A study on the variation of peripapillary retinal nerve fiber layer thickness in myopic patients using optical coherence tomography

• Main Author: Gan, Eng Hui
• Format: Thesis
• Language: English
• Published: 2011
• Subjects: R Medicine (General); RE Ophthalmology
• Online Access: http://eprints.usm.my/60983/1/DR%20GAN%20ENG%20HUI%20-%20e.pdf; http://eprints.usm.my/60983/

Myopia is a common ocular abnormality worldwide. Individuals with myopia have increased risk of glaucoma compared to non-myopic individuals, but the clinical diagnosis of glaucoma in patients with myopia is often difficult. An important approach in detecting early structural change in glaucoma is based on assessment of the retinal nerve fiber layer (RNFL). Thus, evaluation of the RNFL is very valuable for early detection of glaucoma especially in myopes. However, it remains uncertain whether RNFL thickness would vary with the refractive status of the eye. To compare the peripapillary RNFL thickness between control subjects with emmetropia and myopia subjects with low, moderate and high myopia as well as the relation of RNFL thickness with age, spherical equivalent, axial length of the eye respectively. Four hundreds and three eyes from 403 subjects were recruited according to the selection criteria. The eyes were divided into 4 groups according to their spherical equivalent: control (+0.5D > spherical equivalent > -0.5D), low myopia (-0.5D > spherical equivalent > -3.0D), moderate myopia (-3.0D > spherical equivalent > -6.0D), high myopia (spherical equivalent < -6.0D). All subjects underwent full ocular examination with A-scan and imaging with optical coherence tomography (OCT). The peripapillary RNFL thickness profiles were compared between the groups with ANCOVA. The relation between RNFL thickness and age, spherical equivalent and axial length of the eye were evaluated respectively with coefficient of correlation. Multivariate analysis adjusted for sex, age groups, laterality and axial length of the eyes showed significant thinning of the 360° (p=0.017) and the inferior quadrant (p=0.017) RNFL in high myopic eyes when compared to emmetropic eyes. No significant difference in the RNFL thickness when comparing other refractive error groups. Significant fair correlations were evident between RNFL thickness and spherical equivalent (i=0.330, p<0.001) and axial length (r=-0.286, p<0.05) of the eye respectively. The correlation between age and RNFL thickness was poor but statistically significant (r=-0.156, p<0.05). High myopic eyes had thinner 360° and inferior RNFL thickness compared to emmetropic eyes but not universal in all quadrant around the optic disc. No statistical significant difference of RNFL thickness between other refractive error groups. There was a fair linear relationship between RNFL thickness and spherical equivalent as well as axial length of the eye but, the relationship between RNFL thickness and age was poor in our study model.