Astigmatism

To examine the prevalence of anisometropia of spherical refraction (AnisoSR), astigmatism (AnisoAST) and spherical equivalent (AnisoSE) and their associations with spherical refraction (SR), refractive astigmatism (AST), spherical equivalent (SE) and interocular differences of ocular biometric parameters among elderly female twins. Refraction of 117 monozygotic (MZ) and 116 dizygotic (DZ) female twin subjects aged 66-79 years was assessed with an auto-refractor (Topcon AT) and controlled by subjective refraction. Corneal refraction, anterior chamber depth and axial length were measured with a Zeiss IOL Master. Participants with eyes operated for cataract or glaucoma were excluded, but the grade of nuclear opacity was not recorded. The associations between the absolute values of AnisoSR, AnisoAST and AnisoSE with SR, AST, SE, corneal refractive power (CR), corneal astigmatism (CAST), anterior chamber depth (ACD) and axial length (AL) and with their interocular differences were calcul...

The rate of visual impairment has been on a steady increase with several implicating factors. This has led to a more detailed attention in the trend of occurrence of visual defects and diagnosis. Among several reports, it has been recorded that medical students tend to have the most reported visual defects among other professions. Medical schools at Singapore, Taiwan, Denmark and Norway showed prevalence of eye defects among their students at the rate of 89.8%, 90%, 50% and 50.3% respectively. This study therefore aimed at recognizing the prevalence of common eye defects such as myopia, hypermetropia, colour blindness (daltonism) and astigmatism as well as identifying various factors responsible for the occurrence of these visual defects. A total of 200 medical students (aged 14 to above 40 years) in Dominica were examined. Refractive error and colour blindness were checked by using standard rudimentary tests. Additional demographical data was obtained through self-administered questionnaire. Among the students tested, 49.5% presented with at least one eye

To evaluate the consecutive treatment results regarding pterygium recurrence and the efficacy of exclusive strontium-/yttrium-90 beta-irradiation for primary and recurrent pterygia and to analyze the functional outcome. Between October 1974 and December 2005, 58 primary and 21 recurrent pterygia were exclusively treated with strontium-/yttrium-90 beta-irradiation with doses ranging from 3,600 to 5,500 cGy. The follow-up time was 46.6 +/- 26.7 months, with a median of 46.5 months. The treatment led to a size reduction in all pterygia (p < 0.0001). Neither recurrences nor side effects were observed during therapy and follow-up in this study. Best-corrected visual acuity increased (p = 0.0064). Corneal astigmatism was reduced in recurrent pterygia (p = 0.009). Exclusive strontium-/yttrium-90 beta-irradiation of pterygia is a very efficient and well-tolerated treatment, with remarkable aesthetic and rehabilitative results in comparison to conventional treatments, especially for recur...

Refractive errors are a major cause of visual impairment in the population. To find the pattern of refractive errors among patients evaluated in a tertiary care hospital in the western region of Nepal. The present hospital-based retrospective study was conducted in the Department of Ophthalmology of the Manipal Teaching Hospital, situated in Pokhara, Nepal. Patients who had refractive error of at least 0.5 D (dioptre) were included for the study. During the study period, 15,410 patients attended the outpatient department and 10.8% of the patients were identified as having refractive error. The age of the patients in the present study ranged between 5 - 90 years. Myopia was the commonest refractive error followed by hypermetropia. There was no difference in the frequency of the type of refractive errors when they were defined using right the eye, the left eye or both the eyes. Males predominated among myopics and females predominated among hypermetropics. The majority of spherical er...

To compare treatments with wavefront optimized and custom-Q ablations. Two consecutive groups of eyes were treated for myopia and astigmatism with surface ablation. One group was treated with wavefront optimized ablation and the second group was treated with custom-Q ablation. Preoperative and 3-month postoperative Q-values, higher order aberrations, low contrast visual acuity, and classic outcome parameters were analyzed. The wavefront optimized ablation group was comprised of 46 eyes of 23 patients with a mean spherical equivalent refraction (SE) of -3.64 diopters (D) (range: -1.15 to -8.25 D); mean Q-value changed from -0.33 preoperatively to 0.06 postoperatively. The custom-Q ablation group was comprised of 42 eyes of 21 patients with a mean SE of -3.24 D (range: -1.47 to -8.00 D); mean Q-value changed from -0.36 preoperatively to -0.03 postoperatively. A statistically significant difference in postoperative change in Q-values (P = .049) between the two groups was noted, but the...

The purpose of this study was to compare refractions measured with an autorefractor and by retinoscopy with and without cycloplegia. The objective refractions were performed in 199 right eyes from 199 healthy young adults with a mean age of 21.6 ± 2.66 years. The measurements were performed first without cycloplegia and repeated 30 min later with cycloplegia. Data were analysed using Fourier decomposition of the power profile. More negative values of component M and J0 were given by non-cycloplegic autorefraction compared with cycloplegic autorefraction (p < 0.0001). However more positive values for the J45 vector were given by non-cycloplegic autorefraction, although this difference was not statistically significant (p = 0.233). By retinoscopy, more negative values of component M were obtained with non-cycloplegic retinoscopy (p < 0.0001); for the cylindrical vectors J0 and J45 the retinoscopy without cycloplegia yields more negative values (p = 0.234; p = 0.112, respectively). Accepting that differences between cycloplegic and non-cycloplegic retinoscopy are only due to the accommodative response, the present results confirm that when performed by an experienced clinician, retinoscopy is a more reliable method to obtain the objective starting point for refraction under non-cycloplegic conditions.

To determine the long-term safety and effectiveness of laser in-situ keratomileusis (LASIK) in the treatment of refractive errors following penetrating keratoplasty (PK). A retrospective review was performed of 57 eyes of 48 patients with anisometropia or high astigmatism who were unable to wear glasses or a contact lens after PK and who underwent LASIK for visual rehabilitation. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BCVA), and corneal transplant integrity were recorded before surgery as well as up to 60 months after LASIK. The mean follow-up after the LASIK was 21.4 +/- 14.2 months (range 3 to 60 months). Mean preoperative spherical equivalent (SE) was -4.19 +/- 3.38 D. The mean preoperative astigmatism was 4.67 +/- 2.18 D. Preoperative BCVA was 20/40 or better in 42 eyes (74%). At 2 years the mean SE was -0.61 +/- 1.81 D, and mean astigmatism was 1.94 +/- 1.35 D for the 28 eyes with follow-up. UCVA was 20/40 or better in 12 eyes (43%), and BCVA was 20/40 or better in 24 eyes (86%) at 2 years. A gain in BCVA of 1 line or more was seen in 8 eyes (29%). Two eyes (7%) had loss of 2 or more lines of BCVA at 2 years. There were 9 eyes (16%) that developed epithelial ingrowth. Five eyes (9%) in this series had repeat corneal transplants. LASIK is effective for reducing ametropia after PK. Proper patient counseling is necessary because the results of LASIK after PK are not as good as, and complications are more frequent than in eyes with naturally occurring myopia and astigmatism. Complications are especially common in patients with mismatch of the donor and host cornea or in those with poor endothelial cell function.

Refractive procedures enjoy very high success rates and are among the most commonly performed elective surgeries in medicine. With better insights into preoperative screening, the overwhelming majority of cases have successful outcomes. Unfortunately, however, all refractive surgeons must appropriately manage unsuccessful cases. Unsuccessful refractive surgery procedures may relate to each step of the refractive surgery process: preoperative screening, surgical planning, intraoperative events, and postoperative biomechanical or healing anomalies. This paper reviews the management of unsuccessful laser-assisted in situ keratomileusis (LASIK) procedures, focusing on significant advances related to wavefront-guided therapeutic ablations.

The development of emmetropic refraction is known to be under visual control. Does partial spectacle correction of infants&#39; refractive errors, which has been shown to have beneficial effects in reducing strabismus and amblyopia, impede emmetropization? The purpose of the present study was to perform the first longitudinal controlled trial to investigate this question in human subjects. Children identified as having significant hyperopia in a population screening program at age 8 to 9 months were assigned to treated (partial spectacle correction) or untreated groups. A control group of infants with no significant refractive errors at screening was also recruited. Measurements of retinoscopic refraction under cycloplegia were taken at 4- to 6-month intervals up to the age of 36 months, and changes in refraction of 148 subjects were analyzed longitudinally. Refractive error decreased toward low hyperopic values between 9 and 36 months in both hyperopic groups. By 36 months, this re...

To compare the corneal astigmatism (magnitude and axis location) derived by total corneal power (TCP), automated keratometry, and simulated keratometry. Siriraj Hospital, Mahidol University, Bangkok, Thailand. Prospective comparative study. Eyes with previous ocular surgery or abnormalities were excluded. All patients were examined with the ARK 730A autokeratometer and the Galilei analyzer. The steepest and flattest corneal power along with the steepest axis of the TCP, automated keratometry, and simulated keratometry were recorded. Vector analysis (J0 and J45) was calculated. Analysis of variance with Bonferroni correction was performed for multiple comparisons. Outcome measures were the magnitude and axis location of astigmatism. One hundred eyes of 100 cataract patients were randomly selected. There was no statistically significant difference in the mean steepest axis between TCP (93.31 ± 68.75 [SD]), automated keratometry (94.24 ± 64.78), and simulated keratometry (92.42 ± 64.30). However, the mean magnitude of astigmatism measured by TCP (1.23 ± 0.75) was significantly higher than that measured by automated keratometry (0.93 ± 0.68) (P=.01) but not than that measured by simulated keratometry (1.08 ± 0.68) (P=.43); there was no statistically significant difference in J0 or J45. Twenty two (40%) of 54 eyes with more than 1.00 diopter of TCP astigmatism had more than 10 degrees of axis difference from automated keratometry. The magnitude of TCP astigmatism was higher than that of automated keratometry. The axis location was similar. However, there was more than 10 degrees of axis difference between automated keratometry and TCP in patients with high astigmatism. No author has a financial or proprietary interest in any material or method mentioned.

To determine astigmatic changes by vector analysis and postoperative refractive and visual outcomes after implantation of the monofocal aspheric bitoric AT Torbi 709M toric intraocular lens (IOL). Three centers in Salzburg, Austria, and Alicante and San Sebastián, Spain. Prospective interventional case series. Preoperative and postoperative visual acuity, subjective and objective refractions, and corneal radii using a topographer were examined in all patients. All patients had postoperative examinations within the first week and at 6 to 12 weeks. Astigmatic changes were evaluated using the Alpins vector method based on 3 fundamental vectors as follows: target induced astigmatism (TIA), surgically induced astigmatism (SIA), and difference vector. The various relationships between these 3 vectors were calculated, providing an extensive description of the astigmatic correction achieved. Eighty-eight eyes (71 patients) were included. Postoperatively, refractive cylinder was reduced sign...

We investigated the relationship between myopia and peripheral refraction for distance and near vision by measuring peripheral refractive errors in 10 myopic and 10 emmetropic participants at viewing distances of 2.5 and 0.4 m. Measurements were made at the fovea, and at eccentricities of 10°, 20° and 30° in the temporal and nasal hemispheres of the horizontal visual field. Our results showed that peripheral astigmatism increased with increasing eccentricity, but there was no significant difference between refractive error groups except at 30° eccentricity in the temporal retina. Considering the Mean Spherical Equivalent errors, emmetropes became relatively myopic at peripheral eccentricities, but there was little change in myopes. The effect of viewing distance on astigmatism or Mean Spherical Equivalent error was not significant. Our results do not support the view that myopia is associated with changes in peripheral refraction during distance or near vision.