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Arcuate keratotomy to correct naturally occurring astigmatism
Arcuate keratotomy to correct naturally • • • occurring astigmatism Marvin L. Kwitko, MD, Sayed Jovkar, MD, Hua Yan, MD, Samuel Rymer, MD
ABSTRACT Purpose: To evaluate retrospectively the safety, efficacy, and complications of arcuate keratotomy (AI<) in correcting naturally occurring astigmatism. Setting: Laser Ultravision Institute, Montreal, Canada. Methods: Surgically induced refractive change was evaluated in 25 eyes of 15 patients with naturally occurring astigmatism. All patients had mixed or compound myopic astigmatism and were treated with AK alone or both AK and radial keratotomy (RK). Minimum follow-up of 24 months was necessary for inclusion in this study. We used vector analysis to evaluate the refractive and keratometric astigmatic change at 1 month and 1 and 2 years. Results: Ten eyes (40%) had AK only and 15 eyes (60%), both AK and RK. It was necessary to redeepen the original incisions in 21 eyes (84%). All patients had improved uncorrected visual acuity postoperatively. The reduction in refractive cylinder, quantified by vector analysis, was significant. Two years postoperatively, mean reduction was 3.30 diopters (0) ± 1.32 (SO) in eyes that had AK alone and 2.71 ± 1.53 0 in eyes that had both AK and RK. Conclusion: Arcuate keratotomy is an effective and safe method for correcting naturally occurring astigmatism. Further analysis of this series of patients is planned. J Cataract Refract Surg 1996; 22:1439-1442
M
anagement of significant naturally occurring astigmatism has been difficult with optical correction. Different surgical procedures have been devised to correct astigmatic errors including transverse keratotomy alone or combined with radial keratotomy (RK), the former to treat astigmatism and the latter to correct compound myopic astigmatism. 1 This study evaluated
From the Department of Ophthalmology, McGill University, and St. Mary s Hospital andJewish General Hospital, MontreaL Quebec, Canada (Kwitko, Jovkar), Department ofOphthalmology, Tianjin Medical University HospitaL Peoples Republic of China (yan), and Federal University ofRio Grande do Sol Porto Alegre, Brazil (Rymer). Reprint requests to Marvin L. Kwitko, MD, 5591 Cote des Neiges, Montreal, Quebec, H3T 1Y8 Canada.
the safety, efficacy, and predictability of arcuate keratotomy (AK) in the treatment of naturally occurring astigmatism.
Subjects and Methods We retrospectively analyzed the results of AK for correction of naturally occurring mixed or compound myopic astigmatism in 25 eyes of 15 patients. Inclusion criteria were contact lens intolerance and dissatisfaction with spectacle correction in patients older than 21 years. Exclusion criteria included previous corneal disease, uveitis, glaucoma, collagen vascular disease, and use of systemic corticosteroids. Preoperative examinations included Snellen visual acuity, manifest and cycloplegic refractions, pupil size in
J CATARACf REFRACT SURG-VOL 22, DECEMBER 1996
1439
AI< FOR NATURALLY OCCURRING ASTIGMATISM
normal and dim light, intraocular pressure, sliclamp biomicroscopy, ultrasonic pachymetry, corneal sensitivity with the Cochet-Bonnet anesthesiometer, and keratome try. Patients had topical corneal anesthesia with proparacaine hydrochloride 0.5% and a Nadbath facial nerve block. The pupil center was marked and the patient asked to fixate on the operating microscope light. The optical zone was then marked with an optical zone marker and the steeper meridian marked at the limbus. The desired arc was marked. The corneal thickness in the steeper meridian was measured intraoperatively by ultrasonic pachymetry. The diamond knife was calibrated with a microscope and the blade set at 100% of the thinnest eight paracentral pachymetry measurements 1.5 mm from the optical center. A front-cutting knife was set into the cornea with steady guidance through the incision. The nomogram used is shown in Table 1. At the completion of the procedure (four or eight incisions with one or two arcuate incisions), topical antibiotic drops were instilled on the cornea and an eye patch was applied. Patients were examined 1 day, 1 week (using antibiotics four times a day), and 1 month postoperatively. After epithelialization, fluoromethalone 0.1 % was instilled four times daily for 1 month and then tapered to three times daily for another month. Of the 25 treated eyes, 10 (40%) received AK surgery alone and 15 (60%) had AK and RK simultaneously. In AK, a pair of arcuate incisions were made symmetrically on each side of the same meridians. In eyes requiring correction for myopia, AK was performed initially followed by RK. Most patients (21 eyes) required two treatments. The interval between treatments ranged from 3 to
Table 1. Arcuate incision nomogram. Number of Incisions*
Optical Zone (mm)
Correction (D)
Incision Length (Degrees)
2 2 2 2 2
7.0 7.0 7.0 6.5 6.5 6.5 6.0
1.00 1.50 2.00 2.50 3.00 4.00 5.00
30 45 45 45 60 90 90
'One incision in each hemimeridian
1440
14 months. The criteria for re-treatment were a cylinder power greater than 1.50 diopters (D) or patient dissatisfaction. The method of re-treatment was similar to the initial treatment. For reoperations, the nomogram shown in Table 1 was used. The AK incisions were first reopened with a Sinskey hook, and the diamond blade was set at the same depth as the first operation. The RK incisions were reopened and recut with a blade set at the same depth as when there was also residual myopia of 1.50 D or greater. Statistical analysis was performed using a paired Student's t-test. The vector analysis method developed by Holladay and coauthors2 was used to calculate sutgically induced refractive change.
Results The minimum follow-up for all patients was 2 years. Age range of the nine men and six women was 22 to 50 years.
Visual Acuity Uncorrected visual acuity ranged from 20/50 to 20/400 preoperatively and from 20/20 to 20/200 2 years postoperatively. All patients had improved uncorrected visual acuity. Best corrected visual acuity improved in 7 eyes and did not change in 18 eyes, all of which had a weak or no optical correction.
Refractive Cylinder In the 10 eyes that had AK alone, mean refractive cylinder decreased significantly from -4.05 0 ± 2.03 (SO) (range -1.50 to -7.00 D) preoperatively to -1.00 ± 0.95 D (range 0 to -2.75 D) at 2 years (t-test, P < .05) (Figure 1, A). Vector analysis of surgically reduced astigmatism in these eyes showed a significant average astigmatic reduction of 3.30 ± 1.32 D (range 1.50 to 5.18 D) at 2 years. In 15 eyes that had both AK and RK, refractive cylinder decreased significantly from - 3.27 ± 1.17 D (range -1.00 to -6.00 D) preoperatively to -1.08 ± 0.72 D (range -0.50 to -2.50 0) at 2 years (t-test, P < .05) (Figure 1, .8). Vector analysis showed a significant astigmatic reduction of 2.71 ± 1.53 D (range 0.77 to 5.49 D) at 2 years.
J CATARACf REFRACf SURG-VOL 22. DECEMBER 1996
AK FOR NATURALLY OCCURRING ASTIGMATISM
A
o
2 years postoperatively. In eyes that had both AK and RK, the preoperative spherical equivalent was -5.95 ± 2.34 D (range -2.25 to -10.25 D), which decreased to -2.08 ± 1.61 D (-1.50 to -6.75 D) 2 years postoperatively.
-1
. . . -2 -;1_ __ _ _.
1-3L.--:: ~----.--SE
•
[ill
Overcorrection
~ - .
RG
pre 12 months
KG
D
1 month
~
24 months
B -1
Complicatiom
-2
There were no complications including corneal perforation, corneal edema, delayed epithelialization, corneal ulceration, and symptoms such as glare, monocular diplopia, or distortion of image perception.
G; 0.. -3
- -==--- _ ..-
.2
o
Overcorrections were defined as a vector change in excess of the original astigmatism, by vector analysis. In 10 eyes with AK alone, no eye was overcorrected when analyzing keratometric cylinder values by vector analysis. In contrast, in the 15 eyes having both AK and RK, 2 were overcorrected. In 1 eye with a preoperative keratometric cylinder of -1.50 D, there was an overcorrection of 0.25 D; in another eye with a preoperative keratometric cylinder of -4.00 D, there was an overcorrection of about 1.00 D by vector analysis at 2 years.
-4 -5
- ----
-6
• till
SE pre 12 months
RG
GJ
Itl
Discussion
KG
1 month 24 months
Figure 1. (Kwitko) Mean spherical equivalents (SE), refractive cylinders (RC), and keratometric cylinders (KC) preoperatively and at 1, 12, and 24 months postoperatively in patients having AK alone (A) and both AK and RK (8).
Keratometric Cylinder In the 10 eyes that had AK alone, the surgical astigmatic reduction was 2.33 ± 1.18 D (range 0.62 to 3.72 D) at 2 years by vector analysis. In the 15 eyes that had both AK and RK, surgical astigmatic reduction was 2.15 ± 1.36 D (range 0.50 to 4.99 D).
Spherical Equivalent In eyes with AK alone, the mean preoperative spherical equivalent was -1.08 ± 3.07 D (range -0.75 to -4.75 D). This mean decreased to -0.43 ± 1.42 D
Astigmatism greater than 1.00 D usually requires some type of optical or surgical correction. Surgical methods of astigmatic correction have included AK, transverse keratotomy incision alone or combined with RK incisions, paired semiradial incision, trapezoidal keratotomy, relaxing incisions, and addition of compression sutures to AK or relaxing incisions. Arcuate incisions have a uniform distance from the optical center throughout their length and therefore have a much greater effect than straight transverse cuts of the same length and optical zone. 3 Moreover, arcuate incisions lead to less distortion by virtue of their uniform relaxation effect. In this study, we evaluated the safety of AK for the correction of naturally occurring astigmatism. There was no loss of best corrected visual acuity. All patients had improved uncorrected visual acuity. The only complications were two cases of overcorrection. Uncorrected visual acuity continued to improve after 1 month before stabilizing after 1 year.
J CATARACf REFRACf SURG-VOL 22, DECEMBER 1996
1441
AK FOR NATURALLY OCCURRING ASTIGMATISM
At 2 years, the refractive and keratometric cylinders decreased on average by 82 and 66%, respectively, by vector analysis in eyes that had AK alone. By comparison, the refractive and keratometric cylinder reduction averaged 83 and 78%, respectively, by vector analysis in eyes having both AK and RK. In our study, the astigmatic change remained relatively stable after 1 month. Price et al. 4 reported an average reduction in refractive astigmatic cylinder of 82% (vector analysis) in a multicenter study evaluating predictability of AK. However, the results are astigmatic values at 1 month postoperatively. Chavez et al. s also analyzed surgically induced refractive change in 40 eyes having AK alone or AK and RK. Average reduction in refractive cylinder was 72% in both groups, with 3 eyes losing best corrected visual acuity. In summary, our work and other studies4 ,5 show that AK is safe and effective in treating astigmatism. We
1442
plan to continue the follow-up and analysis of this series of patients.
References 1. Thornton SP, Sanders DR. Graded nonintersecting
2.
3.
4.
5.
transverse incisions for correction of idiopathic astigmatism. J Cataract Refract Surg 1987; 13:27-31 Holladay JT, Cravy TV, Koch DO. Calculating the surgically induced refractive change following ocular surgery. J Cataract Refract Surg 1992; 18:429-443 Thornton SP. Astigmatic keratotomy: a review of basic concepts with case reports. J Cataract Refract Surg 1990; 16:430-435 Price FW, Grene RB, Marks RG, et al. Astigmatism reduction clinical trial: a multicenter prospective evaluation of the predictability of arcuate keratotomy. Arch Ophthalmol 1995; 113:277-282 Chavez S, Chayet A, Celikkol L, et al. Analysis of astigmatic keratotomy with a 5.0-mm optical clear zone. Am J OphthalmoI1996; 121:65-76
J CATARACT REFRACT SURG-VOL 22, DECEMBER 1996
ABSTRACT Purpose: To evaluate retrospectively the safety, efficacy, and complications of arcuate keratotomy (AI<) in correcting naturally occurring astigmatism. Setting: Laser Ultravision Institute, Montreal, Canada. Methods: Surgically induced refractive change was evaluated in 25 eyes of 15 patients with naturally occurring astigmatism. All patients had mixed or compound myopic astigmatism and were treated with AK alone or both AK and radial keratotomy (RK). Minimum follow-up of 24 months was necessary for inclusion in this study. We used vector analysis to evaluate the refractive and keratometric astigmatic change at 1 month and 1 and 2 years. Results: Ten eyes (40%) had AK only and 15 eyes (60%), both AK and RK. It was necessary to redeepen the original incisions in 21 eyes (84%). All patients had improved uncorrected visual acuity postoperatively. The reduction in refractive cylinder, quantified by vector analysis, was significant. Two years postoperatively, mean reduction was 3.30 diopters (0) ± 1.32 (SO) in eyes that had AK alone and 2.71 ± 1.53 0 in eyes that had both AK and RK. Conclusion: Arcuate keratotomy is an effective and safe method for correcting naturally occurring astigmatism. Further analysis of this series of patients is planned. J Cataract Refract Surg 1996; 22:1439-1442
M
anagement of significant naturally occurring astigmatism has been difficult with optical correction. Different surgical procedures have been devised to correct astigmatic errors including transverse keratotomy alone or combined with radial keratotomy (RK), the former to treat astigmatism and the latter to correct compound myopic astigmatism. 1 This study evaluated
From the Department of Ophthalmology, McGill University, and St. Mary s Hospital andJewish General Hospital, MontreaL Quebec, Canada (Kwitko, Jovkar), Department ofOphthalmology, Tianjin Medical University HospitaL Peoples Republic of China (yan), and Federal University ofRio Grande do Sol Porto Alegre, Brazil (Rymer). Reprint requests to Marvin L. Kwitko, MD, 5591 Cote des Neiges, Montreal, Quebec, H3T 1Y8 Canada.
the safety, efficacy, and predictability of arcuate keratotomy (AK) in the treatment of naturally occurring astigmatism.
Subjects and Methods We retrospectively analyzed the results of AK for correction of naturally occurring mixed or compound myopic astigmatism in 25 eyes of 15 patients. Inclusion criteria were contact lens intolerance and dissatisfaction with spectacle correction in patients older than 21 years. Exclusion criteria included previous corneal disease, uveitis, glaucoma, collagen vascular disease, and use of systemic corticosteroids. Preoperative examinations included Snellen visual acuity, manifest and cycloplegic refractions, pupil size in
J CATARACf REFRACT SURG-VOL 22, DECEMBER 1996
1439
AI< FOR NATURALLY OCCURRING ASTIGMATISM
normal and dim light, intraocular pressure, sliclamp biomicroscopy, ultrasonic pachymetry, corneal sensitivity with the Cochet-Bonnet anesthesiometer, and keratome try. Patients had topical corneal anesthesia with proparacaine hydrochloride 0.5% and a Nadbath facial nerve block. The pupil center was marked and the patient asked to fixate on the operating microscope light. The optical zone was then marked with an optical zone marker and the steeper meridian marked at the limbus. The desired arc was marked. The corneal thickness in the steeper meridian was measured intraoperatively by ultrasonic pachymetry. The diamond knife was calibrated with a microscope and the blade set at 100% of the thinnest eight paracentral pachymetry measurements 1.5 mm from the optical center. A front-cutting knife was set into the cornea with steady guidance through the incision. The nomogram used is shown in Table 1. At the completion of the procedure (four or eight incisions with one or two arcuate incisions), topical antibiotic drops were instilled on the cornea and an eye patch was applied. Patients were examined 1 day, 1 week (using antibiotics four times a day), and 1 month postoperatively. After epithelialization, fluoromethalone 0.1 % was instilled four times daily for 1 month and then tapered to three times daily for another month. Of the 25 treated eyes, 10 (40%) received AK surgery alone and 15 (60%) had AK and RK simultaneously. In AK, a pair of arcuate incisions were made symmetrically on each side of the same meridians. In eyes requiring correction for myopia, AK was performed initially followed by RK. Most patients (21 eyes) required two treatments. The interval between treatments ranged from 3 to
Table 1. Arcuate incision nomogram. Number of Incisions*
Optical Zone (mm)
Correction (D)
Incision Length (Degrees)
2 2 2 2 2
7.0 7.0 7.0 6.5 6.5 6.5 6.0
1.00 1.50 2.00 2.50 3.00 4.00 5.00
30 45 45 45 60 90 90
'One incision in each hemimeridian
1440
14 months. The criteria for re-treatment were a cylinder power greater than 1.50 diopters (D) or patient dissatisfaction. The method of re-treatment was similar to the initial treatment. For reoperations, the nomogram shown in Table 1 was used. The AK incisions were first reopened with a Sinskey hook, and the diamond blade was set at the same depth as the first operation. The RK incisions were reopened and recut with a blade set at the same depth as when there was also residual myopia of 1.50 D or greater. Statistical analysis was performed using a paired Student's t-test. The vector analysis method developed by Holladay and coauthors2 was used to calculate sutgically induced refractive change.
Results The minimum follow-up for all patients was 2 years. Age range of the nine men and six women was 22 to 50 years.
Visual Acuity Uncorrected visual acuity ranged from 20/50 to 20/400 preoperatively and from 20/20 to 20/200 2 years postoperatively. All patients had improved uncorrected visual acuity. Best corrected visual acuity improved in 7 eyes and did not change in 18 eyes, all of which had a weak or no optical correction.
Refractive Cylinder In the 10 eyes that had AK alone, mean refractive cylinder decreased significantly from -4.05 0 ± 2.03 (SO) (range -1.50 to -7.00 D) preoperatively to -1.00 ± 0.95 D (range 0 to -2.75 D) at 2 years (t-test, P < .05) (Figure 1, A). Vector analysis of surgically reduced astigmatism in these eyes showed a significant average astigmatic reduction of 3.30 ± 1.32 D (range 1.50 to 5.18 D) at 2 years. In 15 eyes that had both AK and RK, refractive cylinder decreased significantly from - 3.27 ± 1.17 D (range -1.00 to -6.00 D) preoperatively to -1.08 ± 0.72 D (range -0.50 to -2.50 0) at 2 years (t-test, P < .05) (Figure 1, .8). Vector analysis showed a significant astigmatic reduction of 2.71 ± 1.53 D (range 0.77 to 5.49 D) at 2 years.
J CATARACf REFRACf SURG-VOL 22. DECEMBER 1996
AK FOR NATURALLY OCCURRING ASTIGMATISM
A
o
2 years postoperatively. In eyes that had both AK and RK, the preoperative spherical equivalent was -5.95 ± 2.34 D (range -2.25 to -10.25 D), which decreased to -2.08 ± 1.61 D (-1.50 to -6.75 D) 2 years postoperatively.
-1
. . . -2 -;1_ __ _ _.
1-3L.--:: ~----.--SE
•
[ill
Overcorrection
~ - .
RG
pre 12 months
KG
D
1 month
~
24 months
B -1
Complicatiom
-2
There were no complications including corneal perforation, corneal edema, delayed epithelialization, corneal ulceration, and symptoms such as glare, monocular diplopia, or distortion of image perception.
G; 0.. -3
- -==--- _ ..-
.2
o
Overcorrections were defined as a vector change in excess of the original astigmatism, by vector analysis. In 10 eyes with AK alone, no eye was overcorrected when analyzing keratometric cylinder values by vector analysis. In contrast, in the 15 eyes having both AK and RK, 2 were overcorrected. In 1 eye with a preoperative keratometric cylinder of -1.50 D, there was an overcorrection of 0.25 D; in another eye with a preoperative keratometric cylinder of -4.00 D, there was an overcorrection of about 1.00 D by vector analysis at 2 years.
-4 -5
- ----
-6
• till
SE pre 12 months
RG
GJ
Itl
Discussion
KG
1 month 24 months
Figure 1. (Kwitko) Mean spherical equivalents (SE), refractive cylinders (RC), and keratometric cylinders (KC) preoperatively and at 1, 12, and 24 months postoperatively in patients having AK alone (A) and both AK and RK (8).
Keratometric Cylinder In the 10 eyes that had AK alone, the surgical astigmatic reduction was 2.33 ± 1.18 D (range 0.62 to 3.72 D) at 2 years by vector analysis. In the 15 eyes that had both AK and RK, surgical astigmatic reduction was 2.15 ± 1.36 D (range 0.50 to 4.99 D).
Spherical Equivalent In eyes with AK alone, the mean preoperative spherical equivalent was -1.08 ± 3.07 D (range -0.75 to -4.75 D). This mean decreased to -0.43 ± 1.42 D
Astigmatism greater than 1.00 D usually requires some type of optical or surgical correction. Surgical methods of astigmatic correction have included AK, transverse keratotomy incision alone or combined with RK incisions, paired semiradial incision, trapezoidal keratotomy, relaxing incisions, and addition of compression sutures to AK or relaxing incisions. Arcuate incisions have a uniform distance from the optical center throughout their length and therefore have a much greater effect than straight transverse cuts of the same length and optical zone. 3 Moreover, arcuate incisions lead to less distortion by virtue of their uniform relaxation effect. In this study, we evaluated the safety of AK for the correction of naturally occurring astigmatism. There was no loss of best corrected visual acuity. All patients had improved uncorrected visual acuity. The only complications were two cases of overcorrection. Uncorrected visual acuity continued to improve after 1 month before stabilizing after 1 year.
J CATARACf REFRACf SURG-VOL 22, DECEMBER 1996
1441
AK FOR NATURALLY OCCURRING ASTIGMATISM
At 2 years, the refractive and keratometric cylinders decreased on average by 82 and 66%, respectively, by vector analysis in eyes that had AK alone. By comparison, the refractive and keratometric cylinder reduction averaged 83 and 78%, respectively, by vector analysis in eyes having both AK and RK. In our study, the astigmatic change remained relatively stable after 1 month. Price et al. 4 reported an average reduction in refractive astigmatic cylinder of 82% (vector analysis) in a multicenter study evaluating predictability of AK. However, the results are astigmatic values at 1 month postoperatively. Chavez et al. s also analyzed surgically induced refractive change in 40 eyes having AK alone or AK and RK. Average reduction in refractive cylinder was 72% in both groups, with 3 eyes losing best corrected visual acuity. In summary, our work and other studies4 ,5 show that AK is safe and effective in treating astigmatism. We
1442
plan to continue the follow-up and analysis of this series of patients.
References 1. Thornton SP, Sanders DR. Graded nonintersecting
2.
3.
4.
5.
transverse incisions for correction of idiopathic astigmatism. J Cataract Refract Surg 1987; 13:27-31 Holladay JT, Cravy TV, Koch DO. Calculating the surgically induced refractive change following ocular surgery. J Cataract Refract Surg 1992; 18:429-443 Thornton SP. Astigmatic keratotomy: a review of basic concepts with case reports. J Cataract Refract Surg 1990; 16:430-435 Price FW, Grene RB, Marks RG, et al. Astigmatism reduction clinical trial: a multicenter prospective evaluation of the predictability of arcuate keratotomy. Arch Ophthalmol 1995; 113:277-282 Chavez S, Chayet A, Celikkol L, et al. Analysis of astigmatic keratotomy with a 5.0-mm optical clear zone. Am J OphthalmoI1996; 121:65-76
J CATARACT REFRACT SURG-VOL 22, DECEMBER 1996