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ORIGINAL ARTICLE
Year : 2007  |  Volume : 14  |  Issue : 2  |  Page : 54-57 Table of Contents     

Two-stage LASIK for correction of refractive errors after penetrating keratoplasty


Anterior Segment Division, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia

Date of Web Publication11-Nov-2009

Correspondence Address:
Abdul-Elah Al-Towerki
King Khaled Eye Specialist Hospital, PO Box 7191, Riyadh 11462
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


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   Abstract 

Purpose. To evaluate the efficiency of two-stage laser-assisted in situ keratomileusis (LASIK) for correction of spherical anisometropia and high astigmatism after penetrating keratoplasty (PKP).
Patients and Methods.
Retrospective analysis of 8 eyes from 8 patients who underwent two-stage LASIK after PKP for keratoconus.
Results.
After flap creation, there was a mean spherical shift of 2.32 diopters (D) (P < .01) and a mean astigmatic shift of 2.19 D (P < .01). After excimer laser treatment, there was a mean spherical shift of 2.41 D (P < .01) and a mean astigmatic shift of 3.97 D (P < .01). The spherical equivalent after the two-stage treatment was within 1 D of emmetropia in 7 eyes (87.5%). No patient experienced a reduction of best spectacle-corrected visual acuity (BSCVA) or uncorrected visual acuity (UCVA) after corneal flap creation or excimer laser treatment. The UCVA was 20/40 or better in 7 eyes (97.5%) and 20/30 or better in 5 eyes (62.5%), 6 months after completion of treatment.
Conclusion.
LASIK is effective in reducing spherical anisometropia and high astigmatism after PKP. Because of a statistically significant change in refractive error after creation of the LASIK flap, it is recommended that the procedure be performed in 2 stages.

Keywords: astigmatism, penetrating keratoplasty, LASIK, myopia, two-stage procedure


How to cite this article:
Al-Towerki AE. Two-stage LASIK for correction of refractive errors after penetrating keratoplasty. Middle East Afr J Ophthalmol 2007;14:54-7

How to cite this URL:
Al-Towerki AE. Two-stage LASIK for correction of refractive errors after penetrating keratoplasty. Middle East Afr J Ophthalmol [serial online] 2007 [cited 2019 Sep 19];14:54-7. Available from: http://www.meajo.org/text.asp?2007/14/2/54/57695

Over the past 20 years, many advances have been made in the surgical aspects of penetrating keratoplasty (PKP), donor tissue preservation, and prevention and treatment of graft rejection. However, management of postoperative refractive errors continues to be one of the most challenging problems facing cornea surgeons. In many cases, spherical anisometropia and high astigmatism limit visual rehabilitation. Although the use of rigid gas-permeable contact lenses is often effective, this option is limited in our patient population because of cost, inconvenience, and environmental factors. Surgical procedures, such as relaxing incisions and photorefractive keratectomy, have produced inconsistent results.

High astigmatic error following penetrating keratoplasty is usually caused by irregular scarring and asymmetric contractile forces emanating from the host-graft junction. The creation of a lamellar corneal flap with a microkeratome results in a circumferential release of these contractile forces with a resultant reduction in the surgically induced astigmatism. [1] Because a shift in spherical and astigmatic error frequently occurs following the creation of a flap using laser-assisted in situ keratomileusis (LASIK), it is probably preferable to wait until the refractive error has stabilized before treating residual refractive errors with excimer laser ablation. The present study was conducted to evaluate refractive changes after the creation of a LASIK flap, as well as the refractive accuracy and visual outcome of subsequent excimer laser ablation.


   Patients and Methods Top


To evaluate the refractive and visual results of two-stage LASIK, 8 eyes of 8 patients (6 males, 2 females) who had undergone PKP for keratoconus were included in a nonmasked, noncontrolled, prospective clinical trial. Patients' ages ranged from 20 to 29 years. Patients presented between January 2000 and January 2002 with spherical anisometropia greater than 5.0 D and high astigmatism (> 4 D). In all cases, at least 2 years (range, 24-36 months) had passed since PKP and at least 6 months (range, 6-11 months) since complete suture removal. All patients had failed to tolerate contact lenses of any type and were, therefore, functioning monocularly with the fellow eye.

After informed consent was obtained, a hinged LASIK flap procedure was performed on each patient by the same surgeon, using a Carriazo-Barraquer microkeratome (Moria, Paris, France). Repositioning of the flap to the underlying corneal tissue was easily achieved in all eyes. Postoperatively, topical Maxitrol drops were administered 4 times daily for 5 days, after which treatment was switched to topical FML drops 4 times daily and tapered gradually over a 6-week period.

Prior to excimer laser ablation, a comprehensive ophthalmic examination was performed including best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), manifest and cycloplegic refraction, corneal topography (EyeSys, Houston, TX, USA), pachymetry, slit-lamp examination, and funduscopic examination.

When stabilization of the corneal shape was demonstrated by analysis of corneal topography (difference in keratometric power of less than 1 D and no change in astigmatic pattern on 2 consecutive visits at least 3 weeks apart), the second stage of the procedure followed. The excimer laser treatment was performed 2 to 3 months after flap creation in all cases. Excimer laser ablation was performed using a NIDEK EC-5000 laser. Correction of the myopic component of the refractive error was performed with a 6.0-mm optical zone and a 7.5-mm transition zone. Correction of hyperopic refractive error was done with an optical-zone diameter of 5.5 to 9.0 mm. For astigmatic correction, cross-cylinder type ablation was used, splitting the treatment into 2 parts for the myopic and hyperopic halves, respectively.

Postoperatively, topical Maxitrol drops were administered 4 times daily for 5 days, after which treatment was switched to topical FML drops 4 times daily and tapered gradually over a 6-week period. Similarly to what was done after creation of the flap, a standard eye examination, including slit-lamp microscopy, uncorrected and best spectacle-corrected visual acuity, refraction, analysis of corneal topography (EyeSys), and slit lamp biomicroscopy, was performed in each patient at 1 month, 3 months, and 6 months after excimer laser treatment. All corneal grafts remained clear during the entire postoperative follow-up period.


   Results Top


The refractive data recorded for each treated eye are shown in [Table 1]. After flap creation, there was a mean spherical shift of 2.32 diopters (D) (P < .01) and a mean astigmatic shift of 2.19 D (P < .01). After excimer laser treatment, there was a mean spherical shift of 2.41 D (P < .01) and a mean astigmatic shift of 3.97 D (P < .01). The spherical equivalent after excimer laser treatment was within 1 D of emmetropia in 7 eyes (87.5%).

[Table 2] shows the UCVA and BSCVA values before and after both flap creation and excimer laser treatment. No patient experienced a reduction of BSCVA or UCVA after corneal flap creation or excimer laser treatment. The UCVA was 20/40 or better in 7 eyes (87.5%) and 20/25 or better in 4 eyes (50.0%), 6 months after completion of treatment.

[Figure 1] shows topographic changes observed in a 27-year-old male patient (case 2) who presented with a BSCVA of 20/40 with a refraction of +3.50 -7.50 X 100. After corneal flap creation, his BSCVA improved to 20/25 with a refraction of +0.75 -6.00 X 10. After excimer laser treatment, his BSCVA improved to 20/20 with a refraction of +1.75, and his UCVA was 20/25. After 43 months, his UCVA was 20/20, and his refraction had changed to plano -1.25 X 80.

[Figure 2] shows changes observed in a 22-year-old female patient (case 5), who presented with a BSCVA of 20/40 with a refraction of +2.50 -7.50 X 90. After corneal flap creation, her BSCVA improved to 20/20 with a refraction of plano -8.00 X 75. After excimer laser treatment, her BSCVA remained 20/20, but the refraction improved to +0.50 -1.00 X 125. Her UCVA was 20/25.


   Discussion Top


Spherical anisometropia and high astigmatism are relatively frequent postoperative complications of PKP. The excimer laser has been used for some time in the treatment of refractive error after PKP. [2],[3],[4],[5],[6],[7],[8],[9] However, the results of photorefractive keratectomy have not always been satisfactory because of the development of haze in many cases. Results of LASIK have been variable and compromised by the use of one-stage procedures, where refractive correction is performed before shifts attributed to the creation of the flap have been properly measured.

Massimo et al [8] demonstrated significant changes in refractive data after flap creation, a finding that was confirmed by the present study, in which there was a statistically significant myopic and astigmatic shift after flap creation. In the previous study that investigated two-stage LASIK, [8] a UCVA of 20/40 or better was obtained in 72.7% of cases, compared with 87.5% in the present study. In addition, 50% of the eyes in the present study attained a UCVA of 20/25 or better, and no eyes lost any lines of BSCVA.

In conclusion, LASIK is effective in reducing myopia and astigmatism after PKP. Because of a statistically significant change in refractive error after creation of the LASIK flap, it is recommended that the procedure be performed in 2 stages.[10]

 
   References Top

1.Dada T, Vajpayee RB, Gupta V, et al. Microkeratome-induced reduction of astigmatism after penetrating keratoplasty. Am J Ophthalmol 2001;131:507-508.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]  
2.Lindstrom RL. Surgical correction of refractive errors after penetrating keratoplasty. Int Ophthalmol Clin 1994;34(4):35-53.  Back to cited text no. 2      
3.Malecha MA, Holland EJ. Correction of myopia and astigmatism after penetrating keratoplasty with laser in situ keratomileusis. Cornea 2002;21:564-569.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]  
4.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 1974-1975.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]  
5.Forseto AS, Francesconi CM, Nose RA, Nose W. Laser in situ keratomileusis to correct refractive errors after keratoplasty. J Cataract Refract Surg 1999;25:479-485.  Back to cited text no. 5      
6.Webber SK, Lawless MA, Sutton GL, Rogers CM. LASIK for post penetrating keratoplasty astigmatism and myopia. Br J Ophthalmol 1999;83:1013-1018.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]  
7.Rashad KM. Laser in situ keratomileusis for correction of high astigmatism after penetrating keratoplasty. J Refract Surg 2000;16:701-710.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]  
8.Busin M, Zambianchi L, Garzione F, et al. Two-stage laser in situ keratomileusis to correct refractive errors after penetrating keratoplasty. J Refract Surg 2003;19:301-308.  Back to cited text no. 8  [PUBMED]  [FULLTEXT]  
9.Kwitko S, Marinho DR, Rymer S, Ramos Filho S. Laser in situ keratomileusis after penetrating keratoplasty. J Cataract Refract Surg 2001;27:374-379.  Back to cited text no. 9  [PUBMED]  [FULLTEXT]  
10.Dada T, Vajpayee RB. Laser in situ keratomileusis after PKP [letter]. J Cataract Refract Surg 2002;28:7-8.  Back to cited text no. 10  [PUBMED]  [FULLTEXT]  


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]



 

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