Frames need to be suitable for the loupe.
Wrap frames properly designed are often used,with safety shields.
Protection by lightweight plastic splashguards can be easily detached when not required.
The Keeler headband offers adjustable nose pads.
Protective and 1 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 autoclaveable to ensure bio safety.
The correct posture, viewing angle and ability to see normally are the benefits of ‘flip up’ loupes as a three way adjustable hinge allows positioning as required.
TTL LOUPES VERSUS FLM LOUPES
Orascoptic only do TTL (Through The Lens) Loupes. They do not do FLM (Front Lens Mount). Some companies eg Surgitel to offer both. There are benefits to both TTL and FLM. TTL allows the ocular to be closer to the eye thereby 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 they offer a high declination angle which reduces head tilt.
The manufacturing process of TTL loupes is very complicated and the loupes will only fit the measured client. The height of the ocular in the frame is dependent on the bridge of the nose and how the frame sits on the clients face. The width between the oculars depends on the clients inter pupillary distance and the eyes are also not always symmetrical on both sides of the nose so there is a left and a right 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 distance 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 they are being worn and this will change the convergence angle. These measurements are critical to getting a working solution with TTL loupes and the measurements 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.
To fit oculars into a prescription lens, a CNC machine to mill the holes (not done in Australia) and a laser alignment bench to align the oculars before gluing is required. Zeiss loupes eg can be cemented to the front of the lens and can be removed and realigned if required