Photography-based method for assessing fluorescein clearance test in dogs

Arianne Pontes Oriá,Lionel Sebbag,Miriam Flores Rebouças,Francisco De Assis Dórea Neto,Emanoel Martins Filho,Ana Cláudia Raposo

doi:10.1186/s12917-018-1593-y

Arianne Pontes Oriá, Lionel Sebbag + Show 4 more

Open Access

https://doi.org/10.1186/s12917-018-1593-y

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Abstract

BackgroundThe fluorescein clearance test (FCT) provides insight into the tear film dynamics. The purpose of this study was to describe an inexpensive and practical method for assessing FCT in dogs, using photography and software analysis, and to assess the retention time of 1 vs. 2 eye drops on the canine ocular surface.Methods(i) In vivo - Eight healthy German Shepherd dogs were recruited. Following topical anesthesia with 0.5% proxymetacaine, each eye sequentially received (1 week apart) either 1 drop (35 μL) or 2 drops (70 μL) of 0.5% fluorescein. A Schirmer strip was inserted in the ventral conjunctival fornix for 10 s at the following times: each 10 min for 100 min, 24 h, 48 h and 72 h. (ii) In vitro - Schirmer strips were placed for 10 s in contact with microplate wells containing 1 or 2 drops of 0.5% fluorescein. In both experiments, the fluorescein-impregnated Schirmer strips were immediately imaged, and the area and intensity of fluorescein uptake were analyzed with ImageJ software. For the in vitro experiment, images were evaluated by the same examiner (repeatability) or two examiners (reproducibility).ResultsPhotography-based FCT was easy to perform and showed high repeatability and reproducibility (coefficients of variation ≤2.75%). In vivo, the area and intensity of fluorescein uptake on Schirmer strips were significantly greater at 30 min and 40 min post- fluorescein instillation in the 2 drops vs. 1 drop groups (p ≤ 0.044). Compared to baseline, the residual fluorescein uptake on Schirmer strips was < 5% at 60 min and 90 min in the 1 drop and 2 drops groups, respectively.ConclusionsPhotography-based FCT is a practical and reliable diagnostic tool with various clinical and research applications in veterinary medicine. Instillation of two drops provided greater amount and longer retention on the anesthetized canine ocular surface than a single drop. Fluorescein clearance time of a single drop in dolichocephalic dogs is 60 min.

Highlights

The fluorescein clearance test (FCT) provides insight into the tear film dynamics
A drop of 0.5% proxymetacaine hydrochlorid5 was instilled in each eye, and after removing the excess solution with a sterile swab, Schirmer tear test II
At 72 h, none of the Schirmer strips had fluorescein uptake, indicating that 3-day washout period is a minimum for FCT in dogs

Summary

Introduction

The fluorescein clearance test (FCT) provides insight into the tear film dynamics. The purpose of this study was to describe an inexpensive and practical method for assessing FCT in dogs, using photography and software analysis, and to assess the retention time of 1 vs. 2 eye drops on the canine ocular surface. Tears are secreted by the lacrimal glands, spread onto the corneo-conjunctival surface, either evaporate, absorb into tissues of the ocular surface, or drain through the nasolacrimal duct. Together, these physiological aspects (secretion, distribution, turnover and elimination) are termed ‘tear film dynamics’. FCT relies on measuring the decay of fluorescein in the tear film over a period of time. It is often performed with a commercial fluorophotometer device that can quantify fluorescein concentrations in a sensitive manner [2]. It involves photography of Schirmer strips to monitor dye disappearance, and has been reported to have

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