What instrument is used to evaluate contact lenses in a patient?

The appropriate instrument used to evaluate contact lenses in a patient is the ophthalmoscope. This device allows healthcare providers, particularly eye care professionals, to closely examine the interior structures of the eye, including the cornea and lens, which is crucial when assessing the proper fit and condition of contact lenses. By using an ophthalmoscope, clinicians can determine if there are any signs of irritation, corneal damage, or infection that might be associated with contact lens wear.

In this context, the other instruments listed serve different purposes. A stethoscope is primarily used to listen to heart sounds and evaluate respiratory function, while an otoscope is designed for examining the ears. A dermatoscope is utilized for skin examinations, focusing on dermatological conditions. Therefore, the specialization of the ophthalmoscope in ocular assessments makes it the correct choice for evaluating contact lenses.