This article is more than 5 years old. Information may no longer be current.
Epithelial thickness varies across central cornea
VHF digital ultrasound measures epithelial thickness within 1-µm precision, study author says.
Click Here to Manage Email Alerts
Epithelial thickness is uneven across the cornea, according to a recent study in which VHF digital ultrasound was used to measure epithelial thickness.
 Dan Z. Reinstein |
The epithelium was thicker in the inferior and nasal areas than in the superior and temporal areas, Dan Z. Reinstein, MD, and colleagues reported in the Journal of Refractive Surgery.
The findings refuted previous data on epithelial thickness, Prof. Reinstein said in a telephone interview with Ocular Surgery News.
“The most significant thing was that we blew out of the water prior folklore about epithelial thickness because every study that’s ever been done that tried to map the thickness of the epithelium across the cornea has stated that the thickness is even throughout the whole cornea,” he said.
Researchers used the Artemis 1 VHF digital ultrasound arc-scanner (ArcScan) to measure epithelial thickness within the central 8-mm to 10-mm corneal diameter.
The retrospective, noncomparative case series included 110 eyes of 56 patients with a mean age of 38.4 years. Patients with keratoconus, corneal scarring, corneal dystrophy and previous ocular surgery were excluded, the authors said.
Mean epithelial thickness at the corneal vertex in all eyes was 53.4 µm (range, 43.5 µm to 63.6 µm). On average, the epithelium was 6-µm thicker in the inferior cornea and thinner in the superior cornea (P < .001), and 1.8-µm thicker nasally than temporally ( P < .001). On average, the thinnest epithelium was displaced 0.33 mm temporally and 0.9 mm superiorly to the corneal vertex, the authors reported.
Measurement of the epithelial thickness profile and knowledge of the epithelial thickness profile in a normal population may aid in the diagnosis of corneal diseases such as keratoconus, a contraindication for LASIK, Prof. Reinstein said.
“I am convinced that epithelial thickness mapping will be the next most powerful diagnostic tool to the corneal and refractive surgeon since topography of the back surface was introduced,” Prof. Reinstein said. – by Matt Hasson
The take-home message is that in dealing with the anatomy of the cornea, the thickness of the epithelium, which most of us have always believed to be somewhere around 50 µm and somewhat evenly distributed across the cornea, is actually not evenly distributed but thicker inferiorly and nasally. This gives us new information about the anatomy of the cornea that was previously not known and expands the strength of our diagnosis in the prescreening of refractive surgery.
Ronald Krueger, MD
Medical Director, Department of
Refractive
Surgery, Cole Eye Institute, Cleveland Clinic
Reference:
- Reinstein DZ, Archer TJ, Gobbe M, Silverman RH, Coleman DJ. Epithelial thickness in the normal cornea: three-dimensional display with Artemis very high-frequency digital ultrasound. J Refract Surg. 2008;24:571-581.
- Dan Z. Reinstein, MD, can be reached at London Vision Clinic, 8 Devonshire Place, London W1G 6HP, United Kingdom; 44-207-224-1005; e-mail: dzr@londonvisionclinic.com.