Influence of the Optic Disc Size on Cup Diameter in Patients with Glaucoma Simplex Chronicum

Introduction: The relationship between the optic disc size, neuroretinal rim and cup diameter is the key in identifying glaucomatous changes in optic nerve head. Like some other biological characteristics, changes of the optic disc differ among healthy populations, thus hindering detection of pathological changes. Materia and methods: From the total number of 90 patients, we selected those that have optic disc diameter less than 1.30 mm, greater than 2.10 mm, as well as patients with a size of disc diameter ranging from 1.31mm to 2.09 mm. In all patients after anamnesis and standard ophthalmologic examination (best corrected visual acuity-BCVA, Goldman aplanatic tonometry, pachymetry, gonioscopy), we also performed the OCT analysis of the optic nerve head. Results and discussion: Glaucomatous changes in small optic discs may remain unnoticed unless there is a high degree of suspicion. The assesment of the optic disc size is an important, but often overlooked component of the diagnostic evaluation in glaucoma. There was a statistically significant strong positive correlation between the size of the optic disc diameter and cup diameter, larger optic disc diameter means greater cup diameter. Due to the large variation in the cup size in healthy subjects, the assessment of the morphology of the neuroretinal rim or cup diameter can be more helpful in evaluation of glaucomatous optic disc damage than the value of C/D ratio itself. Conclusion: Evaluation of the optic disc size and C/D ratio is an essential part in diagnostic procedure and management of glaucoma. OCT analysis in patients with small optic disc diameter showed the least sensitivity in all three categories (normal, abnormal and uncertain OCT results). The OCT results in the small optic disc diameter are the least reliable in the diagnosis of glaucoma. More complexed long term study is needed to evaluate this complicated relations between optic disc diameter, C/D ratio, neuroretinal rim and other important clinical factors in emerging glaucoma disease.