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Purpose: To non-invasively measure the thickness of the anterior and posterior lens capsule, and to determine if it significantly changes during accommodation. Methods: Anterior and posterior capsule thickness was measured on post-mortem lenses using a non-contact optical system using a focus-detection technique. The optical system uses a 670nm laser beam delivered to a single-mode fiber coupler. The output of the fiber coupler is focused on the tissue surface using an aspheric lens (NA=0.68) mounted on a translation stage with a motorized actuator. Light reflected from the sample surface is collected by the fiber coupler and sent to a photoreceiver connected to a computer-controlled data acquisition system. Optical intensity peaks are detected when the aspheric lens is focused on the capsule boundaries. The capsule thickness is equal to the distance traveled between two peaks multiplied by the capsule refractive index. Anterior and posterior lens capsule thickness measurements were performed on 18 cynomolgus (age average: 6±1 years, range: 4-7 years) eyes, 1 rhesus (age: 2 years) eye, and 12 human (age average: 65±16, range: 47-92) eyes during simulated accommodation. The mounted sample was placed under the focusing objective of the optical system so that the light was incident on the center pole. Measurements were taken of the anterior lens capsule in the unstretched and the stretched 5mm states. The lens was flipped, and the same procedure was performed for the posterior lens capsule. Results: The precision of the optical system was determined to be ±0.5um. The resolution is 4um and the sensitivity is 52dB. The human anterior lens capsule thickness was 6.0±1.2um unstretched and 4.9±0.9um stretched (p=0.008). The human posterior lens capsule was 5.7±1.2um unstretched and 5.7±1.4um stretched (p=0.974). The monkey anterior lens capsule thickness was 5.9±1.9um unstretched and 4.8±1.0um stretched (p=0.002). The monkey posterior lens capsule was 5.9±2.0um unstretched and 5.1±1.3um stretched (p=0.128). Conclusions: The results indicate that the primate anterior lens capsule thickness changes during accommodation.
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