diagnostic instruments
A New Kind of Gonioscopy Lens
A different design offers a unique view of angle details and a 360° view.

Gonioscopy should be performed on all individuals with glaucoma as well as all glaucoma suspects. It is also necessary in the care of patients with angle deformities, previous anterior uveitis, and those with unusual iris nodules or vasculature.

Now that every TPA-certified optometrist in the United States can legally use topical anesthetics in his or her practice, gonioscopy should be included in the list of tests necessary to diagnose and manage a wide variety of anterior segment ocular diseases.

	1. A three-mirror lens allows evaluation of the angle, mid- and peripheral retina.
	2. A four-mirror gonioscopic lens does not require gonioscopic fluid.
	3. The new 360° lens can be used for diagnosis and therapeutic applications. PHOTO CREDITS: MAT JOHNSON AND SYLVIA JONES.

Traditional lenses

Hand-held single-mirror, three-mirror, and four-mirror gonioscopic lenses have been the standard of care for many years. A standard Goldmann-style, single-mirror, gonioscopy lens has a 62° mirror, which must be rotated into all quadrants to view the entire circumference of the angle.

Another popular gonioscopic lens has three mirrors angled at 59°, 67°, and 73° to allow for evaluation of the angle, midperipheral retina, and peripheral retina (see image 1). With either lens designs, the lens must be rotated on the eye to view 360-degrees of the angle.

The four-mirror lens design has many advantages over the single and three-mirror versions. Because it doesn't need to be rotated on the eye, the procedure takes less time and does not require gonioscopic fluid (see image 2). And, four-mirror lenses are preferred in children and in patients with small or tight palpebral fissures because they are smaller.

However, because no suction is created between the cornea and the lens, the technique may be initially more difficult to master.

A new view

The new Volk 360 design provides clear angle details and 1.5 times magnification (see image 3, page 26). It affords a unique view of all angle structures simultaneously, which provides a panoramic view that far exceeds that achieved with standard three- or four-mirror lenses.

It requires no gonioscopic fluid (although I prefer to use one drop). It can be used with both standard slit-lamp illumination for diagnostic purposes and with laser light energy for therapeutic applications.

Table 1 (page 24) compares the Volk 360° with other gonioscopic lenses offered by the company. It shows that the new Volk 360� is the longest, widest and heaviest goniolens made by Volk Optical.

There are some drawbacks to the new lens. With certain slit lamps, the patient's face plane may be too close to the examiner to permit in-focus images; therefore an auxiliary forehead-rest cushion must be employed. (These are available from the manufacturer.) Another potential disadvantage is that the entire 360� view is lost when using higher magnifications.

However, overall I found the optics of this lens to be excellent and the "right-side-up" view with low magnification spectacular. It also makes the appreciation of the anterior chamber angle's beauty easy to demonstrate to my students.

The author has no financial interest in, and is not a paid consultant of, Volk Optical, Inc. However, he gratefully acknowledges the loan of their new gonioscopic 360� lens for his clinical evaluation.

ROBERT D. NEWCOMB, O.D., IS PROFESSOR OF CLINICAL OPTOMETRY AND ALSO SERVES AS CHAIR FOR THE ADVANCEMENT OF PROFESSIONAL PRACTICE FOR THE VISION SERVICE PLAN (VSP) AT THE OHIO STATE UNIVERSITY COLLEGE OF OPTOMETRY .