Correlations between optical parameters of retinal nerve fiber layer measured by optical coherence tomography and age in normal population

Background

The measurement of retinal nerve fiber layer (RNFL) by Cirrus optical coherence tomography (OCT) has been applied widely in ophthalmology.However, previous assessment of RNFL is based on spatial measurement, while the evaluation based on optical characteristics of OCT can offset the shortcomings of spatial measurement in some eye diseases.

Objective

This study was to analyze the optical characters of RNFL measured by OCT and its correlation with age in healthy Chinese individuals.

Methods

Four hundred and six normal healthy subjects were collected in Shanghai Shibei Hospital from June 2011 to June 2012, with the age of 40-83 years old.Macular RNFL was unilateral imaged using a Cirrus OCT device with 5 line raster macular scan mode under the approval of Ethic Committee of Shanghai Shibei Hospital and informed consent of subjects.A customized software was used to measure RNFL optical characters, including absorbance (A value) and attenuate coefficient.The difference of the measured parameters in different genders was compared.The correlations between RNFL optical characters and age were analyzed by linear regression analysis.

Results

The data of 353 eyes were included in the final outcomes.The RNFL thickness, A value and attenuate coefficient were (35.1±4.4)μm, 121.6±5.3 and 2.06±0.25, respectively.RNFL thickness and A value showed significantly negative correlations with age (r=-0.487, -0.571, both at P<0.01) with the regression equation Y=-0.17 X+ 45.23 and Y=-0.24 X+ 135.82, while a positive correlation was found between the attenuate coefficient and age (r=0.368, P<0.01) with the regression equation Y= 0.01 X+ 1.63.RNFL thickness and A value showed weaker positive correlations with OCT signal intensity (r_s=0.128, P=0.016; r_s=0.284, P<0.01), but no remarked correlation was seen between the attenuate coefficient and OCT signal intensity (r_s=-0.053, P=0.319).

Conclusions

Age of subjects affects the parameters of OCT optical characteristics in normal populaition.Age-related RNFL change in optical characters of OCT should be considered before concluding optical parameters.

Retina; Nerve fiber layer; Tomography, optical coherence/method; Age; Absorbance; Attenuate coefficient