Ординатура / Офтальмология / Английские материалы / LASIK and Beyond LASIK Wavefront Analysis and Customized Ablation_Boyd_2001
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–1.19 ± 0.71 (SD) (P<0.05) in the RK group, and from –3.38 ± 1.3 (SD) to –0.4 ± 0.5 (SD) (P<0.005) in the PRK group. Uncorrected visual acuity was improved from 0.07 ± 0.05 (SD) to 0.63 ± 0 .19 (SD) (P<0.05) in the RK patients, and from 0.25 ± 012(SD) to 0.87 ± 0.22 (SD) (P<0.05) in the PRK group. Two eyes in the RK group and three eyes in the PRK group gained one line of BCVA. Two eyes in the RK group lost one line of BCVA. No complications that jeopardize sight, like free flap, corneal ectasia, or any retinal complication occurred. There was no statistically significant difference in corneal haze before and after LASIK. Two eyes in the RK group required quick repositioning of the flap due to irregular opposition to the stromal bed. Although the number of eyes studied is limited, LASIK treatment for residual myopia after RK or PRK appears safe, effective, and stable.
REFERENCES
1)Ionniis G Pallikaris, T.G Papadaski, From Keratomileusis to LASIK – Evaluation of lamellar corneal procedures , Refractive Surgery, ,Jaypee, 210-215
2)Steven C, Shallorn, P.J. Mcdonnell, Refractive SurgeryPast ,present and future, Cornea, Mosby, 1997-2006
3)Howard Gimbel,E.E.A. Penno, LASIK the technique , Refractive Surgery, Jaypee 254-265
4)L.E.Probst ,T Woolfson ,M.Knitzinger , Predictive formulas for LASIK , Refractive Surgery,Jaypee, 218-228
5)Dimitri T. Azar, M.D. Suhas Tuli, M.D., Robert Alan Benson, et al. Photorefractive Keratectomy for residual myopia after radial keratotomy. J Cat Refract Surgvol 24,MARCH 1998, 303 –311.
6)William J Jory , Predictability of radial keratotomy after excimer laser photorefractive keratectomy, J Cat Refract Surg ,vol. 24, March 1998, 312-314
7)Marwin l Kwitko, S Jovker, Hua Yan , M. Atas, Radial keratotomy for residual myopia after photorefractive keratectomy, J Cat Refract Surg ,vol. 24, March 1998, 315319
LASIK AFTER RK AND PRK
8)Mihai Pop, Prompt retreatment after photorefractive keratectomy, J Cat Refract Surg ,vol. 24, March 1998,320330
9)Anita Panda, Gopal Das, M Vasanthi, Abhisan kumar, Corneal infection after radial keratotomy; J Cataract Refract Surg vol. 24, March 1998, 331-334.
10)Garthy D S,Larki DF, Hill AR and Ficker LA et al, Retreatment for significant regression after excimer laser photorefractive keratectomy , prospective ,randomized, masked trial, Ophthalmology, 1998, Jan, 105:1, 131-41
11)Rozsival P, Feyurmannova A, Retreatment after photorefractive keratectomy for low myopia, Ophthalmology, 1998, Jul,105:7, 1189-92
12)Ghaith AA, Daniel J, Stulting RD, and Thompson KP et al, Contrast sensitivity and glare disability after radial keratotomy and photorefractive keratectomy, Arch Ophthalmol, 1998 Jan,116:1, 12-8
13)Ozdamar A, Sener B, Aras C, Aktunc R, Laser in situ keratomileusis for myopic regression, J Cat Refract Surg, 1998 Sep, 24:9 ,1208-11
14)Kolahdouz Isfahani AH, WuFM, Salz JJ, Refractive keratotomy after photorefractive keratectomy, J Refract Surg 1999 Jan,15:1 ,53-7
15)Probst LE, Machat JJ , Conservative photorefractive keratectomy for residual myopia after radial keratotomy, Can J Ophthalmol, 1998 Feb, 33 :1 ,20-7
16)Allo Jl, Artola a, Claramonte PJ, Ayala MJ, Snachez SP, Complications of photorefractive keratectomy for myopia :two year follow-up of 3000 cases
17)Hersh PS , S. F Brint, R.K Mololeyand D.D Durrie et al; Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia; Ophthalmology, 1998 Aug, 105:8,1512-22
18)Jorge Alio, A Artola, P Claramonte and N J Ayala et al, PRK for pediatric myopic anisometropia , J. Cat Refract Surg, vol-24, no-3, March 1998, 327-330
Contents
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Section 7
Subjects Index
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Sunita Agarwal, M.S.
Dr. Agarwal’s Eye Hospital, 13 Cathedral Road, Chennai (Madras)- 600 086, India
Tel: + 91 44 8113704 -- Fax: + 91 44 8115871 E-mail: agarwal@giasmd01.vsnl.net.in
LASIK AND BEYOND LASIK 205
LASIK AFTER PENETRATING KERATOPLASTY
Chapter 17
LASIK AFTER PENETRATING
KERATOPLASTY
Umberto Benelli, MD and Marco Nardi, MD
Introduction
Visual recovery after penetrating keratoplasty is often adversely affected by residual refractive errors, despite a clear graft. Residual myopia and regular and irregular astigmatism account for most of the decreased visual acuity. A large amount of corneal astigmatism can greatly influence the visual outcome of an otherwise successful corneal transplant. The mean amount of astigmatism reported after penetrating keratoplasty averages 4.00 to 6.00 diopters (D) in different series, but it can range from 0 to 20.00 D or more. Most patients are not able to tolerate more than 3 D of anisometropia because of image size disparity, or astigmatism of greater than 1.5 to 3 D (Olson et al., 2000).
To treat these conditions, it should initially consider clinical visual rehabilitation. Some patients can be corrected with spectacles but many others must use contact lenses (Applegate and Howland, 1993).
Contact lenses are vital to the rehabilitation of the post-keratoplasty patient. Ten percent to 30% of patients who had penetrating keratoplasty wear contact lenses for visual rehabilitation. The incidence of contact lens wear after penetrating keratoplasty for keratoconus is 25% to 50%.
Both soft and gas permeable contact lenses are extremely effective and remain the primary technique of visual rehabilitation for patients who cannot tolerate spectacles. Wearing contact lenses after penetrating keratoplasty could not be ideal, especially when a patient had surgery because of intolerance to contact lenses, as occurs with keratoconus. Even when a patient is successfully fitted with contact
lenses, the lenses may irritate the donor cornea because of peripheral touch and in some instances, peripheral neovascularization occurs with risk of corneal rejection. If the patient is unable to wear spectacles or contact lenses, surgical treatment should be considered (Genvert et al., 1985; Lim et al., 2000). Additional modalities to correct myopia and astigmatism after penetrating keratoplasty, especially in the first period after corneal transplantation (plastic phase), may be suture adjustment, selective suture removal or compression sutures (Binder, 1985; Mandel et al., 1987; Limberg et al., 1989; McNeill and Wessels, 1989; Karabatsas et al., 1998). The stability and predictability of these procedures are not ideal and there is a risk of damaging the transplanted cornea. Frequently, if acceptable astigmatism is achieved, sutures are left in place for 1 or more years. However, breakage often results, requiring suture removal. Additionally, there may be suture-related complications including inflammation, infection, vascularization, epithelial erosion, and ulceration. Radial keratotomy and transverse keratotomies can be effective in the treatment of astigmatism following penetrating keratoplasty but treatment does not effectively treat the remaining spherical equivalent ametropia because of the coupling phenomenon (Risko and Antonios, 1993).
The use of excimer laser has provided the opportunity to develop new refractive surgical procedures. Although recent reports suggest that photorefractive keratectomy (PRK) is relatively safe and effective in reducing refractive error after penetrating keratoplasty, it still has limits (Campos et al., 1992). PRK for myopia after penetrating keratoplasty is associated with increased incidence
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LASIK AND BEYOND LASIK 207
Chapter 17 
Figure 17-1. Biomicroscopy examination of cornea before LASIK and 2 hours after.
of irregular astigmatism, corneal scarring, and significant regression. In addition, some cases of transplant rejection after PRK have been described (Hersh et al., 1993; Epstein and Robin, 1994; Bilgihan et al., 2000).
In 1991, Pallikaris et al. proposed the corneal flap technique for laser in situ keratomileusis (LASIK) as an alternative to PRK. LASIK has become increasingly popular over the past several years in treating myopia, astigmatism, and, more recently, hyperopia (Salchow et al., 1998; Zadok et al., 2000).
Enthusiasm for this procedure has been tempered by the potential for complications, particularly during the preparation of the corneal flap (superficial keratectomy) (Stulting et al., 1999; Holland et al., 2000). There are different authors who use LASIK after penetrating keratoplasty to correct residual visual defects. In the majority of cases the LASIK procedure resulted in an excellent visual
outcome with no significant post-operative complications (Figure 17-1).
Eligible Patients
The use of LASIK after corneal transplantation as an enhancement or secondary operation markedly improves the optical results of corneal transplantation. The disease present before penetrating keratoplasty made no difference in the refractive results.
It is important to advocate a conservative approach to treating refractive errors after penetrating keratoplasty. Contact lens remain the standard of care and are to be encouraged whenever feasible. When contact lens use is not possible, it is a good idea to suggest slightly undercorrection. The ideal patient must be all spectacle and contact lenses correction intolerant and the astigmatism must be regular.
After penetrating keratoplasty, many patients will have irregular or high astigmatism that may predispose them to flap complications during the keratectomy. This would be especially true in steep postoperative corneas where there is a large difference between the flat and steep axis. These patients, although not amenable to spectacle correction, can be rehabilitated with a gas-permeable contact lens. It is important to discourage these patients from having LASIK if they are at all tolerant of contact lenses (Parisi et al., 1997).
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Subjects Index
Time of Surgery
There are several alterations of normal |
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LASIK technique when treating myopia or astigma- |
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tism or both after penetrating keratoplasty. An accu- |
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rate assessment of the patient’s true refraction de- |
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pends on the donor cornea returning to its normal |
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shape after suture removal. With gas-permeable con- |
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tact lens wear, most LASIK surgeons recommend a |
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minimum of 1 month to allow resolution of corneal |
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warpage, and with long-term gas-permeable contact |
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lens wear, the corneal warpage may take several |
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months to abate (Lam et al., 1998). |
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In our opinion minimum time for LASIK |
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after suture removal is 12 months and minimum time |
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208 SECTION III
for LASIK after penetrating keratoplasty is 1 year. Although there are reports of LASIK being performed as early as 12 months following penetrating keratoplasty without complications, the minimum or ideal time interval between the initial penetrating keratoplasty to LASIK treatment is not yet established. It seems very important to evaluate the strength of the scar at the graft-host junction and the stability of refraction after keratoplasty and/or suture removal (Lam et al., 1998).
Other less quantifiable factors, such as initial corneal pathology and the duration of topical corticosteroid application, may also affect graft-host junction strength. Younger patients may heal faster and might be eligible for earlier treatment with LASIK.
Surgical Technique
The LASIK procedure used by the majority of the surgeons is the standard technique. There are small differences between different authors due to different microkeratome models and/or different LASIK personal techniques.
Some authors suggested that the LASIK flap must be cut first and then laid back down to allow the eye to settle and the residual refractive error and astigmatism to adjust. Once the eye is stable, after several days to a week, the refractive error is reassessed and then the corrective LASIK ablation is performed (Vajpayee and Dada, 2000).
It has been observed that the lamellar cut of the microkeratome and the creation of a 160/180 micron depth flap, leads to a modification of the axis and the magnitude of the cylinder, which may be significant, especially in eyes with a high astigmatic error.
The cylindrical error after a corneal grafting procedure may be caused by irregular contractile forces emanating from the host-graft junction and inducing a toric contracture of the cornea. The large lamellar cut performed by the microkeratome may lead to a release of these contractile forces and subsequent realignment of the corneal tissues. Therefore, the creation of a lamellar corneal flap may be associated with a significant change in the magnitude and the axis of the astigmatism. For this reason performing laser ablation on the basis of the preop-
LASIK AFTER PENETRATING KERATOPLASTY
erative refractive error may not be a good option, because the original cylinder may have undergone significant modification after the creation of a lamellar corneal flap. In addition, in some patients there may be a continued shift in the keratometry, up to a period of 8 to 12 weeks after cutting the flap. For this reason some authors think that LASIK after penetrating keratoplasty should be done as a two-stage procedure. The first stage involves the use of the microkeratome to perform the lamellar corneal cut, without any laser ablation. The change in the corneal topography, keratometry, and the refraction should be noted on the subsequent day and monitored on a weekly basis. The flap can then be relifted after an interval of 4 to 6 weeks or after the refraction is stable over a 2-week period. The excimer laser ablation is performed at this stage on the basis of the current refractive status. This two-stage procedure yields better visual results and is recommended in all eyes that undergo LASIK for the correction of significant residual astigmatism after penetrating keratoplasty (Vajpayee and Dada, 2000).
Although this technique may improve results, it also requires two procedures each with potential complications including graft rejection. The lamellar flap heals more aggressively over the corneal graft/host interface, which can result in difficulty elevating flap during enhancements. The edge of the lamellar flap may not oppose the stromal bed perfectly in LASIK after penetrating keratoplasty: this increase the possibility of epithelial ingrowth, which is known to occur more commonly after all enhancement procedures. In addition any surgical manipulation of the eye results in an increased incidence of allograft rejection.
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Subjects Index
Post-Surgical Treatment
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It is important to be more liberal with the use of postoperative corticosteroids than in normal LASIK patients. Usually, after conventional LASIK surgery, patients are treated with fluorometholone 0.1% four times daily for 5-7 days. In LASIK after penetrating keratoplasty, it is better to use prednisolone acetate 1% four times daily for 10 days and then prednisolone acetate 1% once daily for 2-4 weeks. This additional use of corticosteroids is indicated because of the potential risk of graft rejection after
LASIK AND BEYOND LASIK 209
Chapter 17 
any surgical procedure on a penetrating keratoplasty (Donnefeld et al., 1999).
Risks and Possible Complications
Endothelial alterations after LASIK have been studied. Pallikaris and Siganos (1994) believe that the presence of endothelial loss of up to 4.11%, related to the quantity of the desired correction, is probably caused by the shock waves produced by the excimer laser photoablation and corneal manipulation during keratomileusis. Other studies, however, have demonstrated no significant endothelial alterations after LASIK following penetrating keratoplasty (Holland et al., 2000).
Another major concern in performing LASIK after penetrating keratoplasty is the risk of damage to the corneal transplant or the graft-host- wound interface, or both. Wound dehiscence after penetrating keratoplasty is a well-described case of extrusion of the intraocular contents.
During LASIK surgery after keratoplasty, it is important to minimize the suction time. In LASIK, intraocular pressure is elevated to more than 65 mm Hg and there is a risk of wound dehiscence with the possibility event that could potentially reduce best spectacle-corrected visual acuity, regardless of whether vision actually was lost because of this event.
The substantial decrease of corneal thickness after surgery is similar to that obtained in studies of LASIK for the correction of myopia and myopic astigmatism with no prior surgery.
The more frequent problems are undercorrection and decentered ablation. Difficulties in accurately measuring refractive cylinder due to irregular astigmatism and decreased best spectaclecorrected visual acuity as well as the long-term instability of penetrating keratoplasty wounds, continue to be major obstacles to improve results.
Results
LASIK treatment after keratoplasty is a recent method to correct residual myopia and astigmatism. (Figures 17-2, 17-3 and 17-4) show the modification of computerized corneal maps after
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Subjects Index
Figure 17-2 (a-b). Computerized corneal map before (a) and 10 days after LASIK to correct astigmatism and high myopia.
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post-keratoplasty LASIK. In literature there are few reports that show the results obtained by different authors.
Rashad (2000) performed LASIK on 19 eyes with high astigmatism after penetrating keratoplasty, using the Chiron Automated Corneal Shaper and the Chiron-Technolas Keracor 116 excimer laser. The amount of preoperative refractive astigmatism ranged from 6.50 to 14.50 D (mean, 9.21 ± 1.95 D) and the spherical component of manifest refraction ranged
210 SECTION III
LASIK AFTER PENETRATING KERATOPLASTY
Figure 17-3 (a-b). Computerized corneal map before (a) and 14 days after LASIK to correct regular astigmatism. Residual astigmatism is still detectable.
from -7.00 to +1.25 D (mean, -2.14 ± 2.11 D). At 1 year after 91SECTION 1Chapter 10LASIK, the amount of refractive astigmatism was reduced to a mean of 1.09 ± 0.33 D (range, 0.50 to 1.75 D), with 57.9% of the eyes within ±1.00 D of refractive astigmatism. The mean percent reduction of astigmatism was 87.9 ± 3.7%. The postoperative spherical component of manifest refraction ranged from -1.00 to +1.75 D with a mean of +0.43 ± 0.82 D. There were no intraoperative complications. Spectacle-corrected
Figure 17-4 (a-b). Computerized corneal map before (a) and 12 days after LASIK to treat irregular astigmatism.
visual acuity was not reduced in any eye, and improved by 2 or more lines in 42.1% of eyes after LASIK.
Forseto et al. (1999) reported the results of LASIK after penetrating keratoplasty in 22 eyes. They used the VISX Twenty-Twenty excimer laser, which utilizes a constricting slit to achieve an elliptical ablation profile. Mean preoperative astigmatism was 4.24 ± 2.28 D (range, 0 to 9.00 D), and mean postoperative astigmatism was 1.79 ± 1.12 D (range,
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LASIK AND BEYOND LASIK 211
Chapter 17 
0 to 5.50 D). The mean percent reduction of astigmatism was 57.7% and the mean percent correction of astigmatism was 54.0%.
Arenas and Maglione (1997) showed the results of LASIK in 4 eyes with myopia and astigmatism after penetrating keratoplasty using the Keracor 116 excimer laser. They reported that LASIK was effective in reducing myopia but astigmatism changed from a mean -2.87 D preoperatively (range, -1.00 to -5.00 D) to a mean -3.50 D after LASIK (range, -1.00 to -5.00 D). The ablation zone used in their study for the correction of astigmatism was probably too small (only 3.5 mm), which accounts for the limited change in amount of astigmatism after LASIK. An ablation zone of 5.0-5.5 mm for astigmatic correction seems to be better, yielding better results in terms of astigmatism correction.
Donnenfeld et al. (1999) reported 3-month results of LASIK in 22 eyes with myopia and astigmatism after penetrating keratoplasty using the VISX Star excimer laser. Mean refractive cylinder before surgery was 3.64 ± 1.72 D. One eye had 8.50 D of astigmatism and 21 eyes had less than 6.00 D of astigmatism. The amount of astigmatism was reduced to a mean of 1.64 ± 1.14 D at 3 months after LASIK. There was undercorrection of astigmatism in many eyes. Nine eyes (40.9%) had refractive astigmatism of less than 1.00 D and 18 eyes (81.8%) had refractive astigmatism of less than 2.00 D. LASIK retreatment was performed on 2 eyes for correction of residual astigmatism at 3 months after the primary LASIK procedure,
Koay et al. (2000) performed LASIK on 8 eyes after a mean 71 months following the initial penetrating keratoplasty. No eyes lost any Snellen lines of best spectacle-corrected visual acuity at the latest follow-up (12 months). Mean reduction in spherical equivalent refraction was 91% from -6.79 ± 4.17 D to -0.64 ± 1.92 D and mean reduction of cylinder was 72% from -6.79 ± 3.28 D to -1.93
± 1.17 D.
Nassaralla and Nassaralla (2000) treated 8 eyes with the Chiron Technolas 217 excimer laser and the Automated Corneal Shaper microkeratome. Mean spherical equivalent refraction decreased from -4.50 D (range, -3.00 to -7.25 D) to -0.75 D (range, - 1.50 to +0.50 D) and the mean pre-operative astigmatism decreased from 3.50 D (range, 1.50 to 5.00
D) to 1.25 D (range, 0.75 to 2.00 D). Uncorrected |
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visual acuity improved by at least two Snellen lines |
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in all eyes. Best spectacle-corrected visual acuity did |
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not change in four eyes (50%) and improved in three |
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eyes (37.5%). |
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Webber et al. (1999) reported the results of |
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a series of 26 eyes treated with LASIK to correct |
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post penetrating keratoplasty ametropia; 14 eyes also |
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received arcuate cuts in the stromal bed at the time |
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of surgery. The mean preoperative spherical equiva- |
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lent was -5.20 D and the mean preoperative astig- |
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matism was 8.67 D. The final follow up results for |
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these eyes were -1.91 D and 2.92 D for spherical |
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equivalent and astigmatism. The patients undergo- |
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ing arcuate cuts were less myopic but had greater |
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astigmatism than those not. One eye suffered a sur- |
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gical complication. No eyes lost more than one line |
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of BSCVA and all eyes gained between 0 and 6 lines |
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UCVA. |
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Changes in refractive astigmatism in the |
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majority of the studies showed stability of refraction |
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at 3 months after LASIK or LASIK retreatment. |
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Changes in refractive astigmatism between 6 and 12 |
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months were minimal and statistically insignificant. |
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No change was at this moment observed on trans- |
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parency of the grafts after LASIK. Haze was not |
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observed in any patient. No corneal graft rejection |
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episode was noted. |
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Conclusions
The primary goal of LASIK after penetrating keratoplasty is to reduce the refractive error to allow spectacle correction. The uncorrected visual acuity remains a secondary goal with LASIK after penetrating keratoplasty, whereas uncorrected visual acuity is clearly the primary objective of cosmetic LASIK. For this reason, return to binocularity and optimized best corrected visual acuity with spectacles is the true endpoint for success with LASIK after penetrating keratoplasty.
A potential advantage of LASIK over surface excimer laser photoablation is that there is better corneal sensation after LASIK than after PRK. In LASIK, the 2 to 3 clock-hours of hinge nasally allows the passage of corneal nerves into the central cornea. This has been shown to provide improved sensation. One of the main predictors of graft sur-
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212 SECTION III
vivability is corneal sensation. There is always a diminution of corneal sensation after penetrating keratoplasty due to trephination of the corneal nerves. LASIK offers an additional advantage over PRK in that there is less loss of corneal sensation (Donnenfeld et al., 1999).
Because of the results obtained by different surgeons, it results that LASIK is a good alternative to treat high amounts of myopia and/or astigmatism after penetrating keratoplasty. LASIK is predictable and produces rapid recovery of visual acuity not possible with any previously described method.
Based on studies of corneal wound healing after penetrating keratoplasty, this type of surgery should be delayed at least 12 months after keratoplasty because of the risk of corneal dehiscence from the high pressure (60 mm Hg) applied to place the suction ring of the microkeratome.
The topographic results in the majority of the patients show some changes in the postoperative patterns, with good tendency to correct astigmatism and myopia. LASIK preserves the donor Bowman’s membrane, facilitates good wound healing, and excellent visual recovery.
After penetrating keratoplasty, many patients will have irregular astigmatism, which, although not amenable to spectacle correction, can be rehabilitated with a gas-permeable contact lens. These patients must be discouraged if they are at all contact lenstolerant from having LASIK performed, as the excimer laser currently is not successful in treating irregular astigmatism. Although laser technology is excellent for regular astigmatism and myopia, it cannot currently treat irregular astigmatism. The development of flying spot excimer lasers guided by corneal topography will successfully treat some forms of irregular astigmatism in the next several years (Tamayo Fernandez and Serrano, 2000). This will allow even more accurate treatment of post-penetrat- ing keratoplasty refractive errors.
LASIK AFTER PENETRATING KERATOPLASTY
References
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-Arenas A, Maglione A. Laser in situ keratomileusis for astigmatism and myopia after penetrating keratoplasty. J Refract Surg 1997; 13: 27-32.
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-Binder PS. Selective suture removal can reduce post-keratoplasty astigmatism. Ophthalmology 1985; 92: 1412-1416.
-Campos M, Hertzog L, Garbus J, Lee M, McDonnell PJ. Photorefractive keratectomy for severe post-keratoplasty astigmatism. Am J Ophthalmol 1992; 114: 429-436.
-Donnenfeld ED, Kornstein HS, Amin A, Speaker MD, Seedor JA, Sforza PD, Landrio LM, Perry HD. Laser in situ keratomileusis for correction of myopia and astigmatism after penetrating keratoplasty. Ophthalmology 1999; 106: 1966-1975.
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-Holland SP, Srivannaboon S, Reinstein DZ. Avoiding serious corneal complications of laser assisted in situ keratomileusis and photorefractive keratectomy. Ophthalmology 2000; 107: 640-652.
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LASIK AND BEYOND LASIK 213
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- Karabatsas CH, Cook SD, Figueiredo FC, Diamond JP, Easty DL. Surgical control of late post-kerato- plasty astigmatism with or without the use of computerized videokeratography. Ophthalmology 1998; 105: 19992006.
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Limberg MB, Dingeldein SA, Green MT, Klyce |
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Salchow DJ, Zirm ME, Stieldorf C, Parisi A. |
SD, Insler MS, Kaufman HE. Corneal compression su- |
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tures for the reduction of astigmatism after penetrating |
matism. J Cataract Refract Surg 1998; 24: 175-182. |
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keratoplasty. Am J Ophthalmol 1989; 108: 36-42. |
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Stulting RD, Carr JD, Thompson KP, Waring III |
-Mandel MR, Shapiro MB, Krachmer JH. RelaxGO, Wiley WM, Walker JD. Complications of laser in
ing incisions with augmentation sutures for the correction of post-keratoplasty astigmatism. Am J Ophthalmol 1987; 103: 441-447.
-McNeill JI, Wessels JF. Adjustment of single continuous suture to control astigmatism after penetrating keratoplasty. J Refract Corneal Surg 1989; 5: 216-223.
-Nassaralla BRA, Nassaralla JJ. Laser in situ keratomileusis after penetrating keratoplasty. J Refract Surg 2000; 16: 431-437.
-Olson RJ, Pingree M, Ridges R, Lundergan ML, Alldredge C Jr, Clinch TE. Penetrating keratoplasty for keratoconus: a long-term review of results and complications. J Cataract Refract Surg 2000; 26: 987-991.
-Pallikaris IG, Papatzanaki ME, Siganos DS, Tsilimbaris MK. A corneal flap technique for laser in situ keratomileusis. Human studies. Arch Ophthalmol 1991; 109: 1699-1702.
-Pallikaris IG, Siganos DS. Excimer laser in situ keratomileusis and photorefractive keratectomy for correction of high myopia. J Refract Corneal Surg 1994; 10: 498-510.
situ keratomileusis for the correction of myopia. Ophthalmology 1999; 106: 13-20.
-Tamayo Fernandez GE, Serrano MG. Early clinical experience using custom excimer laser ablations to treat irregular astigmatism. J Cataract Refract Surg 2000; 26: 1442-1450.
-Vajpayee RB, Dada T. Lasik after penetrating keratoplasty (Letter). Ophthalmology 2000; 107: 18011802.
-Zadok D, Maskaleris G, Montes M, Shah S, Garcia V, Chayet A. Hyperopic laser in situ keratomileusis with the Nidek EC-5000 excimer laser. Ophthalmology 2000; 107: 1132-1137.
-Webber SK, Lawless MA, Sutton GL, Rogers CM. LASIK for post penetrating keratoplasty astigmatism and myopia. Br J Ophthalmol 1999; 83: 1013-1018.
Umberto Benelli, MD
Department of Neurosciences
Section of Ophthalmology
University of Pisa
Via Roma, 67 56126 Pisa - Italy
E-Mail: oculista@tin.it
Contents
Section 1
Section 2
Section 3
Section 4
Section 5
Section 6
Section 7
Subjects Index
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214 SECTION III
LASIK AFTER PREVIOUS CORNEAL SURGERY
Chapter 18
LASIK AFTER PREVIOUS CORNEAL SURGERY
Jorge L. Alió, MD, PhD, Walid H. Attia MD, Javier Gómez, MD
Laser-assisted in situ keratomileusis (LASIK) is gaining acceptance as a versatile refractive surgical procedure. LASIK is gaining popularity due to quick visual rehabilitation, minimal postoperative discomfort, and the ability to correct variable forms and high degrees of refractive errors with minimal postoperative complications. LASIK efficacy has been reported in several studies for the correction of primary refractive errors such as myopia, hyperopia, and astigmatism. However, there have been very few studies reporting the use of LASIK in treating patients with residual refractive errors following other corneal or nonrefractive refractive procedures. LASIK is an evolving surgical technique with both therapeutic and refractive indications, especially in cases where refractive defects or irregular astigmatism have been induced by previous refractive surgery, trauma, or penetrating keratoplasty. This chapter is dedicated to study the use of LASIK in treating the following residual refractive problems after different corneal surgical procedures:
1.Radial keratotomy (RK)
2.Astigmatic keratotomy (AK)
3.Photorefractive keratectomy (PRK)
4.Laser thermokeratoplasty (LTK)
5.Penetrating keratoplasty (PKP)
6.Automated lamellar keratoplasty (ALK)
7.Epikeratophakia
8.Corneal trauma
General Considerations After RK
RK was a widely used surgical technique to correct myopia. lt flattens the central cornea indirectly through peripheral radial incisions, however the amount of central flattening that can be achieved is limited. 1,2 The most common side effect of this procedure is overcorrection or undercorrection. Waring et al in 1994 reported the result of a multicenter prospective evaluation of an RK study in which 43% of patients had a hyperopic shift of 1 diopter (D) or more by 10 years after treatment.3 Treatment of hyperopia after RK has heen a complicated problem. To avoid this problem, most radial keratotomy surgeons prefer to perform conservative initial surgery as a safeguard against the development of hyperopic shift, with intentionally undercorrected postoperative results, thus increasing the incidence of patients with significant undercorrection. Eventually, this group will need additional treatment. Myopic regression is a common finding following RK and is more evident in young patients; again this group of patients will need additional treatment.
Contents
Section 1
Section 2
Section 3
Section 4
Section 5
Section 6
Section 7
Subjects Index
Help ?
Residual Myopia After RK
Unexpected or intentional residual myopia after RK may be due to a large optical zone, few incisions, or shallow incisions. Each patient’s cor-
LASIK AND BEYOND LASIK 215