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

Difference in Slit Lamp Measurements

0

1

2

3

4

5

1 2 3 4 5 6 7 8 9 10 11 12 13

pterygia

mm Physician A

Physician B

SD = 0.32

MD = 0.30

Results

Results

00.5

11.5

22.5

33.5

4

1 2 3 4 5 6 7 8 9 10 11 12 13

pterygia

mm Image 1

Image 2

SD = 0.12

MD = 0.1

Difference in OCT Measurements

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.

References1. Buchwald HJ, Muller A, Spraul CW, Lang GK. Ultrasound Biomicroscopy of Conjunctival Lesions. Klin Monatsbl

Augenheilkd. 2003 Jan-Feb; 220(1-2):29-34.2. Buchwald HJ, Muller A, Kampmeier J, Lang GK. Optical Coherence Tomography versus Ultrasound Biomicroscopy of

Conjunctival and Eyelid Lesions. Klin Monatsbl Augenheilkd. 2003 Dec; 220(12):822-9.3. Baikoff G, Lutun E, Ferraz C, and Wei J. Static and Dynamic Analysis of the Anterior Segment With Optical Coherence

Tomography. J Cataract Refract Surg. 2004 Sep; 30(9):1843-50.4. Adamis AP, Starck T, Kenyon KR. The Management of Pterygium. Ophthalmol Clin North Am. 1990; 2(4):611.5. Kent C. Breaking New Ground in Ultrasound. Review of Ophthalmology. 2006 Nov; 13(11):22-26.6. Lin, H, Shen S, Huang S, Tsai R. Ultrasound Biomicroscopy in Pigmented Conjunctival Cystic Nevi. Cornea. 2004 Jan;

23(1):97-99.7. Solomon A, Kaiserman I, Raiskup F, Landau D, Frucht-Pery J. Long-term Effects of Mitomycin C in Pterygium Surgery on

Scleral Thickness and the Conjunctival Epithelium. Ophthalmology. 2004 Aug; 111(8):1522-1527.8. Dada T, Sihota R, Gadia R, Aggarwal A, Mandal S, Gupta V. Comparison of Anterior Segment Optical Coherence

Tomography and Ultrasound Biomicroscopy for Assessment of the Anterior Segment. J Cataract Refract Surg. 2007 May; 33:837-840.

9. Emmy YM, Mohamed S, Leung C, Rao S, Cheng A, Cheung C, Lam D. Agreement Among 3 Methods to Measure Corneal Thickness: Ultrasound Pachymetry, Orbscan II, and Visante Anterior Segment Optical Coherence Tomography. Opthalmology. 2007 October; 114(10):1842-1847.

10. Fujimoto JG. Optical Coherence Tomography: Introduction. In: Bouma BE, Tearney GJ, eds, Handbook of Optical Coherence Tomography. New York, NY, Marcel Dekker, 2002; 1-40.

11. Goldsmith J, Li Y, Regina M, Chalita MR, Westphal V, Patil C, Rollins AM, Izatt JA, Huang D. Anterior Chamber Width Measurement by High-Speed Optical Coherence Tomography. Ophthalmology. 2005 Feb; 112(2):238-244.

12. Lin A, Stern G. Correlation between pterygium size and induced corneal astigmatism. Cornea. 17:1998; 28-30.13. Payman A, Mohammed-Salih, Ahmad F, Sharif . Analysis of Pterygium Size and Induced . Corneal Astigmatism.

Cornea. 27: 2008; 434-438.