Large optic nerve heads: megalopapilla or megalodiscs.

Purpose: To evaluate megalopapillas in order to determine whether they constitute a different population, according to their specific features.

Material: Evaluation of the optic nerve head of 405 eyes divided into 172 normal eyes, 168 pre-perimetric glaucomas (phase 3 or 4), 30 primary congenital glaucomas (children with pure congenital glaucomas operated more than once and diagnosed within the first year of age), and 35 megalopapillas.

Method: The examinations were performed with the HRT (Heidelberg Retina Tomograph), using a wavelength of 680 nm and the new standard reference plane. Each examination results from the mean of 3 image acquisitions with a SD lower than n = 20. Each optic nerve head was studied in 360 degrees (segments), as well as in quadrants and octants separately (predefined segments). The visual fields were assessed with either the Octopus 1-2-3 or the Octopus 101, programs G2 and G2x (three complete phases). The intraocular pressure was measured by means of daily pressure curves including 7 measurements with applanation tonometry at the office and the first one at 6/7 a.m. with the patient still in bed. Gonioscopic examinations were also performed for classification purposes.

Results: By comparing all the stereometric parameters with the Total Area (disc area) and the Rim Volume it has been concluded that the megalopapilla group is different from both the normal control group and the glaucoma group. The disc area of the congenital glaucomas was not statistically different from the megalopapillas, but it was in terms of rim volume and other parameters.

Conclusion: megalopapilla is an entity characterized by a large optic nerve head which may appear abnormal, with an increased cup, but associated with a normal rim volume, normal visual field and normal IOP. Special attention should be given to its differentiation from pseudoglaucomatous diseases.

Discussion: The frequency of megalopapillas seems to be quite higher than in congenital optic nerve head anomalies, but is has been virtually ignored by the literature worldwide so far.