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PubMedDate not supplied

[Surgical correction of astigmatism using kerato-resection methods].

The authors analyze the results of surgical correction of hypermetropic and mixed astigmatism, carried out by two methods: clinoid resection of the cornea and clinoid resection of the cornea with tangent autoclinoplasty (i. e. implantation of the resected site to the tangent incision in strongly refracting meridian). Surgical technique has been mastered in experiments with isolated eyes and the mechanism of changes in corneal refraction, resultant from its resection, studied. Experiments with rabbit eyes have shown that after corneal resection cicatrization is over by the third month after surgery. 17 operations with classical clinoid resection and 17 ones with that and tangent clinoid autoclinoplasty were carried out in patients with corneal astigmatism of 2.0 to 6.25 diopters, the follow-up periods being from 6 months to 4 years. The mean reduction of astigmatism after the use of the aforesaid methods has made up 2.47 and 4.8 diopters respectively (according to the data of subjective examination of refraction).

Animals↗
PubMedDate not supplied

Refractive versus keratometric astigmatism postkeratoplasty.

In patients who had undergone penetrating keratoplasty, we compared the relationship between keratometric astigmatism and actual refractive cylinder required for visual correction in 115 eyes postoperatively. The average time from surgery to refraction was 49.5 months and from surgery to keratometry 50.3 months. Sixty-five eyes retaining their running 10-0 nylon sutures had an average of 5.43 diopters of keratometric cylinder and 2.95 D of refractive cylinder. The difference was highly statistically significant (P less than .001). This significant difference was true in eyes with keratoconus and Fuchs' endothelial dystrophy. In 50 eyes with all sutures removed, the average keratometry reading revealed 4.27 D of astigmatism while the cylindrical refraction required in spectacles averaged 3.70 D. The difference was not statistically significant (P = .018). The significant difference between astigmatism as measured by keratometry and by refraction in eyes with the sutures still in place should be taken into consideration when using suture removal or adjusting techniques after keratoplasty.

Astigmatism↗
PubMed1990

[The experience of the surgical treatment of astigmatism].

The paper analyses results after 133 operations on occasion of a simple, mixed and compound astigmatism; 4 methods of surgical correction were used: longitudinal, tangential, radial and combined. The analysis has shown that corneal astigmatism of different kinds and degrees can be corrected by different methods of anterior keratotomy. As a result of surgical treatment, the degree of refraction of both spherical and cylindrical, reduced and visual acuity with tolerant correction increased. The choice of the method depends on the kind and degree of astigmatism and the degree of the spherical ametropia of the operated eye.

Astigmatism↗
PubMed1990

Astigmatism and tissue-shape disparity in penetrating keratoplasty.

Tissue-shape disparity between the donor and recipient cornea is a major cause of astigmatism following penetrating keratoplasty. We studied the topographic effects of recipient or donor tissue deficiency (oval donor button or recipient hole) in a penetrating keratoplasty rabbit model. The results demonstrated that a crescent-shape block resection of 0.5 mm x 6.0 mm during penetrating keratoplasty induces 4 to 7 diopters of corneal astigmatism, with the steeper meridian along the axis of tissue deficiency. Corneal topography and vector analysis of astigmatism showed steepening along the axis of tissue deficiency and flattening 90 degrees away.

Animals↗
PubMedDate not supplied

[Value of qualitative keratometry for the correction of postoperative astigmatism].

The use of a per operative qualitative Keratometer is of interest in prevention of astigmatism in cataract extraction. Our study, which included two groups of forty patients each, demonstrated that the Karickhoff Keratometer can markedly decrease the degree of immediate post-operative astigmatism = gain of 2.38 delta in comparison with the control group and astigmatism less than or equal to 2 in 35% of the cases.

Astigmatism↗
PubMedDate not supplied

[Our initial experience with the surgical correction of astigmatism by sectorial keratorrhaphy].

The authors analyze the first experience with surgical correction of corneal astigmatism by sectorial keratorrhaphy (SKR). The operation consists in sewing an intralamellar nylon (9.00) suture perpendicular to poorly refracting meridian of the cornea. The mechanism of alteration of the corneal curvature resultant from SKR is similar to that in the known wedge-shaped resection of the cornea. The technique of surgery has been mastered in experiments with 12 isolated cadaver eyes. Morphologic studies of 16 eyes of 8 rabbits have lead the authors to a conclusion that prolonged presence of monofilament sutures in the corneal stroma induces the minimal changes in the adjacent tissues, these changes not augmenting over the follow-up period. 15 operations were performed in clinic, the follow-up periods were 4 to 14 mos. The data of the subjective examination of the refraction indicate that corneal astigmatism has reduced by 0.5 to 5.5 diopters, by 2.0-4.0 diopters in the majority of cases. The results evidence that SKR may be used as a method of choice for the surgical correction of hypermetropic or mixed astigmatism.

Animals↗
PubMedDate not supplied

Irregular astigmatism induced by annular tinted contact lenses.

Three patients developed irregular corneal astigmatism while wearing annular tinted soft contact lenses on a daily basis for 1.5 to 3 years. There was severe keratometer mire distortion, and photokeratoscopy revealed central and midperipheral corneal topographical irregularities in four of six eyes. In a masked protocol, scanning electron microscopy of four contact lenses revealed physical deformations in three lenses worn on affected eyes. We propose that latent stress vectors were created when the affected contact lenses were tinted. With patient usage, the stress vectors matured into physical deformations that induced irregular astigmatism. The astigmatism resolved upon discontinuing wear of these lenses, and the patients were able to wear other lenses with no recurrence of symptoms.

Adult↗
PubMedDate not supplied

Fluoroperm extended wear RGP contact lenses for myopia, hyperopia, aphakia, astigmatism, and keratoconus.

One hundred fifteen eyes of 62 patients were fit with paflufocon-A (Fluoroperm) rigid gas permeable (RGP) contact lenses. Patients included myopes, hyperopes, aphakes, and keratoconic and astigmatic patients; the latter patients were fit with bitoric designs for large amounts of corneal astigmatism or front toric designs for residual astigmatism. Thirty of the 52 patients (58%) who completed the study were able to wear the lenses continuously without complications; six (12%) were able to achieve extended wear for up to one month. The average visual acuity across the study was 20/20. Three complications were observed, resulting in a complication rate of 6%.

Acrylic Resins↗
PubMed1988

Results of a graded relaxing incision technique for post keratoplasty astigmatism.

A technique of graded relaxing incisions and compression sutures was performed for correction of post keratoplasty astigmatism in six patients who were spectacle and contact lens intolerant. Correction was achieved in all six patients after surgery, five with spectacles and one with a contact lens. Keratometric astigmatism decreased from an average of 9.63 diopters preoperatively to 2.17 D postoperatively, a reduction of 7.46 D, or 77%. Up to 13.50 D of correction was obtained. In general, the effect of surgery progressed from 1 week to 3 months postoperatively, and regressed from 3 to 6 months. Complications included perforation in two patients, one requiring suturing and application of tissue adhesive, and graft reaction in two patients. Although the number of patients is small, it appears that this technique can successfully reduce post keratoplasty astigmatism, even in excess of 10 D.

Adult↗
PubMed1988

Changes in contrast sensitivity induced by spherical hydrogel lenses on low astigmats.

Contrast sensitivity values were taken on seven astigmatic (cylinder correction under 1.00 diopter) and eight spherical myopes using the Vistech VCTS 6500 System. For the astigmatic group, no significant difference in contrast sensitivity was found between the full subjective correction and an equivalent spherical spectacle prescription, despite the absence of cylinder correction. However, comparing the full subjective correction with an equivalent spherical hydrogel lens, we found a significant decrease in contrast sensitivity while wearing lenses for all but the highest spatial frequency tested. Using a group of spherical myopes, we were unable to demonstrate a decrease in contrast sensitivity as a product of hydrogel lens wear alone. Our findings suggest that there is a measurable decrease in contrast sensitivity as a result of fitting low astigmats with spherical hydrogel lenses which cannot be attributed solely to hydrogel lens wear or the absence of cylinder correction.

Adult↗
PubMed1988

Corneal astigmatism after cataract extraction.

We studied all cataract surgery done at the ophthalmologic clinic of the University of Bari, Italy in the last 20 years (1966-85). We considered three methods of anterior-chamber incision (blade, Worsth's knife, Graefe's bistoury) and their effect on the dioptric values obtained from ophthalmometry a year after surgery. The larger corneal astigmatism occurred after opening the anterior chamber with Graefe's method; the best results were obtained using Worsth's knife. In this evaluation, the surgeon was not considered. Because postsurgical astigmatism is important for visual acuity after cataract extraction, it is desirable to keep astigmatism as minor as possible.

Astigmatism↗
PubMed1987

[Prediction of post-surgical astigmatism in pseudophakia].

After cataract surgery, the patient wants its vision to be as he remembers it was. We known that this is very difficult to reach; however it is quite possible to approach what would be a practically normal vision, since rather than attaining maximum vision possible (10/10), we must attain what the patient sees as normal dimensions in the space. If there is a high degree of astigmatism left, this goal will not be fully attained even with an intraocular lens. Therefore, we have analyzed the degree, type and evolution of astigmatism along the time, after EICC in some cases and planned EECC in other cases, using in the first ones resorptive sutures and in the second ones non-resorptive sutures, so to predict, through a statistical study, and in each one of the two groups, the astigmatism the patients will have in each one.

Aged↗
PubMed1979

[Surgical correction of corneal astigmatism after corneal graft].

We performed Troutman's technique of corneal wedge resection in 6 patients who had substantial astigmatism after penetrating corneal grafts. The astigmatism was reduced by 5 to over 15 dioptres, and was stable for up to 36 months. The visual acuity was considerably improved in 5 of the 6 cases. However we could not neither predict the amount of correction nor the axis of the residual astigmatism with this technique. We stress the importance of using a keratometer when performing a penetrating corneal graft.

Adult↗
PubMed1985

The surgical management of corneal astigmatism after penetrating keratoplasty.

Seventeen patients with high astigmatism ranging from 5.63 to 19.50 diopters after penetrating keratoplasty had further surgery performed to reduce the astigmatism. Twelve patients had a mean reduction of 4.70 diopters ranging from 1.75 to 10.50 diopters. Four patients had a mean increase of 4.81 diopters with a range from 2.13 to 9.00 diopters. We have found that large amounts of astigmatism can be corrected with relaxing incisions within or circumferential to the graft-host interface but the predictability of the surgical outcome is not satisfactory in all cases.

Adult↗
PubMed1985

Control of postoperative astigmatism.

The surgical technique of wound opening and closure for planned extracapsular cataract extraction (ECCE) and posterior chamber lens implantation is described and the final postoperative corneal astigmatism is analysed and discussed. A prospective study of 720 cases divided into 2 groups was undertaken; Group I using the Terry surgical keratometer and Group II not using the Terry Keratometer. Out of 3 surgeons, only one had statistically significant lower K-readings in the early and late postoperative periods in Group I compared to Group II. The percentage of cases with final corneal astigmatism of 2 diopters or less in the early and late postoperative period is higher in Group I than in Group II. The factors influencing final postoperative corneal astigmatism are discussed.

Astigmatism↗
PubMed1985

The relation of astigmatism and hyperopia (more effective plus).

Two-hundred and ninety eight high astigmatic refractive errors are reviewed in order to establish the clinical and theoretical relationship of high astigmatism to hyperopia. All methods of analysis demonstrated that high astigmatism and greater plus power are related.

Adolescent↗
PubMed1985

Variation of astigmatism with accommodation and its relationship with dark focus.

The refraction of 122 eyes was measured for five distances of fixation with an objective Canon Auto Refractor. The cylindrical component was found to vary, but by a small amount. We found no evidence of a deliberate reduction in astigmatism with accommodation, in accord with other studies. The axis was also found to vary by at least 5 degrees in about half of the subjects tested, which is also in good accord with other investigations. The dark focus of 31 eyes was not found to correlate with a minimum astigmatic distance, since this only occurred in 11 out of the 31 eyes. For these 11 eyes, the correlation of dark focus and the dioptric distance where astigmatism was minimum was equal to + 0.54. It implied that for those eyes (about one-third of all types) there was a tendency to yield the best optical quality at the dark focus.

Accommodation, Ocular↗
PubMed1985

The development of visual acuity in infant astigmats.

Acuity for vertical, horizontal, and oblique gratings was measured in 77 infant astigmats using a preferential looking procedure. Measurements were made with the refractive error uncorrected. Most of the infant astigmats were slightly to moderately hyperopic with respect to the test distance of 50 cm. Their acuity was not significantly different from that of a group of non-astigmatic infants. Average acuity for vertical and horizontal gratings increased from 6/200 at 1 month of age to 6/24 at 1 yr. Average acuity for oblique gratings increased more slowly, so that by 1 yr of age it was only 6/33. The only infants to show reductions in acuity were those with a strong myopic focus and one infant with a very strong hyperopic focus. When this infant was tested with optical correction, acuity improved to normal levels. This suggests that meridional amblyopia develops sometime after the first year of life or that it is confined to high spatial frequencies.

Astigmatism↗