The effect of anisometropia on stereopsis

Background and aim: For good stereopsis, the two retinal images should have similar clarity, shape, and size. Anisometropia is one of the factors which has affect on stereopsis. The purpose of this study was investigation of induced anisometropia effect on binocular function and stereopsis. Methods: In this semi experimental study, a total of 135 students from Zahedan University of Medical Sciences who had inclusion criteria were selected randomly. At the beginning of the work, the refractive errors of the subjects were determined and corrected with retinoscop and their stereopsis measured using T.N.O test. Subsequently, this hyperopic and myopic anisometropia induced by use of negative and positive spherical lenses (power 1, 2, 3 diopter) in trial frame in front of one eye and in each state stereopsis measured again. In agreement and against the rule astigmatic anisometropia induced by positive cylindrical lenses in 180 and 90 degree axes and stereopsis measured again. Data were analyzed by SPPS.14 software using within subjects factorial and repeated measurement ANOVA test. Results: This study showed that both type and amount of anisometropia had significant effect on stereopsis (P<0.001). The mean of stereopsis before intervention was (36.42±12.65). The most and least reduction of stereopsis were related to 3D hyperopic anisometropia (339.42±125.1) and 1D with the rule astigmatic anisometropia (36.57±12.6), respectively. The mean of stereopsis before and after different type and amount of induced anisometropia were significantly different (P<0.001). Conclusion: The result of this study showed that with increasing of anisometropia, stereoacuity decreases. Therefore, low degree of anisometropia, even 1D, can decrease both stereopsis and binocular function and thus, the amendment of stereopsis is necessary

Epidemiology of Dry Eye and Its Determinants Among University Students

This is a Letter to the Editor and does not have an abstract. Please download the PDF or view the article HTML

Abnormal Visual Function: An Under-recognized Risk Factor of Road Traffic Injuries

Purpose: To determine the relationship between road accidents with visual acuity, refractive errors, visual field, and contrast sensitivity. Methods: This population-based case–control study was conducted on roads leading to Tehran Province, Iran. The case group comprised drivers who had met with accidents and were at fault for the accident. The cases were selected in an ongoing manner (incidence cases). The controls were drivers who were the opposing victims in the same. After an initial interview, optometric and ophthalmic examinations including the measurement of visual acuity, refraction, visual field assessment, contrast sensitivity measurement, and slit lamp biomicroscopy were performed for all study participants. Results: In this study, 281 and 204 individuals were selected for the case and control groups. The mean uncorrected visual acuity was 0.05 ± 0.12 and 0.037 ± 0.10 logMAR in the case and control groups, respectively (P = 0.095). Of the participants in the case and control groups, 32.8% and 23% had a visual field defect in at least one eye, respectively (adjusted odds ratios [aOR] = 1.63, 95% confidence interval [CI]: 1.08–2.48; P = 0.021). Moreover, 16.2% of the cases and 8.3% of the controls had visual field defects in both eyes (aOR = 2.13, 95% CI: 1.17–3.86; P = 0.012). Contrast sensitivity was worse in the case group in all spatial frequencies under non-glare conditions. However, under glare conditions, the contrast sensitivity was significantly worse in the case group only in the spatial frequency of 12 cycles per degree (cpd). Conclusion: Reduced contrast sensitivity, especially under non-glare conditions, and visual field defects are risk factors that influence the prevalence of road accidents. It is strongly advised that special attention be paid to these visual functions in legal assessments to apply the necessary interventions in individuals with these types of disorders

The prevalence of ptosis in an Iranian adult population

AbstractPurposeTo determine upper eyelid ptosis prevalence and some related factors in 44- to 69-year-olds of Shahroud in the north of Iran.MethodsIn 2009, using multi-stage cluster sampling, 300 clusters of 40–64-year-olds were selected in Shahroud city, and all 5190 participants were invited to be re-examined in 5 years (2014). The current report is the second phase of the study in which 4737 (91.3%) people participated and underwent vision tests, slit lamp examination, biometry, and ophthalmoscopy in 2014. Upper eyelid ptosis was determined by an ophthalmologist.ResultsThe prevalence of upper eyelid ptosis was 4.7% [95% confidence interval (CI): 4.1–5.4]; 5.2% in women and in 4.0% in men. The prevalence of bilateral and unilateral ptosis was 1.3% (95% CI: 1.0–1.7) and 3.4% (95% CI: 2.8–4.0), respectively. The observed prevalence of ptosis was 3.1% in the 45- to 49-year age group and 5.8% in 65- to 69-year-olds. The prevalence of ptosis increased with age. In the multiple logistic regression model, ptosis prevalence correlated with older age, diabetes (odds ratio = 1.53, 95% CI: 1.16–2.02) and hypertension (odds ratio = 1.41, 95% CI: 1.03–2.92). Mean corneal astigmatism was 1.02 (95%C]: 0.87–1.18) diopter in ptotic eyes and 0.87 (95% CI: 0.84–0.89) diopter in non-ptotic eyes (p = 0.013).ConclusionsThe present report provides valuable information on the prevalence of ptosis in a population of 45-to 69-year-olds. The prevalence of ptosis in this study was considerably high and significantly increased with age

Near Points of Convergence and Accommodation in a Population of University Students in Iran

Purpose: To determine the distribution of the near point of convergence (NPC) and near point of accommodation (NPA) in a young student population in Iran. Methods: The subjects were selected using a cluster sampling method. All students underwent optometry tests, including visual acuity measurement, refraction, and cover test, as well as ophthalmic examinations. The NPC and NPA were measured using an accommodative target (near Snellen chart). Results: Of 1,595 students, the data of 1,357 were analyzed. The mean NPC and NPA in the total sample were 7.25 cm (95% confidence interval [CI], 7.02 to 7.48) and 9.99 cm (95% CI, 9.69 to 10.29), respectively. Older age was associated with an increase in the NPC, which increased from 6.98 cm in 18–20 years olds to 9.51 cm in those over 30 years. The NPA was significantly associated with age and refractive errors in the multiple linear regression model, increasing from 9.92 cm in 18–20 years olds to 11.44 cm in those over 30 years (P = 0.003). Hyperopic eyes had lower NPA than myopic and emmetropic eyes (P = 0.001). In younger age groups, the mean accommodation amplitude was lower than the mean Hofstetter value. Moreover, with age, especially after 30 years, the mean values surpassed those determined using the Hofstetter formula. Conclusion: The NPC values in this study were lower than those previously reported for identical age groups. The Hofstetter formula is not always an accurate predictor of the accommodation amplitude in the Iranian adult population

High Prevalence of Asthenopia among a Population of University Students

Purpose: To determine the prevalence of asthenopia and its associated factors in a sample of university students in Iran. Methods: In this cross-sectional study, participants were selected using multistage cluster sampling. Presence of at least one of the 10 symptoms—foreign body sensation, diplopia, blurred vision, eye swelling, dry eye, eye pain, difficulty in sustaining visual operations, decreased visual acuity, tearing, and photophobia—was considered as asthenopia. Ocular examinations, including uncorrected/corrected visual acuity measurement, objective/subjective refraction, cover test, amplitude of accommodation (AA), and near point of convergence (NPC) were performed. Results: Of the 1,462 students (mean age: 22.8 ± 3.1 years), 73% were women. The age- and gender standardized prevalence was 70.9% (95% confidence interval [CI]: 68.3–73.5), 39.8% (95% CI: 36.4–43.1), and 19.7% (95% CI: 16.0–23.3) based on the presence of at least one, two, and three symptoms, respectively. The prevalence was significantly higher in females (P = 0.048), hyperopic students (P &lt; 0.001), and astigmatic participants (P &lt; 0.001). The mean AA and NPC were 9.7 ± 2.6 D and 10.2 ± 4.2 D (P = 0.008) and 7.0 ± 2.1 cm and 7.7 ± 3.9 cm (P &lt; 0.001) in participants with and without asthenopia, respectively. Multiple regression model revealed age (28–29 years), astigmatism, and NPC as independent associated factors (odds ratios: 3.51, 1.61, and 0.91, respectively). Conclusion: This study shows relatively high prevalence of asthenopia in university students. Demographic factors and visual system disorders are important risk factors and timely correction of conditions may lead to decreased asthenopia

Outpatient and Hospitalization in Cataract Surgery: Iranian Cataract Surgery Survey

Background: To determine the prevalence of outpatient and hospitalization for cataract surgery in Iran.Methods: A random cluster sampling was done in a cross-sectional study on cataract surgeries performed in treatment centers of ophthalmology in Iran between 2000 and 2005. One week of each season was selected randomly and all cataract surgery files of the center were studied. This study reported the prevalence of outpatient surgery and length of hospital stay in all surgeries in Iran between 2000 and 2005.Results: Among 13,409 studied files on cataract surgery, mean hospitalization time was 0.79±0.82 days, 31.42% of surgeries were done on an outpatient basis, and 62.32% were hospitalized for one night. About 4.45% and 1.81% were hospitalized for two nights and more, respectively. Hospitalization time after surgery showed no significant difference with sex. Also, There was no significant difference between mean age of inpatients and outpatients (P=0.08). The most common method used for surgeries was Phaco (52.33%) and the least was lensectomy (11.38%).Conclusions: A major proportion of cataract surgeries required hospitalization. Due to the costs of hospitalization in this surgery, the phaco method can play an important role in reducing the costs of treatment.

Outpatient and Hospitalization in Cataract Surgery: Iranian Cataract Surgery Survey

Background: To determine the prevalence of outpatient and hospitalization for cataract surgery in Iran.Methods: A random cluster sampling was done in a cross-sectional study on cataract surgeries performed in treatment centers of ophthalmology in Iran between 2000 and 2005. One week of each season was selected randomly and all cataract surgery files of the center were studied. This study reported the prevalence of outpatient surgery and length of hospital stay in all surgeries in Iran between 2000 and 2005.Results: Among 13,409 studied files on cataract surgery, mean hospitalization time was 0.79±0.82 days, 31.42% of surgeries were done on an outpatient basis, and 62.32% were hospitalized for one night. About 4.45% and 1.81% were hospitalized for two nights and more, respectively. Hospitalization time after surgery showed no significant difference with sex. Also, There was no significant difference between mean age of inpatients and outpatients (P=0.08). The most common method used for surgeries was Phaco (52.33%) and the least was lensectomy (11.38%).Conclusions: A major proportion of cataract surgeries required hospitalization. Due to the costs of hospitalization in this surgery, the phaco method can play an important role in reducing the costs of treatment.

P100 Wave Latency and Amplitude in Visual Evoked Potential Records in Different Visual Quadrants of Normal Individuals

Purpose: Assessment of the pattern visual evoked potential (PVEP) responses in different areas of visual fields in individuals with normal vision. Methods: This study was conducted on 80 eyes of normal subjects aged 18–35 years. All participants underwent refraction and visual acuity examination. Visual evoked potential (VEP) responses were recorded in different areas of field. The repeated measure test was used to compare the P100 latency and amplitude of PVEP among different areas. Results: The repeated measures analysis of variance showed a statistically significant difference among different areas in terms of amplitude and latency of P100 (P = 0.002 and P &lt; 0.001, respectively). According to the results, the highest and lowest amplitude of P100 was observed in inferior-nasal and superior areas, respectively. The highest and lowest latency of P100 was related to the temporal and inferior-nasal areas, respectively. Conclusion: This study partially revealed the details of local PVEP distribution in the visual field and there was a significant difference in the amplitude and latency of PVEP wave in different areas of the visual field

Does Long-Term Night Shift Work Cause Dry Eye in Hospital Nurses?

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 &lt; 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