Pterygia Measurements With A Standard Slit Lamp Beam

Pterygia Measurements With A Standard Slit Lamp Beam Compared To Caliper Measurements On Anterior Segment Optical Coherence Tomography Images : Pilot Study Mark Welch, DO, Kevin Kalwerisky, MD, and Steven Waller, MD No financial interest

Disclaimer • The view(s) expressed herein are those of the author(s) and do not reflect the official policy or position of Brooke Army Medical Center, the U. S. Army Medical Department, the U. S. Army Office of the Surgeon General, the Department of the Army, Department of Defense or the U. S. Government.

Background • Previous Studies Demonstrating Anterior Segment OCT measurements include: – Anterior Chamber Dimensions – Intraocular Lens Position – Corneal Thickness – Corneal thinning after Mitomycin C • Clinical challenges of pterygium measurements – Subjectivity of Slit Lamp measurements – Cannot measure thickness with Slit Lamp

Purpose • Compare horizontal measurements of pterygia by slit lamp beam to caliper measurements overlayed on Anterior Segment OCT images

Methods • 10 Patients and 13 nasal pterygia were evaluated. Patients with significant ocular surface disease were excluded. – Horizontal measurements were taken by two physicians with the slit lamp beam at 16 magnification • Measurements were taken from the apex of the lesion to the limbus – Two images of lesions with Anterior Segment OCT were obtained • Caliper measurements of lesions from apex to limbus

Methods • Example of INCORRECT meridian to see lesion – 45 degrees – no lesion seen • Example of CORRECT meridian at 180 degrees images the lesion

Visante OCT Measurements Caliper Measurements

Results Difference in Slit Lamp Measurements MD = 0. 30 SD = 0. 32

Results Difference in OCT Measurements MD = 0. 1 SD = 0. 12

Conclusions • Anterior Segment OCT gives statistically more reproducible results than slit lamp for horizontal measurements of pterygia (P=0. 0256). • Anterior Segment OCT can reproduce measurements in the same axis meridian and appears to be less subjective with regard to the starting and stopping point for making measurements. • Anterior Segment OCT can provide thickness measurements of pterygia.

Study Limitations • Small number of patients. • Inherent variability of slit lamp measurements. • Larger study needed to correlate pterygium dimensions (including thickness) with need for surgery. – Anecdotally, in this study, it was found that pterygium thickness is a better predictor of symptoms than horizontal extent onto the cornea.

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