Spark ImageWise 25 – Cornea

Corneal Erosions Mimicking Corneal Ectasia

Dr Prabhat Nangia, Dr Sarang Lambat, Dr Vinay Nangia 
559, Suraj Eye Institute, Nagpur.

Case Description
A female, 21 years of age, came with chief complaint of blurring of vision in right eye (OD) along with foreign body sensation since 6 weeks. There was a history of repair work in her home around the time of onset of symptoms. There was no history of frequent change of glasses. On examination, the best corrected visual acuity (BCVA) was 6/6 in OD with -2DS/+2DC at 70 degrees, and 6/6 in left eye (OS) with -2.75DS/+3.75DC at 75 degrees. Slit lamp examination appeared grossly within normal limits on diffuse illumination. Due to history of blurring of vision along with asymmetrical cylindrical refractive error in both eyes, corneal tomography was done prior to further detailed ophthalmic evaluation.

Figure 1: Shows tomography of right eye at presentation. Anterior surface axial curvature map showed an asymmetric bow tie with inferior steepening (black arrow), a steep K value of 45.41 D (black circle) and Kmax of 48.48 D (green arrow). Thinnest pachymetry however, was 523 microns and posterior elevation map also was not suggestive of corneal ectasia.
Figure 2: Shows tomography of left eye at presentation. Anterior axial curvature map  showed a symmetric bow tie pattern and with-the-rule astigmatism (black arrow). Steep K value was 44.40 D (black circle) and Kmax was 44.55 D (green arrow). Thinnest pachymetry was 511 microns and posterior elevation map was within normal limits.

Slit lamp evaluation with fluorescein staining showed a paracentral area of negative staining in OD, possibly due to loose epithelium in that area. A bandage contact lens (BCL) was placed over the right eye and she was advised to use lubricating and antibiotic eye drops. 

Figure 3: Shows the right eye slit lamp image with fluorescein staining using cobalt blue filter for illumination and yellow filter for viewing, taken during follow up visits. 
Fig. 3A shows stippled appearance of the paracentral area due to epithelial erosions at one week follow up (white arrow). 
Fig. 3B shows healing erosions, with minimal negative staining at the edges of the affected area (white arrow), at two and a half weeks follow up.  

After five more weeks, the patient was reviewed, and the epithelium was healed completely. 

Figure 4a Shows the right eye slit lamp image under diffuse illumination, which showed nebular scars in the area where corneal erosions were initially seen (white arrow). 
Figure 4B
shows the right eye stained with fluorescein, showing no evidence of any active corneal erosions. 
Figure 5 shows repeat tomography of right eye at follow up. Anterior surface axial curvature map showed a symmetric bow tie pattern and with-the-rule astigmatism (black arrow). The Steep K was 43.74 D (black circle) and the Kmax was 44.21 D (green arrow). Corneal pachymetry and posterior elevation maps were within normal limits. There was no evidence of any ectasia in right eye.
Figure 6 shows difference map of the axial curvature of right eye at initial presentation (From Fig. 1) and follow up visit after complete healing (from Fig. 5). The significant flattening in the inferior paracentral cornea is noteworthy (black arrow). 

Discussion

Our patient was diagnosed to have recurrent corneal erosions in right eye, most likely following trivial trauma from a foreign body during the repair work at her home, along with erroneous topography which lead us to suspect that she may have corneal ectasia. However, the reversion of topography to normal that occurred once the erosion healed, lead us to retrospectively analyse the reason for the error. We believe that the loose thickened epithelium lead to an area of steepening. Once the epithelium regained normal thickness, the topography normalised.

 Reinstein et al have described the role of epithelial thickness compensation in keratoconus and in irregular corneas, stating that in case there is an area of stromal thinning such as a healed ulcer, the epithelium over that area undergoes significant thickening, thereby trying to normalise the topography to the extent possible by compensating for the flattening effect of the reduced stromal thickness. This epithelial hyperplasia has also been associated with regression of myopia (which is essentially re-steepening of the cornea flattened with the excimer laser) post photo refractive keratectomy. It follows that whenever the epithelium undergoes localised thickening, such as loose epithelium in recurrent erosions, this may manifest as erroneous steepening on topographical evaluation. This is what happened in our patient, which got rectified with normalisation of the epithelium. 

With this case, we wish to highlight the possibility of topographical errors leading to an incorrect diagnosis of corneal ectasia. It is also important to study the posterior elevation and corneal pachymetry maps in cases of suspected ectasia, which were completely normal in our case, implying that this is almost certainly not a case of ectasia. 

ReadWise 

  1. Reinstein DZ, Arthur TJ, Gobbe M. Rate of change of curvature of the corneal stromal surface drives epithelial compensatory changes and remodelling. J Refract Surg 2014 Dec;30(12):799-802  https://doi.org/10.3928/1081597X-20141113-02
  1. Gauthier CA, Holden BA, Epstein D, et al. Role of epithelial hyperplasia in regression following photorefractive keratectomy. British Journal of Ophthalmology 1996;80:545-548 http://dx.doi.org/10.1136/bjo.80.6.545

Correspondence 

Dr Prabhat Nangia
DNB, FICO, FMRF, FAICO
Consultant  
Department of Cornea and Ocular Surface
Suraj eye Institute
Email – education@surajeye.org

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