September 2014 Online Photo Diagnosis
By Luciano Bastos
This 14-year-old female patient who had been diagnosed with keratoconus was referred to our clinic for visual rehabilitation with specialty contact lenses. During biomicroscopy, we initially observed that the cornea showed no evidence of stromal thinning. The tear breakup time (TBUT) was three to four seconds for both eyes. We also observed small dots on the corneal epithelium. We initially thought that these were corneal infiltrates, but they were small epithelial defects (Figure 2).
Figure 2. No evidence of significant stromal thinning, but notice the epithelial defects. The slit lamp image is turned to the right for better view.
Beyond the epithelial defects, we observed stromal neovascularization (Figure 3) and an unstable tear film. There was also a mild, localized keratinization, probably due to the unstable tear film.
Figure 3. Stromal neovascularization.
Differential Diagnosis
Her keratometry readings and prescription (Rx) showed a high degree of corneal astigmatism and non-significant spherical error. Her keratometry readings were OD 44.37 @ 9x50.00 @ 99 and OS 44.35 @ 163x49.25 @ 73. The Rx was OD +0.12 –6.62 X 11 and OS –0.25 –7.12 X 125.
Although the patient had been diagnosed with keratoconus, we found no evidence of corneal thinning. However, a very steep meridian may have led her ophthalmologist to make a premature diagnosis (Figure 2). It appeared to be only a high corneal cylinder.
Follow-up Findings
We scheduled the patient for an anterior segment tomography by Pentacam HR (Oculus) evaluation to verify the overall aspect of the cornea, especially to confirm our initial findings that the patient did not have keratoconus (Figure 4). We needed this both to confirm the differential diagnosis and to allow us to properly instruct the parents. We also sent the patient for an impression cytology exam.
Figure 4. Anterior segment tomography of the patient’s right and left eyes.
The patient was ultimately diagnosed with limbal stem cell deficiency (LSCD). Note the presence of neovascularization from the upper limbus that is entering the superior corneal periphery. We believe that scleral lens fitting may help her, but first we need to send the patient to another doctor specialized in treating LSCD.