To observe the thickness distribution of retina outer nuclear layer (ONL) by directional optical coherence tomography (D-OCT), and analyze variation of ONL thickness with age, gender and anatomical location.

Cross sectional observational study. From August 2017 to January 2019, the patients were included who had no abnormal eyes in Beijing Tongren Hospital, and healthy volunteers were included in the study. Cirrus HD-OCT 5-line single line scanning mode was used to scan the macular area horizontally and vertically. The pupil diameter of all the tested eyes was more than 6 mm. The protocol was approved by The Medical College of Wisconsin Institutional Review Board. The detection light was incident on the temporal, nasal, upper and lower sides about 1.5 to 2.0 mm away from the pupil center to obtain an image that was oblique and clearly showed the Henle fiber layer (HFL). The upper and lower bounds of HFL and external limiting membrane (ELM) were manually labeled. The thickness of ONL and HFL+ONL were measured and recorded at 150 μm intervals on the horizontal and vertical radial lines with the fovea as the midpoint. The thickness of ONL in different anatomic location, ages and genders were compared. The influence of age and gender on ONL were analyzed by one-way ANOVA and independent sample t test respectively.

67 eyes of 67 subjects were enrolled. Among them, the mean age of 27 males (27 eyes) and 40 females (40 eyes) was 38.48±15.33 and 40.98±17.78 years respectively without significantly statistical difference (t=-0.582, P=0.562). The total mean age was 39.97±16.98 years old. There were 11, 22, 22 and 12 patients aged less than 20, 20-39, 40-59 and over 60 years old respectively, according which they were divided into A, B, C and D groups. According to the anatomical location, the thickness of the ONL reached a maximum in the foveola, and then decreased as the eccentricity increased. Horizontally, ONL/ONL+HFL reached the minimum as 36.1% at 0.90 mm on the nasal side, while the minimum was 38.3% at 0.75 mm on the temporal side. Vertically, ONL/ONL+HFL reached the minimum as 36.2% at 0.75 mm inferiorly and 35.6% at 0.9 mm superiorly. There was no significant difference in the ONL thickness of fovea between group A, B,C and D (P>0.05), however, a significant difference was among the four groups in the parafoveal and the perifovea (P <0.05). The ONL thickness of the male was larger than that of the female, and the differences between them in parafoveal and perifovea showed statistically significant ( P<0.05).

Normal people had the thickest ONL in the fovea. While the location is farther from the fovea, the ONL is thinner. The thickness of ONL in parafovea and perifovea is gradually thin with incerase of age. The thickness of ONL in the male is thicker than that in the female.

Tomographyoptical coherence; Normal subjects; Outer nuclear layer; Henle’s fiber layer