- 1.72 microm at D0 vs. 39 +/- 2 at D21, vs. 31.9 +/- 2.98 at D56; p = 0.017 and p = 0.005, respectively). The first clinical changes appeared from the 42nd day of treatment (conjunctival redness, conjunctival staining and corneal staining; D56 compared to D0: p = 0.005, 0.01 and 0.004, respectively) and then correlated with VHF ultrasound data. Epithelial thickness measured with VHF ultrasound was correlated with histological epithelial pachymetry (p < 0.001) and with the corneal damage score assessed with scanning electron microscopy (p = 0.038).


CONCLUSIONS
VHF ultrasound imaging provided an early in vivo diagnosis of corneal epithelium pathology induced by chronic exposure to a preserved glaucoma drug, before the first clinical evidence of ocular toxicity. It could be a new reproducible method to detect the toxicity of glaucoma medication so that therapy can then be adapted.
Denoyer
Alexandre
A
Department of Ophthalmology, University Hospital of Tours, Tours, France.
Ossant
Frederic
F
Arbeille
Brigitte
B
Fetissof
Franck
F
Patat
Frederic
F
Pourcelot
Léandre
L
Pisella
Pierre-Jean
PJ
D000818:Animals; D000959:Antihypertensive Agents / Q000633:toxicity*; D001548:Benzalkonium Compounds / Q000633:toxicity*; D003229:Conjunctival Diseases / Q000139:chemically induced / Q000000981:diagnostic imaging*; D003315:Cornea / Q000000981:diagnostic imaging* / Q000187:drug effects; D019573:Epithelium, Corneal / Q000000981:diagnostic imaging / Q000187:drug effects; D007634:Keratitis / Q000139:chemically induced / Q000000981:diagnostic imaging*; D008297:Male; D008855:Microscopy, Electron, Scanning; D011310:Preservatives, Pharmaceutical / Q000633:toxicity*; D011446:Prospective Studies; D011817:Rabbits; D011846:Radio Waves; D013999:Timolol / Q000633:toxicity; D014456:Ulcer / Q000139:chemically induced / Q000000981:diagnostic imaging*; D014463:Ultrasonography
D000959:Antihypertensive Agents; D001548:Benzalkonium Compounds; D011310:Preservatives, Pharmaceutical; D013999:Timolol