Refractive aspects of cataract surgery

Cataract surgery has progressed to the point where it can now be performed so as to leave most patients emmetropic or with a predetermined amount of ametropia. The two major factors responsible for this prediction accuracy are intraocular lens power calculation and the control of surgically induced astigmatism. Recent theoretical intraocular lens power formulas are more accurate owing to their improved methods for predicting the postoperative anterior chamber depth. Additionally, there are more reliable methods for determining surgically induced astigmatism as well as methods for its control. Various combinations of wound architecture, wound closure, and astigmatic keratotomy and their effect on surgically induced astigmatism are reviewed.

Astigmatism after cataract surgery: nylon versus Mersilene. Five-year data

This is a follow-up of a previous study that evaluated astigmatism after cataract surgery. In that study with a six-month follow-up, there was no statistically significant difference in astigmatism between eyes with nylon sutures and those with polyester fiber (Mersilene) sutures. This article reports the five-year data on this series of eyes.

A new cornea-marking device for penetrating keratoplasty and refractive corneal procedures

In penetrating keratoplasty, postoperative astigmatism is determined by a number of factors, including adaptation of wound edges, mode of trephination of both donor and patient cornea and, last but not least, suture techniques. We would like to introduce a new cornea-marking device for use in keratoplasty and epikeratophakia. This device helps the surgeon to center the trephine and to perform a perfect double running torque-antitorque suture. Additional single sutures are not necessary. A study of postoperative astigmatism following operations in which this device was used is under way.

Long-term natural and modified course of surgically induced astigmatism after extracapsular cataract extraction

A prospective study was carried out to investigate the long-term course of surgically induced astigmatism after extracapsular cataract extraction. Sixty-one eyes were followed for 36 months. In 27 eyes with post-operative astigmatism > 4D with-the-rule, one or two sutures were cut in the steeper meridian after 3 months. In another group of 34 eyes with only minor or no postoperative astigmatism with-the-rule, no suture was cut. We found that 1) postoperative astigmatism was significantly increased in all eyes after 1 week and 3 months, but decreased in time approaching preoperative values after 3 years, 2) surgically induced astigmatism was with-the-rule at 1 week and 3 months but turned against-the-rule in time in both groups. Astigmatism decay rate was significantly steeper in eyes with suture cutting, 3) the keratometric axis was exclusively with-the-rule after 1 week, but turned against-the-rule in both groups, approaching the preoperative distribution of axis after 3 years. We concluded that surgically induced astigmatism is a dynamic feature showing changes in size and axis even in the period 1-3 years postoperatively. Suture cutting seems to intensify the decrease in the induced astigmatism and accelerate the shift in astigmatic axis, turning astigmatism against-the-rule compared to eyes with intact sutures.

Relaxing incisions with compression sutures for control of astigmatism after penetrating keratoplasty

BACKGROUND

Ten per cent of patients with persisting postoperative astigmatism following penetrating keratoplasty (PK) require surgical re-intervention, despite an otherwise "successful" transplant. Relaxing incisions (RIs) in combination with compression sutures seem to be the preferable procedure. However, poor predictability and lack of long-term experience complicate the issue. Here we report the 2-year follow-up results of 25 patients with high PK astigmatism treated by means of RIs and compression sutures.

METHODS

Commonly, free-handed RIs were placed at the graft-host interface and 10-0 nylon compression sutures were placed perpendicular to the incisions. PK sutures had been removed no less than 4 months prior to refractive surgery.

RESULTS

Nineteen eyes regained a functional vision of > or = 0.4. The net decrease in astigmatism was 6.1 +/- 4.3 D (47 +/- 21%). The mean vector-corrected change in astigmatism was 13.1 +/- 5.7 D. Cylinder axis variation was reasonably low, with a correlation of attempted versus achieved axis of r = 0.85. Within the first 3 months after operation the induced astigmatism regressed by, on average, 5.5 +/- 4.3 D, making intraoperative overcorrection necessary. As an inevitable side effect, refractive procedures resulted in a myopic shift (4.7 +/- 6.9 D) in spherical equivalence.

CONCLUSION

RIs and compression sutures are very useful in reducing postkeratoplasty astigmatism if correction of extremely high cylinder (> 10 D) is not intended. However, predictability still remains unsatisfactory and more than one operation may be required.

Corneal topographic analysis of superolateral incision cataract surgery

Using corneal topography, we compared the corneal shape changes following superolateral incision cataract surgery with those following conventional superior incision surgery. In our superolateral incision procedure, a 6.5 mm limbal incision was made from the 9 o'clock to 11 o'clock meridians to avoid incising the superior limbus. One hundred four patients were divided into two groups; Group 1 comprised 66 patients who had surgery using the superolateral approach; Group 2 comprised 38 patients who had surgery using the superior approach. The corneas were examined by keratometer and topographic modeling system preoperatively, and at one week and one, three, and six months postoperatively. Keratometric measurements showed that surgically induced astigmatism (SIA) in Group 1 was significantly less than that in Group 2 throughout the six-month observation. The standard SIA deviation in Group 1 was also smaller than that in Group 2, indicating a smaller degree of variability in the superolateral incision surgery. In the corneal topographic analysis, a color-coded map averaging all the Group 1 corneas at each interval showed a slight steepening in the central cornea in the 10 o'clock meridian one week after surgery. This surgically induced steepening disappeared by one month, and the corneal shape recovered its preoperative shape. In contrast, the Group 2 averaged map showed a marked steepening of the upper and lower corneas. The steepening gradually decreased but remained until three months after surgery. Superolateral incision surgery induced a smaller degree of change in the corneal shape, as well as in SIA, than superior incision surgery. The postoperative corneal shape changes disappeared rapidly after the superolateral incision, and the corneal shape soon stabilized and recovered its preoperative shape.

Randomized clinical trial comparing astigmatism and visual rehabilitation after penetrating keratoplasty with and without intraoperative suture adjustment

PURPOSE

The authors performed a prospective, randomized clinical trial to compare postoperative astigmatism and visual rehabilitation after penetrating keratoplasty with and without intraoperative suture adjustment.

METHODS

Twenty-five patients undergoing penetrating keratoplasty for avascular corneal pathology randomly were assigned to two groups. All surgery was performed by one surgeon (ONS) using the same technique (except for intraoperative suture adjustment) with Hanna trephination (8 mm) and a running 10-0 nylon suture. Postoperative suture adjustment was done during the first postoperative month in all patients who had more than 3.5 diopters of astigmatism. Refraction and computerized topographic analysis were performed at 1 and 6 months postoperatively.

RESULTS

Intraoperative suture adjustment significantly decreased postkeratoplasty topographic (P = 0.0001) and refractive (P = 0.0001) astigmatism and improved best spectacle-corrected visual acuity (P = 0.0019) during the first postoperative month. Seventy-seven percent of control patients (mean topographic astigmatism, 4.89 +/- 1.99 D at 1 month), but no patients who underwent intraoperative suture adjustment (mean topographic astigmatism, 1.50 +/- 0.74 D at 1 month), required at least one postoperative suture adjustment that delayed optical stability and increased postoperative complications. At 6 months postoperatively, mean topographic (P = 0.06) and refractive (P = 0.0001) astigmatism were smaller in the intraoperatively adjusted group than in the control group with postoperative suture adjustments. After intraoperative adjustment, best spectacle-corrected visual acuity was better (P = 0.0168, P = 0.0434) and corneal topography was more regular (P = 0.02, P = 0.07, NS) at 1 and 6 months, respectively, than after postoperative adjustment.

CONCLUSION

Visual rehabilitation with decreased postkeratoplasty astigmatism and more regular corneal topography was attained more rapidly and safely with intraoperative suture adjustment.

The use of the same size host and donor trephine in penetrating keratoplasty for keratoconus

The results of a retrospective analysis of 49 eyes (40 patients) that underwent penetrating keratoplasty for keratoconus are presented. All grafts had the same size trephine for both host and donor corneas. Ninety-eight per cent of eyes achieved a post-operative visual acuity of 6/12 or better; 43% of eyes attained this level of acuity unaided, although more than half of these required spectacles or contact lenses to reach their best corrected acuity. The average post-operative spherical ametropia was -0.5 dioptre (SD 2.97 dioptres) and the average post-operative cylinder was -3.8 dioptres (SD 2.63 dioptres). Three eyes (6%) required keratorefractive surgery to reduce astigmatism. Wound integrity was satisfactory using the same (size) trephine for both host and donor, with no patient suffering a post-operative wound leak or iris prolapse. The reduction of post-operative myopia and astigmatism is discussed.

Some mechanical properties of 10/0 monofilament nylon sutures

A short pilot study is described which investigates some of the mechanical properties of ophthalmic sutures. The Alcon 10/0 monofilament nylon suture was found to behave in a mechanically consistent manner. Like all nylon it possesses the property of 'creep', which helps to compensate for overtightening of the section during surgery.

Refractive stability after cataract extraction using a 6.5-millimeter scleral pocket incision with horizontal or radial sutures

BACKGROUND

Radial suturing of 6.5-millimeter scleral tunnel incisions following cataract surgery can create significant with-the-rule astigmatism in the immediate postoperative period. Because of the significant visual distortion and slow visual recovery seen with radial suturing, this study was undertaken to compare two other suturing techniques which induce lesser amounts of with-the-rule astigmatism in the immediate postoperative period.

METHODS

The refractive behavior of eyes closed with loose radial sutures and with horizontal sutures was compared to the behavior of eyes closed with the more traditional "tight" radial sutures following phacoemulsification surgery.

RESULTS

Eyes sutured with loosely tied radial sutures demonstrated minimal with-the-rule cylinder immediately following surgery (1.25 D) and showed a more rapid stabilization of astigmatism than did the eyes tied with tight radial sutures, 2 months versus up to 6 months. However, the eyes tied with horizontal sutures, which showed no induced with-the-rule astigmatism at the time of surgery, showed even more rapid stabilization between 5 days and 1 month from the time of surgery.

CONCLUSION

To get the most rapid visual rehabilitation following cataract surgery, a wound closure which generates no induced with-the-rule cylinder such as horizontal sutures would be required.

Corneal sutures: is routine removal really necessary?

Three groups of patients were reviewed 1, 2 and 3 years after extracapsular cataract extraction to assess the incidence of problems related to nylon corneal sutures and the need for suture removal. A large percentage of patients were found to have suture-related problems and required or had previously undergone suture removal. These findings are analysed. The potential risk of sight-threatening pathology associated with corneal sutures that are left in situ suggests that routine suture removal about 3 months after surgery is to be recommended.

Refractive error and ocular motility in plagiocephaly

Plagiocephaly, which is caused by premature closure of one of the coronal sutures, leads to fronto-orbital asymmetry. The aim of this work was to study the repercussions of orbital deformation on the visual system. Twenty-one patients presenting with plagiocephaly at birth and operated on by the same craniofacial technique (bilateral approach with translation and advancement of the entire involved orbits) were included in the study. All of the patients were examined by clinical anthropometry with three-dimensional reconstruction and underwent complete eye examination by the same observer. Follow-up after craniofacial surgery ranged from 15 months to 4 years. In the last few years, three-dimensional reconstruction has shown that the anatomic region affected by the deformation is the frontozygomatic region and has thus made it possible to advance to another theory on the origins of ocular problems. The severe effect of orbital anomalies on the development of the visual system (binocular vision, strabismus with amblyopia, refractive errors) has been emphasized in the literature. The present study shows that the scheduling of reconstructive surgery is fundamental and must not exceed 6 months, given the immaturity of the visual system up until this time. This means that the ophthalmologist must be able to recognize the various craniostenoses in order to schedule reconstructive surgery as soon as possible. Cooperation between the neurosurgeon and the ophthalmologist is of paramount importance if the pathogenic effects of this bone deformation are to be stopped and proper visual development preserved.

Suture adjustment in penetrating keratoplasty

Postoperative adjustment of a single running penetrating corneal graft suture was done in 19 patients (22 adjustments). The short-term effect of this procedure was a mean reduction of corneal astigmatism of 4.39D (p < 0.0001). Thereafter, the corneal contour was fairly stable, provided that the running suture remained intact and tight. Localized loosening of the graft suture significantly increased the corneal astigmatism. Following removal of the graft suture no statistically significant mean change of corneal astigmatism was found. However, patients with a previously intact running suture tended to show increased astigmatism, while those with a previous localized suture loosening usually showed a decreased astigmatism after suture removal. The main benefit of suture adjustment is apparently the rapid and fairly stable reduction of postkeratoplasty astigmatism usually obtained, but unfortunately this effect seems chiefly to exist only as long as the graft suture remains intact and tight.

A comparison of two semi-quantitative surgical keratometers: the modified Hyde ruler and the Barrett keratoscope with "astigmatic dial"

The Hyde astigmatic ruler is an inexpensive, semiquantitative, hand-held, surgical keratometer that we modified by geometrically calculating the correct shape of its ellipses. The Barrett keratoscope is a cheap, disposable, qualitative keratometer that, unlike the Hyde ruler, produces a bright corneal image. We designed a transparent overlay, or "astigmatic dial," to use with the keratoscope. This overlay determines the magnitude of astigmatism and sets the distance the keratoscope is held from the cornea by direct comparison with the corneal image. Using a model cornea, we compared our modified Hyde ruler with the Barrett keratoscope and astigmatic dial to determine the accuracy of measurement provided by each. Both instruments had good predictive values for the true astigmatism; however, the Barrett keratoscope/astigmatic dial provided more consistent measurements of the astigmatism. We believe the keratoscope and dial provide a cheap, convenient, and accurate alternative to the more expensive microscope-mounted keratometers.

[A report of 412 consecutive posterior chamber intraocular lens implantations]

The series of 412 consecutive PC IOL implantations comprised 337 eyes of senile cataract, 16 eyes of membranous cataract, 25 eyes of traumatic cataract, 13 eyes of congenital cataract, 10 eyes of complicated cataract and 11 eyes of aphakia. 362 eyes were postoperatively followed up from 4 weeks to 1 1/2 years with the results that 251 (69.3%) eyes obtained visual acuities of 0.8 or over, and 328 (90.6%) eyes 0.5 or over. The authors discussed the technical improvement in anterior capsulotomy and the implantation procedures in cases of posterior capsule rupture. The importance of postoperative control and management of astigmatism, in the recovery of visual acuity was pointed out.

Normalisation of asymmetric astigmatism after intralesional steroid injection for upper eye lid hemangioma in childhood

Infantile hemangiomas affect about 5% (3%-8%) of the population, showing a predilection for the face. After a phase of rapid enlargement between the 3rd and the 9th month of life, 70% regress by the age of six after a period of stability. 43%-60% of the children with eye lid hemangiomas develop strabismic, anisometropic, or deprivation amblyopia. Previous studies found the majority of cases resulting from anisometropia (especially asymmetric astigmatism) rather than strabism or occlusion of the visual axis. Several methods of treatment--surgical excision, irradiation, sclerosing agents, systemic steroids, ligation, cryotherapy--have been used but all with a risk of local or systemic complications. Local injections of steroids are a simple method of therapy with a high rate of resolution of hemangiomas, but still with a high degree of bad visual output because of persistent astigmatism. In four children with asymmetric astigmatism (axis of astigmatism towards the hemangioma) in which the injection was given at the beginning of the phase of enlargement, amblyopia could be avoided by preventing corneal steepening from becoming permanent.

Factors influencing the accuracy of the SRK formula in the intraocular less power calculation

Several intraocular lens (IOL) power calculation formulas (either theoretical or empirical) are used to determine the emmetropic IOL power) The Sanders-Retzlaff-Kraff (SRK) linear regression formula is among the most widely recognized empirical ones. In the present study intraocular lens power calculation aiming at emmetropia was performed, using SRK formula, in 145 cataractous eyes undergoing lens implantation. The final refraction was evaluated at 8 to 12 months after surgery. The purpose of this study was the identification and quantitative evaluation of the factors which influence significantly the accuracy of SRK in the intraocular lens power calculation. The following factors were studied: (1) the error in preoperative biometry with regard to the difference between post and preoperative axial length measurements, (2) the position of the implantation of the intraocular lens (anterior versus posterior chamber), (3) the intraocular lens style, (4) the intraocular lens power level, (5) the preoperative corneal astigmatism, (6) the surgically induced corneal astigmatism, and (7) the postoperative astigmatism. Multiple regression and stepwise regression analysis showed a strong correlation (R2 = 0.65; p < 0.001) between postoperative refractive error (Rf) and error in preoperative biometry (delta AL), surgically induced corneal astigmatism (SIA) and postoperative astigmatism (Ap) only. This correlation is expressed by the following equation: Rf = 0.07 -2.55 delta AL -0.42 SIA + 0.34 Ap. This equation indicates the quantitative effect of each factor on the accuracy of the SRK formula, by defining the pattern of the fluctuations of the amount or state (myopic or hyperopic) of refractive error induced by changes of variables delta AL, SIA and Ap.

The comprehensive control of astigmatism during and following intraocular lens implantation

The operating corneoloscope and Terry operative keratometer were used respectively in 29 and 34 eyes during the intraocular lens implantation to measure the corneal astigmatism qualitatively or quantitatively, so that the tension of incision closure could be adjusted. The surgically induced astigmatism in qualitative group two weeks after the operation was 3.5 +/- 1.70 D and that in quantitative group was 2.56 +/- 1.60 D. There were 55.17% and 38.24% of the eyes with over 2.00 D corneal astigmatism in qualitative and quantitative group two months after the surgery. The astigmatism of both groups at the early stage after the operation was significantly lower than that of the control group (p < 0.05). Argon laser, Nd:YAG laser or razor-blade were used to cut 1 to 3 limbal sutures in 64 eyes with over with-the-rule astigmatism 2.25 D at the early stage (2 months) after the operation. One hour after suture cutting, the with-the-rule corneal astigmatism reduced significantly with an average of 2.61 D. The astigmatism continued to reduce and stabilized one month after the suture cutting. The arcuate keratotomy was performed in 21 eyes, of which the postoperative astigmatism was over 2.25 D (with the average of 3.34 D) more than 6 months after IOL implantation. The mean astigmatism was 0.82 and 1.18 D one day and 6 months after the keratotomy respectively. The uncorrected visual acuity improved significantly after the keratotomy. These results indicate that applying corneoloscope or Terry keratometer to adjust the tension of incision closure during operations, selected suture cutting at the early postoperative stage, and performing arcuate keratotomy at the late postoperative stage be the effective methods to reduce surgically induced corneal astigmatism.

Astigmatic decay following small incision, self-sealing cataract surgery

A series of 22 consecutive patients had phacoemulsification using a small (3.5 to 4.0 mm), self-sealing incision. Preoperative keratometric analysis was performed using the EyeSys photokeratoscope. Results of this analysis were compared with keratometric data obtained at one week and at one month postoperatively. These comparisons were evaluated for surgery-induced cylinder and astigmatic decay at the 3, 5, and 7 mm corneal zones. At one week postoperatively, there was only mild against-the-rule change in cylinder at each corneal zone, and these changes showed minimal decay at the one month follow-up visit.

[Postoperative astigmatism after keratoplasty. Efforts to minimize using selective suture removal with computerized topography control]

The computer-assisted Corneal Topography allows to give an early description of the irregular surface of corneal transplants. With this new method we followed up 109 patients, who had been operated by combined interrupted and continuous suturing. Our experiences with selective suture removal are reported.

Two-step annular tectonic lamellar keratoplasty in severe Terrien's marginal degeneration

We present a case of severe Terrien's marginal degeneration treated with two-step annular lamellar keratoplasty. Both eyes of the patient had peripheral corneal thinning with ectasia around the entire corneal circumference. First, an annular-shaped ectatic lesion was defined and removed, and donor tissue of the same size and shape was sutured on the recipient bed with 10-0 nylon. Four months later, the same operation was performed in the fellow eye. This procedure allows corneal astigmatism to be controlled either by suture removal or resuturing, thereby substantially improving visual acuity. No complications occurred during 1 1/2 years of follow up.

[Intraoperative control of corneal astigmatism during cataract extraction with PC IOL implantation]

The surgical keratoscope and Terry surgical keratometer were used in 29 (group a) and 34 (group b) eyes respectively during cataract extraction with PC IOL implantation to monitor the corneal astigmatism and to adjust the tension of sutures. Two weeks after the operation, the corneal astigmatism in group a was 3.50 +/- 1.70D, and that in group b was 2.56 +/- 1.60D. Two months after the operation, 55.2% of the eyes in group a and 38.2% of the eyes in group b had corneal astigmatism > 2.00D, differing significantly from the higher percentage in the controls. The authors opined that the intraoperative use of the surgical keratoscope and Terry surgical keratometer helped reduce the corneal astigmatism following the intraocular operation.

Astigmatism after phacoemulsification with posterior chamber lens implantation: small incision technique with fibrin adhesive for wound closure

The scleral pocket technique has dramatically changed wound closure after phacoemulsification with implantation of a posterior chamber lens. The use of single-stitch technique and wound closure by fibrin adhesive is now possible. We conducted a comparative study of 385 consecutive patients; 167 received only fibrin glue for wound closure and 218 had the single-stitch procedure. No complications were observed in either group. Surgically induced astigmatism was smaller in the fibrin group (vector analysis: 0.80 diopters [D]) than in the single-stitch group (vector analysis: 0.99 D). Minimal, statistically insignificant different against-the-rule astigmatism developed: single-stitch group: -0.07 D (Cravy), -0.09 D (Naeser); fibrin adhesive group: -0.13 D (Cravy), -0.17 D (Naeser). These results suggest that postoperative against-the-rule astigmatism can be prevented with fibrin glue.

Control of astigmatism aided by intraoperative keratometry

An evaluation of the final "sutures out" postoperative astigmatism in two groups of keratoconus patients undergoing penetrating keratoplasty is presented. Group I consists of a retrospective evaluation of keratoconus patients who underwent penetrating keratoplasty without using the Troutman Keratometer prior to suturing the button into position. Group II patients had their donor button rotated in the recipient bed until approximate sphericity was indicated by a circular reflex from the Troutman Keratometer before suturing into position. The mean final astigmatism with all sutures removed from Group I was 4.64, SD 1.89, and for Group II 2.27, SD 1.27. Selective positioning of the donor button using the Troutman Keratometer leads to a significant reduction in the final sutures out astigmatism in patients undergoing penetrating keratoplasty for keratoconus.

Astigmatism after a large scleral pocket incision in extracapsular cataract extraction

In this four-month prospective study, we measured astigmatism in 116 patients who had extracapsular cataract extraction through a 13 mm scleral pocket incision. In one group, the wound was closed with five radial 10-0 polypropylene sutures. Early and late postoperative astigmatism in this group was approximately 2 diopters (D), but a significant shift to against-the-rule astigmatism occurred. In a second group, an additional 10-0 polypropylene horizontal suture was placed anteriorly to the radial suture at the 12 o'clock meridian. This reduced the against-the-rule astigmatic decay. Moreover, this group had less postoperative astigmatism. Mean corneal astigmatism was 2.27 D at one week, 1.76 D at one month, 1.37 D at two months, and 1.70 D at four months. In neither group was cutting the sutures necessary.

An adjustable double running suture technique for keratoplasty

In a retrospective analysis, we examined 30 consecutive cases of penetrating keratoplasty in which a double running 10-0/11-0 nylon suture technique was used and the 10-0 suture was adjusted early in the postoperative period to reduce astigmatism. When the response to suture adjustment was inadequate, the presence of the 11-0 suture allowed for early (ten to 18 weeks) removal of the 10-0 suture. Rapid visual recovery (12.3 +/- 0.95 weeks; mean +/- standard error) and low levels of final astigmatism (2.66 +/- 0.24 diopters) were achieved. Visual acuity was 20/20 to 20/40 in 25 of the 28 patients (89%) who were visually rehabilitated. In these 28 patients, visual acuity remained stable for the remainder of the study. All patients had a minimum of six months' follow-up from the time of surgery; mean follow-up was 10.6 +/- 1.70 months.

[Phacoemulsification without suture. Results of implantation of a large optic PMMA lens]

Sutureless phacoemulsification with implantation of a 7-mm PMMA intraocular lens was performed through a modified scleral tunnel in 100 consecutive patients. This was done to minimize postoperative astigmatism while retaining the advantages of implanting intraocular lenses with large optics. Visual and keratometric results and complications are reported after completion of a follow-up period of 6 months for the first 30 patients. Average uncorrected visual acuity improved from 0.13 preoperatively to 0.30 as early as 1 week postoperatively. Average best-corrected visual acuity improved from 0.23 before surgery to 0.51 as early as 1 week after surgery. No significant changes in visual acuity were recorded thereafter. The absolute value of keratometric astigmatism was not increased significantly at any postoperative examination time. The induced cylinder (Jaffe and Clayman) shifted from -1.27 D x 166 degrees at 1 week to 1.18 D x 91 degrees at 1 month postoperatively without further relevant changes thereafter. Endothelial cell loss did not differ from that reported by other authors after conventional cataract surgery. Corneal thickness was not increased significantly at any postoperative examination time. Implantation of intraocular lenses with large optics through a scleral tunnel allows quick visual rehabilitation as well as early stability of refraction.

Astigmatism after penetrating keratoplasty using the Krumeich guided trephine system

BACKGROUND

The use of a suction trephine during penetrating keratoplasty has the potential to reduce trephination errors and astigmatism after suture removal.

METHODS

In this study, we evaluated refractive astigmatism after suture removal in 26 eyes that had penetrating keratoplasty for keratoconus using refraction, keratometry, and videokeratography. Group I (11 eyes) had manual trephination with an open disposable blade of both the donor (8.2 mm) and the recipient (8.0 mm). Group II (10 eyes) had manual trephination with an open disposable blade of the donor (8.2 mm) and Krumeich guided trephine system trephination of the recipient (8.0 mm). Group III (5 eyes) had guided trephination of both the donor (8.0 mm) and the recipient (8.0 mm).

RESULTS

The guided trephine groups II and III demonstrated statistically significant less refractive cylinder when compared to manual trephination group I (p < .01). The mean keratometric cylinder for group I was 6.50 diopters (D) (range, 1.50 to 9.00 D), for group II was 3.00 D (range, 0.50 to 7.00 D), and for group III was 2.55 D (range, 0 to 4.00 D).

CONCLUSION

The Krumeich guided trephine system produced less keratometric astigmatism than manual trephination after penetrating keratoplasty for keratoconus.

Effect of incision size on early postoperative visual rehabilitation after cataract surgery and intraocular lens implantation

One hundred fifty-one unilateral cataract patients were randomly assigned to receive either a one-piece Staar AA-4203 silicone intraocular lens inserted through a 3.5 mm incision, an loptex 5 mm x 6 mm oval optic lens inserted through a 5.5 mm incision, or an AMO three-piece modified C-loop 6.0 round optic poly(methyl methacrylate) lens inserted through a 6.5 mm incision. Follow-up was 97% at two days postoperatively and 84% at one week and two months postoperatively. At one week postoperatively, 62% of 3.5 mm incision cases had uncorrected visual acuity of 20/40 or better compared with 33% of 5.5 mm (P < .01) and 43% of 6.5 mm incision cases. At two months postoperatively, 85% of 3.5 mm incision cases had uncorrected visual acuity of 20/40 or better compared with 64% of 6.5 mm (P < .05) and 71% of 5.5 mm incision cases. The 3.5 mm incision cases had significantly less total keratometric cylinder than other cases at all postoperative examinations (P < or = .001) and less surgically induced cylinder at two days and one week post-operatively (P < or = .02). The 5.5 mm and 6.5 mm incision cases did not differ significantly in visual acuity or astigmatism at any examination.

Postkeratoplasty astigmatism with single running suture or interrupted sutures

In a prospective randomized clinical trial we compared astigmatism after penetrating keratoplasty with two different suture techniques between two groups of patients (38 patients). The first group (18 patients) had a 24-bite single running 10-0 nylon suture (single running suture) with postoperative suture adjustment to decrease astigmatism. The second group (20 patients) had a combination of a 16-bite running 10-0 nylon suture and eight interrupted 10-0 nylon sutures (combined running and interrupted sutures) with selective postoperative removal of interrupted sutures to decrease astigmatism. The single running suture resulted in a lower postoperative astigmatism than a combined running and interrupted suture technique (single running suture, 2.7 +/- 2.2 diopters; combined running and interrupted sutures, 3.9 +/- 2.5 diopters; P < .02). Average length of follow-up was similar in both groups (single running suture, 9.0 +/- 2.2 months and combined running and interrupted sutures, 8.4 +/- 2.2 months). Minimal length of follow-up was six months in both groups. No running sutures were broken. The adjustable single running suture technique provided greater control of astigmatism after penetrating keratoplasty than a technique using a combination of a 16-bite running suture and eight interrupted sutures.

Refractive results after phacoemulsification and ECCE. A comparative study

The refractive results were evaluated in 79 patients undergoing cataract extraction by phacoemulsification using a 6-7 mm tunnel incision, and compared with a group of 77 patients undergoing planned extracapsular cataract extraction (ECCE) by the same surgeon. A mean increase in the keratometric cylinder of 0.05D and 0.52D was found in the phacoemulsification and the extracapsular cataract extraction group, respectively. This was significantly different from zero for the extracapsular cataract extraction group (p < 0.05) but not for the phacoemulsification group (p > 0.05). By vector analysis, the mean surgically induced astigmatism was 0.91D and 1.36D in the phacoemulsification and the extracapsular cataract extraction group, respectively (p < 0.01). The IOL power prediction error (spectacle plane) was found to be 0.17D (+/- 0.69 SD) in the phacoemulsification group and 0.02 D (+/- 0.79 SD) in the extracapsular cataract extraction group, respectively. We conclude that phacoemulsification improves the surgical control of the refractive outcome of cataract surgery.

Induced astigmatism and its decay with a frown incision

Forty consecutive patients selected for cataract extraction by phacoemulsification were studied to evaluate prospectively the amount of and changes in surgically induced astigmatism from a 5 mm to 6 mm pocket incision with the external opening made convex against the limbus (frown incision). All incisions had an internal corneal valve and were closed by a single X-stitch to counteract the relaxing effect of the pocket in the 90-degree meridian. Surgically induced astigmatism calculated by simple subtraction was 0.64 +/- 0.90 diopters (D) (P < .0001) on the first postoperative day, 0.03 +/- 0.58 D (P = .75) six weeks after surgery, and -0.18 +/- 0.44 D (P = .01) six months after surgery. Calculated from polar equivalents, the induced astigmatism on the first postoperative day was 0.98 D +/- 1.03 D (P = .0001), after six weeks -0.11 D +/- 0.64 D (P = .30), and after six months -0.28 D +/- 0.49 D (P = .0009). On the first postoperative day 42% of eyes had less than 0.5 D of induced astigmatism, 68% had less than 1.0 D, and 79% had less than 1.5 D. After six weeks the respective percentages increased to 61%, 97%, and 97% and after six months to 84%, 100%, and 100%. The distribution of patients with against-the-rule, oblique, and with-the-rule astigmatism preoperatively was nine, 20, and 11, respectively, and 11, 19, and nine after six months. The amount of astigmatism induced from the 5 mm to 6 mm frown incision did not differ from that found in previously published studies of smaller incisions (to about 4 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of postoperative against-the-rule astigmatism by lateral incision technique

A group of 80 preoperative against-the-rule (AR) eyes had cataract removal and intraocular lens implantation with lateral (temporal) incision and suturing. Fifty-six of the 80 eyes had extracapsular cataract extraction (ECCE) and 24 had phacoemulsification (KPE) with capsulorhexis. For both procedures, subgroups (21 of ECCE, ten of KPE) with high preoperative AR astigmatism (> or = -2.0 D) were evaluated. Analysis of the postoperative data provided the following: (1) induced postoperative cylinder decrease, (2) effect of cutting and not cutting sutures, (3) induced axial shift, (4) postoperative astigmatic change as a function of time, and (5) comparative effectiveness of ECCE and KPE lateral incision procedures in reducing postoperative AR astigmatism.

Modified corneoscleral incision to reduce postoperative astigmatism after 6 mm diameter intraocular lens implantation

I modified the corneoscleral incision for cataract surgery so the incision is located between the 9 o'clock and 12 o'clock positions and termed it the BENT incision (abbreviated from "between nine and twelve o'clock"). I made the incision on 110 patients for phacoemulsification and 6.0 mm diameter poly(methyl methacrylate) intraocular lens implantation and analyzed postoperative corneal astigmatism. The results revealed that the surgically induced astigmatism was 0.3 diopters of with-the-rule shift in the early postoperative weeks and remained virtually unchanged for the subsequent 24 weeks. This amount of astigmatism was significantly smaller and more stable than that of the conventional superior incision performed on 59 patients. A more rapid stabilization of astigmatism after the BENT approach resulted in better uncorrected visual acuity in the early postoperative period. These findings suggest that corneal astigmatism after cataract surgery is affected by the mechanical force of eyelids and extraocular muscles. The BENT incision would effectively minimize the wound-stretching forces and result in earlier stabilization of a lesser degree of postoperative corneal astigmatism.

Glaucoma triple procedures leaving the internal corneal valve intact to control induced astigmatism--theoretic considerations

As glaucoma surgery increasingly tends to be performed in younger patients, stabilizing visual results by reducing the amount of surgically-induced astigmatism will become just as important as controlling intraocular pressure. I describe two glaucoma triple procedures involving small-incision cataract surgery in which, as contrasted with previous techniques, the internal cataract incision is separated from the trabeculectomy, theoretically reducing surgically-induced astigmatism. One method features a standard trabeculectomy with sutures in the scleral flap; the other, an ab externo trabeculectomy in which no sutures are used. The effectiveness of both these methods in actually reducing surgically-induced astigmatism, while controlling intraocular pressure (IOP), remains to be demonstrated, but the possibility that they might, seems well worth exploring.

Long-term results of sutureless phacoemulsification with implantation of a 7-mm polymethyl methacrylate intraocular lens

In an attempt to minimize postoperative astigmatism while retaining the advantages of implanting intraocular lenses with large optics, sutureless phacoemulsification with implantation of a 7-mm polymethyl methacrylate intraocular lens was performed through a modified scleral tunnel in 100 consecutive patients. Visual and keratometric results, as well as complications, were recorded during a follow-up period of 12 months. Average uncorrected visual acuity improved from 20/153 before surgery to 20/66 as early as 1 week after surgery. Average best corrected visual acuity improved from 20/86 before surgery to 20/39 as early as 1 week after surgery. No significant changes in visual acuity were recorded thereafter. The absolute value of keratometric astigmatism was not increased significantly at any postoperative examination time. The induced cylinder shifted from 1.26 diopters x 74.40 degrees at 1 week to 1.22 D x 1.50 degrees at 1 month after surgery, without further relevant changes thereafter. Mean (+/- SD) endothelial cell loss was 7.2% +/- 6.1% at 1 month and 12.2% +/- 5.4% at 6 months after surgery. Corneal thickness was not increased significantly at any postoperative examination time. Implantation of intraocular lenses with large optics through a scleral tunnel allows quick visual rehabilitation as well as early stability of refraction.

Changes in corneal shape after suture cutting using the argon laser for postoperative astigmatism following cataract extraction

We studied the changes in corneal shape after suture cutting with an argon laser to reduce corneal astigmatism following cataract extraction. Sixty-two patients who exhibited high with-the-rule astigmatism (> 3 diopters [D]) following extracapsular lens extraction had argon laser suture cutting. The patients were classified into three groups: Group A comprised 30 patients whose sutures were cut two to three months after planned extracapsular cataract extraction (p-ECCE); Group B consisted of eight patients who had the same treatment five to nine months after p-ECCE; Group C comprised 24 patients who had the treatment one to two months after phacoemulsification (PE). The dioptric reduction of corneal astigmatism (the percent reduction of astigmatism) was 1.83 +/- 0.98 D (37.4 +/- 18.3%) in Group A, 3.20 +/- 2.35 D (55.6 +/- 34.4%) in Group B, and 2.08 +/- 1.20 D (41.4 +/- 20.4%) in Group C. There was no statistical significance in the dioptric reduction and the percent reduction among Groups A, B, and C. This suggests that the wound size and time of cutting are not directly correlated to the effect of argon laser suture cutting. To examine the relationship between the effect and changes in corneal shape from suture cutting, we divided the patients into two subgroups; one was Subgroup (+) in which the percent reduction of astigmatism was above 25%; the other was Subgroup (-) in which the percent reduction was below 25%.(ABSTRACT TRUNCATED AT 250 WORDS)

Timing of removal of sutures in control of post-operative astigmatism

A prospective, randomised study was carried out in 135 patients to determine whether the time of removal of continuous sutures in the relief of post-operative astigmatism had any effect on subsequent changes in cylinder power or axis. After uncomplicated extracapsular cataract extraction with a corneal section and continuous 10/0 nylon suture, patients with more than 3 dioptres of cylinder were allocated to have their suture removed at 6, 9 or 12 weeks post-operatively. Visual and optical outcome were assessed 1 week after suture removal and at 6 months. Although the time of removal did not affect the change in cylindrical power, the subsequent refraction was more stable when the suture was removed at 12 weeks. However, initial against-the-rule astigmatism did not significantly change after suture removal and resulted in an unsatisfactory final prescription. Suture removal should therefore be performed at 12 weeks, glasses should not be prescribed early, and a poor outcome may be anticipated in those initially against-the-rule.

Effect of rigid gas permeable lens flexure on vision

The flexure of spherical rigid lenses (various materials) and a soft lens was measured using automated over-keratometry on 6 adapted rigid lens wearers (12 eyes) whose corneal toricity ranged from 1.37 to 3.87 D. The results showed: (1) that there was no significant difference in flexure between polymethyl methacrylate (PMMA), silicone acrylate, and the fluorosilicone acrylate lenses (whose Dks ranged from 0 to 115). However, Advent (fluoropolymer) did flex significantly more than the other rigid lenses, and significantly less than the soft lens (Bausch & Lomb U4) and (2) that lens flexure of the rigid lenses did not alter over a 2-h period. We also measured high and low contrast visual acuity (HCVA and LCVA), and the results from subjects wearing Advent and the soft lens were significantly worse than with the other rigid lenses. Finally, the results of this study showed no correlation between rigid lens flexure and permeability and between rigid lens flexure and visual acuity when Advent was excluded from the linear regression analysis.

[Preliminary report on the use of excimer laser in treating keratoconus]

Operations for the reduction of astigmatism in cases of keratoconus were performed on 10 eyes in 8 patients. Disruption of the continuity of the posterior limitans lamina of the cornea was not observed in either case. In 4 cases the intervention had to be repeated. The period of observation amounts presently 1-3 months.