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San Luis Obispo, CA 93401
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Templeton, CA 93465
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Corneal Pachymetry
CPT:
76514
Definition: Determination of corneal thickness
(e.g. pachymetry) by ultrasound, with
interpretation and report.
Your measurements:
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µm
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µm
Date
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could reduce the percentage of ocular hypertensive (OHT)
patients that convert to glaucoma.The studyalso found a much
greater variation in corneal thickness in a general population
than had previously been appreciated.
The average healthy human cornea is 535 microns (µm) to
565 microns thick at the center with slightly increasing thickness toward the edges. However, individual corneas in a large
population may range from 410 µm to 725 µm in thickness.
Further, the study found that patients with thinner corneas
less than 555 µm had a more than three-fold increased risk
of developing glaucoma compared to those with thicker corneas, irrespective of their intraocular pressure. Patients with
corneal thickness between 555 µm and 588 µm had a 1.7
times increased, while those patients with corneas thicker than
588 µm were found to have no appreciable increased risk of
developing glaucoma.
orneal pachymetry is a procedure for measuring
the thickness of the cornea. Until about twenty
years ago, corneal thickness was measured with
complicated optical devices and was not particularly
accurate or reproducible. High frequency ultrasound probes
and digital electronics now allow rapid, accurate, and
reproducible measurements of the corneal thickness in the
ophthalmologist’s office.
A healthy individual’s corneal thickness does not generally
change with age. However, certain disease processes in the
cornea can cause the cornea to thicken, eventually leading
to vision loss through corneal edema and other problems.
Common disorders affecting corneal thickness include corneal
dystrophies,viral or bacterial infections, contact lens overwear,
trauma, and eye surgery.
Corneal pachymetry also has uses in refractive surgery. Back
when radial keratotomywas more common,refractive surgeons
used the pachymeter to determine the depth of their incisions.
Pachymetry is also used by LASIKsurgeons to determine if the
cornea is thick enough to withstand the corneal flap incision
and subsequent laser corneal stromal ablation.
The most recent application for pachymetry is in the diagnosis
and management of glaucoma. A correlation between corneal
thickness and accuracy of intraocular pressure measurement
has been known for some time. In brief, thick corneas cause
falsely high pressure measurements while thin corneas cause
falsely low pressure measurements. Thus, a patient with a thick
cornea could show a high measured intraocular pressure while
their true pressure may be much lower. This could lead to misdiagnosis or over-treatment of glaucoma. Conversely, a patient
with a thin cornea could show a normal measured intraocular
pressure while their true pressure may be much higher, thus
leading to possible under-treatment of glaucoma.
Even more important are the findings of the recently published
Ocular Hypertension Treatment Study1,2. This study showed
that early intervention with pressure-lowering medications
This study has revolutionized our understanding and management of glaucoma and has boosted corneal pachymetry
from a seldom-utilized ancillary test to standard-of-care in the
diagnosis and management of ocular hypertension, glaucoma
suspect and primary open-angle glaucoma3.
In summary, corneal pachymetry is useful for the
documentation and quantification of corneal edema secondary
to corneal disease, trauma or surgery. With the release of the
Ocular Hypertension Study, corneal pachymetry is also now
the standard of care for the diagnosis and management of
ocular hypertension, glaucoma suspect, and the full spectrum
of glaucomatous disease. 
REFERENCES
1.
Gordon MO, Beiser JA, Brandt JD, Heuer DK, Higginbotham EJ, Johnson CA, Keltner JL, Miller JP, Parrish II RK,
Wilson MR, Kass MA, OHTS Group. Ocular Hypertension Treatment Study: baseline factors that predict the
onset of primary open-angle glaucoma. Arch Ophthalmol
2002;120:714-20.
2.
BrandtJD,BeiserJA,Kass MA,Gordon MO,OHTS Group.
Central corneal thickness in the ocular hypertension
treatment study (OHTS). Ophthalmology 2001;108:17791788.
3.
Preferred Practice Patterns: Primary Open-Angle Glaucoma Suspect (limited revision). American Academy of
Ophthalmology, rev. October 2002, pg 9.
050207