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

Astigmatism control for the cataract surgeon: A comprehensive review of surgically tailored astigmatism reduction (STAR) William F. Malonev, . M.D., Lincoln Grindle, M.D., Donald Sanders, M.D., Ph.D., Donald Pearcv,. 0.0.

AB TRACT pos!>ible for the cahll'uct 'U}'geon to control astigmatism. Ba. ed on a I'C iew of 4 000 con ' cuti e patient!>, tl1l"ec categor'ies of astigmatism and catal'act patients ar identified. p cific approach to a. tigmati. m contl"Ol rO!· each categOl') is di 'cus d. PI'eliminm') results 011 the use of astigmatic keratotom) in conjunction \ ith cataract Slll·gCI·. arc pres nted . It i: increasingl

Ke \Vol·ds: H!>tigmati!>l1l , cataract , in 'isiol\ , h\rat()nwtr~ , h' rat()tol1l~

The cataract incision is the most common refractive procedure performed today. The incision and its closure can have a profound effect on astigmatism and, therefore, the refractive state of the postoperative eye. 1 .:2 .:3 The term iatrogenic astigmatism reminds us that, in the past, this effect has often been detrimental because of corresponding changes in the wound and thus the corneal shape .-1 ,.'5 .6 If the incision leaves the cornea less round (more oval), astigmatism increases. Until relatively recently, the increase in astigmatism was accepted as an unavoidable by-product of cataract surgery.' The benefit of cataract surgery was limited to restoring the vision lost by the lens opacity. The incision, considered as nothing more than a necessary part of that process, was crudely "cut and sewn." Improving the postoperative uncorrected vision was not seriously considered. Several innovations have been changing that perspective. The operating microscope, a variety of improved sutures, a hetter understanding of the relationship between the incision and corneal shape, and, abo\'e alL intraoperative keratometry have resulted in much greater attention to incision details. H.!) Refined

techniques have enabled us to control the incision and thus astigmatism ..5 ./;.1O.11 Rather than merely "cutting and sewing," we can now "tailor" an incision that will compensate for the degree of astigmatism that is present. The incision has become a refractive procedure, capable of permanently and predictably reducing the astigmatic component of the preoperative refractive error. Since the spherical component has been eliminated by increasingly accurate intraocular lens (IOL) calculations , the refractive benefit of modern cataract surgery is becoming increasingly important. Indeed, in patients with a large refractive error, this can outweigh the benefit of the cataract removal itself As we have learned from radial keratotomY, a successful refractive procedure must be highly individualized . Refractive errors vary greatly and so must the proced ures that are designed to correct them. This is as true for the incision and its closure as for radial keratotomy. No single incision will compensate for every patient's astigmatism. The incision appropriate for a spherical eye mllst be altered when it is used in a patient with astigmatism.

Excerpted [citll pCl'missioll from Texthook of Phacoemulsificatioll by ,nlliam F Malolley, M.D .. alld Linculll Grilldle. M.D. , Lasclldo Pllhlishers. Fallhruok , California . Clillical research spollliOred ill part hy a grallt fram IA.TROS (Internatio/la/ Assuciation for Trainillg and Research in Ophthalmic Surgery). Stansstad. S[cif:::er/allll. Presented ill part at the Symposium on Cataract, IOL alld Refractice Surgery. Los Angeles, March 1988. Reprint re1/uests to ,nllia/ll F Ma/oll ey, M. D., 202.3

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This principle has been developed into a comprehensive approach to astigmatic management: surgically tailored astigmatism reduction, referred to as STAR. 1:2(1'p8.5-106) This approach is described in this paper. The obvious goal in astigmatism reduction is a spherical eye postoperatively. The patient who has no astigmatism preoperatively will attain that goal naturally. The appropriate incision for such a patient must leave the corneal shape unaltered . For a patient with preoperative astigmatism, the incision must be altered to reshape the cornea to spherical. Strictly speaking, the STAR approach would use a slightly different incision for every degree of astigmatism but-practically-we are not that accurate. We use three different astigmatism categories as a starting point (Figure 1). With experience, one will be able to subdivide these categories and refine th e STAR approach.

THREE CATEGORIES OF PREOPERATIVE ASTIGMATISM The STAR approach begins by developing an incision and closure to be used in patients who have sphe rical corneas or have insignificant preexisting astigmatism (Category 1). This spherical incision must leave the corneal shape unaltered. For Category 2 patients, the spherical incision is altered to reduce the moderate preexisting astigmatism. Finally, for Category 3 patients, the cornea is directly reshaped with keratotomy incisions to reduce the higher degrees of astigmatism . We emphasize that these techniques build upon one another and must he learned sequentially. It would be unwise, for example, to begin wound

Fig. 1.

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(l\laloney) The three ast igmatism categories. The first group, patients \\-ho are alread\' spherical or who have a clinicalh- insignificant amount of astigmatism , comprise -!4% of our patie nt populatioJl. The second group. patie nts with a mode rate amount of preesisting astigmatism , represent -!7% of th e population. The remaining 9% haye high preesisting astigmatism. The incision and closure differ fiJr each categOlT.

alteration or astigmatic ke ratotom y before mastering the spherical incision . Category One - Th e Spherical Incision The spherical inci sion will ideally leave the corneal shape unaltered. This will not occur automatically for as the wound heals, wound tension subsides, which results in a natural tendency of the vertical corneal meridian to flatten . If an incision is centered at 12 o'clock , a relative increase in against-the-rule astigmatism will res ult. This astigmatism shift , or cylinder regression, is the basis for surgically induced astigmatism. It occurs gradually throughout the healing period, and fo r a given type of incision is quite specific. For the spherical incision to work properly, it must avoid the astigmatism shift or it must accurately compensate for the degree of cylinder regression . The surgeon must know how much the K readings will change as the incision heals. The Cylinder Regressioll Profile. The two incision characteristics that determine the amount of cvlinder regression are the incision size and the inci sio~ architecture . A given comhination of these hlctors will generally result in a specific amount of cylinder regression. Once this amount has been determined, it can be used to predict and accurately compensate for the astigmatism shift. The cylinder regre ssion profile will change if either the size or the architecture of the incision is changed. To he predictable, th ese incision parameters must re main constant. Incision Si:::.e . As the incision size decreases, so does the amount of cylinder regression. One advantage of the small incision IOLs is that the .3 mm incision is too small to change the corneal shape appreciably, no mattenvhat the architecture of the incision. Thus, with a 3 mm incision, a spherical cornea will basically remain spherical. Since this incision avoids the cylinder regression, it is the surest and easiest way to maintain a spherical cornea. An incision that is 3 111m or less is the ideal spherical incision . Larger incisions result in a corresponding increase in the amount of cylinder regression. A 12 mm extracapsular cataract extraction (E CCE ) incision will generally produce twice the amount of regression that a 6 111m phacoemulsification incision will produce, assuming the incision architecture is the same. Converseh ', for a given incision length , c hanges in the parameter~ of the incision architecture will also vary the amount of cylinder regression. Illcision Architecture. The parameters of the incision architecture that affect the cylinder regression are incision location, incision depth , incision le ngth , ty pe of suture used , depth and length of suture hites, suture density, suture tension, and postoperative s teroid dosage.

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There are numerous possihle comhinations of these parameters; no t\vo surgeons will make exactly the same incision. Therefore, it is vital that you know the cylinder regression profile for your specific incision size and architecture. The profile is really a "fingerprint" of the individual surgeon. It is obtained by meas uring the postoperative K readings regularly during the healing pe riod. The change in astigmatism is th en graphically followed over time until the eye is fully healed and the K readings have stopped changing. The difference between the first and the last postoperative K reading is the amount of cylinder regression for that particular incision. For a 6 mm incision, it is usually between two and three diopters ; however, to be accurate , each surgeon must determine this. The surgeon can then predictably compensate for the increase in against-the-rule astigmatism by inducing an equivalent amount of with-the-rule astigmatism at the time of surgery. Thus, a spherical eye will, despite this cylinder regression , heal in a spherical shape. Note that the ability to determine the K reading at the time of surgery is a critical part of this process. It depends on the accurate use of intraoperative keratometrv, which has been described. 12 (pp 107-11U The Krat::. Scleral Pocket In cision. If the incision is 3 111m or less, it is too small to affect the corneal curvature appreciably; the need to compensate for cylinder regression in a spherical eye is avoided. 1:3 The scleral incision, introduced by Kratz, is designed to accomplish the same thing by changing the incision architecture -specifically the location. 1 . 10 If a 6 mm incision (it does not work well for large r incisions) is moved posteriorly, sufficiently far hom the cornea, its effect on corneal curvature and thus the astigmatism is negligible . t-.fany surgeons rely on this approach to

Fig. 2.

preserve the preoperative corneal shape. It is important to emphasize, howeve r, that the advantage of this incision is not that it reduces astigmatism, but rather that it does not change it. Therefore, it is most appropriate only in eyes that are spherical preoperatively. Patients with astigmatism that needs correcting require a diffe rent approach. Suggested SplzericalIncision. Many surgeons prefer a limbal incision . The following is an example of the incision that we use, together with our specific cylinder regression profile for it. Figure 2 shows a spherical incision and closure. Remember, each surgeon must dete rmine his or her own cylinder regression profile. 1. 2. 3. 4. 5.

Incision location: normally at posterior limbus Incision depth: usually one-half scleral depth Incision length: 6.0 mm Type of suture used: 9-0 D epth and length of suture bite: bottom of groove and approximately 1 mm from wound edges 6. Suture density: 4 times continuous 7. Suture tension: enough to match the cylinder regression profile 8. Postoperative steroids: 4 tim es a day for 3 weeks Catego ry 2 - Astigmatism Reduction Patients in Category 2 have a moderate amount of astigmatism (1.0 to 2.5 diopters [D]). To correct this astigmatism, the corneal shape must be changed so that both corneal meridians focus at the same plane. Therefore, the spherical incision does not properly fit this group of patients and must be altered. Altering the incision is much more than just changing the tension on the knot: To hm'e apermanent and predictable effect, it is necessary to alter the architecture of th e incision by changing one or more of the parameters.

(r-.laloney) The spherical incision (left ) and closure (right), which are designe d to leave the corneal shape unaltered.

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Patients in Category 2 may have with-the-rule or against-the-rule astigmatism. In both, the cornea is not round - but in opposite directions. In with-the-rule astigmatism, the vertical meridian is steeper than the horizontal; in against-the-rule astigmatism it is the opposite. Thus, the wound alterations to correct withthe-rule astigmatism will be different from those to correct against-the-rule astigmatism. We shall consider them separately. With-the-Rllie Astigmatism Alterations. The incision alteration to correct with-the-rule astigmatism will primarily affect the vertical meridian. To flatten the vertical meridian, the appropriate incision alteration is to loosen or "let out" the wound. So, to correct withthe-rule astigmatism, loosen the wound to flatten the vertical meridian (Figure 3). As we have said, to alter the incision permanently, it is insufficient to tighten or loosen the suture. The architecture itself must be changed, which can be done in the following way: 1. Incision location: move posteriorly 2. Incision depth: more shallow, one-half to one-fourth depth 3. Incision length: lengthen slightly, 6.5 to 7.5 mm 4. Type of suture used: 10-0 .5. Depth and length of suture bites: bottom of groove which is now more shallow, bites shorter, approximately 0.5 mm from wound edges 6. Suture density: fewer suture passes, 3 or 4 times continuous 7. Suture tension: loosen to reduce your cylinder regression profile 8. Postoperative steroids: increase dosage 1. Location of Incision. Moving the incision posteriorly does not, in itself, have a loosening effect. It

does, however, increase the distance that the two sides of the incision overlap, creating a self'sealing, flapvalve closure that is often watertight without sutures. This posterior repositioning gives the flexibility to change the other parameters and considerably loosen the wound without having it leak. 2. Depth of Incision. A shallow groove is the most important parameter in loosening the incision. With the incision moved posteriorly as mentioned above, a one-fourth or even a one-fifth thickness groove is possible. As a shelf is created at this depth, the corneal side of the incision is thin enough to retract or recess considerably from its original l~)cation, automatically loosening the incision. 3. Length ofIncision. Increasing the incision size can enhance the effect of with-the-rule astigmatism incision alterations. Loosening a slightly larger incision has the effect of flattening the vertical meridian. This is generally reserved for relatively high degrees of \viththe-rule astigmatism (2.0 to 2.5 D). 4. Type of Suture. A thin suture does not maintain its tension on the tissue as long as a thicker one and results in incision loosening. 5. Suture Bites. Shallower and shorter suture passes encourage incision loosening because they do not reapproximate the tissue as effectively, encouraging the two edges of the incision to recess. 6. Suture Density. If fewer sutures are placed, the edges of the incision are, again, less well approximated, allowing the incision to loosen more. 7. Suture Tension. Once in place, the looser the suture is tied, the less approximated the incision edges will be and the looser the incision will heal. It is important to reemphasize that the suture tension alone will not have a permanent effect without other changes in the incision architecture.

Fig. 3.

J CATARACT REFRACT SURG-YOL 1.5, JANUARY 1989

(r-.laloney) Incision (hIt) and closure (right) for 2 ..50 of preexisting with-th~-rule astigmatism. This incision is shallower than the spherical incision; the groove is larger, the suture bites shallower, and the suture tied more loosely.

8. Postoperative Steroids. Since steroids inhibit wound healing, increasing the steroids during the postoperative period will encourage loosening. One or all these incision architectural parameters can be altered, depending upon the amount of withthe-rule astigmatism to be corrected.

Against-the-Rllle Astigmatism Alterations. To correct the steeper horizontal meridian in against-therule astigmatism, changes in architecture parameters opposite to those in with-the-rule astigmatism are needed (Figure 4). l. Incision location: move anteriorly 2. Incision depth: deeper, up to three-fourths depth 3. Incision length: 6.0 mm 4. Type of suture used: 9-0 5. Depth and length of suture bite: bottom of groove which is now deeper, bites are longer, approximately l.5 mm from wound edges 6. Suture density: more suture passes, 4 to 5 times continuous 7. Suture tension: tighten to increase your cylinder regression profile 8. Postoperative steroids: decrease dosage l. Location ofIncision. Move the incision anteriorly so that there will be more tissue for the suture to pull on and tightening will have more corneal effect. 2. Depth ofIncision. Make the incision deeper, up to three-fourths of the scleral depth, so there are more substantial tissue edges to maintain the tightening effect. 3. Length of Incision. Shortening the standard length has no effect, so use the 6.0 mm incision. 4. Type of Suture. Use a larger (9-0) suture for more lasting tension on tissue.

Fig. 4.

5. Suture Bites. Longer bites have more tissue within them so that tightening will have a more permanent effect. 6. Suture Density. If more sutures are placed, the incision edges will be approximated more, which encourages more tightening. 7. Suture Tension. Increase tension. If the normal cylinder regression is, for example, 2.0, increase tension to a keratometer reading of 2.5 to 3,5, as indicated. 8. Postoperative Steroids. Fewer steroids postoperatively will encourge wound healing and leave it tighter. Category .3- Redllcing High Astigmatism Appropriate alterations of the spherical wound are effective in changing the shape of the cornea and correcting moderate amounts of preoperative astigmatism. However, this indirect corneal reshaping is insufficient to correct more than 2.5 D of preoperative astigmatism.,5,12(ppll,5-106) The significant amount of corneal reshaping required to correct high degrees of preoperative astigmatism must be done directly-on the cornea itself. Astigmatic Keratotomy. We have learned from radial keratotomy that incisions in the cornea (keratotomy incisions) can profoundly reshape it. In radial keratotomy, the incisions are designed to flatten the entire cornea uniformly. Astigmatic keratotomy, a variation of radial keratotomy, uses corneal incisions to flatten the cornea selectively. In this manner, astigmatic keratotomy can flatten the steeper meridian sufficiently to coincide with the other meridian, thus making the cornea more spherical. 12 ,(ppR.5-106)l4,1.5 A word of caution is warranted here. Astigmatic keratotomy has been used in conjunction with radial

(Maloney) Incision (left) and closure (right) fi)r 1.5 D of preexisting . against-the-rule astigmatism. The incision is deeper and more anterior than the preceding one.

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keratotomy, generally with unpredictable results. There are a variety of reasons for this; most important is that keratometry was not used to measure the intraoperative results. Often, more incisions than necessary were used. Since the keratotomy incision can have a profound effect on the corneal shape, large overcorrections frequently resulted. We have adapted astigmatic keratotomy so that it can be performed in conjunction with phacoemulsification in these Category 3 patients. As will be seen, intraoperative keratometry is a vital part of the process. If this technique is followed carefully, it will not interfere with the phacoemulsification and will yield predictable results. Combined Astigmatic Keratotomy and Phacoemlllsification. In general, this combined procedure involves three phases: 1. The majority of the astigmatism is first corrected with astigmatic keratotomy. The results of the keratotomy incision are far more reliable if it is done prior to the corneoscleral phacoemulsification incision. 2. Routine phacoemulsification and IOL implantation are performed. 3. Residual astigmatism (slight overcorrections or undercorrections from the keratotomy) is corrected by incision alteration as described in Category 2. From this general overview, we will discuss each of the steps. 1. Confirm the degree and the axis of astigmatism. The cylindrical keratometer will provide a clear image of the corneal shape-particularly with astigmatism of this degree. For example, with against-the-rule astigmatism, the steep axis will be 180 degrees and the shorter diameter of the oval will be in the horizontal meridian. Examine the image closely because it is the basis for determining how many keratotomy incisions you will perform. As keratotomy progresses incrementally, this image will change until it becomes nearly round, indicating a spherical cornea. Occasionally the steeper axis is oblique. In these cases, this visual image is particularly helpful in maintaining the proper orientation. 2. Mark the steep axis. Once the steep axis has been identified, align the axis marker so that it coincides exactly with the shorter diameter of the oval, gently indent the epithelium along this axis and mark it (Figure 5). 3. Mark the optical zone. Center a standard 7 mm optical zone marker on the cornea by visibly measuring an equal amount of distance between the optical zone marker and the limbus in all four quadrants (Figure 6). Unlike radial keratotomy, the central visual axis is not marked, since disruption of the central epithelium could obscure 50

Fig . .5.

(Maloney) The axis marker is aligned with the shorter diameter of the o\al, thus marking the steep axis.

visualization during phacoemulsification, as well as during the subs~quent keratotomy. 4. Mark the incision locations. Center the incision marker perpendicular to the axis mark where the optical zone mark and the axis mark intercept (Figure 7). A pair of incisions each 3 m111 long and 1 111m apart is marked. Repeat the process at the opposite side of the cornea. 5. Using the ultrasonic pachymeter, measure the corneal depth at each of the two internal incision marks (Figure 8). Use the hIll corneal depth measured (100% or zero bias) to set a front-cutting diamond blade for each incision. This 100% blade setting will actually result in an incision depth of 90% to 95% (this is true only for a front-cutting blade).

Fig. 6.

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(Maloney) The optical zone marker is centered on the cornea.

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(Maloney) The incision ma rke r is centered perpendicular to the axis mark at the point ,,·he re the optical zone mark and the axis mark inte rcept .

6. For the keratotomy incisions, orient the frontcutting blade at the far end of one of the more ce ntral incision marks to cut toward you (Figure 9). After setting the blade in the cornea, make a mental note of the length and course of the incision, then have an assistant place a drop of balanced salt solution on the cornea in the path the incision is to take. This will prevent epithelial drag and inadvertent abrasion , which could interfere with the subsequent keratom etric readings. Repeat the process for the opposite incision, changing the blade depth . 7. Use the keratometer to meas ure the change in the keratoscopic image and thus the change in the corneal curvature resulting from the first pair of incisions. The effect will vary widely, depending upon the patient's age and other factors; therefore, this keratometric readin g is essential. If this measurement indicates that there is still significant as tigmatism (more than 1.0 D), repeat the process, beginning with ultrasonic pachymetry for the second, more peripheral, pair of incisions. Since

Fig. 9.

(Maloney) The h'ratotmll\' II1CISlOn is made with the front-cntting blade se t to the full measured corneal de pth.

J CATARACT

Fig. 8.

(r..laloney) The ultrasonic pachymeter measures the corneal thickness at each incision.

these incisions are 1 mm apart, the effective optical zone is now 8 mm . The need for th e additional incisions is especially common in younger patients, those with high degrees of astigmatism, or those who, for unknown reasons, respond less to the keratotom y incision. Again , it must be emphasized that the second pair of incisions should be performed only if the intraoperative keratotomy has indicated more than 1.0 D of residual astigmatism . After the second pair of incisions has bee n made at the 8 mm optical zone, use the keratometer to read the incremental change in astigmatism . In rare cases, significant astigmatism will still be present and require more correction. This is done by making two radial incisions on either side of the transverse incisions, being sure they do not connect. 8. After the radial incisions, measure the K readings once again. Be sure to note this reading before making the phacoemllisification incision, since the amount of astigmatism remaining at this point will determine how the incision and its subsequent closure is pe rfi>rmed (see step 10). 9 . After astigmatic keratotomy is comple ted , the phacoemulsification incision can be made. In pure with- or against-the-rule astigmatism , with the axis at 90 degrees or 180 degrees, the incision should be centered at 12 o'clock. If keratometry has demonstrated ohlique astigmatism, the center of the incision can be rotated to align more directly with the astigmatic axis, enhancing the effect of suhsequent incision alteration. 10. The parameters for the phacoemulsification incision are determined by the keratometry reading of the corneal astigmatism present after the fin al astigmatic keratotomy incisions have been made. For example , if the original K reading was 4.0 D

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against-the-rule and 1.0 D against-the-rule remains after the final astigmatic keratotomy inci- . sion, keratotomy was responsible for eliminating 3.0 D of against-the-rule astigmatism. The remaining 1.0 D c~m be corrected by incision alteration. Thus, 1.0 D against-the-rule is the "new" K reading, which determines the parameters of the phacoemulsification incision and its closure. In essence, at the end of the phacoemulsification procedure , the incision is altered to enhance the effect of astigmatic keratotomy, if necessary, or to counteract a slight overcorrection. Incision alteration is very useful in fine tuning the final effect of astigmatic keratotomy. It is, however, important to note that the corneal curvature changes much less during the healing period after astigmatic keratotomy has been performed than with incision alteration alone. In other words, there is very little, if any, natural cylinder regression after astigmatic keratotomy. Therefore, the cylinder regression factor should not be used when considering the suture tension in cases in which astigmatic keratotomy has been performed.

PRELIMINARY REPORT OF ASTIGMATIC KERATOTOMY RESULTS We have had experience with astigmatic keratotomy performed in combination with phacoemulsification in approximately 200 patients . This experience began in 1984; initially results were unpredictable. There were several large overcorrections. Shortly thereafter, we began using the Maloney intraope rative keratometer to obtain an immediate, intraoperative assessment of the effect on the corneal curvature of the initial pair of keratotomy incisions. We found many patients who , according to the preoperative nomogram, should have required two pairs of incisions for adequate correction but did not need the second pair. The intraoperative keratometer demonstrated that the astigmatism was fully corrected by the initial pair of incisions. In this manner, the incidence of overcorrection was significantly reduced and intraoperative keratometry became an integral part of the astigmatic keratotomy procedure . Astigmatic keratotomy is still relatively new and not yet widely performed. Clearly, more data are needed to determine its role in reducing postoperative refractive error in cataract patients. We have been conducting a retrospective analysis of200 consecutive patients, the preliminary results of which are reported. Retrospective analysis of clinical data has certain flaws, however. Therefore , we are also in the process of conducting a randomized prospective study of the effectiveness of astigmatic keratotomy and wound manipulation, with and without intraoperative keratometry. Until the results of that study are known , 52

Fig. 10.

(Maloney) First p air of k eratotomy incisions. The incisions are made and th e n keratometry is done to measure the effect.

astigmatic keratotomy should , in our opinion, be considered an experimental procedure. Single Pair Incisions Fifty-five (55) eyes received a single pair of astigmatic keratotomy incisions (Figure 10). The age of these patients ranged from 52 to 95 years, with a mean age of 79.1 years. Sixty-nine percent (69%) of the patients were female , 31 % male. These data include the most recent follow-up visit for each patient, which ranged from 0.25 to 12.5 months , with a mean followup of 2.6 months. Figure 11 shows the distribution of preoperative and postoperative (final available visit) cylinder by half and single diopter increments. There is a definite shift from large preoperative cylinder values to lower postopera-

60%

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0-.4110 .5-.11110 1-1.4110 1.5-1.SISIO 2-2.11110 -OR-SO

CYLINDER - D Fig. 11.

(Maloney) Distrihution of preoperative and postope rative diopter cylinde r "allles at final available visit for patients who received a single pair of astigmatic ke ratotomy incisions (preliminary datal.

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Fig. 12.

(Maloney) Scatterplot of preoperative versus postoperative cylinder values for patients who received a single pair of astigmatic keratutollH" incisions (preliminary data).

Fig. 13.

(Maloney) Second pair of keratotomy incisions. If keratometry indicates that significant astigmatism still exists, the second pair of incisions are made .

tive cylinder values. Preoperati vely, only 4% of the cases had less than 1 D of cylinder, while postoperatively, 53% had less than 1 D of cylinder. Sixty percent (60%) had 1 D to 2 D of cylinder preoperatively, while 32% had 1 D t o 2 Dof cylinder postoperatively. Thirty-six percent (36%) of the cases had more than 2 D of cylinder preoperatively, while only 15% had more than 2 D of cylinder after surgery. Figure 12 is a scatterplot of preoperative and postoperative cylinder values. The majority of cases had a decrease in actual cylinder after astigmatic keratotom y. The majority of those who had an increase were the earl y overcorrections.

age of77.5 years. Fifty-six percent (56%) of the patients were fe male, 44% male . Follow-up time ranged from 0.5 months to 20.25 months with an average follow-up of 5.2 months. Figure 14 shows the preoperative and postoperative (final available visit) cylinder distribution. The majority of cases (87%) had 1.5 D or more cylinder values preoperatively; 72% of the cases had 1.5 D or less of cylinder postoperatively. Whereas 3% of these patien ts had less than 1.0 D of cylinder values preoperatively, 54% had less than 1.0 D of cylinder postoperatively. Figure 15, the scatterplot of preoperative versus postoperative cylinder values, reflects this reduction.

nco Pair Incisions

Mini Ruiz Another series of patients received two pairs of astigmatic keratotomy incisions combined with small adjacent radial incisions at either end -a so-called

One hundred eight (108) eyes received two pairs of astigmatic keratotomy incisions (Figure 13). The patients had an age range of 54 to 97 years, with a mean

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(Malolley) Distribution of preoperative and postoperative diopter cylinder values at final available visit for patients who received two pairs of astigmatic keratotomy incisions (preliminary data).

J CATARACT

DECREASE

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Fig. 1.5.

(r..-lal on e~-) Scatterplot of preoperative versus postoperative cylinder values for patients receiving tv.'o pairs of astigmatic keratotomy incisions (preliminary data).

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0-.490 .5-.990 1-1.490 1.5-1.9902-2.990 -OR-3D

CYLINDER - D Fig. 16.

(Maloney) Radial incisions. Ifa patient shows significant residual astigmatism even after the second pair of keratotomy incisions. two pairs of radial incisions are added.

mini Ruiz (Figure 16). The series included 15 eyes from patients whose ages ranged from 64 to 88 years. The mean age was 78.7 years. Twenty-seven percent (27%) of these patients were female, 73% male. Follow-up in this category ranged from 0.5 months to 16.25 months, with a mean follow-up of 3.6 months. Figure 17 is a distribution of preoperative and postoperative (last available visit) cylinder based on the mini Ruiz data. The preoperative cylinder values are substantially higher than those in the two pair and single pair data. Eighty-seven percent (87%) of the cases had 2.0 D or more of cylinder preoperatively. Postoperatively, 46% of the cases had less than l.0 D of cylinder, 33% had between l.0 D and 2.0 D, and on Iv 2i % had more than 2.0 D of cylinder. Figure 18 is :1

B.O

VI 0::

7.0

w f-

a.

6.0

e

5.0

W

4.0

0

0::

0

z ::J >u a. 0

w

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a.

DECREASE 0

3.0

0

8

0 0

0

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0

00

2.0

INCREASE

00

1.0 0.0 0.0

1.0

2.0

3.0

4:.0

5.0

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POSTOP CYLINDER (DIOPTERS)

Fig. 18.

.54

(~laloney) Scatterplot of preoperative versus postoperative cylinder values for patients receiving the mini-Ruiz configuration of astigmatic keratotomy incisions (preliminary data).

Fig. 17.

(~Ialoney) Distribution of preoperative and postoperative diopter cylinder values at final available visit fin' patients receiving mini- Ruiz configuration of astigmatic keratotomy incision (preliminary data).

scatterplot of preoperative versus postoperative cylinder values. All patients in this category had a reduction in the degree of preexisting astigmatism. REFERENCES 1. Kratz RP, Johnson SH: Clinical results with the surgical keratometer. lilt Ophtlwlmol eli II 23(-1):B7-99. 1983 2. Cravy TV: Modification of postcataract astigmatism by wound revision. lilt Ophtlwlmol elill 23(-1Ul1-126, 19B.3 3. Bechetoille A. Leclair E, Jallet G, Girard E: Un procede simple de cure (l'astimatisme apres intervention de cataracte. Bull Soc Ophtalmol Fr 8-1:1269-1272. 198-1 -1. Barner SS: Surgical induction of corneal astigmatism. An experimental study. Albrecht fOil Graefe.l· A.rch Klill Exp Ophthalmol 201:21.3-220, 1977 ,5. Jacobi KvV, Strobel J: Control of postoperative astigmatism. TrailS Ophtlwlmol Soc UK 10-1:71.5-726. 198.5 6. Reading V~l: Astigmatism following cataract surgery. Br ] Ophthalmol 68:97-10-1. 198-1 7. Gorn RA: Surgically induced corneal astigmatism and its spontaneous regression. Ophthalmic SII rg 16: 162-16-1, 198.5 8. Bambery SJ: Reduction of astigmatism foll()\\"ing cataract surgery. TrailS Ophtlwllllol Soc UK 10.5:6-17-6-19. 1986 9. Samples JR. Binder PS: The value of the Terry keratometer in predicting postoperative astigmatism. Ophthalmology 91: 280-28-1, 198-1 10. Thrasher BH. Boerner CF: Control of astigmatism hy wound placement. Am Illtra-Ocular Implallt Soc] 10:176-179. 198-1 11. ~Iasket S: Nonkeratometric control of postoperative astigmatism. Am Illtra-Oclilar Implallt Soc] 11:1:3-1-1:37, 198.5 12. ~1aloney VV, Grindle L: Textbook of Plwcoemllisificatioll, Fallbrook, CA. Lasenda Publishers. 1988 13. Lindstrom RL, Destro ~IA: Effect of incision size and Terrv keratometer usage on postoperative astigmatism. Am Illtn;oClilar Implallt Soc] 11:-169--17.3. 198,5 U. Thornton SP, Sanders DR: Graded nonintersecting transverse incisions for correction of idiopathic astigmatism. ] Cataract Refract Sllrg 13:27-.31, 1987 1.5. Fedorov SN. Ivashina AI. Gudechkov VB: Surgical correction of astigmatism by means of anterior non-perforating keratotomy. \btll Oftallllol no. 3:16-18. 198-1

J CATARACT REFRACT SURG-YOL

1.5. JANUARY 1989