Physician still most important 'diagnostic imager'

April 15, 2009

The clinical exam remains the key to ophthalmologists' decision-making related to the diagnosis and determination of progression of glaucoma. "Baseline" technology in ophthalmology practices includes the slit lamp, some lenses, a gonio prism, an automated perimeter, a pachymeter, and optic nerve imaging capability. Other technology, however-such as confocal scanning laser ophthalmoscopy; nerve fiber layer imaging devices capable of scanning laser polarimetry and optical coherence tomography (OCT); and some anterior segment imaging technologies, including ultrasound biomicroscopy and anterior segment OCT-do not yet have absolute sensitivity and specificity and serve as aids to, not replacements for, the ophthalmologist.

Key Points

In a separate interview with Ophthalmology Times, Dr. Rhee, an assistant professor of ophthalmology at Harvard Medical School, Boston, said, "I do feel that technology has its usefulness in our clinical practices," for instance in helping clinicians see evidence of structural damage and glaucomatous disease in the optic nerve or in the nerve fiber layer before it is apparent via achromatic, white-on-white visual field testing.

"But quite frankly, to screen every single patient who comes into your office with these technologies is not practical, nor is it cost-effective, and it certainly is inconvenient for both the practitioner and the patient," he added. And even if every patient were screened, Dr. Rhee said, some instances of disease would remain undetected because of issues related to test sensitivity and specificity.

No 'technology vacuum'

Ophthalmologists cannot practice "in a technology vacuum," Dr. Rhee told audience members. "Baseline" technology in ophthalmology practices should include the slit lamp, some lenses, a gonio prism, an automated perimeter, a pachymeter, and optic nerve imaging capability, he said.

"These have been around for a long time and are the standard of care for most practitioners," Dr. Rhee said.

Other technology, however-such as confocal scanning laser ophthalmoscopy (CSLO), nerve fiber layer imaging devices capable of scanning laser polarimetry (SLP) or optical coherence tomography (OCT), and some anterior segment imaging technologies, including ultrasound biomicroscopy and anterior segment OCT-do not yet have absolute sensitivity and specificity, he said.

"They're not quite like a pregnancy test at this point, where they're all 'yes' or all 'no,' " Dr. Rhee told Ophthalmology Times.

Research has found, for instance, that CSLO has 84% to 90% sensitivity and 81% to 96% specificity, SLP has 87% to 91% sensitivity and 86% to 95% specificity, and OCT has 67% to 86% sensitivity and 83% to 90% specificity, he noted in his presentation.

"They're very good," Dr. Rhee told attendees, "but they are not 100%. In other words, you are not going to be replaced by any of these technologies . . . . You are still the key. These [devices] are simply just aids to you."

He said that he owns all of these types of technology and uses them in his practice but pointed out, "There is no form of glaucoma that can only be diagnosed by one of these technologies."

Research has demonstrated that angles are narrower when viewed via anterior segment imaging than on gonioscopy, Dr. Rhee said, but he added, "I don't think we're having a rash of acute angle-closure glaucomas that we're missing. We're catching these on gonioscopy."

Progression

"With regard to progression, expensive toys have not yet reduced their variability to the point where significant clinical intervention is decided on by anything other than IOP, visual field, or optic nerve," Dr. Rhee said, noting that those parameters can be assessed using the baseline technology he described as being part of every ophthalmology practice. When he asked audience members to indicate how many, in the absence of changes in the visual field, optic nerve, or IOP, would perform surgery based on changes found via CSLO, SLP, or OCT, nobody raised a hand.

"Expensive toys can be very helpful, and I certainly think that they have a role . . . in trying to [determine] early glaucoma or pre-perimetric glaucoma," he told attendees. Also, Dr. Rhee told Ophthalmology Times, advanced technologies can be useful when a patient cannot reliably take a visual field test. "If they can sit still for just a couple minutes, you can get a structural imaging test that can be extremely helpful in helping the practitioner determine whether or not there's glaucomatous damage," he said.

"But you, the clinician, are still the most important thing. These expensive technologies are simply just an aid to help you," Dr. Rhee concluded to his colleagues.

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