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AIM: To determine the corneal sensitivity recovery period after laser-assisted sub-epithelial keratectomy (LASEK) refractive surgery and investigate the effects of ablation depth on it. METHODS: In this study examinations were performed on 90 right eyes of 90 people (34 males and 56 females) with an age range of 20-35 and an average of 22.26±3.8 years old. A sensation of 5 corneal regions, including the center and 4 mid-peripheral regions, i.e., nasal, inferior, temporal, and superior, each at a distance of 2 mm from the center of the cornea were measured with a Cochet-Bonnet esthesiometer device in 3-time points including before LASEK, 1 and 3mo after the surgery, respectively. LASEK was performed on individuals with stabilized myopia of -1.00 to -7.00 diopters and astigmatism of less than 2.00 diopters. Furthermore, the individuals were divided into three groups regarding ablation depth. RESULTS: The highest level of corneal sensitivity before surgery was related to the center of the cornea (59.1±7.76), and the highest level of corneal sensitivity loss was also related to this region. The sensation of all measured corneal regions significantly reduced 1mo postoperatively and returned to their preoperative levels 3mo after surgery (mean of 5 corneal regions in levels of preoperation: 58.2±6.48, 1mo postoperation: 57.3±5.84, 3mo postoperation: 58.2±5.49; P

AIM: To determine the agreement of ocular biometric indices including axial length, keratometric readings, anterior chamber depth, and horizontal corneal diameter between the Pentacam AXL and IOL Master 500. METHODS: The study was a large cross-sectional population-based study (Tehran Geriatric Eye Study) conducted from Jan 2019 to Jan 2020. A total of 160 clusters were randomly selected proportional to size (each cluster contained 20 individuals) from 22 strata of Tehran city. All people aged 60y and above were invited to participate in the study. For all participants, preliminary ocular examinations were performed including the measurement of uncorrected and best-corrected visual acuity, objective and subjective refraction, anterior and posterior segment examinations. All participants underwent an ocular biometry using the Pentacam AXL and IOL Master 500. RESULTS: The 95% limits of agreement (LoA) between the two devices were -0.13 to 0.19, -0.15 to 0.17, and -0.13 to 0.19 in normal, pseudophakic, and cataractous eyes, respectively. With increasing the axial length, the difference between the two devices significantly increased in all three groups of normal, pseudophakic, and cataractous eyes (P

Abstract Purpose: To determine the long-term effects of night shift work on dry eye in hospital nurses. Methods: Each participant was evaluated four times, including at the beginning of the day shift (8 am), at the end of the day shift (2 pm), at the beginning of the night shift (8 pm), and at the end of the night shift (8 am), using the tear break-up time (TBUT) test and ocular surface disease index (OSDI) questionnaire. Results: The results showed significant differences in the TBUT and OSDI between the end of the day shift (2 pm) (10.26, 16.61) and the end of the night shift (8 am) (6.89, 38.59) relative to each other and relative to the beginning of the day and night shifts. As for the correlation between TBUT and OSDI, a significant correlation was found at all measurement times (correlation coefficient: - 0.478, - 0.707, - 0.556, and - 0.365, respectively) (p < 0.05). Conclusion: The results showed that the severity of dry eye increased after the night shift with variation over a 24-hr period. Moreover, a significant correlation was observed between TBUT and OSDI results at the beginning and at the end of the day and night shifts.

Abstract 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 systemPentacam 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.

AIM: To compare anterior segment parameters between two groups of type 2 diabetic with and without diabetic retinopathy (DR) and non-diabetic elderly subjects based on hemoglobin A1c (HbA1c) levels and status of DR. METHODS: This study was conducted on 997 residents aged 60y or over in Tehran, Iran. Diabetic group had HbA1c level ≥6.4% with no other systemic problems. The non-diabetic participants had normal eye findings and no systemic diseases. K1, K2, mean K, Q-value, anterior, central, posterior, and total corneal densitometric findings, anterior chamber volume (ACV), anterior chamber depth (ACD), corneal volume (CV), and pachymetry were measured by Pentacam AXL. RESULTS: A total of 678 non-diabetic (39% male) and 319 diabetic (35% male) subjects with mean age of 66.31±5.23 and 67.22±4.96y were examined, respectively. No statistically significant difference was found in anterior segment parameters between non-diabetic and diabetic groups (all P>0.05). However, middle, posterior, and total corneal densitometric values were statistically different between two groups after controlling the effects of confounders (P=0.014, 0.007, and 0.042, respectively). Corneal densitometric values in all layers, ACD, and ACV were different between diabetic subjects with and without DR (all P

To compare Modulation Transform Function (MTF) between standard monofocal spherical hydrophobic acrylic Alcon SA60AT (Bausch and Lomb) and hydrophilic acrylic Rayner Superflex (620H) (Rayner) intra-ocular lenses (IOLs). This cross-sectional study was conducted on 68 patients who underwent cataract surgery. The hydrophobic Alcon SA60AT IOL was implanted in 39, and the hydrophilic Rayner Superflex (620H) was implanted in 29 eyes. The OPD Scan III (Nidek) was used to assess MTF in normal pupils under mesopic light conditions 1 and 3 months after the surgery. t-test showed no significant difference in mean MTF between the two IOLs in the 2 follow-ups (P=0.788). The results of repeated measure ANOVA for each type of IOL indicated that MTF increased significantly in the hydrophilic group versus the hydrophobic group in the 3rd month (P=0.033). Moreover, the results of repeated measure ANOVA showed that MTF was affected by the type of IOL and refractive error in the 3rd month (P=0.029, P=0.025). It seems that the material of IOL and post-surgical residual refractive error can affect the visual acuity of pseudophakic patients. Although the hydrophilic IOL provided a better MTF three months after the surgery, studies with longer follow-ups are required to confirm the results.

Background and Objectives: We aimed to investigate the variation of heterophoria during a day in students with a normal visual system. Methods: This cross-sectional observational study was conducted on 15 students aged 19 to 22 years with 20/20 visual acuity and normal binocular vision. Heterophoria was measured with a prism bar and alternate cover test at near and far distances (40 cm and 6 m). The measurement was performed from 8 to 10 PM in one day with 2 hours intervals. Results: The Mean±SD age of students was 21.6±0.87 years (63% women and 37% men). The mean deviation in far and near order was 1.93 and 3.75 prism diopter, respectively. The Greenhouse-Geisser test concluded no significant difference between the measurements of distant heterophoria during the day (F=1.362, df=3.066, P=0.267). However, the near-distance results were significant (F=15.17, df=7, P˂0.05). The paired t-test results showed that the highest amount of exophoria was observed near 4 PM, which was significantly different from the initial value, and the difference increases at the end of the day so that the mean difference of the initial near exophoria value from 4 to 10 PM reached from -1.254 to -3.508. Conclusion: Changes in refractive error or high order aberration increase near work and decrease the illumination during a day can induce force on accommodation and vergence. So, at the end of the day, the exophoria increases. Thus, it is preferable to perform eye examinations at the end of the day to make more accurate decisions about the diagnosis and treatment of patients.

Background and Objectives: Keratoconus is a non-inflammatory asymmetric corneal degenerative disease characterized by the steepening and distortion of the cornea. In this disease, irregular astigmatism makes the subjective refraction difficult. Using the Pentacam, we aimed to determine the corrective astigmatism of the spectacle. Methods: The subjective refraction and Pentacam imaging were performed for 317 keratoconic patients who referred to the Salouti Eye Clinic, Shiraz, Iran. Then, the astigmatism values obtained with subjective refraction were compared with the values of anterior and posterior corneal surface astigmatism obtained with the Pentacam imaging. Results: The mean age of 317 keratoconic patients was 29.81 years (range: 15 to 45 years). The minimum, maximum, and average astigmatism of the corneal front surface were 0.3, 16.8, and 3.21 diopters, respectively. Also, the minimum, maximum, and average astigmatism of the corneal back surface were 0, 2.8, and 0.67 diopters, respectively. Moreover, the P value was lower than 0.001 in the regression analysis of the subjective refraction for both the power and axis of the cylinder. Conclusion: The regression formulas obtained in this study can accurately (with a probability of 99%) predict refractive astigmatism, using corneal astigmatism.

Background and Objectives: The color vision evaluation of gas station workers in Isfahan City. Methods: This cross-sectional comparative study was performed on workers at gas stations in Isfahan; all the workers were men. The participants were divided into two 40-people groups of exposure and non-exposure (the members of the fuel sales department). The participants had better vision than 8/10 and no underlying problems or eye disease. Besides, examination, including color vision was performed for all subjects. Color vision was assessed using the D15 test under high to medium light conditions. Also, the color vision test was performed monocularly. Then, the obtained data were analyzed using SPSS V. 22. Results: The two study groups significantly differed in terms of color vision impairment index (P

Purpose: To evaluate the pattern-reversal visual evoked potential (PRVEP) in low-contrast, 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.

Purpose: To evaluate the diagnostic value of visual evoked potentials (VEPs) and to find out which test setting has the most sensitivity and specificity for amblyopia diagnosis. Methods: Thirty-three adult anisometropic amblyopes were intended in this study and were tested for visual evoked potentials with different stimulus conditions including three spatial frequencies [1, 2, and 4-cycles-per-degree (cpd)] at four contrast levels (100, 50, 25, and 5%). We also tested psychophysical contrast sensitivity and compared the results with electrophysiological ones. We plotted Receiver Operating Characteristic (ROC) curve for each VEP recording and psychophysical contrast sensitivity to evaluate the area under the curve, sensitivity, specificity, and cut-point value of each test stimulus for detecting amblyopic eyes. Results: Thirty-three amblyopic and 33 non-amblyopic eyes were examined for psychophysical contrast sensitivity and VEPs. Area under the ROC curve (AURC) findings showed that VEP with different stimulus settings can significantly detect amblyopic eyes, as well as psychophysical contrast sensitivity test. We found that P100 amplitudes had the largest AURC in response to stimuli of 2-cpd spatial frequency at 50 (P

Objective: To determine visual skills in primary school children with poor performance in reading and writing. Methods: This cross-sectional study was conducted on 28 poor-performances in reading and writing students from 600 schoolchildren, based on their teacherchr('39')s score and 14 control children in second to sixth grade in one of the primary schools of Tehran. Visual acuity, refractive error, distance and near horizontal heterophoria, amplitude and facility of accommodation, amplitude and facility of vergence were measured in all subjects of both groups. Results: Statistical comparison showed a higher hyperopia (p

Background and Objectives: Several studies have investigated the correlation between sleep and tear film among adults, senior high school students, employees and animals. The aim of this study is to evaluate the correlation between sleep quality and tear film tests among university students. Materials and Methods: A total of 102 students (52 men and 50 women) were enrolled in this cross-sectional study. Their sleep quality was evaluated using the Pittsburgh standard questionnaire and their tear film by the Schirmer-1 test and the tear film break up time (TBUT). Results: Out of 102 participants in this study, 69(67.6%) students had poor sleep quality and 64 (62.7%) students based on TBUT and 17(16.7%) students based on Schirmer-1 test had dry eye. There was a significant relationship between the Pittsburgh Sleep Quality Index (PSQI) and the Schirmer-1 test (correlation coefficient:-0.409, P

Purpose: This study aimed to evaluate two psychophysical contrast sensitivity testing methods in amblyopic patients. Methods: Thirty-three adults with anisometropic amblyopia participated in this study. Psychophysical contrast sensitivity was measured for both amblyopic and fellow eyes of the participants at 1, 3, and 5 cycles per degree (cpd) spatial frequencies by Freiburg visual acuity and contrast test (FrACT) and Metrovision contrast sensitivity test, which employ sine-wave gratings for measurement of contrast sensitivity. We evaluated the correlation between the two tests and used Bland–Altman analysis to measure the agreement between the two methods. Results: Except for 1 cpd in amblyopic eyes, FrACT showed significantly higher contrast sensitivity measurements than Metrovision at all spatial frequencies both in normal and amblyopic eyes (P

Background and Objective: This study investigates stereopsis and its correlation with refractive errors in Iranian 7-year-old schoolchildren. Methods: This cross-sectional study included 3,675 first-grade primary school students in seven cities of Iran. The subjects were randomly selected and evaluated after obtaining an informed consent letter from their parents. There were two inclusion criteria: no systemic diseases and no medication use. Refractive errors were examined with an auto refractometer and stereopsis was measured using the TNO test. Data were analyzed by SPSS 21 and using independent t-test, ANOVA, and post hoc tests. Results: The results of the present study showed that the rate of stereopsis in all students was 43.97±11.75 arcsec and there was a significant difference between the mean of stereopsis in females (43.30±10.62 arcsec) and males (44.59±12.66 arcsec) (P

Background and Objective: Glare can affect vision in normal and abnormal individuals. It seems that threshold and normal values of glare have been less mentioned in various sources. The aim of this study was to determine acuity preserve in glare situation in normal subjects. Methods: 48 subjects (96 eyes) aged 18 to 25 years with normal visual acuity, and without any refractive error participated in this study. The acuity preserve in glare situation was measured at different light intensity conditions with Metro vision glare test at different luminance and visual field. Results: Glare source in each luminance at the nasal side may show better acuity preserve in glare situation. The maximum score for nasal and temporal source for 1 cd/m2 condition was 57.398 and 51.282 respectively. The same situation was seen for 5 cd/m2 (P

Introduction: to identify the pattern-reversal visual evoked potential (PRVEP) waveform descriptor by evaluating discrete wavelet transform (DWT) in order to optimize stimulus in the diagnosis of anisometropia amblyopia. Materials and Methods: The PRVEP testing was performedfor 31 normal individuals and 35 patients with amblyopia. The stimuli were consisted of spatial frequencies of 1, 2, and 4 cycles per degree (cpd) and contrast levels of 100%, 50%, 25%, and 5%. The results were analyzed in the dimensions of time and time-frequency. DWT descriptor were extracted at level 7 (7P descriptor) for Haar, Daubechies 2, Daubechies 4, Symlet 5, Biorthogonal 3.5, Biorthogonal 4.4, and Coiflet 5 wavelets for 12 stimuli and compared between the two groups. The correlation between different spatial frequencies at the same contrast level and the similarities between reconstructed signals and original waveforms were evaluated. Results: There were a significant reduction in P100 amplitude and a significant elevation in latency among the patient group. In the patients with amblyopia, 7P descriptor decreased in all analysis except for the frequency of 4 cpd and the contrast of 5% using bior4.4. No significant correlation was observed between different frequencies at a special contrast; however, there was a significant correlation between reconstructed signals and the original ones. Conclusion: The 7P descriptor could be used to distinguish between normal and abnormal signals in anisometropia amblyopia. Considering the results, DWT with coif5, db4, bior4.4, and bior3.5 wavelets can be utilized as a good indicator for selecting optimum stimulus.

Abstract farsi Background and Objectives: One of the main health problems of concern is refractive error in children, which has a real burden on community and individuals especially among schoolchildren. The study aim is to evaluate the refractive errors’ prevalence in primary school children. Methods: The study was a cross sectional with the element of analysis which was carried out in a primary school of the Amara city. A total of 768 children were selected randomly from 76 primary schools (urban rural, male and female schools) by cluster sampling according to the geographic area of health districts and their primary health care centers. Each child was examined for visual acuity (both uncorrected and best corrected) dry and cyclo- refraction. Results: In this study, the response rate was (95.7%) from which 66.1% were male and 33.9% were female. The prevalence of refractive error was 47% (360) distributed as myopia, hyperopia, and astigmatism which was (19.6%, 20.1% and 7% respectively) while amblyopia was 4.8%. 39.9% of students showed abnormal visual acuity. After cyclo-refraction, the prevalence of refractive error was changed for all types, most of myopic children were female (52.1%) while most children with hyperoia (53.4%) and astigmatism (54.7%) were male children with statistical significant association (P= 0.001). Conclusion: we concluded that refractive error and visual acuity loss prevalence was high among children of primary school in the Amara city in south of Iraq. It seems that an extensive ocular and visual screening protocol must be considered in this province.

Purpose: To assess the diagnostic power of the Corneal Visualization Scheimpflug Technology (Corvis ST) provided corneal biomechanical parameters in keratoconic corneas. Methods: The following biomechanical parameters of 48 keratoconic eyes were compared with the corresponding ones in 50 normal eyes: time of the first applanation and time from start to the second applanation [applanation-1 time (A1T) and applanation-2 time (A2T)], time of the highest corneal displacement [highest concavity time (HCT)], magnitude of the displacement [highest concavity deformation amplitude (HCDA)], the length of the flattened segment in the applanations [first applanation length (A1L) and second applanation length (A2L)], velocity of corneal movement during applanations [applanation-1 velocity (A1V) and applanation-2 velocity (A2V)], distance between bending points of the cornea at the highest concavity [highest concavity peak distance (HCPD)], central concave curvature at the highest concavity [highest concavity radius (HCR)]. To assess the change of parameters by disease severity, the keratoconus group was divided into two subgroups, and their biomechanical parameters were compared with each other and with normal group. The parameters' predictive ability was assessed by receiver operating characteristic (ROC) curves. To control the effect of central corneal thickness (CCT) difference between the two groups, two subgroups with similar CCT were selected, and the analyses were repeated. Results: Of the 10 parameters compared, the means of the 8 were significantly different between groups (P 0.05). ROC curve analyses showed excellent distinguishing ability for A1T and HCR [area under the curve (AUC) > 0.9], and good distinguishing ability for A2T, A2V, and HCDA (0.9 > AUC > 0.7). A1T reading was able to correctly identify at least 93% of eyes with keratoconus (cut-off point 7.03). In two CCT matched subgroups, A1T showed an excellent distinguishing ability again. Conclusions: The A1T seems a valuable parameter in the diagnosis of keratoconic eyes. It showed excellent diagnostic ability even when controlled for CCT. None of the parameters were reliable index for keratoconus staging. Keywords: Keratoconus, Cornea, Corvis ST, Biomechanics

Purpose: To determine the distribution of negative relative accommodation (NRA) and positive relative accommodation (PRA) and its relationship with binocular vision indices in a young population. Methods: In this cross-sectional study conducted in a student population, samples were selected through multistage cluster sampling. All the samples underwent the measurement of uncorrected and corrected visual acuity and refraction. Then far and near cover tests were performed. The near point of convergence (NPC) and accommodation, accommodation facility, PRA and NRA were evaluated in all participants. Results: The mean age of the 382 participants was 22.5 ± 4.4 years (18–35 years). Mean NRA and PRA in the total sample was +2.08 ± 0.33 diopter (D) and −2.92 ± 0.76 D, respectively. Mean NRA was highest in hyperopic (P = 0.002) and mean PRA was highest in myopic (P = 0.003) participants.The multiple model showed that NRA had a direct relationship with accommodation facility and spherical refractive error, while PRA had a direct relationship with amplitude of accommodation (AA). Conclusion: This study provides the normal range of the NRA and PRA and their relationship with accommodation facility, spherical refractive error, and AA in a sample of the Iranian population. Keywords: Negative relative accommodation, Positive relative accommodation, Population based study, Accommodation facility

Purpose: To compare the visual responses of post refractive surgery's patients using Early Treatment Diabetic Retinopathy Study Chart (ETDRS) and E-chart with and without color filters. Methods: The uncorrected Logarithm of the Minimum Angle of Resolution Visual Acuity (LogMAR VA) of 70 patients with a mean age of 26.2 ± 3.76 years (from 19 to 34 years) who had undergone Photorefractive Keratectomy (PRK) (the range of post operation refractive error: ±0.5 D) was measured under the light conditions of with and without asymmetrical glare by using red, green, and yellow filters and ETDRS chart and E-chart. Results: In both light conditions of with and without glare, the mean visual acuity of the three filters in the right and left eyes was significantly better with the E-chart versus the ETDRS chart (P

Purpose: To determine the short-term effect of rigid gas permeable (RGP) contact lenses on corneal aberrations in keratoconic patients. Method: Sixteen keratoconic eyes with no history of RGP lens wear were included. They all had corneal aberrometry using Pentacam, and different aberration indices of the anterior and posterior surfaces of the cornea were measured before and 3 months after fitting RGP lenses. The effect of baseline parameters on these changes was tested in univariate and multiple models. Results: Total aberrations and individual Zernike coefficients did not show statistically significant changes after using RGP lenses. Although not statistically significant, vertical coma decreased in the anterior (p = 0.073) and posterior surface (p = 0.095). Relationships that remained statistically significant in the multiple model were between baseline central corneal thickness and changes in total higher order aberrations and anterior 4th order astigmatism 0°, and between baseline 2nd order astigmatism 45° and its changes. Conclusion: In this study, corneal aberrations remained unchanged 3 months after wearing RGP contact lens. Further studies with sufficient samples in different groups of keratoconus severity or baseline aberrations are needed to obtain more accurate results.

Purpose: To evaluate the correlation between refractive, corneal, and residual astigmatism and higher order aberrations (HOA) in refractive surgery candidates. Methods: Three hundred and seventy-five eyes of 188 patients aged 28.2 ± 6.24 years with a predominance of females (62.7%) were enrolled in this study. Refraction, topography (Orbscan IIz, Bausch & Lomb, Rochester, NY, USA), and aberrometry (Zywave, Bausch & Lomb, Rochester, NY, USA) were performed to determine refractive and corneal astigmatism and HOA for all participants. Ocular residual astigmatism was calculated using vector analysis. Results: The mean spherical equivalent was −3.59 ± 1.95 D and the mean refractive astigmatism was −1.97 ± 1.3 D. The mean HOA was 0.38 ± 0.15 μm in all cases, which increased with spherical equivalent (p

Purpose: To determine the effect of the cyclopentolate 1% on the cylindrical and spherical components of the refraction. Methods: Three hundred seventy-five eyes of 195 subjects, including 74 males and 121 females, aged from 3 to 59 years were refracted before and 30 min after cyclopentolate 1% eye drop instillation. To compare cylindrical data, power vector analysis (J0 and J45 cross cylinder) was applied. Results: A statistically significant difference between the J0 values of the noncycloplegic and cycloplegic refraction was revealed (P = 0.006) while the J45 values did not significantly differ. 95% limit of agreement for dry and cycloplegic values of the J0 and J45 were −0.22 to 0.25 and −0.19 to 0.20, respectively. Astigmatism difference was separately analyzed in emmetropic, myopic and hyperopic eyes. The J0 difference was significant (P = 0.014) only in hyperopic eyes. Spherical equivalent (SE) values in cycloplegic refraction were significantly more hyperopic than those yielded in dry refraction by mean difference of +1.16 ± 1.20 diopters (P

Purpose: To estimate the fitting parameters of the hybrid contact lens in patients with corneal ectasia using the rigid gas permeable (RGP) lens. Methods: Thirty-four eyes with corneal ectasia were evaluated in this study. The patients were examined once with the RGP lens and once with the hybrid contact lens. The relationship between the base curvature of the RGP and the vault of the hybrid lens and the correlation between their powers were analyzed. Results: We found a linear relationship between the base curvature of the RGP lens and the vault of the hybrid lens (P

Purpose: To investigate the effect of a lubricating drop on optical quality, tear film stability, and subjective symptoms in individuals wearing silicone hydrogel contact lens. Methods: In this one-day, prospective single-center clinical study, Pre-lens Tear Deformation Time (PL-TDT), Root-Mean-Square (RMS) of Low Order Aberrations (LOA) and High Order Aberrations (HOA), individual twelve Zernike coefficients, and subjective symptoms were assessed in 43 volunteers (mean age 19.58 ± 1.63, 86 eyes) at 6 h after inserting the contact lens and then at 60 min after instilling a lubricating drop (Comfort drops, Avizor, Madrid-Spain). Results: PL-TDT, LOA-RMS, and HOA-RMS values measured before drop instillation were not significantly different with those measured after drop. None of the Zernike coefficients were significantly different after instilling lubricating drop. Statistically significant decrement in both frequency and severity values in blurry vision, dryness, discomfort, burning, itching, foreign body sensation, excessive blinking, and lacrimation were seen after drop instillation (all P < 0.05). Conclusion: Our results showed that although the lubricating drop did not improve the tear film stability and optical quality in the silicone hydrogel contact lens wearers, subjects experienced a subjective improvement.

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

Purpose: To determine the effect of using toric soft contact lenses on corneal biomechanical properties. Methods: We enrolled 33 healthy patients with mean age of 23.18 ± 4.06 and minimal cylinder power of 1 D (-1.98 ± 0.808 SD) and negative history of contact lens use; keratoconic patients were excluded from the study. Toric soft contact lenses (BIOFINITY, Comfilcon A, Coopervision, Southampton, UK) were fitted in all participants. The Ocular Response Analyzer (Reichert Ophthalmic Instruments, Depew, New York, USA) was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), and the Pentacam HR (Oculus, Inc., Lynnwood, WA, USA) was used to measure central corneal thickness (CCT) and mean keratometry (K mean) before and one week, one month, and three months after using the toric soft contact lenses. Results: CH and CRF were decreased significantly one month after using the contact lens; mean CH decreased from 9.99 ± 1.44 to 9.59 ± 1.54 mmHg, and mean CRF decreased from 9.96 ± 1.71 to 9.63 ± 1.73 mmHg (P = 0.013 and P = 0.017, respectively). Mean CCT and K mean did not show a significant change during the period of toric soft contact lens use. Conclusion: CH and CRF decreased significantly one month after fitting toric soft contact lenses while CCT and K mean did not change significantly. Corneal biomechanical parameters may alter with toric soft contact lens use and such changes may have implications with long-term use such lenses.

Purpose: To determine the distribution of Zernike coefficients and higher order aberrations in a normal population and its relationship with age, gender, biometric components, and spherical equivalent. Methods: During the first phase of the Shahroud cohort study, 6311 people of the 40-64-year-old population of Shahroud city were selected through random cluster sampling. A subsample of participants was examined with Zywave aberrometer (The Bausch & Lomb, Rochester, NY) to measure aberrations. Measurements of aberrations were done before cycloplegic refraction, and values generated from a minimum pupil diameter of 5 mm were reported in this analysis. Results: After applying exclusion criteria, 904 eyes of 577 people were analyzed in this study and mean age in this study was 49.5 ± 5.7 years and 62.9% were female. Mean root-mean-square (RMS) of the third−, fourth−, and fifth-order aberrations was 0.194 μm (95%CI: 0.183 to 0.204), 0.115 μm (95%CI: 0.109 to 0.121), and 0.041 μm (95%CI: 0.039 to 0.043), respectively. Total RMS coma (Z3−1, Z31, Z5−1, Z51), Total RMS trefoil (Z3−3, Z33, Z5−3, Z53), and spherical aberration (Z40) in the studied population was 0.137 μm (95% CI:0.129–0.145), 0.132 μm (95% CI: 0.123–0.140), and −0.161 μm (95%CI:−0.174 to −0.147), respectively. Mean higher-order Zernike RMS in this study was 0.306 (95% CI: 0.295–0.318) micrometer, and in the multiple model, it significantly correlated with older age and short axial length. The highest amounts of higher-order RMS were observed in hyperopes, and the smallest in emmetropes. Increased nuclear opacity was associated with a significant increase in HO RMS (p

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.

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.

Purpose: To evaluate multifocal electroretinogram (mfERG) changes in eyes with diabetic macular edema (DME) and investigate any possible correlation with optical coherence tomography (OCT) features and visual acuity (VA). Methods: Twenty-nine right eyes of 29 subjects with DME due to non-proliferative diabetic retinopathy and 30 eyes of 30 normal subjects were evaluated. All patients underwent a complete ophthalmic examination. Sixty-one scaled hexagon mfERG responses were recorded. Components of thefirst order kernel of N1, N2, and P1 in five concentric rings centered on the fovea, were measured in both groups. Correlation and regression analyses were performed among VA, central macular thickness (CMT) based on OCT, mfERG amplitude, and latency of the N1, N2 and P1 waves. Results: Significant differences were observed in all mfERG parameters in five-ring regions of the retina between eyes with DME versus controls (P < 0.05). There were significant correlations among VA with N2 (P = 0,001, b = 0.73) and P1 amplitudes (P = 0.001, b = −0.84) in the central macular area, and there was a borderline association between VA and CMT (P = 0.042, b = 0.392). Conclusion: Amplitudes of mfERG components (N1, P1, and N2) are significantly reduced and their latencies are delayed in eyes with DME indicating functional impairment in the outer retina. The mfERG total amplitude was significantly correlated with VA even more than CMT, therefore the combined use of OCT and mfERG for macular evaluation may better evaluate visual status in DME patients.

Background: To determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the National Vision Screening Program for 7 yr old children in Iran. Methods: In this cross-sectional study, eight cities in Iran were selected through multistage cluster sampling. Selected cities were Sari, Birjand, Ardabil, Mashhad, Bandar Abbas, Dezful, Yazd, and Arak, in Iran in 2013. Totally, 4614 schoolchildren were selected, 4106 of which participated in the study. An optometrist at the school site conducted all vision tests. Results were compared against those recorded on each child’s health card. Those with an uncorrected visual acuity worse than 20/25 in at least one eye screened positive for a vision problem. Results: 8.49% [95% confidence interval, 7.65 to 9.39] of the examinees had a vision problem. The sensitivity rate of the school entry screening was 38.15% (95% CI, 33.01 to 43.50) and the specificity rate was 93.11 (95%CI 92.25 to 93.90). The positive and negative predictive values were 33.93 (29.24 to 38.88) and 94.19 (93.39 to 94.93), respectively. Sensitivity and specificity rates did not significantly differ between boys and girls. For the uncorrected visual acuity tested by public health care workers compared to optometrists, the area under the ROC surface was 0.741 (P

Introduction: Although there is a consensus about the importance of vision perception in reading, its role in development of dyslexia is highly debated. In order to understand the relationship between dyslexia and disorders of visual perception, we have compared color opponent contrast sensitivity in dyslexic children with that in normal subjects. Materials and Methods: 3 dyslexic and 3 normal children participated in this study. Their responses to stimuli produced by means of “Pattern Generator” software were recorded in three spatial frequencies: 5, 8, and 18 cycles per degree (cpd). In each spatial frequency, contrast sensitivity test was executed in two different levels (pattern detection and color discrimination) once in yellow background and once again in blue background. Results: In general, there was no significant difference between dyslexic and normal children in almost all the tests performed. Nevertheless, dyslexic subjects have shown reduced sensitivity in pattern detection both in yellow and blue backgrounds, yet they had better sensitivity than normal subjects in color discrimination. Conclusion: The results from comparison between dyslexic and control groups showed that color contrast sensitivity cannot be a proper differential indicator for dyslexia. It suggests that dyslexia does not affect all functions of the visual system. However, in dyslexia we may have anomalous perceptual responses even with normal basic and primary visual functions. Keywords: Dyslexia, Vision, Contrast Sensitivity, Color Opponent

Purpose: To compare the visual acuity outcome of the ClearKone SynergEyes™ hybrid contact lens and Boston XO rigid gas permeable (RGP) contact lens in patients with keratoconus. Methods: Twenty-eight eyes with keratoconus participated in this study. The visual acuity was examined once with the RGP lens and once with the ClearKone SynergEyes™ hybrid contact lens. Results: The mean corneal keratometry, the mean lens back optic zone radius, and the mean vault was 7.23 ± 0.62 mm, 7.67 ± 0.44 mm, and 277.94 ± 104.5 μm, respectively. Visual acuity was significantly better with the ClearKone SynergEyes™ hybrid lens (P = 0.004). The mean best corrected visual acuity (logMAR) was 0.022 ± 0.03 and 0.057 ± 0.09 for the ClearKone and RGP lens, respectively. The Clearkone lens yields an average improvement of one line of the Snellen chart in comparison with the RGP lens. Conclusion: The ClearKone hybrid contact lens and the RGP lens may improve visual acuity in corneal irregularities. But patients who are able to afford hybrid lens wearing may show better visual acuity.

Purpose: There are a few researches regarding the effects of Islamic fasting on visual system. The aim of this study was to investigate the effects of Ramadan fasting on the amplitude of accommodation (AA), near point of convergence (NPC), positive and negative fusional vergences (PFV and NFV, respectively) in visually healthy fasters. Methods: AA, NPC, PFV and NFV at far (6m) and near (40cm) were measured in 30 male students. Nutritional habits in a week before each examination visit were assessed with the Food Frequency Questionnaire (FFQ). Results: Mean age and fasting average experience were 23.9 and 10 years, respectively. AA and NPC showed significant changes (pConclusion: Some visual problems may be reported at far and near visual tasks during Ramadan; but most of the problems may be resolved after it. Some visual preparations may be needed for more effective visual activities during Ramadan; essentially for students with intensive visual tasks. Vision therapy may be suggested along with nutrient pattern improvement during Ramadan.

Background: The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran. Methods: In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE) cyloplegic refraction. Results: From 4614 selected children, 89.0% participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04% (95% CI: 2.30-3.78), 6.20% (95% CI: 5.27-7.14), and 17.43% (95% CI: 15.39-19.46), respectively. Prevalence of myopia (P=0.925) and astigmatism (P=0.056) were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95% CI: 1.01-2.05) times higher in girls (P=0.011). The prevalence of with-the-rule astigmatism was 12.59%, against-the-rule was 2.07%, and oblique 2.65%. Overall, 22.8% (95% CI: 19.7-24.9) of the schoolchildren in this study had at least one type of refractive error. Conclusion: One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade.

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

Purpose: To evaluate tear film stability and optical aberrations in eyes wearing plano Lotrafilcon B contact lenses (CL). Methods: Tear Deformation Time (TDT) and aberrometric parameters were assessed in 86 normal emmetropic eyes before and 6 h after wearing CL. Result: A statistically significant decrease in TDT and increase in root mean square (RMS) values of higher order aberrations (HOA) were revealed 6 h after CL insertion (both P

Objective: Nowadays, many infertile couples can have child by assistant reproductive technology (ART). Always the undesirable effects of these methods on newborn are considered and are evaluated. The aim of this study is to describe the impact of ART on ocular and visual performances of infants born by these methods. Materials and methods: In a cross-sectional descriptive study, 479 infants aged three-nine months presented to an optometry clinic of Child Health and Development Research Department (CHDRD), Tehran, Iran. Static retinoscopy, qualitative fixation evaluation, Hirschberg test, red reflex assessment and external eye examination were carried out. Other information such as birth weight and maturity of the infants was recorded. Results: It was possible to assess only 320 out of 479 infants due to general condition of some participants. Comparison of mean refractive error in infants' right and left eyes did not show any significant difference. Our findings confirmed that 20.3% had poor fixation, while 2.9% revealed manifest strabismus. The results also revealed the prevalences of myopia, hyperopia and emmetropia are 2.9%, 87%, and 10.1%, respectively. Red reflex abnormalities were significantly found in boys and in preterm infants (p < 0.05). Failure of fixation control was seen more frequently with increasing refractive error, which significantly developed in preterm infants (p < 0.001). Conclusion: These results reflect the necessity of more comprehensive assessments and further follow-up of infants born by ART, especially for premature male ART infants. These results also suggest the probability of fixation condition and visual deficiencies in these infants. It is recommended to pay close attention to this preliminary report about the refractive and fixation condition of the infants born after ART.