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Eye & Contact Lens Feb 2021Fitting philosophies for toric orthokeratology are based on elevation or corneal astigmatism, but it is unclear which is more effective. The purpose of this analysis was...
OBJECTIVES
Fitting philosophies for toric orthokeratology are based on elevation or corneal astigmatism, but it is unclear which is more effective. The purpose of this analysis was to further understand corneal shape and the relationship between peripheral elevation and central astigmatism in moderate-to-high astigmats.
METHODS
Corneal tomography was measured three times on the right eyes of 25 moderate-to-high refractive myopic astigmatic adults. Corneal astigmatism and elevation were calculated at 4-, 6-, and 8-mm chords. Subjects were fitted with toric orthokeratology lenses following the manufacturer's guidelines based on elevation. Twenty subjects completed 10 days of wear. A masked examiner assessed movement and centration via slitlamp videos and quantified treatment zone and decentration from tangential power difference tomography maps. Correlations between variables were assessed.
RESULTS
Average corneal astigmatism was 2.20±0.70 DC and peripheral elevation was 50.88±18.92 μm and they were strongly correlated (4 mm R2=0.96, 6 mm R2=0.92, 8 mm R2=0.86, all P<0.001). Each diopter of astigmatism equated to 25 μm of elevation at an 8-mm chord. Via slitlamp, average treatment zone area was 12.73±4.62 mm2 and 13 lenses decentered. From tomography, average treatment zone area was 7.16±2.56 mm2 and 17 were decentered. Tomography treatment zone area was negatively correlated with central corneal astigmatism (R2=0.60) and elevation at an 8-mm chord (R2=0.64, both P<0.001).
CONCLUSIONS
For tomography images, central corneal astigmatism was highly correlated with peripheral elevation and may be a more expedient measure for clinical use. Treatment area decreased as corneal astigmatism and elevation increased.
Topics: Adult; Astigmatism; Cornea; Corneal Topography; Humans; Lenses, Intraocular; Myopia; Refraction, Ocular
PubMed: 32568927
DOI: 10.1097/ICL.0000000000000721 -
Optometry and Vision Science : Official... Apr 2005Astigmatism is the most common ametropia found in humans and is often associated with large spherical ametropias. However, little is known about the etiology of...
PURPOSE
Astigmatism is the most common ametropia found in humans and is often associated with large spherical ametropias. However, little is known about the etiology of astigmatism or the reason(s) for the association between spherical and astigmatic refractive errors. This study examines the frequency and characteristics of astigmatism in infant monkeys that developed axial ametropias as a result of altered early visual experience.
METHODS
Data were obtained from 112 rhesus monkeys that experienced a variety of lens-rearing regimens that were intended to alter the normal course of emmetropization. These visual manipulations included form deprivation (n = 13); optically imposed defocus (n = 48); and continuous ambient lighting with (n = 6) or without optically imposed defocus (n = 6). In addition, data from 19 control monkeys and 39 infants reared with an optically imposed astigmatism were used for comparison purposes. The lens-rearing period started at approximately 3 weeks of age and ended by 4 to 5 months of age. Refractive development for all monkeys was assessed periodically throughout the treatment and subsequent recovery periods by retinoscopy, keratometry, and A-scan ultrasonography.
RESULTS
In contrast to control monkeys, the monkeys that had experimentally induced axial ametropias frequently developed significant amounts of astigmatism (mean refractive astigmatism = 0.37 +/- 0.33 D [control] vs. 1.24 +/- 0.81 D [treated]; two-sample t-test, p < 0.0001), especially when their eyes exhibited relative hyperopic shifts in refractive error. The astigmatism was corneal in origin (Pearson's r; p < 0.001 for total astigmatism and the JO and J45 components), and the axes of the astigmatism were typically oblique and bilaterally mirror symmetric. Interestingly, the astigmatism was not permanent; the majority of the monkeys exhibited substantial reductions in the amount of astigmatism at or near the end of the lens-rearing procedures.
CONCLUSIONS
In infant monkeys, visual conditions that alter axial growth can also alter corneal shape. Similarities between the astigmatic errors in our monkeys and some astigmatic errors in humans suggest that vision-dependent changes in eye growth may contribute to astigmatism in humans.
Topics: Animals; Astigmatism; Cornea; Eye; Eyeglasses; Hyperopia; Macaca mulatta; Myopia; Refraction, Ocular
PubMed: 15829845
DOI: 10.1097/01.opx.0000159357.61498.6b -
Scientific Reports Jan 2021To determine the distribution of ocular residual astigmatism (ORA) in astigmatic eyes and the influence on the anterior corneal (ACA) and refractive astigmatism (RA). A...
To determine the distribution of ocular residual astigmatism (ORA) in astigmatic eyes and the influence on the anterior corneal (ACA) and refractive astigmatism (RA). A total of 165 children met the inclusion criteria. Right eyes' data were analyzed. Using Thibos vector analysis to calculate ORA. Spearman correlation analysis was used to obtain the correlation between the magnitude of ORA, ACA and RA. The median magnitude of ORA in astigmatic eyes was 0.57 D, with interquartile range was 0.42 D. And they were main against-the-rule (57.6-75.8%) and oblique astigmatism (13.9-34.5%) ORA. The ORA in 140 eyes (84.8%) acted as an offset to ACA, meanwhile, 25 eyes (15.2%) superimposed it. About 98% (97.9-98.4%) against-the-rule and 75% (73.9-82.5%) oblique ORA counteracted ACA, nevertheless, all with-the-rule ORA had a superimposed effect on ACA. For with-the-rule ACA, about 86% (85.4-85.9%) ORA worked to offset it. There was statistically correlations between ORA and ACA (r = 0.17, P = 0.03), ORA and RA (r = - 0.27, P = 0.001). The magnitude of ocular residual astigmatism was relatively small in children's astigmatic eyes. Both against-the-rule and oblique ORA can counteract with-the-rule ACA.
Topics: Astigmatism; Child; Child, Preschool; China; Corneal Topography; Cross-Sectional Studies; Diagnostic Techniques, Ophthalmological; Female; Humans; Male; Refraction, Ocular; Retinoscopy
PubMed: 33441809
DOI: 10.1038/s41598-020-80106-6 -
Ophthalmology Clinics of North America Sep 2003Soft contact lens correction for astigmatism has made significant advances over the last 20 years. Soft toric tinted lenses, disposables lenses, and bifocal lenses are... (Review)
Review
Soft contact lens correction for astigmatism has made significant advances over the last 20 years. Soft toric tinted lenses, disposables lenses, and bifocal lenses are now available at lower costs with greater reproducibility, enhanced parameters, and better comfort. Because of these innovations and significant design changes, a greater percentage of astigmatic patients are being treated with soft toric lenses than before.
Topics: Astigmatism; Contact Lenses, Hydrophilic; Equipment Design; Humans; Prosthesis Fitting
PubMed: 14564758
DOI: 10.1016/s0896-1549(03)00046-4 -
Journal of Cataract and Refractive... May 2001A 42-year-old woman developed significant astigmatism after localized thermal injury to the cornea during a cosmetic eyelid procedure. The induced astigmatism regressed...
A 42-year-old woman developed significant astigmatism after localized thermal injury to the cornea during a cosmetic eyelid procedure. The induced astigmatism regressed substantially over the ensuing months. One year after the injury, astigmatic keratotomy (AK) was performed, further reducing the astigmatism and improving the patient's subjective vision. Patients with induced astigmatism from thermal corneal injury should be monitored for regression. When refractive stability is achieved, AK can reduce the remaining astigmatism. This case reviews concepts that apply to refractive thermal keratoplasty.
Topics: Adult; Astigmatism; Blepharoplasty; Cornea; Corneal Topography; Electrocoagulation; Female; Humans; Keratotomy, Radial; Visual Acuity
PubMed: 11377913
DOI: 10.1016/s0886-3350(00)00758-6 -
Journal of Cataract and Refractive... Jan 1989It is increasingly possible for the cataract surgeon to control astigmatism. Based on a review of 4,000 consecutive patients, three categories of astigmatism and... (Review)
Review
It is increasingly possible for the cataract surgeon to control astigmatism. Based on a review of 4,000 consecutive patients, three categories of astigmatism and cataract patients are identified. A specific approach to astigmatism control for each category is discussed. Preliminary results on the use of astigmatic keratotomy in conjunction with cataract surgery are presented.
Topics: Aged; Astigmatism; Cataract Extraction; Female; Humans; Keratotomy, Radial; Male; Middle Aged; Refraction, Ocular; Retrospective Studies; Suture Techniques
PubMed: 2646429
DOI: 10.1016/s0886-3350(89)80139-7 -
International Ophthalmology Oct 2008To determine the astigmatism outcomes after cataract surgery performed using superonasal and superotemporal clear corneal incisions.
PURPOSE
To determine the astigmatism outcomes after cataract surgery performed using superonasal and superotemporal clear corneal incisions.
SETTING
Department of Ophthalmology, Kartal Training and Research Hospital, Istanbul, Turkey.
METHODS
This prospective study includes consecutive 45 eyes of 34 patients having phacoemulsification with implantation of foldable acrylic intraocular lens through a corneal tunnel incision between January and April 2004. The right eye always had a superotemporal incision while the left eye a superonasal incision. Astigmatism was measured by keratometry readings before surgery and 3rd, 15th, and 45th days postoperatively. The surgically induced astigmatism (SIA) was calculated by the vector analysis using the Holladay-Cravy-Koch method at 3rd day, 2nd and 6th weeks postoperatively.
RESULTS
The mean preoperative astigmatism was 0.74 +/- 0.45 diopter (D) in the temporal incision group and 0.69 +/- 0.39 D in the nasal incision group. Fifty-eight percent of eyes had against-the-rule (ATR) astigmatism, 26% had with-the-rule (WTR) astigmatism, and 16% were astigmatically neutral. At 6 weeks, 46% of eyes had ATR astigmatism and 35% had WTR astigmatism. The mean total astigmatism was lower in the temporal incision group than in the nasal incision group at all successive examinations postoperatively. Although the total astigmatism decreased at 6 weeks in both groups, temporal incisions yielded less total and surgically induced astigmatism (P < .05).
CONCLUSIONS
Cataract surgery using superotemporal incision induced significantly less SIA in the early postoperative period.
Topics: Acrylic Resins; Aged; Aged, 80 and over; Astigmatism; Cornea; Female; Humans; Lens Implantation, Intraocular; Lenses, Intraocular; Male; Microsurgery; Middle Aged; Phacoemulsification; Postoperative Complications; Prospective Studies
PubMed: 17901926
DOI: 10.1007/s10792-007-9141-y -
Vision Research 1985The orientation preferences of 70 infants aged 7 to 53 weeks with significant astigmatism [1.0 or more diopters (D)] were measured using a preferential looking procedure...
The orientation preferences of 70 infants aged 7 to 53 weeks with significant astigmatism [1.0 or more diopters (D)] were measured using a preferential looking procedure with paired gratings. The preference data show the consequences of the blurring effects of astigmatism when these are not compensatable by accommodation. Data from infant astigmats tested with optical correction look like those of nonastigmats. We have found no evidence for the development of meridional amblyopia during the first year of life.
Topics: Accommodation, Ocular; Amblyopia; Astigmatism; Fixation, Ocular; Humans; Infant; Pattern Recognition, Visual; Rotation; Visual Acuity
PubMed: 4072007
DOI: 10.1016/0042-6989(85)90042-2 -
Science (New York, N.Y.) Oct 1978Photorefraction of a sample of 93 infants of ages 1 day to 12 months showed that 63 percent of the subjects had astigmatism of 0.75 diopter or greater, and 12 percent...
Photorefraction of a sample of 93 infants of ages 1 day to 12 months showed that 63 percent of the subjects had astigmatism of 0.75 diopter or greater, and 12 percent greater than 2 diopters. Seventy percent of these astigmatisms were in the horizontal-vertical meridians. By comparison, only 8 percent of a sample of 26 adults tested by the same method showed astigmatism (all 0.75 to 1 diopter). The high incidence of infant astigmatism has implications for critical periods in human visual development and for infant acuity.
Topics: Adult; Age Factors; Astigmatism; Humans; Infant; Infant, Newborn; Infant, Newborn, Diseases; Photography; Refraction, Ocular
PubMed: 694540
DOI: 10.1126/science.694540 -
BMC Ophthalmology Aug 2012Cataracts are a common and significant cause of visual impairment globally. We aimed to evaluate uncorrected distance visual acuity (UDVA) as an outcome in treating... (Review)
Review
BACKGROUND
Cataracts are a common and significant cause of visual impairment globally. We aimed to evaluate uncorrected distance visual acuity (UDVA) as an outcome in treating astigmatic cataract patients to assist clinicians or ophthalmologists in their decision making process regarding available interventions.
METHODS
Medline, Embase and Evidence Based Reviews were systematically reviewed to identify relevant studies reporting changes in UDVA, UIVA and UNVA after cataract surgery in presbyopic patients. Strict inclusion/exclusion criteria were used to exclude any non-relevant studies. Relevant outcomes (UDVA, UIVA and UNVA) were identified from the studies retrieved through the systematic review process.
RESULTS
The systematic review identified 11 studies which reported UCVA. All 11 studies reported UDVA. Four brands of toric intraocular lenses (IOLs) were reported in these studies. All studies identified in the literature search reported improvements in UDVA following surgical implant of a toric IOL. The largest improvements in VA were reported using the Human Optics MicroSil toric IOL (0.74 LogMAR, UDVA) and the smallest improvements were also reported using the Human Optics MicroSil toric IOL (0.23 LogMAR, UDVA) in a different study.
CONCLUSIONS
The results of this systematic review showed the aggregate of studies reporting a beneficial increase in UDVA with the use of toric IOLs in cataract patients with astigmatism.
Topics: Astigmatism; Cataract; Cataract Extraction; Humans; Lenses, Intraocular; Refraction, Ocular; Visual Acuity
PubMed: 22894651
DOI: 10.1186/1471-2415-12-41