- Email: [email protected]
Photorefractive keratectomy for post-penetrating keratoplasty myopia and astigmatism1
Photorefractive keratectomy for post-penetrating keratoplasty myopia and astigmatism ¨ zdek, MD, Fikret Akata, MD, Kamil Bilgihan, MD, S¸engu¨l C. O Berati Hasanreisog˘lu, MD ABSTRACT Purpose: To determine the safety, effectiveness, and predictability of photorefractive keratectomy (PRK) for the correction of myopia and astigmatism after penetrating keratoplasty. Setting: Gazi University, Medical School, Department of Ophthalmology, Ankara, Turkey. Methods: Photorefractive keratectomy was performed in 16 eyes of 16 patients with postkeratoplasty myopia and astigmatism who were unable to wear glasses due to anisometropia and were contact lens intolerant. They were examined for uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and corneal transplant integrity before and after surgery. Results: The mean follow-up after PRK was 26.0 months ⫾ 15.7 (SD) (range 12 to 63 months). The mean preoperative spherical equivalent refraction of ⫺4.47 ⫾ 1.39 diopters (D) was ⫺3.39 ⫾ 1.84 D (P ⬎ .05) at the last postoperative visit and the mean preoperative cylinder of ⫺5.62 ⫾ 2.88 D was ⫺3.23 ⫾ 1.70 D (P ⬍ .05); refractive regression correlated with the amount of ablation performed. The BSCVA decreased in 3 eyes (18.8%), and the UCVA decreased in 2 (12.5%). Six eyes (37.5%) had grade 2 to 3 haze, which resolved spontaneously in 4 eyes within a relatively long time but caused a decrease in BSCVA in 2 (12.5%). Two of the eyes (12.5%) had a rejection episode after PRK and were successfully treated with topical steroids. Conclusions: Photorefractive keratectomy to correct postkeratoplasty myopia and astigmatism appears to be less effective and less predictable than PRK for naturally occurring myopia and astigmatism. Corneal haze and refractive regression are more prevalent, and patient satisfaction is not good. J Cataract Refract Surg 2000; 26: 1590 –1595 © 2000 ASCRS and ESCRS
A
main problem in successful visual rehabilitation of patients having penetrating keratoplasty (PKP) is postoperative astigmatism, which may reach 15.0 to 20.0 diopters (D), causing serious anisometropia. Many factors may cause excessive astigmatism, including pre-
Accepted for publicaton July 24, 2000. Reprint requests to Kamil Bilgihan, MD, Defne sitesi 3. Blok 53/10, ¨ mitko¨y, Ankara, Turkey. E-mail: [email protected]. 06530 U © 2000 ASCRS and ESCRS Published by Elsevier Science Inc.
existing corneal thinning and vascularization, eccentric trephination of the host, oversized grafts, preoperative keratoconus, astigmatism of the donor eye, and length, depth, tension, and configuration of corneal sutures. Visual rehabilitation with spectacles often yields an unsatisfactory visual outcome. Contact lenses are usually the first choice in such conditions; however, it is often difficult to fit them. Moreover, contact lenses may induce peripheral neovascularization, which increases the 0886-3350/00/$–see front matter PII S0886-3350(00)00692-1
PRK FOR POST-PKP MYOPIA AND ASTIGMATISM
risk of graft rejection. When these optical methods fail to provide adequate visual rehabilitation, surgical intervention may be warranted. Selective suture removal, single continuous suture adjustment, relaxing incisions, wedge resection, and astigmatic keratotomy are some alternatives for the surgical correction of post-PKP astigmatism.1 Photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) have been reported to yield promising results in the treatment of post-PKP myopia and astigmatism.1– 8 Most of the studies, however, are small series with relatively short follow-ups. We present the results of PRK for myopia and astigmatism occurring after PKP in 16 patients with a mean follow-up of 26 months.
end of the fifth post-PRK day in all eyes. After epithelial resurfacing, fluorometholone 0.1% was instilled 4 times a day for the first month and tapered 1 drop each month for the next 3 months. Postoperatively, patients were examined on each day until complete reepithelialization and then 1 week, 1, 3, 6, and 9 months, 1 year, and annually thereafter. Visual acuity (UCVA and BSCVA), cycloplegic refraction, haze grading, videokeratography, tonometry, and anterior and posterior segment examinations were recorded at each visit. A paired t test was used for statistical analysis of the preoperative and postoperative refractions, and Pearson correlation analysis was applied to study the relationship between ablation depth and regression and haze.
Patients and Methods
Results
The study was a noncontrolled prospective clinical trial of PRK for visual rehabilitation of myopia and astigmatism after PKP. All patients had postkeratoplasty myopic astigmatism. Keratoplasty sutures were removed at least 5 months before the refractive surgery. Patients were spectacle and contact lens intolerant. Informed consent included risks, benefits, and alternative treatment methods. Photorefractive keratectomy was performed 17 months to 9 years after corneal grafting. The preoperative evaluation included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), cycloplegic refraction, videokeratography (Tomey Topographic Modeling System, Computed Anatomy, Inc.), applanation tonometry, and anterior and posterior segment examinations. All surgery was performed by 2 surgeons (K.B., F.A.). Two to 3 drops of oxybuprocaine were instilled in the eye starting 5 minutes before surgery, and the epithelium was removed mechanically with a spatula. Target refraction was emmetropia in all patients; this was entered into the laser computer. The eyes were irradiated with a 193 nm excimer laser (Aesculap Meditec). The fluence at the cornea was 250 mJ/cm2, with a repetition rate of 20 Hz; the diameter of the ablation zone was between 5.0 and 6.0 mm in myopia 1 mask, 6.0 mm in myopia 2 mask, and 5.0 or 6.0 mm in myopia 3 mask. Postoperative treatment included topical ofloxacin (5 times a day) and occlusion until complete epithelial healing occurred. Epithelialization was complete by the
Sixteen eyes (8 right and 8 left) of 16 patients were treated by PRK to correct post-PKP myopia and astigmatism. Table 1 shows patient characteristics. The mean age of the 9 woman and 7 men was 28.4 years ⫾ 8.0 (SD). Fourteen eyes were grafted for keratoconus and 2, for corneal leukoma. The patients were followed for a mean of 26.0 ⫾ 15.7 months (range 12 to 63 months). Spherical Equivalent Refraction The mean preoperative value of ⫺4.47 ⫾ 1.39 D decreased to ⫺3.39 ⫾ 1.84 D by the last postoperative control visits, not a statistically significant difference (t ⫽ 1.95, P ⫽ .69). Although the preoperative spherical equivalent refraction decreased in most cases (13, 81%), it increased in 3 (19%). Regression of spherical equivalent refraction moderately correlated with the ablation level (correlation coefficient 0.42, P ⫽ .10). Refractive Cylinder The mean preoperative cylinder of ⫺5.62 ⫾ 2.88 D decreased to ⫺3.23 ⫾ 1.70 D postoperatively, which was statistically significantly lower than the preoperative value (t ⫽ 4.03, P ⫽ .01). Two eyes had a postoperative cylinder that was greater than the preoperative value (cases 8 and 10). Refractive cyclinder decreased in all others. Regression of postoperative refractive cyclinder correlated significantly with the ablation depth (correlation
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Table 1. Patient data.
Case
Age/ Sex
1
29/M
2
Pre-PRK
Post-PRK
UCVA
BSCVA
Refraction
Follow-up (Months)
Leukoma
20/100
20/25
⫺3.00 ⫺1.50 ⫻ 70
38
20/100
20/32
⫺0.75 ⫺1.50 ⫻ 50
30/M
Keratoconus
20/125
20/25
⫺1.50 ⫺5.00 ⫻ 60
12
20/100
20/25
⫺2.00 ⫺3.50 ⫻ 70
3
25/F
Keratoconus
20/100
20/20
Plano ⫺6.00 ⫻ 90
12
20/32
20/20
⫺1.25 ⫺2.50 ⫻ 70
4
18/F
Keratoconus
20/125
20/25
⫺3.00 ⫺3.00 ⫻ 30
14
20/50
20/25
⫺2.00 ⫺2.00 ⫻ 30
5
51/M
Leukoma
20/100
20/50
Plano ⫺4.00 ⫻ 180
13
20/100
20/50
⫹1.00 ⫺1.50 ⫻ 160
6
26/F
Keratoconus
20/200
20/63
Plano ⫺10.00 ⫻ 125
23
20/200
20/80
⫺2.00 ⫺5.50 ⫻ 100
Diagnosis
UCVA
BSCVA
Refraction
20/40
Plano ⫺10.00 ⫻ 135
19
20/32
20/32
⫹3.00 ⫺4.00 ⫻ 104
20/20
⫺1.50 ⫺2.50 ⫻ 180
35
20/100
20/20
⫺2.50 ⫺3.50 ⫻ 170
FC
20/32
⫺4.00 ⫺3.00 ⫻ 140
22
20/40*
20/25*
⫺1.00 ⫺2.00 ⫻ 20*
FC
20/32
⫺1.50 ⫺5.00 ⫻ 30
36
20/125*
20/32*
Plano ⫺7.00 ⫻ 45*
Keratoconus
FC
20/32
⫺5.00 ⫺5.00 ⫻ 130
63
20/50
20/32
⫺2.00 ⫺1.50 ⫻ 120
Keratoconus
20/200
20/32
⫺4.00 ⫺4.25 ⫻ 110
56
20/50
20/32
⫺2.00 ⫺3.00 ⫻ 100
34/F
Keratoconus
FC
20/100
25
20/200
20/100
⫺8.00 ⫺3.00 ⫻ 100
14
31/F
Keratoconus
20/200
20/32
⫺3.00 ⫺5.00 ⫻ 160
22
20/100
20/32
⫺1.00 ⫺3.00 ⫻ 170
15
21/M
Keratoconus
20/100
20/40
Plano ⫺6.00 ⫻ 175
13
20/25
20/20
⫹2.00 ⫺3.00 ⫻ 160
16
16/M
Keratoconus
20/50
20/25
Plano ⫺10.00 ⫻ 160
13
20/63
20/32
Plano ⫺6.00 ⫻ 140
7
35/M
Keratoconus
8
28/M
Keratoconus
9
29/F
Keratoconus
10
22/F
Keratoconus
11
32/F
12
28/F
13
FC 20/32
Plano ⫺10.00 ⫻ 90
PRK ⫽ photorefractive keratectomy; UCVA ⫽ uncorrected visual acuity; BSCVA ⫽ best spectacle-corrected visual acuity; FC ⫽ finger counting *Post-PTK findings
coefficient 0.65, P ⫽ .006) (Figure 1), and it was observed to progress up to 5 years in patients with a sufficient follow-up (Figure 2). Visual Acuity The UCVA was ⱕ20/100 in all but 2 eyes preoperatively; it was ⱖ20/40 in 4 eyes (25%), ⱖ20/70 in 8
(50%), and ⱖ20/100 in 13 (81%) postoperatively. The BSCVA was ⱖ20/40 in 13 eyes before and after PRK and ⱖ20/25 in 6 (37%). There was no change in 10 eyes (62%), an increase in 3 eyes (19%), and 1 line of loss in 3 eyes postoperatively. Two eyes (12%) lost UCVA (Figure 3). Two eyes (12%) achieved a UCVA as good as or better than the preoperative BSCVA.
Figure 1. (Bilgihan) Relationship between ablation level and astigmatic regression.
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PRK FOR POST-PKP MYOPIA AND ASTIGMATISM
Discussion
Figure 2. (Bilgihan) Postoperative corneal topographies of case 11. A: Six months postoperative. B: Five years postoperative. A–B: Difference map showing progressive regression.
Haze and Complications Haze was mild or transient in most eyes, but grade 2 or more was observed in 6 (37.5%) (Table 2). Haze formation tended to occur late (mostly after 6 months) and was parallel to the regression in these cases. Formation of haze was significantly correlated with the ablation depth (correlation coefficient 0.51, P ⫽ .04). This late-occurring haze resolved spontaneously in most patients within a relatively long time (by the end of the 12th month), although regression continued at that time. Reablation as phototherapeutic keratectomy (PTK) was performed to clear the haze in 2 of these cases (12.5%) that had a line loss of BSCVA (cases 9 and 10). Forty microns of PTK was applied at 10 and 12 months and resulted in a satisfactory visual outcome in case 9 but not in case 10 because of the high residual astigmatism. Retreatment as LASIK or PTK is planned for the other 2 with an impaired BSCVA. Although case 13 had a large regression and grade 2 haze formation, retreatment was not planned because the patient had degenerative myopia and her vision increased only 1 line with this correction. Two patients (12.5%) experienced an endothelial graft rejection episode after the PRK procedure at the 5th month (case 1) and the 10th day (case 7) postoperatively (Table 2). They were treated successfully with topical steroids, and none of the episodes resulted in loss of the graft.
Postkeratoplasty myopia and astigmatism are the major causes of poor optical performance of a graft. Although it is encountered in all transplants, it appears to be more prevalent in keratoconus cases, which may be due to the differences in stromal thickness. This was true in our patient group, which was composed primarily of keratoconus cases. Unfortunately, the results of surgery for postkeratoplasty refractive errors are not always curative and predictable. The reported complication of graft rejection that can occur after refractive surgery is of even greater concern.9 The effectiveness of PRK for the treatment of naturally occurring astigmatism has been demonstrated by several authors.10,11 However, a previously transplanted cornea may respond to PRK differently than one that has not had surgery since corneal wound healing in a grafted eye might differ from the normal wound-healing response of the cornea. Although the results in the literature are challenging, making it difficult to derive meaningful conclusions, most previous studies of PRK after PKP show a higher rate of regression of refractive effect and a late-developing corneal haze, often impairing the BSCVA.2–5 The most serious complication in our study was late-occurring haze and progressive regression, which caused a decrease in BSCVA in 4 patients (25%), 2 of whom were treated with PTK; retreatment was planned for the others. Chan and coauthors12 report a case with corneal scarring after 182 m of PRK in a graft that recurred after the retreatment and resulted in a repeat PKP. Tuunanen and coauthors4 hypothesize that the ablation of anterior stromal nerves in PRK may add to the already abnormal innervation of the graft and may contribute to the more pronounced tendency toward formation of regression and haze in these patients. The results of the previous studies and those of our study suggest that haze formation may be more prevalent after PRK for post-PKP refractive errors. However, we observed a spontaneous resolution of this late-occurring haze in most patients within a relatively long time. The late-occurring progressive refractive regression was associated with this haze. Ablation depth was relatively high in our patients, which is expected to result in more regression and haze in eyes with naturally occurring refractive errors. Likewise, regression and haze increased
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Figure 3. (Bilgihan) Gain and loss of UCVA and BSCVA over time.
proportionally with increasing ablation depth in our study. The goal of therapeutic PRK for visual rehabilitation after PKP is not necessarily the same as PRK for the correction of naturally occurring myopia or astigmatism. The primary goal of PRK after PKP is resolution of sufficient myopia and astigmatism to allow spectacle correction of the residual refractive error. The UCVA remains a secondary goal, although it is clearly the primary objective of cosmetic PRK. In this study, only 2 eyes achieved postoperative UCVA as good as or better than the preoperative BSCVA, which is the main parameter for evaluating efficacy of cosmetic PRK. In this study, we demonstrated a 24% reduction in spherical equivalent refraction and a 42% reduction in refractive astigmatism; these are similar to the results of previous studies.2,3,13 Our results suggest that PRK reduces astigmatism more effectively than spherical myopia after PKP. Relaxing incisions, a simpler and cheaper refractive surgical technique, is reported to cause a mean reduction in postkeratoplasty astigmatism of 4.7 to 5.0 D,14,15 which are at least comparable to the results of this study. The major disadvantages were unpredictability in each particular case, the tendency of the topography to irregularity, and possible regression of the effect. Laser in situ keratomileusis may be preferable as it elicits less of a wound-healing response in the complex immunological environment of the grafted cornea.6,8 Although there is not a consensus between studies,16,17 corneal sensation appears to be better after LASIK than after PRK, which may improve graft survival.16 The 1594
main problems reported with LASIK, however, are the probability of a change in the preoperative refraction after the microkeratome passes through the graft– host junction (M.S. Kritzinger, MD, “Corneal Transplant Patients Fare Better with LASIK than PRK,” Ocular Surgery News, February 1, 1998, page 34) and corneal dehiscence from the high pressure (60 mmHg) applied
Table 2. Ablation depth and complications.
Case
Ablation Haze Rejection (m) (Grade 1 to 4) Tx
Retreatment
1
50
—
⫹
—
2
73
1
⫺
—
3
60
—
⫺
—
4
59
1
⫺
—
5
66
1
⫺
—
6
96
2
⫺
LASIK planned
7
96
—
⫹
—
8
69
—
⫺
—
9
69
2
⫺
PTK 3 (haze–)
10
99
3
⫺
PTK 3 (haze 1)
11
92
—
⫺
—
12
80
—
⫺
—
13
96
2
⫺
—
14
98
2
⫺
—
15
92
—
⫺
—
16
96
3
⫺
PTK planned
LASIK ⫽ laser in situ keratomileusis; PTK ⫽ phototherapeutic keratectomy
J CATARACT REFRACT SURG—VOL 26, NOVEMBER 2000
PRK FOR POST-PKP MYOPIA AND ASTIGMATISM
by the suction ring of the microkeratome. Laser in situ keratomileusis has also been reported to be as effective in the treatment of residual refractive errors after PRK,18 and retreatment with LASIK has been planned for our cases with high regression. Rejection reactions in 2 cases, although controlled with medical treatment, raised a question in our minds about the safety of this treatment modality in corneal grafted patients. Since the first case experienced the reaction 5 months post-PRK, we cannot be sure that the episode was triggered by the PRK procedure. In case 8, however, the rejection reaction started at the end of the first postoperative week, which suggests that it was triggered by the mechanical trauma of the laser surgery. Both rejection reactions were treated effectively with topical steroids and did not result in graft failure. In conclusion, this study demonstrated that the long-term results of PRK for postkeratoplasty myopia and astigmatism are not similar to the results in eyes with naturally occurring myopia and astigmatism. There is more tendency for haze formation with a resultant progressive regression in these eyes, which is positively correlated with the ablation depth. Laser surgery may trigger a rejection reaction in the grafts.
8.
9.
10.
11.
12.
13.
14.
15.
References 1. Riddle HK Jr, Parker DAS, Price FW Jr. Management of postkeratoplasty astigmatism. Curr Opin Ophthalmol 1998; 9:15–28 2. Campos M, Hertzog L, Garbus J, et al. Photorefractive keratectomy for severe postkeratoplasty astigmatism. Am J Ophthalmol 1992; 114:429 – 436 3. Lazzaro DR, Haight DH, Belmont SC, et al. Excimer laser keratectomy for astigmatism occurring after penetrating keratoplasty. Ophthalmology 1996; 103: 458 – 464 4. Tuunanen TH, Ruusuvaara PJ, Uusitalo RJ, Tervo TM. Photoastigmatic keratectomy for correction of astigmatism in corneal grafts. Cornea 1997; 16:48 –53 5. Bansal AK. Photoastigmatic refractive keratectomy for correction of astigmatism after keratoplasty. J Refract Surg 1999; 15:S243–S245 6. Arenas E, Maglione A. Laser in situ keratomileusis for astigmatism and myopia after penetrating keratoplasty. J Refract Surg 1997; 13:27–32 7. Nordan LT, Binder PS, Kassar BS, et al. Photorefractive keratectomy to treat myopia and astigmatism after radial
16.
17.
18.
keratotomy and penetrating keratoplasty. J Cataract Refract Surg 1995; 21:268 –273 Donnenfeld ED, Kornstein HS, Amin A, et al. Laser in situ keratomileusis for correction of myopia and astigmatism after penetrating keratoplasty. Ophthalmology 1999; 106:1966 –1974; discussion by JH Talamo, 1974 – 1975 Mandel MR, Shapiro MB, Krachmer JH. Relaxing incisions with augmentation sutures for the correction of postkeratoplasty astigmatism. Am J Ophthalmol 1987; 103:441– 447 Taylor HR, Kelly P, Alpins N. Excimer laser correction of myopic astigmatism. J Cataract Refract Surg 1994; 20: 243–251 Kremer I, Gabbay U, Blumenthal M. One-year follow-up results of photorefractive keratectomy for low, moderate, and high primary astigmatism. Ophthalmology 1996; 103:741–748 Chan W-K, Hunt KE, Glasgow BJ, Mondino BJ. Corneal scarring after photorefractive keratectomy in a penetrating keratoplasty. Am J Ophthalmol 1996; 121:570 – 571 Yoshida K, Tazawa Y, Demong TT. Refractive results of post penetrating keratoplasty photorefractive keratectomy. Ophthalmic Surg Lasers 1999; 30:354 –359 Kirkness CM, Ficker LA, Steele McGAD, Rice NSC. Refractive surgery for graft-induced astigmatism after penetrating keratoplasty for keratoconus. Ophthalmology 1991; 98:1786 –1792 Vilchis E, Seitz B, Langenbucher A, et al. Limbusparallele Keratotomien mit Kompressionsna¨hten zur Behandlung des hohen Astigmatismus nach perforierender Keratoplastik: Eine vektoranalytische und topographisc Studie. Klin Monatsbl Augenheilkd 1997; 211:151–158 Kanellopoulos AJ, Pallikaris IG, Donnenfeld ED, et al. Comparison of corneal sensation following photorefractive keratectomy and laser in situ keratomileusis. J Cataract Refract Surg 1997; 23:34 –38 Pe´rez-Santonja JJ, Sakla HF, Cardona C, et al. Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia. Am J Ophthalmol 1999; 127:497–504 ¨ zdamar A, S¸ener B, Aras C, Aktunc¸ R. Laser in situ O keratomileusis after photorefractive keratectomy for myopic regression. J Cataract Refract Surg 1998; 24:1208 – 1211
From Gazi University, School of Medicine, Ophthalmology Department, Ankara, Turkey. None of the authors has a financial interest in any product mentioned.
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A
main problem in successful visual rehabilitation of patients having penetrating keratoplasty (PKP) is postoperative astigmatism, which may reach 15.0 to 20.0 diopters (D), causing serious anisometropia. Many factors may cause excessive astigmatism, including pre-
Accepted for publicaton July 24, 2000. Reprint requests to Kamil Bilgihan, MD, Defne sitesi 3. Blok 53/10, ¨ mitko¨y, Ankara, Turkey. E-mail: [email protected]. 06530 U © 2000 ASCRS and ESCRS Published by Elsevier Science Inc.
existing corneal thinning and vascularization, eccentric trephination of the host, oversized grafts, preoperative keratoconus, astigmatism of the donor eye, and length, depth, tension, and configuration of corneal sutures. Visual rehabilitation with spectacles often yields an unsatisfactory visual outcome. Contact lenses are usually the first choice in such conditions; however, it is often difficult to fit them. Moreover, contact lenses may induce peripheral neovascularization, which increases the 0886-3350/00/$–see front matter PII S0886-3350(00)00692-1
PRK FOR POST-PKP MYOPIA AND ASTIGMATISM
risk of graft rejection. When these optical methods fail to provide adequate visual rehabilitation, surgical intervention may be warranted. Selective suture removal, single continuous suture adjustment, relaxing incisions, wedge resection, and astigmatic keratotomy are some alternatives for the surgical correction of post-PKP astigmatism.1 Photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) have been reported to yield promising results in the treatment of post-PKP myopia and astigmatism.1– 8 Most of the studies, however, are small series with relatively short follow-ups. We present the results of PRK for myopia and astigmatism occurring after PKP in 16 patients with a mean follow-up of 26 months.
end of the fifth post-PRK day in all eyes. After epithelial resurfacing, fluorometholone 0.1% was instilled 4 times a day for the first month and tapered 1 drop each month for the next 3 months. Postoperatively, patients were examined on each day until complete reepithelialization and then 1 week, 1, 3, 6, and 9 months, 1 year, and annually thereafter. Visual acuity (UCVA and BSCVA), cycloplegic refraction, haze grading, videokeratography, tonometry, and anterior and posterior segment examinations were recorded at each visit. A paired t test was used for statistical analysis of the preoperative and postoperative refractions, and Pearson correlation analysis was applied to study the relationship between ablation depth and regression and haze.
Patients and Methods
Results
The study was a noncontrolled prospective clinical trial of PRK for visual rehabilitation of myopia and astigmatism after PKP. All patients had postkeratoplasty myopic astigmatism. Keratoplasty sutures were removed at least 5 months before the refractive surgery. Patients were spectacle and contact lens intolerant. Informed consent included risks, benefits, and alternative treatment methods. Photorefractive keratectomy was performed 17 months to 9 years after corneal grafting. The preoperative evaluation included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), cycloplegic refraction, videokeratography (Tomey Topographic Modeling System, Computed Anatomy, Inc.), applanation tonometry, and anterior and posterior segment examinations. All surgery was performed by 2 surgeons (K.B., F.A.). Two to 3 drops of oxybuprocaine were instilled in the eye starting 5 minutes before surgery, and the epithelium was removed mechanically with a spatula. Target refraction was emmetropia in all patients; this was entered into the laser computer. The eyes were irradiated with a 193 nm excimer laser (Aesculap Meditec). The fluence at the cornea was 250 mJ/cm2, with a repetition rate of 20 Hz; the diameter of the ablation zone was between 5.0 and 6.0 mm in myopia 1 mask, 6.0 mm in myopia 2 mask, and 5.0 or 6.0 mm in myopia 3 mask. Postoperative treatment included topical ofloxacin (5 times a day) and occlusion until complete epithelial healing occurred. Epithelialization was complete by the
Sixteen eyes (8 right and 8 left) of 16 patients were treated by PRK to correct post-PKP myopia and astigmatism. Table 1 shows patient characteristics. The mean age of the 9 woman and 7 men was 28.4 years ⫾ 8.0 (SD). Fourteen eyes were grafted for keratoconus and 2, for corneal leukoma. The patients were followed for a mean of 26.0 ⫾ 15.7 months (range 12 to 63 months). Spherical Equivalent Refraction The mean preoperative value of ⫺4.47 ⫾ 1.39 D decreased to ⫺3.39 ⫾ 1.84 D by the last postoperative control visits, not a statistically significant difference (t ⫽ 1.95, P ⫽ .69). Although the preoperative spherical equivalent refraction decreased in most cases (13, 81%), it increased in 3 (19%). Regression of spherical equivalent refraction moderately correlated with the ablation level (correlation coefficient 0.42, P ⫽ .10). Refractive Cylinder The mean preoperative cylinder of ⫺5.62 ⫾ 2.88 D decreased to ⫺3.23 ⫾ 1.70 D postoperatively, which was statistically significantly lower than the preoperative value (t ⫽ 4.03, P ⫽ .01). Two eyes had a postoperative cylinder that was greater than the preoperative value (cases 8 and 10). Refractive cyclinder decreased in all others. Regression of postoperative refractive cyclinder correlated significantly with the ablation depth (correlation
J CATARACT REFRACT SURG—VOL 26, NOVEMBER 2000
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Table 1. Patient data.
Case
Age/ Sex
1
29/M
2
Pre-PRK
Post-PRK
UCVA
BSCVA
Refraction
Follow-up (Months)
Leukoma
20/100
20/25
⫺3.00 ⫺1.50 ⫻ 70
38
20/100
20/32
⫺0.75 ⫺1.50 ⫻ 50
30/M
Keratoconus
20/125
20/25
⫺1.50 ⫺5.00 ⫻ 60
12
20/100
20/25
⫺2.00 ⫺3.50 ⫻ 70
3
25/F
Keratoconus
20/100
20/20
Plano ⫺6.00 ⫻ 90
12
20/32
20/20
⫺1.25 ⫺2.50 ⫻ 70
4
18/F
Keratoconus
20/125
20/25
⫺3.00 ⫺3.00 ⫻ 30
14
20/50
20/25
⫺2.00 ⫺2.00 ⫻ 30
5
51/M
Leukoma
20/100
20/50
Plano ⫺4.00 ⫻ 180
13
20/100
20/50
⫹1.00 ⫺1.50 ⫻ 160
6
26/F
Keratoconus
20/200
20/63
Plano ⫺10.00 ⫻ 125
23
20/200
20/80
⫺2.00 ⫺5.50 ⫻ 100
Diagnosis
UCVA
BSCVA
Refraction
20/40
Plano ⫺10.00 ⫻ 135
19
20/32
20/32
⫹3.00 ⫺4.00 ⫻ 104
20/20
⫺1.50 ⫺2.50 ⫻ 180
35
20/100
20/20
⫺2.50 ⫺3.50 ⫻ 170
FC
20/32
⫺4.00 ⫺3.00 ⫻ 140
22
20/40*
20/25*
⫺1.00 ⫺2.00 ⫻ 20*
FC
20/32
⫺1.50 ⫺5.00 ⫻ 30
36
20/125*
20/32*
Plano ⫺7.00 ⫻ 45*
Keratoconus
FC
20/32
⫺5.00 ⫺5.00 ⫻ 130
63
20/50
20/32
⫺2.00 ⫺1.50 ⫻ 120
Keratoconus
20/200
20/32
⫺4.00 ⫺4.25 ⫻ 110
56
20/50
20/32
⫺2.00 ⫺3.00 ⫻ 100
34/F
Keratoconus
FC
20/100
25
20/200
20/100
⫺8.00 ⫺3.00 ⫻ 100
14
31/F
Keratoconus
20/200
20/32
⫺3.00 ⫺5.00 ⫻ 160
22
20/100
20/32
⫺1.00 ⫺3.00 ⫻ 170
15
21/M
Keratoconus
20/100
20/40
Plano ⫺6.00 ⫻ 175
13
20/25
20/20
⫹2.00 ⫺3.00 ⫻ 160
16
16/M
Keratoconus
20/50
20/25
Plano ⫺10.00 ⫻ 160
13
20/63
20/32
Plano ⫺6.00 ⫻ 140
7
35/M
Keratoconus
8
28/M
Keratoconus
9
29/F
Keratoconus
10
22/F
Keratoconus
11
32/F
12
28/F
13
FC 20/32
Plano ⫺10.00 ⫻ 90
PRK ⫽ photorefractive keratectomy; UCVA ⫽ uncorrected visual acuity; BSCVA ⫽ best spectacle-corrected visual acuity; FC ⫽ finger counting *Post-PTK findings
coefficient 0.65, P ⫽ .006) (Figure 1), and it was observed to progress up to 5 years in patients with a sufficient follow-up (Figure 2). Visual Acuity The UCVA was ⱕ20/100 in all but 2 eyes preoperatively; it was ⱖ20/40 in 4 eyes (25%), ⱖ20/70 in 8
(50%), and ⱖ20/100 in 13 (81%) postoperatively. The BSCVA was ⱖ20/40 in 13 eyes before and after PRK and ⱖ20/25 in 6 (37%). There was no change in 10 eyes (62%), an increase in 3 eyes (19%), and 1 line of loss in 3 eyes postoperatively. Two eyes (12%) lost UCVA (Figure 3). Two eyes (12%) achieved a UCVA as good as or better than the preoperative BSCVA.
Figure 1. (Bilgihan) Relationship between ablation level and astigmatic regression.
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Discussion
Figure 2. (Bilgihan) Postoperative corneal topographies of case 11. A: Six months postoperative. B: Five years postoperative. A–B: Difference map showing progressive regression.
Haze and Complications Haze was mild or transient in most eyes, but grade 2 or more was observed in 6 (37.5%) (Table 2). Haze formation tended to occur late (mostly after 6 months) and was parallel to the regression in these cases. Formation of haze was significantly correlated with the ablation depth (correlation coefficient 0.51, P ⫽ .04). This late-occurring haze resolved spontaneously in most patients within a relatively long time (by the end of the 12th month), although regression continued at that time. Reablation as phototherapeutic keratectomy (PTK) was performed to clear the haze in 2 of these cases (12.5%) that had a line loss of BSCVA (cases 9 and 10). Forty microns of PTK was applied at 10 and 12 months and resulted in a satisfactory visual outcome in case 9 but not in case 10 because of the high residual astigmatism. Retreatment as LASIK or PTK is planned for the other 2 with an impaired BSCVA. Although case 13 had a large regression and grade 2 haze formation, retreatment was not planned because the patient had degenerative myopia and her vision increased only 1 line with this correction. Two patients (12.5%) experienced an endothelial graft rejection episode after the PRK procedure at the 5th month (case 1) and the 10th day (case 7) postoperatively (Table 2). They were treated successfully with topical steroids, and none of the episodes resulted in loss of the graft.
Postkeratoplasty myopia and astigmatism are the major causes of poor optical performance of a graft. Although it is encountered in all transplants, it appears to be more prevalent in keratoconus cases, which may be due to the differences in stromal thickness. This was true in our patient group, which was composed primarily of keratoconus cases. Unfortunately, the results of surgery for postkeratoplasty refractive errors are not always curative and predictable. The reported complication of graft rejection that can occur after refractive surgery is of even greater concern.9 The effectiveness of PRK for the treatment of naturally occurring astigmatism has been demonstrated by several authors.10,11 However, a previously transplanted cornea may respond to PRK differently than one that has not had surgery since corneal wound healing in a grafted eye might differ from the normal wound-healing response of the cornea. Although the results in the literature are challenging, making it difficult to derive meaningful conclusions, most previous studies of PRK after PKP show a higher rate of regression of refractive effect and a late-developing corneal haze, often impairing the BSCVA.2–5 The most serious complication in our study was late-occurring haze and progressive regression, which caused a decrease in BSCVA in 4 patients (25%), 2 of whom were treated with PTK; retreatment was planned for the others. Chan and coauthors12 report a case with corneal scarring after 182 m of PRK in a graft that recurred after the retreatment and resulted in a repeat PKP. Tuunanen and coauthors4 hypothesize that the ablation of anterior stromal nerves in PRK may add to the already abnormal innervation of the graft and may contribute to the more pronounced tendency toward formation of regression and haze in these patients. The results of the previous studies and those of our study suggest that haze formation may be more prevalent after PRK for post-PKP refractive errors. However, we observed a spontaneous resolution of this late-occurring haze in most patients within a relatively long time. The late-occurring progressive refractive regression was associated with this haze. Ablation depth was relatively high in our patients, which is expected to result in more regression and haze in eyes with naturally occurring refractive errors. Likewise, regression and haze increased
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Figure 3. (Bilgihan) Gain and loss of UCVA and BSCVA over time.
proportionally with increasing ablation depth in our study. The goal of therapeutic PRK for visual rehabilitation after PKP is not necessarily the same as PRK for the correction of naturally occurring myopia or astigmatism. The primary goal of PRK after PKP is resolution of sufficient myopia and astigmatism to allow spectacle correction of the residual refractive error. The UCVA remains a secondary goal, although it is clearly the primary objective of cosmetic PRK. In this study, only 2 eyes achieved postoperative UCVA as good as or better than the preoperative BSCVA, which is the main parameter for evaluating efficacy of cosmetic PRK. In this study, we demonstrated a 24% reduction in spherical equivalent refraction and a 42% reduction in refractive astigmatism; these are similar to the results of previous studies.2,3,13 Our results suggest that PRK reduces astigmatism more effectively than spherical myopia after PKP. Relaxing incisions, a simpler and cheaper refractive surgical technique, is reported to cause a mean reduction in postkeratoplasty astigmatism of 4.7 to 5.0 D,14,15 which are at least comparable to the results of this study. The major disadvantages were unpredictability in each particular case, the tendency of the topography to irregularity, and possible regression of the effect. Laser in situ keratomileusis may be preferable as it elicits less of a wound-healing response in the complex immunological environment of the grafted cornea.6,8 Although there is not a consensus between studies,16,17 corneal sensation appears to be better after LASIK than after PRK, which may improve graft survival.16 The 1594
main problems reported with LASIK, however, are the probability of a change in the preoperative refraction after the microkeratome passes through the graft– host junction (M.S. Kritzinger, MD, “Corneal Transplant Patients Fare Better with LASIK than PRK,” Ocular Surgery News, February 1, 1998, page 34) and corneal dehiscence from the high pressure (60 mmHg) applied
Table 2. Ablation depth and complications.
Case
Ablation Haze Rejection (m) (Grade 1 to 4) Tx
Retreatment
1
50
—
⫹
—
2
73
1
⫺
—
3
60
—
⫺
—
4
59
1
⫺
—
5
66
1
⫺
—
6
96
2
⫺
LASIK planned
7
96
—
⫹
—
8
69
—
⫺
—
9
69
2
⫺
PTK 3 (haze–)
10
99
3
⫺
PTK 3 (haze 1)
11
92
—
⫺
—
12
80
—
⫺
—
13
96
2
⫺
—
14
98
2
⫺
—
15
92
—
⫺
—
16
96
3
⫺
PTK planned
LASIK ⫽ laser in situ keratomileusis; PTK ⫽ phototherapeutic keratectomy
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by the suction ring of the microkeratome. Laser in situ keratomileusis has also been reported to be as effective in the treatment of residual refractive errors after PRK,18 and retreatment with LASIK has been planned for our cases with high regression. Rejection reactions in 2 cases, although controlled with medical treatment, raised a question in our minds about the safety of this treatment modality in corneal grafted patients. Since the first case experienced the reaction 5 months post-PRK, we cannot be sure that the episode was triggered by the PRK procedure. In case 8, however, the rejection reaction started at the end of the first postoperative week, which suggests that it was triggered by the mechanical trauma of the laser surgery. Both rejection reactions were treated effectively with topical steroids and did not result in graft failure. In conclusion, this study demonstrated that the long-term results of PRK for postkeratoplasty myopia and astigmatism are not similar to the results in eyes with naturally occurring myopia and astigmatism. There is more tendency for haze formation with a resultant progressive regression in these eyes, which is positively correlated with the ablation depth. Laser surgery may trigger a rejection reaction in the grafts.
8.
9.
10.
11.
12.
13.
14.
15.
References 1. Riddle HK Jr, Parker DAS, Price FW Jr. Management of postkeratoplasty astigmatism. Curr Opin Ophthalmol 1998; 9:15–28 2. Campos M, Hertzog L, Garbus J, et al. Photorefractive keratectomy for severe postkeratoplasty astigmatism. Am J Ophthalmol 1992; 114:429 – 436 3. Lazzaro DR, Haight DH, Belmont SC, et al. Excimer laser keratectomy for astigmatism occurring after penetrating keratoplasty. Ophthalmology 1996; 103: 458 – 464 4. Tuunanen TH, Ruusuvaara PJ, Uusitalo RJ, Tervo TM. Photoastigmatic keratectomy for correction of astigmatism in corneal grafts. Cornea 1997; 16:48 –53 5. Bansal AK. Photoastigmatic refractive keratectomy for correction of astigmatism after keratoplasty. J Refract Surg 1999; 15:S243–S245 6. Arenas E, Maglione A. Laser in situ keratomileusis for astigmatism and myopia after penetrating keratoplasty. J Refract Surg 1997; 13:27–32 7. Nordan LT, Binder PS, Kassar BS, et al. Photorefractive keratectomy to treat myopia and astigmatism after radial
16.
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18.
keratotomy and penetrating keratoplasty. J Cataract Refract Surg 1995; 21:268 –273 Donnenfeld ED, Kornstein HS, Amin A, et al. Laser in situ keratomileusis for correction of myopia and astigmatism after penetrating keratoplasty. Ophthalmology 1999; 106:1966 –1974; discussion by JH Talamo, 1974 – 1975 Mandel MR, Shapiro MB, Krachmer JH. Relaxing incisions with augmentation sutures for the correction of postkeratoplasty astigmatism. Am J Ophthalmol 1987; 103:441– 447 Taylor HR, Kelly P, Alpins N. Excimer laser correction of myopic astigmatism. J Cataract Refract Surg 1994; 20: 243–251 Kremer I, Gabbay U, Blumenthal M. One-year follow-up results of photorefractive keratectomy for low, moderate, and high primary astigmatism. Ophthalmology 1996; 103:741–748 Chan W-K, Hunt KE, Glasgow BJ, Mondino BJ. Corneal scarring after photorefractive keratectomy in a penetrating keratoplasty. Am J Ophthalmol 1996; 121:570 – 571 Yoshida K, Tazawa Y, Demong TT. Refractive results of post penetrating keratoplasty photorefractive keratectomy. Ophthalmic Surg Lasers 1999; 30:354 –359 Kirkness CM, Ficker LA, Steele McGAD, Rice NSC. Refractive surgery for graft-induced astigmatism after penetrating keratoplasty for keratoconus. Ophthalmology 1991; 98:1786 –1792 Vilchis E, Seitz B, Langenbucher A, et al. Limbusparallele Keratotomien mit Kompressionsna¨hten zur Behandlung des hohen Astigmatismus nach perforierender Keratoplastik: Eine vektoranalytische und topographisc Studie. Klin Monatsbl Augenheilkd 1997; 211:151–158 Kanellopoulos AJ, Pallikaris IG, Donnenfeld ED, et al. Comparison of corneal sensation following photorefractive keratectomy and laser in situ keratomileusis. J Cataract Refract Surg 1997; 23:34 –38 Pe´rez-Santonja JJ, Sakla HF, Cardona C, et al. Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia. Am J Ophthalmol 1999; 127:497–504 ¨ zdamar A, S¸ener B, Aras C, Aktunc¸ R. Laser in situ O keratomileusis after photorefractive keratectomy for myopic regression. J Cataract Refract Surg 1998; 24:1208 – 1211
From Gazi University, School of Medicine, Ophthalmology Department, Ankara, Turkey. None of the authors has a financial interest in any product mentioned.
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