Arcuate Keratotomy Research Articles

Combined astigmatic keratotomy with corneal valvular incision in the treatment of high surgical astigmatism

Astigmatic keratotomy is used conventionally to correct moderate surgical astigmatism. However, cases with very high surgical astigmatism due to wound compression can show a dramatic response to relaxing keratotomies made in the steeper meridian. The effect obtained cannot be predicted pre-operatively by using standard nomograms. Coupled arcuate keratotomies combined with corneal valvular incisions were performed in a case of high astigmatism post-cataract surgery. Coupled arcuate keratotomies were combined with a corneal valvular incision enabled a surgical correction of nearly 9 D of astigmatism.

Paired arcuate keratotomy for congenital and post-keratoplasty astigmatism.

To study the effect of arcuate keratotomy on corneal astigmatism in previously grafted eyes compared to eyes with naturally occurring astigmatism. Twenty-three eyes with naturally occurring astigmatism and 21 eyes with post-keratoplasty astigmatism were treated by arcuate keratotomies in the steepest corneal meridian. Visual acuity, spherically equivalent refraction, and refractive cylinder were measured before surgery and 1 to 10 years after the operation. The preoperative refractive cylinder was reduced from 5.0 dioptres (median) to 1.25 dioptres in eyes with natural astigmatism and from 7.0 dioptres to 3.25 dioptres in post-keratoplasty eyes. Spherical equivalent refraction changed from -0.6 dioptres to -1.5 dioptres in eyes with natural astigmatism and from -3.5 dioptres to -4.5 dioptres in previously grafted eyes. The induced change in astigmatism, as calculated by Fourier analysis, correlated strongly with the existing preoperative astigmatism. The effect of the procedure did not correlate with the type of astigmatism (congenital vs. post-keratoplasty), time after surgery, or with patient age or sex. Arcuate keratotomy is a simple procedure to reduce naturally occurring astigmatism as well as induced astigmatism after keratoplasty. Parallel to the astigmatic change, negligible changes in the spherical equivalent are induced.

Depth predictability of stromal pockets in the posterior cornea.

To evaluate the predictability of the depth of stromal pockets made in the posterior cornea for the excision of anterior or posterior lamellar corneal buttons with a planned thickness. Stromal corneal pocket dissections were created in human eye bank eyes by making a peripheral arcuate keratotomy incision at 60, 80, or 95% of central pachymetry and creating a pocket from the bottom of the incision across the cornea. Pocket depth was measured by pachymetry immediately after surgery and by light microscopy. Mean achieved central pocket depth differed by 0.03+/-0.03 mm from the intended depth. Variation in depth across the pocket decreased from 0.07+/-0.02 mm for pockets made at 60% of the intended depth to 0.05+/-0.01 mm for pockets made at 80% depth, and 0.04+/-0.02 mm for pockets made at 95% depth (p < 0.01). Pachymetric and histological measurements of relative pocket depth averaged 64+/-9% and 73+/-7%, respectively, for pockets made at 60% of the intended depth, 82+/-7% and 86+/-3% for pockets made at 80% depth, and 91+/-7% and 92+/-3% for pockets made at 95% depth. The difference between pachymetric and histological relative pocket depth measurements decreased with deeper pocket depth (p < 0.01). In the posterior cornea, stromal pockets can be created to within 30 microm from the intended depth. Variation in depth throughout the pocket decreases with deeper pocket depth. Pachymetry is a reliable method to check the achieved pocket depth during surgery; the accuracy of pachymetry readings improves with deeper pocket depth.

Limbusparallele Keratotomien mit Kompressionsnähten zur Behandlung des hohen Astigmatismus nach perforierender Keratoplastik: Eine vektoranalytische und topographische Studie

Visual acuity following penetrating keratoplasty is frequently limited by excessive astigmatism which cannot be compensated for with spectacles or contact lenses. The purpose of the study was to determine the effects of arcuate keratotomies and compression sutures on the amount and regularity of corneal astigmatism and on the visual acuity. Between June 1989 and August 1995, 56 eyes from 56 patients (30 women, 26 men, average age 53 +/- 16 years) with excessive post-penetrating keratoplasty astigmatism were treated with paired arcuate cuts and compression sutures 4.8 +/- 3.5 years after suture removal (45% keratoconus, 30% scars, 20% dystrophies). The incisions were made along the meridian of maximum dioptric power in a sector extending for 60 +/- 15 degrees (6 mm diameter). Incision depth was standardized at 450 microns. Compression sutures were placed 90 degrees away in the flat meridian. Eight patients required more than one procedure to obtain the desired effect. Best corrected visual acuity (VA), keratometric readings and topographic power maps were analyzed pre- and postoperatively. We categorized the topographic maps into six groups: from group 1 (regular) to group 6 (irregular). For description of the astigmatic change after surgery, the formulas by Naylor and Jaffe (vector-corrected astigmatism) were applied. The mean preoperative astigmatism was 10.8 +/- 3.1 (4.2 to 19.2) diopters (D). After a mean follow-up of 1.1 years, the mean net astigmatism was 5.8 +/- 3.2 (0 to 16) D. The mean preoperative visual acuity (VA) was 0.38 +/- 0.31 (from 0.03 to 1.0). At the end of follow-up, the mean VA was 0.43 +/- 0.25. Non-refractive reasons for poor visual acuity included amblyopia (n = 5), macular degeneration (n = 4), glaucoma (n = 4), cataract (n = 2), and others (n = 5). Twenty-seven percent of the preoperative topographic maps were categorized into groups 1 and 2 and only 10% into groups 5 and 6. At the end of the follow-up, none of the 53 available topographic maps was categorized into group 1, 7.5% into group 2 and 30% into groups 5 and 6. The mean astigmatic change (vector-corrected astigmatism) was 12.3 +/- 5.2 (1.0 to 29.8) D with a turn of the axes ranging from -39 to 44 degrees. Arcuate incisions with compression sutures are easily performed and hold a low complication rate in comparison with other refractive operations. Definition of successful surgery is even broader when a significant reduction of astigmatism that usually allows the use of spectacles or contact lenses is considered. A disadvantage is that each particular case is unpredictable because of the tendency of the topography to irregularity and possible regression of the effect.

Clear Corneal Cataract Surgery and the Correction of Myopia, Hyperopia, and Astigmatism

Advances in cataract removal using topical anesthesia through a clear corneal microincision have created a new opportunity to fully correct refractive errors at the time of cataract surgery. This study was undertaken to assess the effectiveness of keratolenticuloplasty (KLP), the simultaneous modification of the cornea at cataract removal to create emmetropia with lens implantation. Data were analyzed for 690 consecutive cataract procedures performed between March 1993 and March 1995, with follow-up of 12 to 24 months. Each patient underwent cataract removal with topical anesthesia, clear corneal incision fashioned as an arcuate keratotomy to correct pre-existing astigmatism, intercapsular phacoemulsification, and microinjection of a single-piece elastic intraocular lens (IOL) into the capsular bag to correct spherical error. Preoperative best-corrected visual acuity was worse than 20/50 in all patients; 58% were myopic, 32% were hyperopic, and 57% had astigmatism of greater than 1 diopter (D). Postoperatively, spectacle independence was achieved with uncorrected visual acuity of 20/40 or better in 87% of eyes. The sphere was fully corrected in 78%, within 1 D in 17%, and within 2 D in 5%. No patients were overcorrected. The cylinder was fully corrected in 72%, within 1 D in 26%, and within 2 D in 2%. Of those with residual astigmatism, there was no significant postoperative shift in cylinder axis. There were no sight-threatening complications. All patients were able to resume normal unrestricted activities within 24 hours of undergoing the procedure. The KLP technique can correct spherical and astigmatic refractive errors, helping individuals become free of eyeglasses after clear corneal cataract surgery.

Arcuate keratotomy to correct naturally occurring astigmatism

Purpose: To evaluate retrospectively the safety, efficacy, and complications of arcuate keratotomy (AK) in correcting naturally occurring astigmatism.Setting: Laser Ultravision Institute, Montreal, Canada.Methods: Surgically induced refractive change was evaluated in 25 eyes of 15 patients with naturally occurring astigmatism. All patients had mixed or compound myopic astigmatism and were treated with AK alone or both AK and radial keratotomy (RK). Minimum follow-up of 24 months was necessary for inclusion in this study. We used vector analysis to evaluate the refractive and keratometric astigmatic change at 1 month and 1 and 2 years.Results: Ten eyes (40%) had AK only and 15 eyes (60%), both AK and RK. It was necessary to redeepen the original incisions in 21 eyes (84%). All patients had improved uncorrected visual acuity postoperatively. The reduction in refractive cylinder, quantified by vector analysis, was significant. Two years postoperatively, mean reduction was 3.30 diopters (D) ± 1.32 (SD) in eyes that had AK alone and 2.71 ± 1.53 D in eyes that had both AK and RK.Conclusion: Arcuate keratotomy is an effective and safe method for correcting naturally occurring astigmatism. Further analysis of this series of patients is planned.

Analysis of Astigmatic Keratotomy With a 5.0-mm Optical Clear Zone

To investigate the surgically induced refractive change after astigmatic keratotomy with a 5.0-mm optical clear zone in patients with severe naturally occurring astigmatism. We analyzed surgically induced refractive change in 40 consecutive eyes undergoing astigmatic keratotomy with a 5.0-mm optical clear zone. The surgically induced refractive change was calculated according to the method of Holladay, Cravy, and Koch with some modifications. Eyes were divided into two groups: Group I included eyes with mixed astigmatism and a maximum preoperative spherical equivalent of +1.25 diopters that underwent arcuate keratotomy, and Group II included eyes with compound myopic or simple myopic astigmatism (maximum preoperative spherical equivalent of -3.00 diopters) or mixed astigmatism with low minus spherical equivalent that underwent four-incision radial keratotomy and arcuate keratotomy. After refractive surgery, all eyes experienced a reduction of astigmatism when examined three months or more after surgery. Only one eye from each group was overcorrected. The magnitude of refractive astigmatism of surgically induced refractive change was 3.25 +/- 0.90 diopters for eyes in Group I and 3.25 +/- 0.80 diopters for eyes in Group II. There was minimal axis deviation. Eyes in Group I had more flattening with the wound than steepening against the wound, with a coupling ratio of -0.86 +/- 0.36, whereas in Group II, there was flattening both with the wound and against the wound. The net effect of surgery (sum of the primary and secondary effects) was more flattening than steepening in Group I eyes, and flattening of the circumference of the eye in Group II. A decrease of one line of best-corrected visual acuity was observed in one (6.6%) of 15 eyes in Group I and in two (8%) of 25 eyes in Group II. A 5.0-mm optical clear zone arcuate keratotomy is an effective method for correcting moderate to severe naturally occurring astigmatism. Further investigation of this optical clear zone size on glare and contrast sensitivity testing is necessary and is underway.

Arcuate astigmatism keratotomy combined with Excimer laser (PRK) to treat astigmatism and myopia.

Arcuate astigmatism keratotomy combined with Excimer laser (PRK) to treat astigmatism and myopia.

Astigmatism Reduction Clinical Trial-Reply

<h3>In reply</h3> Thank you for the letter regarding the predictability information in our recent publication "Astigmatism Reduction Clinical Trial: A Multicenter Prospective Evaluation of the Predictability of Arcuate Keratotomy."¹The confusion arises over the interpretation of the results presented in Table 5. Predicted results in Table 5 are provided for male patients, but note that 69% of our study participants were women. Our results indicated a strong gender effect, with women averaging 0.37 D less effect than men. If you subtract 0.37 from each result in the "revised" formula in Table 5, you see many more lower predicted results with the revised nomogram. However, where the revised formula shows a greater predicted result, the revised nomogram should be used—such as for the 30-year-old with 2 D of astigmatism—if your goal is a conservative result. The two incisions at 30° and two incisions at 45° plans are the instances in

Rupture of Radial and Arcuate Keratotomy Scars by Blunt Trauma 91 Months After Incisional Keratotomy

We studied a case in which blunt trauma caused dehiscence of radial and arcuate corneal scars 91 months after incisional keratotomy. The ruptured incisions did not extend beyond the corneoscleral limbus. Incisional refractive surgery renders the cornea susceptible to blunt traumatic rupture. This vulnerability results from the intrinsic weakness of the keratotomy wounds. Our case documents that this weakness persists up to 91 months after the operation.

Keratolenticuloplasty: Arcuate keratotomy for cataract surgery and astigmatism

Cataract surgery has evolved into a procedure in which pre-existing refractive errors can be corrected simultaneously to improve uncorrected visual acuity following surgery. This paper describes keratolenticuloplasty, a new technique of clear corneal arcuate keratotomy for cataract surgery that corrects pre-existing astigmatic errors at the time of cataract extraction. This technique uses topical anesthesia, a single pair of arcuate corneal incisions placed on the steepest axis of astigmatism, one-step capsulorhexis, hydrodissection, intercapsular phacoemulsification, and injection of an elastic intraocular lens within the capsular bag. The technique has been used in over 1,000 patients with follow-up of 24 months. Uncorrected visual acuity of 20/40 or better with no associated complications was achieved in 96% of patients.

Mechanical methods in refractive corneal surgery.

Over the past decade, keratorefractive surgery has moved into the mainstream of ophthalmology as improved instrumentation and newer techniques have evolved. These new aspects increase the safety and effectiveness of the various keratorefractive procedures. The introduction of new techniques and knife designs has led to improved results with radial keratotomy. The newly developed arcuate keratome purportedly offers the possibility of improving the predictability of arcuate keratotomy. Keratomileusis and epikeratoplasty have been successful for some difficult refractive states, such as aphakia and high myopia. Intracorneal lenses are showing promise in correcting high refractive errors and may offer an alternative to the more technically challenging lamellar procedures performed for correcting these conditions. Intrastromal ring implants are early in their clinical testing, but may provide an alternative to radial keratotomy for correcting myopia. The predictability, effectiveness, safety, and stability are far from perfect for current procedures, but recent results are encouraging.

Arcuate Keratotomy for the Correction of Spherical Hyperopia in Human Cadaver Eyes

A new experimental surgical technique to correct spherical hyperopia by steepening of the central corneal curvature was performed on human cadaver eyes. Ten eyes were used in the study. All were pretreated with glycerin to ensure a uniform corneal thickness between .55 and .65 mm on ultrasonic pachometry. A constant intraocular pressure of approximately 30 to 40 mm Hg was maintained in each eye by the injection of saline into the vitreous cavity. This was verified by pneumotonometry. A vertical blade diamond knife was set at 100% of the thinnest of four paracentral readings. Each eye underwent preoperative computed topography. One set of five eyes had 12 incisions made following a 5.75-millimeter diameter Mendez hexagonal marker that included unconnected T incisions at each junction (ie, "Hex T" pattern). The other set of five eyes had four arcuate incisions made following a 6-millimeter diameter zone marker; each incision was 60 degrees in arc. Immediately after surgery, computed topography was repeated. The hexagonal keratotomy set of eyes had an average steepening of the cornea of 0.80 D with a range of -1.05 to + 4.38 D. The arcuate keratotomy set had an average steepening of +2.12 D with a range of +1.27 to +3.27 D. This study suggests arcuate keratotomy may be a more effective procedure in the correction of spherical hyperopia when compared with hexagonal keratotomy. The amount of corneal steepening achieved in a cadaver eye model may not be the same as when performed in vivo.

Four-Incision Radial Keratotomy for High Myopia After Penetrating Keratoplasty

High amounts of myopia can frequently produce anisometropia and limit visual rehabilitation by conventional means in eyes with clear corneal grafts. This condition is frequently coupled with large amounts of astigmatism. Four-incision radial keratotomy provides a way to reduce myopia in normal individuals. In our present study, we used the technique of four- incision radial keratotomy to reduce myopia in a group of keratoplasty patients who failed conventional visual rehabilitation. Arcuate or transverse keratotomy was used in conjunction with radial keratotomy in eyes with high amounts of astigmatism. This study retrospectively examined a group of 11 eyes with penetrating keratoplasty which underwent four-incision radial keratotomy for the treatment of visually disabling myopia. The radial incisions were placed in the graft, inside the graft-host interface. Seven eyes underwent concomitant arcuate relaxing incisions at the graft-host interface for treatment of associated astigmatism. One additional eye had paired straight transverse incisions for the treatment of astigmatism. The mean postoperative follow up was 16 months (range, 3 months to 5 years). There was a mean reduction of the spherical equivalent refraction of 3.48 diopters (D) (range, 0.25 to 7.75 D). The eight eyes undergoing astigmatic surgery showed a mean reduction in keratometric astigmatism of 2.25 D (range, -6.75 to +6.50 D) and refractive astigmatism of 4.63 D (range, -1.50 to -9.50 D). Nine of the 11 eyes had stable or improved best spectacle corrected visual acuity. Two eyes had reduction of best spectacle corrected visual acuity--one due to development of irregular astigmatism and one due to worsening of preexisting macular edema. Four-incision radial keratotomy can reduce myopia after penetrating keratoplasty when the patient is unable to tolerate spectacle or contact lens correction. It can be combined with relaxing incisions or transverse keratotomy to reduce astigmatism. There is a high amount of variability, and predictability is currently limited by the complex topographical changes occurring in corneal transplants. Complex corneal biomechanical changes may predispose these eyes to the development of irregular astigmatism.

Circular Keratotomy for the Correction of Astigmatism

Mathematical and physical considerations that are contained in Gauss' law lead to the concept of a circular cut for the correction of corneal astigmatism. The method applied is the coupling of the aspheric corneal surface to the spherical obturator of the Guided Trephine System and cutting of 90% of the parenchyma. Nineteen human eyes were treated with this technique, using a double-running suture closure. Results of reduction of astigmatism can regularly be obtained but are of different amounts depending on the origin of astigmatism. Mean preoperative refractive astigmatism was 5.41 diopters and mean postoperative refractive astigmatism was 1.34 D. Six eyes required additional tranverse arcuate keratotomy. The procedure is effective, but the results are variable. It may be improved by the use of obturators that fit the radius of curvature of the cornea.

Computer Simulation of Arcuate Keratotomy for Astigmatism

The development of refractive corneal surgery involves numerous attempts to isolate the effect of individual factors on surgical outcome. Computer simulation of refractive keratotomy allows the surgeon to alter variables of the technique and to isolate the effect of specific factors independent of other factors, something that cannot easily be done in any of the currently available experimental models. We used the finite element numerical method to construct a mathematical model of the eye. The model analyzed stress-strain relationships in the normal corneoscleral shell and after astigmatic surgery. The model made the following assumptions: an axisymmetric eye, an idealized aspheric anterior corneal surface, transversal isotropy of the cornea, nonlinear strain tensor for large displacements, and near incompressibility of the corneoscleral shell. The eye was assumed to be fixed at the level of the optic nerve. The model described the acute elastic response of the eye to corneal surgery. We analyzed the effect of paired transverse arcuate corneal incisions for the correction of astigmatism. We evaluated the following incision variables and their effect on change in curvature of the incised and unincised meridians: length (longer, more steepening of unincised meridian), distance from the center of the cornea (farther, less flattening of incised meridian), depth (deeper, more effect), and the initial amount of astigmatism (small effect). Our finite element computer model gives reasonably accurate information about the relative effects of different surgical variables, and demonstrates the feasibility of using nonlinear, anisotropic assumptions in the construction of such a computer model. Comparison of these computer-generated results to clinically achieved results may help refine the computer model.

Prospective Topographic Analysis in Peripheral Arcuate Keratotomy for Astigmatism

Delimited peripheral arcuate keratotomy was performed on five eyes of four patients with naturally-occurring astigmatism. Refraction, keratometry, and computer-assisted corneal topographic analysis were performed before and after the procedure. In some eyes, preoperative topographic analysis revealed steepening distributed symmetrically about the corneal apex; in three eyes the steepening was asymmetrically distributed about the corneal apex. In one eye, surgery in a single, steep hemi-meridian superior to the corneal apex flattened that steep hemi-meridian but did not appear to alter the topography of the inferior steep hemi-meridian. Refractive and keratometric astigmatism decreased in all eyes (mean reductions of 3.25 and 2.30 diopters, respectively), and all incisions healed without incident. Surgery extended beyond the zone of steepening in one eye, shifting the axis of astigmatism. A large, multicenter, randomized trial will be necessary to determine whether detailed preoperative topographic analysis can be used to improve the results of surgery for astigmatism.

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.

Paired arcuate keratotomy. A surgical approach to mixed and myopic astigmatism.

Twenty-five cadaver eyes were used to study the effect of paired arcuate keratotomy on corneal astigmatic changes. Paired arcuate incisions placed at optical zones of 5, 6, 7, 8, and 9 mm were progressively lengthened from 45 degrees to 60 degrees, 90 degrees, and, finally, 120 degrees. The corneal flattening in the meridian centered over the incisions and the corneal steepening 90 degrees away were quantified with each successive lengthening. Linear regression analysis showed a direct linear relationship of corneal astigmatic change (sum of corneal flattening and steepening, or delta K) to decreasing optical zone size as measured in millimeters and increasing incision length as measured in degrees. The delta K value ranged from 2.65 +/- 1.07 diopters to 22.05 +/- 3.55 D. The flattening/steepening coupling ratio mean was 1.47 +/- 0.41. Progressively longer paired arcuate incisions produced a predictable and titratable corneal flattening in the meridian centered over the incisions and a slightly smaller corneal steepening 90 degrees away, making the procedure ideal for mixed astigmatism.

Implantation of collagen punctal plugs for the reduction of post-keratoplasty ametropia

In 1995, a 46-year-old woman was referred for refractive surgery. Eleven years earlier, she had undergone an uncomplicated penetrating keratoplasty in her right eye to treat a dense corneal opacity caused by contact lens-related microbial keratitis. Due to high myopia in the graft, she was unable to achieve useful vision and declined contact lens use. After extensive counseling, she elected to undergo radial keratotomy (RK) and arcuate keratotomy (AK) in her right eye. We recommended the insertion of collagen punctal plugs into the keratotomy incisions to increase the RK effect. She also decided to have RK in her left eye. Postoperatively, her uncorrected visual acuity was 20/25 OD and 20/30 OS. We were able to contact her and her ophthalmologist eleven years later, and eight of eleven collagen plugs were still present in the incisions, with no signs of rejection or inflammation. Later, we learned that she underwent a repeat penetrating keratoplasty due to corneal graft failure after a phacoemulsification procedure. The pathologic examination of the intact plugs and graft also showed no rejection or inflammation.