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Acta Ophthalmologica Sep 2018To describe the age-related changes in with-the-rule (WTR) and oblique keratometric astigmatism (KA), posterior corneal astigmatism (PCA) and total corneal astigmatism...
PURPOSE
To describe the age-related changes in with-the-rule (WTR) and oblique keratometric astigmatism (KA), posterior corneal astigmatism (PCA) and total corneal astigmatism (TCA).
METHODS
We used a Pentacam HR (high-resolution) rotating Scheimpflug camera to determine the KA, PCA and TCA in the right eyes of 710 patients, aged from 20 to 88 years. The age-related changes along the vertical, horizontal and oblique meridians were analyzed with Naeser's polar value method in a cross-sectional study.
RESULTS
In the whole group, all meridional astigmatic powers and polar values were stable in the age groups from 20 to 49 years, followed by a 1.0 dioptre (D) against-the-rule (ATR) change in KA and TCA, and a 0.12 D reduction in against-the-rule PCA. A nasal rotation of the steep meridian in KA and TCA was noted in the 70-88 years old. The PCA averaged approximately 0.25 D ATR in all age groups. Females displayed the same early astigmatic stability as in the whole group, while male eyes demonstrated a linear decay from 1.5 D WTR at 20 years to 0.5 D ATR astigmatism for the oldest patients.
CONCLUSION
Corneal astigmatism is stable until the age of 50 years; thereafter both keratometric and total corneal astigmatism show a 0.25 D ATR change per 10 years. The average 0.25 D ATR PCA compensates the predominant keratometric WTR astigmatism in the younger patients and increases the TCA in the elderly with keratometric ATR astigmatism. The gender-based differences in age-related astigmatism require further studies.
Topics: Adult; Age Factors; Aged; Aged, 80 and over; Aging; Astigmatism; Cornea; Corneal Topography; Cross-Sectional Studies; Denmark; Disease Progression; Female; Humans; Incidence; Male; Middle Aged; Refraction, Ocular; Retrospective Studies; Young Adult
PubMed: 29369508
DOI: 10.1111/aos.13683 -
BMC Ophthalmology Apr 2020Currently, various types of toric intraocular lenses (IOL) have been manufactured and can be divided into three types according to the location of correction component;... (Comparative Study)
Comparative Study
BACKGROUND
Currently, various types of toric intraocular lenses (IOL) have been manufactured and can be divided into three types according to the location of correction component; front-toric IOL (correction on anterior IOL surface), back-toric IOL (correction on posterior IOL surface), and bi-toric IOL (correction on both anterior and posterior IOL surfaces). In this study, we aimed to investigate the effectiveness of reducing corneal astigmatism of either normal or post-penetrating keratoplasty (PKP) corneas according to the type of implanted toric IOLs.
METHODS
Medical records were retrospectively reviewed in 370 patients who had undergone phacoemulsification with posterior chamber toric IOL insertion (front-toric IOL, back-toric IOL or bi-toric IOL). Subjects were divided into 2 groups; subjects who had no history of corneal disease with corneal astigmatism more than 1.00 diopters (D) (G1) and subjects who received previous PKP with all corneal sutures removed and had corneal astigmatism more than 1.25 D (G2). Preoperatively intended target from SRK/T was evaluated. Refractive astigmatism and its vector analysis (J0, J45), mean numerical error (MNE) and mean absolute error (MAE) were assessed at least a month after cataract surgery.
RESULTS
Mean preoperative corneal astigmatisms were 2.2 D and 4.0 D in G1 and G2, respectively. There was significant reduction of mean postoperative refractive astigmatism to 0.89 D in G1 and to 2.33 D in G2. In G1, bi-toric IOL showed significantly more improved refractive astigmatism than back-toric IOL. In G2, no difference in refractive astigmatism according to toric IOL type was observed. While G2 showed no difference in MNE among toric IOLs, in G1, bi-toric IOL showed significant hyperopic shift compared to back-toric IOL. In both groups, there was no significant difference in MAE according to type of IOL. No postoperative complications were observed.
CONCLUSION
Our study suggests that all types of toric IOL are beneficial in correcting astigmatism of normal and post-PKP corneas. Noticeably, bi-toric IOL showed significantly better results in refractive astigmatism than back-toric IOL in normal cornea. However, bi-toric IOL showed a more hyperopic shift compared to back-toric IOL. Among post-PKP corneas, all types of toric IOL showed similar results.
Topics: Astigmatism; Corneal Topography; Female; Humans; Keratoplasty, Penetrating; Lens Implantation, Intraocular; Lenses, Intraocular; Male; Middle Aged; Optics and Photonics; Phacoemulsification; Pseudophakia; Refraction, Ocular; Retrospective Studies; Visual Acuity
PubMed: 32345260
DOI: 10.1186/s12886-020-01439-4 -
Investigative Ophthalmology & Visual... Dec 2014To assess longitudinal change in refractive, keratometric, and internal astigmatism in a sample of students from a population with a high prevalence of with-the-rule... (Comparative Study)
Comparative Study
PURPOSE
To assess longitudinal change in refractive, keratometric, and internal astigmatism in a sample of students from a population with a high prevalence of with-the-rule (WTR) astigmatism and to determine the optical origins of changes in refractive astigmatism.
METHODS
A retrospective analysis of longitudinal measurements of right eye refractive and keratometric astigmatism in Tohono O'odham Native American children was conducted. Changes in refractive and keratometric astigmatism per year were compared in a younger cohort (n = 1594, 3 to <11 years old) and an older cohort (n = 648, 11 to <19 years old). Data were analyzed in clinical notation (Cyl) and vector notation (J0, J45).
RESULTS
On average, refractive astigmatism (means: 1.19 diopters [D] Cyl, +0.54 J0, +0.03 J45) resulted primarily from WTR corneal astigmatism (means: +0.85 J0, -0.02 J45) and against-the-rule (ATR) internal astigmatism (means: -0.31 J0, +0.05 J45). Mean longitudinal changes in astigmatism were statistically significant (younger cohort -0.02 D/y Cyl; older cohort +0.06 D/y Cyl). In the younger cohort, astigmatism decreased with age in low and moderate astigmats (<3.00 D) and increased with age in high astigmats (≥3.00 D). In the older cohort, astigmatism increased with age across all levels of astigmatism. Longitudinal changes in keratometric and internal astigmatism were negatively correlated in both cohorts.
CONCLUSIONS
Cross-sectional data suggest the presence of a constant ATR contribution from internal astigmatism (0.60 D Cyl) that is close to the 0.50 D ATR constant reported by Javal and others. Highly astigmatic 3- to <11-year-old children and children older than age 11 years show a small (not clinically significant) increase in astigmatism with age. A negative correlation between changes in keratometric astigmatism and internal astigmatism suggests an active compensation that may contribute to the stability of astigmatism in Tohono O'odham children.
Topics: Adolescent; Arizona; Astigmatism; Child; Child, Preschool; Cross-Sectional Studies; Female; Follow-Up Studies; Humans; Indians, North American; Male; Prevalence; Refraction, Ocular; Retrospective Studies; Time Factors
PubMed: 25515577
DOI: 10.1167/iovs.14-13898 -
Eye & Contact Lens Jan 2011To estimate the proportion of potential soft contact lens wearers requiring an astigmatic correction and to estimate the proportion of astigmats who can be accommodated...
PURPOSE
To estimate the proportion of potential soft contact lens wearers requiring an astigmatic correction and to estimate the proportion of astigmats who can be accommodated with toric soft lenses of varying prescription range.
METHOD
A database of 11,624 spectacle prescriptions was used to calculate the prevalence of astigmatism for various thresholds (0.50-2.00 DC) by eye and by patient. The coverage of various prescription ranges was estimated using a subset of the database comprising those patients with at least 0.75 D of astigmatism in at least one eye (n = 5,444).
RESULTS
The prevalence of patients showing astigmatism of 0.75 and 1.00 D or greater in at least one eye was 47.4% and 31.8% and, in both eyes, 24.1% and 15.0%, respectively. The proportion of eyes showing astigmatism greater than or equal to 0.75, 1.00, 1.50, and 2.00 D was 35.7%, 23.4%, 10.8%, 5.6%, respectively. The prevalence of astigmatism of 0.75 D or greater was almost double in myopes compared with hyperopes: 31.7% vs. 15.7%. The prevalence of with-the-rule (WTR) astigmatism was higher than against-the-rule (32.9% vs. 29.1%); the proportion was also higher for WTR in eyes with astigmatism ≥0.75 D (15.3% vs. 14.5%). We estimate that approximately one third of potential contact lens wearers require astigmatic correction. A stock range of toric soft lenses in sphere powers +6.00 to -9.00 D, three cylinder powers, and 18 axes requires nearly 3,000 prescriptions and provides coverage for 90% of astigmats.
CONCLUSION
These findings provide an estimate of the proportion of soft contact lens patients requiring an astigmatic correction and some useful insights into the proportion of astigmats covered by toric soft lens stocks of varying range.
Topics: Adolescent; Adult; Aged; Astigmatism; Child; Contact Lenses, Hydrophilic; Equipment Design; Humans; Middle Aged; Myopia; Prescriptions; Prevalence; Prosthesis Fitting; Treatment Outcome; Young Adult
PubMed: 21178696
DOI: 10.1097/ICL.0b013e3182048fb9 -
Ophthalmic & Physiological Optics : the... Jul 2008Most astigmats have a similar level of astigmatism in each eye. However, there is controversy over whether the astigmatic axes in fellow eyes typically show direct or...
PURPOSE
Most astigmats have a similar level of astigmatism in each eye. However, there is controversy over whether the astigmatic axes in fellow eyes typically show direct or mirror symmetry. We carried out a statistical analysis designed to address this issue.
METHODS
The median absolute difference in the astigmatic axes of fellow eyes was calculated for a sample of 50 995 astigmats (subjects with at least 0.25 D of astigmatism in each eye). This was done, firstly, for a 'direct symmetry model' in which the difference in axis was calculated as |AxisR - AxisL| and secondly, for a 'mirror symmetry model' in which the difference in axis was calculated as |AxisR - (180 - AxisL)|.
RESULTS
Under the direct symmetry model, the median absolute difference in the axis of astigmatism between fellow eyes was 20 degrees. Under the mirror symmetry model, the median absolute difference in the axis of astigmatism between fellow eyes was significantly lower, at 10 degrees (p < 10e-100). Comparable results were found when the analysis was restricted to subjects with: lower levels of astigmatism (< or =1.00 D), higher levels of astigmatism (>1.00 D), against-the-rule astigmatism, with-the-rule astigmatism or oblique astigmatism (all p < 10e-100).
CONCLUSION
Our results show that mirror, rather than direct, symmetry is the norm.
Topics: Adolescent; Adult; Aged; Aging; Algorithms; Astigmatism; Child; Cornea; Female; Humans; Male; Middle Aged; Optometry; Refraction, Ocular
PubMed: 18565088
DOI: 10.1111/j.1475-1313.2008.00576.x -
European Journal of Ophthalmology Jul 2018To assess the surgically induced astigmatism with femtosecond laser-assisted and manual temporal clear corneal incisions and to evaluate the performance of a model for...
PURPOSE
To assess the surgically induced astigmatism with femtosecond laser-assisted and manual temporal clear corneal incisions and to evaluate the performance of a model for prediction of the surgically induced astigmatism based on the preoperative corneal astigmatism.
METHODS
Clinical data of 104 right eyes and 104 left eyes undergoing cataract surgery, 52 with manual incisions and 52 with femtosecond laser-assisted incisions in each eye group, were extracted and revised retrospectively. In all cases, manual incisions were 2.2 mm width and femtosecond incisions were 2.5 mm width, both at temporal location. A predictive model of the surgically induced astigmatism was obtained by means of simple linear regression analyses.
RESULTS
Mean surgically induced astigmatisms for right eyes were 0.14D@65 (manual) and 0.24D@92 (femtosecond) (p > 0.05) and for left eyes, 0.15D@101 (manual) and 0.19D@104 (femtosecond) (p > 0.05). The orthogonal components of the surgically induced astigmatism (X, Y) were significantly correlated (p < 0.05) with the preoperative orthogonal components of corneal astigmatism (X, Y) (r = -0.29 for X and r = -0.1 for Y). The preoperative astigmatism explained 8% of the variability of the X and 3% of the variability of Y. The postoperative corneal astigmatism prediction was not improved by the surgically induced astigmatism obtained from the model in comparison with the simple vector subtraction of the mean surgically induced astigmatism.
CONCLUSION
Temporal incisions induce similar astigmatism either for manual or for femtosecond procedures. This can be clinically negligible for being considered for toric intraocular lens calculation due to the great standard deviation in comparison with the mean. The usefulness of the prediction model should be confirmed in patients with high preoperative corneal astigmatism.
Topics: Aged; Astigmatism; Cornea; Corneal Diseases; Corneal Topography; Female; Humans; Laser Therapy; Lenses, Intraocular; Male; Middle Aged; Phacoemulsification; Postoperative Complications; Prognosis; Refraction, Ocular; Retrospective Studies
PubMed: 29973075
DOI: 10.1177/1120672117747017 -
The British Journal of Ophthalmology Dec 2009To assess astigmatism induced after phakic intraocular lens (Visian ICL, STAAR Surgical) implantation.
AIM
To assess astigmatism induced after phakic intraocular lens (Visian ICL, STAAR Surgical) implantation.
METHODS
Seventy-three eyes of 47 patients undergoing ICL implantation through a horizontal 3.0 mm clear corneal incision were retrospectively examined. The amount of corneal astigmatism before and 3 months after surgery using an automated keratometer (ARK-700A, Nidek) and corneal topography (ATRAS995, Carl Zeiss Meditec) were quantitatively investigated. The surgically induced astigmatism was assessed by vector analysis using the Holladay-Cravy-Koch formula.
RESULTS
The corneal astigmatism was significantly increased from 1.10 (0.51) dioptres (D) to 1.44 (0.57) D using the keratometer (Wilcoxon signed-rank test, p<0.001). It was also significantly increased from 1.16 (0.53) D to 1.45 (0.57) D using corneal topography (p<0.001). On the other hand, the manifest astigmatism was significantly decreased from 0.93 (0.60) D to 0.72 (0.58) D (p<0.001). The surgically induced astigmatism was 0.45 (0.26) D at an axis of 93.3 degrees using the keratometer and 0.49 (0.26) D at an axis of 98.0 degrees using corneal topography.
CONCLUSIONS
ICL implantation induces corneal astigmatism through a with-the-rule astigmatic shift of approximately 0.5 D, which was small but not negligible for candidates for refractive surgery.
Topics: Adolescent; Adult; Astigmatism; Corneal Topography; Female; Humans; Lens Implantation, Intraocular; Male; Middle Aged; Myopia; Retrospective Studies; Young Adult
PubMed: 19692357
DOI: 10.1136/bjo.2009.160044 -
Acta Ophthalmologica Aug 2021To compare the outcomes of femtosecond astigmatic keratotomy (FSAK) and manual astigmatic keratotomy (AK) in treatment of postkeratoplasty astigmatism. (Comparative Study)
Comparative Study
PURPOSE
To compare the outcomes of femtosecond astigmatic keratotomy (FSAK) and manual astigmatic keratotomy (AK) in treatment of postkeratoplasty astigmatism.
METHODS
A retrospective, comparative, pairwise-matched case series including 150 patients who underwent either FSAK (n = 75) or manual AK (n = 75) for the treatment of astigmatism (>3.00 D) following penetrating keratoplasty or deep anterior lamellar keratoplasty. Pairwise matching for baseline variables (age, visual acuity and astigmatism) was performed.
RESULTS
Mean age was 57.5 ± 16.0 years. The FSAK group had significantly better postoperative best-corrected visual acuity (BCVA) (p = 0.010), uncorrected visual acuity (UCVA) (p = 0.049), corneal astigmatism (p = 0.020) and manifest astigmatism (p < 0.001) compared with the manual AK group. Gain of ≥3 lines in BCVA (logMAR) was seen in five eyes (6.7%) and 21 eyes (28.0%) in manual AK and FSAK, respectively (p = 0.005). Alpins vector analysis showed lower (closer to 0) index of success (0.50 ± 0.24 and 0.79 ± 0.48, p < 0.001) and higher (closer to 1) correction index (0.94 ± 0.45 and 0.74 ± 0.55, p = 0.020) in FSAK compared with manual AK. Corneal and manifest astigmatism improved significantly in both groups, while BCVA and UCVA improved significantly in FSAK only. Repeat AK rate was 32% (24 eyes) in manual AK and 4% (three eyes) in FSAK (p < 0.001). Overcorrection-related re-suturing rate was 0% in manual AK and 8% (six eyes) in FSAK (p = 0.037). There was one microperforation (1.3%) in FSAK, and there were no occurrences of graft dehiscence, infectious keratitis or graft rejection.
CONCLUSIONS
Both manual AK and FSAK were safe and effective in reducing postkeratoplasty astigmatism. FSAK had superior visual and keratometric outcomes compared with manual AK.
Topics: Astigmatism; Cornea; Corneal Diseases; Corneal Topography; Female; Humans; Keratoplasty, Penetrating; Keratotomy, Radial; Lasers, Excimer; Male; Middle Aged; Postoperative Complications; Refraction, Ocular; Reoperation; Retrospective Studies; Treatment Outcome; Visual Acuity
PubMed: 33124121
DOI: 10.1111/aos.14653 -
Ophthalmology Aug 1997The purpose of the study is to evaluate the induced astigmatism after spherical photorefractive keratectomy on the Summit Omnimed (Summit Instruments, Waltham, MA) and...
PURPOSE
The purpose of the study is to evaluate the induced astigmatism after spherical photorefractive keratectomy on the Summit Omnimed (Summit Instruments, Waltham, MA) and the Nidek EC-5000 (Nidek Co. Ltd, Aichi, Japan) excimer lasers.
METHODS
A total of 4269 eyes of 3289 patients were treated with a 5-mm optical zone using the Summit Omnimed excimer laser and 1825 eyes of 1303 patients treated with the Nidek EC-5000 excimer laser. The final astigmatic refractive outcome was compared with the initial refraction by vector analysis (Alpin and Jaffe method).
RESULTS
Subjective astigmatic refraction for the Summit laser reduced from a mean of -0.39 diopter (D) +/- standard deviation (SD) 0.33 D (range, 0 to -2.50 D) to -0.33 D +/- SD 0.41 D (range, 0 to -3.00 D). Surgically induced astigmatism (SIA) had a mean of 0.42 +/- SD 0.34 D (range, 0 to 2.89 D). Mean SIA increased with increasing preoperative astigmatism by 0.60 D SIA for every 1.00 D of preoperative cylinder. For the Nidek laser, subjective astigmatic refraction changed from a mean of -0.18 D +/- SD 0.21 D (range, 0 to -1.25 D) to -0.30 D +/- SD 0.33 D (range, 0 to -3.00 D). Surgically induced astigmatism had a mean of -0.32 D +/- SD 0.29 (range, 0 to 3.05 D). Mean SIA increased with increasing preoperative astigmatism by 0.47 D SIA for every 1.00 D of preoperative cylinder.
CONCLUSIONS
The authors show that spherical photorefractive keratectomy corrections can induce significant astigmatic change, particularly if a large amount of preoperative astigmatism is present.
Topics: Astigmatism; Humans; Laser Therapy; Lasers, Excimer; Photorefractive Keratectomy; Postoperative Period; Refraction, Ocular; Reoperation
PubMed: 9261320
DOI: 10.1016/s0161-6420(97)30141-9 -
Journal of Cataract and Refractive... Jun 1999To study the effect of astigmatism on multifocal intraocular lens (MIOL) function.
PURPOSE
To study the effect of astigmatism on multifocal intraocular lens (MIOL) function.
SETTING
Laser Laboratory, Department of Electronics, Electrotechnics and Informatics, University of Trieste, Italy.
METHODS
Using an experimental optical system, this study compared the division of a laser beam in the focal spots of 1 monofocal IOL (Pharmacia 722A), 1 bifocal IOL (Pharmacia 811E), and 2 MIOLs (AMO Array MPC25NB and Domilens Progress 1). The model consists of a helium-neon laser and an optical system: a triangular optical bench with a precision collimator, a micropositionable immersion stage to support the IOL, and a digital image-processing system. Astigmatism was induced by interposing a +1.0 diopter (D) cylinder lens between the IOL and the television camera. Astigmatism was corrected by adding a -1.0 D cylinder lens in front of the IOL on the same axis.
RESULTS
Astigmatism creates pairs of focal lines, 1 for each focal spot in the IOL. In the multifocal IOL, the posterior focal line of the nearest focus interfered with the anterior line of the next focus. Correcting the astigmatism led to a significant reduction (mean 20%) in light intensity.
CONCLUSIONS
Astigmatically neutral surgery or surgical correction of pre-existing astigmatism is essential in MIOL implantation to minimize the decrease in contrast sensitivity.
Topics: Astigmatism; Contrast Sensitivity; Humans; Lenses, Intraocular; Models, Anatomic
PubMed: 10374161
DOI: 10.1016/s0886-3350(99)00029-2