Ocular imaging innovations enhance diagnosis, treatment of anterior segment disease

OCT, VHF ultrasound and ultrasound biomicroscopy enable the visualization of various structures for a wide range of indications.

Anterior segment imaging proved effective in the evaluation and treatment of ocular pathology and trauma in a recent study.

Used alone or in combination, three technologies facilitated preoperative assessment, tracking of disease progression and screening of candidates for refractive surgery, Roxana Ursea, MD, said.

Dr. Ursea assessed very high-frequency (VHF) ultrasound (Artemis, ArcScan), anterior segment optical coherence tomography (Visante, Carl Zeiss Meditec), and high-resolution ultrasound biomicroscopy (Quantel and VuMax, Sonomed).

The most significant finding from the study was the effective postoperative evaluation of visual complications or poor visual outcomes in patients undergoing refractive surgery, Dr. Ursea said.

“The most interesting finding would be in post-refractive patients in which there are complications or poor vision for no obvious reasons,” she said. “[Artemis] can show you irregularities or striae within the flaps or the depth of scars or haze that cannot be assessed with the standard available technologies.”

Dr. Ursea presented her findings at the American Society of Cataract and Refractive Surgery meeting in Boston.

Study design and indications

Primary indications for high-resolution ultrasound biomicroscopy (UBM) were visualization of anterior chamber structures, posterior iris or ciliary body; assessment of IOL position; preoperative assessment of eyes with hypotony or trauma; poor visualization of the posterior segment; and follow-up of documented abnormalities.

Indications for anterior segment OCT (AS-OCT) were assessment of angle, measurement of corneal thickness, visualization of the anterior iris and preoperative assessment.

The predominant indication for VHF ultrasound was postoperative assessment in refractive surgery cases.

The retrospective, noncomparative study included 65 eyes of 65 patients with various anterior segment pathologies. Mean patient age was 30.5 years (range: 8 to 77 years). The study group included 36 men and 29 women.

Patients were placed into a supine position and administered topical anesthesia. Dr. Ursea used a 21-mm cylindrical eye cup, with balanced salt solution as a contact medium. Radial and longitudinal scans were performed hourly.

Abnormalities were found in 61 eyes, including iris or ciliary body masses, anterior scleritis, pseudophakia, intermediate uveitis, traumatic hyphema and intraocular foreign bodies.

Corneal pathology identified in 34 eyes included keratoconus, corneal edema, corneal scarring, keratitis and Salzmann’s nodules.

UBM and AS-OCT findings correlated with clinical exam results in most cases, Dr. Ursea said.

Corneal mapping and iris imaging

VHF ultrasound was effective in preoperative and postoperative corneal assessment in candidates for refractive surgery, Dr. Ursea said.

“The beauty of the Artemis is that it provides mapping of different corneal layers, like epithelial mapping for post-refractive patients, and much more detail on the order of microns that neither of the other devices is able to visualize,” she said.

Preoperative corneal mapping was effective in identifying frank keratoconus, a contraindication for LASIK, Dr. Ursea said.

“You don’t want to take the risk in those patients,” she said. “Artemis can tell you with a very high precision and reliability if the patient is a good candidate or not.”

Both AS-OCT and UBM were used in assessing anterior chamber depth, corneal and angle measurements.

“Both of them are useful techniques,” Dr. Ursea said, giving the edge to ultrasound biomicroscopy. “It gives you angle-to-angle, white-to-white measurements.”

Dr. Ursea found that UBM also provided better imaging and more depth behind the iris plane than AS-OCT.

“The penetration of the image provided by UBM is increased vs. AS-OCT,” she said. “It can visualize structures posterior to the iris plane, like the ciliary body. So, the UBM would be the gold standard, I would say, and the instrument of choice if you have a patient with a suspicion of iris tumor, with or without ciliary body involvement.”

Trauma, haze and glaucoma

Dr. Ursea recommended AS-OCT for assessing ocular trauma.

“It’s a little bit tricky using UBM in trauma patients, especially if it involves a ruptured globe,” she said. UBM requires use of balanced salt solution as a contact medium between the transducer and the eye. AS-OCT is better suited for assessing trauma, she said, as it involves a noncontact method.

“That’s why, in case of trauma, if you want to visualize the anterior segment, probably the Visante AS-OCT would be better, especially very recent trauma,” Dr. Ursea said. “It involves a noncontact technique. So, in trauma cases, there is no risk of infection or no risk of pressure on the globe of any kind. And it can give you detailed images up through the iris plane.”

In addition to assessing trauma, AS-OCT was suited for evaluating visual disturbances or corneal haze, Dr. Ursea said.

OCT is also effective in visualizing features associated with glaucoma, such as narrow angle.

“In patients with narrow angle, the anterior segment OCT allows you a precise, exact measurement of the degrees of angle, but it also gives you a three-dimensional measurement, ‘the angle volume,’” Dr. Ursea said.

Just as clinicians are gradually using OCT more often in the front of the eye, it would be helpful if ultrasound migrated from the front of the eye to the back; ultrasound would further enhance retinal imaging in the assessment of age-related macular degeneration, she said. – by Matt Hasson

• Roxana Ursea, MD, can be reached at Department of Ophthalmology, University of Arizona, 655 N. Alvernon Way, Suite 108, Tucson, AZ 85711-1824; 520-322-3800, ext. 204; fax: 510-321-3665; e-mail: rursea@eyes.arizona.edu.

The usefulness of UBM and OCT is well demonstrated in the presentation with abundant clinical examples that show intraocular structures that are otherwise invisible, due to the anatomy or pathology that is present. Each of the technologies has its own advantages and disadvantages but together they provide complementary information.

The OCT is fast and convenient in its non-contact view of anterior segment and angle and enables higher image resolution than UBM, which provide a comprehensive view of the anterior and some posterior segment structures. However, its limitation is that it requires an experienced operator with contact application and a water bath. Artemis gives a useful and detailed view of the corneal anatomy in the required detail necessary after laser vision correction.

Much benefit is derived from serial inspection of progressive pathology giving a perspective that tracks the need for surgery. The presentation usefully provides an update on these important facilities and their specific applications.

– Noel A. Alpins, MD
OSN Refractive Surgery Board Member