Relationship of shallow optic cup and small disc with non-arteritic anterior ischemic optic nerupathy

Abstract

Objective To observe the relationship between shallow optic cup. small disc and occurrence in patients with non-arteritic anterior ischemic optic neuropathy (NAION). Methods Ninety-six patients(96 diseased eyes) who accorded with the diagnosis criteria for NAION, with duration ≥ three months and optic disc edema in paracmasis were selected. The fellow eyes of 96 NAION patients and 80 normal eyes were selected in our study. The horizontal and vertical disc and cup diameters,optic cup depth,and peripapillary retinal nerve fiber layer (RNFL) thickness were measured by cross and ring scan of optical coherence tomography (OCT, Humphrey 2000,German Carl Zeiss Company) inspection system. The cup depth were classified four grades by cup shape according to OCT images:Grade Ⅰ,bottom of optic cup above the anterior plane of peripapillary neuroepithelial layer(PNL);Grade Ⅱ ,bottom of optic cup above the plane of PNL; Gr adeⅢ,bottom of optic cup between the plane of PNL and choroidal pigment epithelium; Grade Ⅳ,bottom of optic cup under the plane of choroidal pigment epithelium connection. The grades of optic cup and value in three groups were statistically analyzed. The follow-up ranged from six months to three years. Results The disc diameter in horizontal scanning of diseased eyes, fellow eyes and normal eyes were (1.29±0. 19), (1.32 ± 0. 17), (1.40±0. 15) mm,and diameters in vertical scanning were (1.52± 0.14), (1.49±0.17), (1. 60±0. 22) mm, respectively. Compared the diseased eyes and fellow eyes with normal eyes,the difference were statistically significant in horizontal scanning (t = 4. 291,3. 315; P 0. 05). Of the diseased eyes, Grade Ⅰ optic cup in 36 eyes(37. 50), Grade Ⅱ-Ⅲ optic cup in 52 eyes(54. 17%),Grade IV optic cup in eight eyes(8. 33%),and Grade Ⅰ-Ⅲ optic cup in 88 eyes(91. 67%) were found. Of the fellow eyes,Grade I optic cup in 18 eyes(18. 75%),Grade Ⅱ-Ⅲ optic cup in 69 eyes (71. 88%), Grade IV optic cup in nine eyes (9. 34%) ,and Grade Ⅰ-Ⅲ optic cup in 87 eyes (90. 66 %) were found. Compared the average RNFL thickness of diseased eyes with the fellow eyes and normal eyes, the differences were statistically significant in temporal, upper, nasal, lower quadrant (t = 12. 862, 10. 147, 15.046,8. 180,12. 859,9. 562,12. 174, 8. 632; P 0. 05). During the follow-up, eight eyes with recurrence which optic cup were Grade I andⅡ in diseased eyes; 44 eyes(45. 8%) occurred NAION. Correlation analysis showed that there was negative correlation between incidence of fellow eye and optic cup depth(r= -0. 757, P = 0.000). Conclusion Optic cup and disk in NAION patients are smaller than that in the normal, the anatomical characteristics of shallow cup and small disc was one of the NAION pathogenesis. Key words: Optic disc/anatomy & histology,Optic neuropathy,ischemic/etiology; Tomography,optical coherence/utilization