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Alternatives to Goldmann tonometry useful in certain cases, specialist says
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ROME — Goldmann applanation tonometry remains the gold standard for measuring IOP, but the Tonopen applanation tonometer and the Pascal Dynamic Contour Tonometer should be used in specific cases, according to a glaucoma specialist speaking here at the OSN Rome Symposium.
Antonio Fea, MD, said that Goldmann tonometry is still "the most reproducible system," but its precision may be affected by irregular astigmatism, corneal scars, corneal edema and reduced corneal thickness.
"For this reason, applanation tonometry might not be entirely reliable in post-refractive surgery patients," Dr. Fea said.
Pascal tonometry (Ziemer Ophthalmic Systems) is less reproducible, but also less sensitive to corneal thickness. Therefore, it seems more accurate after LASIK or PRK and in ectatic corneas, he said.
"However, we must take into account that it is more difficult to use and requires more cooperation from patients," Dr. Fea noted.
Although automated and less sensitive to the influence of corneal thickness, the Tonopen (Reichert) is also less reproducible than Goldmann tonometry, and the device tends to overestimate IOP in the extreme ranges. However, the Tonopen requires less patient cooperation and may be better for use in children and post-keratoplasty patients.
"The influence of corneal thickness on IOP measurements remains a complex issue, and no perfect answer has yet been given to this problem," Dr. Fea noted.
The OSN Rome Symposium is a meeting held jointly by Ocular Surgery News, the Italian Association of Cataract and Refractive Surgery and the Italian Society of Ophthalmology.