To determine the spring constants of several types of capsular tension rings (CTRs).
Setting
Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany.
Methods
Fourteen models of CTRs provided by 9 companies were tested; all were 11.0 mm in diameter. The CTRs were positioned in a special retainer of a material-testing machine and compressed at a constant speed of 10.0 mm per minute. The distance and force values were recorded, and each CTR model was tested 3 times using a new specimen each time. The resulting measurements were used to calculate a mean spring constant for each CTR model.
Results
All tested CTRs showed linear proportionality between force and compression distance. Test results were repeatable and precise. Capsular tension rings of the same model had comparable mechanical properties, and different models had different mean spring constants ranging from 0.8162 to 4.5501 mN/mm.
Conclusions
The spring constant of a CTR is a suitable mechanical characteristic to facilitate the choice of CTR model. A CTR with a low spring constant may be advantageous for the management of zonular dialysis, whereas a CTR with a higher spring constant may reduce capsular bag shrinkage more effectively.
From the Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany
Reprint requests to Dr. med. Sabine Kurz, Department of Ophthalmology, Johannes Gutenberg-University, Langenbeckstrasse 1, 55101 Mainz, Germany.
None of the authors has a financial or proprietary interest in any material or method mentioned.
ABSTRACT