Study on the distribution characteristics of peripheral retinal defocus and its correlation with refractive error in adults with myopia

Objective  To explore the characteristics of peripheral retinal defocus distribution in adult myopia and its relationship with refractive error.

Methods  A cross-sectional study was conducted.A total of 270 myopic patients aged 18 to 46 years were enrolled at Tianjin Eye Hospital from January to March 2024.Data from the right eye were included in the analysis.Spherical power and cylindrical power were obtained using an autorefractor and the spherical equivalent (SE) was calculated.Corneal curvature parameters including flap keratometry (K1), steep keratometry (K2), and average keratometry (Km) were measured using the Pentacam anterior segment imaging analyzer.Central corneal thickness (CCT) and axial length (AL) were measured using the IOLMaster optical biometer.Peripheral defocus within a 53° area centered on the fovea was assessed using multispectral refractive topography.Based on the peripheral defocus data, the distribution patterns were classified into four types: hemilateral upturn type, saddle type, crater type, and relatively flat type.Characteristics of different tpes and their correlation with diopter were analyzed.This study followed the Declaration of Helsinki.The study protocol was reviewed and approved by the Medical Ethics Committee of Tianjin Eye Hospital (No.KY-2024020).All participants voluntarily participated and signed the informed consent form.

Results  Of the different types of peripheral retinal defocus, 186 eyes (68.63%) were hemilateral upturn type, 45 eyes (16.61%) were crater type, 36 eyes (13.28%) were relatively flat type, and 3 eyes (1.11%) were saddle type.The crater type exhibited the lowest mean SE of (-6.18±1.50)D, while the relatively flat type showed the highest mean SE of (-3.88±0.87)D.There were significant differences in SE and AL among different peripheral defocus types ( F=15.469, 17.928, 3.431; all P<0.05).The hemilateral upturn type had significantly lower SE and spherical diopter than the relatively flat type, and crater type had significantly lower SE and spherical diopter compared to the hemilateral upturn type and relatively flat type significantly, and the hemilateral upturn type had longer AL than the relatively flat type (all P<0.05).There was no statistically significant difference in CCT, K1, K2, or Km among different peripheral defocus types ( F=0.861, 1.761, 2.603, 2.248; all P>0.05).Spherical power was weakly negatively correlated with superior, inferior, and temporal peripheral defocus ( r=-0.269, P<0.001; r=-0.176, P<0.01; r=-0.292, P<0.001).Age was positively correlated with superior and temporal peripheral defocus ( r _s=0.213, P<0.001; r _s=0.181, P=0.003), and negatively correlated with nasal peripheral defocus ( r _s=-0.138, P=0.023).

Conclusions  Among adult peripheral defocus patterns, the hemilateral upturn type is predominant.The crater type has the lowest mean spherical equivalent, while the relatively flat type has the highest.There are negative correlations between spherical power and the superior, inferior, and temporal peripheral defocus.

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