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Middle East African Journal of Ophthalmology Middle East African Journal of Ophthalmology
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Year : 2009  |  Volume : 16  |  Issue : 4  |  Page : 266-268 Table of Contents     

Mild myopic astigmatism corrected by accidental flap complication: A case report

Ophthalmic Consultants of Beirut, ForeSight Foundation, Lebanon

Date of Web Publication19-Dec-2009

Correspondence Address:
Daoud C Fahed
Ophthalmic Consultants of Beirut, 20/20 Bldg, 1st Floor, Jal El Dib
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0974-9233.58414

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A 35-year-old female presented for laser in-situ keratomileusis (LASIK). Her preoperative eye exam was normal, with a preop refraction of OD -2.50 D Sph +1.25 D Cyl Χ175 and OS -2.75 D Sph +1.50 D Cyl Χ165 (cycloplegic and manifest), with 20/20 BCVA OU. The central pachymetry reading was 553 ΅m in the right eye. Preoperative topography was normal. At the start of the pendular microkeratome path, some resistance was felt, but the microkeratome continued along its path. Upon inspection of the flap, there was a central rectangle of intact epithelium with two mirror-image flaps on both sides. The flap was repositioned and LASIK was discontinued. The cornea healed with two faint thin linear vertical parallel scars at the edge of the pupil. Postoperative inspection of the blade revealed central blunting. One month postoperatively, the uncorrected visual acuity (UCVA) was 20/20. Manifest and cycloplegic refractions were plano. This is an interesting case of accidental flap complication resulting in the correction of mild myopic astigmatism.

Keywords: Accidental Flap Complication, Laser In-situ Keratomileusis, Myopic Astigmatism

How to cite this article:
Fahed DC, Fahed CD. Mild myopic astigmatism corrected by accidental flap complication: A case report. Middle East Afr J Ophthalmol 2009;16:266-8

How to cite this URL:
Fahed DC, Fahed CD. Mild myopic astigmatism corrected by accidental flap complication: A case report. Middle East Afr J Ophthalmol [serial online] 2009 [cited 2020 May 27];16:266-8. Available from: http://www.meajo.org/text.asp?2009/16/4/266/58414

   Introduction Top

Laser in-situ keratomileusis (LASIK) is an effective technique for the treatment of refractive errors. Today, it is still the most commonly performed refractive procedure, [1] despite the recent shift towards surface ablation. Flap complications secondary to microkeratome use remain a feared complication. These complications are fortunately much less frequent with the newer, third generation microkeratomes and the development of the femtosecond laser. [2]

Flap creation is known to create aberrations that can change the visual acuity; these aberrations are even more when the flap is irregular. [3],[4] Though, parallel T-cuts are known to correct astigmatism; to the best of our knowledge, there are no reports of it correcting myopic astigmatism [5],[6],[7] other than a case report of change in refraction after traumatic injury to the cornea. [8]

We report a case where the error of refraction that was intended to be corrected by LASIK was corrected by the accidental flap complication, without the use of the excimer laser.

   Case Report Top

A 35-year-old female presented for LASIK to both eyes. Her past medical history was negative. Her preoperative refraction was OD -2.50 DSph +1.25 D Cyl Χ175 and OS -2.75 DSph +1.50 D Cyl Χ165 (cycloplegic and manifest). She had a 20/20 best corrected visual acuity (BCVA) in both eyes. The central pachymetry was 553 and 555 μm in the right and left eyes, respectively. The anterior segment exam and the dilated fundus exam were non-revealing. The Schirmer's test was >30 mm/5' in both eyes. Preoperative topography was normal [Figure 1]. The keratometric readings were 44.77/43.51 Χ 94 in the right eye and 44.92/43.62 Χ 76 in the left eye.

LASIK was planned for both eyes using the Carriazo pendular microkeratome (Schwind, Kleinostheim, Germany) with the 9 mm ring and a superior hinge.

During the microkeratome path of the right eye, and after reaching adequate suction, the surgeon noticed that the cutting of the keratome was halted at the beginning of its path following which he took off his foot from the pedal and pressed the pedal again. The microkeratome continued its path forward and backward despite the initial resistance. The flap was found to have a central rectangle of intact epithelium with two mirror-image flaps on both sides. LASIK was discontinued, the torn flap was repositioned in place and a bandage contact lens applied on the corneal surface. The patient was informed of the flap complication and about the need to postpone the LASIK. She was treated with a combination of 0.1% dexamethasone (Dexa-Sine, Alcon-Couvreur) and 0.3% ciprofloxacin (Ciloxan, Alcon Inc) QID, in addition to artificial tears hourly.

Inspection of the blade revealed central notching and blunting due to its rubbing on the guard flange of the ring [Figure 2]. The protective flange of the ring was found to be bent inward, probably from trauma inflicted by the technician to the ring while cleaning it.

Two days later, two thin, faint, linear vertical parallel scars at the edge of the pupil were seen [Figure 3] and the patient had an UCVA of 20/40. Two weeks postoperative, the UCVA was 20/20. Manifest and cycloplegic refractions were plano. The vision remained stable at the 3 and 6 months postoperative visit. The patient then underwent an uncomplicated LASIK procedure in the left eye with good result at the 3 months postoperative visit.

   Discussion Top

This case illustrates the need to approach each step of the LASIK procedure carefully. The surgeon should have stopped the procedure when he felt the resistance, but fortunately the end result had no detrimental effect on the patient. We believe that following events results in this complication. The shaft of the pendular microkeratome ring was bent by trauma. The blade of the Carriazo Pendular Keratome rubbed on the metal flange at its center, resulting in a notching and blunting of its cutting edge centrally [Figure 2]. This blunting prevented proper cutting, and the result was a flap of residual corneal tissue in the central cornea. The parallel corneal cuts acted like two central parallel T-cuts, which resulted in the correction of the patient's astigmatism and myopia.

Radial keratotomy (RK) and astigmatic keratotomy have been widely used in the past to correct ametropia. The Prospective Evaluation of Radial Keratotomy Study (PERK study) evaluated the efficiency and outcome of RK. [9] However, the low predictability of results and the high diurnal fluctuation of vision resulted in limited use of these incisional surgeries, and they were replaced by the excimer laser. [10] Khokar et al. reported the correction of astigmatism by opposite, clear corneal incisions. [7] A recent case report describes the self resolution of myopia secondary to ocular trauma. [8] Incisions in the cornea increase the higher order aberrations. We previously reported on the increase in higher order aberration post-flap creation and the influence this will have on visual outcome. [11] The vision correction in this patient was probably due to a change of refraction secondary to the T-cuts, and not from the higher order aberrations that were not markedly altered (data not included). Despite the fact that the cuts in the 'T-cuts procedure' are deeper, our results show an alteration in the refraction after the procedure. This change in refraction occurred because of changes in collagen fibrils. The mid-peripheral corneal lamellae extending from limbus to limbus were cut, and this resulted in alteration of the corneal curvature [Table 1]. [12] The incisions created in the superficial stroma flattened the horizontal curvature and steepened the vertical curvature thus antagonizing the myopic astigmatism in the right eye of the patient. This case is an example of a flap complication resulting in desirable outcome for the patient.

   References Top

1.Sugar A, Rapuano CJ, Culbertson WW, Huang D, Varley GA, Agapitos PJ, et al. Laser in situ keratomileusis for myopia and astigmatism: Safety and efficacy: A report by the American Academy of Ophthalmology. Ophthalmology 2002;109:175-87.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]  
2.Lim T, Yang S, Kim M, Tchah H. Comparison of the IntraLase femtosecond laser and mechanical microkeratome for laser in situ keratomileusis. Am J Ophthalmol 2006;141:833-9.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]  
3.Buzzonetti L, Iarossi G, Valente P, Volpi M, Petrocelli G, Scullica L. Comparison of wavefront aberration changes in the anterior corneal surface after laser-assisted subepithelial keratectomy and laser in situ keratomileusis: Preliminary study. J Cataract Refract Surg 2004;30:1929-33.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]  
4.Kohnen T, Mahmoud K, Buhren J. Comparison of corneal higher-order aberrations induced by myopic and hyperopic LASIK. Ophthalmology 2005;112:1692.  Back to cited text no. 4      
5.Montes-Mico R, Munoz G, Albarran-Diego C, Rodriguez-Galietero A, Alio JL. Corneal aberrations after astigmatic keratotomy combined with laser in situ keratomileusis. J Cataract Refract Surg 2004;30:1418-24.  Back to cited text no. 5      
6.Price FW, Grene RB, Marks RG, Gonzales JS. Astigmatism reduction clinical trial: A multicenter prospective evaluation of the predictability of arcuate keratotomy. Arch Ophthalmol 1995;113:277-82.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]  
7.Khokhar S, Lohiya P, Murugiesan V, Panda A. Corneal astigmatism correction with opposite clear corneal incisions or single clear corneal incision: Comparative analysis. J Cataract Refract Surg 2006;32:1432-7.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]  
8.Reddy S, Myung J, Solomon JM, Young J. Bungee cord-induced corneal lacerations correcting for myopic astigmatism. J Cataract Refract Surg 2007;33:1339-40.  Back to cited text no. 8  [PUBMED]  [FULLTEXT]  
9.Waring GO 3 rd , Lynn MJ, Fielding B, Asbell PA, Balyeat HD, Cohen EA, et al. Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study 4 years after surgery for myopia. JAMA 1990;263:1083-91.  Back to cited text no. 9      
10.Choi DM, Thompson RW Jr, Price FW Jr. Incisional refractive surgery. Curr Opin Ophthalmol 2002;13:237-41.  Back to cited text no. 10  [PUBMED]  [FULLTEXT]  
11.Fahed DC, Fahed CD. Visual outcome and aberration measurement in patients with aborted LASIK Flaps. J Refract Surg 2007;23:14-5.  Back to cited text no. 11  [PUBMED]  [FULLTEXT]  
12.Alastrue V, Calvo B, Pena E, Doblare M. Biomechanical modeling of refractive corneal surgery. J Biomech Eng 2006;128:150-60.  Back to cited text no. 12      


  [Figure 1], [Figure 2], [Figure 3]


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