Corneal pachymetry using ultrasound is a specialized, noninvasive, ophthalmologic procedure that uses a pachymeter to measure corneal thickness. Measurements of central corneal thickness are performed by applying a topical anesthetic to the eye and placing an ultrasound probe on the central cornea where ultrasonic wave energy is passed into the eye.
Corneal pachymetry using ultrasound is primarily used to assist with the diagnosis, assessment, and/or monitoring of corneal diseases and to assess suspected or established glaucoma. For example, corneal pachymetry using ultrasound is used to assist with the diagnosis of corneal thinning disorders (e.g., keratoconus, keratoglobus, keratotorus, posterior keratoconus, pellucid marginal degeneration). Corneal pachymetry using ultrasound is also included in the assessment and/or monitoring of disease progression of many conditions or injury affecting the cornea such as Fuchs' endothelial dystrophy, posterior polymorphous dystrophy, corneal edema, endothelial disease from any etiology, bullous keratopathy, corneal ectasia, and corneal trauma.
Corneal pachymetry using ultrasound is an important component of the assessment and management of intraocular pressure and glaucoma. Corneal thickness is important because it can mask an accurate reading of intraocular pressure in glaucoma. Actual intraocular pressure may be underestimated in individuals with thinner central corneal thickness or overestimated in individuals with thicker central corneal thickness. Because intraocular pressure is reportedly the most important and only variable risk factor for glaucoma progression, knowledge of the central corneal thickness is important in managing individuals with either suspected or established glaucoma. Repeat measurements of central corneal thickness for suspect or established glaucoma is not indicated unless the individual has corneal disease or has had surgery affecting corneal thickness. Corneal pachymetry for suspected or established glaucoma only needs to be performed once to obtain baseline glaucoma risk information.
In addition to assisting with the diagnosis, assessment, and/or the monitoring of corneal diseases and assessing suspected or established glaucoma, corneal pachymetry using ultrasound is valuable in the selection of appropriate surgical techniques and assessment of the individual's risk and response to certain ophthalmologic surgical procedures (e.g., corneal transplant surgery, cataract surgery). Corneal pachymetry using ultrasound is effective in aiding the early diagnosis and/or treatment of corneal transplant rejection, as well as assessing the response to treatment of corneal graft rejection. The procedure may be used to assess corneal graft health. Corneal pachymetry using ultrasound is also considered for assessing the risk of corneal decompensation before and after cataract surgery for individuals with endothelial disease.