These images were performed with the
RTVue FD-OCT (Optovue, Fremont, CA) with the corneal adaptor module (anterior segment camera) attachment.
Case 1
This patient is a 79 year old female with primary open angle glaucoma who underwent glaucoma aqueous tube shunt (Baerveldt 350, AMO, Santa Ana CA) 2 years prior. The tube shunt was performed due to medically uncontrolled IOP with a history of prior failed trabeculectomy approximately 10 years ago and scarred conjunctiva. The patient had IOP controlled in the 14 to 16 mmHg range with adjunctive dorzolamide-timolol fixed combination drops twice a day.
She began to develop corneal edema superiorly, and the possibility of tube corneal touch was investigated with the ASOCT. Clinically, on slit lamp exam, there was no corneal touch with the central portion of the tube, but there was a question of peripheral contact. Figure 1 shows the tube entering into the anterior chamber just anterior to the corneal scleral junction and disrupting the corneal endothelium at the entry site (white arrow).
Figure 1
A diagnosis of corneal decompensation due to peripheral tube-corneal touch was made. A surgical revision was performed with tube repositioned more posteriorly.
Case 2
This patient is a 29 year old male with congenital glaucoma who had a Baerveldt 350 implant superotemporally 15 years ago. He underwent a second Baerveldt 350 in the superonasal quadrant 3 months ago at another institution and came to the Doheny Eye Institute for a second opinion regarding decreased vision. On exam, he had corneal edema with central tube corneal touch in the superonasal tube. This was revised surgically and repositioned more posteriorly. On subsequent exams, the superotemporal tube was noted to be close to the cornea peripherally with some opacification over the entry site (see Figure 2). The possibility of peripheral tube-corneal touch was investigated with ASOCT imaging.
Figure 2
Figure 3 shows the ASOCT image with the tube entry site just posterior to the corneal scleral junction (arrow). There is a fibrous membrane (asterix) from the tube to the corneal endothelium that accounts for the opacity seen on slit lamp examination. This effectively ruled out corneal tube contact, and no further surgery was performed.
Figure 3
Discussion
These cases represent the utility of anterior segment OCT in clinical decision making in glaucoma. Both of these patients had glaucoma aqueous tube shunts that were possibly contributing to corneal decompensation due to peripheral tube corneal touch at the entry site. By slit lamp examination the tube positioning was indeterminate and was indistinguishable between the two cases. However, by ASOCT, we were able to determine that the first case indeed had an entry site that was too anterior and required surgical intervention. Just as importantly, in case two we were able to rule this out and prevent the patient from unnecessary surgery.
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