The Shortest Radius of Curvature of Bruch's Membrane in Macular Optical Coherence Tomography

Hui Kyung Kim; Sun Ho Park; Jae Jung Lee; Han Jo Kwon; Keun Heung Park; Sung Who Park; Ji Eun Lee

doi:10.3341/jkos.2019.60.9.867

Journal List > J Korean Ophthalmol Soc > v.60(9) > 1133039

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Kim, Park, Lee, Kwon, Park, Park, and Lee: The Shortest Radius of Curvature of Bruch's Membrane in Macular Optical Coherence Tomography

Original Article

Journal of the Korean Ophthalmological Society 2019; 60(9): 867-873.

Published online: 18 September 2019

DOI: https://doi.org/10.3341/jkos.2019.60.9.867

The Shortest Radius of Curvature of Bruch's Membrane in Macular Optical Coherence Tomography

Hui Kyung Kim, MD^1,², Sun Ho Park, MD^1,², Jae Jung Lee, MD^1,², Han Jo Kwon, MD^1,², Keun Heung Park, MD^1,², Sung Who Park, MD, PhD^1,², Ji Eun Lee, MD, PhD^1,²

¹Department of Ophthalmology, Pusan National University School of Medicine, Yangsan, Korea.

²Research Institute, Pusan National University Hospital, Pusan, Korea.

Address reprint requests to Sung Who Park, MD, PhD. Department of Ophthalmology, Pusan National University Hospital, #179 Gudeok-ro, Seo-gu, Busan 49241, Korea. Tel: 82-51-240-7326, Fax: 82-51-240-7432, oph97@naver.com

Received 28 February 2019 Revised 27 March 2019 Accepted 16 August 2019

The Korean Ophthalmological Society

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To develop software to measure the shortest radius in curvature of Bruch's membrane from optical coherence tomography (OCT), and then to apply it to various types of eyes.

Methods

Macular OCT images consisting of 12 images of 9 mm radial scans were studied. The horizontal to vertical pixel ratios were changed to 1:1, and Bruch's membrane was marked automatically on each image. Software to measure the radius of Bruch's membrane curvature was developed. The shortest radius on each image was defined as r (mm) and the average r of 12 images was defined as R (mm). The reciprocal of R was multiplied by the constant, 337.5, which was defined as the posterior staphyloma (PS) index.

Results

The OCT images of five eyes were analyzed by the software, which could calculate the curvature of Bruch's membrane automatically. The PS indices were 12.7, 23.7, and 66.4 in eyes without refractive error (Case I), in the high myopic group without posterior staphyloma (Case II), and in the high myopic group with posterior staphyloma (Case V), respectively. The PS index gradually increased according to aging in a 37-year-old patient (Case IV) with mild staphyloma from 34.6 to 39.5 over 4 years.

Conclusions

PS index is a novel parameter to reflect the level of posterior staphyloma, but further studies are needed to apply it to clinical patients.

Keywords: Bruch's membrane, Curvature, Myopia, Optical coherence tomography, Posterior staphyloma

Figures and Tables

Figure 1

Measurement of Bruch's membrane curvature. (A) Bruch's membrane was marked automatically (green line). (B) The horizontal to vertical pixel ratio changed to 1:1 in images of optical coherent tomography and the radium of a pixel (a) is calculated by making a curve (yellow line) connecting two pixels (b, c) that are 100 pixels away (about 1.4 mm distance). (C) The radius on every pixel of Bruch's membrane was measured and the shortest radius of optical coherent tomography image was called as r.

Figure 2

Fundus photo (A) and ultrasonography (B) show that a patient (case II) doesn't have posterior staphyloma. Case II, high myopia without posterior staphyloma.

Figure 3

Case II, high myopia with mild posterior staphyloma. Fundus photo (A) shows that case IV likely has mild posterior staphyloma (PS). Series of optical coherent tomography (B-F) were examined in each year from 2015 to 2018. The curvature of Bruch's membrane has become steeper according to aging. PS index has gradually increased by 5.0 over 4 years.

Figure 4

Fundus photo (A) shows posterior staphyloma (PS) of case V. (B) It shows analysis of Bruch's membrane curvature (green line) of Case V. The blue line indicates the point of shortest radius of Bruch's membrane and its ‘r’ was 4.96 mm. The ‘R’ (average of each “r”) was 4.93 mm and PS index is 68.5.

Figure 5

Diagram of posterior staphyloma index based on Table 1. PS = posterior staphyloma.

Table 1

Summary of PS index and characteristics of Case 1–5

OCT = optical coherent tomography; PS = posterior staphyloma.

^*R of OCT: Average of the shortest radius of curvature of Bruch's membrane on optical coherent tomography; ^†PS index after (years): PS index of 2nd examination of OCT taken after year.

Notes

^{Conflicts of Interest} The authors have no conflicts to disclose.

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