Integration of a spectral domain optical coherence tomography system into a surgical microscope for intraoperative imaging

Abstract

Purpose: To demonstrate an operating microscope-mounted spectral domain optical coherence tomography (MMOCT) system for human retinal and model surgery imaging.

Methods: A prototype MMOCT system was developed to interface directly with an ophthalmic surgical microscope, to allow SDOCT imaging during surgical viewing. Nonoperative MMOCT imaging was performed in an Institutional Review Board-approved protocol in four healthy volunteers. The effect of surgical instrument materials on MMOCT imaging was evaluated while performing retinal surface, intraretinal, and subretinal maneuvers in cadaveric porcine eyes. The instruments included forceps, metallic and polyamide subretinal needles, and soft silicone-tipped instruments, with and without diamond dusting.

Results: High-resolution images of the human retina were successfully obtained with the MMOCT system. The optical properties of surgical instruments affected the visualization of the instrument and the underlying retina. Metallic instruments (e.g., forceps and needles) showed high reflectivity with total shadowing below the instrument. Polyamide material had a moderate reflectivity with subtotal shadowing. Silicone instrumentation showed moderate reflectivity with minimal shadowing. Summed voxel projection MMOCT images provided clear visualization of the instruments, whereas the B-scans from the volume revealed details of the interactions between the tissues and the instrumentation (e.g., subretinal space cannulation, retinal elevation, or retinal holes).

Conclusions: High-quality retinal imaging is feasible with an MMOCT system. Intraoperative imaging with model eyes provides high-resolution depth information including visualization of the instrument and intraoperative tissue manipulation. This study demonstrates a key component of an interactive platform that could provide enhanced information for the vitreoretinal surgeon.

Figure 1.

(A) Illustration of the MMOCT prototype and (B) photograph of the operating microscope and MMOCT system (red box). Surgical manipulations are being performed on cadaveric porcine eye.

Figure 2.

MMOCT B-scan through the fovea (A) and the optic nerve (B) in eyes of health human volunteers.

Figure 3.

MMOCT scans of surgical instruments. (A) MMOCT SVP image of an MVR blade. (B) MMOCT B-scan of the MVR blade shows total shadowing under the metallic instrument (arrow). The tip of the instrument is seen as a hyperreflective signal at the leading edge of the shadow (arrowhead). (C) MMOCT SVP of forceps resting on the retinal surface. (D) MMOCT B-scan with forceps resting on retinal surface. Near total shadowing is seen underneath the instrument tip (arrow). Compression of the retinal tissues is seen at the area of the tip.

Figure 4.

MMOCT scans of surgical instruments. (A) MMOCT SVP image of a silicone soft-tip. (B) MMOCT B-scan of silicone soft-tip on the retinal surface shows moderate reflectivity and minimal shadowing at tip. Total shadowing from the metallic handle is visible at the left of the image. (C) MMOCT SVP of diamond-dusted membrane scraper. (D) MMOCT B-scan of diamond-dusted membrane scraper on the retinal surface. Minimal shadowing and moderate reflectivity are caused by the posterior silicone-only portion of the tip. Increased shadowing and hyperreflectivity appear in the area of the diamond-dusted tip. (E) MMOCT 3-D reconstruction of the diamond-dusted membrane scraper with hyperreflectivity in the area of the diamond dust. The silicone portion appears to be moderately reflective. Total shadowing is noted posterior to the silicone portion, secondary to the instrument handle.

Figure 5.

MMOCT scans of a metallic subretinal needle. MMOCT (A) SVP image and (B) B-scan of the subretinal needle above the retina before retinal vein cannulation. The subretinal needle is highly reflective (arrow), with total shadowing appearing beneath the needle tip. Retinal compression secondary to the vitreous is seen just in front of the needle. MMOCT (C) SVP and (D) B-scan of a subretinal needle (arrow) penetrating the subretinal space during attempted cannulation. Significant shadowing is seen below the needle. MMOCT (E) SVP and (F) B-scan of subretinal needle (arrow) successfully cannulating the retinal vein. Significant shadowing is noted below the needle.

Figure 6.

MMOCT scans showing tissue effects from operative maneuvers. (A) MMOCT SVP image showing a retinal hole with forceps grasping tissue in another area. (B) MMOCT B-scan of full-thickness retinal hole after grasping of retinal tissue with metallic forceps. (C) MMOCT SVP of scrolled retina and retinal elevation after penetration of the retinal surface with the silicone-tipped instrument. (D) MMOCT B-scan of corresponding area with silicone tip embedded in retinal tissue. (E) MMOCT 3-D reconstruction of retinal traction (green) from subretinal needle after injection of subretinal fluid (blue). Red: attached retina. (F) MMOCT SVP of corresponding area with visualization of the subretinal needle and associated area of subretinal fluid (arrow).