ScotopicKit
Striatech's ScotopicKit lets you extend the applications of your OptoDrum. With filter foils, you can stepwise reduce absolute light levels inside the OptoDrum to near darkness. Whether you want to monitor rod-based diseases, or ask questions about light adaptation - with the ScotopicKit you can evaluate your animals' visual threshold at different light levels, and characterize rod-driven vision.
The Scotopic Kit: Briefly explained
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Dr. Kaushikaram Subramanian, Max Planck Institute , DresdenWith scotopic optomotor measurements, I could show that mice see better at night due to the inverted nuclear architecture of their rods - a clear evolutionary advantage!
Dr. Hartwig Seitter, University of InnsbruckMany genetic mouse lines reveal differences in visual abilities only under night-vision conditions. With the ScotopicKit, one is able to screen for such differences.
Background: Measuring rodent vision with innate reflex-behavior
All animals have reflexes that help to stabilize the image of the moving environment in their eyes. For example, if a person looks out the window of a moving train her eyes automatically follow the landscape. These compensatory eye movements are caused by the so-called optokinetic reflex. Many animals also have the optomotor reflex which triggers compensatory head movements.
These compensatory eye and head movements are only triggered if the moving stimulus can be seen by the animal. Thus, observing these innate reflexes can be used as a quantatative readout for visual performance needs of animals. In mice and rats, observing the optomotor reflex is particulary convenient: it does not require fixation or surgery, because the corresponding behavior can be observed macroscopically.
Differences between "normal" and scotopic optomotor measurements
The mammalian retina is sometimes called a "duplex retina" because of its two photoreceptor classes: cones support fast vision during daylight conditions (photopic vision), while rods are exquisitely light sensitive and support vision under low-light conditions (scotopic vision). During the transition between different light levels, complex adaptation mechanisms in the photoreceptors and in the retinal circuitry enable continued vision. By measuring the optomotor reflex with the OptoDrum, while changing light levels with the help of the ScotopicKit, you can obtain a behavioral readout of the consequences of light adaptation.
In many mammals, including mice, rats, and humans, rod photoreceptors constitute the majority of photoreceptors. Mutations in rod-specific genes are therefore underlying many retinal diseases, including diseases that lead to blindness. These mutations can affect the optomotor reflex, and this phenomenon can be caught earlier when looking specifically at vision driven by rods, under scotopic conditions.
Even mutations that do not lead to blindness may have functional consequences that can only be seen under scotopic conditions - not only at the cellular and circuitry level in the retina, but also at the level of behavior. Optomotor behavior in particular, measured with the OptoDrum and the ScotopicKit, can provide a convenient readout in these cases.