جستجوی مقالات مرتبط با کلیدواژه « astigmatism » در نشریات گروه « پزشکی »

This study aims to investigate the visual acuity and prognosis after photorefractive keratectomy among hyperopic patients with and without astigmatism.

In this interventional case series study, 74 eyes from 42 hyperopia patients with and without astigmatism who underwent photorefractive keratectomy using Allegretto EX500 excimer laser at Torfeh and Negah Eye Hospitals from 2014 to 2018 were enrolled. Pre-and postsurgical visual examination findings, including uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction, cyclorefraction, and slit lamp examinations to measure ocular pressure and the presence or absence of haze, were recorded.

The mean age of participants was 34 ± 9 years, and 54.8 % were female. The preoperative mean uncorrected distance visual acuity was 0.55 ± 0.25 LogMAR, which significantly improved to 0.11 ± 0.14 at 6 months postoperatively (P < 0.0001). The predictive value for surgical outcomes at six months post-operation was 71.6 % within ± 0.5 diopter, 89.2 % within ± 1 diopter, and 97.3 % within ± 2 diopters. No eye lost corrected distance visual acuity of two lines or more, and only 16.6 % (12 eyes) experienced a one-line reduction in corrected distance visual acuity. No other notable complications occurred.

Photorefractive keratectomy using Allegretto EX500 excimer laser is an effective and safe method for correcting mild to moderate hyperopia with or without astigmatism.

Refractive errors are among the most common causes of vision loss in patients attending healthcare facilities in the first and second decades of life. Astigmatism stands out as one of the common and treatable causes of vision loss in pediatrics. 

In this cross-sectional study, the samples were chosen by random cluster sampling among children aged between 7 and 13 years from elementary schools in 2014-2015 academic year. For all students, refractive errors were assessed by Autorefractor Keratometer and retinoscopy. Internal astigmatism was defined as the difference between refractory and corneal astigmatism. SPSS software, version 16 was used for data analysis.

A total of 1009 children participated in the study. Among them, 468(46.4%) were male, and 541(53.6%) were female. Their mean age was 9.2±1.7 years. About 14.5% of them had refractory astigmatism. Corneal astigmatism was the most common type, with 12.5% of students suffering from it. The prevalence of corneal astigmatism was not significantly different between males and females (P=0.19). Also, there was no significant relationship between increasing age and prevalence of astigmatism in this age group (P=0.06).

There was no significant difference in the rate of refractory astigmatism, lenticular and corneal astigmatism, between males and females. Because correcting refractory errors in students has a positive effect on learning ability and physical and mental development, screening and follow-up are recommended in this age group.

The purpose of the present study was to determine the refractive profile of strabismic children under 8 in a tertiary referral center in Tehran, Iran.

This retrospective cross-sectional study was conducted on the medical records of 357 patients under the age of 8 who had one type of strabismus in Farabi Hospital, Tehran, Iran, between 2015 and 2019. All routine ophthalmic examinations were done for all patients. Cycloplegic refraction was performed after the instillation of two drops of cyclopentolate 1% with an interval of 5 minutes, and the refractive error was measured after 30 minutes. The diagnostic criteria were based on cycloplegic refraction in which myopia, hyperopia, and astigmatism were defined when the refractive error was -0.25, +0.75, and -0.50 diopter (D) or more, respectively. The cycloplegic results were classified into different groups with an interval of 1.00 D, and astigmatism was also assessed separately.

In this study, the most common type of refractive error in esotropic patients was hyperopia, with the +2.00 to +4.00 D range having a higher prevalence. In exotropic patients, hyperopia was also prevalent; the most common range of hyperopia was between +0.75 to +1.00 D. Astigmatism had a prevalence of 37.8% in esotropic patients, and 17.2% in exotropic patients with the most common range from -0.50 to -1.00. Myopia was present in 2.8% of patients with esotropia and 3.2 % of patients with exotropia with the most common range from -0.25 to -1.00.

In strabismic Iranian children, hyperopia was the most prevalent refractive error in both esotropic and exotropic patients, with higher degrees of hyperopia in esotropic patients. Low astigmatism was twice as prevalent in patients with esotropia as in patients with exotropia. Low myopia was the least prevalent in both esotropic and exotropia.

We aimed to report the five-year results of Trans-epithelial Photorefractive Keratectomy (TPRK) in treating all kinds of refractive errors. In this retrospective cohort study, we quantitatively compared the clinical findings and assessment of optical and refractive parameters, including slit-lamp, corneal topography, Best Corrected Visual Acuity (BCVA), and Uncorrected Distance Visual Acuity (UDVA) in 172 eyes of myopic, hyperopic, and astigmatic patients before and five years after trans-PRK. The average time for post-surgery epithelial healing was 2.97 0.83 days in male and 2.94 0.87 days in female patients; the pain score in a week following the operation was 1.88 0.68 in males and 2.25 0.73 in females. Corneal haze was observed in five patients. No long-term adverse effect was reported. The pre-operative UDVA was 0.84 0.32 in male and 0.87 0.34 in female patients; while the postoperative UDVA was -0.02 0.04 in male and -0.01 0.02 in female patients. There was a highly significant correlation (P<0.001) in all indices except UDVA, which was almost near to being significant (P=0.07). In this survey, the mean safety and index were nearly 1.00. TPRK is a safe and efficient therapeutic procedure to treat all types of refractive errors, including myopia, hyperopia, and astigmatism, with no significant adverse effect. Being touchless and having a short recovery time are two main characteristics of this refractive surgery.

To assess the prevalence and distribution of refractive errors in Madang Province, Papua New Guinea (PNG).

A retrospective hospital‑based study was conducted at Madang Provincial Hospital Eye Clinic. It is a free eye clinic and spectacle costs are further subsidized by a nongovernmental organization. Nonprobability purposive sampling was used to retrieve patients’ records at the eye clinic from January to December 2016. Only demographic and clinic data on the patients’ first visit to the eye clinic were recorded and these included their age, gender, location, presenting visual acuity (VA), and refractive correction.

One thousand and one hundred eighty‑four patients’ records were retrieved, of which 622 (52.53%) had refractive error. The mean age of refractive error presentation was 49.68 ± 16.29 years with a range of 9–86 years. There were more males (55%) than females. About a quarter of the patients (21.2%) presented with moderate visual impairment. There was a statistically significant relationship between visual impairment and age group (P < 0.001). Myopia (53.1%) was the most common type of refractive error followed by hyperopia (32.5%) and astigmatism (14.4%). The uptake of spectacle correction was very high (95.3%) among the patients. More than one‑tenth of the patients(12.5%) reported from other provinces. Almost one‑third of the patients (31.4%) could not obtain a VA of 6/6 after refraction. About one‑fifth (17.0%) of the patients were suspected of functional amblyopia.

Uncorrected refractive error (URE) is a significant cause of visual impairment in PNG. There is a need for the integration of eye care services into primary health care for early detection, treatment, and prevention of visual impairment caused by UREs.

To analyze the biometric values and the prevalence of corneal astigmatism in cataract surgery candidates.

This is a prospective study. Ocular biometric values and corneal keratometric astigmatism were measured by optical low‑coherence reflectometry (Lenstar LS 900) before surgery in patients who were candidates for cataract extraction surgery. Descriptive measurements of biometric dimensions and keratometric cylinder data and their correlations with sex and age were evaluated.

Ocular biometric and keratometric values from 2084 eyes of 2084 patients (mean age 66.43, range 19–95 years) were analyzed. The mean values were as follows: corneal astigmatism 0.89 diopter (D), mean corneal keratometry 44.29 D, central corneal thickness 534 μ, internal anterior chamber depth (ACD) 3.11 mm, lens thickness 4.50 mm, and axial length 23.35 mm. Corneal astigmatism was <1.25 D in 1660 (79.5%) of eyes. Astigmatism was with‑the‑rule in 976 (46.8%) of eyes, against‑the‑rule (ATR) in 702 (33.7%), and oblique in 406 (19.5%). Analysis of corneal astigmatism revealed a change toward “ATR” with age which was not statistically significant. The ACD was correlated with age. The amount of corneal astigmatism had no correlation with age and sex.

Corneal astigmatism was higher than 1.25 D in about 21% of cataract surgery candidates with slight differences between the various age ranges and had no correlation with age and sex.

To evaluate the effect of opposite clear corneal incisions (OCCI) with 4 mm incisions on the steep meridian on postoperative astigmatism.

This study was performed on 64 eyes of 55 patients with keratometric astigmatism of ≥ 1 diopter (D) undergoing phacoemulsification. Patients were divided into two groups, with‑the‑rule (WTR) astigmatism and against‑the‑rule (ATR) astigmatism. Initial incisions in the WTR group were performed on the temporal side with 3.2 mm keratome and paired stab incisions were performed on the steep meridian. At the end of the surgery, stab incisions were enlarged to 4 mm. Follow‑up visits were scheduled at 1, 3, 6, and 12 months postoperatively, which included refraction and keratometry.

It was found that the mean preoperative keratometric astigmatism was 2.06 ± 0.86 D. The postoperative mean keratometric astigmatism was 1.3 ± 0.7 D after 1 month and 1.2 ± 0.7 D after 12 months. The mean astigmatism correction between the preoperative measure and that taken at 1 month was statistically significant (P = 0.001), but there was no significant change in the severity of astigmatism afterward. The mean surgically‑induced astigmatism was found to be 1.99 ± 0.9 D. The 12‑month changes of mean absolute astigmatism were: 1.06 ± 0.7 D in the WTR group, and 0.53 ± 0.7 D in the ATR group. The difference between the two groups was statistically significant (P = 0.02).

Based on our findings, we posit that paired OCCI on the steep axis, using 4 mm incisions is an effective technique to correct preoperative astigmatism.

Ocular chemical injury is an ophthalmic emergency that may be challenging to manage. Here, we presented a case of persistent corneal astigmatism secondary to chemical burn with superficial limbal injury and no corneal involvement.

The case was a 36-year-old man who presented with a chemical acid injury in the right eye. He had sectorial superficial involvement of inferior limbus from 4 to 5 o’clock hours, and the cornea was clear. Corneal topography showed high irregular astigmatism that was not corrected with glass. In long-term follow-up, changes in topographic parameters happened very slowly.

In conclusion, optical corneal changes should be considered in the ocular surface chemical burn, especially in sectorial involvement despite clear cornea.

 To evaluate the stabilization time of astigmatism and refractive errors after cataract surgery using phacoemulsification and foldable lens implantation.

 The present cross-sectional study was carried out with convenience sampling method and included patients who underwent cataract surgery using phacoemulsification and implantation of foldable intraocular lens. The patients were evaluated and their data including age, sex, uncorrected visual acuity, best corrected visual acuity,  corneal cylinder, cylinder axis,  Sim K, and intra ocular pressure were recorded prior to the surgery as well as in days 2, 3, 4, weeks 1, 2, 5 and day 75 post surgery.

 Eighty one eyes of 77 patients with mean age of 61.39 ± 10.9 years were evaluated. The mean follow up time was 60.5 ± 48.86 days. The mean keratometry before surgery was 44.90 ± 1.85 diopters, while the mean axial length, the mean intraocular pressure and the mean astigmatism were 23.15 ± 1.98 mm, 14.01 ± 2.95 mmHg and 0.99 ± 1.10 diopters, respectively. The mean postoperative keratometry at last visit was 45.34 ± 1.80 diopters, and the mean intraocular pressure and astigmatism were, 12.46 ± 2.87 mmHg and 1.14 ± 0.96 diopters, respectively. The mean time for refraction stabilization was 11.46 ± 11.40 days and the mean stabilization time for astigmatism was 10.18 ± 11.34 days.

 In the present study the mean stabilization time for refraction and astigmatism after cataract surgery in an Iranian population using phacoemulsification and foldable lens implantation was comparable with previous studies.

To determine the prevalence of asthenopia and its associated factors in a sample of university students in Iran.

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.

Of the 1,462 students (mean age: 22.8 ± 3.1 years), 73% were women. The age- and genderstandardized 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 < 0.001), and astigmatic participants (P < 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 < 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).

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.

To evaluate the effect of intraocular pressure on topographic findings of donor corneas.

In the present study 37 intact enucleated globes were included. Desirable intraocular pressure was provided by fluid flowing into the globe using a needle inserted via the optic nerve connected to a balanced salt serum bottle. The Sim K and corneal astigmatism in different IOPs (0, 10, 20, 30, 40 and 50 mmHg) were measured using a topography cone (Zeiss-Humphery System, Atlas Version 10.1).

Out of 37 globes studied, 26 globes (70.3 %) were from male and 11 globes (29.7 %) were from female donors. Donors were aged 25 to 45 years at time of death with the mean age of 37 years. The mean Sim K was not significantly different in different IOP levels (0 to 50 mmHg). The mean corneal astigmatism had a significant relation with IOP (P < 0.001) and decreased (IOP 0 mmHg to IOP 30 mmHg) then increased (IOP 30 mmHg to IOP 50 mmHg) when the IOP was changed. The minimum astigmatism was detected at IOP 30 mmHg (1.56 D) and the maximum was detected at IOP 0 mmHg (2.76 ± 1.73).

The mean Sim K of donor cornea does not significantly change in different IOP levels of enucleated globe, while the corneal astigmatism changes significantly.  It seems that keratometric readings from donor cornea might be used without caution about the IOP in enucleated globe.
 

To determine the agreement of table-mounted and handheld auto-refractometers and to evaluate the effect of age and different types of refractive errors on this comparison.

In this cross-sectional study conducted in 2015 using multi-stage cluster sampling, two underserved villages were selected randomly in the north and southwest of Iran. All the selected participants underwent optometric and ophthalmic examinations. Refraction was measured using handheld and table-mounted auto-refractometers in 652 subjects.

The mean age of the subjects was 32.7 ± 18.72 years, and 58.3% of them were female. A significant difference was observed in the results of sphere, spherical equivalent (SE), and J45 vector between the two devices (P < 0.012), but there was no significant difference in J0 vector. There was a significant difference in the results of sphere between the two devices in all age groups under 50 years (P ¼ 0.005), but there was no difference in age groups above 50 years. Correlation coefficients of the two devices were 0.989, 0.986, 0.908, and 0.951 for the results of sphere, SE, J0 vector, and J45 vector, respectively (P < 0.0001). The 95% limit of agreement (LOA) of the two devices was 0.31 to þ0.53 for sphere, 0.27 to þ0.63 for SE, 0.27 to þ0.27 for J0 vector, and 0.16 to 0.17 for J45 vector.

According to our findings, the spherical error and cylindrical power measurements of the two devices have a significant correlation. Although there is a significant difference in the mean values between the two devices, this difference may be considered clinically insignificant, and considering the narrow 95% LOA between the two devices, the results may be used interchangeably.