The focal length of this training eye can be adjusted from +3 to –4.5 to simulate different refractive errors. Hyperopia is simulated with the training eye set to plus powers while myopia is simulated with minus powers.
The Retinoscopy Practice Eye holds three trial lenses, which can be used in conjunction with its built-in adjustable sphere power to further simulate different refractive errors. For example, cylinder lenses can be inserted to simulate astigmatism. An axis scale helps you position your trial lenses. If a simple red reflex is all you require as a student, then the Retinoscopy Practice Eye will help you hone your skills.
The solution shroud is an added bonus that comes with the device. It is used by evaluators to cover the 'solution' (i.e., markings on the trial lenses) so that the student must have mastered retinoscopy to obtain the correct prescription. Without the shroud, the student can read the markings on the trial lens and deduce the refractive error without having mastered the skill.