Purpose: To modify the HRT-II Confocal Microscope with Rostock Corneal Module (HRT-RCM) to allow computerized control of the focal plane position (depth) within the cornea. Methods: A threaded housing on the HRT-RCM microscope is normally rotated by hand to change the focal plane position within the cornea. This piece was removed to allow the front housing of the microscope to move freely. A linear actuator (Oriel Encoder Mike) was then attached to the side of the microscope and coupled to a drive shaft that was connected to the front housing. The actuator was connected to an Oriel 18011 Encoder Mike controller, which was interfaced to a PC. Software was developed to allow control and display of the focal plane position using this PC, while image acquisition software was run on the HRT-RCM PC. The instrument was tested on one human volunteer. Results: The modified instrument successfully allowed computer-controlled focusing throughout the entire cornea. Through-focus sequences could be collected online and analyzed and reconstructed three dimensionally off-line using modified confocal microscopy through-focusing software. Conclusions: Although this is only a prototype instrument, it significantly improves the examination procedure by allowing completely “hands-free” operation of the HRT-RCM microscope. The data also demonstrate the feasibility of performing quantitative z-axis scans through the full thickness of the cornea with the HRT-RCM. Given the higher contrast images and improved optical sectioning of the HRT-RCM as compared with other instruments, these capabilities could have widespread application.
