Are All Retinal Nerve Fiber Layer Defects on Optic Coherence Tomography Glaucomatous?

Abstract

Objectives: In this study, we investigated the patients who were referred to our clinic with a prediagnosis of glaucoma based on retinal nerve fiber layer (RNFL) defects on optic coherence tomography (OCT) but were determined to have nonglaucomatous RNLF defects upon detailed examination.

Materials and methods: The ophthalmic examination notes, OCT images, Heidelberg retinal tomography (HRT) II and fundus photographs of 357 patients were retrospectively evaluated. Final diagnoses of these patients were investigated.

Results: Of the 357 patients, 216 (60.5%) were diagnosed as open angle glaucoma, 33 (9.2%) as low-tension glaucoma, 39 (10.9%) as pre-perimetric glaucoma. The ophthalmic examinations of 14 patients (3.9%) were normal and there were no RNFL defects in OCT examinations after dilatation. In 39 patients (10.9%), the ophthalmic and optic disc examinations were completely normal and no etiologic factor explaining RNFL defects was found. Twenty-two eyes of 16 patients (4.5%) were included in this study (the mean age was 53.8±11.5 years; 9 men and 7 women). After detailed questioning of the medical history and systemic and neurologic examinations, a diagnosis of ischemic optic neuropathy was made in 11 eyes (10 patients) (2.8%), optic neuritis in 3 eyes (2 patients) (0.6%), optic disc drusen in 4 eyes (2 patients) (0.6%), pseudotumor cerebri in 2 eyes (1 patient) (0.3%), and cerebral palsy in 2 eyes (1 patient) (0.3%).

Conclusion: Decrease in RNFL thickness on OCT images alone may be misleading in glaucoma examination. In cases where optic disc cupping is not evident, diagnosis should not be based on OCT RNFL examinations alone, and the patient's medical history, detailed ophthalmic examination, OCT optic disc parameters, HRT, and visual field tests should all be carefully evaluated together.

Keywords: Anterior ischemic optic neuropathy; Retinal nerve fiber layer; glaucoma; optic coherence tomography.

Figure 1. A 65-year-old male patient with bilateral non-arteritic ischemic optic neuropathy: a, b) There is no cupping in either eye and optic disc pallor is evident in the left eye; c) Optical coherence tomography shows retinal nerve fiber layer (RNFL) defects in both eyes; d) Heidelberg retinal tomography images are within normal limits; e, f) A visual field defect is detected in the region corresonding to RNFL thinning

Figure 2. A patient with history of multiple sclerosis-associated retrobulbar optic neuritis. Optic disc examination, visual field test, and Heidelberg retinal tomography are within normal limits, while optical coherence tomography reveals retinal nerve fiber layer defect in the right eye