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 Table of Contents  
CASE REPORT
Year : 2017  |  Volume : 18  |  Issue : 3  |  Page : 182-184

Misinterpretation of topographic early keratoconus, with consequent post small-incision lenticule extraction ectasia


Department of Ophthalmology, Cairo University, Cairo, Egypt

Date of Submission14-Jan-2017
Date of Acceptance01-Apr-2017
Date of Web Publication17-Oct-2017

Correspondence Address:
Sherif A Eissa
Department of Ophthalmology, Cairo University, Kasr El Ainy, Cairo, 11451
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/DJO.DJO_1_17

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  Abstract 

The purpose of this paper is to describe an infrequent complication of small-incision lenticule extraction. Bilateral corneal ectasia that was discovered 6 months postoperatively is described here. The case has shown that the procedure can aggravate early keratoconus cases without any advantage over laser in-situ keratomileusis or surface ablation procedures. Placido disk imaging with correct scaling and color coding of Scheimpflug images is essential in the preoperative assessment of small-incision lenticule extraction patients.

Keywords: ectasia, keratoconus, placido, Scheimpflug, SMILE


How to cite this article:
Eissa SA. Misinterpretation of topographic early keratoconus, with consequent post small-incision lenticule extraction ectasia. Delta J Ophthalmol 2017;18:182-4

How to cite this URL:
Eissa SA. Misinterpretation of topographic early keratoconus, with consequent post small-incision lenticule extraction ectasia. Delta J Ophthalmol [serial online] 2017 [cited 2021 Oct 16];18:182-4. Available from: http://www.djo.eg.net/text.asp?2017/18/3/182/216916


  Introduction Top


Femtosecond lenticule extraction and small-incision lenticule extraction (SMILE) have not been thoroughly investigated. However, they have shown encouraging results in the treatment of myopia and myopia with mild to moderate astigmatic error [1],[2]. SMILE represents a less invasive alternative to laser in-situ keratomileusis (LASIK) for the correction of myopic error, without disruption of the Bowman’s layer. However, microdistortions have been observed in the Bowman’s layer in patients who had SMILE, which resulted from unavoidable tissue compression from shortening of the cap’s arc length, without adversely affecting vision [3].


  Case history Top


A 26-year old Egyptian male patient presented with a history of previous SMILE (Carl Zeiss Meditec AG, Jena, Germany) procedure in Egypt 5 months earlier. He complained of progressively decreasing vision in his left eye with glare and halos in both eyes (OU). His visual acuity was 20/30 in the right eye that corrects to 20/25 with −0.75/−0.75×10. Left eye visual acuity was 20/400 and corrects to 20/100 with −8.50 spherical error. Corneal topography (OPD scan II, Nidek, Japan) and Scheimpflug-based corneal topography (Pentacam; Oculus Optikgerate GmbH, Wetzlar, Germany) were performed and showed ectasia which is more advanced in the left eye with inferior corneal steepening in both eyes as well as high posterior elevation in the left eye ([Figure 1] and [Figure 2], respectively). The patient had his preoperative glasses prescription of −6.75/−0.50×40 (right eye) and −7.25/−0.75×40 (left eye). His preoperative Pentacam image showed thinnest location on pachymetry map of 505 µm left eye and 524 µm right eye as shown in [Figure 3]. Corneal thickness spatial profile showed normal pattern both eyes. Keratometry readings on the anterior corneal surface sagittal map were relatively flat (right eye: 41.9 and 42.5 D and left eye: 43.0 and 43.6 D), which tempted the surgeon to proceed with SMILE, especially with cold color code and wrong scaling on the posterior elevation map (5 μm). However, the surgeon overlooked suspicious indices, especially in the absence of placido disk imaging on preoperative assessment. Suspicious findings included posterior elevation of +20 μm in both eyes at the border of the central 5 mm circle, high index of height decentration and index of height asymmetry, especially in the left eye, and high I–S ratio on sagittal map left eye, with an early vortex pattern.
Figure 1 OPD scan 6 months following SMILE showing ectasia in both eyes.

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Figure 2 Bilateral Ectasia 6 months post-SMILE as shown by pentacam.

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Figure 3 Pentacam before SMILE procedure, misinterpreted as normal tomography.

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  Discussion Top


Although Wu and Wang [4] have found a statistically significant elevation in corneal hysteresis and corneal resistance factor in SMILE, compared with femtosecond laser-assisted LASIK, the superiority of biomechanical stability with SMILE has not been convincingly demonstrated and future analysis should clarify this aspect [4].

Sinha Roy et al. [5] in another study concluded that SMILE poses less biomechanical risk to the residual corneal stroma of susceptible corneas than a similar correction using LASIK flaps. SMILE preserves the anterior corneal stromal integrity, which is thought to provide mainly corneal strength, thus minimizing the risk of postoperative ectasia. However, the actual removal of corneal stromal tissue in the SMILE procedure can weaken the cornea to some extent [6].

A case report by El Najar described a case of bilateral ectasia following SMILE, with preoperative topography showing the classic full-blown picture of keratoconus. To the best of the author’s knowledge, this is the first report of ectasia after femtosecond laser-assisted SMILE over very early keratoconus, with misinterpreted preoperative topography. Placido disk imaging with correct scaling and color coding of Scheimpflug images in the preoperative assessment of SMILE patients is crucial to guard against skipping latent warning signs of ectasia.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Sekundo W, Kunert K, Russmann C, Gille A, Bissmann W, Stobrawa G et al. First efficacy and safety study of femtosecond lenticule extraction for the correction of myopia; six-month results. J Cataract Refract Surg 2008; 34:1513–1520.  Back to cited text no. 1
    
2.
Sekundo W, Kunert K, Blum M. Small incision corneal refractive surgery using the small incision lenticule extraction (SMILE) procedure for the correction of myopia and myopic astigmatism: results of a 6-month prospective study. Br J Ophthalmol 2011; 95:335–339.  Back to cited text no. 2
    
3.
Yao P, Zhao J, Li M, Shen Y, Dong Z, Zhou X. Microdistortions in Bowman’s layer following femtosecond laser small incision lenticule extraction observed by Fourier-domain OCT. J Refract Surg 2013; 29:668–674.  Back to cited text no. 3
    
4.
Wu W, Wang Y. The correlation analysis between corneal biomechanical properties and the surgically induced corneal high-order aberrations after small incision lenticule extraction and femtosecond laser in situ keratomileusis. J Ophthalmol 2015; 2015.  Back to cited text no. 4
    
5.
Sinha Roy A, Dupps WJ Jr, Roberts CJ. Comparison of biomechanical effects of small-incision lenticule extraction and laser in situ keratomileusis: finite-element analysis. J Cataract Refract Surg 2014; 40:971–980.  Back to cited text no. 5
    
6.
El-Naggar MT. Bilateral ectasia after femtosecond laser-assisted small-incision lenticule extraction. J Cataract Refract Surg 2015; 41:884–888.  Back to cited text no. 6
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]



 

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