|Year : 2017 | Volume
| Issue : 3 | Page : 182-184
Misinterpretation of topographic early keratoconus, with consequent post small-incision lenticule extraction ectasia
Sherif A Eissa
Department of Ophthalmology, Cairo University, Cairo, Egypt
|Date of Submission||14-Jan-2017|
|Date of Acceptance||01-Apr-2017|
|Date of Web Publication||17-Oct-2017|
Sherif A Eissa
Department of Ophthalmology, Cairo University, Kasr El Ainy, Cairo, 11451
Source of Support: None, Conflict of Interest: None
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|| |
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 ,. 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 .
| Case history|| |
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 3 Pentacam before SMILE procedure, misinterpreted as normal tomography.|
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| Discussion|| |
Although Wu and Wang  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 .
Sinha Roy et al.  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 .
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
Conflicts of interest
There are no conflicts of interest.
| References|| |
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[Figure 1], [Figure 2], [Figure 3]