Changes in Amblyopia Using Optical Coherence Tomography

Study Overview
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Brief Summary
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There have been multiple trials to investigate the morphological changes in the macula and retinal nerve fiber layer of amblyopic eyes, due to the different published results and the lack of evident association between these changes and the patients' parameters. So, we perform this study to compare the variations in macular parameters (central thickness, average thickness, macular volume) and peripapillary thickness in different cases of amblyopic eyes versus the normal fellow eyes using spectral-domain optical coherence tomography. In addition, to estimate the relationship of optical coherence tomography variations with different defined patients' parameters (age, sex, best corrected visual acuity, spherical equivalent refractive error, and axial length).

Detailed Description
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Amblyopia remains an important cause of low visual acuity,affecting 2% to 6% of the general population. Unilateral amblyopia is defined as reduced best-corrected visual acuity secondary to an abnormal visual experience during the critical period of visual development. Classic causes include strabismus, anisometropia, form deprivation or a combination of these factors . The normal postnatal reduction (apoptosis) of retinal ganglion cells is arrested in amblyopia which would cause increase in retinal nerve fiber layer thickness as hypothesized by Yen et al .This also would affect the normal maturation of the macula, including movement of Henle's fibers away from the foveola. This would result in increased foveal thickness. Furthermore, because of the reduced apoptosis of retinal ganglion cells, the thickness of the ganglion cell layer in the macula would also be increased. Optical coherence tomography : is a non-contact and non-invasive technique that help in assessment of retina abnormalities. The high resolving power (10um - Time Domain, 5um - Spectral Domain) provides excellent detail for evaluating the vitreo-retinal interface, neurosensory retinal morphology, and the retinal pigmented epithelial-choroid complex. It generates cross sectional images by analyzing the time delay and magnitude change of low coherence light as it is backscattered by ocular tissues. An infrared scanning beam is split into a sample arm (directed toward the subject) and a reference arm (directed toward a mirror). As the sample beam returns to the instrument it is correlated with the reference arm in order to determine distance and signal change via photodetector measurement. The resulting change in signal amplitude allows tissue differentiation by analysis of the reflective properties, which are matched to a false color scale. As the scanning beam moves across tissue, the sequential longitudinal signals, or A-scans, can be reassembled into a transverse scan yielding cross-sectional images, or B-scans, of the subject. The scans can then be analyzed in a variety of ways providing both empirical measurements (e.g. retinal thickness/volume) and qualitative morphological information.

Official Title
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Macular and Retinal Changes in Unilateral Amblyopia Using Optical Coherence Tomography

Conditions
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Amblyopia

Intervention / Treatment
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* Device: optical coherence tomography


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age>16 and <40 years Patients with unilateral amblyopia ( anisometropic , strabismic and deprivational amblyopia ) . Exclusion Criteria: Age<16 and >40 years. Patients with structural abnormality in their eye , mentally retarded patients .

Ages Eligible for Study
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Minimum Age: 16 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| anisometropic amblyopia<br> | Device: optical coherence tomography<br>* It generates cross sectional images by analyzing the time delay and magnitude change of low coherence light as it is backscattered by ocular tissues. An infrared scanning beam is split into a sample arm and a reference arm. As the sample beam returns to the instrument it is correlated with the reference arm in order to determine distance and signal change via photodetector measurement. The resulting change in signal amplitude allows tissue differentiation by analysis of the reflective properties, which are matched to a false color scale. As the scanning beam moves across tissue, the sequential longitudinal signals, or A-scans, can be reassembled into a transverse scan yielding cross-sectional images, or B-scans, of the subject. The scans can then be analyzed in a variety of ways providing both empirical measurements (e.g. RNFL or retinal thickness/volume) and qualitative morphological information.<br>|
| strabismic amblyopia<br> | Device: optical coherence tomography<br>* It generates cross sectional images by analyzing the time delay and magnitude change of low coherence light as it is backscattered by ocular tissues. An infrared scanning beam is split into a sample arm and a reference arm. As the sample beam returns to the instrument it is correlated with the reference arm in order to determine distance and signal change via photodetector measurement. The resulting change in signal amplitude allows tissue differentiation by analysis of the reflective properties, which are matched to a false color scale. As the scanning beam moves across tissue, the sequential longitudinal signals, or A-scans, can be reassembled into a transverse scan yielding cross-sectional images, or B-scans, of the subject. The scans can then be analyzed in a variety of ways providing both empirical measurements (e.g. RNFL or retinal thickness/volume) and qualitative morphological information.<br>|
| deprivational amblyopia<br> | Device: optical coherence tomography<br>* It generates cross sectional images by analyzing the time delay and magnitude change of low coherence light as it is backscattered by ocular tissues. An infrared scanning beam is split into a sample arm and a reference arm. As the sample beam returns to the instrument it is correlated with the reference arm in order to determine distance and signal change via photodetector measurement. The resulting change in signal amplitude allows tissue differentiation by analysis of the reflective properties, which are matched to a false color scale. As the scanning beam moves across tissue, the sequential longitudinal signals, or A-scans, can be reassembled into a transverse scan yielding cross-sectional images, or B-scans, of the subject. The scans can then be analyzed in a variety of ways providing both empirical measurements (e.g. RNFL or retinal thickness/volume) and qualitative morphological information.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| To measure retinal layers and macular thickness changes in cases of unilateral amblyopia using optical coherence tomography in comparison with the other sound eye. | Foveal thickness (mean thickness in the central 1000-μm diameter area) and central foveal thickness (mean thickness at the point of intersection of 6 radial scans) are 212 ± 20 and 182 ± 23 μm, respectively. Macular thickness measurements were thinnest at the center of the fovea, thickest within 3-mm diameter of the center, and diminished toward the periphery of the macula. The temporal quadrant was thinner than the nasal quadrant. | from october 1st 2019 to october 1st 2020 |