Correlation Between Visual Function Evaluated By MAIA And Retinal Vascular Network Alterations Measured By OCTA In Nonpathological High Myopia

Myopia is a public health concern in many parts of the world.Although myopia can be easily managed with an appropriate optical correction,it is a risk factor for a number of retinal pathologies,especially in high myopia(>-6.0 diopter),and may cause permanent visual impairment or even blindness.As the severity of myopia is increased,excessive axial elongation of the globe exerts a biomechanical stretch on the posterior pole,leading to pathological changes of the eye,such as macular hemorrhage,choroidal neovascularization(CNV),chorioretinal atrophy,and macular hole with or without retinal detachment.Studies in recent years have focused on the structural and functional changes of the retina in high myopia.Optical coherence tomography has been used to identify subtle anatomical changes in people with myopia,and the correlation of regional variation in the macular thickness and spherical equivalent(SE),axial length(AL)in myopic eyes has been well recorded.Electroretinogram(ERG)testing,including multifocal(mf)ERG,has shown decreased b-wave amplitudes with increased AL in eyes affected by non-pathologic myopia,indicating the functional disorder or depression of the visual cells.Microperimetry(MP)advancements have facilitated the functional assessment in the whole macular region,and not only retinal sensitivity(RS)but also the quantification of fixation stability(FS,including P1,P2,BCEA@63%,BCEA@95%),which may be better indicators of practical visual capabilities for patients with macular dysfunction.As a novel device that utilizes scanning laser ophthalmoscope technology,the MAIA(macular integrity assessment)system has recently been introduced into clinical practice.MAI A measures RS using 61 or 37 Goldmann-style stimulus points within a 10-degree meridional grid centered on the fovea.It uses an automated eye tracking system that corrects 25 times per second to compensate for eye movements and/or poor fixation.Previous studies have assessed RS and different FS indicators in several visual field(VF)defects using MAIA MP,but the differences in RS and FS measured by MAI A MP between highly myopic and nonmyopic subjects have not been fully discussed.Optical coherence tomography angiography(OCTA),is a noninvasive,quick and convenient diagnostic instrument that can evaluate vessel network in retina structure.This device has been used to measure retinal blood flow velocity in several common ocular diseases,but the application in myopia research need to be extensively discussed.The goal of the present study was to characterize the retinal microvasculature parameters including FAZ,GCC and RNFL in high myopia using OCTA and to correlate it with the functional changes detected with MAIA.Using these two advanced devices,the goal of the present study was to characterize the retinal microvasculature in high myopia using OCTA and to correlate it with the functional changes detected with MAIA,and to attempt to quantify the relationship between functional and anatomical derangements in high myopia.PURPOSETo analyze macular function by using MAIA MP parameters and the morphological features of foveal photoreceptors;to evaluate the FAZ area and perifoveal capillary network density in the high myopia,and to compare the findings to those of normal individuals using OCTA;to assess the association between morphological alterations and functional deficits as measured by OCTA and MAIA MP in patients in high myopia.METHODS1.128 Patients from the Qilu Hospital of Shandong University and volunteers from Shandong University were recruited in the present study from July 2016 to March 2017.Each subject underwent a thorough ophthalmic examination at the start of the study,including determination of best corrected BCVA,SE,IOP by Goldmann applanation tonometry,slit-lamp examination,color fundus photography,and AL using an IOL Master.2.All subjects underwent a thorough ophthalmic examination,including mean RS,FS(including P1,P2,BCEA@63%,BCEA@95%),macular integrity(MI),and examination time,using MAIA.3.The foveal avascular zone(FAZ)size,the retinal nerve fiber layer(RNFL)thickness,and the macular ganglion cell complex(GCC)thickness were determined by OCTA,and correlations of the main outcomes were analyzed.RESULTS1.A total of 128 eyes from 128 subjects were enrolled in the present study,in which 73 eyes were from females and 55 eyes were from males.The age of participants ranged from 20 to 54 years old(30,72 ± 7.52).The mean SE of highly myopic subjects was-7.45± 1.74 D,and it was-0.87 ± 0.71 D in control eyes.The mean AL of highly myopic subjects was 26.89 ± 0.89 mm,and it was 22.63 ± 0.38 mm in control eyes.The mean BCVA of highly myopic subjects was 0.90 ± 0.14,and it was 0.99 ± 0.03 in control eyes.The mean IOP of highly myopic subjects was 15.94 ± 2.67 mmHg,and it was 16.01 ± 3.45 mmHg in control eyes.2.The mean retinal sensitivity and fixation pattern were evaluated by MAIA,and the results were summarized in table 2.The RS of the 88 highly myopic eyes(28.59 ±1.26 dB)was significantly decreased as compared with control eyes(29.97 ± 0.79 dB,t=6.38,P<0.0001).The P1 and P2 were 93.49%± 7.28%and 98.02%±3.44%in highly myopic eyes,respectively,and they were 96.13%± 4.18%and 99.13%± 1.40%in control eyes,respectively.The average areas of BCEA@63%and BCEA@95%in highly myopic eyes were 1.32 deg2 and 3.92 deg2,respectively,and they were 0.66 deg2 and 1.96 deg2 in control eyes.BCEA@63%and BCEA@95%were significantly increased in highly myopic eyes as compared with the control group(t=-2,41,P=0.0176;t=-2.38,P=0.0190),while P1 and P2 were reduced in highly myopic eyes as compared with the control group(t=2.13,P=0.0348;t=1.95,P-0.0535).Meanwhile,Macular integrity(MI)was significantly increased in highly myopic eyes as compared with control eyes(31.67 ± 25.93 vs.10.37 ± 11.36,t=-4.98,P<0.0001).The mean examination time was significantly longer in the highly myopic group(300.20 sec)as compared with the control group(285.2 sec,t=-2.36,P=0.0199).3.The mean RS showed a significant negative correlation with SE(r=0.40709,P<0.0001)and AL(r=-0.3182,P=0.0025),while it was not correlated with IOP(r=0.00296,P=0.9782).In addition,the mean RS showed a positive correlation with BCVA(r=0.26258,P=0.0135),and the higher the visual acuity,the greater the RS.The FS at P1 and P2 exhibited a significant negative correlation with SE and AL(P1:r=0.3341,P=0.0015;r=-0.3493,P=0.0009;r=-0.2840,P=0.0073;P2:r=0.2319,P=0.0297,r=-0.25354,P=0.0172;r=-0.2710,P=0.0106).The FS at BCEA@63%and BCEA@95%showed a considerable positive correlation with SE and AL(BCEA@63%:r=-0.3285,P=0.0018 r=0.3350,P=0.0014;r=-0.3483,P=0.0009;BCEA@95%:r=0.3343,P=0.0015,r=0.3400,P=0.0012;r=-0.3507,P=0.0008).We also observed a significant negative correlation between RS and MI,BCEA@63%,BCEA@95%or mean examination time;a positive correlation between RS and P1 or P2;a significant positive correlation between MI and SE or AL;and a negative correlation between MI and P1 or P2.No significant difference was found in sex or age distribution between the groups(X2=2.602,P=0.1067;t=1.14,P=0.2576)4.Macular vascular variables were analyzed using the OCTA system.The FAZ area was 0.35 ± 0.09 mm2 in the high-myopia group,which was significantly different from that of the control group(0.30 ± 0.07 mm2;P =0.0068).Macular vessel density was defined as the percentage of the sample area occupied by vessel lumens following binary reconstruction of images,which was separately calculated in following regions,including foveal,temporal parafoveal,superior parafoveal,nasal parafoveal,and inferior parafoveal.There was a trend of vessel density reduction in participants with high myopia,but without statistically significant differences between these sectors in the two groups(Fovea,P =0.1298,Parafovea,P =0.2344,Temporal,P =0.0563,Nasal,P =0.7263,Super,P =0.3074,Inferior,P =0.3106).Macular GCC were also investigated here.The GCC thickness measured 98.22 ± 5.04 μm in the high-myopia group,significantly lower than that in the control participants(102.48 ± 2.72 μm,P<0.0001).Meanwhile,the RNFL was marginally thinner in the high-myopia participants(98.37 ± 8.36 μm)when compared with the control participants(113.78±10.91μm,P<0.0001).Central corneal thickness(CCT)mean values were 545.60±25.63 μm in the high-myopia group,as compared to 554.43 ± 26.02 μm in the control group,and the average CCT did not indicate any significant difference between two groups.(p=0.0748).5.In the high-myopia group,the thicknesses of macular GCC,as a reflection of retinal neural loss,along with the FAZ as a reflection of optic vessel damage,were selected for analysis,using the visual function parameters including SE,AL,RS,BCEA@63%,and BCEA@95%(Table 4).The mean FAZ showed significant negative correlations with SE(r=-0.39 1 8,P=0.0002),AL(r=0.2277,P=0.0329),and RS(r=-0.2489,P=0.0193),while it was not correlated with BCEA@63%(r=0.0421,P=0.6966)or BCEA@95%(r=0.0469,P=0.6646)(Figure 1).The mean GCC showed negative correlations with BCEA@63%(r=-0.2291,P=0.0318)and BCEA@95%(r=-0.2354,P=0.0273).Relationships between GCC and SE,AL,and RS were nonsignificant(r=-0.14673,P=0,1725,r=0.06626,P=0.5396,r=0.04264,P= 0.6933).CONCLUSION1.The progress of axial length elongation and vision decline in myopia result in enlarged FAZ area,reduced RS and FS ability.2.Retinal sensitivity and fixation stability work as the surrogate markers of visual function in high myopia,which were negatively correlated with visual ability.3,Changes of visual function observed in high myopia were ahead of alternation in macular structure.4.Collectively,measuring changes in macular structure with OCTA,in combination with evaluating retinal function using MAIA,could comprehensively evaluate the severity of disease in myopic subjects.