Purpose: To compare artificial eye amplitudes in patients who randomly received either a hydroxyapatite or an acrylic, scleral-covered spherical implant after enucleation.

Design: Randomized, controlled trial.

Participants: Thirty-four consecutive patients who underwent enucleation because of an intraocular melanoma and 21 healthy control participants from the hospital staff.

Methods: Eligible patients randomly received a hydroxyapatite or an acrylic, scleral-covered spherical orbital implant. Fourteen patients were fitted with a hydroxyapatite implant, and 16 were fitted with an acrylic implant. We measured horizontal and vertical saccadic amplitudes of both the artificial eye and the healthy eye. Measurements were performed with the magnetic search coils technique. Saccadic amplitudes of the artificial eye were compared with the healthy eye of the patient. The amplitudes of the healthy eyes were compared with saccadic amplitudes of control participants. The interval from surgery to measurements was at least 3 months in all patients. Saccadic gain (artificial eye and eye amplitude divided by target amplitude) and saccadic symmetry (artificial eye amplitude divided by healthy eye amplitude) were calculated.

Main outcome measures: Saccadic gain and saccadic symmetry.

Results: The gain in the healthy eyes of the patients was comparable with the gain of the control eyes. Saccadic symmetry was 1.0 in control participants. In patients, it was 0.334 in horizontal saccades and 0.577 in vertical saccades. However, saccadic symmetry did not differ significantly between the acrylic group and the hydroxyapatite group (P: > 0.1 for any saccadic direction). Equivalence was detectable with a power more than 90% for horizontal saccades and more than 80% for vertical saccades. Curvilinearity was rejected for both patient groups and for all saccadic directions (P: > 0.5).

Conclusions: When no motility peg is placed, acrylic and hydroxyapatite spherical implants yield comparable saccadic amplitudes of the artificial eye. Artificial eye amplitudes were markedly more restricted horizontally than vertically. In all saccadic directions, the relation between target amplitude and artificial eye amplitude was linear.