Birefringence Analyses Reveal Differences in Supramolecular Characteristics of Corneal Stromal Collagen Fibrils Between Falconiformes and Strigiformes.

This study aimed to assess the birefringent properties of corneal stromal collagen fibrils in birds of the orders Falconiformes (diurnal) and Strigiformes (predominantly nocturnal) to compare their supramolecular organizations. In total, 22 corneas of Falconiformes (Caracara plancus, n = 8; Rupornis magnirostris, n = 10; and Falco sparverius, n = 4) and 28 of Strigiformes (Tyto furcata, n = 16; Pseudoscops clamator, n = 6; and Athene cunicularia, n = 6) were processed histotechnically into 8-µm thick sections. Corneal optical retardation (OR) values related to the form and intrinsic fractions of the total birefringence of collagen fibrils were measured using a polarized light microscope equipped with phase compensators. In addition, the coherence coefficients that inform the local orientation of the fibrils were calculated through video image analysis. All assessments were conducted both in the anterior and posterior stroma of the cornea. Differences were significant when P < 0.05. The results showed supraorganizational differences between fibrils in the anterior stroma of Falconiformes and Strigiformes. The OR values were greater (P < 0.0001) for Falconiformes, indicating that the corneas of these birds contain more collagen fibrils or more aggregated collagen fibrils. In contrast, the coherence coefficients were higher (P = 0.016) for Strigiformes, indicating that the corneal collagen fibers in these birds are highly aligned and have few undulations. A multivariate data matrix constructed for Euclidean distance calculations showed that the dissimilarity between Falconiformes and Strigiformes corneas, in terms of the supraorganization of stromal collagen fibrils, was 4.56%. In conclusion, it is possible that the supraorganizational differences reported in this study may be sources of variation in the visual quality of Falconiformes and Strigiformes. This study provides the necessary evidence to encourage further research associating corneal optical performance to supramolecular characteristics of corneal stromal collagen.

Tear meniscometry test in wild animals / Teste de meniscometria lacrimal em animais silvestres

ABSTRACT: This study aimed to describe strip meniscometry test values for Amazona aestiva (turquoise-fronted amazon), Ara ararauna (blue-and-yellow macaw) and Caiman latirostris (broad-snouted caiman). Twenty-one Amazona aestiva and 11 Ara ararauna, healthy, adults of unknown sex, and 37 healthy adult Caiman latirostris (27 males and 10 females), were used in this investigation. All animals were manually restrained and I-Tear® Test strip was inserted for 5 s at the edge of the lower tear meniscus, without touching the eyelid or ocular surface, immediately followed by measurement (millimeter per 5 seconds). No differences were reported between left and right eyes for Amazona aestiva (P = 0.824), Ara ararauna (P = 0.262) and Caiman latirostris (P = 0.679). Median and confidence interval were 2.0 (2.25-3.56) mm/5s for Amazona aestiva, 3.0 (2.93-4.15) mm/5s for Ara ararauna and 3.0 (2.55-4.90) mm/5 s for Caiman latirostris. These values for strip meniscometry tear test can be used as parameters for each species and may be helpful for diagnosis and treatment of tear-production disorders in birds and reptiles.

RESUMO: O objetivo deste estudo foi descrever os valores do teste de meniscometria lacrimal para Amazona aestiva (papagaio-verdadeiro), Ara ararauna (arara-canindé) e Caiman latirostris (jacaré-de-papo-amarelo). Vinte e um Amazona aestiva, 11 Ara ararauna adultos, de sexo desconhecido, e 37 Caiman latirostris adultos (27 machos e 10 fêmeas), foram utilizados nesta investigação. Todos os animais foram contidos manualmente e uma tira do I-Tear® test foi inserida por 5 segundos na borda do menisco inferior, sem tocar a pálpebra ou a superfície ocular, e imediatamente mensurada (milímetro por 5 segundos). Não foram encontradas diferenças entre os olhos esquerdos e direitos para Amazona aestiva (P = 0,824), Ara ararauna (P = 0,262) e Caiman latirostris (P = 0,679). Mediana e intervalo de confiança foram de 2,0 (2,25-3,56) mm/5 s para Amazona aestiva, 3,0 (2,93-4,15) mm/5 s para Ara ararauna e 3,0 (2,55-4,90) mm/5 s para Caiman latirostris. Estes valores para o teste de meniscometria podem ser utilizados como parâmetros para estas espécies e podem ser úteis para diagnosticar e tratar distúrbios de produção lacrimal em aves e répteis.