Macular gradient measurement in myopic posterior staphyloma using optical coherence tomography

Abstract

Purpose: To evaluate clinical characteristics and the macular gradient in myopic posterior staphyloma with time domain (TD) optical coherence tomography (OCT).

Methods: Sixty-four staphyloma eyes of 40 patients were examined. Macular gradient (tangent θ) and the location of staphyloma were assessed with OCT imaging. The macular gradient was measured at points 1 mm and 2 mm distant from the fovea. The relationships of the macular gradient with age, axial length, and spherical equivalent were analyzed.

Results: In 8 eyes (12.5%), the bottoms of the staphylomas were in the fovea, and there was no macular gradient. However, in the other 56 eyes (87.5%), the bottoms of the staphylomas were not in the foveal area, and macular gradients existed. Staphylomas were commonly located in the infero-nasal retinal area. The mean macular gradient (tangent θ) was 0.26 ± 0.08 at 1 mm distance from the fovea and 0.28 ± 0.10 at 2 mm. No significant relationships were observed between macular gradient and axial length, patient age, or spherical equivalent.

Conclusions: TD OCT reveals staphyloma location. If the location is outside of the fovea, a macular gradient exists and can be measured by OCT. Axial length measurement error may occur in eyes with poor visual fixation and steep macular gradients.

Keywords: Macula; Myopia; Optical coherence tomography.

Fig. 1

Images showing posterior staphyloma. A 51-year-old woman with 20 / 40 visual acuity and a -11 diopter spherical equivalent. (A) Fundus photograph showing the posterior staphyloma. (B) On B-scan ultrasonography, a posterior staphyloma was detected. (C) An optical coherence tomography (OCT) scan showed the macular gradient. The scanning direction is transverse. Between the macula and the optic disc area, a steep macular gradient is observed, and the staphyloma protrudes toward the temporal retina. The macular gradient, between the macula and the optic disc, was measured (tangent θ). (D) On vertical scanning, symmetric posterior curvature of the retina was seen. From images of the two-axis OCT scans, the location of the staphyloma was confirmed to lie in the temporal area, with respect to the fovea.

Fig. 2

Image showing a radial line scan optical coherence tomography (OCT) map. The transverse scan length (6 mm) and the vertical scan length (2 mm) are features of the Stratus OCT program. We measured the macular gradient at points 1 mm (A) and 2 mm (B) distant from the base of the fovea.

Fig. 3

The distribution of staphylomas, as shown by optical coherence tomography, in 64 eyes. Most staphylomas were distributed in the inferior and nasal retinal areas, with respect to the fovea. S = superior; T = temporal; I = inferior; N = nasal; C = center of fovea; IT = infero-temporal; IN = infero-nasal; ST = supero-temporal; SN = supero-nasal.

Fig. 4

Macular gradients 1 mm and 2 mm distant from the fovea. Macular gradient at 1mm was 0.26 and 0.28 at 2 mm. At 2 mm, the tangent value was greater than at 1 mm, but this was not statistically significant.

Fig. 5

Correlations between macular gradient and spherical equivalent, age, and axial length. No statistically significant associations were seen (spherical equivalent p-value, 0.728; age, 0.244, and axial length, 0.799).