**Abstract:**  
  
There are two methods used for intraocular lens power calculation:

  * A-Scan Ultrasound Ophthalmic Biometry  
  
Ophthalmic A-scan biometry by ultrasound echography is performed through the
optical axis of the eye to determine the power of an intraocular (IOL) lens
implant. The technical portion of ophthalmic biometry is usually performed in
both eyes at the same setting.  
  

  * Non-Ultrasound Ophthalmic Biometry  
  
Optical coherence biometry (OCB) utilizes partial coherence interferometry for
measuring axial length (biometry) and for intraocular lens power calculation
when planning for cataract surgery. OCB also measures the corneal curvature
and anterior chamber depth. The technical portion is usually performed in both
eyes at the same visit.

**Indications:**  
  
A diagnostic ultrasound A-scan generally is used for patients who have simple
cataracts. For patients with a dense cataract, an ultrasound B-scan may be
used. _(CMS Publication 100-03, _Medicare National Coverage
Determinations(NCD)Manual_ , Chapter 1, Part 1, Section 10.1) _ _  
  
_ A second complete A scan/OCB will be covered if a different surgeon,
unaffiliated with the surgeon who performed the first cataract extraction,
performed the extraction on the second eye. We would not anticipate a high
frequency of these instances. _  
  
_ **Limitations:** _  
  
_Currently, the relative value units (RVUs) for the global and technical
components of each method of ophthalmic biometry for intraocular lens power
calculation are based on the procedure being bilaterally performed. If
unilateral cataract extraction with an IOL implant is planned, a bilateral
technical component of the A-scan or OCB is typically performed, while the
professional component of the power calculation is performed unilaterally (on
the operative eye only). Thus, the technical components are considered
bilateral and the professional component is considered unilateral.  
  
Prior to cataract surgery on the second, contralateral eye, allowance for the
power calculation can be made. However, allowance for the technical component
of the A-scan or OCB CPT code cannot be made since this bilateral procedure
was performed and reimbursed at the time of the first surgery.  
  
The technical component of the scan will generally provide valid information
for twelve months. A repeat scan in less than twelve months would not be
covered without documentation of significant change in vision (unless required
because a second unaffiliated surgeon performed the second cataract
extraction.) Generally, when bilateral cataracts are noted at examination,
extraction of the second cataract is only performed after results of the first
cataract extraction are known and symptoms or findings support the medical
necessity for removal of the cataract in the other eye. If ophthalmic biometry
is performed and later the surgery is canceled, it is reasonable to allow a
repeat scan if significant time, e.g., greater than one (1) year, has elapsed
when surgery is rescheduled.  
  
Ophthalmic biometry for lens power calculation should not be performed unless
a decision to remove the cataract has been made by the patient and surgeon. If
the biometry is performed by an optometrist, he/she should do so in
coordination with the operating surgeon so that only one procedure is
necessary. If the biometry is repeated by the operating surgeon due to
inadequacy of the study, the original eye care physician/provider should
anticipate not being reimbursed for the study.  
 _  
_