Combined myopia and astigmatism surgery Review of 350 cases David M. Schneider, M.D., Traci Draghic, C.O.T., Ramesh K. Murthy, B.S.
When radial keratotomy was introduced in the United States in the late 1970s, its application was limited to spherical myopia or to individuals with less than 1 diopter (D) of astigmatism. 1-4 Though this was helpful for many patients, it excluded a large percentage with compound myopic astigmatism. Since increasing numbers of these patients were seeking surgical correction of their refractive errors, it became incumbent on refractive surgeons to perform astigmatic procedures as well. Various techniques were proposed by various surgeons. These have been well reviewed 5 - 7 and include oval optical zones, multiple radial incisions in the axis of astigmatism, flag incisions, jump incisions, Ruiz incisions, and single transverse incisions. When this study was begun, there was no consensus among refractive surgeons about the best way to approach these cases. Having attempted many of the proposed techniques, the surgeon (D.M.S.) became convinced that transverse incisions placed on either side of the optical
center of the cornea was the most predictable procedure in his hands. We attempted to quantify the results of this technique, and determine the longterm stability of these incisions. MATERIALS AND METHODS The 229 patients in this study had preoperative astigmatism between 0.50 D and 6.00 D. A total of 350 eyes were studied in this series but some were hypermetropic preoperatively and were therefore excluded from the final data analysis. A total of 332 eyes were used for the astigmatism data alone but all eyes were analyzed for postoperative visual acuities. All surgeries were performed by the same surgeon (D.M.S.) at the Midwest Eye Center in Cincinnati, Ohio, between February 1985 and December 1987. Topical anesthesia was used in almost all cases and stabilization of the globe was achieved with a Bores two-point fixation forceps. All procedures were performed with a single-
Reprint requests to David M. Schneider, M.D., MidWest Eye Center, 6779 Colerain Avenue, Cincinnati, Ohio 45239. 370
J CATARACf REFRACT SURG-VOL 18, JULY 1992
edged, 45-degree diamond blade except for those eyes that had a second procedure to redeepen previous incisions. For these procedures, a front-cutting diamond blade was used. To insure maximal incision depth, the blade was set to at least 100% of corneal thickness as measured at the incision site. Thirty-nine of the 350 eyes (11 %) in our study required more than one surgical procedure to achieve maximal refractive correction. All radial incisions were made from the optical zone out to the periphery. All transverse incisions were placed between the radial incisions except for the few cases that required secondary astigmatism procedures. In certain of these eyes the transverse incisions transected radial incisions: The technique described by Thornton 8 using a single set of nonintersecting transverse incisions at the 7 mm optical zone was applied to the majority of cases (259). Dual optical zones were used in 73 eyes. Of these, 55 had dual zones at 5 mm and 7 mm and 18 had dual optical zones at 6 mm and 8 mm. Four eyes had triple optical zones at 5 mm, 7 mm, and 9 mm. Patients were evaluated preoperatively to rule out any pre-existing corneal pathology and to determine surgical parameters. The standard assessment included refraction (both subjective manifest and cycloplegic manifest), vision with and without correction, keratometry (Humphrey autokeratometer), intraocular pressure, and fundus evaluation. Postoperative visits were scheduled at approximately 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, and each year thereafter. Obviously all patients did not adhere to this strict schedule. The final available follow-up visit ranged from 3 months to 5+ years, with the mean follow-up time being 24 months.
Table 1. Uncorrected visual acuity at the final postoperative visit. Uncorrected Visual Activity
20/15-20/20 20/25 20/30 20/40 20/50-20/60 > 20/60
1.25 mm 1/3-1/2
Fig. 1.
Number
Percentage
150
43 21 19 10 4 3
75 65 35 14 11
1.75 mm 2/3
2.00 mm 3/4 Incision Lengths
2.50 mm
1
(Schneider) Reduced cylinder in the desired axis at the final available visit for cases having single transverse incisions at the 7 mm optical zone.
RESULTS The data were analyzed primarily to determine the correlative effects of specific transverse incision patterns on the astigmatic refractive status. This is described on the basis of reduced cylinder in the desired axis (i.e., the intended axis of correction). In addition, the data were analyzed to determine uncorrected visual acuity after surgery (Table 1) as a measure of effectiveness of the surgery from the patient's point of view. 9, 1 0 Figure 1 shows the results of 257 cases using the single transverse incisions at 7 mm. There is a progressive increase in effect that correlates with increase in incision length. The same can be seen in Figure 2 which gives the results for 52 cases using dual incisions at 5 mm and 7 mm optical zones. Figure 3 shows the results of the 18 cases in
1.25mm 1/3-1/2
Fig. 2.
1.75mm 213
2.00mm 3/4 Incision Lengths
2.50mm 1
(Schneider) Reduced cylinder in the desired axis at the final available visit for cases having dual incisions at the 5 mm and 7 mm optical zones.
which dual incisions were made at 6 mm and 8 mm. Figure 4 compares the overall mean cylinder reduction in the desired axis for all cases in each technique; however, individual incision lengths were not factored into the overall analysis.
J CATARACT REFRACT SURG-VOL 18, JULY 1992
371
g"
"
0
0
~
::I
al
al a:
a:
:;;
~
'C
'C
.5
.5
~
~
1.25mm 1/2
1.75mm 213 Incision Lengths
2.00mm 3/4
7mm
5&7mm
6&8mm
Optical Zone Width
Fig. 3. (Schneider) Reduced cylinder in the desired axis at the final available visit for cases having dual incisions at the 6 mm and 8 mm optical zones.
Fig. 4.
(Schneider) Comparison of the mean cylinder reduction in the desired axis for all cases in each technique.
3.0
2.5 CUI 0·._ >C
2.0
't).~ 0-
1.0
0.5
0.0
21
60
120
210
620
318
Time (Days)
3.0
€I 5&7mmOZ _6&8mmOZ
I>- -
2.5 CUI
.g~ Fig. 6.
(Schneider) Reduced cylinder in the desired axis at the final available visit for cases using dual optical zones (5 mml 7 mm and 6 mm/8 mm) .
2.0
!:l"C (i) "CCII" CII.!:: I:tUlc,. 1.5
/
!!!
.. ClIo
CIICC "C C eD .....
_,c
~:5
--------
1.0
0.5
0.0
21
60
120
210
318
Time (Days)
372
J CATARACT REFRACT SURG-VOL 18, JULY 1992
620
>725
Figures 5 and 6 demonstrate the reduction of cylinder in the desired axis longitudinally from 21 days postoperatively to over two years from time of surgery. Figure 5 shows the cases in which a single optical zone of 7 mm was used. Figure 6 shows the cases in which dual optical zones were used (5 mm/7 mm and 6 mm/8 mm). Both figures demonstrate a slight increased effect of the surgery between the last two visits.
DISCUSSION Thornton has prepared a nomogram for the nonintersecting T incisions to correct astigmatism in combination with radial incisions to correct myopia. 8 Our results in this study support the accuracy of his nomogram for the single set of nonintersecting T incisions at 7 mm. Our data did not support the projected results for dual incisions for astigmatism. This may be the result of the surgeon being overly cautious with less deep incisions as these cases (6 mm/8 mm) represent our earliest astigmatic cases. However, we did find that larger corrections could be achieved when using dual incisions at 5 mm and 7 mm and the results correlated well with incision length. This study confirms the use of transverse incisions as a quantifiably predictable technique to surgically reduce corneal astigmatism. Our results also confirm the relative stability of these transverse incisions, but like the PERK study and other reports, 11-16 we did find an increasing effect from the surgery in approximately 20% of the cases that had greater than a two-year follow-up. It remains to be seen whether these findings will change further with time. The results of this study show that 93% of the eyes studied attained 20/40 or better uncorrected visual acuity. It would seem that the next phase of study would compare these results with those being generated by studies involving the use oflasers to perform transverse incisions in the cornea. 17-20 As others have suggested,21,22 our clinical impression is that the results of combined myopic/astigmatic refractive surgery will be more accurate and predictable when the placement of the incisions can be geometrically insured as to location, depth, length, and especially tangentiality to the optical zone and perpendicularity with respect to the axis of astigmatism. REFERENCES l. Bores LD, Myers W, Cowden J. Radial keratotomy: an
analysis of the American experience. Ann Ophthalmol 1981; 13:941-948
2. Bores LD. Historical review and clinical results of radial keratotomy. Int Ophthalmol Clin 1983; 23(3):93118 3. Fyodorov SN, Durnev W. Operation of dosaged dissection of corneal circular ligament in cases of myopia of mild degree. Ann Ophthalmol 1979; 11: 18851890 4. Schachar RA. Indications, techniques, and complications of radial keratotomy. Int Ophthalmol Clin 1983; 23(3):119-128 5. Fyodorov SN, Durnev W. Surgical correction of complicated myopic astigmatism by means of dissection of circular ligament of cornea. Ann Ophthalmol 1981; 13:115-118 6. Zelman J. Controlling astigmatism with radial keratotomy. In: Schachar R, Levy N, Schachar L, eds, Refractive Keratoplasty, Denison, TX, LAL Publishing, 1983; 284-286 7. Franks JB, Binder PS. Keratotomy procedures for the correction of astigmatism. J Refract Surg 1985; 1(1): 11-17 8. Thornton SP. Thornton guide for radial keratotomy incisions and optical zone size. J Refract Surg 1985; 1:29-33 9. Lynn MJ, Waring GO III, Carter JT. Combining refractive error and uncorrected visual acuity to assess the effectiveness of refractive corneal surgery. Refract Corneal Surg 1990; 6:103-112 10. Lynn M, Waring GO III, Nizam A, et al. Symmetry of refractive and visual acuity outcome in the prospective evaluation of radial keratotomy (PERK) study. Refract Corneal Surg 1989; 5:75-81 11. Waring GO III, Lynn MJ, Gelender H, et al. Results of the prospective evaluation of radial keratotomy (PERK) study one year after surgery. Ophthalmology 1985; 92:177-198 12. Waring GO III, Lynn MJ, Culbertson W, et al. Threeyear results of the prospective evaluation of radial keratotomy (PERK) study. Ophthalmology 1987; 94: 1339-1354 13. Waring GO III, Lynn MJ, Fielding B, et al. Results of the prospective evaluation of radial keratotomy (PERK) study 4 years after surgery for myopia. JAMA 1990; 263:1083-1091 14. Waring GO III, Lynn MJ, Nizam A, et al. Results of the prospective evaluation of radial keratotomy (PERK) study five years after surgery. Ophthalmology 1991; 98:1164-1176 15. Arrowsmith PN, Marks RG. Visual, refractive, and keratometric results of radial keratotomy: five-year follow-up. Arch Ophthalmol1989; 107:506-511 16. Deitz MR, Sanders DR, Raanan MG. A consecutive series (1982-1985) of radial keratotomies performed with the diamond blade. Am J Ophthalmol1987; 103: 417-422 17. Seiller T, Bende T, Wollensak J, Trokel S. Excimer laser keratectomy for correction of astigmatism. Am J Ophthalmol1988; 105:117-124 18. Tenner A, Neuhann T, Schroder E, et al. Excimer laser radial keratotomy in the living human eye: a preliminary report. J Refract Surg 1988; 4:5-8 19. Trokel SL, Srinivasan R, Braren B. Excimer laser surgery of the cornea. Am J Ophthalmol1983; 96:710715 20. Krauss JM, Puliafito CA, Steinert RF. Laser interactions with the cornea. Surv Ophthalmol1986; 31:3753
J CATARACT REFRACT SURG-VOL 18, JULY 1992
373
21. Marshall J, Trokel S, Rothery S, et al. A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radiations from an excimer laser. Br] Ophthalmol1986; 70:482-501
374
22 . Sanders DR, Deitz MR. Factors affecting predictability of radial keratotomy . In: Sanders DR, Hofmann RF, eds, Refractive Surgery: A Text of Radial Keratotomy. Thorofare, N], Slack, 1985; 61-72
J CATARACT REFRACT SURG-VOL 18, JULY 1992
When radial keratotomy was introduced in the United States in the late 1970s, its application was limited to spherical myopia or to individuals with less than 1 diopter (D) of astigmatism. 1-4 Though this was helpful for many patients, it excluded a large percentage with compound myopic astigmatism. Since increasing numbers of these patients were seeking surgical correction of their refractive errors, it became incumbent on refractive surgeons to perform astigmatic procedures as well. Various techniques were proposed by various surgeons. These have been well reviewed 5 - 7 and include oval optical zones, multiple radial incisions in the axis of astigmatism, flag incisions, jump incisions, Ruiz incisions, and single transverse incisions. When this study was begun, there was no consensus among refractive surgeons about the best way to approach these cases. Having attempted many of the proposed techniques, the surgeon (D.M.S.) became convinced that transverse incisions placed on either side of the optical
center of the cornea was the most predictable procedure in his hands. We attempted to quantify the results of this technique, and determine the longterm stability of these incisions. MATERIALS AND METHODS The 229 patients in this study had preoperative astigmatism between 0.50 D and 6.00 D. A total of 350 eyes were studied in this series but some were hypermetropic preoperatively and were therefore excluded from the final data analysis. A total of 332 eyes were used for the astigmatism data alone but all eyes were analyzed for postoperative visual acuities. All surgeries were performed by the same surgeon (D.M.S.) at the Midwest Eye Center in Cincinnati, Ohio, between February 1985 and December 1987. Topical anesthesia was used in almost all cases and stabilization of the globe was achieved with a Bores two-point fixation forceps. All procedures were performed with a single-
Reprint requests to David M. Schneider, M.D., MidWest Eye Center, 6779 Colerain Avenue, Cincinnati, Ohio 45239. 370
J CATARACf REFRACT SURG-VOL 18, JULY 1992
edged, 45-degree diamond blade except for those eyes that had a second procedure to redeepen previous incisions. For these procedures, a front-cutting diamond blade was used. To insure maximal incision depth, the blade was set to at least 100% of corneal thickness as measured at the incision site. Thirty-nine of the 350 eyes (11 %) in our study required more than one surgical procedure to achieve maximal refractive correction. All radial incisions were made from the optical zone out to the periphery. All transverse incisions were placed between the radial incisions except for the few cases that required secondary astigmatism procedures. In certain of these eyes the transverse incisions transected radial incisions: The technique described by Thornton 8 using a single set of nonintersecting transverse incisions at the 7 mm optical zone was applied to the majority of cases (259). Dual optical zones were used in 73 eyes. Of these, 55 had dual zones at 5 mm and 7 mm and 18 had dual optical zones at 6 mm and 8 mm. Four eyes had triple optical zones at 5 mm, 7 mm, and 9 mm. Patients were evaluated preoperatively to rule out any pre-existing corneal pathology and to determine surgical parameters. The standard assessment included refraction (both subjective manifest and cycloplegic manifest), vision with and without correction, keratometry (Humphrey autokeratometer), intraocular pressure, and fundus evaluation. Postoperative visits were scheduled at approximately 1 day, 1 week, 1 month, 3 months, 6 months, 1 year, and each year thereafter. Obviously all patients did not adhere to this strict schedule. The final available follow-up visit ranged from 3 months to 5+ years, with the mean follow-up time being 24 months.
Table 1. Uncorrected visual acuity at the final postoperative visit. Uncorrected Visual Activity
20/15-20/20 20/25 20/30 20/40 20/50-20/60 > 20/60
1.25 mm 1/3-1/2
Fig. 1.
Number
Percentage
150
43 21 19 10 4 3
75 65 35 14 11
1.75 mm 2/3
2.00 mm 3/4 Incision Lengths
2.50 mm
1
(Schneider) Reduced cylinder in the desired axis at the final available visit for cases having single transverse incisions at the 7 mm optical zone.
RESULTS The data were analyzed primarily to determine the correlative effects of specific transverse incision patterns on the astigmatic refractive status. This is described on the basis of reduced cylinder in the desired axis (i.e., the intended axis of correction). In addition, the data were analyzed to determine uncorrected visual acuity after surgery (Table 1) as a measure of effectiveness of the surgery from the patient's point of view. 9, 1 0 Figure 1 shows the results of 257 cases using the single transverse incisions at 7 mm. There is a progressive increase in effect that correlates with increase in incision length. The same can be seen in Figure 2 which gives the results for 52 cases using dual incisions at 5 mm and 7 mm optical zones. Figure 3 shows the results of the 18 cases in
1.25mm 1/3-1/2
Fig. 2.
1.75mm 213
2.00mm 3/4 Incision Lengths
2.50mm 1
(Schneider) Reduced cylinder in the desired axis at the final available visit for cases having dual incisions at the 5 mm and 7 mm optical zones.
which dual incisions were made at 6 mm and 8 mm. Figure 4 compares the overall mean cylinder reduction in the desired axis for all cases in each technique; however, individual incision lengths were not factored into the overall analysis.
J CATARACT REFRACT SURG-VOL 18, JULY 1992
371
g"
"
0
0
~
::I
al
al a:
a:
:;;
~
'C
'C
.5
.5
~
~
1.25mm 1/2
1.75mm 213 Incision Lengths
2.00mm 3/4
7mm
5&7mm
6&8mm
Optical Zone Width
Fig. 3. (Schneider) Reduced cylinder in the desired axis at the final available visit for cases having dual incisions at the 6 mm and 8 mm optical zones.
Fig. 4.
(Schneider) Comparison of the mean cylinder reduction in the desired axis for all cases in each technique.
3.0
2.5 CUI 0·._ >C
2.0
't).~ 0-
1.0
0.5
0.0
21
60
120
210
620
318
Time (Days)
3.0
€I 5&7mmOZ _6&8mmOZ
I>- -
2.5 CUI
.g~ Fig. 6.
(Schneider) Reduced cylinder in the desired axis at the final available visit for cases using dual optical zones (5 mml 7 mm and 6 mm/8 mm) .
2.0
!:l"C (i) "CCII" CII.!:: I:tUlc,. 1.5
/
!!!
.. ClIo
CIICC "C C eD .....
_,c
~:5
--------
1.0
0.5
0.0
21
60
120
210
318
Time (Days)
372
J CATARACT REFRACT SURG-VOL 18, JULY 1992
620
>725
Figures 5 and 6 demonstrate the reduction of cylinder in the desired axis longitudinally from 21 days postoperatively to over two years from time of surgery. Figure 5 shows the cases in which a single optical zone of 7 mm was used. Figure 6 shows the cases in which dual optical zones were used (5 mm/7 mm and 6 mm/8 mm). Both figures demonstrate a slight increased effect of the surgery between the last two visits.
DISCUSSION Thornton has prepared a nomogram for the nonintersecting T incisions to correct astigmatism in combination with radial incisions to correct myopia. 8 Our results in this study support the accuracy of his nomogram for the single set of nonintersecting T incisions at 7 mm. Our data did not support the projected results for dual incisions for astigmatism. This may be the result of the surgeon being overly cautious with less deep incisions as these cases (6 mm/8 mm) represent our earliest astigmatic cases. However, we did find that larger corrections could be achieved when using dual incisions at 5 mm and 7 mm and the results correlated well with incision length. This study confirms the use of transverse incisions as a quantifiably predictable technique to surgically reduce corneal astigmatism. Our results also confirm the relative stability of these transverse incisions, but like the PERK study and other reports, 11-16 we did find an increasing effect from the surgery in approximately 20% of the cases that had greater than a two-year follow-up. It remains to be seen whether these findings will change further with time. The results of this study show that 93% of the eyes studied attained 20/40 or better uncorrected visual acuity. It would seem that the next phase of study would compare these results with those being generated by studies involving the use oflasers to perform transverse incisions in the cornea. 17-20 As others have suggested,21,22 our clinical impression is that the results of combined myopic/astigmatic refractive surgery will be more accurate and predictable when the placement of the incisions can be geometrically insured as to location, depth, length, and especially tangentiality to the optical zone and perpendicularity with respect to the axis of astigmatism. REFERENCES l. Bores LD, Myers W, Cowden J. Radial keratotomy: an
analysis of the American experience. Ann Ophthalmol 1981; 13:941-948
2. Bores LD. Historical review and clinical results of radial keratotomy. Int Ophthalmol Clin 1983; 23(3):93118 3. Fyodorov SN, Durnev W. Operation of dosaged dissection of corneal circular ligament in cases of myopia of mild degree. Ann Ophthalmol 1979; 11: 18851890 4. Schachar RA. Indications, techniques, and complications of radial keratotomy. Int Ophthalmol Clin 1983; 23(3):119-128 5. Fyodorov SN, Durnev W. Surgical correction of complicated myopic astigmatism by means of dissection of circular ligament of cornea. Ann Ophthalmol 1981; 13:115-118 6. Zelman J. Controlling astigmatism with radial keratotomy. In: Schachar R, Levy N, Schachar L, eds, Refractive Keratoplasty, Denison, TX, LAL Publishing, 1983; 284-286 7. Franks JB, Binder PS. Keratotomy procedures for the correction of astigmatism. J Refract Surg 1985; 1(1): 11-17 8. Thornton SP. Thornton guide for radial keratotomy incisions and optical zone size. J Refract Surg 1985; 1:29-33 9. Lynn MJ, Waring GO III, Carter JT. Combining refractive error and uncorrected visual acuity to assess the effectiveness of refractive corneal surgery. Refract Corneal Surg 1990; 6:103-112 10. Lynn M, Waring GO III, Nizam A, et al. Symmetry of refractive and visual acuity outcome in the prospective evaluation of radial keratotomy (PERK) study. Refract Corneal Surg 1989; 5:75-81 11. Waring GO III, Lynn MJ, Gelender H, et al. Results of the prospective evaluation of radial keratotomy (PERK) study one year after surgery. Ophthalmology 1985; 92:177-198 12. Waring GO III, Lynn MJ, Culbertson W, et al. Threeyear results of the prospective evaluation of radial keratotomy (PERK) study. Ophthalmology 1987; 94: 1339-1354 13. Waring GO III, Lynn MJ, Fielding B, et al. Results of the prospective evaluation of radial keratotomy (PERK) study 4 years after surgery for myopia. JAMA 1990; 263:1083-1091 14. Waring GO III, Lynn MJ, Nizam A, et al. Results of the prospective evaluation of radial keratotomy (PERK) study five years after surgery. Ophthalmology 1991; 98:1164-1176 15. Arrowsmith PN, Marks RG. Visual, refractive, and keratometric results of radial keratotomy: five-year follow-up. Arch Ophthalmol1989; 107:506-511 16. Deitz MR, Sanders DR, Raanan MG. A consecutive series (1982-1985) of radial keratotomies performed with the diamond blade. Am J Ophthalmol1987; 103: 417-422 17. Seiller T, Bende T, Wollensak J, Trokel S. Excimer laser keratectomy for correction of astigmatism. Am J Ophthalmol1988; 105:117-124 18. Tenner A, Neuhann T, Schroder E, et al. Excimer laser radial keratotomy in the living human eye: a preliminary report. J Refract Surg 1988; 4:5-8 19. Trokel SL, Srinivasan R, Braren B. Excimer laser surgery of the cornea. Am J Ophthalmol1983; 96:710715 20. Krauss JM, Puliafito CA, Steinert RF. Laser interactions with the cornea. Surv Ophthalmol1986; 31:3753
J CATARACT REFRACT SURG-VOL 18, JULY 1992
373
21. Marshall J, Trokel S, Rothery S, et al. A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radiations from an excimer laser. Br] Ophthalmol1986; 70:482-501
374
22 . Sanders DR, Deitz MR. Factors affecting predictability of radial keratotomy . In: Sanders DR, Hofmann RF, eds, Refractive Surgery: A Text of Radial Keratotomy. Thorofare, N], Slack, 1985; 61-72
J CATARACT REFRACT SURG-VOL 18, JULY 1992
