Frames need to be suitable for the loupe.
Wrap frames properly designed are often used with safety shields.
Protection by lightweight plastic splash guards can be easily detached when not required.
The Keeler headband offers adjustable nose pads.
Protective and one dioptre distance caps protect the front lens. Powered caps will allow even more magnification but will change working distances.
The loupes removable flip lever and protective caps are easily removed and are designed to be autoclavable to ensure biosafety.
The correct posture, viewing angle and ability to see usually are the benefits of ‘flip up’ loupes as a three-way adjustable hinge allows positioning as required.
TTL LOUPES VERSUS FLM LOUPES
Orascoptic only does TTL (Through The Lens) Loupes. They do not do FLM (Front Lens Mount). Some companies, e.g. Surgitel offer both. There are benefits to both TTL and FLM. TTL allows the ocular to be closer to the eye, providing a larger field of view. They are also set in one position, so no adjustments to be made. TTL loupes are custom-made for each client. FLM loupes are adjustable and offer a high declination angle that reduces head tilt.
The manufacturing process of TTL loupes is very complicated, and the loupes will only fit the measured client. The ocular height in the frame depends on the bridge of the nose and how the frame sits on the client’s face. The width between the oculars depends on the client’s interpupillary distance, and the eyes are also not always symmetrical on both sides of the nose, so there is a left and a correct side measurement. The angle that the oculars are mounted in the glass is related to the working distance for the client, and the two images need to ‘converge’ at the correct length to give one single image. This will also vary depending on the prescription for the client. The convergence will also vary depending on the head width of the client, as the head width will ‘flex’ the frame when worn, which will change the convergence angle. These measurements are critical to getting a working solution with TTL loupes, and the measures become more critical with higher magnifications. That’s why FLM loupes are so easy, as most of these things (except convergence) can be adjusted by the user.
A CNC machine to mill the holes (not done in Australia) and a laser alignment bench to align the oculars before gluing are required to fit oculars into a prescription lens. Zeiss type can be cemented to the front of the lens, removed, and realigned if needed.