No abstract

The purpose of this study was to study the age-dependence of the optomechanical properties of human lenses during simulated disaccommodation in a mechanical lens stretcher, designed to determine accommodative forces as a function of stretch distance, to compare the results with in vivo disaccommodation and to examine whether differences exist between eyes harvested in the USA and India. Post-mortem human eyes obtained in the USA (n=46, age = 6 to 83 years) and India (n=91, age = 1 day to 85 years) were mounted in an optomechanical lens stretching system and dissected to expose the lens complete with its accommodating framework, including zonules, ciliary body, anterior vitreous and a segmented rim of sclera. Disaccommodation was simulated through radial stretching of the sectioned globe by 2 mm in increments of 0.25 mm. The load, inner ciliary ring diameter, lens equatorial diameter, central thickness and power were measured at each step. Changes in these parameters were examined as a function of age, as were the dimension/load and power/load responses. Unstretched lens diameter and thickness increased over the whole age range examined and were indistinguishable from those of in vivo lenses as well as those of in vitro lenses freed from zonular attachments. Stretching increased the diameter and decreased the thickness in all lenses examined but the amount of change decreased with age. Unstretched lens power decreased with age and the accommodative amplitude decreased to zero by age 45-50. The load required to produce maximum stretch was independent of age (median 80 mN) whereas the change in lens diameter and power per unit load decreased significantly with age. The age related changes in the properties of human lenses, as observed in the lens stretching device, are similar to those observed in vivo and are consistent with the classical Helmholtz theory of accommodation. The response of lens diameter and power to disaccommodative (stretching) forces decreases with age, consistent with lens nuclear stiffening.

Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) are widely used retinal imaging modalities that can assist in the diagnosis of retinal pathologies. The combination of SLO and OCT provides a more comprehensive imaging system and a method to register OCT images to produce motion corrected retinal volumes. While high quality, bench-top SLO-OCT systems have been discussed in the literature and are available commercially, there are currently no handheld designs. We describe the first design and fabrication of a handheld SLO/spectral domain OCT probe. SLO and OCT images were acquired simultaneously with a combined power under the ANSI limit. High signalto-noise ratio SLO and OCT images were acquired simultaneously from a normal subject with visible motion artifacts. Fully automated motion estimation methods were performed in post-processing to correct for the inter-and intra-frame motion in SLO images and their concurrently acquired OCT volumes. The resulting set of reconstructed SLO images and the OCT volume were without visible motion artifacts. At a reduced field of view, the SLO resolved parafoveal cones without adaptive optics at a retinal eccentricity of 11° in subjects with good ocular optics. This system may be especially useful for imaging young children and subjects with less stable fixation.