Background/Purpose: In a method evaluating conjunctival hyperemia using rabbits, it is common to visually grade the degree of vasodilation. However, this method is limited in evaluating consecutive value and in reproducibility. We quantified the degree of conjunctival hyperemia in rabbits as the area ratio of blood vessels by image analysis, and compared the vascular area percentage calculated by image analysis with the hyperemia score.

Methods: The conjunctiva was photographed before and after the instillation of 0.1% arachidonic acid using a digital medical scope VersaCam^® (Nidek Co., Ltd.). Next, the area of the conjunctival blood vessels occupying the area of interest was calculated using hyperemia analysis software. The hyperemia score was visually graded for the degree of conjunctiva vasodilation. Furthermore, the hyperemia score and the vascular area ratio were compared.

Results: Fifteen minutes after the instillation of arachidonic acid, the area ratio of the blood vessels in the conjunctiva increased significantly and gradually decreased over time. This trend correlated with the hyperemia score.

Conclusion: We found that the degree of conjunctival hyperemia in rabbits can be evaluated numerically and quantitatively. This method is considered to be useful for evaluating conjunctival hyperemia in allergic conjunctival diseases.

Although an important cause of vocal cord dysfunction (VCD) is psychogenic reaction, VCD may be associated with severe asthma and must be distinguished from the disease. A 30-years-old woman was admitted to our hospital with dyspnea despite treatment for asthma. Inspiratory stridor and expiratory wheezes were noted, and neck and chest computed tomography showed normal airways and lungs. Fractional exhaled nitric oxide levels were also normal. Pulmonary function test with a flow-volume loop curve showed normal expiratory loop with flattening of the inspiratory loop after methacholine inhalation. During the attack, bronchoscopy revealed the vocal cord closing with stridor during the inspiratory phase. Therefore, the patient was diagnosed with VCD. The dyspnea improved with respiratory rehabilitation and pursed-lip breathing. VCD should be considered in the differential diagnosis of intractable severe asthma. In this case, bronchoscopy and bronchial inhalation challenge with methacholine helped in the diagnosis.