Coding & Reimbursement

By Suzanne L. Corcoran, COE

Measurement of Corneal Hysteresis

Ophthalmologists continue to search for ways to provide better care for their patients. Diagnostic tests that identify potential problems are valuable in this regard. Measurement of corneal hysteresis is such a test. What is it, and what do ophthalmologists and their administrators need to know about reimbursement?

Q. What is corneal hysteresis and why should it be measured? Hysteresis is defined as the lagging of an effect behind its cause, as when some neurons do not return to their basal conditions from a stimulated condition immediately after removal of the stimulus. Hysteresis is a property of systems that do not instantly respond to forces applied to them, but react slowly, or do not return completely to their original state. That is, hystereis is systems whose states depend on their immediate history.

For example, consider a suspension strut on a car that contains both a coil spring and a shock absorber. When the vehicle hits a bump, the coil spring rapidly compresses in response to the force of the blow. Left unchecked, the coil spring would return all of the energy very rapidly, causing the car to bounce uncontrollably. However, at the center of the coil spring, the shock absorber dampens the movement of the spring, allowing the vehicle to rapidly return to a smooth, controlled ride. In this example, the spring has very low hysteresis, but the shock absorber has high hysteresis. The human cornea is very similar, in principle, and this hysteresis phenomenon can be measured.

Measuring the biomechanical properties of the cornea enables practitioners to quantify various corneal conditions. Low corneal hysteresis (CH) demonstrates that the cornea is less capable of absorbing the energy of the air pulse. Clinical studies suggest that a low CH measurement may indicate ocular abnormalities or corneas at risk for disease.¹

The human corneal tissue is a complex viscoelastic structure. Studies suggest that subjects whose corneas demonstrate low CH, which can be considered a soft cornea, may be at greater risk for an array of ocular diseases and surgical complications.¹ CH testing is useful in identifying abnormal corneal conditions, evaluating IOP measurements and assessing the potential for complications following corneal refractive surgery.

Hysteresis Measurement

Q. How is hysteresis coded? Category III CPT code 0181T (Corneal hysteresis determination, by air impulse stimulation, bilateral, with interpretation and report) should be used to report this test.

Q. Is it covered? Sometimes. Medicare does not assign relative value units or a dollar value to Category III CPT codes. Reimbursement is determined on a case-by-case basis at the discretion of the payer. Pachymetry (CPT 76514) provides a useful starting point for establishing a value. Policies will vary.

When coverage is in question and third party payers.

Q. What documentation is required? The medical record should contain:

► Patient’s name and date of test

► Order for the test with medical rationale

► Results of the test (i.e., printout)

► Interpretation of the test

► Signature of physician

► Hysteresis measurement. OM

Reference

1. Luce DA. Determining in vivo biomechanical properties of the cornea with an ocular response analyzer. |J of Cat. & Refract Surg. Jan.2005: 31:1: 156-62