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Optometry and Vision Science : Official... Jul 2012To characterize astigmatism as a function of age in a Hong Kong clinical population. (Comparative Study)
Comparative Study
PURPOSE
To characterize astigmatism as a function of age in a Hong Kong clinical population.
METHODS
All records from new clinical patients at a university optometry clinic in the year 2007 were used for the study. Only data from subjects with corrected visual acuity ≥6/9 in both eyes and with completed subjective refraction were analyzed. The subjects were divided into seven age groups by decade (i.e., 3 to 10 years, 11 to 20 years, …, >60 years). Refractive errors were decomposed into spherical-equivalent refractive error (M), J0, and J45 astigmatic components for analyses. Internal astigmatism was calculated by subtracting corneal astigmatism from refractive astigmatism (RA).
RESULTS
Of the 2759 cases that fulfilled our selection criteria, 58.9% had myopia (M ≥-0.75 D) and 28.4% had RA (Cyl ≥ 1.00 D). The prevalence of RA increased from 17.8% in the 3 to 10 years age group to 38.1% in the 21 to 30 years age group. It then dipped to 25.8% in 41 to 50 years age group but increased again to 41.8% in the >60 years age group. Among the astigmats, almost all 3- to 10-year-old children (92.6%) had with-the-rule (WTR) astigmatism, but a majority of the elderly (>60 years) had against-the-rule (ATR) astigmatism (79.7%). For a subset of subjects who had both subjective refraction and keratometric readings (n = 883), RA was more strongly correlated with corneal (r = 0.35 to 0.74) than with internal astigmatism (r = 0.01 to 0.35). More importantly, the magnitudes of both refractive and corneal J0 were consistent with synchronized decrements (-0.15 and -0.14 D per 10 years, respectively) after the age of 30 years, indicating that the shift toward more ATR astigmatism was related to corneal change.
CONCLUSIONS
In this Hong Kong Chinese clinical population, the prevalence rates of both myopia and astigmatism increased during the first three decades and shared a similar trend before the age of 50 years. The manifest astigmatism was mainly corneal in nature, bilaterally mirror symmetric in axis, and shifted from predominantly WTR to ATR with age.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aging; Astigmatism; Child; Child, Preschool; Disease Progression; Female; Follow-Up Studies; Hong Kong; Humans; Male; Middle Aged; Population Surveillance; Prevalence; Prognosis; Refraction, Ocular; Retrospective Studies; Young Adult
PubMed: 22705776
DOI: 10.1097/OPX.0b013e31825da156 -
Journal of Cataract and Refractive... Jan 1989A human cadaver eye model was used to study the effects of various sized limbal and scleral-pocket-type incisions on corneal astigmatism. Limbal incisions of 5.0 mm and...
A human cadaver eye model was used to study the effects of various sized limbal and scleral-pocket-type incisions on corneal astigmatism. Limbal incisions of 5.0 mm and 10.0 mm and scleral pocket incisions of 3.5 mm and 7.0 mm were carefully placed in human cadaver eyes. These wounds were closed in a uniform fashion, first loosely and then tightly, using interrupted 10-0 nylon sutures. Pre-incision and post-incision keratometer readings were taken and the net change in astigmatic error was calculated. The results indicate that tighter sutures, larger wound size, and limbal rather than scleral-pocket-type incisions were associated with a greater degree of immediate postoperative astigmatism in the cadaver eye.
Topics: Astigmatism; Cadaver; Cataract Extraction; Cornea; Eye; Humans; Keratotomy, Radial; Postoperative Complications; Suture Techniques
PubMed: 2646428
DOI: 10.1016/s0886-3350(89)80135-x -
Cornea Aug 2018To assess the correlation between the scleral shape and corneal astigmatism.
PURPOSE
To assess the correlation between the scleral shape and corneal astigmatism.
METHODS
Twenty-two participants (11 nonastigmatic and 11 astigmatic) aged from 19 to 36 years and with no previous ocular surgeries were included in this study. Three-dimensional (3D) corneoscleral maps from both eyes (44 eyes) were acquired using a corneoscleral topographer (Eye Surface Profiler). Each 3D map was split into 13 concentric annuli, each 0.5-mm wide, starting at 1.0-mm radius from the corneal apex to the scleral periphery at 7.5 mm from the apex. Each ring was fitted to a quadratic function of the radial distance to the apex, to calculate the elevation difference between the raw data and the fitting surface ring. For each ring, the resulting elevation difference between the original and fit data profile was fit to a sum of sine function. Decentration and astigmatic terms obtained from the sinusoidal fit were analyzed and compared between nonastigmatic and astigmatic groups.
RESULTS
In astigmatic eyes, corneal and scleral asymmetry are highly correlated, but both appear independent of each other in nonastigmatic eyes. No significant difference between astigmatic and nonastigmatic eyes was found for the decentration term [P > 0.05/N (Bonferroni)], whereas for the astigmatic component, the differences were statistically significant [P < 0.05/N (Bonferroni)].
CONCLUSIONS
Corneal and scleral shapes are correlated in astigmatic eyes, which suggests that astigmatism is not restricted to the cornea but should rather be considered a property of the entire eye globe.
Topics: Adult; Astigmatism; Cornea; Corneal Topography; Female; Humans; Male; Refraction, Ocular; Sclera; Young Adult
PubMed: 29521692
DOI: 10.1097/ICO.0000000000001565 -
Journal of Cataract and Refractive... Sep 1994Using a modification of vector analysis for calculating surgically induced astigmatism, we describe a simple method that divides the induced cylinder into two orthogonal...
Using a modification of vector analysis for calculating surgically induced astigmatism, we describe a simple method that divides the induced cylinder into two orthogonal components. This decomposition allows with-the-rule and against-the-rule astigmatic changes to be calculated for individual case analysis, as well as for statistical analysis of aggregate data. Because it is based on the true induced cylinder, as determined by optical principles, this method overcomes some of the problems associated with earlier methods of evaluating surgically induced astigmatism.
Topics: Astigmatism; Cataract Extraction; Cornea; Humans; Mathematics; Refraction, Ocular
PubMed: 7996407
DOI: 10.1016/s0886-3350(13)80231-3 -
Indian Journal of Ophthalmology Oct 2020To evaluate the amount and type of surgically induced astigmatism (SIA) in manual small incision cataract surgery (SICS) with a 4.5 mm U-shaped scleral incision.
PURPOSE
To evaluate the amount and type of surgically induced astigmatism (SIA) in manual small incision cataract surgery (SICS) with a 4.5 mm U-shaped scleral incision.
METHODS
A prospective cross-sectional study was done on a total of 61 patients above 40 years of age with senile cataract. All patients underwent complete examination including preoperative uncorrected visual acuity (UCVA), refraction, best-corrected visual acuity (BCVA), and keratometry using a manual keratometer (Bausch and Lomb). All 61 patients underwent manual SICS with a 4.5 mm U-shaped scleral incision within the astigmatic neutral incisional funnel. Patients were thoroughly examined on immediate postoperative day 1 and findings of UCVA, BCVA, refraction, and keratometry were noted at the end of the 1 week, 4 week, and 6 week follow-up visits. SIA was calculated for all the follow-ups using the SIA calculator version 2.1, a free software program. The changes in the amount and type of postoperative SIA were tested for statistical significance using Fischer's exact test. Variance was tested using intraclass score effect. The threshold for statistical significance was set to P < 0.001.
RESULTS
Postoperatively, the average SIA was 0.43 ± 0.13 D at the end of 1 week, 0.29 ± 0.20 D at the end of the 4 week, and remained the same 0.29 ± 0.21 D at the end of 6 week. The type of astigmatism shifted more towards against-the-rule (ATR) type in 45.9% of cases during the final postoperative follow-up.
CONCLUSION
In our study, we conclude that the incision within the funnel of astigmatic neutralization is one of the major determinants of SIA in manual SICS. We were able to achieve phacocomparable SIA in our study mainly because of our type of incision.
Topics: Astigmatism; Cataract; Cataract Extraction; Cornea; Cross-Sectional Studies; Humans; Phacoemulsification; Postoperative Complications; Prospective Studies
PubMed: 32971618
DOI: 10.4103/ijo.IJO_1696_19 -
Eye (London, England) 1992Total post-operative refractive astigmatism and keratometric corneal astigmatism were determined in patients following cataract surgery. By comparing the results of the...
Total post-operative refractive astigmatism and keratometric corneal astigmatism were determined in patients following cataract surgery. By comparing the results of the two methods, the value of keratometry as a simple and quick procedure for identification of surgically induced astigmatic errors was established. It is proposed that this method should be used before final refraction in an attempt to increase clinic efficiency and reduce further appointments resulting from surgically induced astigmatism.
Topics: Astigmatism; Cataract Extraction; Cornea; Humans; Ophthalmology; Refraction, Ocular
PubMed: 1426403
DOI: 10.1038/eye.1992.12 -
Optometry and Vision Science : Official... Feb 2017Many studies have assessed the visual impact of astigmatism by inducing it using loose trial lenses at set axes. There are conflicting opinions and some confusion about...
PURPOSE
Many studies have assessed the visual impact of astigmatism by inducing it using loose trial lenses at set axes. There are conflicting opinions and some confusion about the results, but the reduction in vision is typically least with lens-induced with-the-rule astigmatism. In this study, we determined whether a participant's habitual astigmatism influences the impact of lens-induced astigmatism on distance visual acuity (VA).
METHODS
Participants included 35 adults (age range 19-79, average 41.3 ± 15.4 years), who were either astigmats (≥0.75DC; N = 21) or non-astigmatic controls (N = 14). Distance VA was measured using an automated FrACT (Freiburg VA) system with the participant's habitual correction, and then with the addition of a +1.00DC lens at either 90 or 180 degrees (control) or at and perpendicular to the axis of habitual astigmatism (astigmats).
RESULTS
The reduction in VA with induced astigmatism was significantly affected by whether the participant was a with-the-rule astigmat, against-the-rule astigmat, or non-astigmat (p = 0.006). Lens-induced astigmatism axis ≈ 180 (160-20°) reduced the VA less than axis ≈ 90 (70-120°) in the control group (reduction in mean VA of 0.32 SD ± 0.10 with 95% confidence intervals of [0.27,0.37] compared to 0.42 ± 0.09 [0.37,0.47] logMAR) and with-the-rule astigmats (reduction in VA of 0.31 SD ± 0.06 [0.27,0.35] compared to 0.45 SD ± 0.12 [0.38,0.52] logMAR). The against-the-rule astigmats had a very similar reduction in VA with the ≈+1.00DC axis 180 condition compared to the ≈+1.00DC axis 90 condition (reduction in VA of 0.26 SD ± 0.09 [0.21,0.31] compared to 0.25 SD ± 0.14 [0.17,0.33] logMAR).
CONCLUSIONS
The impact of lens-induced astigmatism was dependent on the refractive status of the participants. When investigating the impact of lens-induced astigmatism, it is important to consider the participants' habitual axis of astigmatism.
Topics: Adult; Aged; Astigmatism; Eyeglasses; Female; Humans; Male; Middle Aged; Refraction, Ocular; Vision Tests; Visual Acuity; Young Adult
PubMed: 27776084
DOI: 10.1097/OPX.0000000000001000 -
Klinische Monatsblatter Fur... Jul 2006Data on refraction of patients with congenital nystagmus are not available in the literature.
BACKGROUND
Data on refraction of patients with congenital nystagmus are not available in the literature.
PATIENTS AND METHODS
We have analysed the refractive errors in a cohort of 224 consecutive patients with congenital nystagmus, aged 1-57 years.
RESULTS
Refractive errors, i. e., myopia, hyperopia (> 0.50 dioptres) and astigmatism (> 1.25 dioptres), were found in 179 patients (79.91 %). Of them 8 were myopic (4.46 %), 19 were hyperopic (10.61 %) and 152 were astigmatic (84.91 %). Mean astigmatism was of 2.44 dioptres for right eyes and 2.74 dioptres for left eyes.
CONCLUSIONS
Astigmatism is extremely common in congenital nystagmus. Its presence is much higher than that found in normal populations. The amount of astigmatism found in nystagmus patients is noticeable. When considering he visual difficulties of patients with nystagmus, the astigmatic component should be taken in greatest consideration. Its presence should favour early surgery for anomalous head posture. Furthermore, refractive surgery should be considered as early as possible, for improving visual potential.
Topics: Adolescent; Adult; Astigmatism; Child; Child, Preschool; Comorbidity; Female; Humans; Incidence; Infant; Male; Middle Aged; Nystagmus, Congenital; Risk Assessment; Risk Factors
PubMed: 16855946
DOI: 10.1055/s-2006-926852 -
Archives of Ophthalmology (Chicago,... Aug 1980Astigmatic refractive errors may develop late in the visual maturity period of strabismic children. Seventeen strabismic children who had surgery and ten strabismic...
Astigmatic refractive errors may develop late in the visual maturity period of strabismic children. Seventeen strabismic children who had surgery and ten strabismic children who did not have surgery are discussed; none had astigmatic error at the initial refraction. Significant astigmatism developed in both groups at age 4 years and two years after the initial refraction. The ophthalmologist should be aware that late-developing astigmatism can cause a recurrence or deterioration of strabismus. The best response is serial refractions and appropriate correction of all strabismus patients during the visual maturity period.
Topics: Aging; Astigmatism; Child, Preschool; Humans; Infant; Recurrence; Refraction, Ocular; Strabismus
PubMed: 7417080
DOI: 10.1001/archopht.1980.01020040282014 -
PloS One 2015To determine the effects of optically imposed astigmatism on early eye growth in chicks.
PURPOSE
To determine the effects of optically imposed astigmatism on early eye growth in chicks.
METHODS
5-day-old (P5) White Leghorn chicks were randomly assigned to either wear, monocularly, a "high magnitude" (H: +4.00DS/-8.00DC) crossed-cylindrical lens oriented at one of four axes (45, 90, 135, and 180; n = 20 in each group), or were left untreated (controls; n = 8). Two additional groups wore a "low magnitude" (L: +2.00DS/-4.00DC) cylindrical lens orientated at either axis 90 or 180 (n = 20 and n = 18, respectively). Refractions were measured at P5 and after 7 days of treatment for all chicks (P12), whereas videokeratography and ex-vivo eyeshape analysis were performed at P12 for a subset of chicks in each group (n = 8).
RESULTS
Compared to controls, chicks in the treatment groups developed significant amounts of refractive astigmatism (controls: 0.03 ± 0.22DC; treatment groups: 1.34 ± 0.22DC to 5.51 ± 0.26DC, one-way ANOVAs, p ≤ 0.05) with axes compensatory to those imposed by the cylindrical lenses. H cylindrical lenses induced more refractive astigmatism than L lenses (H90 vs. L90: 5.51 ± 0.26D vs. 4.10 ± 0.16D; H180 vs. L180: 2.84 ± 0.44D vs. 1.34 ± 0.22D, unpaired two-sample t-tests, both p ≤ 0.01); and imposing with-the-rule (H90 and L90) and against-the-rule astigmatisms (H180 and L180) resulted in, respectively, steeper and flatter corneal shape. Both corneal and internal astigmatisms were moderately to strongly correlated with refractive astigmatisms (Pearson's r: +0.61 to +0.94, all p ≤ 0.001). In addition, the characteristics of astigmatism were significantly correlated with multiple eyeshape parameters at the posterior segments (Pearson's r: -0.27 to +0.45, all p ≤ 0.05).
CONCLUSIONS
Chicks showed compensatory ocular changes in response to the astigmatic magnitudes imposed in this study. The correlations of changes in refractive, corneal, and posterior eyeshape indicate the involvement of anterior and posterior ocular segments during the development of astigmatism.
Topics: Animals; Astigmatism; Chickens; Eye
PubMed: 25675443
DOI: 10.1371/journal.pone.0117729