RESUMO
PURPOSE: The objective of the present study was to determine what histological changes occur in the photoreceptor layer of male rabbits exposed to intermittent light of different intensities. METHODS: Twelve adult male rabbits were randomly divided into three groups: control group (CON), experimental group I (EXP-1), and experimental group II (EXP-2). The EXP-1 and EXP-2 groups were exposed to a 3-h/3-h light-dark cycle, with light provided by a 60-W or 200-W fluorescent bulb, respectively. The eyes of the rabbits were removed, routinely fixed, and studied by transmission electron microscopy. RESULTS: The EXP-1 rabbits showed the least photoreceptor damage, such as only slight vacuolization in the inner segment, but normal appearance in the other layers. The EXP-2 rabbits showed disorganization and distention in the outer segments and sublethal injury in the inner segment, such as vacuolization, mitochondrial distention and disorganization, increased extracellular space, and distention of cisternae in the rough endoplasmic reticulum. In the EXP-2 group, the outer limiting membrane was absent at some sites, and swelling and pyknosis were present. CONCLUSIONS: These observations suggest that intermittent high-intensity light causes more damage in the photoreceptor layer of the rabbit than does intermittent low-intensity light.
