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At least 19 recordsLinked to original sources

PubMed2000

[The analysis of the axises of corneal astigmatism and total astigmatism in astigmatic patients].

PURPOSE: The axial amount and the relationship between the axises of corneal astigmatism and total astigmatism were statistically analyzed in ametropic patients, for the purpose of selecting the refractive correction, the base curve of contact lens, the axis of astigmatic contact lens, and providing the reference of operational amount of ecimer laser keratoplasty. METHODS: The refractive state and the corneal curvature of ametropic patients were measured and consecutvely repeated 3 times in the same eye at the same state with the same autorefractometer in 107 cases. The detected axises of total astigmatism and corneal astigmatism were statistically analyzed through the computerized recording. RESULTS: The mean angle between the axis of corneal astigmatism and the axis of total astigmatism was 5.73 degrees +/- 3.97 degrees in myopic patients, 3.13 degrees +/- 2.49 degrees in mixture astigmatism patients and 6.35 degrees +/- 4.20 degrees in hyperopic patients. CONCLUSION: The angle between the axis of corneal astigmatism and the axis of total astigmatism in the refractive state was mainly caused by the difference of the axises of surface astigmatism of lens and cornea.

Adolescent↗

PubMed2003

Internal astigmatism and its correlation to corneal and refractive astigmatism.

OBJECTIVE: To evaluate the internal astigmatism and its relationship to corneal and refractive astigmatism in a refractive surgery patient population. METHOD: Patients who underwent pre-operative evaluation for Laser in situ Keratomileusis (LASIK) at Excimer Laser Clinic, Siriraj Hospital, Mahidol University were included. Pre-operative data including age, manifest refraction and corneal topography obtained by Orbscan Corneal Topography were performed. Regression Analysis was done to find the correlation between refractive and corneal astigmatism. RESULTS: 110 patients (220 eyes: 110 right eyes and 110 left eyes) were included. The mean age was 31.14 +/- 7.00 year (range 19 to 48 years). The mean astigmatism measured by manifest refraction (refractive astigmatism) was 0.76 +/- 0.72 diopters (range 0 to 3.50 diopters). The mean astigmatism measured by Orbscan Corneal Topographer (corneal astigmatism) was 1.38 +/- 0.72 diopters (range 0.20 to 5.30 diopters). The mean difference in magnitude of refractive and corneal astigmatism (internal astigmatism) was 0.62 +/- 0.67 diopters (range 0 to 3.00 diopters) and 74 per cent were within +/- 1.00 diopters difference. The mean difference in axis of astigmatism was 0.95 +/- 23 degree (range 0 to 85 degree) and 79.6 per cent were within +/- 15 degree difference. There was low correlation between corneal and internal astigmatism (R2 = 0.12, p < 0.05), also low correlation between refractive and internal astigmatism (R2 = 0.27, p < 0.05). There was a statistically significant difference between magnitude of corneal and refractive astigmatism (p < 0.05) but no difference in the axis of astigmatism (p = 0.55). CONCLUSION: This study demonstrated non-mutual agreement between refractive and corneal astigmatism (presence of internal astigmatism). High value (> 1.00 diopter) of internal astigmatism was demonstrated in 1/3 of the cases. Kerato-refractive surgery that attempts to correct refractive astigmatism at corneal plane may effect long-term evaluation of the astigmatism.

Adult↗

PubMed1996

Astigmatic keratotomy combined with myopic keratomileusis in situ for compound myopic astigmatism.

PURPOSE: Myopic keratomileusis in situ by an automated microkeratome corrects myopia but not astigmatism, which is traditionally corrected by astigmatic keratotomy months after keratomileusis. We developed a technique for simultaneously correcting astigmatism and severe myopia, and examined its effectiveness in a retrospective case-control study. METHODS: Thirty-four eyes (23 patients) underwent myopic keratomileusis in situ combined with one or two arcuate keratotomy incisions performed after the refractive cut, in the bed of the primary keratectomy flap. The myopic keratomileusis control group consisted of 34 matched eyes (30 patients) undergoing keratomileusis without astigmatic keratotomy. The astigmatic control group consisted of 117 unmatched eyes (85 patients) undergoing astigmatic keratotomy combined with radial keratotomy. RESULTS: Mean refractive astigmatism in the study group decreased from 2.4 diopters (range, 1.0 to 4.0 diopters) preoperatively to 1.7 diopters (range, 1.0 to 4.0 diopters) at three months postoperatively, and increased by 0.4 diopter in the myopic keratomileusis control group at three months postoperatively (P < .005). Eighteen of 27 eyes in the study group showed decreased refractive astigmatism compared with ten of 34 eyes in the myopic keratomileusis control group (P < .0001). Combining astigmatic keratotomy with myopic keratomileusis produced 0.2 +/- 0.9 diopter less astigmatic correction than that expected from the astigmatic control group. One of 27 eyes lost two or more lines of best spectacle-corrected visual acuity at the three-month postoperative visit. No eye lost two or more lines of best spectacle-corrected visual acuity at postoperative month 6. CONCLUSION: Eyes with substantial preoperative refractive astigmatism that undergo myopic keratomileusis in situ may benefit from simultaneous astigmatic keratotomy to reduce residual post-operative refractive astigmatism.

Adult↗

PubMed2003

Limbal relaxing incisions for primary mixed astigmatism and mixed astigmatism after cataract surgery.

PURPOSE: To evaluate the effect of limbal relaxing incisions (LRIs) in the treatment of primary mixed astigmatism and mixed astigmatism after cataract surgery. SETTING: Department of Ophthalmology, Inönü University, Malatya, Turkey. METHODS: Limbal relaxing incisions were performed to correct astigmatism in 37 eyes of 26 patients with mixed astigmatism. Twenty-four eyes had primary astigmatism, and 13 eyes had astigmatism after cataract surgery. The length, number, and depth of the incisions were determined using the Gills and Gayton nomogram. The manifest refractive astigmatism was measured preoperatively and 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively. Surgically induced astigmatism using the vector method, preoperative and postoperative uncorrected visual acuity (UCVA), and best spectacle-corrected visual acuity (BSCVA) were evaluated. Follow-up was at least 6 months in all cases. RESULTS: The mean preoperative and postoperative refractive astigmatism was 3.31 diopters (D) +/- 1.50 (SD) and 1.59 +/- 1.28 D, respectively (P <.001). The mean absolute change in refractive astigmatism was 1.72 +/- 0.81 D. No patient lost lines of UCVA or BSCVA. The safety index was 1.21 and the efficacy index, 0.88. The mean preoperative and postoperative UCVA was 0.29 +/- 0.22 and 0.54 +/- 0.31, respectively (P =.0001) and the mean BSCVA, 0.61 +/- 0.30 and 0.74 +/- 0.30, respectively (P =.0001). The mean vectorial magnitude was 2.32 +/- 1.36 D at the last follow-up. There were no serious postoperative complications. CONCLUSION: Limbal relaxing incisions are a simple, safe, and effective method to correct primary mixed astigmatism and mixed astigmatism after cataract surgery.

Adolescent↗

PubMed1995

Prospective evaluation of surgically induced astigmatism and astigmatic keratotomy effects of various self-sealing small incisions.

The refractive effects of self-sealing clear corneal and corneoscleral tunnel incisions, 3.5 mm and 5.2 mm, in cataract surgery were studied prospectively by automatic keratometric evaluation at day one postoperatively and weeks one, three, and six. Keratometric readings were converted to polar values. The amount of surgically induced astigmatism was calculated for each incision and mean postoperative keratometric astigmatism was estimated for patients with preoperative against-the-rule and with-the-rule astigmatism to evaluate the astigmatic keratotomy effects of the incisions. The corneoscleral incisions were almost astigmatically neutral, with no major difference between the 3.5 mm and the 5.2 mm incisions after six weeks. The 5.2 mm frown incisions were less stable than the straight corneoscleral incisions. Clear corneal incisions resulted in a considerable amount of induced astigmatism; there was more with the 5.2 mm incisions than with the 3.5 mm incisions. Temporal incisions resulted in a with-the-rule induced change and superior incisions, an against-the-rule induced change. The refractive effect of the clear corneal incisions did not change significantly from day one to week six. The astigmatic keratotomy effects of these incisions were therefore more useful and predictable. Preoperative against-the-rule astigmatism was reduced significantly by temporally placed clear corneal incisions and preoperative with-the-rule astigmatism, by superiorly placed clear corneal incisions. If one considers the preoperative astigmatism when selecting incision type and location for small incision cataract surgery, one can minimize postoperative keratometric astigmatism.

Astigmatism↗

PubMed2001

[Astigmatism-oriented perforating keratoplasty. A possibility for minimizing postoperative astigmatism?].

BACKGROUND: This pilot study examined whether astigmatism of donor corneas can be evaluated postmortem, and whether there is an effect on the astigmatism following keratoplasty. METHODS: The corneoscleral rims of donors were marked after measurement by a hand keratometer in the 12 o'clock position. We examined 38 patients after penetrating keratoplasty and divided them into three groups. The 12 o'clock position of the donor cornea was fixed in the same position as the recipient (group A, n = 12), or the donor corneas were transplanted with the axis in opposition to the axis of the recipient (group B, n = 12) or in the same orientation (group C, n = 14). Development of postoperative astigmatism was compared with controls (group D, n = 40). RESULTS: In group B we found a new orientation of the astigmatism axis within 2-4 months; in group C the axis maintained the original orientation of the recipient. Mean postoperative astigmatism was 3.5 +/- 1.5 dpt in group A, 2.1 +/- 1.3 dpt in group B, 5.8 +/- 1.6 dpt in group C, and 3.4 +/- 1.5 dpt in group D. After suture removal the axis orientation persisted in all groups. CONCLUSION: This study shows the possibility of evaluating corneal astigmatism in donor eyes. The astigmatism of the donor cornea itself directly influences the postoperative axis of astigmatism in recipient eyes. Astigmatism after corneal grafting can be reduced by orienting the donor astigmatism against the axis of the recipient.

Adult↗

PubMed2002

LASIK correction of spherical hyperopia, hyperopic astigmatism, and mixed astigmatism with the LADARVision excimer laser system.

OBJECTIVE: To assess the safety and effectiveness of the LADARVision active tracking narrow beam excimer laser system (Alcon Surgical, Orlando, FL) using laser in situ keratomileusis (LASIK) for correction of spherical hyperopia, hyperopic astigmatism, and mixed astigmatism. DESIGN: A multicenter, prospective non-randomized (self-controlled) comparative trial. PARTICIPANTS: A total of 360 eyes, including 152 spherical hyperopic, 143 hyperopic astigmatic, and 65 mixed astigmatic, were treated for up to +6.00-diopter (D) sphere with up to -6.00-D cylinder. INTERVENTION: Treatments were performed at six sites in the United States using a 6-mm optic zone with a 1.5-mm peripheral blend zone for a maximum ablation zone diameter of 9 mm. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), manifest refraction, vector analysis, best spectacle-corrected visual acuity (BSCVA), complications and adverse reactions, subjective symptoms, and patient satisfaction. RESULTS: Six and 12 months of follow-up, respectively, were available on 143 and 117 spherical hyperopic eyes, 124 and 74 hyperopic astigmatic eyes, and 57 and 38 mixed astigmatic eyes, respectively. For spherical hyperopes at 6 and 12 months, UCVA was 20/40 or better in 93.4% and 93.9% of eyes, respectively. The manifest refraction spherical equivalent (MRSE) was within 0.50 D of intended in 65.0% and 74.1% of eyes, respectively, and within 1.00 D in 87.4% and 91.4%, respectively. Refractive stability was demonstrated in 94.2% or more of eyes between the intervals of 1 to 3 months and 3 to 6 months and in 95.3% or more of eyes to 12 months. A loss of two lines of BSCVA occurred in 3.5% and 3.4%, respectively, and no eyes lost more than two lines. For hyperopic astigmats at 6 and 12 months, UCVA was 20/40 or better in 90.9% and 93.8% of eyes, respectively. The MRSE was within 0.50 D of intended in 60.5% and 73.0% of eyes, respectively, and within 1.00 D in 88.7% and 89.2% of eyes, respectively. Refractive stability was demonstrated in 96.5% or more of eyes, respectively, between the intervals of 1 to 3 months and 3 to 6 months and 95.5% or more to 12 months. A loss of two lines of BSCVA occurred in 5.8% and 1.4% of eyes, respectively, and no eyes lost more than two lines. For mixed astigmats at 6 and 12 months, UCVA was 20/40 or better in 92.6% and 94.4% of eyes, respectively. The MRSE was within 0.50 D of intended in 64.9% and 73.7% of eyes, respectively, and within 1.00 D in 87.7% and 94.7% of eyes, respectively. Refractive stability was demonstrated in 100% of eyes between the intervals of 1 to 3 months and 3 to 6 months and in 97.0% or more to 12 months. A loss of two lines of BSCVA occurred in 1.9% and 0.0% of eyes, respectively, and no eyes lost more than two lines. CONCLUSIONS: The data support safety and effectiveness of the LASIK correction of spherical hyperopia, hyperopic astigmatism, and mixed astigmatism with the LADARVision system.

Adult↗

PubMed2026

Astigmatic vector outcomes after FS-LASIK versus SMILE for high myopic astigmatism: a single-center retrospective comparative cohort study without cyclotorsion compensation.

PURPOSE: To compare astigmatic correction vector outcomes between femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small-incision lenticule extraction (SMILE, also termed Keratorefractive Lenticule Extraction, KLEx) without intraoperative cyclotorsion compensation in patients with high myopic astigmatism (- 2.00 to - 3.75 D), and to clarify procedure-specific correction tendencies under this non-standardized alignment protocol. METHODS: This single-center retrospective comparative cohort study enrolled 155 eyes (one eye randomly selected per patient) that underwent FS-LASIK (80 eyes) or SMILE/KLEx (75 eyes) for high myopic astigmatism correction from January 2023 to July 2024 in Beijing Fenglian Jiayue Lige Clinic. Intraoperative cyclotorsion compensation was intentionally disabled to isolate inherent procedural astigmatism correction characteristics. Standardized Alpins vectorial analysis was performed at 3 months and 12 months postoperatively. PRIMARY ENDPOINT: 12-month Alpins correction index (CI). Multivariable propensity score adjustment was applied to mitigate confounding by clinical treatment selection bias. Statistical multiplicity control was implemented for secondary vector and visual outcomes. RESULTS: Baseline demographic, refractive, corneal and ocular biometric parameters were balanced between groups after propensity matching. No statistically significant intergroup differences were detected in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), residual cylinder, safety index or efficacy index at 3 and 12 months (all P > 0.05). Under the non-cyclotorsion-compensated protocol, significant intergroup differences were identified in the magnitude of surgically induced astigmatism (SIA), correction index (CI), and magnitude error (ME) at both follow-up timepoints (all P < 0.0001). Target induced astigmatism (TIA), difference vector (DV), index of success (IOS), and angle error (AE) magnitudes were comparable between groups (all P > 0.05). The vector mean axis of DV differed significantly between groups at 3 and 12 months (Watson-Williams circular test, all P < 0.0001). No reoperations were documented in clinic medical records for either cohort. No standardized dry eye questionnaires, tear film testing or corneal nerve density metrics were collected to quantify dry eye adverse events; only unstructured clinical notes were reviewed for complication screening. CONCLUSIONS: Under surgical alignment without cyclotorsion compensation, FS-LASIK and SMILE/KLEx both yielded acceptable visual and refractive safety/efficacy for high myopic astigmatism (- 2.00 to - 3.75 D) at 1-year follow-up, but demonstrated divergent astigmatism correction tendencies: FS-LASIK exhibited relative astigmatism overcorrection (vector mean DV: - 0.35 ± 0.43 D × 91°, CI > 1), while SMILE/KLEx showed relative undercorrection (vector mean DV: - 0.21 ± 0.53 D × 12°, CI < 1). These correction biases are specific to the study's manual limbal alignment protocol without cyclotorsion tracking and cannot be generalized to modern optimized surgical platforms equipped with automated cyclotorsion compensation. Residual refractive errors across both groups are likely multifactorial, including differential corneal stromal healing responses, divergent femtosecond/excimer laser tissue modification mechanisms, and uncorrected intraoperative ocular cyclotorsion.

Humans↗

PubMed2000

Developmental compensation of imposed astigmatism is not initiated by astigmatic accommodation in chickens.

PURPOSE: It is not clear whether emmetropization is confined to spherical refractive errors, or whether astiqmatic errors are also corrected via visual feedback. Experimental results from the animal model of the chicken are equivocal since compensation of imposed astimatic defocus was found in some but not all studies. Astigmatism could only be compensated by changes in the geometry of the cornea or lens. One has tested whether astigmatic spectacle lenses induce astigmatic accommodation as a possible first step of long-lasting compensation. METHODS: Thirty-five chickens were treated with cylinder lenses (+3/0D or -3/0D) for 5 h. Refractions were determined at 1.38 m distance without cycloplegia in hand-held chicks before attaching the lenses, with the lenses on (0 h), and after 3 and 5 h, and after removal of the lenses. Spheres (S), cylinders (C) and axes (A) were determined using infrared photoretinocopy in three axes (the 'PowerRefractor', equipped with a 135 mm lens). RESULTS: (1) The performance of the 'PowerRefractor' was tested in the chickens with trial lenses and gave correct refractions. (2) Astigmatic trial lenses induced refractive errors as expected from their powers in the case of +3/0D lenses: (S) +3.26 +/- 0.93D, (C) -3.45 +/- 0.87D). In the case of -3/0D lenses, slightly more hyperopic spheres were induced (refractions (S) +4.5 +/- 0.48D) but the cylinders were still as expected (-3.25 +/- 0.49D). The axes of astigmatism were correctly reproduced, since rotating the lenses changed the axes of the induced cylinders as expected. (3) Neither after 3 nor after 5 h of lens wear were there significant changes in the axes or the magnitude of astigmatism. Directly after removal of the lens, the refractions did not differ from their start-up values (with +3/0D lenses: (S) +3.31 +/- 1.05D vs. +3.22 +/- 0.76D, (C) -1.19 +/- 1.77D vs. -0.65 +/- 0.94D, (A) 96 +/- 49 vs. 113 +/- 45 deg; with -3/0D lenses: (S) 2.63 +/- 1.12D vs. 2.97 +/- 0.94D, (C) -1.11 +/- 1.15D vs. -0.53 +/- 0.56D, (A) 78 +/- 24 vs. 131 +/- 35 deg). CONCLUSIONS: The most intuitive mechanism for compensation of astigmatic refractive errors, astigmatic accommodation, could not be demonstrated in chickens. In light of this finding, it seems unlikely that a visually controlled mechanism is operating during development to reduced astigmatism by changing corneal or lenticular growth.

Accommodation, Ocular↗

PubMed1990

Astigmatic keratotomy to correct preexisting astigmatism in cataract patients.

We evaluated three general strategies for dealing with astigmatism control following phacoemulsification with posterior chamber intraocular lens surgery: (1) a neutral wound closure to minimize surgically induced cylinder; (2) wound revision techniques to minimize residual postoperative cylinder; (3) astigmatic keratotomy incisions to treat preexisting astigmatism. With the neutral wound closure, mean postoperative keratometric cylinder averaged less than 1 diopter (D). In the presence of moderate preoperative astigmatism (1.0 D to 1.9 D), the wound revision technique tended to undercorrect, while the astigmatic keratotomy tended to overcorrect. However, the keratotomy procedure resulted in less postoperative cylinder. For cases with substantial preoperative astigmatism (greater than or equal to 2 D), the astigmatic keratotomy groups corrected more of the preoperative cylinder, which resulted in a greater proportion of cases with less than 1 D of postoperative cylinder and a smaller proportion with more than 2 D. Results suggest that astigmatic keratotomy is a useful adjunct to correct preexisting astigmatism in cataract patients. However, this procedure as any incisional refractive surgery technique has a certain amount of inherent biological variability.

Adult↗

PubMed1998

Surgically induced astigmatism with superior and temporal incisions in cases of with-the-rule preoperative astigmatism.

PURPOSE: To evaluate surgically induced astigmatism (SIA), postoperative astigmatism, and uncorrected visual acuity (UCVA) after cataract surgery with superior corneal, superior scleral, and temporal corneal 4.0 mm sutureless incisions in cases of preoperative with-the-rule (WTR) astigmatism. SETTING: Hopital des Quinze-Vingts, Paris, France. METHODS: This prospective evaluation included patients having phacoemulsification with foldable lens implantation through a 4.0 mm incision. Patients with preoperative WTR astigmatism were randomly assigned to 1 of 3 incisions: superior corneal (Group 1), superior scleral (Group 2), or temporal corneal (Group 3). All patients had autokeratometry preoperatively and postoperatively (1 day, 1 week, 1 month, 1 year). Surgically induced astigmatism using the vector method, postoperative astigmatism, and UCVA (patients whose spherical equivalent was with +/- 1 diopter) were evaluated. RESULTS: Ninety patients were included in the study; there were 30 in each incision group. One year postoperatively, Group 1 had 1.52 diopters (D) of SIA and 1.36 D of postoperative astigmatism; 53.5% of patients had a UCVA of 20/32 or better, Group 2 had 0.69 D of SIA (P < .05) and 0.67 D of postoperative astigmatism (P < .05); 82.7% of patients had a UCVA of 20/32 or better (P < .05). Group 3 had 0.69 D (P > .05), 0.98 D (P < .05), and 79.3% (P > .05), respectively. CONCLUSIONS: In this study, the superior corneal incision produced significant SIA, leading to high postoperative astigmatism and poor UCVA. The scleral and temporal incisions produced minimal SIA and good UCVA.

Aged↗

PubMed1990

Is the relation between keratometric astigmatism and refractive astigmatism linear?

Javal's rule, which states that the total astigmatism of the eye--or refractive astigmatism--is equal to 1.25 (keratometric astigmatism) - 0.50 x 90, implies a linear relation between the two entities. Data published by Grosvenor, Quintero, and Perrigin (Am J Optom Physiol Opt 1988;65:292-7) show that for eyes having no more than 2.50 D of keratometric astigmatism, the slope of the regression line for refractive astigmatism plotted against keratometric astigmatism is less than 1.00, rather than the 1.25 required by Javal's rule. When data compiled for eyes having greater amounts of keratometric astigmatism are plotted in the same manner, the slope of the regression line is greater than 1.00, suggesting that the relation between keratometric and refractive astigmatism may be non-linear. However when data for these highly astigmatic eyes are plotted in combination with data published by Grosvenor, Quintero, and Perrigin, they are adequately characterized by a straight-line relation.

Adolescent↗

PubMed1999

Corneal and refractive astigmatism in a sample of 3- to 5-year-old children with a high prevalence of astigmatism.

PURPOSE: To examine the relation between corneal and refractive astigmatism in a sample of pre-school-age Native American children with a high prevalence of astigmatism. METHODS: Subjects were 250 Tohono O'Odham children, 3 to 5 years of age. Each child had corneal astigmatism measured with the Marco Nidek KM-500 portable autokeratometer without pupil dilation, and with the Nikon Retinomax K-Plus portable autorefractor/autokeratometer without and with pupil dilation. Refractive astigmatism was measured using the Retinomax K-Plus, with cycloplegia, confirmed by retinoscopy. RESULTS: Corneal astigmatism exceeded refractive astigmatism, with a median vector dioptric difference of 0.88 D for the KM-500, 0.76 D for the Retinomax K-Plus without dilation, and 0.75 for the Retinomax K-Plus with dilation. The relation between corneal and refractive astigmatism was adequately described by the modification by Grosvenor et al. of Javal's rule, but not by laval's rule. CONCLUSIONS: The results are in agreement with data reported previously for older Native American and non-Native American populations. The modified laval's rule adequately describes the relation between corneal and refractive astigmatism in a population; however, this rule does not provide accurate prediction of refractive astigmatism in individual children or adults.

Arizona↗

PubMed1992

Similarities and differences between the Kelman phacoemulsification and extracapsular cataract extraction procedures in the spontaneous regression of corneal astigmatism from against-the-rule astigmatism.

We perspectively examined the induction and spontaneous regression of corneal astigmatism from preoperative against-the-rule astigmatism [Kelman phacoemulsification (KPE), n = 618; extracapsular cataract extraction (ECCE), n = 192] among cataract extraction surgeries (KPE, n = 1,648; ECCE, n = 443). All data were set on a double-angle coordinate graph, from which the mean +/- SE of the axis and the amount of astigmatism were obtained simultaneously. In the KPE group, the surgically induced astigmatism was independent of preoperative state or age. In the ECCE group, surgically induced astigmatism shifted toward with-the-rule astigmatism, and postoperative recovery was delayed longer in patients over 80 years of age than in those under 70. Postoperative against-the-rule astigmatism was more frequent after KPE. Our first trial to calculate astigmatism from a double-angle coordinate graph was useful in showing astigmatism changes.

Aged↗

PubMed1996

Astigmatic change 1 year after excimer laser treatment of myopia and myopic astigmatism. Melbourne Excimer Laser Group.

PURPOSE: To evaluate the surgically induced astigmatism (SIA) 1 year after excimer laser photorefractive astigmatic keratectomy (PARK) and photorefractive keratectomy (PRK). SETTING: Royal Victorian Ear and Eye Hospital, Melbourne, Australia. METHODS: This study comprised 333 PARK patients and 155 PRK patients treated with a VISX 20/20 excimer laser and followed prospectively for 12 months. Vector analysis of the change in astigmatism was used to calculate the SIA in the PRK group and the percentage of astigmatism corrected in the PARK group. RESULTS: Among patients with low cylinders astigmatic correction varied greatly, particularly in those treated for large amounts of myopia. The spherical PRK treatments yielded a mean induced postoperative astigmatism of 0.47 diopter. There was a linear relationship between this inadvertent SIA and increasing myopia. CONCLUSION: Excimer laser surgery for myopia creates a low degree of random, unpredictable SIA that may be the result of irregular epithelial thickening during postoperative healing. This creates a background noise of astigmatic change upon which the targeted astigmatic correction is superimposed.

Adult↗

PubMed2001

[Postmortem evaluation of corneal astigmatism after astigmatism oriented penetrating keratoplasty].

BACKGROUND: Reduction of astigmatism following penetrating keratoplasty can be achieved if the graft is oriented according to astigmatism parameters in donor and host (AOPKP). Postmortem evaluation of these parameters is therefore essential. The aim of our investigation was to compare postmortem measurements using a hand-held keratometer with those of the living donor's astigmatism. METHOD: The 72-year-old female patient had undergone AOPKP on her right eye. After death the astigmatism in the right eye was evaluated 4.5 h postmortem using a hand-held keratometer. After explantation, the eyeball was examined by computer-assisted topography (TMS-1). RESULTS/CONCLUSION: We could show that hand keratometry in situ is reliable for evaluating astigmatism in donor eyes after death. As far as our AOPKP study is concerned, these results are of great interest. Reduction of postoperative astigmatism following penetrating keratoplasty is only possible if data on astigmatism of the donor and host corneas are available.

Aged↗

PubMed2000

A new concept for the correction of astigmatism: full-arc, depth-dependent astigmatic keratotomy.

OBJECTIVE: The purpose of this study is to introduce and evaluate a new concept in astigmatic keratotomy (AK) named full-arc, depth-dependent AK (FDAK). DESIGN: Noncomparative interventional case series. PARTICIPANTS: FDAK was performed on a total of 37 eyes with regular astigmatism; of these, 16 eyes received FDAK alone, and 21 eyes received FDAK combined with cataract surgery. METHODS: Corneal topography was used to divide the cornea into two discreet regions of "steep" and "flat." Then, paired arcuate incisions, 90 degrees in length, were placed along the full arc of the steep area. The level of astigmatic correction was controlled by varying the incision depth from 40% to 80% on the basis of a provisional nomogram developed by the authors. MAIN OUTCOME MEASURES: Keratometries, corneal topographies, and visual acuities were measured. RESULTS: The FDAK alone group showed a significant improvement from a preoperative corneal astigmatism of 2.90 +/- 0.78 diopters (D) to a postoperative value of 0.89 +/- 0.52 D. The "combined" group also showed significant improvement from a preoperative corneal astigmatism of 2.97 +/- 1.01 D, to a postoperative value of 1.02 +/- 0.45 D. The deviation of achieved correction from attempted correction using vector analysis was between 1.37 D of undercorrection and 0.98 D of overcorrection, with 91.9% of cases within the range of +/- 1.0 D. Slight oblique change caused by axis deviation was observed in seven cases. Both uncorrected and corrected visual acuity showed statistically significant improvement. No serious complications were encountered. CONCLUSIONS: Controlling the level of correction by varying the incision depth allowed the surgeon to use long incisions (90 degrees in length in regular astigmatism) covering the entire steep area, minimizing the undesirable changes induced by conventional deep and narrow incision AK and resulting in an ideal corneal sphericity after surgery. FDAK enabled the surgeon to accurately control the level of astigmatic correction with minimal risk of corneal perforation.

Adult↗

PubMed2000

Correction of high astigmatism with astigmatic keratotomy combined with laser in situ keratomileusis.

PURPOSE: To evaluate the efficacy, predictability, and stability of a combined procedure, arcuate keratotomy and laser in situ keratomileusis (LASIK), for the correction of high astigmatism. SETTING: Instituto de Microcirugía Ocular (IMO), Barcelona, Spain. METHODS: Fifteen eyes of 11 patients with naturally occurring astigmatism (NOA) (86. 66%) or surgically induced astigmatism (SIA) (13.34%) between -3.00 and -8.00 diopters (D) who had astigmatic keratotomy were studied. The patients had a secondary procedure, LASIK, to correct the residual refractive error. RESULTS: Mean baseline spherical equivalent refraction was -2.47 D +/- 3.69 (SD) and mean refractive cylinder, -4.59 +/- 1.66 D. Twelve months after LASIK, mean spherical equivalent was -0.09 +/- 1.50 D and the mean refractive cylinder, -1. 21 +/- 1.07 D. The mean cylindrical correction attempted in the NOA group was -4.05 +/- 1.19 D and in the SIA group, -7.00 +/- 1.41 D. Postoperatively, the values were -1.50 +/- 1.17 D and -1.62 +/- 0.17 D, respectively. Twelve months after LASIK, the uncorrected visual acuity (UCVA) was 0.5 +/- 0.1. The UCVA in the NOA group (0.50 +/- 0. 08) was better than in the SIA group (0.32 +/- 0.10). The efficacy index was 0.96 overall. Best corrected visual acuity deteriorated by 1 Snellen line in 1 case (6.6%) but improved by 1 and 2 Snellen lines in 4 cases (26.6%) and 2 cases (13.3%), respectively. All procedures were completed without adverse reactions intraoperatively or postoperatively. CONCLUSION: This combined technique was effective in the treatment of high astigmatism, with excellent results compared with the results of each procedure alone. Because of its high predictability, we strongly recommend the technique in cases with astigmatism higher than 3.0 D, particularly in those with astigmatism higher than 5.0 D.

Adult↗