Anisometropia Profile in Elderly Population: Tehran Geriatric Eye Study.

PURPOSE: To investigate the distribution and prevalence of anisometropia according to age, gender and ocular biometry in a geriatric population in Tehran, Iran. METHODS: The present study was conducted on the geriatric population aged above 60 years. The study participants were selected using stratified random cluster sampling. The uncorrected and best-corrected visual acuity, dry objective (ARK510A, Nidek Co. 42 LTD, Aichi, Japan) and subjective refraction and ocular biometry (IOL Master 500; Carl Zeiss Meditec, Jena, Germany) were recorded for each patient. The magnitude and prevalence of anisometropia were evaluated in association with influential factors in cut-points of 0.50, 1.00, 1.50 and 2.00 diopter (D). RESULTS: The mean age of participants (3237 individuals, 54% were female) was 68.19 ± 6.48 (range: 60-97) years. The mean anisometropia in the whole sample was 0.82 D (95% CI: 0.76 - 0.88 D), which increased from 0.62 D (in those aged 60-64 years old) to 1.36 D (in those above 80 years). The prevalence of anisometropia >1 D in total population, males, and females were 23.81%, 24.9%, and 22.76%, respectively. The odds ratio of anisometropia was higher in cases with cataracts, myopia compared to emmetropia, keratometry asymmetry, axial length asymmetry (P = .001), and corneal diameter asymmetry (all others, P < .001). CONCLUSION: The results of the present study show a high prevalence of anisometropia in elderly population, which was related to refractive error, cataract, age, gender, and ocular biometry asymmetry.

Binocular vision disorders in a geriatric population.

CLINICAL RELEVANCE: A population-based epidemiological survey is important to help establish the frequency of binocular vision disorders in a geriatric population. Such data will be useful to clinicians and help guide diagnostic testing for this age group. BACKGROUND: To determine the prevalence of binocular vision disorders and their associations with age and sex in the geriatric population. METHODS: This report is a part of the Tehran Geriatric Eye study (TGES); a population-based cross-sectional study conducted on residents over 60 years of age in Tehran, Iran, using random stratified cluster sampling. A total of 165 clusters were selected (proportionally to size) from 22 strata of Tehran city. All participants underwent a complete ocular examination including the measurement of visual acuity, refraction, unilateral and alternating cover tests, and the Worth 4-dot suppression test. Strabismus was defined as the presence of constant unilateral or alternating esotropia or exotropia at either near (40 cm) or far (6 m). Distance and near exophoria were defined as more than 3Δ and 9Δ of exophoria at 6 m and 40 cm, respectively. Distance and near esophoria were defined as more than 1Δ and any amount of esophoria at 6 m and 40 cm, respectively. RESULTS: Statistical analysis was performed on the data of 2,227 participants. The mean age of the participants was 66.6 ± 5.4 years and 59.4% were female. The prevalence of distance exophoria, esophoria, and hyperphoria was 8.9%, 0.34%, and 0.29%, respectively. The prevalence of near exophoria, esophoria, and hyperphoria was 32.4%, 0.61%, and 0.37%, respectively. The prevalence of distance exotropia and esotropia was 1.3% and 0.63%, respectively. The prevalence of near exotropia and esotropia was 4.6% and 0.59%, respectively. CONCLUSION: Non-strabismic binocular vision disorders were prevalent in an elderly population. Exo deviations were more prevalent than eso deviations.

Is retinal nerve fibre layer thickness correlated with visual function in individuals having optic neuritis?

CLINICAL RELEVANCE: The existence of a correlation between the results of paraclinical retinal imaging and clinical tests such as contrast sensitivity can reduce time and cost in diagnosing optic neuritis (ON). BACKGROUND: To demonstrate whether changes of peripapillary retinal nerve fibre layer (RNFL) thickness are correlated with the results of visual acuity, contrast sensitivity and colour vision in eyes with acute ON. METHODS: Thirty patients with acute ON, 23 females and seven males, who had no previous history of ON in neither eye, were examined. Inclusion criteria were: subjects had spherical refraction of less than ±5D, no prior ON or optic disc swelling, no history of amblyopia or colour blindness, and no history or ophthalmoscopic evidence of glaucoma, diabetic retinopathy, or maculopathies. Visual acuity, contrast sensitivity and colour vision were tested and optical coherence tomography was performed for all patients after complete ophthalmologic examinations including refraction, biomicroscopy, and funduscopy with a 90D lens by a neuro-ophthalmologist. RESULTS: Thirty patients who were 18-45 years old entered the study. There was an inverse correlation between contrast sensitivity and nasal (r = -0.430, p = 0.018), inferior (r = -0.503, p = 0.005) and mean (r = -0.510, p = 0.004) RNFL thickness. The multiple linear regression model, after adjustment for age and sex, showed a significant association between visual acuity and nasal RNFL thickness (coefficient = 0.025, p = 0.032). There was also a significant inverse correlation between contrast sensitivity and nasal (coefficient = -0.003, p = 0.036), inferior (coefficient = -0.006, p = 0.010) and mean (coefficient = -0.007, p = 0.012) RNFL thickness. No significant correlation was found between colour vision and RNFL thickness. CONCLUSION: Contrast sensitivity is more correlated with changes in RNFL thickness in comparison with visual acuity and colour vision. Contrast sensitivity measurement therefore can be used as one of the first assessments in patients with ON.

Corneal Stability and Visual Acuity 1 Year After Corneal Cross-linking Assessed Using the ABCD Keratoconus Staging System.

PURPOSE: To assess corneal stability and corrected distance visual acuity (CDVA) 3, 6, and 12 months following corneal cross-linking (CXL) using the ABCD keratoconus staging system. METHODS: This prospective longitudinal study included 31 eyes with keratoconus receiving CXL based on the standard Dresden protocol. CDVA, refraction, and Scheimpflug tomography with the Pentacam HR (Oculus Optikgeräte GmbH) were evaluated before and after surgery. Geometric and functional changes were assessed using the actual values and staging of each element of the ABCD keratoconus staging system. A, B, C, and D refer to the anterior and posterior radii of curvature in a 3-mm zone centered on the cor-neal thinnest point, minimum corneal thickness, and CDVA, respectively. RESULTS: There were no significant changes in the actual values of anterior radius of curvature (P = .497) and CDVA (P = .082), whereas posterior radius of curvature (P = .007) and corneal thinnest point (P < .001) showed significant changes statistically. Pairwise comparison showed only a statistically significant steepening in posterior radius of curvature at 3 months after CXL compared to the preoperative radius (P = .002) and a significant decrease in corneal thinnest point at 3 (P < .001) and 6 (P = .028) months after CXL compared to baseline assessment. Staging of each element of the ABCD keratoconus staging system indicated no change between baseline and 3, 6, and 12 months after CXL. CONCLUSIONS: The geometric and functional parameters included in the ABCD keratoconus staging system showed stability of corneal status and CDVA 1 year after CXL. [J Refract Surg. 2021;37(10):700-706.].

Corneal and Ocular Residual Astigmatism in School-Age Children.

PURPOSE: To determine the distribution of residual and corneal astigmatism (CA) in children aged 6-18 years and their relationship with age, sex, spherical equivalent, and biometric parameters. METHODS: In this cross-sectional study, multi-stage stratified cluster sampling was done to select students from Dezful, a city in Southwestern Iran. Examinations included the measurement of visual acuity with and without optical correction, refraction with and without cycloplegia, and biometry using the Biograph (Lenstar, Germany). The main outcomes in this report were corneal and residual astigmatism. The CA was measured by Biograph (difference between k1 and k2), and residual astigmatism was calculated using Alpine method. The power vector method was applied to analyze the data of astigmatism. RESULTS: Of 864 students that were selected, 683 (79.1%) participated in the study. The mean residual and CA were -0.84 diopter (D) and -0.85 D, respectively. According to the results of J0 and J45 vectors, residual astigmatism was -0.33 D and 0.04 D, and CA was 0.38 D and 0.01 D, respectively. With-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism were seen in 3.4%, 66.8%, and 4.5% of the children with residual astigmatism and 67.94%, 1.3%, and 1.5% of the children with CA. Residual astigmatism decreased with an increase in spherical refractive error, whereas CA increased with an increase in spherical refractive error. CONCLUSION: The results of the present study showed a high prevalence and amount of residual astigmatism with ATR pattern among the 6-18-year-old population and the compensatory effect of this type of astigmatism on CA that mostly followed a WTR pattern.

Agreement between Pentacam and handheld Auto-Refractor/Keratometer for keratometry measurement / Concordancia entre el sistema Pentacam y un auto-refractómetro/queratómetro portátil para la medición de queratometría

OBJECTIVE: This study was conducted to evaluate the level of agreement in keratometry measurements between a rotating Scheimpflug imaging-based system (Pentacam) and a handheld auto-refractokeratometer (handheld NIDEK ARK-30). METHOD: This analytical cross-sectional study was conducted in the right eyes of 579 subjects. Keratometry measurements were conducted with the Pentacam and the handheld NIDEK ARK-30 systems. The SPSS Software version 22 and MedCalc V3 were applied to estimate descriptive statistics using paired t-test, Pearson correlation coefficient, 95% limits of agreement (LoA), and Bland-Altman plot. RESULTS: In the total sample, the inter-device difference in the mean flat and steep keratometry values was -0.266 diopter (D) (P-value < 0.001) and 0.052 D (P-value = 0.093), respectively. There was a significant difference in mean flat keratometry between the two devices in all groups of refractive errors (paired difference < 0.5 D and P-value < 0.001). The difference in mean steep keratometry was significant only in myopic subjects (P-value = 0.046). The 95% LoA between the two devices measurements was 2.51 D, 3.98 D, and 6.37 D for flat keratometry and 2.6 D, 3.2 D, and 3.9 D for steep keratometry in emmetropic, myopic, and hyperopic subjects, respectively. CONCLUSION: Our study showed relatively wide limits of agreement between handheld NIDEK ARK-30 and Pentacam; therefore, these devices cannot be used interchangeably for measuring corneal curvature

OBJETIVO: Se realizó este estudio para evaluar el nivel de concordancia de las mediciones queratométricas obtenidas mediante un sistema de cámara rotatoria Scheimpflug (Pentacam) y un auto-refractoqueratómetro portátil (NIDEK ARK-30 portátil). MÉTODO: Este estudio analítico transversal fue realizado en los ojos derechos de 579 sujetos. Las mediciones queratométricas se obtuvieron con Pentacam y NIDEK ARK-30 portátil. Se aplicó el software SPSS versión 22 y MedCalc V3 para calcular las estadísticas descriptivas utilizando la prueba t pareada, el coeficiente de correlación de Pearson, los límites de concordancia (LoA) al 95%, y el análisis gráfico de Bland-Altman. RESULTADOS: En la muestra total, la diferencia inter-dispositivo en cuanto a valores queratométricos planos y curvos medios fue de -0,266 dioptrías (D) (valor P < 0,001) y 0,052 D (valor P = 0,093), respectivamente. Se produjo una diferencia significativa en términos de queratometría plana media entre los dos dispositivos para todos los grupos de errores refractivos (diferencia pareada < 0,5 D y valor P < 0,001). La diferencia en cuanto a queratometría curva media fue significativa únicamente en sujetos miopes (valor P = 0,046). Los LoA al 95% entre las mediciones de los dos dispositivos fue de 2,51 D, 3,98 D, y 6,37 D para la queratometría plana, y de 2,6 D, 3,2 D, y 3,9 D para la curva, en los sujetos con emetropía, miopía e hipermetropía, respectivamente. CONCLUSIÓN: Nuestro estudio reflejó unos límites de concordancia relativamente amplios entre NIDEK ARK-30 portátil y Pentacam; por tanto, estos dispositivos no pueden utilizarse indistintamente para medir la curvatura de la córnea

Long-term Evaluation of Corneal Biomechanical Properties After Corneal Cross-linking for Keratoconus: A 4-Year Longitudinal Study.

PURPOSE: To compare the long-term changes in corneal biomechanics, topography, and tomography before and 4 years after corneal cross-linking (CXL) with the Dresden protocol and correlate these changes with visual acuity. METHODS: In this longitudinal study, 18 eyes of 18 patients with progressive keratoconus who were treated with CXL were included. All patients received a standard ophthalmological examination and were examined by Placido disc-based topography, Scheimpflug tomography, and biomechanical assessments with the Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany) and Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY) before and 4 years after CXL. The main outcome measures were dynamic corneal response (DCR) parameters obtained from the Corvis ST, corneal hysteresis (CH), corneal resistance factor (CRF), visual acuity, refraction, corneal curvature, and corneal thickness. RESULTS: There were no significant differences in mean visual acuity, refraction, intraocular pressure, corneal topography, corneal astigmatism in both corneal surfaces, maximum keratometry, corneal thickness at apical and thinnest points, thickness profile indices, corneal volume, and specular microscopy before and 4 years after CXL (P > .05). Significant changes were observed in many DCR parameters, including radius at highest concavity and integrated inverse radius, both of which were consistent with stiffening. The CH and CRF values after CXL were not statistically significant. The new parameters using the Corvis ST include integrated inverse concave radius, which showed a significant decrease 1.07 ± 0.93 mm-1, consistent with stiffening. The corneal stiffness parameter at the first applanation, Ambrósio's Relational Thickness to the horizontal profile, deformation amplitude ratio, and Corvis Biomechanical Index as a combined biomechanical screening parameter did not show significant changes. CONCLUSIONS: CXL is a minimally invasive treatment option to prevent keratoconus progression over 4 years. Pressure-derived biomechanical parameters obtained from the ORA did not show any change following CXL at 4 years of follow-up, whereas the Corvis ST DCR parameters detected changes in corneal biomechanical properties. [J Refract Surg. 2018;34(12):849-856.].

Comparison of the Visual Acuity and Refractive Error Using OPDIII and Subjective Findings in Visually Normal Subjects.

PURPOSE: To compare the visual acuity and refractive error using OPDIII and subjective findings in visually normal subjects. METHOD: This study was performed on 75 participants (134 eyes) with an age range of 18 to 35 years. Visual acuity was evaluated using both subjective Snellen chart and OPDIII devices. Also, OPDIII objective refraction was compared with subjective refraction. Paired t test was used to compare mean visual acuity and refractive error. The 95% limits of agreement (LOAs) were reported to evaluate the agreement between subjective and objective methods. RESULTS: The mean Snellen visual acuity was 0.705±0.243 logMAR in group with myopia and 0.375±0.207 logMAR in group with hyperopia. Visual acuity obtained using OPDIII was 0.632±0.270 and 0.054±0.084 logMAR in groups with myopia and hyperopia, respectively. There was a significant difference in the mean visual acuity between OPDIII and Snellen chart. The correlation of the Snellen chart with OPDIII was 0.862 and -0.172 in myopic and hyperopic groups, respectively. The 95% LOAs of the OPDIII with Snellen chart were -0.33 to 0.18 and -0.14 to 0.79 logMAR in myopic and hyperopic patients, respectively. The mean spherical power obtained by OPDIII was more negative than that of subjective refraction (OPDIII mean difference -0.272±0.335 and 0.163±0.302 DS in myopic and hyperopic groups respectively), while the cylinder power was less than that of the subjective refraction (OPDIII mean difference 0.488±0.566 and 0.030±0.255 DC in groups with myopia and hyperopia, respectively). The correlation of OPDIII with subjective refraction was 0.905, 0.920 in measurement of the spherical power and 0.908, 0.928 in measurement of the cylinder power in groups with myopia and hyperopia, respectively. CONCLUSION: Visual acuity scores were significantly better using OPDIII compared with Snellen chart in group with myopia, whereas the Snellen chart provided the better visual acuity scores in hyperopic patients. Although the correlation of OPDIII with subjective refraction in measuring the refractive error was high, OPDIII showed a significant difference with subjective refraction.

The normal distribution of corneal eccentricity and its determinants in two rural areas of north and south of Iran.

PURPOSE: The aim of this study was to determine the distribution of corneal eccentricity (E-value) in a normal population and to examine related factors. METHODS: In this cross-sectional study, two villages were selected in Iran using multistage cluster sampling. Selected persons were invited to have a comprehensive eye examination. Examinations in each village were performed at a specific location under standard conditions. After testing for vision and refraction and conducting the slit-lamp exam, E-value was measured with Pentacam. RESULTS: Of the 3851 selected individuals, 3314 participated in the study. After applying the exclusion criteria, data from 2610 subjects was used in the analysis for this report. Mean E-value was 0.53 [95% confidence interval (CI): 0.52 to 0.54]. E-value was not significantly different between males and females. Mean E-value reduced with age from 0.60 in subjects aged 6-20 years to 0.47 in subjects older than 70 years. The hyperopic group of participants had significantly lower E-value than myopic and emmetropic ones (P < 0.001). The relationship of E-value with age, gender, and other anterior segment variables and spherical equivalent was examined in a multiple linear regression model. In multiple linear regression model, age (coef = -0.003), spherical equivalent refraction (coef = -0.005), pupil diameter (coef = 0.018), anterior chamber volume (coef = -0.001), and anterior chamber angle (coef = 0.003) significantly correlated with E-value. CONCLUSIONS: The results of this study showed that the cornea in normal populations is prolate, and the degree of prolateness varies by age, such that older age is associated with a less prolate cornea. This study showed that factors such as age and refractive errors and anterior chamber indices influence the E-value.

Changes in the ABCD Keratoconus Grade After Intracorneal Ring Segment Implantation.

PURPOSE: To assess the changes in the ABCD keratoconus staging system 6 months after intracorneal ring segment implantation. METHODS: Fifty eyes of 50 patients with keratoconus who were implanted with the Keraring (Mediphacos, Belo Horizonte, Brazil) using the femtosecond laser were assessed. Preoperative and postoperative assessments included determination of distance uncorrected visual acuity and distance corrected visual acuity (DCVA), refraction, and Scheimpflug tomography with the Pentacam HR. In the ABCD keratoconus staging system, the elements A, B, C, and D stand for anterior and posterior radii of curvature in a 3.0-mm zone centered on the thinnest point (TP), corneal thickness at the TP, and DCVA, respectively. RESULTS: Keraring implantation produced significant flattening changes (preoperatively vs. postoperatively) in the anterior (6.60 ± 0.48 vs. 7.22 ± 0.57 mm, P < 0.001) and posterior (4.99 ± 0.47 vs. 5.16 ± 0.53 mm, P = 0.002) radii of curvature of the 3-mm zone centered on the corneal TP associated with a statistically significant improvement in the DCVA (0.56 ± 0.24 vs. 0.70 ± 0.22 in the decimal notation, P = 0.001) with no significant change in the corneal thickness at the TP (P = 0.285). The most changes occurred in element A of the ABCD keratoconus classification. Also, a 1-stage change was observed for element B, whereas elements C and D did not show changes in their postoperative stages after ring implantation. ABCD keratoconus staging before ring implantation was A2B3C2D1 and changed to A1B2C2D1 6 months after surgery. CONCLUSIONS: The ABCD staging system provides a more comprehensive guide that better illustrates the structural changes and visual acuity as one aspect of visual function after the implantation of the intrastromal corneal ring segments.

Effect of Induced Vertical Disparity on Horizontal Fusional Reserves.

PURPOSE: The aim of this study was to investigate the effects of induced vertical disparity on horizontal fusional reserves at near. MATERIALS AND METHODS: In 170 healthy subjects wearing best corrective refraction, the negative and positive horizontal fusional reserves were measured with base-in (BI) and base-out (BO) prisms, respectively, in the presence of 0.5 prism diopters (∆) and 1∆ vertical prisms placed in trial frames in front of the right eye. The prism power was slowly increased step by step until the subject reported sustained blur, break, and recovery. These were compared to horizontal fusional reserves in the same subjects without a vertical prism. Data were analyzed in SPSS.17 software using a repeated measures ANOVA. RESULTS: Induced vertical disparity decreased negative fusional reserves (NFR) horizontally and was more significant with 1∆ vertical disparity (P<0.001). There were significant differences between the blur (P<0.001), break (P<0.001), and recovery (P<0.001) for NFR before and after induced vertical disparity and no significant difference between blur (P=0.173) and recovery points (P=0.261) with a marginal difference for break points (P=0.045) for the positive fusional reserves (PFR). CONCLUSION: Inducing vertical disparity even with small magnitudes affects all 3 aspects (blur, break, and recovery) of horizontal negative fusional reserves while only break is affected in positive fusional reserves. These changes are statistically significant but do not seem to be clinically significant except for cases accompanied by symptoms.

Pattern Visual Evoked Potentials in Dyslexic Children.

PURPOSE: This study aimed to compare pattern visual evoked potential (PVEP) components in dyslexic and normal children. METHODS: This cross-sectional analytic study recruited 72 children, including 36 dyslexic and 36 normal participants aged 8-12 years. Visual examinations included measurement of distance visual acuity, refraction, and PVEP components of amplitudes and latencies with two different check sizes of 15 and 60 minutes (min) of arc at two contrast levels of 25% and 100%. RESULTS: Our results demonstrated significant differences between dyslexic and normal children in terms of P100 latency and amplitude of PVEP at 25% contrast, with check sizes of 15 and 60 min of arc. However, there were no significant differences between the two groups regarding P100 latency and amplitude at 100% contrast with check sizes of both 15 and 60 min of arc. CONCLUSION: Dyslexic participants showed reduced amplitude and prolonged latency in most PVEP components at low-contrast levels. These findings may support the magnocellular deficit hypothesis in dyslexic participants, even though the parvocellular pathway remains intact.

Accommodative amplitude using the minus lens at different near distances.

PURPOSE: The purpose of this study was to compare the mean findings and the repeatability of the minus lens (ML) amplitude of accommodation (AA) at 33 cm and 40 cm. MATERIALS AND METHODS: AA was measured from the dominant eye of 120 fully corrected subjects using the ML procedure when viewing the target at both 33 and 40 cm. Each measurement was repeated between 24 and 48 hours after the first trial. RESULTS: Mean AA when tested at 33 cm and 40 cm was 10.20 diopter (D) (standard deviation [SD] =1.24) and 8.85 D (SD = 1.23), respectively (P < 0.001). The limits of agreement of the measured amplitude calculated with taking into account of the replicates at 33 and 40 cm were - 0.19 (95% confidence interval [CI]: -0.34 to -0.04) and 2.53 (95% CI: 2.38 to 2.68), respectively. The repeatability of testing at the two distances 33 and 40 cm was ± 1.24 and ± 0.99, respectively. In addition, the retest reliability of measured amplitude using the intraclass correlation coefficient was 0.87 (95% CI: 0.789-0.920) at 33 cm and 0.91 (95% CI: 0.872-0.945) at 40 cm. CONCLUSION: There is no agreement in the obtained amplitude at the two measurement distances. Testing the ML AA at 40 cm may be superior given that a lower repeatability coefficient was observed. However, it is unclear whether the larger amplitude measured at 33 cm reflects a larger increase in accommodation (greater proximity effect) or a decrease in the ability to perceive the first slight sustained blur.

Amplitude of accommodation in an 11- to 17-year-old Iranian population.

PURPOSE: The aim was to determine normal values of accommodative amplitude (AA) during adolescence in Iran. METHODS: In this cross-sectional study, sampling was done from high school students in Kermanshah in 2015 through a multi-stage cluster sampling method and selected students were invited to participate in the study. Examinations were performed on-site at each sampled high school. All students had visual acuity and refractive examination followed by measurement of AA. Accommodative amplitude was tested with Donder's push-up method using a Royal Air Force (RAF) near point rule. RESULTS: Of the 1,070 selected students, 901 were included in the study and their mean age was 14.4 ± 1.7 years. Mean AA in this study was 11.53 ± 3.02 D (range: 5.00-28.50 D). Mean AA was 15.33 D in 11-year-olds and significantly decreased with age, until it reached 10.40 D in the 17-year-old age group. Mean AA in boys and girls were 10.09 ± 2.48 D and 11.65 ± 3.03 D, respectively. Based on the multiple linear regression model, younger age (coefficient = -0.774) and female gender (coefficient = 1.060) significantly associated with AA. CONCLUSION: This study showed that the AA in Iranian teenagers is lower than that calculated with Hofstetter's formula. It is important to take account of this point when making diagnostic and therapeutic decisions.

Evaluating Three Different Methods of Determining Addition in Presbyopia.

PURPOSE: To compare three different methods for determining addition in presbyopes. METHODS: The study included 81 subjects with presbyopia who aged 40-70 years. Reading addition values were measured using 3 approaches including the amplitude of accommodation (AA), dynamic retinoscopy (DR), and increasing plus lens (IPL). RESULTS: IPL overestimated reading addition relative to other methods. Mean near addition obtained by AA, DR and IPL were 1.31, 1.68 and 1.77, respectively. Our results showed that IPL method could provide 20/20 vision at near in the majority of presbyopic subjects (63.4%). CONCLUSION: The results were approximately the same for 3 methods and provided comparable final addition; however, mean near additions were higher with increasing plus lens compared with the other two methods. In presbyopic individuals, increasing plus lens is recommended as the least time-consuming method with the range of ±0.50 diopter at the 40 cm working distance.

Estimation of the hybrid lens parameters through rigid gas permeable lens fitting.

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 < 0.001) (R(2) = 0.45). Moreover, we found a correlation between the power of the RGP and hybrid lens (P < 0.001) (R(2) = 0.4). However, a 0.5 mm decrease in the base curvature radius of the RGP lens increased the vault of the hybrid lens by 72 µ. CONCLUSION: The results of this study could be used for better and faster selection of the first hybrid contact lens.

Corneal Biomechanical Changes Following Toric Soft Contact Lens Wear.

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 Kmean 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.

Prevalence of Refractive Errors among High School Students in Western Iran.

PURPOSE: To determine the prevalence of refractive errors among high school students. METHODS: In a cross-sectional study, we applied stratified cluster sampling on high school students of Aligoudarz, Western Iran. Examinations included visual acuity, non-cycloplegic refraction by autorefraction and fine tuning with retinoscopy. Myopia and hyperopia were defined as spherical equivalent of -0.5/+0.5 diopter (D) or worse, respectively; astigmatism was defined as cylindrical error >0.5 D and anisometropia as an interocular difference in spherical equivalent exceeding 1 D. RESULTS: Of 451 selected students, 438 participated in the study (response rate, 97.0%). Data from 434 subjects with mean age of 16±1.3 (range, 14 to 21) years including 212 (48.8%) male subjects was analyzed. The prevalence of myopia, hyperopia and astigmatism was 29.3% [95% confidence interval (CI), 25-33.6%], 21.7% (95%CI, 17.8-25.5%), and 20.7% (95%CI, 16.9-24.6%), respectively. The prevalence of myopia increased significantly with age [odds ratio (OR)=1.30, P=0.003] and was higher among boys (OR=3.10, P<0.001). The prevalence of hyperopia was significantly higher in girls (OR=0.49, P=0.003). The prevalence of astigmatism was 25.9% in boys and 15.8% in girls (OR=2.13, P=0.002). The overall prevalence of high myopia and high hyperopia were 0.5% and 1.2%, respectively. The prevalence of with-the-rule, against-the-rule, and oblique astigmatism was 14.5%, 4.8% and 1.4%, respectively. Overall, 4.6% (95%CI, 2.6-6.6%) of subjects were anisometropic. CONCLUSION: More than half of high school students in Aligoudarz had at least one type of refractive error. Compared to similar studies, the prevalence of refractive errors was high in this age group.

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.