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

Macula Characteristics in Young Saudi Male Patients with Myopia: A Comparative Hospital-Based Study

BACKGROUND

Myopia is associated with changes in the posterior segment of the eye, including the macula, which may contribute to potential blindness. Therefore, the study aims to evaluate the macula integrity in young myopic patients through optical coherence tomography (OCT).

METHODS

A cross-sectional study was conducted at Qassim University optometry clinics from January to June 2024, involving 30 healthy young males with myopia and 30 with emmetropia. Clinical examination and OCT imaging were used to gather data on macular volume and thickness. The results were analyzed using descriptive statistics and correlation analysis.

RESULTS

The study included 60 myopic eyes and 60 emmetropic eyes. The participants' mean age was 22.10 ± 1.65 years (p = 0.135). A significant difference was found between myopic and emmetropic eyes in fovea, parafovea, perifovea, and total macula thickness and volume (P < 0.05). Additionally, the study showed a significant positive correlation between the magnitude of myopia and fovea thickness (r = 0.297, p = 0.011) and negative correlations with perifovea thickness (r = -0.418, p < 0.001), total macula thickness (r = -0.353, p = 0.003), and total macula volume (r = -0.352, p = 0.003). However, parafoveal thickness had no significant correlation with the severity of myopia (r= -0.107; p=0.207). Fovea thickness was higher in high myopia (255.40 ± 23.51 µm) compared to low (238.69 ± 15.98 µm) and moderate (248.15 ± 8.70 µm) myopia. Perifovea thickness, macula thickness, and macula volume were significantly lower in high myopia (p ˃ 0.05).

CONCLUSION

Myopia influences macular parameters compared to emmetropia. It increases fovea thickness and decreases total macula thickness and volume as well as perifovea thickness. High myopia has more alterations in macula parameters.

Differences in structural parameters in patients with open-angle glaucoma, high myopia and both diseases concurrently. A pilot study

PURPOSE

To evaluate the differences in structural parameters in patients with open-angle glaucoma (OAG), high myopia (M), and both diseases (OAG-M) concurrently.

METHODS

42 subjects with OAG (n = 14), M (n = 14) and OAG-M (n = 14) were included in a prospective pilot study. Mean peripapillary retinal nerve fiber layer (RNFL) thickness, RNFL in superior, temporal, inferior, nasal quadrants, macular ganglion cell complex (GCC) and its' layers, vessel density (VD) of optic nerve head (ONH) and macula were evaluated.

RESULTS

The OAG-M group showed significantly lowest thickness of mean peripapillary RNFL 89 (49-103) μm (p = 0.021), temporal quadrant 64.5 (51-109) μm (p = 0.001) and inferior quadrant 107 (64-124) μm (p = 0.025). The macular RNFL was thinnest in the OAG-M group (p <0.001). Macular VD in inferior quadrant was lowest in OAG-M group at superficial capillary plexus 45.92 (40.39-51.72) % (p = 0.014) and choriocapillaris 51.62 (49.87-56.63) % (p = 0.035). The lowest ONH VD of temporal quadrant was found in the OAG-M group 52.15 (35.73-59.53) % (p = 0.001) in the superficial capillary plexus. Similarly, the lowest VD of inferior quadrant was found in OAG-M group in the choriocapillaris 54.42 (46.31-64.64) % (p<0.001).

CONCLUSIONS

The M group showed the least thinning in the peripapillary RNFL thickness in the temporal quadrant and macular RNFL compared to other two groups. The highest macular VD in the inferior quadrant was in the M group in the superficial capillary plexus, deep capillary plexus and choriocapillaris. The M group showed highest VD in the temporal quadrant and in total VD of ONH at the superficial capillary plexus and in total VD of ONH at the deep capillary plexus.

PRACTICAL RECOMMENDATIONS

The observed decrease in peripapillary RNFL thickness of the temporal quadrant, macular RNFL thickness, the decrease of macular VD at the inferior quadrant and decrease in VD of the ONH temporal quadrant in deep capillary plexus could be beneficial for diagnosing glaucoma in high myopia.

[Optical coherence tomography analysis of the optic nerve head and macula of the fellow eye in acute unilateral nonarteritic anterior ischemic optic neuropathy]

INTRODUCTION

The objective of the study was to compare the thickness of the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) of the fellow eyes of patients with acute nonarteritic anterior ischemic optic neuropathy (NAAION) to those of control subjects.

METHODS

This study included 46 patients with NAAION matched for age, sex and refraction data (spherical equivalent and/or axial length) to 46 control subjects. The anatomical parameters assessed using the Cirrus SD-OCT were the mean RNFL thickness, in the 4 quadrants (inferior, nasal, temporal, superior) and according to the 12 hourly meridians, GCC mean and in 6 quadrants centered on the fovea (infero-nasal, supero-nasal, infero-temporal, supero-temporal, superior and inferior) and parameters of the optic disc (Cup ratio - Vertical and Average Disc, Rim Area, Disc Area, Cup Volume).

RESULTS

Compared to the control group, the eyes contralateral to those affected by NAAION showed a greater value of the area of the neuro-retinal rim (rim area), and a smaller vertical cup/disc (C/D) ratio, mean C/D, and cup volume than the control group. There was no significant difference between the two groups for peripapillary RNFL thickness and GCC parameters.

CONCLUSION

The absence of damage to the RNFL or GCC of the unaffected fellow eyes of patients with NAAION does not explain the perimetric damage. The eyes contralateral to those affected by NAAION are characterized by an overall size of the optic disc identical to those of the control subjects, but a smaller cup, a recognized risk factor for NAAION.

Effect of refractive status on retinal nerve fiber layer thickness in Chinese Population

PURPOSE

To evaluate the relationship between retinal nerve fiber layer (RNFL) thickness and other related parameters measured by spectral-domain optical coherence tomography and the refractive error of eyes.

METHODS

A total of 5394 subjects were enrolled in this population-based cohort study, who were divided into three groups by refractive state after they underwent a standardized ophthalmic examination: emmetropia (the absolute value should range from 0 to 0.5 D), low-moderate myopia (the absolute value of myopic error should range from 0.5 to 6 D), and high myopia (the absolute value of myopic error should be over than 6 D). R 3.6.1 software was adopted for statistical analysis.

RESULTS

Two thousand five hundred fifty-two subjects (4548 eyes) were collected in this study, with an average age of 53.14 ± 10.64 years. There were significant differences among groups in average central corneal curvature, spherical equivalent, and axial length (P < 0.001). The measurements of average retinal nerve fiber layer (RNFL) were 113.95 ± 10.62 μm, 112.97 ± 11.59 μm, and 101.88 ± 15.67 μm, respectively, in the emmetropia, low-moderate, and high myopia groups (P < 0.001). Meanwhile, there was a decreasing trend of cup area, cup volume, disc area, and rim area in the high myopia group compared with the emmetropia group (P < 0.001).

CONCLUSION

The measurements of RNFL thickness vary greatly with refractive error, and this study indicated that it is of great significance for the accurate diagnosis of glaucoma to establish an individualized RNFL thickness database.

Structure–Function Relationships and Glaucoma Detection with Magnification Correction of OCT Angiography

Purpose

To investigate the effects of adjusting the ocular magnification during OCT-based angiography imaging on structure–function relationships and glaucoma detection.

Design

Cross-sectional study.

Participants

A total of 96 healthy control participants and 90 patients with open-angle glaucoma were included.

Methods

One eye of each patient in the control group and the patient group was evaluated. The layers comprising the macula vascular density (VD) and circumpapillary VD were derived from swept-source OCT angiography imaging. The mean sensitivity (MS) of the standard automated perimetry was measured using the Humphrey 24-2 test. Structure–function relationships were evaluated with simple and partial correlation coefficients. A receiver operating characteristic analysis was performed to evaluate the diagnostic accuracy for glaucoma using the area under the receiver operating characteristic curve (AUC). Ocular magnification was adjusted using Littmann’s formula modified by Bennett.

Main Outcome Measures

The association between the axial length and VD, structure–function relationships, and glaucoma detection with and without magnification correction.

Results

The superficial layer of the macular region was not significantly correlated to the axial length without magnification correction (r = 0.0011; P = 0.99); however, it was negatively correlated to the axial length with magnification correction (r = –0.22; P = 0.028). Regarding the nerve head layer in the circumpapillary region, a negative correlation to the axial length without magnification correction was observed (r = –0.22; P = 0.031); however, this significant correlation disappeared with magnification correction. The superficial layer of the macula and the nerve head layer of the circumpapillary region were significantly correlated to Humphrey 24-2 MS values without magnification correction (r = 0.22 and r = 0.32, respectively); however, these correlations did not improve after magnification correction (r = 0.20 and r = 0.33, respectively). Glaucoma diagnostic accuracy in the superficial layer (AUC, 0.63) and nerve head layer (AUC, 0.70) without magnification correction did not improve after magnification correction (AUC, 0.62 and 0.69, respectively).

Conclusions

Adjustment of the ocular magnification is important for accurate VD measurements; however, it may not significantly impact structure–function relationships and glaucoma detection.

Clinical Utility of Bruch Membrane Opening-Minimum Rim Width for Detecting Early Glaucoma in Myopic Eyes

PRCIS

Bruch membrane opening-minimum rim width (BMO-MRW) is overall a useful parameter for diagnosing early glaucoma in myopic eyes.

PURPOSE

The aim of this study was to determine the diagnostic value of BMO-MRW compared with peripapillary retinal nerve fiber layer (pRNFL) thickness for detecting early glaucoma in patients with moderate to severe myopia.

METHODS

One eye was randomly selected from each of the 253 subjects (127 normal controls, 82 with glaucoma suspect, and 44 with early glaucoma). All patients underwent visual acuity testing, refractive error assessment, slit-lamp inspection, intraocular pressure measurement, fundus photography, perimetry. BMO-MRW and pRNFL thickness data were obtained using spectral-domain optical coherence tomography. Area under the receiver operating characteristic curves (AUC) for global and sectoral thickness parameters were calculated.

RESULTS

Global analyses for the discrimination of early glaucoma in all myopic subjects showed comparable AUCs between BMO-MRW and pRNFL thickness [AUC 0.952 (95% confidence interval, 0.918-0.975) and 0.934 (95% confidence interval, 0.896-0.961), respectively, P=0.345]. However, in sectoral analysis, BMO-MRW showed significantly better diagnostic performance than pRNFL thickness except for the superotemporal sector. The AUC for discriminating early glaucoma from glaucoma suspect, BMO-MRW showed statistically better diagnostic performance in the inferotemporal, inferonasal, superonasal, and nasal sectors. When dividing the subject based on a threshold Bruch membrane opening (BMO) area of 2.5 mm2, the diagnostic power of BMO-MRW was generally lower except for the inferonasal sector in the subgroup with a large BMO area.

CONCLUSIONS

BMO-MRW was overall a useful parameter for diagnosing early glaucoma in myopic eyes. However, its diagnostic performance was decreased in myopic eyes with large BMO and there were no significant differences from pRNFL thickness.

Evaluation of Retinal Nerve Fiber Layer, Ganglion Cell-Inner Plexiform Layer, and Optic Nerve Head in Glaucoma Suspects With Varying Myopia

PRCIS

Myopic glaucoma suspects, particularly with high myopia, experience thinning of nontemporal parameters of retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL), without change in optic nerve head (ONH) parameters.

PURPOSE

The aim was to assess the effect of myopia on RNFL, GCIPL, and ONH parameters in glaucoma suspects.

MATERIALS AND METHODS

Seventy-six eyes of glaucoma suspects studied with Cirrus high definition optical coherence tomography were divided into low (n=27), moderate (n=25), and high myopia (n=24) groups. Optical coherence tomography parameters were correlated with spherical equivalent (SE) and evaluated with areas under the receiver operating characteristic curve for quantifying diagnostic ability to differentiate high myopia from nonhigh myopia.

RESULTS

In high myopia, SE was positively correlated with thinning of average, minimum, and nontemporal GCIPL and thinning of average and nontemporal RNFL (P<0.05 for all), but not for inferior RNFL (P=0.28). In moderate myopia, SE was correlated with thinning of inferonasal and minimum GCIPL as well as superior and inferior RNFL (P<0.05 for all). SE was not correlated with ONH parameters in moderate or high myopia (P>0.05). The largest areas under the receiver operating characteristic curve for RNFL and GCIPL parameters were for superior (0.82) and superonasal (0.80) regions, respectively, with comparable diagnostic ability (P=0.74).

CONCLUSION

High myopia, in particular, is associated with thinning of average RNFL, average and minimum GCIPL, and nontemporal parameters of both RNFL and GCIPL, warranting consideration of refractive status in glaucoma suspects.

Correlation between retrobulbar blood flow parameters and retinal nerve fiber, ganglion cell and inner plexus layer thickness in myopia

PURPOSE

To assess the thickness of the retinal nerve fiber layer (RNFL), ganglion cell and inner plexus layer (GCIPL) and blood flow parameters in retrobulbar vessels, and to analyze correlations between these parameters in myopes.

METHODS

The study included forty myopic and 20 healthy eyes. Standard eye examination was supplemented with OCT of the optic nerve and macula (GCIPL, RNFL, RNFL in each quadrant and rim area of the optic nerve) and color Doppler imaging of retrobulbar arteries [peak systolic and end-diastolic velocities, pulsatile index and resistance index (RI) in the ophthalmic (OA), central retinal (CRA), nasal posterior ciliary and temporal posterior ciliary arteries].

RESULTS

Significant correlations were found between blood flow parameters in the CRA, RNFL and GCIPL thickness, and axial length (AL) and spherical equivalent (SE). There were significant positive correlations between RNFL with PSV and EDV in the CRA and negative correlations between RNFL and RI in the CRA. GCIPL was positively correlated with PSV and EDV in the CRA. The decrease in RA was associated with reduced blood flow velocities in the CRA, TPCA and NPCA.

CONCLUSION

The reduced retrobulbar blood flow in healthy young myopes is correlated with increasing AL and refractive value, and thinning of the RNFL and GCIPL. Reduction of the rim-area of the optic disc is associated with vascular and retinal circulatory disorders. These phenomena indicate the vascular basis of the described changes. To the best of our knowledge, this is the first study which correlates ocular circulation with retinal structure.

Axial length-related inter-individual variability in the posterior pole morphology of healthy eyes

AIM

To evaluate morphological characteristics of optic nerve head (ONH) and fovea (F) related to axial length (AL) in healthy eyes.

METHODS

This is an observational study. A consecutive series of healthy subjects was enrolled. Demographic and clinical parameters were age, gender, eye, intraocular pressure, spherical equivalent, AL. Tomographic parameters were ONH-F distance, ONH-F angle, horizontal and vertical ONH diameters, retinal nerve fiber layer (RNFL) thickness and foveal profile patterns.

RESULTS

One hundred six eyes (56 patients) were recruited. A correlation between AL and ONH-F distance was demonstrated (p = 0.0342). Horizontal diameter decreased with increasing AL (p = 0.0003), conferring to ONH a more oval shape. A significant decrease in RNFL thickness was correlated with AL, except for temporal quadrant. Two foveal profile patterns were described: concave and straight patterns. Eyes with concave pattern were longer than eyes with straight pattern.

CONCLUSION

Eye elongation affects the morphology of the ONH, the fovea and the distribution of retinal nerve fibers.

Fourier analysis of circumpapillary retinal nerve fiber layer thickness in optical coherence tomography for differentiating myopia and glaucoma

Differentiating glaucoma from myopic eye is a challenge to ophthalmologists. We try to develop a new discrete Fourier transform (DFT) model for analyzing optical coherence tomography data for the circumpapillary retinal nerve fiber layer (cpRNFL), and investigate DFT as a new diagnostic tool for glaucomatous myopic eyes. The thicknesses of 12 equidistant cpRNFL points were transformed into 6 signals in the frequency domain, ranging from 1 to 6 Hz. In all 232 eyes, generalized linear model showed that 1 Hz, 2 Hz, and 4 Hz were associated with glaucoma, high myopia, and the interaction between glaucoma and high myopia. The 3 Hz signal was associated with glaucoma and high myopia exclusively. A receiver operating characteristic curve analysis of the 3 Hz signals showed areas under the curves of 0.93 (95% CI 0.90-0.96) and 0.93 (95% CI 0.88-0.98), for diagnosing glaucoma in all subjects and in the highly myopic group, respectively. The DFT model is useful to differentiate glaucoma from non-glaucomatous change and showed potential as a diagnostic tool for glaucomatous myopic eyes.

The optic nerve head, lamina cribrosa, and nerve fiber layer in non-myopic and myopic children

The purpose of this study was to evaluate the optic nerve head, lamina cribrosa, retina, and choroid in school age children using spectral domain optical coherence tomography (SD-OCT) and to assess these structural parameters in relation to age, axial length, and refractive error. Healthy children, ages 11.15 ± 2.62 years (range 6-15 years, n = 53), underwent cycloplegic autorefraction, biometry, and SD-OCT imaging in both eyes. Images were analyzed using custom written programs in MATLAB, after adjustment for lateral magnification. Peripapillary retinal nerve fiber layer (RNFL) thickness, retinal and choroidal thicknesses, Bruch's membrane opening (BMO) area, minimum rim width (MRW), and anterior lamina cribrosa surface depth (ALCSD) were determined and analyzed with age, axial length, and refraction. Results show that axial length increased and refractive error became more myopic with increasing age (R2 = 0.25, β = 0.18, P < 0.0001 and R2 = 0.27, β = -0.37, P < 0.0001, respectively). Minimum foveal thickness and central 1 mm retinal thickness increased with increasing age (R2 = 0.15, β = 2.38, P < 0.01 and R2 = 0.11, β = 3.16, P < 0.05, respectively). Age-adjusted raw values for peripapillary RNFL thickness decreased with increasing axial length (R2 = 0.11, β = -3.18, P < 0.05); however, this relationship was not present when image magnification was corrected (R2 = 0.07, β = 2.72, P = 0.09). BMO area increased with myopic refractive error (R2 = 0.16, β = -0.10, P < 0.01). Age-adjusted vertical cup-to-disc ratio decreased with increasing axial length and myopic refractive error (R2 = 0.12, β = -0.05, P < 0.05 and R2 = 0.11, β = 0.03, P = 0.05, respectively). Mean MRW, mean ALCSD, and peripapillary choroidal thickness were not associated with age, axial length, or refraction. Mean MRW was significantly thinner in eyes with deeper ALCS (R2 = 0.41, β = -0.83, P < 0.0001). These findings provide normal values for retinal and optic nerve head parameters in school age children, and also suggest that ocular remodeling occurs in some structures in school age children with normal eye growth and during early stages of myopia development.

The role of intracranial pressure in glaucoma and therapeutic implications

Despite glaucoma being the second leading cause of blindness globally, its pathogenesis remains incompletely understood. Although intraocular pressure (IOP) contributes to glaucoma, and reducing IOP slows progress of the disease, some patients progress despite normal IOP (NTG). Glaucomatous damage causes characteristic cupping of the optic nerve where it passes through the lamina cribrosa. There is evidence that cerebrospinal fluid (CSF) within the optic nerve sheath has a different composition from CSF surrounding the brain. Furthermore, fluctuations in CSF flow into the optic nerve sheath may be reduced by trabeculae within the sheath, and on standing intracranial pressure (ICP) within the sheath is stabilised at around 3 mmHg due to orbital pressure. Blood pressure has been linked both to glaucoma and ICP. These facts have led some to conclude that ICP does not play a role in glaucoma. However, according to stress formulae and Laplace's Law, stress within the lamina cribrosa is dependent on the forces on either side of it, (IOP and ICP), and its thickness. On lying flat at night, ICP between the brain and optic nerve sheath should equalise. Most evidence suggests ICP is lower in glaucoma than in control groups, and that the lamina cribrosa is thinner and more posteriorly displaced in glaucoma. Subjects who have had ICP reduced have developed signs of glaucoma. This review finds most evidence supports a role for low ICP in the pathogenesis of glaucoma. Caffeine, theophylline and vitamin A may increase ICP, and could be new candidates for an oral treatment.

RE-PERG, a new paradigm for glaucoma diagnosis, in myopic eyes

Purpose

To evaluate reliability of steady-state pattern electroretinogram (ssPERG) phase variability in re-test (procedure called RE-PERG) in the presence of myopia, which is known to affect ssPERG amplitude, in glaucomatous patients (GP), normal controls (NC), and myopic patients (MY).

Methods

The procedure was performed on 50 GP, 35 NC, and 19 MY. All subjects were examined with RE-PERG, spectral-domain coherence tomography (SD-OCT), and standard automated perimetry (SAP). Standard deviation of phase (ssPERG SDph) and mean amplitude value (ssPERG Amp) of second harmonic (2ndH) were correlated, by means of one-way ANOVA and Pearson correlation, with mean deviation (MD) and pattern standard deviation (PSD) assessed by SAP and retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) thickness assessed by SD-OCT. Receiving operating characteristics were calculated in cohort populations with and without myopia.

Results

GP showed significant differences from the control group for MD, PSD, RNFL, GCC, ssPERG Amp, and ssPERG SDph; GP also showed significant differences from the MY group for all the parameters except for ssPERG Amp, which is reduced in both groups. In GP group, ssPERG Amp showed a specificity of 82.1% (95% confidence interval [CI]I: 66.5–92.5). In MY group, ssPERG Amp was reduced in 58% of the patients. As a consequence of this, in GP and MY groups, considered as a whole, total specificity dropped to 70.69% (95% CI: 57.3–81.9). In the GP group, ssPERG SDph showed a specificity of 84.6% (95% CI: 69.5–91.1). In both GP and MY groups, considered as a whole, ssPERG SDph total specificity increased from 84.6% to 93.1% (95% CI: 83.3–98.1).

Conclusion

Intrinsic phase variability of ssPERG is not influenced by myopia, even in the presence of fundus alterations.

Optical Coherence Tomography Angiography: Are There Any Changes in Measurements After Strabismus Surgery?

PURPOSE

To evaluate the possible hemodynamic changes following strabismus surgery via optical coherence tomography angiography.

METHODS

Thirty-two eyes of 16 patients who underwent strabismus surgery in one eye were included in the study. Fellow eyes were used as a control group. The vessel densities of the superficial and deep capillary plexus and superficial and deep foveal avascular zones were measured preoperatively and 3 months postoperatively.

RESULTS

The mean superficial and deep foveal avascular zones measurements were 0.84 ± 0.09 and 0.76 ± 1.13 mm², respectively. The mean vessel density of the superficial capillary plexus was 1.23 ± 0.12 and 11.13 ± 1.04 mm² preoperatively in the 1- and 3-mm zones, respectively, whereas the mean vessel density of the deep capillary plexus was 1.13 ± 0.16 and 10.11 ± 1.28 mm² preoperatively. Postoperatively, the mean superficial and deep foveal avascular zones changed to 0.20 ± 0.13 and 0.23 ± 0.12 mm², respectively. Postoperatively, the mean vessel density of the superficial capillary plexus changed to 1.47 ± 0.11 and 12.75 ± 1.10 mm², and the mean vessel density of the deep capillary plexus changed to 1.56 ± 0.12 and 13.91 ± 1.35 mm² in 1- and 3-mm zones, respectively. There was a statistically significant increase in vessel density measurements of the superficial and deep capillary plexus, and a statistically significant decrease in measurements of the superficial and deep foveal avascular zone postoperatively (P < .05). In the fellow eyes, there was no statistically significant change in any of the measurements (P > .05).

CONCLUSIONS

Following strabismus surgery, vessel density of the fovea may increase and the foveal avascular zone may decrease according to optical coherence tomography angiography measurements. [J Pediatr Ophthalmol Strabismus. 2019;56(2):95-100.].

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.

Preventing Myopia

BACKGROUND

Nearsightedness (myopia) has become more common around the world recently, mainly because of changes in visual, educational, and recreational behavior. The question arises how the risk of myopia and its progression can be reduced. This would lessen the prevalence and severity of myopia and also lower the risk of secondary diseases that impair visual acuity.

METHODS

The PubMed/Medline database was selectively searched for pertinent literature.

RESULTS

The risk of myopia is lowered by exposure to daylight and increased by activities performed at short visual distances (close-up work). A person with little exposure to daylight has a fivefold risk of developing myopia, which can rise as high as a 16-fold risk if that person also performs close-up work. Two meta-analyses and a large randomized clinical trial from Asia have shown that the progression of myopia over two years of observation can be lessened by up to 0.71 diopters by the administration of atropine eye drops in a concentration that has practically no serious side effects. At higher doses, myopia progresses more severely than in the placebo group after the cessation of therapy. This is an off-label treatment. A weaker effect on progression has been shown for multifocal optical corrections that include both a distance correction and a correction for near vision.

CONCLUSION

Effective pharmacological and optical measures are now available to lessen the progression of myopia. The increasing prevalence of myopia should motivate pediatricians, parents, and schools to pay attention to risk factors such as close-up work and lack of daylight exposure, particularly in view of the increased use of digital media.

Retinal Nerve Fiber Layer Thickness in a Multiethnic Normal Asian Population: The Singapore Epidemiology of Eye Diseases Study

PURPOSE

To describe variations in retinal nerve fiber layer (RNFL) thickness based on spectral-domain (SD) OCT in a multiethnic Asian population.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Ethnic Chinese, Malay, and Indian adults older than 48 years without glaucoma who were recruited from the Singapore Epidemiology of Eye Diseases Study.

METHODS

All participants underwent standardized systemic and ocular examinations. Retinal nerve fiber layer thickness was measured using SD OCT. Participants with poor-quality scans were excluded. Linear regression models were used to investigate the associations of ocular and systemic factors with average RNFL thickness. Generalized estimating equation models were used to account for correlation between both eyes.

MAIN OUTCOME MEASURE

Average RNFL thickness.

RESULTS

Four thousand four hundred seventy-five participants (8178 eyes) consisting of 1371 Chinese, 1303 Malay, and 1801 Indian adults contributed to this analysis. Average RNFL thickness measured was 95.7±9.6 μm in Chinese participants, 94.9±10.6 μm in Malay participants, and 87.3±10.6 μm in Indian participants (P < 0.001). Multivariate analysis adjusted for age, gender, and ethnicity revealed a reduction in RNFL thickness with increased intraocular pressure and axial length (P < 0.001 for both), as well as a diagnosis of diabetes (P = 0.04); greater RNFL thickness was associated with increased disc area (P < 0.001), signal strength (P < 0.001), and low-density lipoprotein cholesterol (P = 0.02). When these significant variables were taken into account, the average RNFL thickness of Indian participants was significantly thinner compared with Chinese participants (7.45 μm thinner on average [95% confidence interval, 6.75-8.15 μm; P < 0.001]), whereas there was no significant difference in average RNFL thickness between Malay and Chinese participants (P = 0.15).

CONCLUSIONS

Average and regional RNFL thicknesses were significantly thinner in Indian eyes compared with Chinese and Malay eyes. Results of the study highlight the need to acquire more refined normative data for the comparison of individual patients with others of similar ethnic background while accounting for ocular factors that could influence RNFL thickness. This in turn may improve the sensitivity and specificity of glaucoma detection.

Comparison of peripapillary retinal nerve fiber layer thickness between myopia severity groups and controls

AIM

To compare the peripapillary retinal nerve fiber layer (RNFL) thickness measured via optical coherence tomography (OCT) between different groups of myopia severity and controls.

METHODS

This was a prospective cross-sectional study. All subjects underwent a full ophthalmic examination, refraction, visual field analysis and A-scan biometry. Myopic patients were classified as low myopia (LM) [spherical equivalent (SE) from greater than -0.5 D, up to -3.0 D], moderate myopia (MM; SE greater than -3.0 D, up to -6.0 D) and high myopia (HM; SE greater than -6.0 D). The control group consisted of emmetropic (EM) patients (SE from +0.5 D to -0.5 D). A Zeiss Cirrus HD-OCT machine was used to measure the peripapillary RNFL thickness of both eyes of each subject. The mean peripapillary RNFL thickness between groups was compared using both analysis of variance and analysis of covariance.

RESULTS

A total of 403 eyes of 403 subjects were included in this study. The mean age was 31.48±10.23y. There were 180 (44.7%) eyes with EM, 124 (30.8%) with LM, 73 (18.1%) with MM and 26 (6.5%) with HM. All groups of myopia severity had a thinner average RNFL than the EM group, but after controlling for gender, age, and axial eye length, only the HM group differed significantly from the EM group (P=0.017). Likewise, the superior, inferior and nasal RNFL was thinner in all myopia groups compared to controls, but after controlling for confounders, only the inferior quadrant RNFL was significantly thinner in the HM group, when compared to the EM group (P=0.017).

CONCLUSION

The average and inferior quadrant RNFL is thinner in highly myopic eyes compared to emmetropic eyes. Refractive status must be taken into consideration when interpreting the OCT of myopic patients, as RNFL thickness varies with the degree of myopia.

Comparison of quantitative measurement of foveal avascular zone and macular vessel density in eyes of children with amblyopia and healthy controls: an optical coherence tomography angiography study

PURPOSE

To quantify vessel density of superficial capillary plexus (SCP), deep capillary plexus (DCP), and the foveal avascular zone (FAZ) of children's amblyopic eyes and to compare the measurements with those of companion eyes and age-matched controls.

METHODS

Fifteen patients with strabismic amblyopia, and 15 age-matched controls were included in this cross-sectional study. SCP, DCP, and FAZ were measured via optical coherence tomographic angiography (OCTA).

RESULTS

Mean subject age was 8.2 ± 2.3 years in the amblyopia group and 8.6 ± 2.2 years in the control group. The mean SCP at 1 mm, 2 mm, and 3 mm zones were (in the order amblyopic eye, companion eye, control) 1.399 ± 0.088, 5.854 ± 0.195, 12.866 ± 0.346; 1.467 ± 0.084, 5.979 ± 0.182, 12.965 ± 0.321; and 1.559 ± 0.052, 6.343 ± 0.190, 13.819 ± 0.423. SCP was significantly lower in amblyopic eyes than in companion eyes and controls (P < 0.05). The mean DCP at 1 mm, 2 mm, and 3 mm zones were 1.425 ± 0.069, 6.038 ± 0.186, 13.522 ± 0.336; 1.525 ± 0.072, 6.427 ± 0.190, 14.286 ± 0.322; and 1.685 ± 0.074, 6.895 ± 0.198, 15.355 ± 0.356. DCP was significantly lower in amblyopic eyes than companion eyes and controls (P < 0.05). The mean superficial FAZ were 0.287 ± 0.091, 0.262 ± 0.092, and 0.280 ± 0.097. The mean deep FAZ were 0.382 ± 0.092, 0.335 ± 0.080, and 0.329 ± 0.085. There was no significant difference in FAZ among groups (P > 0.05).

CONCLUSIONS

Vessel density of SCP and DCP of eyes with amblyopia is lower than that of the companion eye and the age-matched controls.