Abstract
Purpose: :
To determine the circumferential variations in peripapillary retinal nerve fiber layer (RNFL) thickness in myopic subjects.
Methods: :
One hundred and thirty–two young males with myopia (spherical equivalent –0.50 to –14.25 diopters) underwent full ophthalmic examination of one randomly selected eye. Optical Coherence Tomography (OCT–1, Version 4.1; Zeiss–Humphrey Systems, Dublin, CA) was performed by a single operator using circular scans concentric with the optic disc with scan diameters of 3.40 mm, 4.50 mm and 1.75x of vertical disc diameter (VDD). For each scan diameter, RNFL thickness for each clock hour segment were obtained. Statistical analysis comprised repeated measurements analysis and Pearson correlation.
Results: :
Inferior clock hour RNFL thickness (defined as mean thickness from 5.30 to 6.30 clock hour) decreased with more negative spherical equivalents for 3.40 mm (r=0.28, p=0.001), 4.50 mm (r=0.27, p=0.002) and 1.75*VDD scans (r=0.42, p<0.0001); and with increasing axial lengths for 1.75*VDD scans (r=–0.40, p<0.0001). Superior clock hour RNFL thickness (defined as mean thickness from 11.30 to 12.30 clock hour) also decreased with negative spherical equivalents for 1.75*VDD scans (r=0.26, p=0.003) and with increasing axial lengths (r=–0.23, p=0.01). However mean peripapillary RNFL thickness was not correlated with spherical equivalent or axial length for all scan diameters.
Conclusions: :
Inferior and superior clock hour peripapillary RNFL thickness decreased with increasing myopia especially when measured with a scan diameter proportional to optic disc size.
Keywords: retina • myopia • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)