1154 workers in the Parma area will be screened for eligibility to long-term use of video-monitors. Those referred to the Glaucoma Clinic for suspected PDS will be enrolled in the study.
In a prospective study on the natural history of PDS and PG, Richter et al. (Arch Ophtal 104:211-5, 1986) found an association between "active pigment dispersion" and elevated IOP. Therefore, in order to evaluate the "stability" of the pigment, a phenylephrine test will be performed following the method reported by Epstein et al (1978) AJO 85:43-50. The test will be performed by one investigator (SAG)and was considered positive if \> "grade 1+" (i.e. at least 10 particles in a single light beam). Eyes showing a positive test will be considered as "high-risk" for conversion to PG.
Yag laser iridotomy will be performed in patients showing both eyes at high risk. One eye only (randomly chosen) will be treated. the fellow eye will be left untreated and considered as internal control.
Low risk eyes will be followed without any intervention.
