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Lymphatic sinusoids exist in chick but not in rabbit choroid
B M Junghans1, S G Crewther, D P Crewther
1School of Optometry, University of New South Wales, Sydney, Australia. B.Junghans@unsw.edu.au
Summary
Choroidal lymphatics, previously thought absent, show species-specific differences. Chickens possess lymphatic sinusoids, while rabbits have vacuoles, impacting fluid and metabolite management.
Area of Science:
- Ophthalmology
- Comparative Anatomy
- Vascular Biology
Background:
- The choroid, a vascular layer in the eye, is traditionally considered avascular regarding lymphatic drainage.
- Emerging evidence suggests the presence of lymphatic-like structures in the choroids of certain species.
Purpose of the Study:
- To investigate and compare the ultrastructure of the outer choroid in chicks and rabbits.
- To determine the presence and nature of lymphatic-like structures in the choroid across different species.
Main Methods:
- Comparative ultrastructural analysis of chick and rabbit outer choroid.
- Microscopic examination focusing on non-vascular areas of the choroid.
Main Results:
- Significant ultrastructural differences were observed in the non-vascular choroid between chicks and rabbits.
- Chick choroids exhibit large lymphatic sinusoids.
- Rabbit choroids contain a system of large vacuoles within fibroblast processes, not true lymphatic vessels.
Conclusions:
- The findings challenge the notion of absent choroidal lymphatics, revealing species-specific variations.
- These differences raise questions about interspecies similarities in managing retinal metabolites and tissue fluid.
- Choroidal homeostasis mechanisms may differ significantly between species, particularly under overload conditions.