Abstract
Purpose :
To investigate effect on head tilt on tube position of Ahmed glaucoma valve (AGV) using anterior segment optical coherence tomography (AS-OCT) in glaucoma patients.
Methods :
This prospective study included twenty-six eyes of 24 patients who underwent AGV implantation. Tube-cornea distance (TCD), tube-cornea angle (TCA) and intracameral tube length (TL) were measured from the scans obtained using AS-OCT in three different head positions: neutral, 30° lateral head tilt and 30° medial head tilt. Gonioscopy was also performed to assess the location of the tube in the angle. Endothelial cell density (ECD) and coefficient of variation were measured using specular microscopy after surgery.
Results :
The mean TCD decreased from 0.91 ± 0.48 mm to 0.88 ± 0.47 mm and 0.87 ± 0.47 mm when the head position was changed from neutral to medial and lateral head tilt positions side head tilt (both, p<0.05). During the same alteration of head positions, the mean TCA and TL also showed a decrease (TCA: 31.22±6.74° to 30.10±7.13° (lateral tilt) and 30.80±7.20° (medial tilt), both p<0.05; TL: 3.07±0.94 mm to 3.01±0.95 mm (lateral tilt) and 3.00 ± 0.97 mm (medial tilt), both p<0.05). Mean central corneal ECD significantly decreased after surgery (p=0.001), but no association was found between the amount of ECD decrease and the head position-induced changes in tube position. However, the eyes with tube entry anterior to Schwalbe’s line showed a difference in ECD between superotemporal and central cornea after surgery compared to those with tube more posteriorly located (-35.5±553.6 cell/mm2 vs -990.4±543.1 cell/mm2, p=0.001).
Conclusions :
Mild alterations of head positions induced changes in intracameral tube position of glaucoma drainage implants. However, further studies are needed to address the question whether a greater range of positional alterations leads to changes in tube positions which may significantly affect the corneal endothelial cells.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.