Optic disc of the myopic eye: relationship between refractive errors and morphometric characteristics

A Morphometric Study of the Pars Plana of the Ciliary Body in Human Cadaver Eyes

This study aimed to determine the pars plana length in postmortem human eyes using advanced morphometric techniques and correlate demographics to ocular metrics such as age, sex, ethnicity, and axial length. Between February and July 2005, we conducted a cross-sectional observational study on 46 human cadaver eyes deemed unsuitable for transplant by the SBO Eye Bank. The morphometric analysis was performed on projected images using a surgical microscope and a video-microscopy system with a 20.5:1 correction factor. The pars plana length was measured three times per quadrant, with the final value being the mean of these measurements. Of the 46 eyes collected, 9 were unsuitable for the study due to technical constraints in conducting intraocular measurements. Overall, the average axial length was 25.20 mm. The average pars plana length was 3.8 mm in all quadrants, with no measurements below 2.8 mm or above 4.9 mm. There were no statistically significant variations across quadrants or with age, sex, axial length, or laterality. Accurately defining the pars plana dimensions is crucial for safely accessing the posterior segment of the eye and minimizing complications during intraocular procedures, such as intravitreal injections and vitreoretinal surgeries.

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

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.

Measuring visual acuity and spherical refraction with smartphone screens emitting blue light

INTRODUCTION

A periodical self-monitoring of spherical refraction using smartphones may potentially allow a quicker intervention by eye care professionals to reduce myopia progression. Unfortunately, at low levels of myopia, the far point (FP) can be located far away from the eye which can make interactions with the device difficult. To partially remedy this issue, a novel method is proposed and tested wherein the longitudinal chromatic aberration (LCA) of blue light is leveraged to optically bring the FP closer to the eye.

METHODS

Firstly, LCA was obtained by measuring spherical refraction subjectively using blue pixels in stimuli shown on organic light-emitting diode (OLED) screens and also grey stimuli with matching luminance. Secondly, the visual acuity (VA) measured with a smartphone located at 1.0 m and 1.5 m and displaying blue optotypes was compared with that obtained clinically standard measurements. Finally, the spherical over refraction obtained in blue light with a smartphone was compared with clinical over-refraction with black and white (B&W) optotypes placed at 6 m.

RESULTS

Mean LCA of blue OLED smartphone screens was -0.67 ± 0.11 D. No significant differences (p > 0.05) were found between the VA measured with blue optotypes on a smartphone screen and an eye chart. Mean difference between spherical over-refraction measured subjectively by experienced subjects with smartphones and the one obtained clinically was 0.08 ± 0.34 D.

CONCLUSIONS

Smartphones using blue light can be used as a tool to detect changes in visual acuity and spherical refraction and facilitate monitoring of myopia progression.

Myopic tilted disc: Mechanism, clinical significance, and public health implication

Myopic tilted disc is a common structural change of myopic eyes. With advancing ocular imaging technology, the associated structural changes of the eye, particularly the optic nerve head, have been extensively studied. These structural changes may increase patients' susceptibility to axonal damage and the risk of developing serious optic neuropathies including glaucoma. They also lead to diagnostic difficulties of disease suspects and treatment dilemmas of patients, which implicate clinical practice and subsequently the health care system. In the context of the mounting prevalence of myopia worldwide and its implications to irreversible visual impairment and blindness, it is essential to gain a thorough understanding of the structural changes of myopia. Myopic tilted disc has been extensively investigated by different study groups. However, generalizing the knowledge could be difficult because of the variable definitions of myopic tilted disc utilized in these studies and the complexities of the changes. The current review aimed to clarify the concepts and discuss various aspects of myopic tilted disc, including the definitions, association with other myopia-related changes, mechanism of tilted disc development, structural and functional changes, and clinical implications.

Effects of Myopia and Glaucoma on the Neural Canal and Lamina Cribrosa Using Optical Coherence Tomography

PRCIS

Glaucoma was associated with axial bowing and rotation of Bruchs membrane opening (BMO) and anterior laminar insertion (ALI), skewed neural canal, and deeper anterior lamina cribrosa surface (ALCS). Longer axial length was associated with wider, longer, and more skewed neural canal and flatter ALCS.

PURPOSE

Investigate the effects of myopia and glaucoma in the prelaminar neural canal and anterior lamina cribrosa using 1060-nm swept-source optical coherence tomography.

PATIENTS

19 control (38 eyes) and 38 glaucomatous subjects (63 eyes).

MATERIALS AND METHODS

Participants were imaged with swept-source optical coherence tomography, and the images were analyzed for the BMO and ALI dimensions, prelaminar neural canal dimensions, and ALCS depth.

RESULTS

Glaucomatous eyes had more bowed and nasally rotated BMO and ALI, more horizontally skewed prelaminar neural canal, and deeper ALCS than the control eyes. Increased axial length was associated with a wider, longer, and more horizontally skewed neural canal and a decrease in the ALCS depth and curvature.

CONCLUSION

Our findings suggest that glaucomatous posterior bowing or cupping of lamina cribrosa can be significantly confounded by the myopic expansion of the neural canal. This may be related to higher glaucoma risk associated with myopia from decreased compliance and increased susceptibility to IOP-related damage of LC being pulled taut.

Assessment of changes in optic disc parameters and peripapillary retinal nerve fiber layer thickness in myopic patients and its correlation with axial length and degree of myopia

Purpose

The present study aimed to assess the changes in optic disc and peripapillary retinal nerve fiber layer (RNFL) parameters in myopic patients and its correlation with axial length (AL) and spherical equivalent (SE) using optical coherence tomography (OCT).

Methods

This was a cross-sectional study carried out from August 2019 to September 2021 in the ophthalmology department of a tertiary care hospital in eastern India. Myopic patients in the age group of 20-40 years and SE between - 0.5 to - 10 Diopters (D) were included in the study. Patients were divided into two groups on the basis of degree of myopia and AL. Appropriate statistical analysis was done at the end of the study period.

Results

The study included 307 eyes of 307 myopic patients. There were 181 females (58.96%) and 126 males (41.04%). The mean age of the patients enrolled for the study was 28.78 ± 5.76 years. Statistically significant difference (P < 0.001) was found between SE and AL in between the subgroups of A and B. With every 1 D increase in SE, the average peripapillary RNFL thickness decreased by 0.61 μ while with every 1 mm increase in AL, the average peripapillary RNFL thickness was found to reduce by 1.03 μ.

Conclusion

Analysis of optic nerve head parameters and RNFL thickness by OCT for the diagnosis should be compared with a normative control group that has been matched for refractive error and AL instead of comparison with a normative database that has only been age matched.

Size and position of the optic disc crescent in a white European population with myopia

SIGNIFICANCE

One of the first clinically observed changes in the retina with progressing myopia is in the form of optic disc crescents. If such a change is predictive of myopia progression, it could aid in myopia management interventions to target those at greatest risk of progression and subsequent ocular morbidity.

PURPOSE

To investigate the type, dimension and appearance of optic disc crescents and how they relate to the level of myopia.

METHODS

Retrospective data collection analysing retinal photographs of healthy children and adults with a refractive error of ≤-0.50 D sphere and astigmatism ≤2.00 D. Crescent location, maximum crescent width and vertical disc diameter were measured from retinal images of right eyes only.

RESULTS

Four-hundred eyes with a mean spherical error (SER) of -0.50 to -14.00 D (aged 7-81 years) were included (83.5% exhibited a discernible crescent). Mean (SD) maximum crescent width was 0.24 (0.24) mm. Univariate analysis showed a significant correlation between crescent width and age (r = 0.26, p < 0.001). SER was correlated with crescent width when controlling for age (r = -0.45, p < 0.001) and to the ratio of crescent width to vertical disc diameter (r = -0.43, p < 0.001). Temporal crescents were the most frequently observed (74%), followed by inferior temporal crescents (17%). One-way between-groups analysis of variance showed a significant difference between crescent locations (F = 5.2, p < 0.001). Post-hoc analysis revealed significant differences in SER between those with no crescent versus an inferior-temporal crescent, as well as differences between those with temporal versus inferior-temporal crescents. Other crescent locations did not differ significantly in the level of myopia. Participants not exhibiting a crescent had the lowest level of myopia (mean [SD] -3.03 [1.97)] D), while those with inferior temporal crescents had a mean (SD) SER of -5.01 (2.37) D.

CONCLUSION

In this white European population, higher levels of SER were associated with increasing crescent size. Eyes with inferior temporally located crescents were more myopic.

Peripapillary Atrophy Segmentation and Classification Methodologies for Glaucoma Image Detection: A Review

Information-based image processing and computer vision methods are utilized in several healthcare organizations to diagnose diseases. The irregularities in the visual system are identified over fundus images shaped over a fundus camera. Among ophthalmology diseases, glaucoma is measured as the most common case that can lead to neurodegenerative illness. The unsuitable fluid pressure inside the eye within the visual system is described as the major cause of those diseases. Glaucoma has no symptoms in the early stages, and if it is not treated, it may result in total blindness. Diagnosing glaucoma at an early stage may prevent permanent blindness. Manual inspection of the human eye may be a solution, but it depends on the skills of the individuals involved. The auto diagnosis of glaucoma by applying a consolidation of computer vision, artificial intelligence, and image processing can aid in the ban and detection of those diseases. In this review article, we aim to introduce a review of the numerous approaches based on peripapillary atrophy segmentation and classification that can detect these diseases, as well as details about the publicly available image benchmarks, datasets, and measurement of performance. The review article introduces the demonstrated research of numerous available study models that objectively diagnose glaucoma via peripapillary atrophy from the lowest level of feature extraction to the current direction based on deep learning. The advantages and disadvantages of each method are addressed in detail, and tabular descriptions are included to highlight the results of each category. Moreover, the frameworks of each approach and fundus image datasets are provided. The improved reporting of our study would help in providing possible future work directions to diagnose glaucoma in conclusion.

Factors associated with axial length elongation in high myopia in adults

AIM

To investigate the association of axial length (AL) and ocular factors on AL elongation.

METHODS

A retrospective chart review of patients who underwent two or more AL examinations for more than two years. Totally 4 groups were divided according to initial AL (<24 mm, 24-26 mm, 26-28 mm, ≥28 mm). Initial fundus photograph was used to find risk factors associated AL elongation.

RESULTS

The mean age of the patients was 47.21±7.79y. AL remained almost unchanged in the groups with AL<24 mm and 24≤AL<26 mm. On the contrary, AL increased by 0.011 mm/y in the group with 26≤AL<28 mm and 0.035 mm/y in the group with AL≥28 mm (P<0.001). In high myopia, AL elongation increased in eye with longer AL (r=0.003, P=0.024), female gender (r=0.014, P=0.019), eye with larger peripapillary chorioretinal atrophic area (r=0.002, P=0.019), and smaller vascular arcade angle (r=-0.004, P=0.006). The risk of elongation 0.03 mm/y in high myopia was increased in female gender (P=0.040), and gradually increased in eye with large peripapillary chorioretinal atrophy area (P<0.01).

CONCLUSION

AL elongate significantly in the eye with longer AL, female gender, and the eye with larger atrophic area and smaller arcade angle on fundus photography.

The relationship between optic nerve head deformation and visual field defects in myopic eyes with primary open-angle glaucoma

PURPOSE

To investigate the relationship between the morphologic features of myopic optic nerve head (ONH) and visual field (VF) defects in myopic subjects with primary open-angle glaucoma (POAG) by intraindividual comparison.

METHODS

Myopic POAG subjects with unilateral glaucomatous VF defect were recruited. The morphologic features of myopic ONH, including optic disc tilt, optic disc rotation, and β-zone parapapillary atrophy (PPA) were measured from color fundus photographs. The comparisons were performed between the eyes with VF defects and the contralateral eyes without VF defects. Logistic regression analysis was performed to investigate the relationship between various ocular parameters and the presence of VF defects.

RESULTS

We retrospectively included 100 eyes of 50 myopic POAG subjects. (Mean age: 50.1 ± 10.0 years). The tilt ratio was similar between the paired eyes. The degree of optic disc rotation (12.96 ± 7.21°) in eyes with VF defects were statistically greater than the contralateral eyes (6.86 ± 4.30°; P < 0.001) without VF defect. The β-zone PPA-to-disc area ratio was significantly greater in eyes with VF defects than the contralateral eyes (P = 0.024) without VF defect. In multivariate logistic regression analysis, the greater degree of optic disc rotation was significantly associated with the presence of VF defects (P < 0.001). However, tilt ratio, β-zone PPA-to-disc area ratio, refractive error, and axial length were not associated with the presence of VF defects.

CONCLUSIONS

Among the morphologic features of myopic ONH, only the greater degree of the optic disc rotation was associated with the presence of VF defects in myopic subjects with POAG.

Effect of High Myopia on Optic Nerve Head by Confocal Scanning Laser Ophthalmoscopy in Nepalese Eyes

Purpose

To compare parameters of confocal scanning laser ophthalmoscopy (Heidelberg Retinal Tomograph [HRT] II) in high myopia with age- and sex-matched emmetropes.

Methods

A hospital-based cross-sectional study was conducted among Nepalese subjects aged 18 to 35 years at BP Koirala Lions Centre for Ophthalmic Studies, Institute of Medicine, Maharajgunj, Kathmandu from November 2015 to October 2016. Fifty consecutive subjects with high myopia (spherical equivalent ranging from −6.00 to −12.00 diopters) and age- and sex-matched emmetropic subjects were enrolled for comparison. Correlations between disc area and other HRT parameters, asymmetry between the right and left eyes, and comparisons between male and female subjects in both high myopic and emmetropic groups were evaluated.

Results

Disc area was not significantly (p = 0.11) larger in high myopic eyes than in emmetropic eyes. HRT parameters in highly myopic eyes involved smaller cup parameters and greater rim parameters compared with emmetropic eyes. Disc area was found to be significantly positively correlated with inter disc parameters and significantly negatively correlated with rim to disc area ratio in the high myopia group. Disc area and other intra-disc parameters showed significant correlations between right and left eyes in both high myopia and emmetropia, and no significant differences between males and females from a Nepalese population.

Conclusions

Characteristics of HRT parameters in high myopic eyes involved smaller cup parameters and greater rim parameters compared with emmetropic eyes in a Nepalese population. The effect of disc area on HRT parameters differed significantly only in height variation contour by emmetropic eyes.

Associations between Optic Nerve Head-Related Anatomical Parameters and Refractive Error over the Full Range of Glaucoma Severity

Purpose

To evaluate the associations between optic disc (OD)-related anatomical parameters (interartery angle [IAA] between superior and inferior temporal retinal arteries, OD tilt [TL], rotation [ROT], and torsion [TO], OD surface curvature [CUR], and central retinal vessel trunk entry point location [CRVTL] on OD) and the spherical equivalent of refractive error (SE), and to assess the impact of glaucoma severity on these relationships.

Methods

Cirrus optical coherence tomography (OCT) fundus images and 24-2 visual fields of 438 patients were included. Ellipses were fitted to OD borders. IAA was calculated between marked retinal artery locations on a circle around OD. Blood vessel entry point on OD was marked to locate CRVTL. TL was measured as the angle between the lines fitted to OD clinical boundary and the Bruch's membrane edges on the horizontal B-scans. Ellipse rotation relative to the vertical axis defined ROT. Angle between the long axis of OD and the interartery line defined TO. CUR was determined by the inner limiting membrane on the horizontal B-scans. Linear regression models evaluated by Bayes Factors (BF) were used to determine the covariance structure between the parameters and SE as well as possible impacts of mean deviation (MD).

Results

Our results showed that CRVTL had the strongest relationship with SE, followed by ROT, TL, and IAA (BFs: 3.59 × 10⁷, 2645, 1126, and 248, respectively). MD did not significantly modulate the relationship between ONH parameters and SE.

Conclusion

Our results suggest that SE should be considered when interpreting the OD and its circumpapillary region for diagnostic purposes.

Translational Relevance

The reported relationships between OD-related parameters and ametropia may help to decrease false-positive clinical diagnoses of optic neuropathies.

The relationship between retinal nerve fibre layer thickness profiles and CorvisST tonometry measured biomechanical properties in young healthy subjects

We previously reported that a shallow circumpapillary retinal nerve fiber layer (cpRNFL) peak angle as measured by optical coherence tomography (OCT) suggests the temporal retina is stretched around the optic disc from the papillo-macular bundle (Yamashita T et al. Investigative Ophthalmol Vis Sci 2013). The purpose of the current study was to investigate the relationship between CorvisST tonometry (CST) corneal measurements, axial length (AL) and the change in OCT-measured cpRNFL peak angle, in young healthy subjects. OCT and CST measurements were carried out in 97 eyes of 97 young healthy volunteers. The relationship between cpRNFL peak angle and 12 CST parameters, adjusted for AL, was investigated using linear modelling. The mean ± standard deviation cpRNFL peak angle of the 97 healthy volunteers was 130.6 ± 25.4 (range: 77.8 to 207.0) degrees. The optimal linear model to explain cpRNFL peak angle (chosen from 2¹⁶ different models) included three CST variables related to the speed and size of energy absorption (namely, A1 time, A1 length and A2 time), in addition to AL. In eyes with longer AL and shorter energy absorption in CST measurement, temporal retina is stretched around the optic disc from the papillo-macular bundle, as suggested by a shallow cpRNFL peak angle.

Influence of Myopia on Size of Optic Nerve Head and Retinal Nerve Fiber Layer Thickness Measured by Spectral Domain Optical Coherence Tomography

Purpose

To investigate optic nerve head size and retinal nerve fiber layer (RNFL) thickness according to refractive status and axial length.

Methods

In a cross-sectional study, 252 eyes of 252 healthy volunteers underwent ocular biometry measurement as well as optic nerve head and RNFL imaging by spectral-domain optical coherence tomography. Correlation and linear regression analyses were performed for all subjects. The magnification effect was adjusted by the modified axial length method.

Results

Disc area and spherical equivalent were positively correlated (r = 0.225, r² = 0.051, p = 0.000). RNFL thickness showed significant correlations with spherical equivalent (r = 0.359, r² = 0.129, p = 0.000), axial length (r = -0.262, r² = 0.069, p = 0.000), disc radius (r = 0.359, r² = 0.129, p = 0.000), and radius of the scan circle (r = -0.262, r² = 0.069, p = 0.000). After adjustment for the magnification effect, those relationships were reversed; RNFL thickness showed negative correlation with spherical equivalent and disc radius, and positive correlation with axial length and radius of the scan circle. The distance between the disc margin and the scan circle was closely correlated with RNFL thickness (r = -0.359, r² = 0.129, p = 0.000), which showed a negative correlation with axial length (r = -0.262, r² = 0.069, p = 0.000).

Conclusions

Optic disc radius and RNFL thickness decreased in more severely myopic eyes, but they increased after adjustment for magnification effect. The error due to the magnification effect and optic nerve head size difference might be factors that should be considered when interpreting optical coherence tomography results.

Location of Tessellations in Ocular Fundus and Their Associations with Optic Disc Tilt, Optic Disc Area, and Axial Length in Young Healthy Eyes

Tessellated fundus is found as common and early-phase characteristic of myopic eyes and their locations are varied among patients. However, the relationship between their locations and morphological parameters of the eyes is still unknown. The purpose is this study is to determine the locations of the tessellations in the ocular fundus of young healthy eyes, and to determine relationships between their locations and morphological parameters of the eyes. This is a prospective observational cross sectional study of 126 eyes of 126 healthy volunteers (mean age 26.0±4.1 years). The eyes were classified into eight groups based on the location of the tessellations; no tessellation, temporal, infra-temporal, inferior, nasal, peripapillary, whole retina, and unclassified tessellations. The degree of optic disc tilt was quantified using a sine curve fitting program on the optical coherence tomographic circle scan images. The correlations between each tessellation location and the axial length, area of the optic disc plus conus (AOC), and optic disc tilt were determined. Forty-four eyes were place in the no tessellation group, 12 eyes in the temporal, 21 eyes in the infra-temporal, 9 eyes in the inferior, 8 eyes in the nasal, 15 eyes in the peripapillary, 11 eyes in the whole, and 6 eyes in the unclassified groups. The differences in the axial lengths between the no tessellation group and the infra-temporal groups were significant. A significant difference was found in the AOC between the no tessellation and the inferior, infra-temporal, and peripapilalry groups. A significant difference was found in the optic disc tilt between the no tessellation and infra-temporal groups (P<0.05). The tessellations are located at specific sites in the fundus of young healthy eyes with the infra-temporal location most frequent. It was correlated with some parameters associated with myopia.

Topographical Analysis of Non-Glaucomatous Myopic Optic Discs Using a Confocal Scanning Laser Ophthalmoscope (TopSS)

OBJECTIVES

To show normative data of optic discs and the mechanism of glaucoma in people with myopia.

DESIGN

Cross-sectional study.

PARTICIPANTS

This study investigated 89 Korean adults with myopia but without glaucoma.

METHODS

Patients were divided into three groups according to the refractive error: low, moderate, and high; and axial length: normal or below normal length, moderately long, and extremely long. Optic disc variables were obtained by confocal scanning laser ophthalmoscope and compared among groups.

RESULTS

The optic disc parameters have a correlation between the refractive error and the optic disc parameters such as average depth, volume below, and half-depth volume. Those parameters also decreased as the axial length increased. The thickness of the volume above decreased significantly as the axial length increased, but a similar relationship was not evident with the refractive error change. In addition, the optic disc parameters were analyzed with respect to the 12 clockwise directions.

CONCLUSIONS

Analyses of optic disc parameters provided by TopSS™ revealed the height of the disc decreased as the myopic refractive error and/or axial length increased. The RNFL bundle became compacted in the thinner disc of the myopic population. This could be an explanation for the fragility of the RNFL in the myopic population. The 12 radial section analyses revealed the shallow cupping at the temporal side in the high-myopic, very-long-axis group. The neuroretinal rim (NRR) height significantly decreased at the superior and inferior sides. These findings suggest that the RNFL bundle should be under high mechanical strain in these sectors.

Validity of a new optic disc grading software for use in clinical and epidemiological research

BACKGROUND

To determine the reliability and agreement of a new optic disc grading software program for use in clinical, epidemiological research.

DESIGN

Reliability and agreement study.

SAMPLES

328 monoscopic and 85 stereoscopic optic disc images.

METHODS

Optic disc parameters were measured using a new optic disc grading software (Singapore Optic Disc Assessment) that is based on polynomial curve-fitting algorithm. Two graders independently graded 328 monoscopic images to determine intergrader reliability. One grader regraded the images after 1 month to determine intragrader reliability. In addition, 85 stereo optic disc images were separately selected, and vertical cup-to-disc ratios were measured using both the new software and standardized Wisconsin manual stereo-grading method by the same grader 1 month apart. Intraclass correlation coefficient (ICC) and Bland-Altman plot analyses were performed.

MAIN OUTCOME MEASURES

Optic disc parameters.

RESULTS

The intragrader and intergrader reliability for optic disc measurements using Singapore Optic Disc Assessment was high (ICC ranging from 0.82 to 0.94). The mean differences (95% limits of agreement) for intergrader vertical cup-to-disc ratio measurements were 0.00 (-0.12 to 0.13) and 0.03 (-0.15 to 0.09), respectively. The vertical cup-to-disc ratio agreement between the software and Wisconsin grading method was extremely close (ICC = 0.94). The mean difference (95% limits of agreement) of vertical cup-to-disc ratio measurement between the two methods was 0.03 (-0.09 to 0.16).

CONCLUSIONS

Intragrader and intergrader reliability using Singapore Optic Disc Assessment was excellent. This software was highly comparable with standardized stereo-grading method. Singapore Optic Disc Assessment is useful for grading digital optic disc images in clinical, population-based studies.

A characteristic optic disc appearance associated with myopia in subjects with Graves' ophthalmopathy and in subjects with primary open-angle glaucoma

Purpose

To determine if qualitatively defining the appearance of optic disc change was a valid characteristic of myopia in subjects with Graves’ ophthalmopathy (GO) or primary open-angle glaucoma (POAG).

Methods

We defined typical tilt appearance as the simultaneous presence of the following: an elliptical optic disc, a crescent, unequal sharpness of the cupping margin (horizontally), and nasally displaced vessels in the optic cup. Ninety-two eyes from 92 subjects each with GO or with POAG and no severe complications were included in the study after matching for spherical refractive errors. Using our definition of tilt appearance, two independent observers subjectively judged optic disc photographs. One observer repeated judgments in 70 randomly selected eyes and judgment reproducibility was assessed using kappa statistics. Tilt ratio was used as a quantitative parameter.

Results

The numbers of eyes judged as having a typical tilt appearance in the GO group and in the POAG group were 25 (27.2%) and 39 (42.4%), respectively, by one observer (P = 0.0297), and 12 (13%) and 44 (47.8%), respectively, by another observer (P < 0.0001). Intra- and interobserver reproducibility of tilt judgment were very good (kappa = 0.93) and good (kappa = 0.65), respectively. Tilt ratio did not significantly differ between the two groups. Analytical results including background factors were essentially the same for the two observers: multivariate logistic regression for one observer’s judgment showed that the presence of the typical tilt appearance was associated with belonging to the glaucoma group (odds ratio [OR], 6.25; P = 0.0054), tilt ratio (OR per 0.01, 0.77; P < 0.0001), and spherical refractive error (OR per diopter, 0.80; P < 0.003).

Conclusion

The optic disc feature we designated as typical tilt was associated with myopia, and its frequency was higher in subjects with POAG compared to those with GO.

Peripapillary atrophy detection by sparse biologically inspired feature manifold

Peripapillary atrophy (PPA) is an atrophy of pre-existing retina tissue. Because of its association with eye diseases such as myopia and glaucoma, PPA is an important indicator for diagnosis of these diseases. Experienced ophthalmologists are able to determine the presence of PPA using visual information from the retinal images. However, it is tedious, time consuming and subjective to examine all images especially in a screening program. This paper presents biologically inspired feature (BIF) for the automatic detection of PPA. BIF mimics the process of cortex for visual perception. In the proposed method, a focal region is segmented from the retinal image and the BIF is extracted. As BIF is an intrinsically low dimensional feature embedded in a high dimensional space, it is not suitable to measure the similarity between two BIFs directly based on the Euclidean distance. Therefore, it is necessary to obtain a suitable mapping to reduce the dimensionality. In this paper, we explore sparse transfer learning to transfer the label information from ophthalmologists to the sample distribution knowledge contained in all samples. Selective pair-wise discriminant analysis is used to define two strategies of sparse transfer learning: negative and positive sparse transfer learning. Experimental results show that negative sparse transfer learning is superior to the positive one for this task. The proposed BIF based approach achieves an accuracy of more than 90% in detecting PPA, much better than previous methods. It can be used to save the workload of ophthalmologists and thus reduce the diagnosis costs.

The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

Background

To evaluate the influence of corneal astigmatism (CA) on retinal nerve fiber layer (RNFL) thickness and optic nerve head(ONH) parameters measured with spectral-domain optical coherence tomography (OCT) in high myopes patients before refractive surgery.

Methods

Seventy eyes of 35 consecutive refractive surgery candidates were included in this study. The mean age of the subjects was 26.42 ± 6.95 years, the average CA was −1.17 diopters (D; SD 0.64; range −0.2 to-3.3D), All subjects in this study were WTR CA. 34 eyes were in the normal CA group with a mean CA was −0.67 ± 0.28D, 36 eyes were in the high CA group with an average CA of −1.65 ± 0.49D. All subjects underwent ophthalmic examination and imaging with the Cirrus HD OCT.

Results

No significant difference was noted in the average cup-to-disk ratio, vertical cup-to-disk ratio and cup volume (all P values > 0.05). Compared with the normal CA group, the high CA group had a larger disc area and rim area, thinner RNFL thickness in the temporal quadrant, and the superotemporal and inferotemporal peaks were farther to the temporal horizon (All P values < 0.05). There were no significant differences between the two groups in global average RNFL thickness, as well as superior, nasal and inferior quadrant RNFL thickness (all P values > 0.05).

Conclusions

The degree of with-the-rule CA should be considered when interpreting ONH parameters and peripapillary RNFL thickness measured by the Cirrus HD OCT.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1148475676881895

Clinical characteristics and outcomes of cataract surgery in highly myopic Koreans

Purpose

To evaluate the clinical characteristics and outcomes of cataract surgery in highly myopic Korean subjects.

Methods

We retrospectively reviewed the medical records of 694 eyes of 694 patients who underwent cataract surgery. The case group included 347 eyes of 347 patients whose axial lengths (AXL) were ≥26.00 mm, and the control group included 347 eyes of 347 patients with AXL between 22.00 and 25.99 mm. Cataract density was determined preoperatively using the Pentacam Scheimpflug imaging system. We compared age at operation, cataract type, coexisting disease, visual prognosis, and complications.

Results

The mean age at the time of the operation was 59.60 ± 12.28 years in the case group and 67.47 ± 11.36 years in the control group. The case group had a larger proportion of nuclear cataracts and posterior subcapsular cataracts (PSC), 40.63% and 26.22%, respectively, versus 25.07% and 11.82%, respectively, in the control group. Postoperative corrected visual acuity showed a negative correlation with AXL (R² = 0.172), and severe funduscopic findings were related to poor visual prognosis (p = 0.05). The incidence of retinal detachment in the case group after cataract surgery was 1.72%, compared with 0.28% in the control group.

Conclusions

Highly myopic eyes tend to develop cataracts earlier than normal eyes and to have a higher prevalence of coexisting disease and complications, such as retinal detachment. Nuclear cataracts and PSC were more common in the highly myopic group. Poor visual prognosis was associated with longer axial length and retinal myopic degeneration.

Myopia and associated pathological complications

Besides the direct economic and social burden of myopia, associated ocular complications may lead to substantial visual loss. In several population and clinic-based cohorts, case-control and cross-sectional studies, higher risks of posterior subcapsular cataract, cortical and nuclear cataract in myopic patients were reported. Patients with high myopia (spherical equivalent at least -6.0 D) are more susceptible to ocular abnormalities. The prevalent risks of glaucoma were higher in myopic adults, and risks of chorioretinal abnormalities such as retinal detachment, chorioretinal atrophy and lacquer cracks increased with severity of myopia and greater axial length. Myopic adults were more likely to have tilted, rotated, and larger discs as well as other optic disc abnormalities. Often, these studies support possible associations between myopia and specific ocular complications, but we cannot infer causality because of limitations in study methodology. The detection and treatment of possible pathological ocular complications is essential in the management of high myopia. The ocular risks associated with myopia should not be underestimated and there is a public health need to prevent the onset or progression of myopia.

Evaluation of the influence of tilt of optic disc on the measurement of optic disc variables obtained by optical coherence tomography and confocal scanning laser ophthalmoscopy

PURPOSE

To evaluate the relationship between optic disc variables measured by confocal scanning laser ophthalmoscopy (CSLO) and optical coherence tomography (OCT).

METHODS

Fifty-one eyes in 27 non-glaucomatous patients were scanned using a CSLO-TopSStrade mark and an OCT-OCT 3000trade mark. The relationship between the following four optic disc variables-disc area (DA), cup area (CA), neuroretinal rim area (NRRA), and cup-disc area ratio (CDAR)-measured by CSLO and OCT were evaluated, and the relationship between these measurements and optic disc tilt was assessed. Horizontal (HD) and vertical diameters (VD) of the optic disc were measured from disc photographs, and by CSLO and OCT, and ratios (HD/VD) were then compared.

RESULTS

There was a good correlation in DA, CA, and CDAR except NRRA between OCT and CSLO measurements. In eyes with a tilt >/=4 degrees, DA and NRRA were measured larger, and CDAR and CA were measured smaller by OCT than by CSLO. However, in the eyes with a tilt of <4 degrees, no significant differences in measurement of disc variables were observed for the two measurement systems. HD/VD measured from disc photographs was well correlated with those determined by CSLO (r = 0.741, P < 0.0001), however, it correlated poorly with those measured by OCT in whole study eyes (r = 0.410, P = 0.008) and in eyes tilted by >/=4 degrees, respectively (P = 0.280).

CONCLUSIONS

Although CSLO and OCT measurements of the optic disc are highly correlated, discrepancy becomes prominent in eyes with a disc tilted >/=4 degrees. Therefore, analysis of the optic nerve head by OCT must be cautiously interpreted in eyes with a highly tilted disc.

Optic disk and retinal characteristics in myopic children

PURPOSE

To examine the baseline retina and optic disk characteristics in children.

DESIGN

Cross-sectional study.

METHODS

Subjects included 679 subjects with myopia and 100 with emmetropia, aged 8 to 13 years. Digital retina imaging and cycloplegic autorefraction were conducted to look for signs of retinal degeneration. Other outcome measures were vertical and horizontal cup-to-disk (CD) ratios, CD area ratio, parapapillary atrophy (PPA)-to-disk area ratio, and disk rotational angle.

RESULTS

The prevalence of lattice degeneration was 0.15% (95% confidence interval: 0.008-1.00). No other retinal abnormalities were detected. Increased PPA-to-disk area ratio was associated with increased axial length, increased myopia severity, and increasing age. Cup-to-disk ratios were smaller in subjects with myopia compared with those with emmetropia, but this did not correlate with severity of myopia. In subjects with severe myopia, the upper pole of the disk was rotated away from the fovea but to lesser extent than in those with emmetropia or milder myopia.

CONCLUSIONS

Apart from PPA, degenerative features were not commonly found in this study.

Correlation between a Disc Hemorrhage and Peripapillary Atrophy in Glaucoma Patients with a Unilateral Disc Hemorrhage

PURPOSE

To investigate the correlation between a disc hemorrhage and peripapillary atrophy in glaucoma patients with a unilateral disc hemorrhage.

METHODS

The 44 glaucoma patients (7 with primary open-angle glaucoma and 37 with normal-tension glaucoma) with a unilateral disc hemorrhage from June 1997 to November 2002 were selected randomly and included sequentially. The topographic measurements were performed using Heidelberg Retina Tomograph (HRT) within 3 months of detecting the disc hemorrhage. The zone beta parameters of the peripapillary atrophy were analyzed by the Atrophy Zone Analysis software. The intraocular pressure, refractive error, visual field parameters, and optic disc parameters were compared between both eyes. Univariate and multivariate regression analysis were performed.

RESULTS

The area, angular and radial extent of the zone beta, and the ratio of the zone beta area to the disc area were significantly greater in the hemorrhagic eyes than in the contralateral eyes (P < 0.001). The prevalence of peripapillary atrophy was significantly higher in the hemorrhagic eyes (84%) than in the contralateral eyes (66%) (P = 0.034, chi2 test). The rim area and the rim volume of the hemorrhagic eyes were significantly smaller than those of the contralateral eyes (P = 0.02, < 0.001, respectively). In multivariate regression analysis, the peripapillary atrophy area was the independent significant factor associated with disc hemorrhage (P = 0.03, Odds Ratio = 1.51). The refractive error, intraocular pressure, Mean Deviation (MD), and Corrected Pattern Standard Deviation (CPSD) of the visual fields in both eyes were similar.

CONCLUSION

The area and extent of the peripapillary atrophy was significantly greater and more prevalent in the eyes with a disc hemorrhage than in the contralateral control eyes. Peripapillary atrophy is closely associated with a disc hemorrhage in glaucoma patients irrespective of small neuroretinal rim area and volume.

Development of a novel reference plane for the Heidelberg retina tomograph with optical coherence tomography measurements

PURPOSE

To develop an ideal reference plane for the Heidelberg Retina Tomograph (HRT) with the assistance of optical coherence tomography (OCT) measurements of the mean retinal nerve fiber layer (RNFL) thickness.

PATIENTS AND METHODS

The mean RNFL thickness was measured with OCT in eyes with early glaucoma (n = 50) and age-matched normal eyes (n = 40) at a circle as close as possible to the disc margin without touching it. Glaucomatous eyes were enrolled from chronic open-angle glaucoma patients with reproducible glaucomatous visual field defects with standard automated perimetry. One eye of each patient was randomly selected. A new reference plane was defined as located posteriorly from the mean height of the contour line by the amount of mean RNFL thickness measured with the OCT. Receiver-operating characteristic (ROC) curves were generated to compare the ability of parameters obtained with the conventional and the new reference plane to differentiate glaucomatous eyes from normal eyes. The same analysis was performed for early glaucomatous eyes with myopic refractive errors (n = 25).

RESULTS

The areas under the ROC curves (AUCs) were greater for rim area, rim area/disc area, and rim volume with the new reference plane compared with those with the conventional reference plane, but they were not significantly different. When the same analysis was performed for myopic glaucomatous eyes, the AUCs for rim area, rim area/disc area, and rim volume with the new reference plane were greater than those with the conventional reference plane ( = 0.002, 0.010, and 0.034, respectively).

CONCLUSION

A novel reference plane for the HRT defined by OCT measurements may improve the ability of the HRT to detect early glaucoma, especially in eyes with tilted discs.

Morphometry of the optic nerve and retinal vessels in children by computer-assisted image analysis of fundus photographs

BACKGROUND

The retinal fundus in childhood has a different morphology than in adulthood. Existing methods are not suitable for evaluation of fundus photographs from children. Therefore, a new method for quantitative analysis of fundus morphology utilizing a personal computer-assisted digital mapping system was developed.

METHODS

A CCD flatbed scanner is used to digitize fundus photographs, producing computer images which are analyzed on an IBM/AT computer. Area measurements of the optic disc, excavation and peripapillary crescent are made, as well as determinations of the length, branching, tortuosity and distribution of the retinal vessels on the fundus surface.

RESULTS

Determination of the inter- and intra-observer variability of the computer-assisted image analysis technique demonstrated good reproducibility. The method is demonstrated using fundus photographs of six normal children and six children with the fetal alcohol syndrome. Typical variations in appearance of optic disc and retinal vessels are seen.

CONCLUSION

The system is unique in measuring both the optic nerve head and the retinal vessels and is therefore especially useful for detailed studies of normal and abnormal development of these structures in children.