Morphological Characteristics Of The Optic Nerve Head And Its Correlation With Choroidal Thickness In Myopia

Objective: To investigate the changes of peripapillary parameters related to the morphological characteristics of the optic nerve head in young healthy myopic patients with different degrees of myopia,including Bruch membrane opening distance(BMOD),Bruch’s membrane opening minimum rim width(BMO-MRW),peripapillary retinal nerve fiber layer(RNFL),and the changes of subfoveal choroidal thickness(SFCT)and peripapillary choroidal thickness(PPCT),and to further explore the correlation between the peripapillary parameters and choroidal thickness,in order to detect the risk population of choroidal thinning in myopic patients,and to guide the early diagnosis and treatment of myopic fundus diseases.Methods: Cross-sectional study.The subjects were young healthy patients with different degrees of myopia who visited the ophthalmology department of the First Affiliated Hospital of Kunming Medical University from May 2022 to February 2023.Each participant was asked about their personal,family,and systemic medical history,and underwent relevant ophthalmic examinations,including computerized optometry,subjective optometry,fundus photography,optical coherence tomography(OCT),central corneal thickness,and axial length.The participants were divided into 4groups according to the axial length(AL),Group AL1(AL≤24mm),Group AL2(24<AL≤25mm),Group AL3(25<AL≤26mm),and Group AL4(AL>26mm).Bruch’s membrane opening distance(BMOD),Bruch’s membrane opening minimum rim width(BMO-MRW),peripapillary choroidal thickness(PPCT),subfoveal choroidal thickness(SFCT),and peripapillary retinal nerve fiber layer(RNFL)were measured with the built-in software of OCT.The difference of peripapillary parameters and choroid thickness among different axis groups was analyzed with One-Way ANOVA,and the correlation between ocular axis,peripapillary parameters and choroid thickness in respctive group was analyzed with Pearson correlation.Parameters showing significant associations in correlation analysis(P<0.05)were analyzed with multiple linear regression.Results:A total of 142 eyes of 76 young healthy patients with different degrees of myopia were included in this study,including 31 males and 45 females,aged 20-30 years,with an average age of 25.07±2.11 years.They were divided into four groups according to the ocular axis,Group AL1 of 31 eyes with AL≤24mm,Group AL2 of43 eyes with 24<AL≤25mm,Group AL3 of 42 eyes with 25<AL≤26mm,and Group AL4 of 26 eyes with AL>26mm.1.Choroidal thickness1.1 Subfoveal choroidal thickness(SFCT)1)Comparison of SFCT between groups: the thickness value of AL1(335.13±99.54μm)was significantly greater than that of AL2(260.36±97.57μm),AL3(212.33±47.30μm)and AL4(208.77±63.59μm)(P<0.05).2)Correlation analysis between SFCT and axial length(AL): SFCT was negatively correlated with AL(r=-0.476,P=0.000).As the length of the axial length increases,a thinning of the choroidal thicknessin the macular fovea can occur.1.2 Peripapillary choroidal thickness at 3 mm from the center of the optic disc(PPCT)1)Comparison of PPCT between groups.Average PPCT: the thickness value of AL1(267.39±50.15μm)was significantly thicker than that of AL2(216.35±81.44μm),AL3(185.82±35.91μm)and AL4(193.94±54.46μm)(P<0.05).Superior PPCT: the thickness value of AL1 (315.06±57.32μm)was significantly thicker than that of AL2(262.39±91.34μm),AL3(226.74±58.68μm)and AL4(234.54±55.14μm)(P<0.05);inferior PPCT: the thickness value of AL1(221.03±86.96μm)was significantly thicker than that of AL2(161.59±75.85μm),AL3(137.74±34.52μm)and AL4(149.77±64.44μm)(P<0.05);nasal PPCT: the thickness value of AL1(303.42±71.94μm)was significantly thicker than that of AL2(221.76±87.69μm),AL3(209.31±60.04μm)and AL4(204.54±69.71μm)(P<0.05);temporal PPCT: the thickness value of AL1(282.52±77.67μm)was significantly thicker than that of the AL2(209.83±99.59μm),AL3(163.10±50.62μm)and AL4(162.96±62.39μm)(P<0.05).Supranasal PPCT: the thickness value of AL1(295.68±65.31μm)was significantly thicker than that of AL3(225.90±51.15μm)(P<0.05);infranasal PPCT: the thickness value of AL1 group(236.84±53.50μm)was significantly thicker than that of AL3(181.74±43.74μm)and AL4(177.88±56.39μm)(P<0.05);supratemporal PPCT: the thickness value of AL1group(273.32±76.96μm)was significantly thicker than that of the AL3(200.14±44.60μm)and AL4(192.77±64.84μm)(P<0.05);infratemporal PPCT: the thickness value of AL1(262.48±77.03μm)was significantly thicker than that of the AL2(183.98±90.89μm),AL3(141.90±39.95μm)and AL4(151.96±55.28μm)(P<0.05).2)Correlation analysis between PPCT and AL.Average PPCT was negatively correlated with AL(r=-0.407,P=0.000),while superior,inferior,nasal,temporal,infranasal,supratemporal,infratemporal PPCT were significantly negatively correlated with AL(r=-0.362,-0.364,-0.350,-0.481,-0.325,-0.406,-0.477;P=0.000,0.000,0.000,0.000,0.000,0.000,0.000),there was no significant correlation between supranasal PPCT and AL(r=-0.135,P=0.112),and peripapillary choroidal thickness thinning could be seen with increasing axial length.2.Thickness of peripapillary retinal nerve fiber layer(RNFL).1)Comparison of RNFL between groups.Average RNFL: the thickness value of AL1(104.41±6.96μm)was significantly thicker than that of AL3(98.76±8.44μm)and AL4(96.85±5.40μm)(P<0.05),while the thickness value of AL1 was thicker than that of AL2(103.83±6.30μm)with no statistical significance(P>0.05).Superior RNFL: the thickness value of AL1(138.14±9.34μm)was significantly thicker than that of AL2(128.34±15.17μm),AL3(119.03±17.60μm)and AL4(115.85±15.72μm)(P<0.05);Inferior RNFL: the thickness value of AL1(136.15±15.79μm)was significantly thicker than that of AL3(118.95±11.62μm)and AL4(120.62±13.99μm)(P<0.05);nasal RNFL: the thickness value of AL1 was thicker was than that of AL3(62.74±8.40μm)and AL4(59.88±6.98μm)with no statistical significance(P>0.05);temporal RNFL: the thickness value of AL1(77.11±12.62μm)was significantly thinner than that of AL2(89.17±19.56μm),AL3(94.31±20.04μm)and AL4(93.35±19.94μm)(P<0.05).2)Correlation analysis between RNFL and AL.Average RNFL was significantly negatively correlated with AL(r=-0.359,P=0.000);superior and inferior RNFL were negatively correlated with AL(r=-0.508,-0.403;P=0.000,0.000),nasal RNFL was not significantly correlated with AL(r=-0.098,P=0.261),temporal RNFL was significantly positively correlation with AL(r=0.311,P=0.000).The average peripapillary nerve fiber layer thickness and the thickness of the nerve fiber layer in all quadrants except for the temporal side became thinner as the length of the axial increased.3)Correlation analysis between RNFL and PPCT.There was no significant correlation between average RNFL and average PPCT(r=0.173,P=0.051);superior RNFL was not significantly correlated with superior PPCT(r=0.165,P=0.058);inferior and nasal RNFL were significantly positively correlation with corresponding quadrant PPCT(r=0.288,0.303;P=0.001,0.000),temporal RNFL was negatively correlated with temporal PPCT(r=-0.515,P=0.000).The thinning of the inferior,nasal peripapillary retinal nerve fiber layer was accompanied by the thinning of the peripapillary choroid in the corresponding quadrant,while the thickening of the temporal peripapillary retinal nerve fiber layer was accompanied by the thinning of the temporal peripapillary choroid.3.Peripapillary parameters related to the morphological characteristics of the optic nerve head.3.1 Bruch’s membrane opening distance(BMOD)1)Comparison of BMOD between groups.Horizontal BMOD: the distance value of AL3(1809.76±141.86μm)was significantly wider than AL2(1753.41±249.68μm)and AL1(1609.68±121.97μm)(P<0.05);vertical BMOD: there was an increase from the value of AL1(1697.42±111.18μm)to that of AL2(1774.88±213.10μm),and to that of AL3(1808.1±171.72μm),with no statistically significant difference(P>0.05),indicating that there was no significant change in vertical BMOD values as AL increased.2)Correlation analysis between BMOD and AL: horizontal BMOD was significantly positively correlated with AL(r=0.269,P=0.001);vertical BMOD was significantly ositively correlated with AL(r=0.167,P=0.048).3)Correlation analysis between BMOD and choroidal thickness: horizontal BMOD was significantly negatively correlated with SFCT(r=-0.421,P=0.000),and with average PPCT(r=-0.391,P=0.000).Horizontal BMOD was significantly negatively correlated with the PPCT of superior,inferior,nasal,temporal,supratemporal,infratemporal,supranasal,and infranasal(r=-0.192,-0.371,-0.260,-0.428,-0.256,-0.334,-0.331,-0.479;P=0.023,0.000,0.002,0.000,0.002,0.000,0.000,0.000).The widening of horizontal BMOD was accompanied by the thinning of the subfoveal choroidal thickness and peripapillary choroidal thickness.Vertical BMOD was significantly negatively correlated with SFCT(r=-0.262,P=0.002)and with average PPCT(r=-0.288,P=0.001).Vertical BMOD was significantly negatively correlated with the PPCT of superior,inferior,nasal,temporal,supratemporal,infratemporal,supranasal,and infranasal(r=-0.168,-0.260,-0.168,-0.284,-0.295,-0.235,-0.294,-0.292;P=0.047,0.002,0.048,0.001,0.000,0.005,0.000,0.000).The widening of vertical BMOD was accompanied by the thinning of the subfoveal choroidal thickness and peripapillary choroidal thickness.4)Correlation analysis between BMOD and RNFL: horizontal BMOD was not significantly correlated with average RNFL(r=-0.058,P=0.516),while significantly negatively correlated with superior and nasal RNFL(r=-0.342,-0.184,P=0.000,0.035),significantly positively correlated with temporal RNFL(r=0.342,P=0.000),and not significantly correlated with inferior RNFL(r=-0.069,P=0.430).The widening of horizontal BMOD was accompanied by the thinning of superior and nasal peripapillary nerve fiber layer thickness,and the thickening of temporal peripapillary nerve fiber layer thickness.Vertical BMOD was not significantly correlated with average RNFL(r=0.112,P=0.208),or with superior,inferior,and nasal RNFL(r=-0.141,0.083,-0.004;P=0.107,0.341,0.964),and was significantly positively correlated with temporal RNFL(r=0.229,P=0.008).The widening of vertical BMOD was accompanied by the thickening of temporal peripapillary nerve fiber layer thickness.3.2 Bruch’s membrane opening minimal rim width(BMO-MRW)1)Comparison of BMO-MRW between groups.The was no statistically significance of average BMO-MRW,superior,inferior,nasal,temporal,supratemporal,infratemporal,supranasal,and infranasal BMO-MRW among the groups(P>0.05).2)Correlation analysis between BMO-MRW and AL: average BMO-MRW was significantly positively correlated with AL(r=0.199,P=0.020).3)Correlation analysis between BMO-MRW and choroidal thickness.Average BMO-MRW was significantly negatively correlated with SFCT and average PPCT(r=-0.443,-0.474;P=0.000,0.000),the increase of average BMO-MRW was accompanied by the thinning of SFCT and average PPCT.BMO-MRW in the quadrants was significantly negatively correlated with PPCT in the corresponding inferior,nasal,infranasal,supratemporal,and infratemporal quadrants(r=-0.233,-0.235,-0.200,-0.219,-0.188;P=0.006,0.005,0.018,0.009,0.026);there was no significant correlations between them in the superior,temporal and supranasal quadrants(r=-0.115,-0.041,-0.057;P=0.175,0.633,0.500).4)Correlation analysis between BMO-MRW and RNFL.Average BMO-MRW was correlated positively with average RNFL(r=0.175,P=0.049);BMO-MRW in the quadrants was correlated positively with the RNFL in the corresponding inferior,temporal quadrant(r=0.188,0.282;P=0.030,0.001);nasal BMO-MRW was positively correlated with nasal RNFL(r=-0.197,P=0.024);there was no significant correlation in superior quadrant(r=0.115,P=0.188).The narrowing of average BMO-MRW was accompanied by the thinning of average RNFL thickness.4.Multiple linear regression analysis.4.1 Multiple linear regression analysis of BMOD with average RNFL,SFCT,and average PPCT.There was no significant correlation between horizontal BMOD,vertical BMOD(independent variable)with average RNFL,SFCT,and average PPCT(dependent variable)(P>0.05).4.2 Multiple linear regression analysis of AL and BMO-MRW with average RNFL,SFCT,and average PPCT: AL and BMO-MRW(independent variables)were independently correlated with average RNFL,SFCT,and average PPCT(dependent variables)(P<0.01).1)SFCT was significantly negatively correlated with AL(β=-0.383,P<0.001)and with average BMO-MRW(β=-0.361,P<0.001).SFCT thinned as the axial length grew and thinned as BMO-MRW became wider.2)Average PPCT was significantly negatively correlated with AL(β=-0.269,P<0.001)and with average BMO-MRW(β=-0.409,P<0.001).The average PPCT thinned as the axial length grew and thinned as the BMO-MRW became wider.3)Average RNFL was significantly negatively correlated with AL(β=-0.407,P<0.001)and positively correlated with average BMO-MRW(β=0.253,P<0.01).The average RNFL thinned as the axial length grew and thinned as BMO-MRW became narrower.Conclusions: 1.The subfoveal choroidal thickness and peripapillary choroidal thickness become thinner with the growth of the axial length in the young healthy myopic people.2.The thickness of the temporal peripalliary retinal nerve fiber layer increases with the growth of the axial length,and the thickness of retinal nerve fiber layers in the remaining quadrant become thinner.3.BMO-MRW is correlated with choroidal thickness changes during the development of myopia,especially the peripapillary choroidal thickness.BMO-MRW can be combined with AL as a predictive model for choroidal thickness thinning,so as to detect people at risk of choroidal thinning in myopia patients to guide the early diagnosis and treatment of myopia-related fundus lesions.