Retina-Subcortex Pathway Deficit In Adult Patients With Amblyopia

Part 1:The structural and functional changes of retina in adult patients with amblyopiaObjective:To investigate the changes of retinal thickness and P-ERG in adult patients with strabismic or anisometropic amblyopia.Methods:30 cases of monocular adult amblyopia patients who visited the outpatient clinic of The Eye&ENT Hospital of Fudan University,between June 2014 to November 2014 were collected.Each of the anisometropic amblyopia(anisometropic amblyopia,AA,aged 18 to 34 years)group and strabismic amblyopia(strabismic amblyopia,SA,aged 18 to 42 years)group,contained 15 cases.Retinal nerve fiber layer(RNFL)thickness was measured within 3.4mm diameter range surrounding the optic nerve,and ganglion cells composite layer(GCC)thickness within 6mm diameter range surrounding the fovea in all amblyopic and contralateral healthy eyes with the Optovue RTVue OCT.Roland electrophysiology instrument was also employed to record the amplitude and latency of P50 and N95 in PERG under two different stimulation conditions(respectively stimulate the parvocellular pathway and magnocellular pathway).Data between amblyopic and fellow eyes were statistically analyzed by using paired t test,Person correlation test were used in analyzing the correlation between axial length and indexes in OCT and P-ERG.Results:(1)Changes in RNFL thickness:in anisometropic amblyopia group,temporal quadrant thinned(t=-2.353,p= 0.033),while in the nasal,superior and inferior 3 quadrants incrassated;(p<0.05)in amblyopic eyes compared with fellow eyes;in strabismic amblyopia group,compared with contralateral healthy eyes,there were not a statistically significant difference(each quadrant p>0.05)in amblyopic eyes.(2)Changes in GCC thickness:in anisometropic amblyopia group,GCC layer thickness increases(t = 2.246,p = 0.039)in amblyopic eye compared with the contralateral healthy eye;while we did not find statistically significant difference between amblyopic eyes and contralateral healthy eyes in strabismic amblyopia group(p>0.05).(3)P-ERG under the parvocellular pathway stimulated mode:in anisometropic amblyopia group,amplitude of P50(t =-3.329,p = 0.004)and N95(t=-2.235,p = 0.038)decreased in amblyopic eye compared with contralateral healthy eyes,but no statistically significant latent time difference(p>0.05)can be found when compared with contralateral healthy eyes.In the same stimulus pattern,no statistically significant difference(p>0.05)can be found in amplitude and latency of P50&N95 in strabismic amblyopia group when compared with the contralateral healthy eye.(4)P-ERG under the magnocellular pathway stimulated mode:amplitude and latency of P50&N95 showed no statistically significant difference(P>0.05)in both anisometropic amblyopia group and strabismic amblyopia group,when compared with contralateral healthy eyes.(5)We found no significant correlation between axial length and OCT,P-ERG indicators(P>0.05).Conclusion:The results of this study show that there are changes in structure and function of retina in adult anisometropic amblyopia,and this change maybe mainly manifested as a damage of a part of ganglion cell that in charge of the parvocellular pathway.While in adult strabismic amblyopia,the structure and function of retina in their amblyopic eye did not change significantly.And those may because these two types of amblyopia might be generated under different pathological mechanismsPart 2:The functional change of Magnocellular and Parvocellular pathway in adult patients with amblyopiaObjectives:Using fMR1 to explore the functional loss of subcortical nuclei in adult amblyopiaMethods:Seventeen adult patients diagnosed with unilateral amblyopia(ten anisometropic and seven strabismic amblyopia patients)and twelve healthy,matched controls were enrolled in our study.Lateral geniculate body(LGN)was selected as ROIs to investigate the functional status of the subcortical pathways.The M and P stimuli were used to segment the M and P layers of the LGN.The M stimulus was a low-spatial-frequency sine wave checkerboard counter-phase flickering at a high temporal frequency with low luminance contrast,while the P stimulus was high-spatial-frequency isoluminant red/green square wave checkerboard with reverse contrast at a low temporal frequency.MRI data were collected with a 3T scanner at the Eye and ENT Hospital of Fudan University using a twelve-element Head Matrix coil.The fellow eye and the amblyopic eye of each subject were examined in separate sessions.The MRI data were analyzed using Brainvoyger QX and custom codes.The ROIs of the LGN were defined based on the activation map of the hemi-field localizer and T1 anatomical images.The beta values of various stimuli conditions were fitted and extracted with general linear models.The M layer of the LGN was identified as a section of the voxels showing a stronger response to the M stimulus than to the P stimulus,and the reverse principal was used for the identification of the P layerResults:From the activation pattern of the LGN in the normal group,the M layer was located more medially,interiorly,and anteriorly as compared to the location of the P layer,which is consistent with the anatomy of the human anatomic LGN.In the P layer of the LGN,a significant interaction was found between the factors of stimuli and subject groups(normal eyes/amblyopia eyes,amblyopia eyes/fellow eyes)but no such significant interaction was seen in the M layer.An independent-sample test showed that the fMRI response to the P stimulus in the P layer was significantly reduced in the amblyopic eye group,while there were no significant signal changes in response to the M stimulus.Both the anisometropic and strabismic amblyopia groups showed the same trends.These results indicated that neural responses to the M and P stimuli are selectively reduced in the LGNs of amblyopic subjects,who experienced a greater loss of signals in response to the P stimulus only in the P layers due to amblyopic damageConclusions:Using fMRI and custom stimuli to sketch the two parallel pathways’functions,we demonstrated the clear segregation of the M and P divisions in the LGN noninvasively in normal and adult amblyopia patients.The amblyopic eyes demonstrated a selective loss in the P layer of LGN,with a relatively intact retino-tectal pathway.