Detection ability of corneal biomechanical parameters for early diagnosis of ectasia.

PURPOSE: To assess the detection ability of corneal biomechanical parameters for early diagnosis of ectasia. METHODS: This retrospective descriptive-analytical study included 134 normal eyes (control group) from 134 healthy subjects and 128 eyes with asymmetric contralateral corneal ectasia with normal topography (ACE-NT, study group) from 128 subjects with definite keratoconus in the opposite eye. Placido-disk-based corneal topography with TMS-4, Scheimpflug corneal tomography with Pentacam HR, and corneal biomechanical assessment with Corvis ST and ocular response analyzer (ORA) were performed. A general linear model was used to compare Corvis ST and ORA biomechanical parameters between groups, while central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered covariates. Receiving operator sensitivity curve (ROC) analysis was used to determine the cut-off point with the highest sensitivity and specificity along with the area under the curve (AUC) for each parameter. RESULT: All parameters of Corvis ST and ORA showed a statistically significant difference between the two groups except for the first (P = 0.865) and second (P = 0.226) applanation lengths, and deformation amplitude (P = 0.936). The discriminative analysis of corneal biomechanical showed that the highest accuracy for the classic, new, and combined parameters of Corvis ST was related to HCR (AUC: 0.766), IR & DAR (0.846), and TBI (0.966), respectively. Using ORA, the corneal resistance factor (0.866) had a higher detection ability than corneal hysteresis (0.826). CONCLUSIONS: TBI has the best accuracy and the highest effect size for differential diagnosis of normal from ACE-NT eyes with a cut-off point of 0.24.

Randomized contralateral comparison of visual outcomes following implantation of two monofocal aspherical intraocular lenses after cataract surgery.

PURPOSE: To compare optical and visual performances of two one-piece aspherical implanted intraocular lenses (IOLs) following phacoemulsification cataract surgery in a contralateral eye study. METHODS: In this prospective randomized parallel-group study, 25 patients with bilateral age-related cataract were implanted in one eye with the EnVista IOL (MX60, Bausch & Lomb Corporations, Rochester, NY, USA) and the Acrysof IQ IOL (Acrysof IQ SN60WF, Alcon Surgical Laboratories, Fort Worth, TX, USA) in the other eye. Uncorrected and corrected distance visual acuity (UDVA, CDVA), refractive status, higher-orders aberrations (HOAs) in 5 and 6 mm pupil size, contrast sensitivity (CS) with and without glare, color vision status, and patient satisfaction were assessed in the two eyes at 1 and 3 months after surgery. RESULTS: There was no significant difference in CDVA (P > 0.99), UDVA (P = 0.46), spherical equivalent refractive error (P = 0.63), CS with and without glare across different spatial frequencies, color vision, and root mean square (RMS) of aberrometric values between the two IOLs after 3-month follow-up. Spherical aberration with 5 and 6 mm pupil sizes (P = 0.02) and horizontal coma with a 6 mm pupil size (P < 0.001) were lower with the EnVista IOL. Patient's satisfaction showed no cases of dissatisfaction, and most patients were highly or moderately satisfied with both IOLs. CONCLUSION: The visual and optical performance of eyes implanted with the EnVista IOL or the Acrysof IQ IOL was similar, although the aberration profile differed.

Long-term Outcomes of Collagen Crosslinking for Early Keratoconus.

PURPOSE: To evaluate the long-term outcomes of collagen crosslinking in early keratoconus. METHODS: Thirty eyes of twenty patients with early keratoconus were enrolled. Uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), objective refraction, subjective refraction, corneal topography and pachymetry were assessed before and 3, 6, 12 months and 9 years after performing collagen crosslinking surgery. RESULTS: The patients' mean age was 31.2 ± 5.59 years at nine-year follow-up (range, 25-44 years). The means of preoperative UCVA and BSCVA were 0.57 ± 0.34 and 0.15 ± 0.12 logMAR, respectively, and these values remained stable at the final follow-up (P = 0.990 and P = 0.227, respectively). The mean objective spherical equivalent decreased considerably from -6.00 ± 4.05 D preoperatively to -5.22 ± 3.71 D at the final follow-up (P < 0.05). The mean subjective spherical equivalent was -4.25 ± 2.87 D preoperatively and this value was stable at the last follow-up (P = 0.92). No considerable difference was found between the post- and preoperative mean objective cylinder values (P = 0.34). The mean subjective cylinder value changed significantly from -4.05 ± 1.85 D preoperatively to -3.1 ± 1.42 D at the final follow-up (P < 0.05). The mean central corneal thickness was 496.97 ± 45.95 µm preoperatively and this value was stable at nine-year follow-up (P = 0.183). No significant difference was found between the pre- and postoperative mean maximum and mean minimum corneal curvature values (P = 0.429 and P = 0.248, respectively). There were no significant postoperative complications. CONCLUSION: Corneal crosslinking in early keratoconus seems to be a safe procedure that can effectively stabilize UCVA, BSCVA, subjective SE and CCT, while improving objective spherical equivalent.

Prevalence of Refractive Errors in Iranian University Students in Kazerun.

PURPOSE: To determine the prevalence of refractive errors and visual impairment and the correlation between personal characteristics, including age, sex, weight, and height, with different types of refractive errors in a population of university students in the south of Iran. METHODS: In this cross-sectional study, a number of university majors were selected as clusters using multi-stage sampling in all universities located in Kazerun (27 clusters of 133 clusters). Then, proportional to size, a number of students in each major were randomly selected to participate in the study. Uncorrected and corrected visual acuity, non-cycloplegic objective refraction and subjective refraction were measured in all participants. RESULTS: The prevalence and 95% confidence interval (CI) of presenting visual impairment and blindness was 2.19% (1.48-3.23) and 0.27% (0.12-0.62), respectively. Refractive errors comprised 75% of the causes of visual impairment. The prevalence (95% CI) of myopia [spherical equivalent (SE) ≤ -0.5 D], hyperopia (SE ≥ 0.5 D), and astigmatism (cylinder power < -0.5 D) was 42.71% (39.71-45.77), 3.75% (2.85-4.51), and 29.46% (27.50-31.50), respectively. Totally, 49.03% (46.39-51.68) of the participants had at least one type of refractive error. There was a positive association between weight and myopia (1.01; 95% CI: 1.01-1.02), anisometropia (1.03; 95% CI: 1.01-1.06), and refractive errors (1.01; 95% CI: 1.01-1.02). In comparison with the age group 18-19 years, the odds ratio (OR) of astigmatism in the age group 26-27 years was 1.64 (95% CI: 1.03-2.61), and the OR of anisometropia in the age group ≥ 30 years was 0.21 (95% CI: 0.04-0.98). CONCLUSIONS: The prevalence of refractive errors, especially myopia, is higher in university students than the general population. Since refractive errors constitute a major part of visual impairment, university students should receive special services for providing corrective lenses and glasses to reduce the burden of these disorders.

Scheimpflug Corneal Densitometry Changes After the Intrastromal Corneal Ring Segment Implantation.

PURPOSE: To investigate the changes in corneal backward scattering using Scheimpflug tomography (densitometry) 6 months after intrastromal corneal ring segments (Keraring) implant for keratoconus and to correlate with clinical results. METHODS: Along with standard ophthalmic examination, Scheimpflug tomography using Pentacam HR was performed to document corneal densitometry and corneal shape. A densitometry map was displayed using grayscale units (GSUs) ranging from 0 to 100 (minimum to maximum light scattering) in 4 concentric annuluses: central 2-, 2- to 6-, 6- to 10-, 10- to 12-, and total 12-mm corneal diameter and at 3 different depths: anterior 120 µm, posterior 60 µm, middle (varying accordingly to the total thickness), and total thickness. RESULTS: The changes in mean corneal densitometry values for anterior, central, and posterior layers were 3.82 ± 3.13, 2.70 ± 1.78, and 1.68 ± 1.52 GSU, respectively, and for annuluses of 0 to 2, 2 to 6, 6 to 10, and 10 to 12 mm were 2.96 ± 2.60, 4.53 ± 2.28, 2.09 ± 1.74, and 0.45 ± 3.93 GSU, respectively. The mean values increased for all corneal layers (P < 0.05), except in the peripheral 10- to 12-mm annulus (P> 0.05). The highest increase was in the annulus 2 to 6 mm of the anterior layer (5.72 ± 3.70 GSU). Changes in the mean densitometry showed a significant correlation with the mean of average keratometry changes only for the front corneal surface and changes in the Q-values for both corneal surfaces in the 2- to 6-mm annulus for all layers. CONCLUSIONS: Significant increase in the corneal densitometry mainly in the anterior 2- to 6-mm annulus of the cornea is associated with the position of the ring segment implant. More studies are needed to elucidate the relevance of such findings.

The prevalence of color vision deficiency in the northeast of Iran.

PURPOSE: To determine the prevalence of color vision deficiency (CVD) in the northeast of Iran. METHODS: This cross-sectional, population-based study was conducted in Mashhad, in the northeast of Iran. Multistage cluster sampling was used for selecting the participants. After preliminary screening, the subjects underwent a complete ophthalmic examination. The examination included the measurement of visual acuity, refraction, and slit-lamp biomicroscopy. The Farnsworth D-15 test was used to detect CVD. The color vision test was done with the best optical correction. RESULTS: Of the 4453 invitees, 3132 participated in the study (response rate: 70.4%). The overall prevalence of CVD in this study was 13.93% [95% confidence interval (CI): 12.44-15.41]. The prevalence of CVD in males and females was 15.85% (95% CI: 13.26-18.44) and 12.96% (95% CI: 11.22-14.71), respectively. The most prevalent types of CVD were tritanopia (6.96%; 95% CI: 5.84-8.08), deuteranopia (3.92%; 95% CI: 3.14-4.70) and tritanomalous (2.21%; 95% CI: 1.55-2.86), respectively. According to the results of logistic regression, the odds of having protanopia were higher in females than males [Odds ratio (OR) = 4.80; 95% CI: 1.20-19.18]. The odds of having deuteranopia were lower in females than males (OR = 0.52; 95% CI: 0.35-0.76). The odds of having CVD were lower in 16-30 (OR = 0.52; 95% CI: 0.37-0.73) and higher in 46-60 (OR: 1.41; 95% CI: 1.01-1.97) year age groups compared to 7-15 year age group. The odds of having tritanopia in 16-30 and 46-60 year age groups was 0.56 (95% CI: 0.35-0.90) and 1.79 (95% CI: 1.19-2.67) compared to 7-15 year age groups, respectively. CONCLUSION: The prevalence of CVD was high in this study, especially in males and people over 46 years of age. Planning for involvement of ocular disease control programs in health care systems can be helpful in the reduction of CVD and improving the quality of life in affected patients.

Pattern visual evoked potential in hypothyroid patients.

PURPOSE: To investigate the functional integrity of visual pathway in hypothyroid patients by pattern visual evoked potential (PVEP). METHODS: We enrolled 36 female patients with history of hypothyroidism (18 overt and 18 subclinical) aged 20 to 60 years and 36 healthy women of similar age (control group). All subjects had a complete ophthalmic examination. For VEP testing, subjects were exposed to checks subtending a visual angle of 15 and 60 min of arc. RESULTS: For the 15 min of arc check size, the mean P100 latency was significantly delayed (113 milliseconds (ms)) and amplitude significantly reduced (9.2 microvolts (µv)) in the hypothyroidism group compared with controls (109.6 ms and 11.6 µv, respectively). For this 15' check size, the group differences were related to significantly increased latency and reduced amplitude of responses in the group with overt hypothyroidism compared with controls. There was no difference between the groups (hypothyroid vs control) with 60 min of arc check size. There was a significant correlation between severity of the disease and PVEP component. CONCLUSIONS: In conclusion, low levels of circulating hypothyroid hormone are associated with delay in the pattern VEP to small check sizes. This CNS involvement worsens in patients with greater severity and duration of hypothyroidism.

Contrast Sensitivity Abnormalities in Deaf Individuals.

PURPOSE: Hearing impaired children are heavily dependent on their sense of vision to develop efficient communication skills; any contrast sensitivity defect can negatively impact their lives because they are not able to use auditory stimuli to recognize probable dangers in the world around them. The purpose of this study was to determine the contrast sensitivity abnormalities in deaf individuals. METHODS: In this cross-sectional study, contrast sensitivity of 15- to 20-year-old high-school boys with hearing disability from Tehran, Iran were evaluated. Sixty-four eyes were tested for contrast sensitivity and refractive error. All subjects had an intelligence quotient (IQ) >70. We investigated their contrast sensitivity with Vector vision CVS-1000 in 4 different spatial frequencies. RESULTS: Profound hearing loss was noted in 50% of the subjects. The frequency of contrast sensitivity abnormalities in 4 different spatial frequencies varied between 51.6% and 65.6%. The largest abnormalities were recorded at 18 cycles per degree. Only 12.5% of deaf students had corrected distance visual acuity (CDVA) greater than zero (in LogMAR). The abnormalities in contrast sensitivity showed no correlation with the type or severity of hearing loss. CONCLUSION: Hearing impaired boys are at a greater risk for contrast sensitivity abnormalities than boys with normal hearing. The larger frequency of contrast sensitivity abnormalities in high spatial frequencies than in other frequencies may demonstrate greater defects in the central visual system compared with the periphery in individuals with hearing loss.

Investigation of the effects of Islamic fasting on ocular parameters.

PURPOSE: To investigate the effects of religious fasting during the month of Ramadan on intraocular pressure (IOP), refractive error, corneal tomography and biomechanics, ocular biometry, and tear film layer properties. METHODS: This prospective study was carried out one week before and in the last week of Ramadan. Ninety-four eyes of 94 healthy adult volunteers (54 males and 40 females) with a mean ± SD age of 35.12 ± 9.07 were enrolled in this study. Patients with any systemic disorder, ocular disease, or a history of previous surgery were excluded. Corneal tomography and biomechanics, ocular biometry, IOP, refractive error, and tear break up time (TBUT) were evaluated in non-fasting and fasting periods by the Pentacam (Oculus), Corvis ST (Oculus), IOL Master (Carl Zeiss), computerized tonometer (Topcon CT-1/CT-1P), auto kerato-refractometer (Topcon KR-1), and Keratograph 5M (Oculus), respectively. RESULTS: There was no significant difference in the central corneal thickness (CCT) between the study groups (P = 0.123) using the Pentacam while the Corvis ST showed a significant difference in all participants (P < 0.0001). Moreover, the peak distance (distance of the two surrounding peaks of the cornea at the highest concavity) of male and female participants showed a significant difference between the fasting and non-fasting groups (P = 0.002). The anterior chamber depth (ACD) using the Pentacam decreased in the male group (P = 0.004) in the fasting period. During the fasting period, computerized tonometer showed a decrease in IOP only in males in comparison to the non-fasting group (P = 0.018) while the Corvis ST showed decreased IOP in all participants (P < 0.0001). The steep keratometry (K2) in the corneal posterior surface appeared to be different in males between the study groups (P = 0.034). We were unable to show any significant difference in other ocular parameters between fasting and non-fasting periods. CONCLUSION: This study showed that ACD, IOP, CCT, and peak distance were different between fasting and non-fasting groups while no difference was observed in other ocular parameters. Interpretations of these significant differences should be considered in the clinical setting.

Binocular and Accommodative Characteristics in a Normal Population.

PURPOSE: To study binocular and accommodative characteristics and their associations with age and gender in an Iranian young adult population. METHODS: In this cross-sectional study, multistage cluster sampling was done from the students of Mashhad University of Medical Sciences. All participants had visual acuity, refraction, and cover tests followed by measurements of the near point of convergence (NPC), amplitude of accommodation (AA), monocular and binocular accommodative facility (MAF and BAF) using ±2.00 diopter (D) flipper lenses, and negative and positive relative accommodation (NRA and PRA). Near and distance fusional vergence reserves were measured using prism bar, and near associated phoria was assessed using the Mallett unit. RESULTS: The mean age of the participants was 22.5±4.4 years (range: 18-35 years). The binocular and accommodative characteristics and their means in the studied sample included: mean distance dissociated phoria: 1.15 exophoria±2.04 prism diopters (PD), near dissociated phoria: 5.02 exophoria±4.74 PD, near associated phoria: 0.55 base-in±1.02, gradient accommodative convergence/accommodation (AC/A) ratio: 4.66±1.59, NPC: 5.27±3.60 cm, MAF: 11.33±5.58 cpm, BAF: 8.84±4.47 cpm, NRA: 2.08±0.33 D, PRA:-2.92±0.76 D, and AA: 11.14±2.6 D. In the multiple regression model including age and gender, near exophoria was significantly higher in men and levels of near base-out-break and near base-out-recovery were higher in females. Distance exophoria, distance base-in-break, distance base-in-recovery, and NPC increased with age and near base-out-break, PRA, BAF, MAF, and AA significantly decreased with age. CONCLUSION: Studied indices in this study significantly differ from available guidelines and these differences must be considered when making diagnostic or therapeutic decisions. Certain indices can be affected by age and gender.

The Relationship of Body Mass Index and Blood Pressure with Corneal Biomechanical Parameters in Healthy Subjects.

This study aimed to assess the possible relationship of body mass index (BMI) and blood pressure (BP) with corneal biomechanical parameters in healthy subjects. The study included 88 eyes of 88 healthy subjects aged 20-40 years. After a thorough medical history, a digital sphygmomanometer was used to measure the systolic blood pressure (SBP) and diastolic blood pressure (DBP). In addition, several hematological and biochemical parameters were determined to assess general health. Prior the ophthalmic examination, the body height and weight were measured; then, the BMI was calculated. Finally, after comprehensive ophthalmic examination, all cases were evaluated with Pentacam (Oculus) in order to rule out corneal ectasia; then, the corneal biomechanical parameters of all individuals were measured using the Scheimpflug-based Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany). If the measurements of the hematological and biochemical parameters were within normal range, the results of the Corvis ST, BMI, and BP were included in the analysis carried out with SPSS software. The mean (± standard deviation [SD]) BMI, SBP, DBP, intraocular pressure (IOP), central corneal thickness (CCT), deformation amplitude, radius, and peak distance was 27.24 ± 4.80 kg/m2, 116.47 ± 11.21 mmHg, 80.51 ± 5.68 mmHg, 15.10 ± 1.70 mmHg, 533.10 ± 30.97 micrometer, 1.03 ± 0.11 mm, 7.51 ± 0.86 mm, and 5.03 ± 0.30 mm, respectively. Results showed no significant difference in IOP, CCT, peak distance, radius, and deformation amplitude between different BMI subcategories defined by World Health Organization (all P > 0.05). The results of the Corvis ST showed that corneal biomechanical parameters had no significant correlation with BMI, SBP, and DBP in three subgroups of BMI and all participants (all P > 0.05) but the results showed a positive correlation between CCT and IOP (P < 0.001, r = 0.504) in all participants. CCT and IOP had no correlation with BMI, SBP, and DBP (P > 0.05). This study showed that BMI and BP had no correlation with corneal biomechanical parameters in healthy subjects using the Corvis ST.

Visual Field Abnormalities among Adolescent Boys with Hearing Impairments.

The aim of this study was to compare the visual field (VF) categorizations (based on the severity of VF defects) between adolescent boys with hearing impairments and those with normal hearing. This cross-sectional study involved the evaluation of the VF of 64 adolescent boys with hearing impairments and 68 age-matched boys with normal hearing at high schools in Tehran, Iran, in 2013. All subjects had an intelligence quotient (IQ) > 70. The hearing impairments were classified based on severity and time of onset. Participants underwent a complete eye examination, and the VFs were investigated using automated perimetry with a Humphrey Visual Field Analyzer. This device was used to determine their foveal threshold (FT), mean deviation (MD), and Glaucoma Hemifield Test (GHT) results. Most (50%) of the boys with hearing impairments had profound hearing impairments. There was no significant between-group difference in age (P = 0.49) or IQ (P = 0.13). There was no between-group difference in the corrected distance visual acuity (P = 0.183). According to the FT, MD, and GHT results, the percentage of boys with abnormal VFs in the hearing impairment group was significantly greater than that in the normal hearing group: 40.6% vs. 22.1%, 59.4% vs. 19.1%, and 31.2% vs. 8.8%, respectively (P < 0.0001). The mean MD in the hearing impairment group was significantly worse than that in the normal hearing group (-0.79 ± 2.04 and -4.61 ± 6.52 dB, respectively, P < 0.0001), and the mean FT was also significantly worse (38.97 ± 1.66 vs. 35.30 ± 1.43 dB, respectively, P <0.0001). Moreover, there was a significant between-group difference in the GHT results (P < 0.0001). Thus, there were higher percentages of boys with VF abnormalities and higher mean MD, FT, and GHT results among those with hearing impairments compared to those with normal hearing. These findings emphasize the need for detailed VF assessments for patients with hearing impairments.

Refractive Outcomes, Contrast Sensitivity, HOAs, and Patient Satisfaction in Moderate Myopia: Wavefront-Optimized Versus Tissue-Saving PRK.

PURPOSE: To compare refractive outcomes, contrast sensitivity, higher-order aberrations (HOAs), and patient satisfaction after photorefractive keratectomy for correction of moderate myopia with two methods: tissue saving versus wavefront optimized. METHODS: In this prospective, comparative study, 152 eyes (80 patients) with moderate myopia with and without astigmatism were randomly divided into two groups: the tissue-saving group (Technolas 217z Zyoptix laser; Bausch & Lomb, Rochester, NY) (76 eyes of 39 patients) or the wavefront-optimized group (WaveLight Allegretto Wave Eye-Q laser; Alcon Laboratories, Inc., Fort Worth, TX) (76 eyes of 41 patients). Preoperative and 3-month postoperative refractive outcomes, contrast sensitivity, HOAs, and patient satisfaction were compared between the two groups. RESULTS: The mean spherical equivalent was -4.50 ± 1.02 diopters. No statistically significant differences were detected between the groups in terms of uncorrected and corrected distance visual acuity and spherical equivalent preoperatively and 3 months postoperatively. No statistically significant differences were seen in the amount of preoperative to postoperative contrast sensitivity changes between the two groups in photopic and mesopic conditions. HOAs and Q factor increased in both groups postoperatively (P = .001), with the tissue-saving method causing more increases in HOAs (P = .007) and Q factor (P = .039). Patient satisfaction was comparable between both groups. CONCLUSIONS: Both platforms were effective in correcting moderate myopia with or without astigmatism. No difference in refractive outcome, contrast sensitivity changes, and patient satisfaction between the groups was observed. Postoperatively, the tissue-saving method caused a higher increase in HOAs and Q factor compared to the wavefront-optimized method, which could be due to larger optical zone sizes in the tissue-saving group.

Comparison of visual status of Iranian military and commercial drivers.

BACKGROUND: There is no legal requirement for Iranian military truck drivers to undergo regular visual checkups as compared to commercial truck drivers. OBJECTIVES: This study aimed to evaluate the impact of drivers' visual checkups by comparing the visual function of Iranian military and commercial truck drivers. PATIENTS AND METHODS: In this comparative cross-sectional study, two hundred military and 200 commercial truck drivers were recruited and their Visual Acuity (VA), Visual Field (VF), color vision and Contrast Sensitivity (CS) were assessed and compared using the Snellen chart, confrontation screening method, D15 test and Pelli-Robson letter chart, respectively. A questionnaire regarding driving exposure and history of motor-vehicle crashes (MVCs) was also filled by drivers. Results were analyzed using an independent samples t-test, one-way ANOVA (assessing difference in number of MVCs across different age groups), chi-square test and Pearson correlation at statistical significance level of P < 0.05. RESULTS: Mean age was 41.6 ± 9.2 for the military truck drivers and 43.4 ± 10.9 for commercial truck drivers (P > 0.05). No significant difference between military and commercial drivers was found in terms of driving experience, number of MVCs, binocular VA, frequency of color vision defects and CS scores. In contrast, the last ocular examination was significantly earlier in military drivers than commercial drivers (P < 0.001). In addition, 4% of military drivers did not meet the national standards to drive as opposed to 2% of commercial drivers. There was a significant but weak correlation between binocular VA and age (r = 0.175, P < 0.001). However, CS showed a significantly moderate correlation with age (r = -0.488, P < 0.001). CONCLUSIONS: The absence of legal requirement for regular eye examination in military drivers caused the incompetent drivers to be missed in contrast to commercial drivers. The need for scientific revision of VA standard for Iranian drivers is also discussed. The CS measurement in visual checkups of older drivers deserves to be investigated more thoroughly.

Frequency of convergence and accommodative disorders in a clinical population of Mashhad, Iran.

PURPOSE: To investigate the frequency of convergence and accommodation anomalies in an optometric clinical setting in Mashhad, Iran, and to determine tests with highest accuracy in diagnosing these anomalies. METHODS: From 261 patients who came to the optometric clinics of Mashhad University of Medical Sciences during a month, 83 of them were included in the study based on the inclusion criteria. Near point of convergence (NPC), near and distance heterophoria, monocular and binocular accommodative facility (MAF and BAF, respectively), lag of accommodation, positive and negative fusional vergences (PFV and NFV, respectively), AC/A ratio, relative accommodation, and amplitude of accommodation (AA) were measured to diagnose the convergence and accommodation anomalies. The results were also compared between symptomatic and asymptomatic patients. The accuracy of these tests was explored using sensitivity (S), specificity (Sp), and positive and negative likelihood ratios (LR+, LR-). RESULTS: Mean age of the patients was 21.3 ± 3.5 years and 14.5% of them had specific binocular and accommodative symptoms. Convergence and accommodative anomalies were found in 19.3% of the patients; accommodative excess (4.8%) and convergence insufficiency (3.6%) were the most common accommodative and convergence disorders, respectively. Symptomatic patients showed lower values for BAF (p = .003), MAF (p = .001), as well as AA (p = .001) compared with asymptomatic patients. Moreover, BAF (S = 75%, Sp = 62%) and MAF (S = 62%, Sp = 89%) were the most accurate tests for detecting accommodative and convergence disorders in terms of both sensitivity and specificity. CONCLUSIONS: Convergence and accommodative anomalies are the most common binocular disorders in optometric patients. Including tests of monocular and binocular accommodative facility in routine eye examinations as accurate tests to diagnose these anomalies requires further investigation.

Eye problems in children with hearing impairment.

PURPOSE: To compare the prevalence of refractive errors, amblyopia, and strabismus between hearing-impaired and normal children (7-22 years old) in Mashhad. METHODS: In this cross-sectional study, cases were selected from hearing-impaired children in Mashhad. The control group consisted of children with no hearing problem. The sampling was done utilizing the cluster sampling method. All of the samples underwent refraction, cover test, and visual examinations. RESULTS: 254 children in the hearing-impaired group (case) and 506 children in the control group were assessed. The mean spherical equivalent was 1.7 ± 1.9 D in the case group, which was significantly different from the control group (0.2 ± 1.5) (P < 0.001). The prevalence of hyperopia was 57.15% and 21.5% in deaf and normal children, respectively, but myopia was mostly seen in the control group (5.5% versus 11.9%, P = 0.007). The mean cylinder was 0.65 ± 1.3 D and 0.43 ± 0.62 D in deaf and normal subjects, respectively (P = 0.002). 12.2% of deaf subjects and 1.2% of normal subjects were amblyopic (P < 0.001), and the prevalence of strabismus was 3.1% in the case group and 2.6% in the control group (P = 0.645). CONCLUSION: In a comparison of children of the same ages, hearing-impaired children have significantly more eye problems; therefore, a possible relation between deafness and eye problems must exist. Paying attention to eye health assessment in hearing-impaired children may help prevent adding eye problems to hearing difficulties.

Pattern Visual Evoked Potentials in Dyslexic versus Normal Children.

PURPOSE: Presence of neurophysiological abnormalities in dyslexia has been a conflicting issue. This study was performed to evaluate the role of sensory visual deficits in the pathogenesis of dyslexia. METHODS: Pattern visual evoked potentials (PVEP) were recorded in 72 children including 36 children with dyslexia and 36 children without dyslexia (controls) who were matched for age, sex and intelligence. Two check sizes of 15 and 60 min of arc were used with temporal frequencies of 1.5 Hz for transient and 6 Hz for steady-state methods. RESULTS: Mean latency and amplitude values for 15 min arc and 60 min arc check sizes using steady state and transient methods showed no significant difference between the two study groups (P values: 0.139/0.481/0.356/0.062). Furthermore, no significant difference was observed between two methods of PVEPs in dyslexic and normal children using 60 min arc with high contrast (P values: 0.116, 0.402, 0.343 and 0.106). CONCLUSION: The sensitivity of PVEP has high validity to detect visual deficits in children with dyslexic problem. However, no significant difference was found between dyslexia and normal children using high contrast stimuli.

Normal range of cambridge low contrast test; a population based study.

PURPOSE: To determine the range of contrast sensitivity (CS) and its determinants in a normal population, Mashhad, Iran. METHODS: In this cross-sectional population based study, 4,453 individuals were invited of whom 3,132 persons agreed to participate (response rate, 70.4%). CS data from 2,449 eligible individuals were analyzed. CS was determined using the Cambridge low contrast square-wave grating test, and its associations with age, gender, best-corrected visual acuity (BCVA) and manifest refraction spherical equivalent (MRSE) refractive error, were analyzed. RESULTS: Mean age of the participants was 29.1±17.3 (range, 4-89) years and 66.4% were female. Mean CS was 239.6±233.3 and 234.6±228.6 cps in right and left eyes, respectively. Mean binocular CS was 310.9±249.0 cps. Multiple linear regression showed that CS was inversely correlated with older age (ß=-1.1, P<0.001), female gender (ß=-40.1, P<0.001), poorer BCVA (ß=-165.4, P<0.001), and severity of myopia (ß=-10.2, P<0.001). CONCLUSION: The normal range of Cambridge low-contrast grating test reported herein may serve as a reference for the general population in Iran. Our findings can be used for both research and clinical applications, particularly for evaluations of the outcomes of refractive surgery. In the current study, CS was lower in older subjects, myopic individuals and patients with lower BCVA.

Prevalence of Refractive Errors in Students with and without Color Vision Deficiency.

PURPOSE: To evaluate refractive errors in school age children with color vision deficiency (CVD) and those with normal color vision (NCV) in order to make a better understanding of the emmetropization process. METHODS: A total of 4,400 primary school students aged 7-12 years were screened for color vision using Ishihara pseudoisochromatic color vision plate sets. Of these, 160 (3.6%) students had CVD. A total of 400 age- and sex-matched students with NCV were selected as controls. Refractive status was evaluated using objective cyclorefraction. RESULTS: The CVD group included 136 male (85%) and 24 female (15%) subjects with mean age of 10.1 ± 1.8 years. The NCV group comprised of 336 male (84%) and 64 female (16%) subjects with mean age of 10.5 ± 1.2 years. The prevalence of myopia (7.7% vs. 13.9%, P < 0.001) and hyperopia (41% vs. 57.4%, P = 0.03) was significantly lower in the CVD group. Furthermore, subjects with CVD subjects demonstrated a lower magnitude of refractive errors as compared to the CVD group (mean refractive error: +0.54 ± 0.19 D versus + 0.74 ± 1.12 D, P < 0.001). CONCLUSION: Although the lower prevalence of myopia in subjects with CVD group supports the role of longitudinal chromatic aberration in the development of refractive errors; the lower prevalence of hyperopia in this group is an opposing finding. Myopia is a multifactorial disorder and longitudinal chromatic aberration is not the only factor influencing the emmetropization process.

The prevalence of anisometropia in population base study.

PURPOSE: To determine the prevalence of anisometropia and its determinants in the population of Mashhad. METHODS: In a cross-sectional study in 2008, 4453 residents of Mashhad city between the ages of 1 and 90 years were selected using stratified cluster sampling, of which 70.4% participated in the study. All respondents had visual acuity and refraction testing. Anisometropia was defined as the absolute interocular difference in the spherical equivalent based on non-cycloplegic refraction. The prevalence rates and 95% confidence intervals (CI) of anisometropia were determined based on cut points of 0.5 diopter (D), 1.0 D, and 2.0 D or more, and we used the 1.0 D cut point to examine associations. RESULTS: After applying exclusion criteria, data from 2947 participants were used in the analyses. Based on cut points of 0.5 D, 1.0 D, and 2.0 D or more, the prevalence of anisometropia was 17.0% (n = 451) (95% CI, 15.1-18.8), 5.6% (n = 148) (95% CI, 4.6-6.6), and 1.7% (n = 50) (95% CI, 1.2-2.2), respectively. The odds of anisometropia showed a significant increase of 2.8% with every year of aging (P < 0.001); 2.6% and 2.8% were anisomyopic and anisohyperopic, respectively. The prevalence of anisometropia was directly associated with myopia (P < 0.001) as well as a history of ocular trauma (P < 0.001). The prevalence of anisoastigmatism was 5.6% and significantly increased with age (P < 0.001). CONCLUSION: The prevalence of anisometropia in the studied population, compared to studies conducted in the Middle Eastern Region and East Asia, is in the midrange. The prevalence of anisometropia is higher at older age, however, children should receive more attention due to the risk of amblyopia. A history of ocular trauma is a risk factor for anisometropia.