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The surgical correction of postoperative astigmatism by wound revision
the surgical correction of postoperative astigmatism by wound revision Thomas V. Cravy, MD. Santa Maria, California
Excessive postoperative astigmatism after cataract extraction may result from either an ectatic or a cicatricial surgical incision. The ectatic incision follows premature suture absorption or removal causing the wound to gape or become ectatic. The cicatricial incision occurs if tight sutures are left in place until the wound is substantially healed; when sutures are finally removed, there is no significant change in astigmatism. Although excessive postoperative astigmatism following cataract extraction is relatively rare, it may be as optically debilitating as the original cataract. Troutman! describes a technique of wedge resection to correct high postoperative astigmatism, which has met with only moderate success. Herein are described the technique and results of a single surgical approach to the treatment of both types of postoperative astigmatism. The cataract incision is reopened and reclosed under keratometric control to produce a redistribution and equalization of tension upon the cornea.
SUBJECTS AND METHODS Of approximately 75 patients undergoing astigmatism correction, eight met the criteria for inclusion in this study. These criteria were: 1) a history of previous cataract surgery resulting in postoperative astigmatism of not less than 6 diopters by keratometry; 2) a minimum one-year follow-up; and 3) surgery performed solely for the correction of excessive astigmatism, without additional procedures. Although the last criterion limited eligibility, it also reduced the number of indeterminate variables which might bias the study's results. Of the eight patients, six were pseudophakes. Preoperative astigmatism was quantitated by keratometry and refraction. Dynamic keratoscopy2 was used to monitor the entire corneal contour, from
periphery to apex, and precisely locate areas of abnormal wound healing causing high and often irregular astigmatism. Surgery was performed under an operating microscope equipped with an operating keratometer. A fornix-based conjunctival flap was centered over the central meridian of the previous surgical incision, generally at the 12-o'clock position. Bleeding vessels were cauterized with bipolar cautery. The old ectatic or cicatricial incision was reopened. The anterior chamber was entered with a razor-blade knife, and the incision was enlarged with curved corneoscleral scissors. Air was used in the anterior chamber to protect the corneal endothelium. The endothelial edge was identified so that a full-thickness closure could be performed using a 10-0 polypropylene (Prolene) shoelace suture, loosely tensioned and tied under keratometric control. Additional interrupted 10-0 nylon compression sutures were strategically placed so that steepening in any meridian could be corrected postoperatively by removing one or more tight sutures. All sutures were full-thickness and vertically oriented to prevent suture drag or "cheese wiring."3 Tensioning and tying were done under keratomehic control to produce a spherical cornea. If the flat meridian of the cornea did not lie within the corneal incision, a half-thickness, clear corneal incision was precisely centered across the meridian, and one or more compression sutures were placed to counterbalance ,the keratometric reflex. The object of the closure was to balance the forces upon the cornea during healing. Beginning at eight weeks postoperatively, overly tight interrupted sutures (as determined by dynamic keratoscopy) were removed one by one until a desirable astigmatic result was obtained. About six months after surgery the remaining interrupted sutures were removed. The polypropylene shoelace suture was left intact indefinitely to ensure wound integrity.
Presented at the American Intra-Ocular Implant Society's Fifth Academy Program in San Francisco, November 1979, Reprint requests to Dr, Cravy, 616 East Chapel, Santa Maria, CA 93454, 160
AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
13
PREOP
. (+ 12.50
x 064·)
12 11
10
9 8
RESULTS AND DISCUSSION Results are shown in Table 1. In most cases, reopening of the cataract wound combined with carefully engineered full-thickness closure performed under keratometric control produced immediate and stable reduction of astigmatism (Figs. 1-4). In no case was corneal tissue excised. Figs. 5 and 6 represent the two earliest cases, which received only interrupted sutures. Both eyes had ectatic incisions attributable to impaired wound healing. Subsequent cases were reinforced with a shoelace suture to provide long-term wound support and allow safe removal of compression sutures.
7
6
5 4
3 2
0 I 0
1
,
p
T E R
S
0
3
6
-1
12
MONTHS
-2 -3
Fig. 1 (Cravy). Keratometric decay curve for Case #8. The y-axis records the change in astigmatism (Ks)4 after surgical correction. Compression sutures were removed eight weeks postoperatively (hatch marks) and the degree of astigmatism had stabilized by the twelfth postoperative week.
Table 1. Pre- and postoperative visual acuity and astigmatism for eight patients undergoing surgical correction of excessive astigmatism after previous cataract removal. Case #
Age (years)
1 2t
70 70
3:j: 4:j: 5 6t 7t 8
80 87 59 87 74 72 Mean 74.9 S.D. :±:9.5
Best Corrected Visual Acuity Pre-op Post-op
20/60 Counting fingers at 10 ft. 20170 (pinhole) 20/60 20/200 20/200 20/60 20/100
Pre-op Astigmatism*
Follow-up Time (years)
Post-op Astigmatism at end of Follow-up*
Total COfrection (diopters)
Percentage Corn~c-
tion**
20/25 20/40
+7.00 x 007° +8.75 x 108°
3.14 2.17
+ 1..50 x 016° + l.50 x 088°
5.52 7.36
79 84
20/20 20/25 20/20 20/200 20/30 20115
+7.50 x OOT +8.25 x 003° +6.62 x 010° +9.12 x 020° +7.00 x 172° + 12.50 x 064° +8.34 :±: l.90
2.03 2.53 2.73 1.()7 2.7.3 l.02 2.18 ±0.78
+ l.00 x 146° +3.88 x 178° +0.88 x 085° + l.12 x 003° +0.25 x 086° +0.88 x 090° + 1..37 ± l.08
6.78 4.40 6.4.5 8.06 6.99 11.72 7.16 ±2.16
90 .53 97 88 100 94 87 ± 1.5
*Determined by quantitative keratometry. **Equal to the total correction divided by the preoperative astigmatism. tSenile macular degeneration :j:Aphakic AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
161
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-4 -5
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-.
-.
PREOP -7
.(+9.12 x 020·)
.(+7.00 x 001·)
Fig. 5 (Cravy). Compressed-scale keratometric decay curve for Case # 1, which was undercorrected after astigmatism surgery, shows gradual spontaneous reduction in the amount of residual astigmatism. No sutures were removed.
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Fig. 2 (Cravy). Keratometric decay curve for Case #6. The hatch marks indicate removal of compression sutures.
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-2
Fig. 3 (Cravy). Keratometric decay curve for Case #5. The hatch marks indicate removal of compression sutures.
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Fig. 6 (Cravy). Compressed-scale keratometric decay curve for Case #4 shows that the patient was still significantly overcorrected 14 weeks after astigmatism surgery. Subsequent removal of the last interrupted suture was immediately followed by wound gape with formation of a filtering bleb and more than a 7-D change in astigmatism. The hatch marks indicate removal of compression sutures.
+(+7.50 . 007·)
Fig. 4 (Cravy). Keratometric decay curve for Case #3. No sutures were removed. 162
AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
Because of its characteristic late hydrolysis in situ, nylon suture was not used for the shoelace closure. The polypropylene shoelace sutures displayed enduring tensile strength and the ability to readjust tension following interrupted suture removal. Eventual absorption of unremoved nylon interrupted sutures did not affect astigmatism (Fig. 4). Serial photokeratographs and keratometry were used to evaluate corneal astigmatism and objectively document the effects of surgery (Fig. 7, 8). This technique was not associated with any complications and was equally effective for ectatic and cicatricial cataract incisions.
Fig. 8 (Cravy). Photokeratograph of Case #8 taken one year after surgical correction of a cicatricial cataract wound. At the top of the photo is the net postoperative astigmatism, as measured by quantitative keratometry.
REFERENCES 1. Troutman RC: Microsurgical control of corneal astigmatism in
Fig. 7 (Cravy). Photokeratograph of Case #8 prior to surgical correction of a cicatricial cataract wound. At the top of the photo is the net preoperative astigmatism, as measured by quantitative keratometry.
cataract and keratoplasty. Trans Am Acad Ophthalmol Otolaryngol 77:563, 1973 2. Cravy TV: The Cravy operating keratometer, in Emery JM (ed): Current Concepts in Cataract Surgery. St Louis, CV Mosby Co, in press 3. Cravy TV: A modified suture placement technique to avoid suture drag or "cheese wire" effect. Ophthalmic Surg, in press 4. Cravy TV: Calculation of the change in corneal astigmatism following cataract extraction. Ophthalmic Surg 10:38, 1979
AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
163
Excessive postoperative astigmatism after cataract extraction may result from either an ectatic or a cicatricial surgical incision. The ectatic incision follows premature suture absorption or removal causing the wound to gape or become ectatic. The cicatricial incision occurs if tight sutures are left in place until the wound is substantially healed; when sutures are finally removed, there is no significant change in astigmatism. Although excessive postoperative astigmatism following cataract extraction is relatively rare, it may be as optically debilitating as the original cataract. Troutman! describes a technique of wedge resection to correct high postoperative astigmatism, which has met with only moderate success. Herein are described the technique and results of a single surgical approach to the treatment of both types of postoperative astigmatism. The cataract incision is reopened and reclosed under keratometric control to produce a redistribution and equalization of tension upon the cornea.
SUBJECTS AND METHODS Of approximately 75 patients undergoing astigmatism correction, eight met the criteria for inclusion in this study. These criteria were: 1) a history of previous cataract surgery resulting in postoperative astigmatism of not less than 6 diopters by keratometry; 2) a minimum one-year follow-up; and 3) surgery performed solely for the correction of excessive astigmatism, without additional procedures. Although the last criterion limited eligibility, it also reduced the number of indeterminate variables which might bias the study's results. Of the eight patients, six were pseudophakes. Preoperative astigmatism was quantitated by keratometry and refraction. Dynamic keratoscopy2 was used to monitor the entire corneal contour, from
periphery to apex, and precisely locate areas of abnormal wound healing causing high and often irregular astigmatism. Surgery was performed under an operating microscope equipped with an operating keratometer. A fornix-based conjunctival flap was centered over the central meridian of the previous surgical incision, generally at the 12-o'clock position. Bleeding vessels were cauterized with bipolar cautery. The old ectatic or cicatricial incision was reopened. The anterior chamber was entered with a razor-blade knife, and the incision was enlarged with curved corneoscleral scissors. Air was used in the anterior chamber to protect the corneal endothelium. The endothelial edge was identified so that a full-thickness closure could be performed using a 10-0 polypropylene (Prolene) shoelace suture, loosely tensioned and tied under keratometric control. Additional interrupted 10-0 nylon compression sutures were strategically placed so that steepening in any meridian could be corrected postoperatively by removing one or more tight sutures. All sutures were full-thickness and vertically oriented to prevent suture drag or "cheese wiring."3 Tensioning and tying were done under keratomehic control to produce a spherical cornea. If the flat meridian of the cornea did not lie within the corneal incision, a half-thickness, clear corneal incision was precisely centered across the meridian, and one or more compression sutures were placed to counterbalance ,the keratometric reflex. The object of the closure was to balance the forces upon the cornea during healing. Beginning at eight weeks postoperatively, overly tight interrupted sutures (as determined by dynamic keratoscopy) were removed one by one until a desirable astigmatic result was obtained. About six months after surgery the remaining interrupted sutures were removed. The polypropylene shoelace suture was left intact indefinitely to ensure wound integrity.
Presented at the American Intra-Ocular Implant Society's Fifth Academy Program in San Francisco, November 1979, Reprint requests to Dr, Cravy, 616 East Chapel, Santa Maria, CA 93454, 160
AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
13
PREOP
. (+ 12.50
x 064·)
12 11
10
9 8
RESULTS AND DISCUSSION Results are shown in Table 1. In most cases, reopening of the cataract wound combined with carefully engineered full-thickness closure performed under keratometric control produced immediate and stable reduction of astigmatism (Figs. 1-4). In no case was corneal tissue excised. Figs. 5 and 6 represent the two earliest cases, which received only interrupted sutures. Both eyes had ectatic incisions attributable to impaired wound healing. Subsequent cases were reinforced with a shoelace suture to provide long-term wound support and allow safe removal of compression sutures.
7
6
5 4
3 2
0 I 0
1
,
p
T E R
S
0
3
6
-1
12
MONTHS
-2 -3
Fig. 1 (Cravy). Keratometric decay curve for Case #8. The y-axis records the change in astigmatism (Ks)4 after surgical correction. Compression sutures were removed eight weeks postoperatively (hatch marks) and the degree of astigmatism had stabilized by the twelfth postoperative week.
Table 1. Pre- and postoperative visual acuity and astigmatism for eight patients undergoing surgical correction of excessive astigmatism after previous cataract removal. Case #
Age (years)
1 2t
70 70
3:j: 4:j: 5 6t 7t 8
80 87 59 87 74 72 Mean 74.9 S.D. :±:9.5
Best Corrected Visual Acuity Pre-op Post-op
20/60 Counting fingers at 10 ft. 20170 (pinhole) 20/60 20/200 20/200 20/60 20/100
Pre-op Astigmatism*
Follow-up Time (years)
Post-op Astigmatism at end of Follow-up*
Total COfrection (diopters)
Percentage Corn~c-
tion**
20/25 20/40
+7.00 x 007° +8.75 x 108°
3.14 2.17
+ 1..50 x 016° + l.50 x 088°
5.52 7.36
79 84
20/20 20/25 20/20 20/200 20/30 20115
+7.50 x OOT +8.25 x 003° +6.62 x 010° +9.12 x 020° +7.00 x 172° + 12.50 x 064° +8.34 :±: l.90
2.03 2.53 2.73 1.()7 2.7.3 l.02 2.18 ±0.78
+ l.00 x 146° +3.88 x 178° +0.88 x 085° + l.12 x 003° +0.25 x 086° +0.88 x 090° + 1..37 ± l.08
6.78 4.40 6.4.5 8.06 6.99 11.72 7.16 ±2.16
90 .53 97 88 100 94 87 ± 1.5
*Determined by quantitative keratometry. **Equal to the total correction divided by the preoperative astigmatism. tSenile macular degeneration :j:Aphakic AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
161
3
2
0 I
JIOftIII
1
0 p T
9
6
0
E R
-1
S
-2 o
-3
I
o
P T E R -1 S
-4 -5
-J
-.
-.
PREOP -7
.(+9.12 x 020·)
.(+7.00 x 001·)
Fig. 5 (Cravy). Compressed-scale keratometric decay curve for Case # 1, which was undercorrected after astigmatism surgery, shows gradual spontaneous reduction in the amount of residual astigmatism. No sutures were removed.
"
T
•
J6
1
, ,
o
S
JO
-5
Fig. 2 (Cravy). Keratometric decay curve for Case #6. The hatch marks indicate removal of compression sutures.
I
24
-4
-7
•
11 **THS
-2
-6
PRi&'
12
-1
-2
0 I 0
-, -,
-. 'I..'¥"
P T
0
R
-1
E +C·'.I2. 010·)
5
,
12
18
2.
30
MONTHS
-2
Fig. 3 (Cravy). Keratometric decay curve for Case #5. The hatch marks indicate removal of compression sutures.
-.
-3
-5
-6 -7
-e
PREOI'
•, ,o
-,
1
"
T
t
;
11
-1
-2
-,
-. -. -, -s
-,
'I(OP
+(+1.25 x 003")
Fig. 6 (Cravy). Compressed-scale keratometric decay curve for Case #4 shows that the patient was still significantly overcorrected 14 weeks after astigmatism surgery. Subsequent removal of the last interrupted suture was immediately followed by wound gape with formation of a filtering bleb and more than a 7-D change in astigmatism. The hatch marks indicate removal of compression sutures.
+(+7.50 . 007·)
Fig. 4 (Cravy). Keratometric decay curve for Case #3. No sutures were removed. 162
AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
Because of its characteristic late hydrolysis in situ, nylon suture was not used for the shoelace closure. The polypropylene shoelace sutures displayed enduring tensile strength and the ability to readjust tension following interrupted suture removal. Eventual absorption of unremoved nylon interrupted sutures did not affect astigmatism (Fig. 4). Serial photokeratographs and keratometry were used to evaluate corneal astigmatism and objectively document the effects of surgery (Fig. 7, 8). This technique was not associated with any complications and was equally effective for ectatic and cicatricial cataract incisions.
Fig. 8 (Cravy). Photokeratograph of Case #8 taken one year after surgical correction of a cicatricial cataract wound. At the top of the photo is the net postoperative astigmatism, as measured by quantitative keratometry.
REFERENCES 1. Troutman RC: Microsurgical control of corneal astigmatism in
Fig. 7 (Cravy). Photokeratograph of Case #8 prior to surgical correction of a cicatricial cataract wound. At the top of the photo is the net preoperative astigmatism, as measured by quantitative keratometry.
cataract and keratoplasty. Trans Am Acad Ophthalmol Otolaryngol 77:563, 1973 2. Cravy TV: The Cravy operating keratometer, in Emery JM (ed): Current Concepts in Cataract Surgery. St Louis, CV Mosby Co, in press 3. Cravy TV: A modified suture placement technique to avoid suture drag or "cheese wire" effect. Ophthalmic Surg, in press 4. Cravy TV: Calculation of the change in corneal astigmatism following cataract extraction. Ophthalmic Surg 10:38, 1979
AM INTRA-OCULAR IMPLANT SOC J-VOL. 6, APRIL 1980
163