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Effects of hemiretinal form deprivation on central refractive development and posterior eye shape in chicks
Chin-hung Chu1, Li Deng, Chea-su Kee
1School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Special Administrative Region.
Insights
Hemiretinal form deprivation in chicks significantly alters refractive development and eye shape. Superior retinal deprivation (SRD) and inferior retinal deprivation (IRD) showed the most significant refractive differences, impacting axial length to equatorial diameter ratio.
Area of Science:
- Ophthalmology
- Developmental Biology
- Animal Models
Background:
- Form deprivation myopia is a significant research area in understanding refractive error development.
- Hemiretinal form deprivation offers a unique model to investigate the localized effects of visual input on eye growth and refractive state.
Purpose of the Study:
- To investigate the impact of hemiretinal form deprivation on central refractive development and posterior eye shape in chicks.
- To compare the effects of superior, inferior, temporal, and nasal hemiretinal deprivation on refractive error components and eye dimensions.
Main Methods:
- Seventy-seven chicks underwent monocular hemiretinal form deprivation (superior, inferior, temporal, or nasal) from day 5 to day 26.
- Central refractive errors (spherical equivalent, J0, J45) were measured weekly using a Hartinger refractometer.
- Eye shape parameters including axial length (AL) and equatorial diameter (ED) were analyzed post-treatment.
Main Results:
- Hemiretinal form deprivation altered refractive errors and posterior eye shape to varying degrees.
- The greatest refractive difference (M) was observed between superior retinal deprivation (SRD) and inferior retinal deprivation (IRD) groups.
- SRD showed a significantly higher AL/ED ratio compared to IRD and nasal retinal deprivation (NRD) groups, with M significantly correlated with AL/ED ratio.
Conclusions:
- Selective interruption of visual experience in different parts of the visual field influences the mechanisms regulating central ametropia.
- Hemiretinal form deprivation provides insights into the localized control of eye growth and refractive development.
- These findings contribute to understanding the complex interplay between visual input and ocular development.
Abstract:
We determined effects of hemiretinal form deprivation (i.e., form-depriving half of the retina) on central refractive development and posterior eye shape in chicks. Seventy-seven White Leghorn chicks were randomly assigned to receive superior (SRD, "Superior Retinal Deprivation" or inferior visual field deprivation, same principle applies for the following abbreviations, n=17), inferior (IRD, n=14), temporal (TRD, n=23) or nasal hemiretinal (NRD, n=23) form deprivation monocularly from day 5 to day 26. Central refractive errors, expressed as interocular difference in spherical equivalent (M), J0 and J45 astigmatic components, were measured using Hartinger refractometer at the beginning and weekly after treatment for 3weeks. At the end of the treatment period, eyes of a subset of birds were enucleated and eye shape profile was photographed along four different meridians. These digital images were later processed to extract axial length (AL), equatorial diameter (ED), and AL/ED. For comparison purposes, the eye shape profile was also acquired from a separate group of birds reared with monocular full-retinal form deprivation (FRD, n=10). The four hemiretinal form deprivations altered central ametropia and posterior eye shape to different degrees. The biggest contrast in M was found between SRD and IRD groups (mean±SE after 3weeks: SRD=-4.14±0.71 D vs. IRD=+1.24±0.36 D; p<0.05), whereas subtle differences in J0 and J45 components were found across the four treatment groups (both p⩽0.03). SRD group also showed significantly higher AL/ED ratio compared to IRD and NRD groups (0.76±0.05 vs. 0.74±0.07 and 0.75±0.04; both p⩽0.03). Furthermore, M was significantly correlated with AL/ED ratio in the treated eyes of hemiretinal treated chicks (r=-0.55, p<0.001). Our results suggest that mechanism regulating central ametropia can be influenced by selectively interrupting the visual experience at different parts of visual field.
