I(inetic Ultrasound Evaluation of the Posterior Vitreoretinal Interface YALE L. FISHER, MD, JASON S. SLAKTER, MD, ROBERT A. FRIEDMAN, MD, LA WRENCE A. YANNUZZI, MD

Abstract: The evaluation of the posterior vitreoretinal interface is important in the study of the natural course and preoperative evaluation of numerous disorders of the retina. The exact status of the posterior vitreous cannot always be reliably determined by ophthalmoscopic examination. The diagnostic value of kinetic contact ultrasonography was investigated to evaluate the status of the posterior vitreous in 70 eyes with clear ocular media. Contact B-scan ultrasound provided an extremely accurate method for evaluating the posterior vitreoretinal interface in 69 of the 70 eyes in this study, when compared with all conventional clinical means of examination including slit-lamp biomicroscopy with the Goldmann contact lens and fundus photography with the EI BayadiKajiura lens. Contact B-scan ultrasonography is an important diagnostic adjunct in determining the status of the vitreoretinal interface. Ophthalmology 1991; 98: 1135-1138

The evaluation of the posterior vitreoretinal interface is important in the study of the natural course and preoperative analysis of numerous disorders involving the macula as well as the more peripheral retina. In clear media, current techniques for evaluation of the posterior vitreoretinal interface include indirect ophthalmoscopy, slitlamp biomicroscopy, and photography with the EI BayadiKajiura lens. These methods of examination often are limited by poor visual resolution of the vitreoretinal interface, particularly in the retinal periphery. Furthermore, in eyes with opaque media, biomicroscopic examination and photography are not possible. Posterior vitreous face separation has been observed and reported using immersion ("water bath") ultrasound techniques. 1,2 Resolution of the separated vitreous by

contact ultrasonography has been erratic and difficult with older equipment primarily because of display screen flicker and poor image quality. Within the limits of resolution, state-of-the-art, high-gain contact B-scan ultrasonography with improved electronic imaging and fusedimage real-time display is capable of imaging the posterior vitreous face after complete or incomplete detachment in clear or opaque media eyes. This report describes a masked comparison of contact ultrasound to biomicroscopic examination techniques in establishing the position of the posterior vitreous face in 70 clear media eyes.

MATERIALS AND METHODS EQUIPMENT

Originally received: March 19, 1990. Revision accepted: February 28, 1991 . From the Manhattan Eye, Ear and Throat Hospital, New York. Presented as a poster at the American Academy of Ophthalmology Annual Meeting. Las Vegas. October 1988. Supported by a grant from the Macula Foundation . New York. New York. Reprint requests to Yale L. Fisher. MD. 519 E 72nd St. Suite 203. New York. NY 10021.

Ultrasound devices. Two fused-image, high-gain, realtime ultrasound devices were used-Alcon Digital B 2000 (Fort Worth, TX) and the Alcon-Biophysic Ophthascan S (Fort Worth, TX). Documentation was performed by videotape recording and Polaroid still photography. Visual devices. A standard slit-lamp biomicroscope was used with the Goldmann three-mirror contact lens. A Nikon (Torrance, CA) slit-lamp biomicroscope/camera was used with the EI Bayadi-Kajiura lens. 1135

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Table 1. Visual Confirmation of Posterior Vitreous Face Status Visual Confirmation Ultrasound Evaluation Results

EI Bayadi-Kajiura + Contact Lens

EI Bayadi-Kajiura Only

Contact Lens Only

PVD (27) No PVD (43) Total

23 35 58

3 4 7

3 4

PVD

=

1

No Visual Confirmation

0 1 1

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macular region was detached. The results were recorded in a masked fashion and compared after completion of the entire study. As no histopathologic determination of the exact status of the posterior vitreous face could be performed, Cohen's kappa statistic was used to evaluate interrater agreement. 3 A value of kappa (K) greater than 0.75 is considered excellent agreement, a value between 0.4 and 0.75 is considered fair-to-good agreement, and a value less than 0.4 is considered poor agreement. 3

posterior vitreous detachment.

RESULTS

Table 2. Cohen's Kappa Values'

EI 8ayadi-Kajiura Contact lens

Ultrasound

EI 8ayadi-Kajiura

0.852 (0.728-0.976) 0.762 (0.607-0.917)

0.634 (0.504-0.852)

• Values in parentheses represent 95% confidence intervals for the value kappa.

TECHNIQUE

Ultrasound. Standard "through-the-lid" contact ultrasound technique was used. Coronal probe examining positions were chosen to avoid lens-induced artifacts. Tilting motions permitted systematic sequential examination of each globe from superior, temporal, inferior, and nasal coronal probe positions. Movement of the vitreous face was evaluated during directed voluntary motion of the patient's globe while the probe was held stationary (kinetic examination). Visual examination. All patients were fully dilated before visual examination. Topical anesthesia was used for contact lens examination. Goldmann contact lens examination was performed from anterior-to-posterior centrally, followed by evaluation of the periphery using the side mirrors. El Bayadi-Kajiura Lens examination was performed similarly in an anterior-to-posterior fashion. Command voluntary motions were used to permit maximal visualization of the posterior vitreous face for both visual techniques. PATIENTS

Thirty-five randomly selected patients (70 eyes) were examined by contact lens technique by one author (RF), by El Bayadi-Kajiura fundus slit-lamp/photography by a second author (JS), and by contact B-scan ultrasonography by a third author (YF). As the El Bayadi-Kajiura lens does not permit examination of the peripheral retina, attention was directed toward the presence or absence of posterior vitreous separation at the optic nerve head and macular region. A partial separation of the vitreous face was classified as a posterior vitreous detachment if the 1136



Contact B-scan ultrasound examination identified a posterior vitreous detachment at the optic nerve head and macular region in 27 eyes, with no posterior vitreous separation noted in the remaining 43 eyes. These observations were confirmed by both visual means in 58 of 70 eyes (83%). One of the visual techniques supported the ultrasound findings in 11 of70 eyes (16%). Table 1 depicts the breakdown of the visual techniques that confirm the status of the posterior vitreous face as determined by ultrasonography. The agreement between the results of the ultrasound examination and either of the visual methods was excellent as measured by Cohen's kappa statistic, with agreement highest between the El Bayadi-Kajiura lens and ultrasound examination techniques (Table 2). The agreement between the two visual methods was 0.63, which is in the fair-to-good range. In 8 of the 11 cases where one visual technique did not agree with the results of the remaining two observers, both examiners using visual techniques reported the presence of "debris" in the vitreous cavity. This debris was interpreted as visual "evidence" of a posterior vitreous separation by one examiner, while being considered cortical vitreous condensation by the other. In only one case did the two visual techniques identify a posterior vitreous detachment that was not observed by the ultrasound examination. In this case, the detachment was noted to be less than 0.5 mm in height from the surface of the fovea, which is below the axial resolution of the B-scan instruments.

DISCUSSION The slit-lamp biomicroscope and the Goldmann contact lens are the standard instruments used for examination of the posterior vitreoretinal interface, which is best seen at the optic nerve head through the central portion of the contact lens.4,5 Peripheral examination is possible but more difficult using the mirrors of the lens. Documentation and standardization of the results ofa clinical examination are not easily accomplished or confirmed by independent viewers. The use of the El Bayadi-Kajiura lens coupled with slit-lamp biomicroscopy/photography permits documentation of the vitreoretinal architec-

FISHER et al



POSTERIOR VITREORETINAL INTERFACE

Fig I. High-gain ultrasound images of the same eye demonstrate a total posterior vitreous detachment. Notice the curvilinear line representing the posterior vitreous face which changes position with eye movement. A, upgaze; B, downgaze; C, gaze directed centrally.

ture. 5- 7 This technique, however, does not allow for evaluation of the peripheral vitreoretinal interface. With both visual techniques, clear ocular media, fairly wide pupillary dilatation, and patient cooperation are critical for proper examination. The presence of optically resolvable tissue

interfaces is necessary for the determination of the status of the posterior vitreous face. As noted, debris visualized in the vitreous cavity may be misinterpreted by the observer as evidence of a posterior vitreous separation. Conversely, a true vitreous separation may be overlooked if the posterior vitreous face is fully transparent. Current B-scan ultrasound equipment is capable of fused, real-time, high-gain, electronically improved imaging, permitting display of subtle acoustical impedance mismatch. With such improvements, clear media cortical vitreous structure is visible at high gain. After posterior vitreous separation, the interface between formed vitreous and preretinal liquid vitreous becomes ultrasonically visible as a fine, low-intensity line concave to the retinal surface (Figs lA, B, C). During kinetic scanning (directed voluntary movement of the globe), the mobility and extent of the separation can be assessed and vitreoretinal interface mapping is possible. The usefulness of ultrasound is limited, to some extent, by the experience of the examiner, who must be properly trained in the technique of contact uhrasonography, as well as by the lack of precise landmarks other than the optic nerve head and the insertion sites of the extraocular muscles. In addition, resolution limitations of 0.5 mm axially and 1.5 to 2.0 mm laterally must be considered. In this study, the results of the ultrasound examination were supported by both clinical examination and photography in 83% of cases, and by one of these visual techniques in 16% of the cases. In only one case was the ultrasound evaluation in disagreement with both visual techniques. In this case, the posterior vitreous separation in the macular region was below the limits of axial resolution of the ultrasound units. The presence of epiretinal membranes or material elevated less than 0.5 mm from the surface of the retina could not be detected by ultrasound. No pathologic confirmation of the results were possible in this study. While histopathology represents the most accurate means of determining the reliability of ultrasonic assessment of the vitreous face, the design of this study is a reasonable clinical alternative. The results of the ultrasound examination demonstrate an excellent agreement wfth the visual techniques as measured by Cohen's kappa statistic, indicating that ultrasonography should play a major role in the evaluation of the posterior vitreous face. In clear media situations, the ability to observe the mobility of a large segment of the vitreous cavity in real-time is a major advantage of ultrasound examination in determining the mobility and position of the posterior vitreoretinal interface. Relying on acoustic impedance mismatch rather than optical visualization, ultrasound provides a relatively easy appreciation of cortical vitreous structure to the experienced examiner. Rapidity of examination, high patient acceptance, minimal cooperation requirements, and an absence of the need for dilation are additional advantages. Furthermore, the results are readily documented by videotape. Polaroid photography is limited by poor gray scale and resolution and by the lack of real-time imaging. 1137

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Improvements in ultrasound imaging coupled with thorough examination techniques appear to be of value in establishing the position of the formed vitreoretinal interface at the optic nerve, macular region, and peripheral portion of the retina. Ultrasonically determined vitreous architectural maps may prove useful in studying, standardizing, and documenting the natural course of many retinal diseases that involve formed vitreous traction as part of their pathogenesis.

REFERENCES 1. Coleman OJ, Franzen LA. Vitreous surgery: preoperative evaluation and prognostic value of ultrasonic display of vitreous hemorrhage. Arch Ophthalmol 1974: 92:375-81.

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2. Jalkh AE, Avila MP, EI-Markabi H, et al Immersion A- and B-scan ultrasonography: its use in preoperative evaluation of diabetic vitreous hemorrhage. Arch Ophthalmol1984: 102:686-90. 3. Fleiss JL. Statistical Methods of Rates and Proportions, 2nd ed. New York: John Wiley and Sons, 1981; 212-25. 4. Toletino FL, Schepens CL, Freeman HM. Vitreoretinal Disorders: Diagnosis and Management. Philadelphia: WB Saunders, 1976; 71108. 5. Jalkh AE, Trempe CL. Clinical methods of vitreous examination. In: Schepens CL, Neetens A, eds. The Vitreous and Vitreoretinallnterface. New York: Springer-Verlag, 1987; 73-83. 6. Kajiura M, Takahashi M, Takahashi F. Uehara M. Use of an aspherical convex lens for slit-lamp funduscopy. Rinsho Ganko 1977; 31 :1399403. 7. Takahashi M, Trempe CL, Schepens CL. Biomicroscopic evaluation and photography of posterior vitreous detachement. Arch Ophthalmol 1980; 98:665-8.

Kinetic ultrasound evaluation of the posterior vitreoretinal interface.

The evaluation of the posterior vitreoretinal interface is important in the study of the natural course and preoperative evaluation of numerous disord...
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