Journal of Refractive Surgery

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Combined Transverse and Interrupted Radial Keratotomy for Compound Myopic Astigmatism

Isaac Lipshitz, MD; Yoram Mayron, MD; Anat Loewenstein, MD

Abstract

ABSTRACT

BACKGROUND: A variety of patterns of keratotomy are used to correct naturally occurring astigmatism. We evaluated straight transverse incisions with interrupted radial incisions (jump radiais).

METHODS: In 32 human eyes with naturally occurring astigmatism, we used straight transverse incisions with interrupted radial incisions, with or without additional radial keratotomy, to correct compound myopic astigmatism. The range of preoperative refractive astigmatism was 1.00 to 3.50 D.

RESULTS: The mean follow-up time was 15 months (range, 12 to 16 months). The average surgically corrected astigmatism was 1 .55 ± 0.29 D. Eightyseven percent of the eyes achieved less than 1 .00 D of astigmatism, and the remaining four eyes retained 1 .00 to 1 .25 D of astigmatism.

CONCLUSION: Combined transverse and interrupted radial incisions are effective in correcting naturally occurring astigmatism. [Refract Corneal Surg 1992;8:280-285.)

RÉSUMÉ

INTRODUCTION. Différentes variétés de kératotomie ont été utilisées dans le traitement de l'astigmatisme myopique congénital. Nous avons évalué l'effet des incisions transverses associées à des incisions radiaires discontinues.

METHODES. Nous avons réalisé des incisions transverses droites associées à des incisions radiaires discontinues dan le traitement de l'astigmatisme congenital de 32 yeux. Des incisions radiaires transverses ont été réalisées si nécessaire pour traiter l'élément myopique de l'astigmatisme.

RESULTATS. Le recul moyen était de 15 mois (12 à 18 mois). La correction chirurgicale de l'astigmatisme était de 1.55 ± 0.29 D. 87% des yeux étaient corrigés à moins de 1 .00 D, seuls 4 yeux étaient entre 1.00 et 1.25 D.

CONCLUSION. L'association incision radiaire discontinue et transverse est efficace dans la correction de l'astigmatisme congénital. (Translated by Jean Marc Legeais, MD, Paris, France.)

SOMMARIO

PREMESSA. Una varietà di modelli di cheratotomia sono usati per correggere l'astigmatismo congenito (primario); noi abbiamo valutato le incisioni rette trasverse con incisioni radiali interrotte (radiali a salto).

METODI. In 32 occhi con astigmatismo congenito abbiamo usato le incisioni rette trasverse con incisioni radiali interrotte con o senza tagli radiali addizionali per correggere astigmatismo miopico composto. L'estensione dell'astigmatismo preoperatorio era fra 1 .00 a 3.50 diotric.

RESULTATI. Il follow up medio era di 15 mesi (da un minimo di 12 ad un massimo di 18 mesi). L'astigmatismo medio corretto chirurgicamente era 1 .55 ± 0.29 D. L'87% degli occhi ha ottenuto meno di 1 .00 D di astigmatism ed il rimanente 4 occhi ha mantenuto da 1 .00 a 1 .23 D di astigmatismo.

CONCLUSIONI. Le incisioni trasverse combinate alle radiali interrotte sono efficaci nel correggere l'astigmatismo congenito. (Translated by Lucio Buratto, MD, Milan, Italy.)

Abstract

ABSTRACT

BACKGROUND: A variety of patterns of keratotomy are used to correct naturally occurring astigmatism. We evaluated straight transverse incisions with interrupted radial incisions (jump radiais).

METHODS: In 32 human eyes with naturally occurring astigmatism, we used straight transverse incisions with interrupted radial incisions, with or without additional radial keratotomy, to correct compound myopic astigmatism. The range of preoperative refractive astigmatism was 1.00 to 3.50 D.

RESULTS: The mean follow-up time was 15 months (range, 12 to 16 months). The average surgically corrected astigmatism was 1 .55 ± 0.29 D. Eightyseven percent of the eyes achieved less than 1 .00 D of astigmatism, and the remaining four eyes retained 1 .00 to 1 .25 D of astigmatism.

CONCLUSION: Combined transverse and interrupted radial incisions are effective in correcting naturally occurring astigmatism. [Refract Corneal Surg 1992;8:280-285.)

RÉSUMÉ

INTRODUCTION. Différentes variétés de kératotomie ont été utilisées dans le traitement de l'astigmatisme myopique congénital. Nous avons évalué l'effet des incisions transverses associées à des incisions radiaires discontinues.

METHODES. Nous avons réalisé des incisions transverses droites associées à des incisions radiaires discontinues dan le traitement de l'astigmatisme congenital de 32 yeux. Des incisions radiaires transverses ont été réalisées si nécessaire pour traiter l'élément myopique de l'astigmatisme.

RESULTATS. Le recul moyen était de 15 mois (12 à 18 mois). La correction chirurgicale de l'astigmatisme était de 1.55 ± 0.29 D. 87% des yeux étaient corrigés à moins de 1 .00 D, seuls 4 yeux étaient entre 1.00 et 1.25 D.

CONCLUSION. L'association incision radiaire discontinue et transverse est efficace dans la correction de l'astigmatisme congénital. (Translated by Jean Marc Legeais, MD, Paris, France.)

SOMMARIO

PREMESSA. Una varietà di modelli di cheratotomia sono usati per correggere l'astigmatismo congenito (primario); noi abbiamo valutato le incisioni rette trasverse con incisioni radiali interrotte (radiali a salto).

METODI. In 32 occhi con astigmatismo congenito abbiamo usato le incisioni rette trasverse con incisioni radiali interrotte con o senza tagli radiali addizionali per correggere astigmatismo miopico composto. L'estensione dell'astigmatismo preoperatorio era fra 1 .00 a 3.50 diotric.

RESULTATI. Il follow up medio era di 15 mesi (da un minimo di 12 ad un massimo di 18 mesi). L'astigmatismo medio corretto chirurgicamente era 1 .55 ± 0.29 D. L'87% degli occhi ha ottenuto meno di 1 .00 D di astigmatism ed il rimanente 4 occhi ha mantenuto da 1 .00 a 1 .23 D di astigmatismo.

CONCLUSIONI. Le incisioni trasverse combinate alle radiali interrotte sono efficaci nel correggere l'astigmatismo congenito. (Translated by Lucio Buratto, MD, Milan, Italy.)

Figure 1: (A) Configuration of the incisions in the procedures in eyes with astigmatism only, (B) myopia and astigmatism at 90°, (C) myopia and astigmatism at 180°, (D) myopia and astigmatism at 80°.Figure 2: The nomogram according to Nordan: (A) In astigmatism of up to 1 .5 D, 1 .5 mm length, (B) in astigmatism of 1 .5 to 2.0 D, 2.5 mm length, (C) in astigmatism of 2.0 to 3.0 D1 1.5 mm length, (D) in astigmatism of 3.0 to 3.5 D, 2.5 mm length.

Figure 1: (A) Configuration of the incisions in the procedures in eyes with astigmatism only, (B) myopia and astigmatism at 90°, (C) myopia and astigmatism at 180°, (D) myopia and astigmatism at 80°.

Figure 2: The nomogram according to Nordan: (A) In astigmatism of up to 1 .5 D, 1 .5 mm length, (B) in astigmatism of 1 .5 to 2.0 D, 2.5 mm length, (C) in astigmatism of 2.0 to 3.0 D1 1.5 mm length, (D) in astigmatism of 3.0 to 3.5 D, 2.5 mm length.

Accurate correction of corneal astigmatism whether naturally occurring, following other surgical procedures, or following corneal trauma is a challenge for the refractive surgeon. There is still great variety in the approach to the surgical correction of astigmatism. Modern techniques utilize incisions cut transverse to the steep meridian. These incisions are called transverse keratotomy or transverse incisions. They may have a straight or arcuate configuration. Sato1 and Akiama et al2 devised a number of patterns of keratotomy to correct astigmatism, including both transverse incisions and grouped radial incisions. These had the problem of being performed on the posterior surface of the cornea. Fyodorov modified this approach by making the incisions on the anterior surface of the cornea. He and Furney proposed ellipses.3 The intersecting transverse-radial (TR) of Fyodorov, flag T of Fenzl, interrupted T of Hofmann, Thornton T between radiais, and the trapezoidal keratotomy of Ruiz all attempted to selectively flatten the steeper corneal meridian (with various amounts of coupling effect on the flatter meridian). The TR keratotomy suffers from instability caused by wound gape. The flag transverse incision is an attempt to prevent complete crossing of the radial and transverse incision, thus reducing the gaping.4 The interrupted transverse incisions attempt to maintain stability by avoiding intersection.5 The Thornton procedure partially prevents junctional discontinuity and utilizes some standardized length of incision with variable optical zone size.6 The interrupted transverse incision and the Thornton incision leave a small amount of intact corneal tissue between the transverse and the radial incision. The trapezoidal keratotomy titrates its effect through variable clear zone size and transverse incision intersects the radial incision.7 The modification of the trapezoidal keratotomy in which the transverse and radial incisions are separated by an isthmus of tissue lessens the disruption of corneal integrity.8

Table

Table 1Patient Characteristics

Table 1

Patient Characteristics

We evaluated the efficacy of a transverse astigmatic keratotomy procedure that was reported by Nordan - transverse incision with an interrupted radial.9 This procedure is quite simple to perform, and the results, especially in reference to the induced and irregular astigmatism are promising.

MATERIALS AND METHODS

We used the technique as proposed by Nordan (Fig I).9 If the meridian of astigmatism does not coincide with a planned radial incision, we rotate the radiais so that one of them will go through the exact meridian of astigmatism in an attempt to correct the myopia and astigmatism in the same meridian (Fig ID). In all the eyes, the surgical astigmatism procedures were adjunctive to the spherical correction of myopia using conventional radial keratotomy.10 Any level of astigmatism equal to or greater than 1.00 D was treated. The nomogram used was similar to the one in Figure 2. All transverse incisions were straight and were done along the 7.00-millimeter zone (Nordan, personal communication). Short incisions were 2.5 mm long, and long ones were 5.00 mm long. Surgery was performed under topical anesthesia with Benoxinate HCl 4%. A Katena sapphire knife was used. Radial incisions were performed eentrifugally from the clear zone to the periphery.

Surgical planning was based on the preoperative cycloplegic refraction along with keratometry readings. Astigmatic correction was performed first. We report a total of 32 keratotomy procedures that were performed using this technique between January 1989 and February 1990. During this time, 32 eyes underwent this procedure. The net surgicallyinduced astigmatism was calculated according to the vector method.11

RESULTS

Thirty-two eyes of 22 patients who underwent jump radial transverse incisions were evaluated (Tables 1-2).

Net Change in Refractive Astigmatism

Analysis of the amount of astigmatism corrected without referring to the axis of the new cylinder. A comparison of preoperative refractive cylinder to the final postoperative refractive cylinder is presented in Fig 3. The results are summarized in Table 3. In the 32 eyes, 87.5% had less than 1.00 diopters of postoperative cylinder. Table 4 shows the mean amount of surgical correction of the preoperative cylinder. The average surgically-corrected (vectoral analysis) astigmatism was 1.55 ± 0.29 D.

Change in Axis of Astigmatism

We analyzed the results with regard to the change in axis of refractive astigmatism that resulted after the operation. This analysis is valuable since one of the main advantages of this procedure is relatively low-induced astigmatism in a different axis than the preoperative one. We omitted from the analysis all the eyes in which the postoperative astigmatism was 0.50 D or less because this amount of astigmatism has no clinical significance and because such a small astigmatism might be within the limit of acceptable refractive measurement. We analyzed the new axis only in the 12 eyes in which it was more than ± 0.50 D of cylinder induced, and calculated the change of the new cylinder axis from the meridian of surgery (Table 5). Only 3 of the 32 eyes operated showed change in the axis between preoperative and postoperative of more than 30° and that 5 out of the 12 eyes showed minimal change in axis of 10° or less. In 3 eyes, microperforations were observed during surgery; all of them sealed spontaneously. Overcorrections and undercorreetions are detailed in Table 2.

Table

Table 2Refractive Results in 32 Eyes That Received Radial and Transverse Keratotomy With Interrupted Radiais

Table 2

Refractive Results in 32 Eyes That Received Radial and Transverse Keratotomy With Interrupted Radiais

DISCUSSION

The results represent evaluation of our current technique for surgical correction of compound myopic astigmatism. We used the technique of interrupted ("jump") radial transverse incisions, as described by Nordan (personal communication, Jeffersonville, Ind, 1989). This procedure, as opposed to others, tries to reduce both the astigmatism and the myopia in the same meridian, attempting to minimize irregular distortion of the cornea as manifested by retinoscopy. A similar concept existed in the early Fyodorov grouped radial (L and RL) procedures, which failed because the multiple incisions were difficult to perform, and the intersecting incisions healed poorly.5 In techniques such as the Thornton and the Flag T, the correction of astigmatism is performed in a different meridian than the incisions for correcting the myopia. The fact that the cornea is untouched in the meridians where no radiais exist enables us to add more radiais (up to 16) in eyes with undercorrection if necessary. Since most of the effect of radial keratotomy is achieved by cutting in the paracentral part of the cornea, we do not think that interrupting the radial cut by the transverse incision reduces the amount of surgical myopic correction. Although we do not present data here on the coupling effect of this procedure, it seems to be 3:1, as in some astigmatic procedures. In our calculations for the myopic correction of these eyes, we assumed this figure of 3:1 which means that for each 3.00 D of flattening of the operated meridian, there was 1.00 D of steepening 90° away. This should be considered when correcting the myopia with radiais, by adding the expected myopia that is induced by the coupling effect to the myopia that was corrected with the radiais.

Table

Table 3Comparison of Preoperative and Postoperative Refractive Astigmatism

Table 3

Comparison of Preoperative and Postoperative Refractive Astigmatism

Figure 3: Comparison of preoperative, postoperative, and refractive astigmatism in 32 eyes using transverse and interrupted radial Incisions. ("Number" In Figure refers to "eye number.")Table 4Surgically-Induced Cylinder Change (Vectoral Analysis) For 32 EyesTable 5Deviation of Surgically-Induced Refractive Cylinder Axis From Axis of Attempted Effect in Eyes With a Postoperative Cylinder of 0.75 D or More (12 Eyes)

Figure 3: Comparison of preoperative, postoperative, and refractive astigmatism in 32 eyes using transverse and interrupted radial Incisions. ("Number" In Figure refers to "eye number.")

Table 4

Surgically-Induced Cylinder Change (Vectoral Analysis) For 32 Eyes

Table 5

Deviation of Surgically-Induced Refractive Cylinder Axis From Axis of Attempted Effect in Eyes With a Postoperative Cylinder of 0.75 D or More (12 Eyes)

The technique that we present here is useful for correcting low to moderate amounts of astigmatism. Since astigmatism of less than 1.00 D, especially if it is "with the rule," is not considered an indication for surgery, we recommend the jump radial cuts technique for the correction of astigmatism in the range of 1.00 to 3.50 D.

Neumann et al12 evaluated the efficacy of three transverse-incision, astigmatic-keratotomy procedures. The methods were; 1) staggered transverse incisions that touched the radial (flag transverse incisions); 2) interrupted transverse incisions that did not touch the radial (Hoffman technique); and 3) transverse incisions with interrupted radial (the procedure described here). They found that nonradial-touching transverse incisions were reasonably effective for reducing the low levels of astigmatism (less than 3.75 D). The mean correction of preoperative astigmatism was 82%. The radial-touching transverse incisions and the interrupted radial transverse incisions were equally effective for reducing over 93% of the preoperative astigmatism, the interrupted radial procedure being the more accurate technique. They concluded that this procedure appears to be the most effective and accurate method to treat astigmatism below 3.75 D. In our series, we did not observe any wound-healing problems with this method as seen by slit-lamp microscopy up to 18 months, probably because we used a maximum of eight radiais. Neumann and colleagues12 reported occasional wound gape of the transverse incisions from neighboring radial incisions with interrupted radial incisions when 16-incision radial keratotomy was performed. The gape diminished with use of an additional 3 to 4 days of patching. Our results support the finding of Neumann and colleagues that correcting compound myopic astigmatism by interrupted radial transverse incisions is effective and accurate.

REFERENCES

1. Sato T. Posterior half-incision of the cornea for astigmatism: operative procedures and results of the improved tangent method. Am J Ophthalmol. 1953;36:462-466.

2. Akiama K, Shibata H, Kanai A, et al. Development of Radial Keratotomy for Myopia and Astigmatism. St Louis, Mo: Mosby- Year Book, Ine; 1991:179-219.

3. Fyodorov SM, Furney VV. Operation of dosaged dissection of corneal circular ligament in cases of myopia of mild degree. Ann Ophthalmol 1979;11:1885-1890.

4. Fenzl RE. Control of astigmatism with corneal incision. In: Sanders DR, Hofmann RF, eds: Refractive Surgery: A Text of Radial Keratotomy. 2nd ed. Thorofare, NJ: SLACK, Incorporated; 1985:115-165.

5. Hofmann RA. The surgical correction of idiopathic astigmatism. In: Sanders DR, Hofmann RF, Salz JJ, eds: Refractive Corneal Surgery. Thorofare, NJ: SLACK, Incorporated; 1986:243-289.

6. Thornton SP, Sanders DR. Graded nonintersecting transverse incision for correction of idiopathic astigmatism. J Cataract Refract Surg. 1987;13:27-31.

7. Leavery GW1 Lindstrom RL. Clinical results of trapezoidal astigmatic keratotomy. Journal of Refractive Surgery. 1985;1:70-74.

8. Terry A, Rowsey JJ. Dynamic shifts in corneal topography during the modified Ruiz procedure for astigmatism. Arch Ophthalmol. 1986;104:1611-1616.

9. Nordan LT. Quantifiable astigmatism correction: concepts and suggestions, 1986. J Cataract Refract Surg. 1986; 12:507518.

10. Ellis W. Radial Keratotomy and Astigmatism Surgery. 2nd ed. Irvine, Calif: Medical Aesthetics, Ine; 1986:9-139.

11. Jaffe NS, Clayman HM. The pathophysiology of corneal astigmatism after cataract extraction. Ophthalmology. 1975;79:615-630.

12. Neumann AC, McCarty GR, Sanders DR, Raanan MG. Refractive evaluation of astigmatic keratotomy procedures. J Cataract Refract Surg. 1989;15:25-31.

Table 1

Patient Characteristics

Table 2

Refractive Results in 32 Eyes That Received Radial and Transverse Keratotomy With Interrupted Radiais

Table 3

Comparison of Preoperative and Postoperative Refractive Astigmatism

10.3928/1081-597X-19920701-07

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