Corneal Striae in Keratoconic and Non-Keratoconic Eyes

A 22-year-old Caucasian male presented to our office with recent onset ocular discomfort in both eyes and reduced vision OS. He specifically complained of itching and admitted that he frequently rubbed his eyes when they were irritated.

Presenting visual acuities without spectacle correction were OD 20/30 and OS 20/60. Refraction improved his acuities to OD 20/25 and OS 20/30. Biomicroscopy revealed bilateral conjunctival injection and papillae. We also noted small, linear, vertical striae isolated to the central left cornea that appeared to be located at the interface of the posterior stroma and the corneal endothelium.

We treated the patient for allergic conjunctivitis and asked him to return for additional testing. Subsequent corneal topography revealed findings consistent with a diagnosis of bilateral asymmetric keratoconus, which was more advanced in the left eye. We eventually fit the patient in keratoconus contact lenses that he has worn successfully.

Keratoconus Diagnosis

Keratoconus is a non-infectious, non-inflammatory ectatic disorder of the cornea that is often progressive. Early in the disease process, it may be difficult to diagnose. Shirayama-Suzuki et al¹ reported that over a period of six years, only 20% of eyes initially suspected of keratoconus were definitively diagnosed with the disease.

Corneal striae are a relatively common finding in keratoconus. The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study reported that 35% of participants who have keratoconus had unilateral corneal striae and a 30% of had bilateral striae.²

The following question has intrigued researchers for years: In individuals who have bilateral keratoconus, why are striae present in one cornea but not in the other? A recent Iranian study addressed this very question. In that study, Ostadi-Moghaddam et al³ evaluated the corneal endothelial cells in patients who have bilateral keratoconus but unilateral striae. Those researchers studied corneal endothelial cell density, cell size, and corneal thickness. They found that reduced corneal thickness was the only variable that correlated with the occurrence of striae.

Keratoconic Versus Non-Keratoconic Eye Variations

Keratoconus has long been linked to the presence of corneal striae; our patient is an excellent example. But what may not be widely appreciated is the occurrence of corneal striae in non-keratoconic eyes. Grieve et al⁴ used full-field optical coherence tomography (OCT) and reported the presence of striae independent of the presence of keratoconus.

Using optical coherence microscopy (OCM), a variant of OCT that has been used to map biological cells such as onion skin and red blood cells, the researchers evaluated the structure of corneal striae in keratoconic and non-keratoconic eyes. Their findings suggest that corneal striae are present in both and at a much higher rate than is commonly believed. According to this study, OCM has great potential for helping practitioners understand various corneal anomalies as well as diseases such as glaucoma.

References

1. Shirayama-Suzuki M, Amano S, Honda N, Usui T, Yamagami S, Oshika T. Longitudinal analysis of corneal topography in suspected keratoconus. Br J Ophthalmol. 2009 Jun;93:815-819.
2. Zadnik K, Joseph T. Barr JT, et al. Baseline Findings in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Invest Ophthalmol Vis Sci. 1998 Dec;39:2537-2546.
3. Ostadi-moghaddam H, Sedaghat M, Rakhshandadi T, Rajabi S, Narooie-Noori F, Askarizadeh F. A contralateral eye study comparing characteristics of corneal endothelial cells in bilateral keratoconus patients with unilateral corneal Vogt's striae. J Curr Ophthalmol. 2018 Sep;30:228-233.
4. Grieve K, Ghoubay D, Georgeon C, et al. Stromal striae: a new insight into corneal physiology and mechanics. Sci Rep. 2017 Oct 19;7:13584.