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Scleral changes induced by atropine in chicks as an experimental model of myopia
Patricia Gallego1, Carmen Martínez-García, Pablo Pérez-Merino
1Department of Cell Biology, Histology and Pharmacology, School of Medicine, University of Valladolid, Valladolid, Spain. patricia.gallego.munoz@uva.es
Insights
Intravitreal atropine treatment in chicks with induced myopia led to significant refractive error recovery. Atropine altered scleral growth, thickening the fibrous layer and thinning the cartilaginous layer, halting ocular growth.
Area of Science:
- Ophthalmology
- Developmental Biology
- Animal Models
Background:
- Myopia, a common vision disorder, is characterized by excessive eye elongation.
- Understanding the mechanisms of scleral growth is crucial for developing myopia control strategies.
- The form-deprived chick model provides a valuable platform for studying myopia development and potential interventions.
Purpose of the Study:
- To investigate the impact of intravitreal atropine on scleral growth and refractive error in a chick model of myopia.
- To determine if atropine can modulate the structural changes in the sclera associated with myopia progression.
Main Methods:
- Chicks were subjected to monocular form deprivation to induce myopia.
- Groups received intravitreal injections of atropine or a control vehicle.
- Refractive error, axial length, and scleral histology (fibrous and cartilaginous layers) were assessed.
Main Results:
- Form-deprived eyes exhibited myopic refractive errors.
- Atropine treatment resulted in hyperopic shifts and statistically significant changes in refractive error.
- Scleral analysis revealed a thickened fibrous layer and thinned cartilaginous layer in atropine-treated eyes compared to controls.
- Axial length changes correlated with refractive error modifications.
Conclusions:
- Intravitreal atropine can reverse myopia and halt ocular growth in this experimental model.
- Atropine induces specific morphological changes in the sclera, including fibrous layer thickening and cartilaginous layer thinning.
- These scleral alterations suggest atropine's mechanism of action involves direct effects on scleral tissue, influencing ocular growth regulation.
Purpose:
To determine the effects of intravitreal atropine on scleral growth in the form-deprived chick as an experimental model of myopia.
Methods:
Five groups of five chicks were studied from day 0-12 post-hatching. One group remained untreated (C), and four were form-deprived by monocular light diffusers to induce myopia. Two groups (RL and A) wore diffusers for 9 days, and the other two groups (D and D + A) wore diffusers throughout the study. Group D received no further treatment (myopia positive control). Groups A and D + A received intravitreal injections of atropine for days 9-12. Measurements of refractive error and axial length were performed on days 0, 9, and 12. Sclera changes were assessed in cartilaginous and fibrous layers by histological analysis.
Results:
All form-deprived eyes had a myopic refractive error on day 9. All atropine-treated groups were hyperopic on day 12. The effect of atropine was most evident in Group D + A in which diffusers were maintained throughout treatment and changes in refractive error were statistically significant. The observed changes in axial length were in line with the changes in refractive error. The scleral fibrous layer thickness increased, and the sceral cartilaginous layer underwent a slight thinning compared to Group D, the myopia positive control.
Conclusions:
If the signals that induce growth remain during atropine treatment, morphological changes in sclera are produced: the scleral fibrous layer thickened, and the sceral cartilaginous layer thinned. These changes resulted in refractive error recovery, and the ocular growth was stopped. The data suggested the atropine was acting throughout the scleral fibrous layer.
