Purpose
To evaluate the relationship between tiling value around the optic disc and visual field loss in normal tension glaucoma (NTG).
Methods
This is a retrospective observational-investigation. Eighty eyes of 47 patients diagnosed as NTG without any other ophthalmic diseases or surgical histories were enrolled. The high penetration OCT (DRI-OCT1, Topcon, Japan) was used for imaging the optic disc. Four-mm diameter circle scan OCT image around the optic disc was extracted from the 3D OCT volume image and then image was divided into the 24 clock hour sectors. To quantify the disc tilting, peripapillary tilting index (PTI; pixel) which was the deference in RPE height between one sector and its counterpart sector was evaluated by using a custom-designed software program. The ± degree between the tilting line with maximal PTI and the horizontal line of the optic disc was named the tilting degree. Mean deviation (MD,db), mean central threshold value of 4 points within 5 degree (MCTV,db) of visual field were evaluated by Swedish interactive threshold algorithm standard 30-2 test. Axial length (AL,mm) was measured by IOL master. Tukey-Kramer’s multiple comparison test was used for statistical comparisons. Differences test for multiple comparisons were judged statically significant at P<0.05.
Results
Eighteen eyes (22.5%) were superiorly tilted disc and 62 eyes (77.5%) were inferiorly. Mean maximal tilting degree was (-15.1±14.2°); 31 eyes of -7.5°, 19 eyes of -22.5°, 11 eyes of +7.5°and 19 eyes of others. Among three group (-7.5°,-22.5°and +7.5°), age (60.7±14.7, 55.7±14.6, 62.6±12.7)y.o. and AL (25.87±1.70, 26.21±1.69, 25.83±2.37) were no significant differences, whereas maximal PTI was significant differences between -7.5°and +7.5°(1155±545 vs 728±390, P<0.05) and MD was significant differences between -7.5°and -22.5°(-11.5±7.6 vs -6.5±5.4, P<0.05). Eighteen eyes of 19 eyes (94.7%) with MCTV under 20db among three group were tilting within±7.5°.
Conclusions
The optic disc of NTG patients with a severe central visual field loss tends to be temporally tilted.
Keywords: 550 imaging/image analysis: clinical •
627 optic disc •
758 visual fields