Astigmatic Keratotomy Research Articles

Transverse astigmatic keratotomy An integral part of small incision cataract surgery

Transverse astigmatic keratotomy (TAK) is used with an astigmatically neutral wound to control against-the-rule astigmatism. Previously both wound manipulation and TAK have been used to alter astigmatism, but with the advent of astigmatically neutral small incision surgery, astigmatism control involves TAK alone. This paper discusses the TAK approach to astigmatism control and includes a nomogram for incision size.

Reduction of corneal astigmatism at cataract surgery

We studied the effect at three months of four transverse astigmatic keratotomy incisions (TAK) performed prior to phacoemulsification in 61 eyes on corneal astigmatism. The optical zone was varied in each case depending upon the magnitude of preoperative astigmatism. The eyes were compared to 105 control eyes in which no astigmatic incisions were performed to assess the estimated effect of the TAK incisions. Keratometry readings were taken preoperatively and three months postoperatively. Surgically induced astigmatism was measured using vector corrected astigmatism. Improvement in astigmatism was reported in all three optical zone groups, but the astigmatism was undercorrected in each. No complications affecting vision were reported, indicating that TAK may be a safe way to reduce postoperative astigmatism when combined with phacoemulsification.

Retinal Detachment Following Radial and Astigmatic Keratotomy

Serious complications of radial keratotomy are infrequent, but include: iridocyclitis, microbial keratitis, endophthalmitis, corneal perforation, and traumatic wound rupture. We report a case of retinal detachment following microperforation during radial keratotomy.

Paired Relaxing Incisions for the Control of Astigmatism

The problem of astigmatism, occurring both congenitally and in conjunction with cataract and refractive surgery, is a common and significant one. A review of patients in this study shows 18% greater than 2 diopters and 6% greater than 3 diopters of astigmatism measured by keratometry. Many methods for correcting this astigmatism have developed, including long peripheral incisions, both straight and curved, the many varieties of the Ruiz procedure, and short paired relaxing incisions. I have reviewed my results for short paired incisions following cataract surgery, congenital astigmatism, and radial keratotomy at 6 months following surgery. The average change in astigmatism was 2.69 +/- 0.78 (manifest)/2.35 +/- 1.09 (keratometry) for the 5-mm optic zone following cataract surgery. Paired relaxing incisions following radial keratotomy showed a change in astigmatism of 0.92 +/- 0.19 (manifest)/1.29 +/- 1.29 (keratometry) diopters for the 6-mm optic zone and 2.12 +/- 0.34 (manifest)/2.25 +/- 0.49 (keratometry) diopters for the 5.5-mm optic zone. No significant complications and no large overcorrections were encountered.

Astigmatic keratotomy: A review of basic concepts with case reports

Despite the use of small incisions, better wound closure, and other technical improvements in cataract and corneal surgery, astigmatism remains a problem for the cataract and refractive surgeon. Case reports illustrate the applicability of astigmatic keratotomy in postcataract and idiopathic astigmatism. The basic concepts of corneal relaxing incisions are reviewed and the frequently misunderstood coupling phenomenon is explained in the light of the “law of elastic domes.” Properly used, astigmatic keratotomy with coupling effectively corrects a wide variety of types of astigmatism.

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.

Astigmatic keratotomy to correct preexisting astigmatism in cataract patients

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

Radial keratotomy: 500 consecutive cases.

A report on 500 consecutive eyes having radial keratotomy for myopia and myopic astigmatism is presented. Surgery was on an out-patient basis under local anaesthetic, with a follow-up of 99.2% of cases, 91.8% of the 294 patients elected to have radial keratotomy on the fellow eye. The surgical protocol was designed to minimise side effects and complications rather than maximise the reduction in myopia. 6/12 unaided vision or better was achieved by 99% of cases in the low myopia group, 91% in the middle and 41% in the high myopia group. Persistent hypermetropia of +1.00D or greater occurred in only 0.4% of cases and secondary astigmatism of 1.00D or greater in 1% of cases. Corneal perforations were minimised by single-pass incisions, but this was at the cost of lesser myopic corrections in the higher myopic group. Centering on the visual axis rather than the centre of the pupil minimised glare sensitivity. No patient developed potentially blinding complications.

Blindness Following Retrobulbar Anesthesia for Astigmatic Keratotomy

ABSTRACT Retrobulbar anesthesia has become the most common form of anesthesia used in ophthalmic surgery. Acute blindness is a rare but known complication of retrobulbar anesthesia given for intraocular surgery. I report a case of acute, permanent blindness caused by direct trauma to the optic nerve when retrobulbar anesthesia was used for an astigmatism correction procedure. Complications, sometimes probably too incidental or insignificant to be noticed, probably occur far more frequently than a review of the literature would indicate. Using dull shorter needles, proper eye positioning, and injection technique will minimize risk of injury to the optic nerve. Another alternative under review is the use of peribulbar anesthesia. Perhaps the best way to prevent a complication from a retrobulbar injection, however, is to carefully and judiciously consider whether any injection at all is needed.

Refractive surgery: through the looking glass

Historically, surgical procedures designed to change the refractive power of the cornea have been controversial at their inception, gaining acceptance only with time and study. From intraocular lenses to corneal remodelling with the excimer laser, and numerous procedures in between, including radial keratotomy, epikeratophakia, incisional keratotomy for astigmatism, and hydrogel and polysulfone implants, ophthalmologists have balanced the risks and benefits for their patients to produce the maximum benefit at the least cost. The present status and future potential of each of these are assessed as they appear today. There is no question that progress will continue, and that our patients will be the beneficiaries of our ongoing interest in improving older procedures and developing new techniques for the correction of refractive errors.

Analysis of astigmatic keratotomy

Eighty-two keratotomy procedures were performed for both idiopathic and postsurgical astigmatism or myopic astigmatism and analyzed for efficacy using vector and linear regression analysis. Delta keratometry values (delta K) ,were computed for each case as delta K in the desired axis of effect using vector analysis. Six different procedures were compared including both intersecting and nonintersecting trapezoidal keratotomy, relaxing incisions with compression sutures, T cuts with radial keratotomy, T cuts alone, and RK with elliptical optical zones. Our results showed that the greatest shifts occurred in the trapezoidal groups, whereas the most predictable effects occurred in the relaxing incision/compression suture group. Astigmatic keratotomy is capable of producing large shifts in corneal astigmatism; however, the accuracy of these procedures remains highly variable.

Irregular Astigmatism After Radial and Astigmatic Keratotomy

Eleven eyes of six patients, who had been referred for management of irregular astigmatism after receiving crossed incisions for myopic astigmatism, had moderate to marked irregular corneal astigmatism with marked flattening in the meridians of intersecting incisions. All six patients had a decrease in best-corrected visual acuity with spectacles after surgery. Visual acuity with spectacles was 20/40 in five of 11 eyes; with contact lenses it reached 20/40 in ten of 11 eyes. However, two patients could not wear the contact lenses because of lens decentration caused by the marked distortion in corneal topography. Even with contact lenses, visual acuity could only be improved to 20/25 or better in six of 11 eyes.

Corneal press-on ruler for astigmatic keratotomy

Corneal press-on ruler for astigmatic keratotomy

Astigmatism control for the cataract surgeon: A comprehensive review of surgically tailored astigmatism reduction (STAR)

It is increasingly possible for the cataract surgeon to control astigmatism. Based on a review of 4,000 consecutive patients, three categories of astigmatism and cataract patients are identified. A specific approach to astigmatism control for each category is discussed. Preliminary results on the use of astigmatic keratotomy in conjunction with cataract surgery are presented.

Refractive evaluation of astigmatic keratotomy procedures

We evaluated the efficacy of three transverse incision astigmatic keratotomy procedures using a vector analysis that enabled us to determine the magnitude of the effect and the axis in which it occurred. These procedures were used for low levels of astigmatism (0.5 diopter [D] to 3.75 D): (1) staggered, radial-touching transverse (T) incisions, (2) non-radial-touching T incisions, and (3) T incisions with interrupted radial. Most procedures were performed in conjunction with radial keratotomy for spherical correction of myopia. The non-radial-touching T procedure was the least effective method of reducing astigmatism. The staggered, radial-touching T and T with interrupted radial procedures were equally effective in reducing over 93% (on the average) of the preoperative astigmatism. Of these two procedures, the T with interrupted radial procedure was the most accurate, with the effect of the surgery deviating less than ten degrees from the desired axis in over 70% of the eves.

Surgical correction of astigmatism using paired T-incisions

Transverse incision astigmatic keratotomy procedures were performed, combined with radial keratotomy, in 16 eyes for correction of astigmatism and coexisting myopia. We used a transverse incision technique in which T-incisions vertically intersected radial incisions of the steepest corneal meridian. After a mean follow-up period of 10 months with a range of six to 27 months, an average 1.92 diopters of the cylinder was corrected. In comparison with 2.11 diopters of the cylinder corrected at postoperative one day, there was a 22.8% decrease in the effect of astigmatism correction after a postoperative period averaging 10 months.

William H. Bates: The Originator of Astigmatic Keratotomy and Psycho-ophthalmology

William H. Bates: The Originator of Astigmatic Keratotomy and Psycho-ophthalmology

Transverse astigmatic keratotomy combined with phacoemulsihcation and intraocular lens implantation

Transverse astigmatic keratotomy is a surgical technique to correct preoperative corneal astigmatism during cataract surgery. The operative technique is described and the results of my first 40 cases are reviewed. The average keratometric astigmatism for this group before surgery was 2.6 diopters (D). The average reduction in astigmatism was 1.5 D, which yielded a final residual average astigmatism of 1.1 D after surgery. Cases of substantial astigmatism showed the most improvement. Less improvement was seen in cases of minimal preoperative astigmatism. No increase in net keratometric astigmatism was seen in any of the eyes studied. Minor complications were limited to several small corneal abrasions created by the frontcutting diamond blade and one late temporary wound dehiscence. The only serious complication was one case of corneal macroperforation. Recommendations for handling this complication and future high astigmatism cases are given.

Management of Overcorrection Following Astigmatic Keratotomy

ABSTRACT: Overcorrection may be seen following any surgical procedure designed to correct astigmatism. We describe a technique in which overcorrection following astigmatic keratotomy may be managed by reopening of astigmatic incisions followed by closure with interrupted compression sutures. The principal advantage of this technique is that it avoids placement of additional corneal incisions.

Surgical Correction of Postoperative Astigmatism

The photokeratoscope has increased the understanding of the aspheric nature of the cornea as well as a better understanding of normal corneal topography. This has significantly affected the development of newer and more predictable models of surgical astigmatic correction. Relaxing incisions effectively flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. The net change in spherical equivalent is therefore negligible. Poor predictability is the major limitation of relaxing incisions. Wedge resection can correct large degrees of postkeratoplasty astigmatism. Resection of 0.10 mm of tissue results in approximately 2 diopters of astigmatic correction. Prolonged postoperative rehabilitation and induced irregular astigmatism are limitations of the procedure. Transverse incisions flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. Semiradial incisions result in two times the amount of flattening in the meridian of the incision compared to the meridian 90 degrees away. Combination of transverse incisions with semiradial incisions describes the trapezoidal astigmatic keratotomy. This procedure may correct from 5.5 to 11.0 diopters depending upon the age of the patient. The use of the surgical keratometer is helpful in assessing a proper endpoint during surgical correction of astigmatism.