The Repeatability of Axial Length Measurements Using a Scheimpflug-based System

Purpose: To assess the repeatability of Pentacam AXL as a Scheimpflug-based system or measuring axial length according to the age, sex, lens type, axial length value, and type of cataract. Methods: The present study was conducted using multistage cluster sampling in Tehran, Iran. Ocular biometry was performed, using the Pentacam AXL, by an experienced optometrist on all the participants. The axial length (AL) measurements were taken thrice, with a gap of 10 minutes. To evaluate the repeatability, the intraclass correlation coefficient (ICC) and the repeatability coefficient (RC) were calculated. To determine the significant difference in the repeatability index among study variables, the tolerance index (TI) was calculated. Results: In this report, 897 eyes of 677 individuals aged between 20 and 91 years (mean ± SD: 64.90 ± 13.62 years) were reported. The ICC of the axial length measurements was 0.981 for all cases. Based on the within-subject standard deviation, the RC was 0.401. The ICC was 0.976 and 0.985 in men and women, respectively. The TI showed better RC of measurements among females. The ICC decreased from 0.999 in participants under 40 years to 0.973 in individuals over 60 years of age. The TI showed a decrease in RC with advancing age. The RC was worse in eyes with nuclear cataracts; the RC was also worse in the first quartile of the signal-to-noise ratio (SNR) compared to the other SNR quartiles. Conclusion: The Scheimpflug-based system Pentacam AXL had high repeatability in measuring axial length. Some variables such as male gender, older age, and nuclear cataract were associated with reduced repeatability of the measurements. A higher SNR was associated with better repeatability of the axial length measurements

Is corneal sensitivity sex dependent?

Purpose: To determine whether corneal sensitivity is different between the two genders. Methods: Corneal sensitivity of 130 normal volunteers, including 77 women and 53 men aged 20-35 years, with no history of previous ocular surgery was measured using the Cochet-Bonnet esthesiometer. Measurements were done on five corneal regions: central, nasal, inferior, temporal and superior. The findings were compared between men and women using the non-parametric Mann-Whitney U test. Results: Mean age of male subjects was 28.0 years and that of female participants was 26.8 years (P = 0.063). There was a significant difference in corneal sensitivity between men and women in the superior (P = 0.013), temporal (P = 0.020) and inferior (P = 0.046) regions. There was no significant difference in corneal sensitivity in the central (P = 0.862) and nasal (P = 0.273) regions. Conclusion: Except for the central and nasal regions, corneal sensitivity is significantly higher in men as compared to women. The reason for this difference is not yet evident. © 2015 Journal of Ophthalmic and Vision Research

Comparison of the wave amplitude of visually evoked potential in amblyopic eyes between patients with esotropia and anisometropia and a normal group

Background: We compared the wave amplitude of visually evoked potential (VEP) between patients with esotropic and anisometropic amblyopic eyes and a normal group.Methods: The wave amplitude of VEP was documented in 2 groups of persons with amblyopia (15 with esotropia and 28 with anisometropia) and 1 group of individuals with normal visual acuity (n, 15). The amplitude of P100 was recorded monocularly with different spatial frequencies.Results: Our statistical analysis revealed that the wave amplitude in the 2 groups with amblyopia was significantly decreased compared to that in the normal group (P<0.001). There was a significant difference regarding the amplitude in high spatial frequencies in both high-and low-contrast conditions between the groups with esotropia and anisometropia and the normal group (P<0.001). There were also significant differences in large check-size stimuli and low-contrast condition between the amblyopic groups with esotropia and anisometropia and the normal group (P=0.013 and P=0.044, respectively). In large check-size stimuli and high-contrast condition, a significant difference was indicated only in the comparison between the esotropic amblyopic eyes and the normal eyes (P=0.036).Conclusion: The wave amplitude parameter of VEP was influenced by both types of amblyopia, but it seems that this parameter was more sensitive to esotropic amblyopia than anisometropic amblyopia. This outcome may reflect a non- parallel pattern of cortical responses in the comparison of the2 types of amblyopia with each other and with the control group, which may be beneficial for the diagnosis and treatment of amblyopia. © 2016, Shiraz University of Medical Sciences. All rights reserved

Low-contrast Pattern-reversal Visual Evoked Potential in Different Spatial Frequencies

Purpose: To evaluate the pattern-reversal visual evoked potential (PRVEP) in lowcontrast, spatial frequencies in time, frequency, and time-frequency domains. Methods: PRVEP was performed in 31 normal eyes, according to the International Society of Electrophysiology of Vision (ISCEV) protocol. Test stimuli had checkerboard of 5% contrast with spatial frequencies of 1, 2, and 4 cycles per degree (cpd). For each VEP waveform, the time domain (TD) analysis, Fast Fourier Transform(FFT), and discrete wavelet transform (DWT) were performed using MATLAB software. The VEP component changes as a function of spatial frequency (SF) were compared among time, frequency, and time–frequency dimensions. Results: As a consequence of increased SF, a significant attenuation of the P100 amplitude and prolongation of P100 latency were seen, while there was no significant difference in frequency components. In the wavelet domain, an increase in SF at a contrast level of 5% enhanced DWT coefficients. However, this increase had no meaningful effect on the 7P descriptor. Conclusion: At a low contrast level of 5%, SF-dependent changes in PRVEP parameters can be better identified with the TD and DWT approaches compared to the Fourier approach. However, specific visual processing may be seen with the wavelet transform

Can hand dexterity predict the disability status of patients with multiple sclerosis?

Background: Multiple Sclerosis (MS) is the most common disabling neurological disease. Hand dysfunction is one of the main complaints of patients with MS. The present study aimed to compare hand dexterity of MS patients with low Expanded Disability Status Scale (EDSS) scores and healthy adults. It also sought to identify the predictors of disability status of patients with MS based on their manual dexterity and demographic characteristics. Methods: In this cross-sectional study, 60 (16 male/44 female) patients with MS and 60 (19 male/41 female) healthy people, who matched in terms of age and sex, were recruited. Their hand dexterity was evaluated by the Purdue Pegboard Test. The disability status of the MS group was determined by the Expanded Disability Status Scale. The data were analyzed using SPSS15. Results: The hand dexterity in MS group even with low EDSS score (1.5 ± 1.07) was weaker than control group. Moreover, the dexterity of dominant hand and alternating two hands coordination subtests of the PPT was a good discriminator between two groups (p<0.001). The results of linear regression analysis suggested dominant hand dexterity and disease duration as predictors of disability status that predict 60.5 per cent of the variation in EDSS scores in patients with MS (p<0.001). Conclusion: Reduced dominant hand dexterity in patients with MS is a disabling factor. Further research is recommended to determine if early hand rehabilitation can reduce the severity of disability in Patients with MS

P100 wave latency in anisometropic and esotropic amblyopia versus normal eyes

Purpose: To evaluate cortical activity using pattern visual evoked potentials (PVEPs) in patients with mild and moderate amblyopia (esotropic and anisometropic). Methods: PVEP was recorded in 43 unilateral amblyopic patients, including 15 esotropic (ET) and 28 anisometropic (AM) patients, selected from three different medical centers in the city of Shiraz, Iran and compared to that obtained from 15 age and sex matched normal subjects who served as controls. Visual acuity (VA) in amblyopic eyes was equal to or less than 0.7 LogMAR. The latency of P100 was recorded monocularly using two check sizes of 15 and 60 min of arcs at two different levels of contrasts (30 and 100). Results: P100 latency in amblyopic eyes was significantly increased compared to the normal group (P < 0.001). There was a significant difference (P < 0.001) in P100 latency in anisometropic and esotropic amblyopic eyes as compared to normal subjects, using high spatial frequency and with both levels of contrast. A significant difference was observed with large check sizes and high contrast between anisometropic amblyopic and normal eyes (P = 0.03). However, there was no significant difference between these two groups and the control group with other stimuli. Conclusion: The neural response based on p100 latency in PVEP was different between amblyopic groups and normal subjects. PVEP may be valuable for diagnosis, prognosis and treatment of amblyopia. © 2015 Journal of Ophthalmic and Vision Research | Published by Wolters Kluwer - Medknow

Comparison of saccadic eye movements and facility of ocular accommodation in female volleyball players and non-players

There is controversy on the interaction of sport exercise and visual functions. Some aspects of visual skills have been evaluated in volleyball players. Eighty-three normal females were categorized in four groups; non-players (NP), beginner volleyball players, intermediate and advanced players. Facility of accommodation and far saccade for optotypes at three distances were measured. The athletes showed better facility of accommodation and saccadic eye movement (SEM) than the non-playing control group. There was a significant difference (P<0.001) between NP and beginner players with advanced players and intermediate players. There are mutual interrelations between the visual system and sensory-motor coordination of the whole body. In a "programed" activity many motor and sensorial elements interactively influence one another. The visual system, as the most important coordinator, navigates the "programed" activities. The facility of accommodation shows how fast clear vision can be accomplished. The SEM shows how fast visual system can fixate on an object. Improvement of these two parameters indicates that the visual system can change fixation very fast and clearly see a new fixation point promptly. These are the requirement for a good volleyball player; hence, we find better visual performance in advanced players than in others. Copyright © 2006 Blackwell Munksgaard

Scotopic contrast sensitivity and glare after accelerated corneal cross-linking

Background: The aim was to assess one-year changes in uncorrected and corrected contrast sensitivity (CS) and glare under scotopic conditions after accelerated cross-linking (CXL) using the 18 mW/cm2 protocol for the treatment of progressive keratoconus and compare results with unoperated controls. Methods: In this non-randomised clinical trial, 30 eyes were enrolled in the CXL group and 30 were assigned to the control group. Scotopic CS at spatial frequencies (SFs) of 0.5, 1.1, 2.2, 3.4, 7.1 and 15 cycles per degree (cpd) were assessed using the MonCv3System (Metrovision, Pérenchies, France) under scotopic conditions (0.5 lux) at baseline and at six and 12 months. Results: The mean ages of the participants in the CXL and control groups were 24.32 ± 5.17 and 30.93 ± 7.43 years, respectively (p &lt; 0.001). After adjusting for age, changes in uncorrected and corrected CS and glare were similar in the two groups (all p &gt; 0.05) except for corrected CS at SF 7.1 cpd (1.45 ± 4.31 versus 3.21 ± 4.69 dB, p = 0.010) and 15 cpd (1.12 ± 4.63 versus 3.03 ± 5.48 dB, p = 0.007), which were reduced as an effect of CXL. Based on covariate analyses, among corrected CS indices, corrected CS7.1 and CS15 were related to CXL and their baseline values (all p &lt; 0.050). Uncorrected CS in all SFs and uncorrected and corrected glare were related to their pre-operative values (all p &lt; 0.001). Conclusion: Accelerated CXL can reduce scotopic corrected CS at SFs higher than 7.0 cpd in cases with better baseline values of these parameters. Changes in uncorrected CS and glare are only a factor of baseline values and the indices reduce in cases with better baseline values after one year. © 2017 Optometry Australi

Frequency Domain Electroretinography in Retinitis Pigmentosa versus Normal Eyes

Purpose: To compare electroretinogram (ERG) characteristics in patients with retinitis pigmentosa (RP) and normal subjects using frequency domain analysis. Methods: Five basic ERG recordings were performed in normal subjects and patients with a clinical diagnosis of RP according to the ISCEV (International Society of Clinical Electrophysiology of Vision) protocol. Frequency domain analysis was performed by MATLAB software. Different frequency domain parameters were compared between the study groups. Results: Peak frequency (Fmod) of flicker and oscillatory responses in RP patients showed significant (P<0.0001) high pass response as compared to normal controls. Peak frequency (Fmod) of the other responses was not significantly different between the two groups. Conclusion: In addition to conventional ERG using time domain methods, frequency domain analysis may be useful for diagnosis of RP. Oscillatory and flicker responses may be analyzed in frequency domain. Fast Fourier transform may reveal two distinct high pass responses (shift to higher frequencies) in Fmod. Time and frequency domain analyses may be performed simultaneously with many modern ERG machines and may therefore be recommended in RP patients