Use of a new night vision enhancement device (DAVIS)

Night blindness severely hinders orientation especially during darkness. As a result of a European project a night vision enhancement system is availa ble. We wanted to evaluate the acceptance and possibilities of rehabilitati on with those night vision glasses (DAVIS) during conditions simulating typ ical outdoor activities. Patients and Methods: Following complete ophthalmologic examination 37 pati ents with night blindness due to Retinitis Pigmentosa (sometimes Usher-Synd rome) and Choroideremia (n=3) performed several tests with DAVIS during dar kness. We evaluated the improvement of visual function on a special outside course in the city of Heidelberg (duration 1.5 to 4 hours). Results: Twenty six of the patients were able to better recognize obstacles , 28 could see objects which were not seen without DAVIS. Twenty two of the 37 patients would use the DAVIS. Patients needed a visual acuity of more t han 0.1 and more than 6 degree of central visual field to experience improv ement with DAVIS. However, in patients with only minimal changes of the vis ual field, the restriction due to the presence of the device was a drawback . Sudden occurrence of light sources leads to blinding and limits the indoo r use. Conclusion: DAVIS enhances contrast acuity especially during night and twil ight. This leads to improvement of orientation due to better recognition of obstacles and allows rehabilitation of patients with night blindness for o utdoor mobility. Individual test and adjustment of DAVIS is necessary to al low exact and adequate prescription.