Myopic Subjects Research Articles

Reference Values of the Central Corneal Thickness with Different Refractive Errors for the Adult Egyptian Population.

AimTo generate reference values of the central corneal thickness (CCT) with different refractive errors for the adult eastern Egyptian population.Subjects and MethodsThis study was a retrospective, observational, and cross-sectional study. It included 1166 eyes (1166 subjects) scheduled for LASIK, who came to private refractive eye centre, Ismailia, Egypt. The study period was from January 2018 to January 2020. The subjects were divided into a broad range of myopia with spherical equivalent (SE) ≤-0.5D and hyperopia (SE) ≥+0.5D. Then, the myopic eyes divided into low (SE>-3.0D), moderate (SE-3.0D to >-6.0D), and high (SE≤-6.0D). Similarly, the hyperopic eyes were divided into low (SE<+3.0D) and moderate (SE+3.0D to <+6.0D) and high ≥+6.0D. The refractive error was measured by an auto-refractometer, and CCT was measured using ultrasonic pachymetry.ResultsThe data of 556 myopic eyes in 556 subjects (31.1% males and 68.9% females) and 610 hyperopic subjects (34.4% males and 65.6% females) were included in this study. The mean±SD of CCT for the total myopic subjects was 532.8±32.6μm, range (470 to 627μm). The mean±SD of SE was -4.06±2.50D, range (−0.50 to −14.00D). The mean±SD of CCT for the total hyperopic subjects was 530.8±37.2μm, range (471 to 616μm). The mean±SD of SE was +3.57±1.98D, range (+0.50 to +8.50D). About 16.2% of the myopic eyes and 12.7% of the hyperopic eyes have CCT less than 500μm.ConclusionThe mean of the central corneal thickness of the eastern Egyptian population was 532.8μm for myopic and 530.8μm for hyperopic subjects, respectively. The myopic and hyperopic subjects show a reduction in CCT with age. Females have a thinner cornea than males, 16.2% of the myopic eyes and 12.7% of the hyperopic eyes have CCT less than 500μm.

The Effect of Refractive Error on Melanopsin-Driven Pupillary Responses.

PurposeHuman and animal studies suggest that light-mediated dopamine release may underlie the protective effect of time outdoors on myopia development. Melanopsin-containing retinal ganglion cells may be involved in this process by integrating ambient light exposure and regulating retinal dopamine levels. The study evaluates this potential involvement by examining whether melanopsin-driven pupillary responses are associated with adult refractive error.MethodsSubjects were 45 young adults (73% female, 24.1 ± 1.8 years) with refractive errors ranging from –6.33 D to +1.70 D. The RAPDx (Konan Medical) pupillometer measured normalized pupillary responses to three forms of square-wave light pulses alternating with darkness at 0.1 Hz: alternating long wavelength (red, peak at 608 nm) and short wavelength (blue, peak at 448 nm), followed by red only and then blue only.ResultsNon-myopic subjects displayed greater pupillary constriction in the blue-only condition and slower redilation following blue light offset than subjects with myopia (P = 0.011). Pupillary responses were not significantly different between myopic and non-myopic subjects in the red-only condition (P = 0.15). More hyperopic/less myopic refractive error as a continuous variable was linearly related to larger increases in pupillary constriction in response to blue-only stimuli (r = 0.48, P = 0.001).ConclusionsRepeated light exposures to blue test stimuli resulted in an adaptation in the pupillary response (more constriction and slower redilation), presumably due to increased melanopsin-mediated input in more hyperopic/less myopic adults. This adaptive property supports a possible role for these ganglion cells in the protective effects of time outdoors on myopia development.

Association between ocular dominance and refraction in myopic subjects

Objective: To determine the association between ocular dominance and myopic-astigmatic characteristics in myopic subjects. Methods: Cross-sectional study. A total of 1 503 myopic subjects visiting from the myopiac clinic from December 2011 to December 2012 were included. The spheres and cylinders were recorded. The ocular dominance was determined by the hole-in-the-card test. The average spherical equivalent (SE) and the cylinder between the dominant eyes and the non-dominant eyes were compared with the paired t test. The associations between ocular dominance laterality and refractive characters were analyzed with the crosstab Chi-square test. Results: There were 527 males and 976 females in this study. The median (min, max) of age was 24 (17, 49) years old. Among the subjects, 66.00% (992/1 503) of subjects were right-eye dominant, while 34.00% (511/1 503) of subjects were left-eye dominant. The dominant eyes had significantly lower average sphere powers ［(-5.01±1.91) D vs. (-5.10±1.99) D］ and lower average cylinder powers ［(-0.70±0.68) D vs. (-0.76±0.73) D］ than the non-dominant eyes (t=2.976, 4.319; both P<0.01). In the subgroups of |ΔSE|≤0.50 D, 0.50 D<|ΔSE|≤1.00 D, 1.00 D<|ΔSE|≤2.00 D and |ΔSE|>2.00 D, respectively, the dominant eyes were lower myopic in 49.37% (355/719), 51.10% (163/319), 58.48% (100/171) and 65.56% (59/90) of the subjects. The inter-group difference was statistically significant (χ²=11.588, P=0.009). In the subgroups of |ΔCyl|≤0.25 D, 0.25 D<|ΔCyl|≤0.50 D and |ΔCyl|>0.50 D, the dominant eyes had lower astigmatism in 53.94% (89/165), 65.66% (65/99) and 69.70% (46/66) of the subjects, respectively. The inter-group difference was statistically significant (χ²=6.414, P=0.040). Conclusion: The ocular dominance laterality is significantly associated with lower myopia and lower astigmatism in the myopic subjects. (Chin J Ophthalmol, 2020, 56: 693-698).

Alteration of the pattern of regenerative corneal subbasal nerves after laser in‐situ keratomileusis surgery

Corneal nerves exhibit high plasticity, which allows successful reinnervation after nerve damage caused by laser in-situ keratomileusis (LASIK) surgery. This study aimed to examine corneal subbasal nerve orientation during regeneration after LASIK. This study involved 20 healthy, myopic subjects who had undergone bilateral Femto-LASIK 12-16months prior with a superior hinge position. The corneal subbasal nerve plexus at the central, mid-temporal and mid-superior cornea on the right eye were imaged using in vivo confocal microscopy. Global nerve fibre orientation (indicating the overall pattern) and variation of nerve fibre orientation (indicating the consistency of the orientation) was determined using customised MATLAB™ software (www.mathworks.com/products/matlab.html). Differences in nerve orientation variables between groups were examined using the Mann-Whitney U test. Linear mixed models with Bonferroni adjustment were conducted to examine differences between corneal regions, and over time, after LASIK. There were no differences between post-LASIK and control groups in global nerve orientation at any of the examined corneal regions. The post-LASIK subjects had a greater variation of nerve orientation at the central (p=0.007) and temporal (p=0.049) cornea than the controls. There was a difference in global nerve fibre orientation between corneal regions (p<0.001) in the controls but not in the post-LASIK group. The variation of nerve fibre orientation was higher at the central, compared to the temporal and superior cornea after LASIK (p<0.001), although there were no differences between corneal regions in controls. Our results demonstrate that there was an increased variability in the corneal subbasal innervation patterns following LASIK when compared to controls.

Genetic and environmental factors related to the development of myopic maculopathy in Spanish patients.

High myopia and the subsequent degenerative changes of the retina, choroid, and sclera, known as myopic maculopathy (MM), are a serious visual problem in many Asian countries, and are beginning to be so in the south of Europe, especially in the Mediterranean. It is therefore necessary to carry out genetic and environmental studies to determine the possible causes of this disease. This study aims to verify if the genetic factors that have been most related to Asian populations are also associated in two Spanish cohorts. Eight SNPs from six genes (PAX6, SCO2, CCDC102B, BLID, chromosome 15q14, and COL8A1) along with demographic, ophthalmic and environmental factors were analysed in two cohorts from a total of 365 highly myopic subjects and 177 control subjects. The genetic analysis showed that COL8A1 SNP rs13095226 was associated with the development of choroidal neovascularization (CNV) and also seems to play an important role in the increase of axial length. The SNP rs634990 of chromosome 15q14 also showed a significant association with MM, although this was lost after the Bonferroni correction. Additional demographic and environmental factors, namely age, sex, smoking status, and pregnancy history, were also found to be associated with MM and CNV in this population.

Altered spatial summation optimizes visual function in axial myopia

This study demonstrates significant differences between the area of complete spatial summation (Ricco’s area, RA) in eyes with and without non-pathological, axial myopia. Contrast thresholds were measured for six stimuli (0.01–2.07 deg2) presented at 10º eccentricity in 24 myopic subjects and 20 age-similar non-myopic controls, with RA estimated using iterative two-phase regression analysis. To explore the effects of axial length-induced variations in retinal image size (RIS) on the measurement of RA, refractive error was separately corrected with (i) trial lenses at the anterior focal point (near constant inter-participant RIS in mm), and (ii) contact lenses (RIS changed with axial length). For spectacle corrected measurements, RA was significantly larger in the myopic group, with a significant positive correlation also being observed between RA and measures of co-localised peripheral ocular length. With contact lens correction, there was no significant difference in RA between the groups and no relationship with peripheral ocular length. The results suggest RA changes with axial elongation in myopia to compensate for reduced retinal ganglion cell density. Furthermore, as these changes are only observed when axial length induced variations in RIS are accounted for, they may reflect a functional adaptation of the axially-myopic visual system to an enlarged RIS.

Effect of optical correction by fully corrected glasses on postural stability.

Although various previous studies have reported that the experimentally induced refractive errors interfered with postural control, few studies have demonstrated the optical correction effect of wearing glasses. The purpose of this study was to investigate whether wearing full corrected glasses to correct myopia and hyperopia can have a positive effect on postural stability. To this end, a total of 34 subjects (19 males and 15 females) of an average age of 22.38 ± 2.41-years-old participated in this study. After measuring the full corrected powers of refractive errors of subjects through subjective refraction, updated glasses were provided to 17 myopic subjects and first time glasses were provided to 17 hyperopic subjects as full corrected glasses, respectively. Postural evaluation was carried out using the TETRAX biofeedback system, after which we compared and analyzed the postural instability index and sway power index before and after wearing full corrected glasses. When updated and old glasses for correcting myopia were worn, the postural instability index was significantly reduced, and the sway power index was statistically decreased only in the mid-high frequency region associated with the somatic system, compared to the no glasses state, respectively. However, after wearing first time glasses for hyperopia correction, no significant difference was found in the postural instability index or sway power index. We suggest that providing optimal visual information through the optical correction of myopic refractive error is a useful approach that can lead to synergistic effects of somatic functions involved in postural control. Consequently, we demonstrated that wearing glasses to fully correct the refractive errors has a positive effect on increasing postural control in static posture. Our results may have important clinical implications in the field of optometry and balance evaluation.

&lt;p&gt;Contributions of Anterior Corneal and Ocular Residual Astigmatism to Autorefraction Astigmatism in a Myopic Adult Sample&lt;/p&gt;

AimTo evaluate the contributions of anterior corneal and ocular residual astigmatism to autorefraction astigmatism in adult myopic and myopic astigmatic subjects and how these compensate each other.Subjects and MethodsThis retrospective study was completed in private eye centre, Ismailia, Egypt, between September 2017 and November 2019. The study included eyes with myopia (0.5 to 10.0D) or myopic astigmatism (0 to 8.5D). The refractive errors, including autorefraction astigmatism, were measured after using 1% cyclopentolate with autorefractometer (Topcon, Tokyo Optical Co., Ltd., Japan). Corneal topography (Sirius; CSO, Florence, Italy) was used to measure anterior corneal astigmatism. Ocular residual astigmatism was measured by vectorial subtraction of the anterior corneal astigmatism from autorefraction astigmatism determined to the corneal plane.ResultsThis study included 1158 eyes (right 582 and left 576) with myopia or myopic astigmatism of 582 participants (206 males with 406 eyes and 376 females with 752 eyes). The mean±SD age of the total participants was 26±5.7 years, range (21 to 50 years). The mean±SD of spherical error was −3.2±1.9D, range (−0.5 to −10.0D). The mean±SD of autorefraction astigmatism was 1.13±1.1D; range (0.5 to 8.5D). The mean±SD of anterior corneal astigmatism was 1.22±0.8D; range (0.03 to 5.6D). The mean±SD of ocular residual astigmatism was 0.6±0.5D; range (0 to 4.8D). Of the total eyes, 75.4% had significant autorefraction astigmatism, 82.5% had significant anterior corneal astigmatism, and 16.8% had significant ocular residual astigmatism.ConclusionThe percentage of the significant autorefraction astigmatism (>0.5D) was 75.4% which is mainly anterior corneal. In 26.8% of participants, anterior corneal astigmatism is compensated by ocular residual astigmatism.

Volumetric Choroidal Segmentation Using Sequential Deep Learning Approach in High Myopia Subjects.

Many ocular diseases are associated with choroidal changes. Therefore, it is crucial to be able to segment the choroid to study its properties. Previous methods for choroidal segmentation have focused on single cross-sectional scans. Volumetric choroidal segmentation has yet to be widely reported. In this paper, we propose a sequential segmentation approach using a variation of U-Net with a bidirectional C-LSTM(Convolutional Long Short Term Memory) module in the bottleneck region. The model is evaluated on volumetric scans from 40 high myopia subjects, obtained using SS-OCT(Swept Source Optical Coherence Tomography). A comparison with other U-Net-based variants is also presented. The results demonstrate that volumetric segmentation of the choroid can be achieved with an accuracy of IoU(Intersection over Union) 0.92.Clinical relevance- This deep learning approach can automatically segment the choroidal volume, which can enable better evaluation and monitoring at ocular diseases.

Agreement of Central Corneal Thickness Measurements between Scheimpflug Photography and Optical Low-Coherence Reflectometry in Children

ABSTRACT Purpose Central corneal thickness (CCT) is a key indicator of the corneal health status and is therefore of clinical importance. The aim of the present study was to determine the agreement between Scheimpflug photography (SP) and optical low-coherence reflectometry (OLCR) systems in measuring the CCT in children. Methods In this cross-sectional study, the samples were selected from Shahroud schoolchildren using cluster sampling. The samples then underwent optometric examinations, including the measurement of visual acuity and refraction. CCT measurements were done by the SP and OLCR systems between 8 am and 4 pm. To evaluate the agreement between these devices, 95% limits of agreement (LoA) and interclass correlation coefficient (ICC) were reported. Results After applying the exclusion criteria, 4890 right eyes (53.2% male) were analyzed. The mean age of the students was 9.22 ± 1.72 years (range: 6–12 years). The mean CCT by the SP and OLCR systems was 555.30 ± 34.15 and 550.23 ± 35.11 µm, respectively. The 95% LoA between the two devices was −19.81 to 9.66 µm, and the ICC was 0.983. The CCT difference between the SP and OLCR systems was 5.61 µm in boys and 3.36 µm in girls. The CCT difference between the two devices was 6.41 µm in 6-year-old and 3.54 µm in 12-year-old children. The 95% LoA was −17.96 to 9.58 µm and −18.89 to 8.47 µm and the ICC was 0.987 and 0.984 in myopic and hyperopic subjects, respectively. Conclusion The results of this study showed a high agreement between OLCR and SP measurements of CCT in children.

Performance of Topological Perception in the Myopic Population

ABSTRACT Purpose: Discriminating objects’ topological property (TP) is a primitive function of visual representation, which is reported to be associated with magnocellular (M) visual pathway, temporal lobe (TL), and superior colliculus (SC)-pulvinar subcortical pathway. Previous studies have shown that M pathway and TL were affected in high myopia (HM) subjects. The study was accordingly designed to explore whether topological perception performance was abnormal in HM subjects. Methods: 30 mildly myopic, 25 moderately myopic, 35 highly myopic, and 20 emmetropic subjects were enrolled. All participants underwent a comprehensive ophthalmological assessment including automated refraction, intraocular pressure, Humphrey 10–2 standard automated perimetry, ocular fundus photography and swept-source optical coherence tomography. Defined by differences in hole, TP and non-TP discrimination with letters “E”, “S”, “P”, “d” as stimuli in the central and peripheral regions was performed using the MATLAB 2017 software. d-primes extracted from the software were analyzed within each group. The correlation of peripheral TP/non-TP deficit with spherical equivalent (SE), axial length (AL) and average peripapillary retinal nerve fiber layer (RNFL) thickness was performed. Results: The patterns of topological perception performance were similar among the groups. TP discrimination peripherally was significantly better than that centrally in the mild myopia (P < .001), moderate myopia (P < .001), high myopia (P < .001) and emmetropia groups (P = .001). In the peripheral region, TP d-prime scores were significantly better than non-TP d-prime scores (all P < .001). The main and interaction effects of eccentricity and stimulus type were statistically significant(P < .05). There was no statistically significant correlation between peripheral TP/non-TP deficit and SE, AL or average RNFL thickness (P > .05). Conclusions: The current study first showed that patterns of topological perception among the myopic population were similar and not affected by the severity of myopia.

Standard Correction of Vision Worsens EMG Activity of Pericranial Muscles in Chronic TMD Subjects

Recent studies showed an evident correlation between the stomatognathic system and the visual system. These results suggest that subjects who are affected by both temporomandibular (TMD) disorders and refractive disorders present with altered control of pericranial musculature tone and higher open-eye electromyographic (EMG) values. The objective of this work was to evaluate the effects of standard vision correction on EMG in subjects suffering from TMD compared with application of the same vision treatments to non-TMD subjects. 40 subjects were enrolled in this study. The test group included 20 myopic subjects and also included patients with TMD. The control group included 20 healthy myopic subjects. All of the participants underwent a complete ocular examination and a sEMG analysis. The results showed that TMD subjects with vision disorders that are corrected with standard glasses present EMG values that are significantly higher than those presented by non-TMD subjects with vision disorders and standard glasses. Infact, in TMD subjects, eye correction did not have a positive effect on the stomatognathic or pericranial musculature.

Generalized Convex Hull Pricing for the AC Optimal Power Flow Problem

We study an abstract myopic electricity market subject to general nonconvex power flow models and convex generator models (without discrete commitment variables) in a setting where there may be no market equilibrium that guarantees revenue adequacy of the independent system operator. A generalized version of convex hull prices (CHPs) are proposed and are defined to solve a novel multiobjective minimum uplift problem that captures the tradeoff between generator side-payments and potential congestion revenue shortfall (PCRS). A convex primal counterpart of this multiobjective minimum uplift problem, called the primal CHP problem , is formulated in terms of the convex hull of the set of feasible net power injections. Indeed the term convex hull price derives from the result that the CHPs are equivalent to the optimal Lagrange multipliers of the primal CHP problem . However, depending on the chosen model of the transmission network, the convex hull of the feasible set of net power injections may be intractable to evaluate. In this case, CHPs are approximated using state-of-the-art convex relaxations that are efficiently solvable. This is the first proposed method of approximating CHPs in polynomial-time that is general enough to accommodate the nonlinear transmission constraints in the AC optimal power flow (OPF) problem. In our abstract myopic market setting, we show that tight relaxations of the AC OPF problem can be used to effectively approximate CHPs that decrease potential congestion revenue shortfall significantly with little effect to side-payments.

Quantitative assessment of the retinal microvasculature and choriocapillaris in myopic patients using swept-source optical coherence tomography angiography.

To study the retinal capillary microvasculature and the choriocapillaris (CC) in myopic eyes using swept-source optical coherence tomography angiography (SS-OCTA). Patients with high myopia (≥ - 6D; axial length ≥ 26.5mm), moderate myopia (≥ - 3D, < - 6D), and age-matched healthy subjects presenting to the Shanghai General Hospital and Doheny-UCLA Eye Centers were enrolled in this prospective, multicenter study. Any subjects with evidence of macular abnormalities suggestive of pathologic myopia were excluded. SS-OCTA at both sites was performed using a Zeiss PLEX Elite instrument with a 6 × 6mm scan pattern centered on the fovea. Two repeated volume scans were acquired for image averaging. The instrument pre-defined en face slab of the superficial and deep retinal capillary microvasculature was used to isolate and display the superficial and deep retinal capillaries. A slab spanning from 21 to 31μm deep to the RPE fit line was used to isolate and display the CC. The OCTA images were exported for averaging using Image J. Littmann's method and the Bennett formula were applied to adjust for the impact of magnification in the high and moderate myopia groups. The resultant images were then binarized. Though projection artifact removal software was used, regions below the large superficial retinal vessels were excluded for quantitative analyses of the deep retinal capillary plexus and the CC. Vessel density (VD) and vessel length density (VLD) of the superficial and deep retinal capillary plexus (SCP, DCP) and CC flow deficit (FD) were analyzed, quantified, and compared between different groups. Twenty-five eyes of 25 patients with high myopia, 25 eyes of 25 patients with moderate myopia, and 25 eyes of 25 normal age-matched controls were included in this study. The VD of the SCP was lower in the high myopia group compared with the emmetropic control groups (p < 0.05), but the VD of the DCP demonstrated no significant difference among the three groups (p > 0.05). The VLDs of the SCP were lower in the high and moderate myopia groups compared with the control group (p < 0.05), while the VLD of the DCP was lower in the high myopia group compared with the moderate myopia and emmetropic control group (p < 0.05). The CC FD% in the high myopia group was significantly greater than both the control and moderate myopia subjects (p < 0.05). Of note, the severity of the CC flow deficit was not correlated with choroidal thickness (p > 0.05). The retinal microvasculature may demonstrate alterations in highly myopia eyes. The CC in macular regions shows greater impairment in eyes with high myopia compared with eyes with lesser degrees of myopia, and these deficits are already present in the absence of features of pathologic or degenerative myopia. The threshold of CC FD leading to myopic maculopathy remains to be defined.

Association of macular thickness with parapapillary atrophy in myopic eyes

BackgroundTo investigate whether macular structure could be affected by axial elongation and to determine the association between macular intraretinal thickness and the microstructure of β-zone parapapillary atrophy (PPA) in myopic eyes.MethodsThe study recruited 113 healthy myopic subjects (113 eyes). Images of the macula, subfoveal choroid, and optic nerve head were acquired using spectral-domain optical coherence tomography (SD-OCT). An automatic segmentation algorithm was used to segment the macular images into 7 intraretinal layers. PPA widths with and without Bruch’s membrane (PPA+BM and PPA-BM, respectively) were evaluated. Linear regression analysis was performed to evaluate the association between macular intraretinal thickness and axial length and the microstructure of PPA.ResultsAn increase in axial length was associated with a decrease in whole macular thickness of the peripheral region and an increase in whole macular thickness of the central region. Thickness alterations of the macular intraretinal layers were most apparent in the peripheral region. A significant correlation was found between PPA-BM width and macular intraretinal layer thickness, whereas no significant correlation was found between PPA+BM width and macular intraretinal layer thickness. Moreover, both PPA+BM and PPA-BM widths significantly correlated with subfoveal choroidal thickness.ConclusionsMacular intraretinal layer thickness may be affected by PPA-BM width. These findings indicate that the microstructure of PPA should be considered when evaluating the macula in patient with myopia and glaucoma.

The impact of intraocular pressure fluctuations and other factors on conversion of ocular hypertension to primary open-angle glaucoma.

To evaluate the role of intraocular pressure (IOP) fluctuations and other factors on conversion of ocular hypertension to open-angle glaucoma (OAG) within a retrospective, longitudinal cohort study. The study population included patients with ocular hypertension defined by IOP > 21mmHg with normal appearing optic discs and no visual field defect. IOP fluctuation, mean and maximum were examined in 61 eyes over a follow-up period of 36months (standard deviation (SD) 24). All patients underwent at least two 48-h IOP profiles including night-time IOP measurements in the supine position, visual field examinations, Heidelberg retina tomograph analyses (HRT) and optic disc photographs. Regression analyses were performed to demonstrate the impact of IOP parameters, myopia, sex, cup/disc ratio and visual field results on conversion to glaucoma. While IOP fluctuation and mean did not impact conversion, myopia proved to be a risk factor (HR 14.4; 95% CI: [3.9-53.0]; p ≤ 0.001). Over an average of three years, 6/61 converted to OAG. The study yielded a mean long-term IOP over all available pressure profiles of 18.1mmHg (SD 3.2) and an IOP fluctuation of 1.9mmHg (SD 1.1) within a mostly treated cohort. Conversion-free five-year rate was 59.8%. The amount of fluctuation we measured in our study sample did not result in the development of glaucoma in treated ocular hypertension patients. Myopic subjects with ocular hypertension are at a higher risk for glaucoma conversion than non-myopic ocular hypertensive subjects are.

Contrast sensitivity function with soft contact lens wear

PurposesTo compare contrast sensitivity function (CSF) with soft contact lens (SCL) and spectacles wear. To investigate the effect of a three-month period of SCL wear on CSF. MethodsForty-seven myopic subjects with no history of contact lens (CL) wear were included in this longitudinal prospective study. CSF was measured with spectacles using the CSV-1000 (VectorVision, Greenvile, OH). Subsequently, subjects were fitted with a daily disposable lens (Nelfilcon-A, Stenofilcon-A or Nesofilcon-A) in one eye and a monthly disposable lens (Lotrafilcon-B, Comfilcon-A or Balafilcon-A) in the other eye and wore the same type of CLs for three months. CSF was measured again on the same day and after three months wearing CLs. Differences in CSF with spectacles and CLs on baseline and changes to CSF after three months of CLs wear were assessed. The effect of lens materials and wearing modality on CSF change was also investigated. ResultsCSF was higher with CLs in comparison to the values with spectacles for spatial frequencies of 3, 6 and 12 cycles per degree (cpd) (p<0.05) while there was no difference for spatial frequency of 18 cpd (p=0.114). No significant difference was found in the CSF with CLs between baseline and after three months of lens wear (p>0.05). There was no difference in CSF between hydrogel and silicone CLs as well as when comparing daily with monthly wear CLs (p>0.05). ConclusionCSF is better with CLs than with spectacles. CSF values with CL are similar between baseline and after 3 months of lens wear.

Evaluation of the Function of Ganglion Cells in Myopic Patients Using Pattern Electroretinogram (PERG)

<i>Objective</i>: Assessment of the macular ganglion cells function in myopic subjects using pattern electroretinogram (PERG) in comparison with healthy controls to help in diagnosing of retinal diseases, and studying the relationship of the changes seen in PERG with the axial length (AL) of the eye. <i>Methods</i>: The study was cross sectional, included 62 subjects (121 eyes). Three groups were examined: group 1: controls or emmetropics; group 2: mild myopics; group 3: moderate myopics. For all participants, a detailed pathological story was taken, a comprehensive eye examination was performed, AL was measured, and PERG was recorded, then the variables of the recorded waves (peak time and amplitude) were analyzed. <i>Results</i>: A statistically significant decrease in mean amplitudes of (P50, N95) waves was observed in group 2 (36 eyes) and 3 (25 eyes) compared to group 1 (60 eyes) (P-value <0.01), and a statistically significant elongation of mean N95 peak time was observed in (group 2 and 3) compared to group 1 (P-value <0.01) without being associated with elongation of mean P50 peak time. By studying the relationship between AL and each of peak time and amplitude of (P50, N95) waves, we have found that when AL increased, amplitudes decreased and peak times prolonged in a statistically significant way (P-value <0.01). <i>Conclusion</i>: The decreased amplitude of P50 wave may indicate a functional impairment of the macula in myopic subjects, and the decreased amplitude of N95 wave may be due to a functional impairment of their ganglion cells. The elongation of P50 peak time with increasing of AL may be due to a delay of the synaptic transmission between photoreceptors, bipolar cells, and ganglion cells.

Repeatability of Manual Measurement of Foveal Avascular Zone Area in Optical Coherence Tomography Angiography Images in High Myopia

PurposeTo analyze the repeatability of manual measurement of foveal avascular zone (FAZ) area in an optical coherence tomography angiography (OCTA) image in high myopia.MethodsThis study comprised patients with high myopia and controls. Two consecutive FAZ areas of the superficial and deep capillary plexus were obtained using OCTA. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) were assessed, and univariate and multivariate generalized linear mixed models were conducted to identify factors related to repeatability.ResultsThirty eyes with high myopia and 34 eyes of healthy subjects were included in the study. The mean age in high myopia and control subjects was 55.5 and 60.8 years, respectively, the mean spherical equivalent was −9.98 and −0.55 diopters, and the mean axial length was 28.0 and 23.9 mm. The ICCs of FAZ area of the superficial capillary plexus (SCP) were 0.891 and 0.919, while the CVs were 8.8% and 8.5%. In measurement of the deep capillary plexus, the ICCs were 0.788 and 0.907, while the CVs were 11.2% and 11.0%, which were acceptable but exhibited lower repeatability than those of SCP. Multivariate analyses showed that older age (p = 0.030) and greater axial length (p = 0.005) were significantly associated with lower repeatability of SCP FAZ area measurements. In addition, greater axial length (p = 0.044) was a significant factor for lower repeatability of deep capillary plexus FAZ area measurements.ConclusionsManual measurement of FAZ area using OCTA exhibited relatively good repeatability for high myopia. Age and axial length affected repeatability and should be considered when analyzing FAZ areas in high myopia patients.

Plastic modification of human cornea in vivo: applications to clinical refractive procedures.

Purpose:The purpose of this report is to quantify how pressure applied to the human cornea, either physiological or intentional, affects its curvature. In particular, how pneumatic procedures flatten the central cornea and keep it flat over time, thereby decreasing the patient’s myopia.Methods:A viscoelastic model is developed for plastic deformation which gives us the basic governing equations of the elastic and plastic strain of corneal stroma. The model is applied to data from corneas of six patients who underwent pneumatic keratology (NEumatica Keratologia) to reduce their myopia.Results:The model shows corneal dimensional stability for long periods of time after NEumatica Keratologia that decay with an exponential time constant. Separate equations are developed that relate corneal plastic strain to the pressure applied and its duration ε = σ0 t1/η1, to change in refraction ε = 2 × ΔRefr, to keratometry radius increase ε = ΔR/R, and to corneal thinning ε = sqr (Δh/h). The average values obtained for ε from the patients’ data are 3%, 3.2%, 3%, and 2.6%, respectively, all in remarkable agreement. The average refraction change is found to remain stable at ΔRefr = +1.67D ± 5.2%. Clinical data yield good agreement of theory and treatment results.Conclusions:The model proposed is a good description of NEumatica Keratologia outcomes. Practical applications include the long-term stable correction of myopia with refractive procedures. High myopia subjects can benefit from this procedure because NEumatica Keratologia corrects and protects the central cornea radius by stretching the peripheral cornea.