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. 2024 Jan 19;13(2):596.
doi: 10.3390/jcm13020596.

Optic Nerve Head Curvature Flattening Is Associated with Central Visual Field Scotoma

Keunheung Park  1 , Jinmi Kim  2 , Jiwoong Lee  3   4
Affiliations

Optic Nerve Head Curvature Flattening Is Associated with Central Visual Field Scotoma

Keunheung Park et al. J Clin Med. .

Abstract

This study aimed to develop a new index, the average curvature ratio (ACR), to represent the optic nerve head (ONH) tilting and investigate its clinical relevance. Myopic eyes were included and divided into two subgroups: flat ONH (ACR < 1.0) and convex ONH (ACR ≥ 1.0). The occurrences of central and peripheral visual field (VF) defects were compared between the two groups. A total of 375 myopic eyes were recruited, and 231 and 144 eyes were included in the flat and convex ONH groups, respectively. Central scotoma occurred more frequently in the flat ONH group. According to the Patella-Anderson criteria, the number of eyes with central scotoma was 103 (44.6%) in the flat and 44 (30.6%) in the convex ONH groups (p = 0.009). According to Kook's criteria, the number of eyes with central scotoma was 122 (52.8%) in the flat and 50 (34.7%) in the convex ONH groups (p < 0.001). Peripheral scotoma was not significantly different between the groups. In the correlation analysis, the ACR was positively correlated with spherical equivalence, but not with axial length or central corneal thickness. The ACR reflects the degree of the ONH tilt and is a good index for estimating central VF damage in myopic eyes.

Keywords: glaucoma; myopia; optic nerve head.

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Conflict of interest statement

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Custom software was developed to measure optic nerve head (ONH) average curvature ratio (ACR) and vertical–horizontal (VH) ratio. Vertical/horizontal axis and 11 points along with ONH margin were determined by two glaucoma specialists. ACR and VH ratio are automatically calculated.
Figure 2
Figure 2
Calculation of average curvature ratio (ACR) and vertical–horizontal (VH) ratio.
Figure 3
Figure 3
Calculation of coordinates P1~P11 on imaginary circle (radius = 1) for the expected tilt angle.
Figure 4
Figure 4
Definition of central and peripheral scotoma.
Figure 5
Figure 5
Scatter plots of average curvature ratio (ACR) versus vertical–horizontal (VH) ratio. ACR was significantly correlated with VH ratio, which means that when optic nerve head (ONH) shifting occurs, tilting of the ONH also occurs.
Figure 6
Figure 6
Calculation of vertical–horizontal (VH) ratio according to distance of optic nerve head (ONH) shifting in an imaginary circle (radius = 1). (a) The smaller VH ratio, the larger ONH shifted. (b) Calculation formula.
Figure 7
Figure 7
Representative cases of fundus photo and visual field exam.
Figure 8
Figure 8
Central/peripheral scotoma ratio binned by average curvature ratio (ACR). To define the glaucomatous scotoma, Patella–Anderson criteria (a,b) and Kook’s criteria (c,d) were used. The central scotoma ratio became larger as the ACR decreased, which means the more centrally flattened optic nerve head, the more central scotomas occur. In contrast, peripheral scotoma ratio showed little changes as ACR increased.
Figure 9
Figure 9
Shifting versus tilting. (a) Illustrates the case when only a horizontal shifting of the optic nerve head (ONH) occurs. The relative position of the scleral opening (grey circle) to BMO (blue circle) is shifted. In this case, the central curvature of ONH does not change while the VH ratio becomes smaller. Both central and peripheral nerve fibers will be evenly stressed because the elongated length are the same. (b) Illustrates the case when both tilting and shifting of the ONH occurs. Scleral opening is not only horizontally shifted but also rotated (tilted). In this case, the central curvature becomes flattened because of rotation, and this makes the average curvature ratio (ACR) smaller. The VH ratio, which is affected by both tilting and shifting, also becomes smaller. BMO: Bruch’s membrane opening.
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