Abstract
Purpose :
Tilted and torted optic discs are a morphologic feature associated with myopia. Optic disc tilt has been defined as a ratio of more than 1.30 between the longest and shortest disc diameter. The classical tilted optic disc orientation is inferonasal. It was the purpose to characterise the tilt of the optic disc and study its parapapillary and ocular correlates.
Methods :
The study included 104 eyes of 52 myopes ( 32 females). Subjects less than 10 years were excluded. All myopes with classically tilted disc that show a superior origin of blood vessels with an inferior parapapillary atrophy were included. An ophthalmic evaluation, included biometry, fundus photography and SD-OCT. Tilt of the disc was measured by drawing the longest and shortest diameters of the optic disc and the torsion was measured as the angle between a line perpendicular to the horizontal and the longest diameter of the disc. Torsion was present when the angle was more than 15 degrees. The angle between a horizontal line passing through the center of optic disc and a line from the maximum extent of the PPA inferiorly, to the center of the disc was considered as a presumed extent of rotation in a classical tilted disc.
Results :
The mean age was 33.00±13.29 yrs, BCVA was 0.64±0.25 in decimal units, axial length was 25.80±1.50mm. and IOP was 15.24±2.09mmHg. Cylinder on AR was -1.937±1.13D, Horizontal and vertical K readings were 43.95±1.76D and 45.06±1.76D respectively. Peripapillary atrophy ( PPA) was present in all eyes. The Longest axis disc diameter was 1.82±0.29mm, shortest axis diameter was 1.457±0.28 mm. and the disc ovality/tilt ratio was 1.28±0.21. Torsion was 44.64±33.29 degrees and angle of rotation was 102±43.93 deg. The tilt ratio was significantly correlated with torsion (P=0.004;r=0.305), rotation (P=0.001;r=0.353), maximum width of the PPA (P=0.045;r=0.218), Gamma zone width (P=0.016;r=0.260) and staphyloma involving the disc (P=0.059;r=0.206).
Conclusions :
The disc ovality ratio in the classical tilted disc has a significant association with several other optic disc and parapapillary parameters, including torsion, rotation, PPA and Gamma zone. These parameters may constitute a constellation of signs associated with the tilted disc, and enable us to understand this condition better.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.