- Email: [email protected]
Refractive outcomes after arcuate keratotomy using the Terry astigmatome
Refractive outcomes after arcuate keratotomy using the Terry astigmatome ¨ zc¸etin, MD Mehmet Baykara, MD, Murat Dogru, MD, PhD, Hikmet O Purpose: To investigate the refractive outcomes after arcuate keratotomy for astigmatism. Setting: Uludag University, Faculty of Medicine, Department of Ophthalmology, Bursa, Turkey. Method: Sixteen eyes of 11 patients with astigmatism had arcuate keratotomy using the Terry astigmatome. The mean age of the patients was 36 years ⫾ 10 (SD). All patients received preoperative and postoperative ophthalmic examinations consisting of best spectacle-corrected (BSCVA) and uncorrected (UCVA) visual acuities, corneal topography, and ultrasonic pachymetry. Surgery was performed using topical anesthesia of oxybuprocaine 0.1% eyedrops. The Terry astigmatome was selected by the mean paracentral (estimated incision area) corneal thickness. All patients received topical ofloxacin 0.3% and topical diclofenac 0.1% eyedrops postoperatively. Results: The mean corneal astigmatism was ⫺4.0 ⫾ 1.1 diopters (D) (range ⫺2.2 to ⫺6.0 D) preoperatively and –1.8 ⫾ 0.8 D (range ⫺0.6 to ⫺3.0 D) postoperatively. The mean surgically induced corneal astigmatism was 2.5 ⫾ 0.6 D. The mean UCVA (logMAR) was 0.74 ⫾ 0.25 preoperatively and 0.18 ⫾ 0.23 1 week postoperatively, and the mean BSCVA (logMAR) was 0.19 ⫾ 0.24 and 0.19 ⫾ 0.23, respectively. There were no intraoperative or postoperative complications. Conclusion: Arcuate keratotomy using the Terry astigmatome was a safe and reliable treatment for corneal astigmatism. J Cataract Refract Surg 2003; 29:2397–2401 2003 ASCRS and ESCRS
A
stigmatism is a refractive error with a prevalence in the normal population of 14% to 50%.1 The first experimental keratotomy to correct astigmatism was performed in 1898 by Leendedt Jan Lans,2 after which Fyodorov proposed TL- or RL-shaped astigmatic incisions.3 The technique evolved into isolated horizontal incisions, introduced by Lindstrom, and then arcuate incisions, introduced by Merlin.3–6 At present, arcuate incisions are performed using a corneal optical Accepted for publication February 6, 2003. From the Department of Ophthalmology, Uludag University School of Medicine, Bursa, Turkey. None of the authors has a financial or proprietary interest in any material or method mentioned. Reprint requests to Mehmet Baykara, MD, Uludag University Faculty of Medicine, Department of Ophthalmology, 16059, Gorukle, Bursa, Turkey. E-mail: [email protected]. 2003 ASCRS and ESCRS Published by Elsevier Inc.
zone of 6.0 to 8.0 mm.3 The excimer laser and toric intraocular lenses have recently been advocated as other modalities to treat astigmatism.7,8 We present the results of astigmatic correction by arcuate incisions using the Terry astigmatome in eyes with naturally occurring corneal astigmatism.
Patients and Methods In this study, 16 eyes of 11 patients with naturally occurring orthogonal astigmatism were evaluated. The mean age of the 5 men (45.5%) and 7 women (54.5%) was 36 years ⫾ 10 (SD) (range 21 to 82 years). All patients had visual acuity measurements with the logMAR chart using manifest and cycloplegic refractions, biomicroscopic anterior and posterior segment examinations, intraocular pressure measurement by applanation tonometry, corneal topography (Tomey TMS 1, version 1.61), and corneal thickness measurement by ultrasonic pachymetry (So0886-3350/03/$–see front matter doi:10.1016/S0886-3350(03)00246-3
ASTIGMATIC SURGERY USING THE TERRY ASTIGMATOME
Figure 1. (Baykara) Body and disposable blade of the Terry astigmatome.
Figure 2. (Baykara) Disposable parts (position indicator, blade
The Terry astigmatome, which was used in all cases, consisted of a body with an indicator (Figure 1) and a disposable keratome (Figure 2). Different bodies were used for limbal (10.0 mm) and corneal (8.0 mm) arcuate incisions. The incision depth was 50 m less than the mean paracentral corneal pachymetry. The incision length was adjusted according to the astigmatic value on the Terry nomogram (Table 1), which corresponded to the amount of desired correction. The keratomes were designed to make 500, 550, and 600 m incisions in opposite axes for 8.0 mm optical zones and 550, 600, and 650 m in opposite axes for 10.0 mm optical zones. One surgeon (M.B.) performed all procedures. One drop of oxybuprocaine 0.1% was instilled every 5 minutes 20 minutes before surgery. The periocular area and eyelids were cleaned with an antiseptic solution containing povidone– iodine 10%. A lid retractor was placed. The ocular surface was washed with fortified balanced salt solution (BSS Plus威) and then dried with absorbent sticks. The 0-, 90-, 180-, and 270-degree axes and the surgical axis of the cornea were marked. The astigmatome body with the indicator was placed according to the surgical axis. An incision was made at the targeted angle by placing the keratome on the midpoint of the axis where the astigmatism was highest. The incision site was washed with BSS Plus. Eyes were patched after antibiotic or antiinflammatory drops were instilled. All eyes received topical ofloxacin 0.3% and diclofenac 0.1% 4 times a day for 2 weeks. Visual acuity, keratometry, and topography were measured 1 day, 1 week, 1, 3, and 6 months, and 1 year postoperatively. The astigmatism results were evaluated by vector analysis using the Holladay-Cravy-Koch formula. Statistical analysis was by the Wilcoxon test with the probability level at 1%.8
guard, and blade) of the blade holder.
Results noscan 4000 AP, Sonomed Inc.). Surgery was planned according to the topographic map findings. The knife used for surgery was chosen to cut approximately 90% of the paracentral (estimated incision area) corneal thickness.
The mean corneal astigmatism was ⫺4.00 ⫾ 1.10 diopters (D) (range ⫺2.20 to ⫺6.00 D) preoperatively and ⫺1.80 ⫾ 0.80 D (range ⫺0.60 to ⫺3.00 D) postoperatively. The difference in mean corneal myopic
Table 1. Terry nomogram. ATR Astigmatism
WTR Astigmatism
Diopters
OZ (mm)
Incisions (n)
Degrees
Incision Indicator
OZ (mm)
Incisions (n)
Degrees
Incision Indicator
1
10.0
1
90
4.5–4.5
8.0
2
60
3.0–3.0
2
10.0
2
60
3.0–3.0
8.0
2
80
4.0–4.0
3
10.0
2
80
4.0–4.0
8.0
2
100
5.0–5.0
4
10.0
2
100
5.0–5.0
—
—
—
—
ATR ⫽ against the rule; OZ ⫽ optical zone; WTR ⫽ with the rule
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J CATARACT REFRACT SURG—VOL 29, DECEMBER 2003
ASTIGMATIC SURGERY USING THE TERRY ASTIGMATOME
Figure 3. (Baykara) Preoperative (left) and postoperative (right) topographies in case 5.
astigmatism between preoperatively and 1 week postoperatively was statistically significant (P⬍.01). There was no statistically significant difference in the mean corneal myopic astigmatism between 1 week and 1 year (P⬎.05). The mean desired astigmatic correction was 3.00 ⫾ 0.59 D. The final surgically induced astigmatism was 2.50 ⫾ 0.60 D (Table 2). The mean uncorrected visual acuity (UCVA) was 0.74 ⫾ 0.25 preoperatively and 0.18 ⫾ 0.23 at 1 week. The mean final UCVA was 0.20 ⫾ 0.20. The difference
in the mean UCVA between preoperatively and postoperatively was statistically significant (P⬍.01). The mean best spectacle-corrected visual acuity (BSCVA) was 0.19 ⫾ 0.24 preoperatively and 0.19 ⫾ 0.23 at 1 week. The mean final BSCVA was 0.19 ⫾ 0.23. The difference in the mean BSCVA between preoperatively and postoperatively was statistically significant (P⬍.01). There was no statistically significant difference between the mean postoperative BSCVA and final BSCVA (P⬎.05) (Table 2).
Table 2. Patients’ characteristics and results. Age Case/Pt (Y) Sex Eye 1/1 2/2 3/2 4/3 5/4 6/5 7/6 8/7 9/8 10/8 11/9 12/9 13/10 14/10 15/11 16/11
45 27 27 30 31 39 28 52 51 51 39 39 21 21 32 32
M F F F M F M F M M M M F F F F
R R L R L R L L R L R L R L R L
Preop COA 4.7 3.5 3.0 4.7 5.2 3.0 6.0 4.4 4.0 2.2 3.8 2.2 4.8 4.8 4.8 4.9
⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻
21 98 80 87 162 86 166 86 93 93 97 153 82 86 103 69
Preop Preop MPCT SN UCVA BSCVA (m) (m) 1.0 0.5 0.5 0.7 1.0 0.7 1.0 0.7 1.0 0.4 0.7 0.2 1.0 1.0 0.7 0.7
0.7 0.3 0.1 0.1 0.5 0.1 0.7 0.1 0.0 0.0 0.2 0.0 0.0 0.0 0.1 0.0
595 580 594 610 637 590 655 570 580 615 600 560 650 640 620 610
550 550 550 550 550 550 600 500 500 550 550 500 600 600 550 550
Postop COA 3.0 1.4 1.4 1.8 2.8 1.0 3.0 1.8 0.8 0.6 1.5 1.0 3.0 2.7 2.1 2.1
⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻
3 82 80 80 179 87 169 84 103 110 120 146 87 84 89 60
Postop Des Post UCVA AC (D) BSCVA 0.7 0.0 0.0 0.1 0.4 0.0 0.7 0.1 0.0 0.0 0.1 0.1 0.2 0.2 0.1 0.2
4.0 3.0 3.0 3.0 4.0 3.0 4.0 3.0 3.0 2.0 3.0 2.0 3.0 3.0 3.0 3.0
0.7 0.0 0.0 0.1 0.4 0.0 0.5 0.0 0.0 0.1 0.0 0.1 0.0 0.0 0.1 0.0
SIA 2.88 2.43 1.60 2.99 3.28 2.00 3.00 2.60 3.30 1.80 3.00 1.25 1.90 2.11 3.11 3.00
⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻
FU (Mo) CLV 40 107 80 91 148 86 163 87 91 88 86 159 74 89 122 75
12 9 9 11 9 19 11 16 16 15 14 13 11 11 8 8
Amb — — — Amb — Amb — — — — — — — — —
Amb ⫽ amblyopia; BSCVA ⫽ best spectacle-corrected visual acuity, logMAR; CLV ⫽ cause of low vision; COA ⫽ corneal astigmatism; Des AC ⫽ desired astigmatic correction; FU ⫽ follow-up; MPCT ⫽ mean paracentral corneal thickness; Pt ⫽ patient; SIA ⫽ surgically induced astigmatism; SN ⫽ surgical knife depth; UCVA ⫽ uncorrected visual acuity, logMAR
J CATARACT REFRACT SURG—VOL 29, DECEMBER 2003
2399
ASTIGMATIC SURGERY USING THE TERRY ASTIGMATOME
Increasingly effective corneal laser surgery techniques have been developed to treat myopia, hyperopia, and astigmatism. Thus, correction of higher corneal astigmatism can be performed.13 In conclusion, our results indicate that the Terry astigmatome, with its fixed depth cut and easy manipulation, is safe in the correction of astigmatism in selected patients. The creation of single or paired incisions was easily achieved.
References Figure 4. (Baykara) Postoperative photograph of the arcuate incisions in case 11.
No epithelial defects or perforations occurred. Figure 3 shows the preoperative and postoperative corneal topographies in case 5 and Figure 4, an anterior segment photograph of case 11.
Discussion Many refractive procedures have been developed to correct myopic astigmatism greater than 2.00 D. These include astigmatic keratotomy, refractive corneal laser techniques, and combined procedures.3–10 An arcuate incision causes relative flattening of the cornea in the axis of the incision with relative steepening at 90 degrees of the incision. This effect, known as coupling, varies with the location, number, depth, and length of the incision. Because the inferotemporal cornea is the thinnest zone, incisions made there are expected to be the deepest.3 Thus, it is important that the knife used for these incisions not cut deep enough to cause a perforation. In our study, the mean paracentral thickness was 606.4 ⫾ 29.3 m (range 560 to 650 m). The knives were chosen to cut on average 90% of corneal thickness of the estimated incision area. No perforations occurred, and the mean final refractive change was 2.50 ⫾ 0.60 D, confirming the appropriateness of the procedure and the desired correction (mean 3.00 ⫾ 0.59 D). Clinical and experimental ultrasonic biomicroscopic studies should be done to validate the incision depths and correlate them with refractive results. Astigmatic change can also be assessed by wavefront analysis.11,12
2400
1. Bear JC, Richler A. Cylindrical refractive error: a population study in western Newfoundland. Am J Optom Physiol Opt 1983; 60:39–45 2. Hirsch MJ. Changes in astigmatism during the first eight years of school—an interim report from the Ojai longitudinal study. Am J Optom 1963; 40:127–132 3. Ozcetin H. Astigmatic keratotomy. In: Ozcetin H, Sener B, eds, Treatment of Myopia. Istanbul, Nobel Press, 2002; 271–287 4. Hoffmann RF. The surgical correction of idiopathic astigmatism. In: Sanders DR, Hoffmann RF, Salz JJ, eds, Refractive Corneal Surgery. Thorofare, NJ, Slack, 1986; 241–290 5. Merlin U. Curved keratotomy procedure for congenital astigmatism. J Refract Surg 1987; 3:92–97 6. Budak K, Yılmaz G, Aslan BS, Duman S. Limbal relaxing incisions in congenital astigmatism: 6 month follow-up. J Cataract Refract Surg 2001; 27:715–719 7. Shimizu K, Misawa A, Suzuki Y. Toric intraocular lenses: correcting astigmatism while controlling axis shift. J Cataract Refract Surg 1994; 20:523–526 8. Gu¨ell JL, Vazquez M. Correction of high astigmatism with astigmatic keratotomy combined with laser in situ keratomileusis J Cataract Refract Surg 2000; 26: 960–966 9. Maloney WF, Sanders DR, Pearcy DE. Astigmatic keratotomy to correct preexisting astigmatism in cataract patients. J Cataract Refract Surg 1990; 16:297–304 10. Yang C-N, Shen EP, Hu F-R. Laser in situ keratomileusis for the correction of myopia and myopic astigmatism. J Cataract Refract Surg 2001; 27:1952–1960 11. Harris WF. Analysis of astigmatism in anterior segment surgery. J Cataract Refract Surg 2001; 27:107–128 12. Applegate RA, Hilmantel G, Howland HC, et al. Corneal first surface optical aberrations and visual performance. J Refract Surg 2000; 16:507–514 13. Sheludchenko VM, Rybintseva LV, Kurenkov VV. [Correction of high astigmatism and astigmatic anisometropia by intrastromal photokerato-ablation in children and adolescents]. [Russian] Vestn Oftalmol 2002; 118(4):18–22
J CATARACT REFRACT SURG—VOL 29, DECEMBER 2003
A
stigmatism is a refractive error with a prevalence in the normal population of 14% to 50%.1 The first experimental keratotomy to correct astigmatism was performed in 1898 by Leendedt Jan Lans,2 after which Fyodorov proposed TL- or RL-shaped astigmatic incisions.3 The technique evolved into isolated horizontal incisions, introduced by Lindstrom, and then arcuate incisions, introduced by Merlin.3–6 At present, arcuate incisions are performed using a corneal optical Accepted for publication February 6, 2003. From the Department of Ophthalmology, Uludag University School of Medicine, Bursa, Turkey. None of the authors has a financial or proprietary interest in any material or method mentioned. Reprint requests to Mehmet Baykara, MD, Uludag University Faculty of Medicine, Department of Ophthalmology, 16059, Gorukle, Bursa, Turkey. E-mail: [email protected]. 2003 ASCRS and ESCRS Published by Elsevier Inc.
zone of 6.0 to 8.0 mm.3 The excimer laser and toric intraocular lenses have recently been advocated as other modalities to treat astigmatism.7,8 We present the results of astigmatic correction by arcuate incisions using the Terry astigmatome in eyes with naturally occurring corneal astigmatism.
Patients and Methods In this study, 16 eyes of 11 patients with naturally occurring orthogonal astigmatism were evaluated. The mean age of the 5 men (45.5%) and 7 women (54.5%) was 36 years ⫾ 10 (SD) (range 21 to 82 years). All patients had visual acuity measurements with the logMAR chart using manifest and cycloplegic refractions, biomicroscopic anterior and posterior segment examinations, intraocular pressure measurement by applanation tonometry, corneal topography (Tomey TMS 1, version 1.61), and corneal thickness measurement by ultrasonic pachymetry (So0886-3350/03/$–see front matter doi:10.1016/S0886-3350(03)00246-3
ASTIGMATIC SURGERY USING THE TERRY ASTIGMATOME
Figure 1. (Baykara) Body and disposable blade of the Terry astigmatome.
Figure 2. (Baykara) Disposable parts (position indicator, blade
The Terry astigmatome, which was used in all cases, consisted of a body with an indicator (Figure 1) and a disposable keratome (Figure 2). Different bodies were used for limbal (10.0 mm) and corneal (8.0 mm) arcuate incisions. The incision depth was 50 m less than the mean paracentral corneal pachymetry. The incision length was adjusted according to the astigmatic value on the Terry nomogram (Table 1), which corresponded to the amount of desired correction. The keratomes were designed to make 500, 550, and 600 m incisions in opposite axes for 8.0 mm optical zones and 550, 600, and 650 m in opposite axes for 10.0 mm optical zones. One surgeon (M.B.) performed all procedures. One drop of oxybuprocaine 0.1% was instilled every 5 minutes 20 minutes before surgery. The periocular area and eyelids were cleaned with an antiseptic solution containing povidone– iodine 10%. A lid retractor was placed. The ocular surface was washed with fortified balanced salt solution (BSS Plus威) and then dried with absorbent sticks. The 0-, 90-, 180-, and 270-degree axes and the surgical axis of the cornea were marked. The astigmatome body with the indicator was placed according to the surgical axis. An incision was made at the targeted angle by placing the keratome on the midpoint of the axis where the astigmatism was highest. The incision site was washed with BSS Plus. Eyes were patched after antibiotic or antiinflammatory drops were instilled. All eyes received topical ofloxacin 0.3% and diclofenac 0.1% 4 times a day for 2 weeks. Visual acuity, keratometry, and topography were measured 1 day, 1 week, 1, 3, and 6 months, and 1 year postoperatively. The astigmatism results were evaluated by vector analysis using the Holladay-Cravy-Koch formula. Statistical analysis was by the Wilcoxon test with the probability level at 1%.8
guard, and blade) of the blade holder.
Results noscan 4000 AP, Sonomed Inc.). Surgery was planned according to the topographic map findings. The knife used for surgery was chosen to cut approximately 90% of the paracentral (estimated incision area) corneal thickness.
The mean corneal astigmatism was ⫺4.00 ⫾ 1.10 diopters (D) (range ⫺2.20 to ⫺6.00 D) preoperatively and ⫺1.80 ⫾ 0.80 D (range ⫺0.60 to ⫺3.00 D) postoperatively. The difference in mean corneal myopic
Table 1. Terry nomogram. ATR Astigmatism
WTR Astigmatism
Diopters
OZ (mm)
Incisions (n)
Degrees
Incision Indicator
OZ (mm)
Incisions (n)
Degrees
Incision Indicator
1
10.0
1
90
4.5–4.5
8.0
2
60
3.0–3.0
2
10.0
2
60
3.0–3.0
8.0
2
80
4.0–4.0
3
10.0
2
80
4.0–4.0
8.0
2
100
5.0–5.0
4
10.0
2
100
5.0–5.0
—
—
—
—
ATR ⫽ against the rule; OZ ⫽ optical zone; WTR ⫽ with the rule
2398
J CATARACT REFRACT SURG—VOL 29, DECEMBER 2003
ASTIGMATIC SURGERY USING THE TERRY ASTIGMATOME
Figure 3. (Baykara) Preoperative (left) and postoperative (right) topographies in case 5.
astigmatism between preoperatively and 1 week postoperatively was statistically significant (P⬍.01). There was no statistically significant difference in the mean corneal myopic astigmatism between 1 week and 1 year (P⬎.05). The mean desired astigmatic correction was 3.00 ⫾ 0.59 D. The final surgically induced astigmatism was 2.50 ⫾ 0.60 D (Table 2). The mean uncorrected visual acuity (UCVA) was 0.74 ⫾ 0.25 preoperatively and 0.18 ⫾ 0.23 at 1 week. The mean final UCVA was 0.20 ⫾ 0.20. The difference
in the mean UCVA between preoperatively and postoperatively was statistically significant (P⬍.01). The mean best spectacle-corrected visual acuity (BSCVA) was 0.19 ⫾ 0.24 preoperatively and 0.19 ⫾ 0.23 at 1 week. The mean final BSCVA was 0.19 ⫾ 0.23. The difference in the mean BSCVA between preoperatively and postoperatively was statistically significant (P⬍.01). There was no statistically significant difference between the mean postoperative BSCVA and final BSCVA (P⬎.05) (Table 2).
Table 2. Patients’ characteristics and results. Age Case/Pt (Y) Sex Eye 1/1 2/2 3/2 4/3 5/4 6/5 7/6 8/7 9/8 10/8 11/9 12/9 13/10 14/10 15/11 16/11
45 27 27 30 31 39 28 52 51 51 39 39 21 21 32 32
M F F F M F M F M M M M F F F F
R R L R L R L L R L R L R L R L
Preop COA 4.7 3.5 3.0 4.7 5.2 3.0 6.0 4.4 4.0 2.2 3.8 2.2 4.8 4.8 4.8 4.9
⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻
21 98 80 87 162 86 166 86 93 93 97 153 82 86 103 69
Preop Preop MPCT SN UCVA BSCVA (m) (m) 1.0 0.5 0.5 0.7 1.0 0.7 1.0 0.7 1.0 0.4 0.7 0.2 1.0 1.0 0.7 0.7
0.7 0.3 0.1 0.1 0.5 0.1 0.7 0.1 0.0 0.0 0.2 0.0 0.0 0.0 0.1 0.0
595 580 594 610 637 590 655 570 580 615 600 560 650 640 620 610
550 550 550 550 550 550 600 500 500 550 550 500 600 600 550 550
Postop COA 3.0 1.4 1.4 1.8 2.8 1.0 3.0 1.8 0.8 0.6 1.5 1.0 3.0 2.7 2.1 2.1
⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻
3 82 80 80 179 87 169 84 103 110 120 146 87 84 89 60
Postop Des Post UCVA AC (D) BSCVA 0.7 0.0 0.0 0.1 0.4 0.0 0.7 0.1 0.0 0.0 0.1 0.1 0.2 0.2 0.1 0.2
4.0 3.0 3.0 3.0 4.0 3.0 4.0 3.0 3.0 2.0 3.0 2.0 3.0 3.0 3.0 3.0
0.7 0.0 0.0 0.1 0.4 0.0 0.5 0.0 0.0 0.1 0.0 0.1 0.0 0.0 0.1 0.0
SIA 2.88 2.43 1.60 2.99 3.28 2.00 3.00 2.60 3.30 1.80 3.00 1.25 1.90 2.11 3.11 3.00
⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻ ⫻
FU (Mo) CLV 40 107 80 91 148 86 163 87 91 88 86 159 74 89 122 75
12 9 9 11 9 19 11 16 16 15 14 13 11 11 8 8
Amb — — — Amb — Amb — — — — — — — — —
Amb ⫽ amblyopia; BSCVA ⫽ best spectacle-corrected visual acuity, logMAR; CLV ⫽ cause of low vision; COA ⫽ corneal astigmatism; Des AC ⫽ desired astigmatic correction; FU ⫽ follow-up; MPCT ⫽ mean paracentral corneal thickness; Pt ⫽ patient; SIA ⫽ surgically induced astigmatism; SN ⫽ surgical knife depth; UCVA ⫽ uncorrected visual acuity, logMAR
J CATARACT REFRACT SURG—VOL 29, DECEMBER 2003
2399
ASTIGMATIC SURGERY USING THE TERRY ASTIGMATOME
Increasingly effective corneal laser surgery techniques have been developed to treat myopia, hyperopia, and astigmatism. Thus, correction of higher corneal astigmatism can be performed.13 In conclusion, our results indicate that the Terry astigmatome, with its fixed depth cut and easy manipulation, is safe in the correction of astigmatism in selected patients. The creation of single or paired incisions was easily achieved.
References Figure 4. (Baykara) Postoperative photograph of the arcuate incisions in case 11.
No epithelial defects or perforations occurred. Figure 3 shows the preoperative and postoperative corneal topographies in case 5 and Figure 4, an anterior segment photograph of case 11.
Discussion Many refractive procedures have been developed to correct myopic astigmatism greater than 2.00 D. These include astigmatic keratotomy, refractive corneal laser techniques, and combined procedures.3–10 An arcuate incision causes relative flattening of the cornea in the axis of the incision with relative steepening at 90 degrees of the incision. This effect, known as coupling, varies with the location, number, depth, and length of the incision. Because the inferotemporal cornea is the thinnest zone, incisions made there are expected to be the deepest.3 Thus, it is important that the knife used for these incisions not cut deep enough to cause a perforation. In our study, the mean paracentral thickness was 606.4 ⫾ 29.3 m (range 560 to 650 m). The knives were chosen to cut on average 90% of corneal thickness of the estimated incision area. No perforations occurred, and the mean final refractive change was 2.50 ⫾ 0.60 D, confirming the appropriateness of the procedure and the desired correction (mean 3.00 ⫾ 0.59 D). Clinical and experimental ultrasonic biomicroscopic studies should be done to validate the incision depths and correlate them with refractive results. Astigmatic change can also be assessed by wavefront analysis.11,12
2400
1. Bear JC, Richler A. Cylindrical refractive error: a population study in western Newfoundland. Am J Optom Physiol Opt 1983; 60:39–45 2. Hirsch MJ. Changes in astigmatism during the first eight years of school—an interim report from the Ojai longitudinal study. Am J Optom 1963; 40:127–132 3. Ozcetin H. Astigmatic keratotomy. In: Ozcetin H, Sener B, eds, Treatment of Myopia. Istanbul, Nobel Press, 2002; 271–287 4. Hoffmann RF. The surgical correction of idiopathic astigmatism. In: Sanders DR, Hoffmann RF, Salz JJ, eds, Refractive Corneal Surgery. Thorofare, NJ, Slack, 1986; 241–290 5. Merlin U. Curved keratotomy procedure for congenital astigmatism. J Refract Surg 1987; 3:92–97 6. Budak K, Yılmaz G, Aslan BS, Duman S. Limbal relaxing incisions in congenital astigmatism: 6 month follow-up. J Cataract Refract Surg 2001; 27:715–719 7. Shimizu K, Misawa A, Suzuki Y. Toric intraocular lenses: correcting astigmatism while controlling axis shift. J Cataract Refract Surg 1994; 20:523–526 8. Gu¨ell JL, Vazquez M. Correction of high astigmatism with astigmatic keratotomy combined with laser in situ keratomileusis J Cataract Refract Surg 2000; 26: 960–966 9. Maloney WF, Sanders DR, Pearcy DE. Astigmatic keratotomy to correct preexisting astigmatism in cataract patients. J Cataract Refract Surg 1990; 16:297–304 10. Yang C-N, Shen EP, Hu F-R. Laser in situ keratomileusis for the correction of myopia and myopic astigmatism. J Cataract Refract Surg 2001; 27:1952–1960 11. Harris WF. Analysis of astigmatism in anterior segment surgery. J Cataract Refract Surg 2001; 27:107–128 12. Applegate RA, Hilmantel G, Howland HC, et al. Corneal first surface optical aberrations and visual performance. J Refract Surg 2000; 16:507–514 13. Sheludchenko VM, Rybintseva LV, Kurenkov VV. [Correction of high astigmatism and astigmatic anisometropia by intrastromal photokerato-ablation in children and adolescents]. [Russian] Vestn Oftalmol 2002; 118(4):18–22
J CATARACT REFRACT SURG—VOL 29, DECEMBER 2003