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PubMedDate not supplied

[Causes, prognosis and prevention of cicatrical corneal astigmatism].

Penetrating wounds of the eyeball in 57-66% cases are associated with corneal involvement leading to the development of cicatricial astigmatism and decrease of the functional results. We investigated the causes of posttraumatic cicatricial corneal astigmatism, possibilities of its prediction, prevention, and correction. The results of treatment of 256 patients with corneal wounds and cicatrices are analyzed. Our analysis confirmed that the severity of astigmatism in corneal wounds directly depends on the wound size, edge status, direction, location, and structure of the forming cicatrix. Adequate and timely primary debridement of the corneal wound with intraoperative keratometric control plays the key role in minimization of cicatricial astigmatism. Early therapy with drugs stimulating the regeneration processes promotes more complete recovery of corneal tissue structure and decrease of astigmatism severity. Timely dosed slackening or removal of sutures makes possible modulation of astigmatism development. A formula is proposed, using which makes it possible, on the basis of initial data on the corneal wound, to estimate the possibility of corneal astigmatism, i.e. predict the outcome of the injury.

Astigmatism↗
PubMed2004

[Higher-order aberrations in myopic and astigmatism eyes].

OBJECTIVE: To analyze the distribution of the higher order aberrations in the population of Chinese with myopia and astigmatism and determine whether the pupil size, degree of myopia and astigmatism affects the higher order aberrations. METHODS: Using a Tscherning method, 147 myopic and astigmatism eyes were evaluated before LASIK. The root mean square (RMS) values of higher order aberrations for each subject with pupil diameters of 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0 mm were calculated. The subjects were divided into following groups: high myopia (> -6.00 D) and low myopia ( or= 0.75 D) and astigmatism group II (< 0.75 D). RESULTS: The root mean square (RMS) values was decreased from 3rd order to sixth order aberrations in the same eye. The individual difference was from 6.1-fold to 36.6-fold in same type of aberration. All types of aberrations, in particular spherical and coma aberration, was increased significantly with increasing pupil size. Secondary spherical aberration, spherical and secondary coma aberration were affected by myopia, but coma aberration; astigmatism only affected the coma aberration, but spherical aberration. CONCLUSIONS: The aberrations were increased with the increasing of refractive error such as myopia and astigmatism. Spherical aberration is more common in high myopia, Coma aberrations is related with astigmatism.

Adult↗
PubMed2004

[Astigmatism at post operational stage after a phacoemulsification cataract removal].

OBJECTIVE: Assessment of post operation astigmatism and dynamics of its reduction within three month after the procedure. MATERIAL AND METHODOLOGY: The research included cataract removal in 140 eyes by means of phacoemulsification (100) and extracapsular (40) methods. Central keratotomy and refraction measurements were conducted with a refractor on 2nd, 7th, 30th and 90th day after the procedure. RESULTS: Average value of postoperative astigmatism after an extracapsular cataract removal was 4.69 D on the second day. After a phacoemulsification without a suture the value was 1.36 D, with a single loop suture -1.98 D, with a single criss-cross suture it was 2.89 D. Two alternative parameters of astigmatism reduction were suggested: a half-value period and a rate of reduction. CONCLUSIONS: Average early postoperative astigmatism values after an extracapsular cataract removal are at least twice as high as in the case of a phacoemulsification cataract removal. A suture applied after a phacoemulsification results in an increase in early postoperative astigmatism. Astigmatism half-value period and rate of reduction provide a good description of the dynamics of postoperative astigmatism reduction.

Adult↗
PubMed1992

Remarkable postcataract against-the-rule astigmatism after phacoemulsification in 83 of 809 cases.

We analyzed 83 cases of remarkable postcataract against-the-rule (AR) astigmatism (greater than 1.5D) occurring in a total of 809 Kelman's phacoemulsification aspiration procedures, all using 10-0 polyester sutures in a double-running fashion to close the corneoscleral incisions. All operations were done by one surgeon, using the same surgical procedure and the same number of sutures. The induction and spontaneous regression of several types of astigmatism were analyzed over six months. In cases of preoperative oblique and AR astigmatism, shifts (2.09 +/- 0.22D, 1.93 +/- 0.13D, respectively) after the first week were much smaller than those of preoperative with-the-rule astigmatism. Thereafter, degrees of oblique and AR astigmatism increased and remained higher even six months after surgery. The induction and spontaneous regression of postoperative AR astigmatism was similar to that of oblique astigmatism. Compression of the lids on the eye may be a more important factor than previously considered.

Aged↗
PubMed1992

Early postkeratoplasty astigmatism following placement of anterior chamber lenses and transsclerally sutured posterior chamber lenses.

Intraocular pseudophakic correction during penetrating keratoplasty (PK) for aphakic or pseudophakic bullous keratopathy may be achieved either with anterior or posterior chamber lenses. Posterior chamber lenses can be fixed to the iris or sclera in eyes lacking adequate posterior capsular support. Post-PK astigmatism can delay early visual rehabilitation of the patient. We reviewed the last 15 patients at our institution who had undergone PK and anterior chamber lens placement for bullous keratopathy. These were compared to the last 15 patients who had undergone PK and transsclerally sutured posterior chamber lens placement. Patients who had placement of a flexible anterior chamber lens at time of PK had a mean astigmatism of 6.73 D at the last visit before any sutures were removed. There was no predominant axis of astigmatism or relationship of the axis of astigmatism to the meridian of lens placement. Patients with placement of a transsclerally sutured posterior chamber lens at time of PK had a mean astigmatism of 5.18 D at the last visit before any sutures were removed. Mean astigmatism was not significantly different (P greater than 0.05) from that seen with anterior chamber lens placement. In the majority of patients the axis of post-PK astigmatism was oriented perpendicular to the meridian of the transsclerally sutured posterior chamber lens.

Aged↗
PubMedDate not supplied

Prospective analysis of photokeratoscopy for arcuate keratotomy to reduce postkeratoplasty astigmatism.

Seven eyes of seven patients with visually disabling postkeratoplasty astigmatism underwent arcuate keratotomy to reduce astigmatism. Keratotomy length was prospectively determined by comparing the corneal shape change needed by each patient with shape changes in cadaver eyes induced by arcuate keratotomy. Keratograph ring ovality quantified corneal shape change. Keratotomies were placed in the wound interface using a diamond knife with blade length set to 100% of corneal thickness. Prekeratotomy keratometric astigmatism was 9.27 +/- 2.14 D (mean +/- SD), and at 2.0 to 18.4 months after keratotomy, astigmatism was 2.75 +/- 2.25 D (mean +/- SD). All corneas had decreased keratometric astigmatism and less oval keratoscope rings. Five corneas had 3.00 D or less residual keratometric astigmatism. Change in ring ovality was significantly correlated with keratotomy length and keratometric astigmatism change. The utility of keratoscope ring ovality as a corneal topography metric was demonstrated by systematically investigating the response to arcuate keratotomy.

Adult↗
PubMed1979

An analysis of corneal transplantation: II--postoperative astigmatism.

An analysis of 153 penetrating keratoplasties was undertaken. The same surgical technique was used in all cases. Three factors had a statistically significant effect on postoperative astigmatism, as measured by keratometry. (1) Astigmatism decreased with increasing follow-up time (P less than 0.05). (2) Vitreous loss at the time of the keratoplasty increased the amount of postoperative astigmatism (P less than 0.05). (3) Females had more postoperative astigmatism than males (P less than 0.05), but this was probably related to a tendency for females to have a greater incidence of postoperative anterior synechiae (P just greater than 0.05), and the fact that all 6 cases of vitreous loss were in females. There was an almost significant trend toward postoperative anterior synechiae being associated with increased astigmatism (P just greater than 0.05), and there was also a trend toward the division of these synechiae reducing the amount of astigmatism. Fifteen of the 153 penetrating grafts were done in cases of herpes simplex. These were compared with 11 lamellar grafts done for herpes simplex, and there was a statistically insignificant trend toward more postoperative astigmatism in penetrating grafts.

Astigmatism↗
PubMed1984

[Intracorneal suture. A simple procedure for the correction of astigmatism after cataract operation].

A simple surgical procedure to cure post cataract-surgery astigmatism is reported. Corneo-corneal (sometimes corneo-scleral), 9-0 polyamide monofilament sutures are put in radially at the end (or at the two ends) of the flattest meridian to increase its curvature and therefore its refractive power. 14 eyes were treated by this procedure, 11 of them for an "against the rule" astigmatism (1st group) and the 3 others for a "with the rule" astigmatism (2nd group). No corneal incision or resection is performed before suturing. Surgery has been efficient in all cases. As compared to a mean pre-op against the rule astigmatism of 6.55 +/- 2.20 diopters, the post-op residual astigmatism was no more than 3.16 +/- 1.94, 2.66 +/- 1.17, 2.69 +/- 1.33 and 2.80 +/- 1.74 diopters, respectively 8 days, 3 months, 6 months, 12 months after the surgery. The average axis of the effect of the surgery was almost perpendicular to the initial axis of the astigmatism. The visual acuity also improved but was dependent on other factors in addition to the refractive surgery. The results were stable from 3 months after surgery and remained unchanged in those cases where the follow-up period was 18 months or more. No significative complications have been observed and side effects have been negligible. In our opinion, the results that we have obtained open the way to the intracorneal suture, without any section of the cornea, as a potential treatment for excessive astigmatism.

Aged↗
PubMedDate not supplied

Correction of myopia and astigmatism using an ablatable mask.

BACKGROUND: Most excimer laser refractive procedures use a computer driven mechanical diaphragm to shape the laser beam. Studies are currently underway using an ablatable polymethylmethacrylate (PMMA) mask to transfer a new spherical or toric curve to the cornea for the correction of myopia and astigmatism; it may leave a smoother corneal surface than diaphragm procedures. METHODS: As part of a Phase IIb FDA clinical study, 25 eyes of 25 patients underwent excimer laser photorefractive keratectomy using a hand held ablatable mask. Fifteen eyes had attempted spherical corrections of up to 6.00 diopters (D) and 10 had toric corrections of up to 6.00 D of sphere and 2.75 D of astigmatism. RESULTS: Seventy-four percent of all eyes achieved uncorrected visual acuity of 20/40 or better--86% in the spherical group and 63% in the astigmatism group. Sixty-nine percent of eyes were within +/- 1 D of the attempted correction. In eyes treated for astigmatism, mean astigmatism decreased from 1.48 D preoperatively to 0.86 D postoperatively. Approximately one half of the eyes treated for astigmatism had a decrease in cylinder of more than 0.5 D. One eye lost 2 Snellen lines of best spherical corrected visual acuity. Video keratography showed toric ablations to result in an elliptical optical zone. Analysis of centration of the procedure showed 66% of ablations centered within 1.0 mm of the center of the pupil aperture. CONCLUSIONS: The ablatable mask represents a promising modality for the treatment of eyes with both myopia and myopic astigmatism.

Adult↗
PubMed1995

[Computerized corneal topography in treatment of high grade astigmatism after perforating keratoplasty].

BACKGROUND: High astigmatism is the most frequent complication of penetrating keratoplasty for keratoconus. The postoperative use of corneal topography enables the surgeon to analyse the surface geometry of the graft and consequently to reduce in controlled steps the postoperative astigmatism. PATIENTS AND METHODS: Based on the measurements of corneal topography 13 patients underwent selective sutures removal and/or arcuate keratotomy to reduce high postoperative astigmatism (> 3 dpt). In 7 cases only selective sutures removal was applied. 5 patients underwent sutures removal combined with arcuate keratotomy and in one case only arcuate keratotomy was performed. RESULTS: The mean astigmatism after perf. keratoplasty was 8.2 dpt (Min. 3.0-Max 19.0). After selected sutures removal or arcuate keratotomy the mean astigmatism was 4.7 dpt (Min. 0-Max. 6.5). The mean reduction corresponds to 4.7 dpt. In no cases we observed an increase in astigmatism after selective sutures removal. CONCLUSION: The measurement of corneal topography after penetrating keratoplasty enables us to better analyse and recognize the tissue forces responsible for high astigmatism and consequently to selectively reduce it.

Astigmatism↗
PubMed1995

[Quantitative evaluation of corneal irregular astigmatism using computed corneal topography].

A new method was developed to quantify corneal irregular astigmatism using computed corneal topography. Refractive powers on a mire ring projected on a toric plane (regular cornea) can be approximated to follow a sine curve. The discrepancy between the approximated sine curve and actual refractive powers was calculated and employed as a parameter of corneal irregular astigmatism. Artificial precision models of a sphere and a toric plane showed similar parameters and the least amount of irregular astigmatism (0.02-0.05D). Consecutive measurements on normal human corneas displayed a reproducible irregular astigmatism range of 0.10-0.25D. Irregular astigatism of the eyes with pterygium was significantly greater than that of normal human controls even from early stages of the disease. Surgery for removal of the pterygium normalized the amount of regular astigmatism regardless of the size of the pterygium, but irregular astigmatism of the eyes with large pterygium (the apex reaching within the central 2 mm cornea) remained at a significantly higher than normal level. It was concluded that the current method enables a quantitative analysis of corneal irregular astigmatism, independent by the amount of regular antigmatism.

Adult↗
PubMed1993

[Calculating the induced, computerized tomography measured corneal astigmatism after cataract surgery with small incision technique and wound closure with single suture technique based on various mathematical models].

Small-incision cataract surgery with scleral tunnel incision and one-stitch horizontal or sutureless wound closure has been found to be an effective way to reduce postoperative astigmatism and to guarantee greater stability of the wound with rapid visual rehabilitation. In some studies surgically induced astigmatism by different wound constructions and wound-closure techniques has been compared to determine the astigmatism induced. Different calculation methods were used leading to different results. Therefore, we evaluated the induced astigmatism in 50 patients operated on by scleral tunnel incision, phacoemulsification with PCL implantation and single-stitch wound closure. We analyzed induced astigmatism on the first postoperative day and 3 months postoperatively by different methods: the simple subtraction method (0.91 and 0.30 D), Naeser's polar value method (-0.74 and -0.75 D), the vector analysis method of Jaffe (2.53 and 1.19 D) and two calculations described by Cravy. Depending on the formula used, different results were obtained. The subtraction method disregards axis change and is less precise. The vector analysis methods obtain the highest values for induced astigmatism and seem to be the most precise for evaluating the real amount of induced postoperative astigmatism.

Aged↗
PubMed1997

Photoastigmatic keratectomy for correction of astigmatism in corneal grafts.

BACKGROUND: The efficacy and safety of excimer laser photoastigmatic refractive keratectomy (PARK) for treatment of astigmatism after penetrating keratoplasty (PKP) was evaluated in this study. METHODS: A VisX 20/20 excimer laser was used to correct the regular astigmatic component of the grafts. The epithelium was removed manually in seven cases and in three patients with the PTK mode of the laser. The results were analyzed for uncorrected visual acuity (UCVA), best corrected acuity (BCVA), haze, and changes in the cylinder and axis. The vectorial change in astigmatism was measured using Alpins' method. RESULTS: Preoperative astigmatism ranged from 3.50 to 11.25 D (mean, 5.98 +/- 2.28) and the mean attempted correction of astigmatism was 6.28 +/- 1.56 D (range, 3.50-9.00 D). The induced reduction of net corneal astigmatism was 48.1%. The vector-corrected astigmatism, which was 6.40 +/- 3.49 D at 1 month postoperatively, was reduced at 12 months to 4.28 +/- 2.42 D. The Alpin Success Index varied in the range 0.06 to 1.0. Although the UCVA improved by > or = 2 lines in 60% of the eyes, the BCVA decreased in 40% of the eyes and three patients required a reoperation. CONCLUSION: Although PARK is relatively safe and effective in reducing post-PKP cylinder and improves UCVA, the frequently and surprisingly late-developing corneal haze often impairs the BCVA.

Adult↗
PubMed1997

[Surgical treatment of astigmatism caused by penetrating keratoplasty using the Hanna arcuate keratome].

PURPOSE: High postkeratoplasty astigmatism is a common postoperative complication which can limit the final functional result. Arcuate incisions are a possible surgical treatment. They can be performed with the arcuate keratome which provides regular incisions. The aim of this study was to evaluate the results obtained with this device in the correction of high postkeratoplasty astigmatism. METHODS: We retrospectively studied ten eyes operated for high postkeratoplasty astigmatism with the Hanna arcuate keratome. Arcuate keratomy procedures were performed on the graft button in all. Before surgery, mean uncorrected visual acuity was 0.07 +/- 0.05. Best spectacle-corrected visual acuity was 0.33 +/- 0.20 and mean subjective cylinder was 6.1 +/- 1.71 D. RESULTS: After one month postoperatively, the mean best spectacle-corrected visual acuity (0.45 +/- 0.20) was significantly improved (p < 5%) and mean subjective cylinder (2.85 +/- 1.29 D) was significantly decreased (p < 5%). Vector analysis showed a 5.59 D (+/- 3.63) mean astigmatism correction. Modifications of the spherical equivalent were not statistically significant. Astigmatism irregularity was not modified. CONCLUSION: Arcuate keratotomy carried out with the Hanna arcuate keratome is effective in reducing high postkeratoplasty astigmatism. It is easier to perform than the standard manual technique. However, astigmatism correction predictibility should be improved.

Adult↗
PubMed1998

[The effect of corneal incision method on astigmatism after cataract extraction].

PURPOSE: To assess the effect of the type of corneal incision and its closure on astigmatism after cataract extraction. MATERIAL AND METHODS: Induced astigmatism was evaluated in 94 eyes after cataract extraction with IOL implantation 7 days, 1 month, 3 months, 6 months and 12 months after operation. 3 groups: were compared I--after extracapsular extraction with corneo-scleral incision (10 h-2 h) and continuous cross-like suture, II--after phacoemulsifications with scleral tunnel incision (3.3 mm) without suture. RESULTS: The highest induced astigmatism was observed 7 days after surgery in patients with the longest corneo-scleral incision with suture (group I). Induced astigmatism gradually decreased in time. In group after phacoemulsification especially with no suture low astigmatism with prompt stabilization was observed. CONCLUSIONS: The length and type of closure of the incision have an essential effect on induced astigmatism. Small incision, especially without suture induces minimal early postoperative astigmatism which remains stabile.

Adult↗
PubMed1998

[Reduction of astigmatism by 4mm long sutureless corneal cataract incision (stretch incision) with phacoemulsification and 5mm PMMA lens implantation].

AIM: Refractive cataract surgery using corneal incisions is aiming at neutralization of preoperative astigmatism. PATIENTS AND METHODS: 61 patients with preoperative astigmatism of 2.25 +/- 0.98 were included in the treatment. A self-sealing corneal tunnel incision measuring 4.0 to 4.1 mm in external diameter and 6.5 to 7.0 mm in internal diameter (stretch incision) was performed on the steeper axis. After capsulorhexis and phacoemulsification a 5 mm PMMA lens was implanted without suturing. Keratometry and corneal topography were performed preoperatively, 3 days and 1 year respectively following surgery. The statistical analysis was based on the Wilcoxon signed ranks test. RESULTS: Surgical induced astigmatism (IA) following superior incisions in cases of astigmatism with the rule (n = 29) amounted to 1.93 +/- 0.97, while lateral incisions in cases of astigmatism against the rule (n = 29) led to an IA of 1.35 +/- 0.73. Axial shifts by more than 30 degrees were 23% following superior incisions and 17%, after lateral incisions. We observed. astigmatic reduction of 1.3 D after superior incisions and 0.7 D following lateral incisions. CONCLUSION: By 4 mm corneal cataract incisions on the steeper axis a high preoperative astigmatism can be reduced significantly without additional keratotomies.

Astigmatism↗
PubMed2001

Pterygium-induced corneal astigmatism.

A significant degree of corneal astigmatism can be induced by the encroachment of a pterygium onto a cornea. The pterygium generally causes with-the-rule corneal astigmatism that is hemimeridional on the side of the pterygium. There is a significant correlation between the extension of the pterygium onto the cornea and the amount of induced astigmatism. However, there is a poor correlation between pterygium-induced astigmatism measured topographically and that measured by manifest refraction. Successful pterygium surgery will reduce pterygium-induced refractive astigmatism and improve visual acuity. This paper outlines the management of a patient with an advanced pterygium, in whom a large degree of corneal astigmatism was induced by the encroachment of a pterygium onto the cornea. Subsequent excision of the pterygium brought about a reversal of the pterygium-induced corneal astigmatism.

Journal Article↗
PubMed2004

Changes in astigmatism after congenital cataract surgery and intraocular lens implantation: a comparative study.

OBJECTIVE: To evaluate the postoperative changes in astigmatism in the pseudophakic eyes of children who underwent 1 of 3 different types of surgical incisions for congenital cataract extraction with intraocular lens implantation, and in whom astigmatism of at least 3 diopters (D) was recorded 1 week after the operation. METHODS: We retrospectively reviewed the medical records of all the children in our department who had undergone surgery for nontraumatic cataract between 1992 and 2001. Cataract surgery with intraocular lens implantation was performed using 1 of 3 types of surgical incisions: a limbal incision, a scleral tunnel, or a clear corneal incision allowing the use of a foldable intraocular lens. In 28 children (32 eyes) aged 2 months to 11 years (mean +/- SD, 4.7 +/- 3.4 years), astigmatism of 3 D or more was found when assessed 1 week after surgery. The refraction was measured and recorded again 3 months and 5 months after surgery. The paired t test was used to compare the outcome variables. MAIN OUTCOME MEASURES: Refractive error 1 week, 3 months, and 5 months after surgery. RESULTS: Mean +/- SD astigmatism 1 week postoperatively was 5.8 +/- 2.2 D, 5.1 +/- 2.1 D, and 4.0 +/- 1.3 D in groups 1, 2, and 3, respectively. Thereafter, the astigmatic component of the refractive error underwent a spontaneous decline, reaching mean +/- SD values of 0.9 +/- 1.0 D, 1.6 +/- 1.6 D, and 1.0 +/- 0.8 D, respectively, in the 3 groups 5 months after the operation. The difference between the mean values at 1 week and at 5 months in each group was statistically significant (P <.001 in group 1; P =.01 in group 2; and P<.001 in group 3). CONCLUSION: Children who underwent extraction of congenital cataract and intraocular lens implantation by different surgical techniques showed a significant spontaneous reduction in astigmatism postoperatively.

Astigmatism↗