Influence of Correction of Ocular Magnification on Spectral-Domain OCT Retinal Nerve Fiber Layer Measurement Variability and Performance

Nowroozizadeh, Sara; Cirineo, Nila; Amini, Navid; Knipping, Shane; Chang, Ted T.; Chou, Tom; Nouri‐Mahdavi, Kouros

doi:10.1167/iovs.14-13880

Cited by 41 publications

(31 citation statements)

References 24 publications

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“…However, Nowroozizadeh et al used customized measurement circles in normal and glaucomatous eyes and found that a correction with ocular magnification did not improve global or regional structure-function relationships [18]. Compared to Nowroozizadeh et al's study, the myopic subjects in the current study had longer axial length.…”

Section: Discussioncontrasting

confidence: 52%

“…Compared to Nowroozizadeh et al's study, the myopic subjects in the current study had longer axial length. According to Bennett's formula, axial length affects the magnification of the ocular optic system by a scaling factor expressed as (24.46 − 1.82)/( AL ⁡−1.82) [17, 18]. Axial length is also linearly correlated with refraction.…”

Section: Discussionmentioning

confidence: 99%

“…The associations between the RNFL thickness and visual field indices were first analyzed separately for the right and left eyes by general linear models and later by combining the data and examining them with linear mixed models. A scaling factor based on Bennett's formula [17, 18] was included in one model to adjust for ocular magnification. Bennett's formula relies on the axial length to correct for ocular magnification.…”

Section: Participants and Methodsmentioning

confidence: 99%

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The Relationship between Visual Field Global Indices and Retinal Nerve Fiber Layer Thickness in Healthy Myopes

Yuan

Feng

et al. 2014

Journal of Ophthalmology

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The aim of the current study was to investigate the association between the thickness of the retinal nerve fiber layer (RNFL) and central visual field indices in otherwise healthy myopes. In total, 57 otherwise healthy subjects were cross-sectionally studied. General ophthalmic examinations, refractive measurements, RNFL thickness by spectral domain optical coherence tomography (OCT), and central visual fields were examined. Linear models were used to assess the associations. In this young and mid-aged population, the mean spherical equivalent was −4.79 (SD 1.66) and −4.59 (SD 1.88) diopters in the right and left eyes, respectively. Approximately 7% to 14% of the eyes showed the average RNFL thickness out of the normal range. The temporal RNFL was remarkably thicker, whereas the nasal RNFL was thinner. The higher the refractive error, the thinner the RNFL thickness. A thicker overall RNFL was significantly associated with decreased mean sensitivity and increased mean defect, and further adjustments for age, sex, refractive error, optic disk area, or ocular magnification did not change the association. Although nonpathologic myopia does not significantly affect central visual field global indices, its effects on the RNFL may be linked with performance on the central visual field test.

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Section: Discussioncontrasting

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Section: Participants and Methodsmentioning

confidence: 99%

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The Relationship between Visual Field Global Indices and Retinal Nerve Fiber Layer Thickness in Healthy Myopes

Yuan

Feng

et al. 2014

Journal of Ophthalmology

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“…Therefore, images obtained from highly myopic eyes were corrected for magnification using Bennett's formula. 16,17 The relationship between OCT image measurements and actual scan diameter was expressed by the formula t ¼ p 3 q 3 s, where t represents the actual scan length, p represents the magnification factor determined by the OCT imaging system camera, q represents the magnification factor in relation to the eye, and s represents the original measurement value obtained from the OCT image. The correction factor q is expressed by the equation q ¼ 0.01306 3 (AL -1.82) (Fig.…”

Section: Methodsmentioning

confidence: 99%

Retinal Microvasculature Alteration in High Myopia

Wang

Jiang

et al. 2016

Invest. Ophthalmol. Vis. Sci.

130

100

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PURPOSE. To investigate the retinal vascular network alterations in highly myopic eyes.METHODS. Thirty-three highly myopic eyes from 21 subjects and 47 mildly myopic or emmetropic eyes from 24 healthy control subjects were enrolled. Optical coherence tomography angiography (OCTA) was used to image the superficial, deep, and whole retinal vascular plexuses at the macular region. Highly myopic eye images were analyzed after adjusting the ocular magnification using Bennett's formula. Fractal analysis (box counting method, D box ) representing vessel density was performed in different annular and quadrantile zones of both large vessels and microvessels. Correlations between the vascular density, axial length, and spherical equivalent refractive error were analyzed. RESULTS.The average density (D box ) of the superficial retinal annular zone (0.6-2.5 mm) microvessels was 1.741 6 0.018 in highly myopic eyes and was shown to be significantly lower than that of the controls (1.773 6 0.010, P < 0.001). Individual annular zone (bandwidth of 0.16 mm) analysis of highly myopic eyes revealed a significant level of microvessel alteration in all zones compared with the same zones in control eyes (P < 0.001). Furthermore, in the highly myopic group, the microvessel density was significantly correlated with axial length elongation in all three layers (r ¼ À0.38 to À0.48; P < 0.05).CONCLUSIONS. This study reveals retinal microvascular network alterations in highly myopic eyes, which correlates with axial length elongation. Fractal analysis of the microvasculature by OCTA images may help to characterize the underlying pathophysiological mechanisms involved in high myopia.

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“…The actual size of the scan circle in the eye increases at higher ALs (because of ocular and photographic magnification). In fact, the real scan circle size in an eye with an AL greater than 24.46 mm or a refractive error less than zero diopter would be larger than the normal size and vice versa . Therefore, because RNFL thickness decreases at more distant points from the optic disc, underestimation of the average RNFL thickness is expected .…”

Section: Discussionmentioning

confidence: 99%