Abstract
To investigate conditions that cause temporal lens opacity, we tested chemical and physical factors, such as anaesthesia dose, ocular surface dryness, and infrared (IR) light exposure in anaesthetised C57BL/6 N mice. Mice were anaesthetised with a low (80%; tiletamine/zolazepam 32 mg/kg and xylazine 8 mg/kg, intraperitoneal injection) or high (120%; 48 mg/kg and 12 mg/kg) dose of anaesthetic and examined every 5 min from 10 to 30 min after anaesthesia was induced. Lens opacity levels were assessed and graded (1–6) using the standard classification system. Regardless of the anaesthetic dose, lens opacity grade was 1–2 in moisturised eyes with application of 0.5% carboxymethylcellulose, and 5–6 in dry ocular surface conditions. Lens opacity in mice with high-dose anaesthetic in the dry ocular surface condition was not different from that of mice with low-dose anaesthetic. Lens opacity grade 1–2 was noted in eyes in the wet ocular surface condition, regardless of IR light exposure. During IR light exposure in eyes in the dry ocular surface condition, lens opacity (grade 6) in mice with high-dose anaesthetic was not different from that (grade 6) in mice with low-dose anaesthetic. We demonstrated that ocular surface dryness might be a relevant factor for the formation and progression of lens opacity in anesthetized C57BL/6 N mice. Anaesthesia dose and IR light exposure did not strongly influence lens opacity formation. Furthermore, eyes with corneal dryness-induced lens opacity recovered to normal status without additional intervention.
Highlights
During observation of the posterior segment of the eye, transparency of the ocular media is essential, because opaque medium, especially lens opacity, significantly affects accuracy and results of measurement
Effect of anaesthetic dose on lens opacity formation in wet ocular surface condition To evaluate degrees of lens opacities resulting from various factors, we collected sample pictures from all image data and established classification standards consisting of six grades of lens opacity
A modified visual classification system of progressive lens opacity was used to assess the severity of lens opacity on the basis of six grades of lens opacity, from grade 1 to grade 6, all of which were based on images obtained from optical coherence tomography (OCT) and slit-lamp biomicroscopy examinations
Summary
During observation of the posterior segment of the eye, transparency of the ocular media is essential, because opaque medium, especially lens opacity, significantly affects accuracy and results of measurement. Lens opacity is induced by genetic, developmental, and environmental cues. 90 genes were annotated as associating with abnormal lens morphology in the International Mouse Phenotyping Consortium. Because many genes have been annotated as associating with lens abnormalities, there is a need to determine the various factors causing them. It has been reported that various chemical and physical factors, including drugs, anaesthetics, oxygen supply, calcium, pH stress, and dehydration, affect the formation of lens opacity in mice and rat [1,2,3,4]. There is a consensus that anaesthetic dose, dehydration, and temperature are the most important factors affecting the formation of lens opacity, a precise explanation for the interrelationship of these factors remains ambiguous [1, 5, 6]
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