Moderate Myopia Group Research Articles

Relationship between functional and structural retinal changes in myopic eyes

BackgroundThe aim of this study was to investigate the retinal structure in different grades of myopia and correlate it with the functional changes detected with multifocal electroretinogram (mf‐ERG) and try to show the most important determining factors.MethodsThe study included 80 participants divided into four groups according to their spherical equivalent refractive error, namely, emmetropia (within ± 0.50 D), mild myopia group (greater than −0.50 to −3.00 D), moderate myopia group (more than −3.00 to −6.00 D) and high myopia group (greater than −6.00 D). Full ophthalmologic examination was performed for all participants, including visual acuity (VA), slitlamp examination, Goldmann applanation tonometry, indirect ophthalmoscopy, axial length (AL) measurement, retinal nerve fibre layer thickness assessment and mf‐ERG stimulation.ResultsAxial length was significantly higher in myopes than emmetropes; also it was higher the greater the degree of myopia. There was a reduction in the amplitude and prolongation of implicit times of mf‐ERG in myopia. Also P1 implicit time of the mf‐ERG response was prolonged the greater the degree of myopia. The retinal nerve fibre layer was significantly thinner in myopic groups than the emmetropic group. The thinning of the retinal nerve fibre layer increased the more the degree of myopia. Multiple regression analysis of myopic patients showed that AL is the most important determinant of most of the mf‐ERG five‐rings retinal response density (RRD), mf‐ERG four‐quadrant (Q) RRD, most of the five‐rings P1 amplitude and all five‐rings latencies. The most important determinant factors of mean Q RRD were VA, AL and retinal nerve fibre layer thickness.ConclusionThe retina of the myope is subject to both structural and functional alterations compared to that of the emmetrope. Significant correlations exist between the functional and structural changes and can be explained on bases of longer AL and increasing myopic refraction.

Association of retinal nerve fiber layer thickness and degree of myopia using spectral-domain optical coherence tomography

Objective The objective of this study was to assess the effect of myopia on the peripapillary retinal nerve fiber layer (RNFL) thickness by spectral-domain (SD) optical coherence tomography (OCT). Background Myopia is the most common ocular abnormality worldwide, and its high subtype is among the leading causes of blindness. Several studies proposed it as a potential risk for glaucoma. However, it is unclear how both are related. RNFL thickness, currently used for glaucoma monitoring, can be the missed link. The aim of this study is to assess the effect of myopia on the peripapillary RNFL thickness by SD-OCT, thus correlating it to glaucoma. Patients and methods Eighty-six eyes of 86 participants were included in this cross-sectional observational study and categorized into low, moderate, and high myopia groups. Study participants underwent thorough ophthalmological examination, autorefractometer, axial length measurement, and perimetry. Peripapillary RNFL thickness was measured in each quadrant using Spectralis SD-OCT. The effects of spherical equivalent, axial length, age, and sex on peripapillary RNFL thickness were evaluated using Pearson's correlation test. Results The mean age was 38.81 ± 7.76 years (range: 25–55 years), mean spherical equivalent was –5.31 ± 3.34 D (range: −0.41 to −12.5 D), with an average axial length of 25.73 ± 1.14 mm (range: 24.0–28.2 mm). The mean RNFL thickness was thinner in highly and moderately myopic eyes (81.77 ± 6.09 and 85.10 ± 5.10 mm, respectively, P = 0.0001) compared with low myopic eyes (98.14 ± 5.59). A significant correlation was noted between spherical equivalent and axial length with peripapillary RNFL thickness (P 0.05). Conclusion High myopia should be considered in the interpretation of OCT data because of thinning of RNFL thickness, and normative database corrected for refractive error and axial length should be incorporated.

Horizontal relative peripheral refraction and astigmatic vector patterns in Chinese young myopic subjects

Background The relationship between the relative peripheral refraction (RPR) of retina and the development of myopia has recently become the concerns for researchers.However, there have been few data on the RPR and the astigmatic vector patterns in myopic populations.It is needed to study the RPR and the astigmatic vector patterns in the Chinese young myopic subjects. Objective The RPR and astigmatic vector patterns were determined in Chinese young myopic subjects. Methods This prospective study comprised 301 Chinese young myopic subjects who visited ophthalmology department of Peking University People's Hospital from June 2014 to October 2015.Horizontal peripheral refractions were measured in 5° steps out to 30° eccentricity in both the nasal and temporal visual fields using Grand Seiko WAM-5500 autorefractor.Only data from the right eyes were used for analyses.Spherical equivalent refractions (SER) at each angular position were calculated and the relative peripheral refractive errors (expressed as defocus) were determined by subtracting the peripheral SER from the central SER.The RPR was categorized based on the shapes of peripheral refractive curves and the relative positions in the nasal or temporal retinal regions.Astigmatism at each angle was decomposed into J0 and J45 vectors based on Fourier decomposition and the curve patterns for the astigmatic vectors were examined.This study adhered to the tenets of the Declaration of Helsinki and was approved by the Human Research Ethics Committee of Peking University People's Hospital. Results Seven types of relative peripheral refractive curves were identified (retinal regions)∶ negative defocus, temporal positive defocus and nasal flatness, temporal positive and nasal negative defocus, temporal flatness and nasal negative defocus, flatness in both temporal and nasal retina, temporal negative defocus and nasal flatness, and positive defocus.Patterns of astigmatic vector J0 and J45 were divided into 9 categories.The rate of type Ⅰ RPR was significantly greater in the moderate and high myopia group than that in the low myopia group (χ2=26.770, P<0.05). The rate of type Ⅲ was significantly greater in the low myopia group than that in the moderate and high myopia group (χ2=12.500, P<0.05). Conclusions The distributions of RPR were significantly different between low myopia group and moderate and high myopia group.There were nasal-temporal asymmetries for the absolute values of astigmatism along peripheral horizontal meridian.The absolute values of astigmatism in the nasal retinal regions were increased with the increase of fixation angles (except for the value at nasal 10°). Key words: Relative peripheral refraction; Myopia; Peripheral defocus

Visual and refractive outcomes of small-incision lenticule extraction in mild, moderate, and high myopia: Six-month results

To evaluate the efficacy, safety, predictability, and stability of small-incision lenticule extraction in low, moderate, and high myopia. Prospective case series. Eyes were divided into a low myopia group (spherical equivalent [SE] refraction -1.00 to -3.00 diopters [D]), moderate myopia group (SE refraction of -3.25 to -6.00 D), and high myopia group (SE refraction -6.25 to -10.00 D). Small-incision lenticule extraction surgery was performed, and outcomes were reported 6months postoperatively. The low myopia group comprised 94 eyes; the moderate myopia group, 95 eyes; and the high myopia group, 85 eyes. There was significant improvement in uncorrected (UDVA) and corrected (CDVA) distance visual acuities, sphere, cylinder, and SE in all groups 6months postoperatively. The difference in postoperative UDVA, sphere, and SE was statistically significant between the low and moderate myopia groups and the high myopia group; however, there was no difference in the CDVA, cylinder, efficacy, or safety indices. The difference between the attempted SE and achieved SE correction was 0.12 D ± 0.14 (SD) in the low myopia group, -0.18±0.02 D in the moderate myopia group, and -0.60±0.03 D in the high myopia group. There was no statistically significant change in the postoperative SE in any group at 3months or 6months. Small-incision lenticule extraction showed acceptable efficacy, safety, predictability, and stability in low, moderate, and high myopia. The tendency toward undercorrection in the high myopia group suggests the need to modify the nomograms of small-incision lenticule extraction in highly myopic patients.

Comparative analysis of the efficacy of astigmatic correction after wavefront-guided and wavefront-optimized LASIK in low and moderate myopic eyes.

To evaluate and compare the efficacy of the astigmatic correction achieved with laser in situ keratomileusis (LASIK) in eyes with myopic astigmatism using wavefront-guided (WFG) and wavefront-optimized (WFO) ablation profiles. Prospective study included 221 eyes undergoing LASIK: 99 and 122 eyes with low and moderate myopic astigmatism (low and moderate myopia groups). Two subgroups were differentiated in each group according to the ablation profile: WFG subgroup, 109 eyes (45/64, low/moderate myopia groups) treated using the Advanced CustomVue platform (Abbott Medical Optics Inc.), and WFO subgroup, 112 eyes (54/58, low/moderate myopia groups) treated using the EX-500 platform (Alcon). Clinical outcomes were evaluated during a 6-month follow-up, including a vector analysis of astigmatic changes. Significantly better postoperative uncorrected visual acuity and efficacy index was found in the WFG subgroups of each group (P≤0.041). Postoperative spherical equivalent and cylinder were significantly higher in WFO subgroups (P≤0.003). In moderate myopia group, a higher percentage of eyes with a postoperative cylinder ≤0.25 D was found in the WFG subgroup (90.6% vs 65.5%, P=0.002). In low and moderate myopia groups, the difference vector was significantly higher in the WFO subgroup compared to WFG (P<0.001). In moderate myopia group, the magnitude (P=0.008) and angle of error (P<0.001) were also significantly higher in the WFO subgroup. Significantly less induction of high order aberrations were found with WFG treatments in both low and moderate myopia groups (P≤0.006). A more efficacious correction of myopic astigmatism providing a better visual outcome is achieved with WFG LASIK compared to WFO LASIK.

Detailed Distribution of Corneal Epithelial Thickness and Correlated Characteristics Measured with SD-OCT in Myopic Eyes.

Purpose To investigate the detailed distribution of corneal epithelial thickness in single sectors and its correlated characteristics in myopic eyes. Methods SD-OCT was used to measure the corneal epithelial thickness distribution profile. Differences of corneal epithelial thickness between different parameters and some correlations of characteristics were calculated. Results The thickest and thinnest part of epithelium were found at the nasal-inferior sector (P < 0.05) and at the superior side (P < 0.05). respectively. Subjects in the low and moderate myopia groups have thicker epithelial thickness than those in the high myopia group (P < 0.05). Epithelial thickness was 1.39 μm thicker in male subjects than in female subjects (P < 0.001). There was a slight negative correlation between corneal epithelial thickness and age (r = −0.13, P = 0.042). Weak positive correlations were found between corneal epithelial thickness and corneal thickness (r = 0.148, P = 0.031). No correlations were found between corneal epithelial thickness, astigmatism axis, corneal front curvature, and IOP. Conclusions The epithelial thickness is not evenly distributed across the cornea. The thickest location of the corneal epithelium is at the nasal-inferior sector. People with high myopia tend to have thinner corneal epithelium than low–moderate myopic patients. The corneal epithelial thickness is likely to be affected by some parameters, such as age, gender, and corneal thickness.

Assessment of Retinal Nerve Fiber Layer Changes by Cirrus High-definition Optical Coherence Tomography in Myopia.

ABSTRACTIntroduction To evaluate the relationship between retinal nerve fiber layer (RNFL) thickness measured by Cirrus high-definition (HD) optical coherence tomography (OCT) and the axial length and refractive error of the eye.Materials and methods A total of 100 eyes of 100 healthy subjects (age 20-34 years with M/F ratio of 57/43), comprising 50 eyes with emmetropia [spherical equivalent (SE) 0 D], 25 eyes with moderate myopia (SE between -4 D and -8 D), and 25 eyes with high myopia (SE between -8 D and -12 D) were analyzed in this cross-sectional study. Average and mean clock hour RNFL thicknesses were measured by cirrus HD-OCT and compared between the three groups. Associations between RNFL measurements and axial length and SE were evaluated by linear regression analysis.Results The average RNFL measurements were significantly lower in high myopia (78.68 +/- 5.67) and moderate myopia (83.76 +/- 3.44) group compared with emmetropia group (91.26 +/- 2.99), also in the superior and inferior mean clock hours. Significant correlations were evident between RNFL measurements and the SE and axial length. The average RNFL thickness decreased with increasing axial length (r = -0.8115) and negative refractive power (r = 0.8397). Myopia also affected the RNFL thickness distribution. As the axial length increased and the SE decreased, the thickness of the superior, inferior, and nasal peripapillary RNFL decreased.Conclusion The axial length/refractive error of the eye affected the average RNFL thickness and the RNFL thickness distribution. Analysis of RNFL thickness in the evaluation of glaucoma should always be interpreted with reference to the refractive status. When interpreting the RNFL thickness of highly myopic patients by OCT, careful attention must be given to the inherently thinner RNFL to avoid a false diagnosis of glaucoma.How to cite this article Singh D, Mishra SK, Agarwal E, Sharma R, Bhartiya S, Dada T. Assessment of Retinal Nerve Fiber Layer Changes by Cirrus High-definition Optical Coherence Tomography in Myopia. J Curr Glaucoma Pract 2017;11(2):52-57.

Evaluation of the Ganglion Cell Complex and Retinal Nerve Fiber Layer in Low, Moderate, and High Myopia: A Study by RTVue Spectral Domain Optical Coherence Tomography

Purpose: To assess the effect of low, moderate, and high myopia on the thickness of the retinal nerve fiber layer (RNFL) and Ganglion cell complex (GCC) measured by Spectral Domain Optical Coherence Tomography (SD-OCT) in non-glaucomatous subjects. Methods: The subjects were divided into three groups: low (n = 81, 35.6%), moderate (n = 79, 34.8%), and highly myopic eyes (n = 67, 29.5%). The RNFL thickness profile, including the average, superior, nasal, inferior, and temporal quadrant and each of the eight directional thicknesses, was measured. GCC parameters, including the average, superior, and inferior values, the focal loss volume (FLV), and the global loss volume (GLV), were measured. The correlation between the OCT measurements and the axial length was evaluated. Results: The average, superior, inferior, and nasal RNFL thicknesses of low and moderate myopic eyes were found to be significantly higher than those of highly myopic eyes. The temporal RNFL thicknesses were not different among the three groups. The average, superior, and inferior ganglion cell complex values of low and moderate myopic eyes were significantly higher than those of highly myopic eyes. The FLV and GLV of low and moderate myopic eyes were significantly higher than those of highly myopic eyes (p = 0.001 for all). In the moderate and high myopia groups, the average RNFL thickness and GCC thickness were both negatively correlated with the axial length. Conclusion: Highly myopic subjects tend to have thinner RNFL and GCC thicknesses than subjects with low and moderate myopia.

Roles of intraocular pressure in different degree of myopia and axial elongation in children

Background The development and progression of myopic eyes is biomechanical and dominated by axial elongation.The biomechanics change of stretching of the fundus and sclera appears to reduce its thickness and elastic modulus, which make eyeballs more susceptible to the distending forces of intraocular pressure (IOP). Objective This study was to analyz the axial length (AL) and IOP changes in different degree of myopia and investigate the roles of IOP in myopia development and AL elongation. Methods A prospective cases-controlled study was performed under the informed consent of patients and custodian.Four hundred and twenty-eight eyes of 428 children aged 4-14 years were enrolled in Affilicated Second Hospital of Zhengzhou University from February to December 2014.The patients were divided into 4 groups based on the refractive status.Ninety-three eyes of 93 patients were in the hyperopic-emmetropia group with the spherical equivalent (SE) of (1.81±2.32)D, 192 eyes of 192 patients were in mild myopia group with the SE of (-1.43±0.74)D, 83 eyes of 83 patients were in the moderate myopia group with the SE of (-4.09±0.89)D and 60 eyes of 60 patients were in the high myopia group with the SE of (-8.02±2.61)D.AL was measured by IOL Master system, IOP was measured by iCare tomnometer, and the central corneal thickness (CCT) was measured by OCT.The corrected IOP was calculated based on IOPcorrection =IOPGAT+ (544-CCT)/37.03.The correlations between IOPcorrection and AL or diopter were analyzed. Results The AL values were (22.44±1.32)mm, (23.89±1.09)mm, (25.05±0.89)mm and (26.47±1.20)mm in the hyperopic-emmetropia group, mild myopia group, moderate myopia group and the high myopia group, showing a significant difference among the four groups (F=177.336, P=0.000). The IOPcorrection values were (15.24±2.73)mmHg, (17.51±2.98)mmHg, (17.94±2.34)mmHg and (18.49±2.90)mmHg in the hyperopic-emmetropia group, mild myopia group, moderate myopia group and the high myopia group, with a significant difference among the four groups (F=22.104, P=0.000). The IOPcorrection values were significantly lower in the hyperopic-emmetropia group than that in the mild myopia group, moderate myopia group and high myopia group (all at P<0.05), and the mean IOPcorrection value in the high myopia group was significantly higher than that in the mild myopia group (P=0.018). The IOPcorrection was negatively correlated with diopter (r=-0.384, P<0.01) and positively correlated with AL (r =0.377, P<0.01). Conclusions As the increase of myopic diopter and elongation of AL, IOPcorrection is considerably elevated in childhood.IOPcorrection rising in childhood probably promotes the progression of myopia and elongation of AL. Key words: Intraocular pressure; Myopia/physiopathology; Refraction, ocular/physiology; Axial length; Children

The Distinct Biometric Features of High Myopia Compared to Moderate Myopia

ABSTRACTPurpose: To evaluate changes in biometric parameters in myopic eyes.Materials and Methods: 412 eyes of 412 young myopic patients underwent ophthalmic examinations including assessments of refractive error, axial length (AL), anterior chamber depth (ACD), and central corneal thickness (CCT). By using spectral domain optical coherence tomography (SD-OCT), peripapillary retinal nerve fiber layer (pRNFL) thickness was measured. Subjects were divided into two groups: a moderate-myope group (−6 diopters (D) or more) and a high-myope group (less than −6 D). The relationships among ocular biometric parameters including pRNFL thickness, AL, ACD, and CCT were calculated for each group.Results: In the moderate-myopia group, the anterior chamber deepened as AL increased (Pearson’s coefficient = 0.346, p < 0.01). However, in the high-myopia group, ACD did not correlate with AL (Pearson’s r = 0.065, p = 0.383). Average pRNFL thickness was also more related to SE than AL in highly myopic eyes.Conclusions: In highly myopic eyes, ACD did not increase as AL increased. pRNFL thickness was more related to SE than to AL. That might be due to the uneven elongation of anterior and posterior portions of the eyeball and the discrepancy between distance from the cornea to the fovea and distance from the cornea to the bottom of the eyeball as axial eye elongation. Interpretation of ocular biometric parameter in highly myopic eyes should consider these differences.

Kappa angles in different positions in patients with myopia during LASIK.

To investigate the difference in kappa angle between sitting and supine positions during laser-assisted in situ keratomileusis (LASIK). A retrospective study was performed on 395 eyes from 215 patients with myopia that received LASIK. Low, moderate, and high myopia groups were assigned according to diopters. The horizontal and vertical components of kappa angle in sitting position were measured before the operation, and in supine position during the operation. The data from the two positions were compared and the relationship between kappa angle and diopters were analyzed. Two hundred and twenty-three eyes (56.5%) in sitting position and 343 eyes (86.8%) in supine position had positive kappa angles. There were no significant differences in horizontal and vertical components of kappa angle in the sitting position or horizontal components of kappa angle in the supine position between the three groups (P>0.05). A significant difference in the vertical components of kappa angle in the supine position was seen in the three groups (P<0.01). Differences in both horizontal and vertical components of kappa angles were significant between the sitting and supine positions. Positive correlations in both horizontal and vertical components of kappa angles (P<0.05) were found and vertical components of kappa angle in sitting and supine positions were negatively correlated with the degree of myopia (sitting position: r=-0.109; supine position: r=-0.172; P<0.05). There is a correlation in horizontal and vertical components of kappa angle in sitting and supine positions. Positive correlations in both horizontal and vertical components of kappa angle in sitting and supine positions till the end of the results. This result still needs further observation. Clinicians should take into account different postures when excimer laser surgery needs to be performed.

Comparison of visual acuity of the patients on the first day after sub-Bowman keratomileusis or laser in situ keratomileusis.

To compare recovery of the visual acuity in patients one day after sub-Bowman keratomileusis (SBK) or laser in situ keratomileusis (LASIK). Data from 5923 eyes in 2968 patients that received LASIK (2755 eyes) or SBK (3168 eyes) were retrospectively analyzed. The eyes were divided into 4 groups according to preoperative spherical equivalent: between -12.00 to -9.00 D, extremely high myopia (n=396, including 192 and 204 in SBK and LASIK groups, respectively); -9.00 to -6.00 D, high myopia (n=1822, including 991 and 831 in SBK and LASIK groups, respectively), -6.00 to -3.00 D, moderate myopia (n=3071, including 1658 and 1413 in SBK and LASIK groups, respectively), and -3.00 to 0.00 D, low myopia (n=634, including 327 and 307 in SBK and LASIK groups, respectively). Uncorrected logMAR visual acuity values of patients were assessed under standard natural light. Analysis of variance was used for comparisons among different groups. Uncorrected visual acuity values were 0.0115±0.1051 and 0.0466±0.1477 at day 1 after operation for patients receiving SBK and LASIK, respectively (P<0.01); visual acuity values of 0.1854±0.1842, 0.0615±0.1326, -0.0033±0.0978, and -0.0164±0.0972 were obtained for patients in the extremely high, high, moderate, and low myopia groups, respectively (P<0.01). In addition, significant differences in visual acuity at day 1 after operation were found between patients receiving SBK and LASIK in each myopia subgroup. Compared with LASIK, SBK is safer and more effective, with faster recovery. Therefore, SBK is more likely to be accepted by patients than LASIK for better uncorrected visual acuity the day following operation.

Posterior Corneal Elevation after Small Incision Lenticule Extraction for Moderate and High Myopia.

PurposeTo investigate the changes of posterior corneal elevation after small incision lenticule extraction (SMILE) for moderate and high myopia.MethodsIn this prospective study, fifty consecutive eyes of thirty patients (10 male, 20 female) who underwent SMILE for myopia and myopic astigmatism were included. Eyes were divided in two groups based on the preoperative spherical equivalent refraction: high myopia group (32 eyes, range -6.25D to -10.00D) and moderate myopia group (18 eyes, range -3.00D to -6.00D). Posterior corneal surfaces were measured by a Scheimpflug camera (Pentacam, Oculus Germany) preoperatively and 1 month, 3 months, 6 months and 12 months postoperatively. Posterior central elevation (PCE) and posterior mean elevation (PME) at 17 predetermined points in the central-4mm area above the best-fit sphere were analyzed.ResultsNo significant difference in the amount of posterior corneal elevation changes in the high myopia group was noted over time (P = 0.23 and P = 0.94 for PCE and PME, respectively). Similarly, the changes in the moderate myopia group before and after SMILE were not significant either (P = 0.34 and P = 0.40 for PCE and PME). A statistically significant correlation was found between the residual bed thickness and the shift of the PCE in the high myopia group at 12 months postoperatively (r = 0.53, P = 0.01).ConclusionsThe results of this study suggest that the posterior corneal surface remain stable within one year after SMILE for both moderate and high myopia. The changes of PCE correlate to the residual bed thickness for high myopia. Long-term changes of posterior corneal surface need further investigation.

Refractive error, visual acuity, and corneal-curvature changes in high and low myopes with orthokeratology treatment: A Malaysian study

Background/PurposeThe effect of orthokeratology (OK) on low myopia is well known, but there are a few reports on its effect on high myopia. In this study, the parametric changes in high and low myopia as results of wearing OK lenses for a period of 6 months have been analyzed. MethodsRecords of schoolchildren (age 7–17 years) undergoing OK treatment from an optometry clinic were retrospectively reviewed. Data involving refractive errors, uncorrected visual acuity, and corneal curvatures at baseline and after 1 day, 1 week, 1 month, 3 months, and 6 months of OK treatment from 25 patients who fulfilled the inclusion criteria were examined. For the analysis, the participants were arbitrarily divided into two groups comprising high myopia (< −6.00 D) and low to moderate myopia (from −1.00 D to −6.00 D). ResultsSignificant reductions of refractive error, improvement in visual acuity, and corneal-curvature flattening were found in all participants after 6 months of OK lens wear compared to the baseline. No significant changes were found in corneal toricity in both high and low to moderate myopic groups. Almost all of these occurred after one night of lens wear in both the high- and low-myopia groups. ConclusionThe OK lens wear significantly reduced the refractive error and corneal curvature that results in the improvement in visual acuity in both high- and low-myopia groups, and the reduction seemed to occur nearly at the same time despite the difference in initial myopic power. High myopes with refractive power up to −8.25 D would benefit significantly from OK lenses.

Posterior corneal curvature changes following Refractive Small Incision Lenticule Extraction

PurposeTo compare the posterior corneal curvature changes, in terms of corneal power and asphercity, following Refractive Small Incision Lenticule Extraction (ReLEx SMILE) procedure for low, moderate, and high myopia.MethodsThis retrospective, non randomized, comparative, interventional trial; included 52 eyes of 26 patients, divided in three groups: low myopia (myopia ≤3 D [diopters] spherical equivalent [SE]), moderate myopia (myopia >3 D and <6 D SE), and high myopia (myopia ≥6 D SE). All patients were treated for myopia and myopic astigmatism using ReLEx SMILE. The eyes were examined pre-operatively and 3 months post-operatively using SCHWIND SIRIUS, a three-dimensional rotating Scheimpflug camera with a Placido disc topographer to assess corneal changes with regard to keratometric power and asphericity of the cornea.ResultsA statistically significant increase in mean keratometric power in the 3, 5, and 7 mm zones of the posterior corneal surface compared with its pre-ReLEx SMILE value was detected after 3 months in the moderate myopia group (pre-operative [pre-op] −6.14±0.23, post-operative [post-op] −6.29±0.22, P<0.001) and high myopia group (pre-op −6.19±0.16, post-op −6.4±0.18, P<0.001), but there was no significant change in keratometric power of the posterior surface in the low myopia group (pre-op −5.87±0.17, post-op −6.06±0.29, P=0.143). Asphericity (Q-value) of the posterior surface changed significantly (P<0.001) after ReLEx SMILE in the moderate myopia group in the 3, 5, and 7 mm zones, and in the high myopia group in the 3 and 7 mm zones; but there was no significant change in the Q-value in the low myopia group in all three zones (pre-op 0.23±0.43, post-op −0.40±0.71, P=0.170), and in the high myopia group in the 5 mm zone (P=0.228).ConclusionReLEx SMILE causes significant changes in posterior corneal keratometric power and asphericity in moderate and high myopia, but the effect is subtle and insignificant in low myopia.

Biomeasurement and analysis of the anterior chamber angle and related tissues in myopia eyes

Background Myopia is one of the main blinding diseases worldwide.At present, a lot of studies on ocular structure focus on the changes of corneal curvature（CC), central corneal thickness (CCT), anterior chamber depth (ACD), ocular axial length (AL) and choroid and retina, but the research of anterior chamber angle section structure form and ciliary body shape is lack. Objective This study was to measure and analyze the changes of the anterior chamber angle and related tissue structure in myopic eyes. Methods One hundred and forty-nine eyes of 149 subjects were included from May 2008 to May 2010 in Eighth Hospital of Qingdao City with the ages of 18-40 years old under the informed consent.The subjects were assigned to the emmetropia group (30 eyes) ([0.02±0.18]D), low myopia group(46 eyes) ([-1.64±0.69]D), moderate myopia group (35 eyes) ([-4.56±0.66]D) and high myopia group(38 eyes) ([-7.04±1.02]D). Conventional indexes including intraocular pressure (IOP), CCT, CC, AL and ACD were measured, and the indexes including chamber angel open distance (AOD), iris thickness (IT1, IT2, IT3), the position of ciliary body such as A-angel, B-angel, trabecular ciliary process distance (TCPD), iris-ciliary process distance (ICPD) and ciliary body thickness (CBT1, CBT2, CBT3) were measured by ultrasound biomicroscope（UBM). Results The IOP, CC and CCT values showed slight change in different groups without remarkable difference among them (all at P>0.05). As the increase of myopic degree, AL was extended and ACD was deepened, showing significant differences among the groups (both at P 0.05). However, the measuring values of angle opening degree (TIA and AOD500), ciliary position (A-angle, B-angle, TCPD, ICPD) and CBT (CBT1, CBT2, CBT3) elevated with the increase of myopic degree (all at P<0.05). Positive correlations were found between AOD500 and ACD, A-angle, CBT1, CBT2, AL, negative correlations was found between AOD500 and myopic degree（r=0.573, 0.513, 0.325, 0.398, 0.542, -0.435, all at P<0.01); Positive correlations were found between TIA and ACD, A-angle, CBT1, CBT2, AL, negative correlations was found between AOD500 and myopic degree（r=0.573, 0.464, 0.276, 0.410, 0.539, -0.435, all at P<0.01). Conclusions Within certain limits, as the increase of myopic degree, ACD deepens, the anterior chamber angle widens, ciliary process thickens and ciliary body backward shifts. Key words: Biometry; Myopia; Microscopy, acoustic; Axial length; Anterior chamber/ultrasonography; Ciliary body/ultrasonography; Anterior chamber angle/ultrasonography

Objective optical quality and intraocular scattering in myopic adults.

To evaluate objective optical quality and intraocular scattering in adults with myopia. This was a cross-sectional study. Patients between 18 and 40 years of age were recruited from those undergoing routine preoperative examinations prior to myopic refractive surgery. The spherical equivalent refraction (SE) ranged from -14.25 to -0.63 diopters (D). Right eyes of 274 subjects were included for factor analyses: 25 eyes were super-high myopia (SE < -9 D), 88 eyes were high myopia (-6 D > SE ≥ -9 D),133 eyes were moderate myopia (-3 D > SE ≥ -6 D), and 28 eyes were low myopia (SE ≥ -3 D). A double-pass system was used to measure the modulation transfer function cutoff frequency (MTFcutoff) and objective scatter index (OSI). Mean MTFcutoff was 32.38 ± 9.73 and 27.61 ± 8.11 cycles per degree (cyc/deg) in the high and super-high myopia groups, significantly lower than 39.92 ± 10.53 and 37.39 ± 8.74 cyc/deg in the low and moderate groups (P < 0.01). Mean OSI was 0.89 ± 0.61 and 1.33 ± 0.65 in the high and super-high myopia groups, significantly higher than in the low and moderate groups, 0.50 ± 0.39 and 0.57 ± 0.44 (P < 0.01). No significant difference was found between the low myopia and the moderate myopia group in any of the parameters (P > 0.05). Other factors such as eye side, sex, and age did not significantly affect optical quality parameters or OSI in this study population (P > 0.05). Optical quality and intraocular scattering varied among individuals with myopia. High myopia has more influence on retinal image quality and scattering than moderate and low myopia. Our study also helps to establish MTFcutoff and OSI standards for Chinese refractive surgery candidates.

Spectral- and time-domain optical coherence tomography measurements of macular thickness in young myopic eyes

PurposeTo evaluate the variation in macular retinal thickness and volume in young Chinese myopic patients using time-domain optical coherence tomography (Stratus TD-OCT) and spectral-domain optical coherence tomography (Cirrus HD-OCT).MethodsNinety-two eyes of 92 myopic subjects were recruited in this study. Based upon spherical equivalence (SE), subjects were divided into two groups: the low to moderate myopia group (-0.5 D ≤ SE < -6.0 D), and the high myopia group (SE ≥ -6.0 D). Stratus TD-OCT and Cirrus HD-OCT were used to compare macular retinal thickness and volume between the two groups. Bland–Altman analysis and Pearson correlation were used to measure agreement between the two OCT systems.ResultsAverage macular retinal thickness and total macular volume measured by Cirrus HD-OCT and Stratus TD-OCT of the low to moderate myopia group were 283.52 ± 12.14 μm and 245.38 ± 8.55 μm, respectively, and 10.08 ± 0.37 mm3 and 6.85 ± 0.26 mm3, respectively, and the high myopia groups were 269.58 ± 10.72 μm and 235.65 ± 7.54 μm, respectively, and 9.71 ± 0.36 mm3 and 6.52 ± 0.25 mm3, respectively. The measurements of the two OCTs showed that macular retinal thickness of the parafovea was significantly lower in the high myopia group compared with the low to moderate myopia group, except at the fovea (all P-values less than 0.001, except at the fovea). Using the Bland–Altman method and Pearson correlation, measurements of macular thickness in nine macular retinal subfields and total macular volumes showed good agreement between the two OCTs in myopic eyes (all P-values less than 0.001), with better agreement in the low to moderate myopia group than in the high myopia group.ConclusionsThe average macular retinal thickness of the fovea did not vary with myopia, while the total volume and retinal thickness of the parafovea were thinner with increasing myopia. There was good agreement between the two OCTs in myopic eyes in all macular subfields, and the Cirrus HD-OCT system provided thicker macular retinal thickness measurements than the Stratus TD-OCT system.Virtual slidesThe virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1683223414107652.

Assessment of corneal biomechanical properties and intraocular pressure in myopic spanish healthy population.

Purpose. To examine biomechanical parameters of the cornea in myopic eyes and their relationship with the degree of myopia in a western healthy population. Methods. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOP), and corneal compensated IOP (IOPcc) were measured using the ocular response analyzer (ORA) in 312 eyes of 177 Spanish subjects aged between 20 and 56 years. Refraction was expressed as spherical equivalent (SE), which ranged from 0 to −16.50 diopters (D) (mean: −3.88 ± 2.90 D). Subjects were divided into four groups according to their refractive status: group 1 or control group: emmetropia (−0.50 ≤ SE < 0.50); group 2: low myopia (−0.75 ≤ SE < 3.00 D); group 3: moderate myopia (−3.00 ≤ SE ≤ −6.00 D); and group 3: high myopia (SE greater than −6.00 D). We analyzed the relationship between corneal biomechanics measured with ORA and SE. Results. CH in the emmetropia, low myopia, moderate myopia, and high myopia groups was 11.13 ± 0.98, 11.49 ± 1.25, 10.52 ± 1.54, and 10.35 ± 1.33 mmHg, respectively. CH in the highly myopic group was significantly lower than that in the emmetropic group (P = 0.07) and low myopic group (P = 0.035); however, there were no differences with the moderate myopic group (P = 0.872). There were no statistically significant differences regarding IOP among the four groups (P > 0.05); nevertheless, IOPcc was significantly higher in the moderately myopic (15.47 ± 2.47 mmHg) and highly myopic (16.14 ± 2.59 mmHg) groups than in the emmetropia (15.15 ± 2.06 mmHg) and low myopia groups (14.53 ± 2.37 mmHg). No correlation between age and the measured parameters was found. CH and IOPcc were weakly but significantly correlated with SE (r = 0.171, P = 0.002 and r = −0.131, P = 0.021, resp.). Conclusions. Present study showed only a very weak, but significant, correlation between CH and refractive error, with CH being lower in both moderately and highly myopic eyes than that in the emmetropic and low myopic eyes. These changes in biomechanical properties of the cornea may have an impact on IOP measurement, increasing the risk of glaucoma.

Macular and retinal nerve fiber layer thickness in myopic children by three-dimensional OCT

To investigate the variations of macular thickness and peripapillary retinal nerve fiber layer (RNFL) thickness in myopic children. A total of 96 eyes from 48 myopic children at department of Ophthalmology, Second Affiliated Hospital of Wenzhou Medical College from September 2010 to March 2012 were enrolled in this study and divided into three groups (low, moderate and high myopia group) according to the severity of myopia. Another 33 eyes from 19 emmetropic children were recruited as control group. The macular thickness and peripapillary RNFL thickness of the myopic children measured by optical coherence tomography were compared with that of the control group. The mean thickness of nasal, superior and inferior regions of outer-ring macular in the high myopia group were 276 µm, 294 µm, 285 µm respectively, which were significantly lower than that in the control group (P < 0.05). The mean thickness of superior of outer-ring macular in the low and moderate groups were 302 µm, 301 µm respectively, and the inferior of outer-ring ones were 288 µm, 283 µm respectively, which were significantly lower than that in the control group (P < 0.05). The temporal region of peripapillary RNFL thickness was significantly greater, and the other six regions of RNFL thicknesses were significantly lower in the high group than in the control group (P < 0.05). The central-1 mm, superior region of inner-ring, temporal and superior region of outer-ring macular thickness had positive correlations with spherical equivalent (SE) (P < 0.05). There was a negative correlation between the temporal peripapillary RNFL thickness and SE, while positive correlations were found between other regions of peripapillary RNFL thickness and SE (P < 0.05). The thicknesses of macular and peripapillary RNFL of myopic children have already redistributed before apparent changes of funds.