PURPOSE A method to measure the tear film beneath a soft contact lens, referred to as post-lens tear thickness (PLTT), would have many applications to contact lens research. In this study a noninvasive technique for measuring the PLTT is presented. METHODS The feasibility of measuring the tear layer by optical pachometry was first assessed using a model eye. The baseline corneal thickness (B)...

The purpose of this study was to determine dimensions and curvatures of excised human lenses using the technique of shadowphotogrammetry. A modified optical comparator and digital camera were used to photograph magnified sagittal and coronal lens profiles. Equatorial diameter, anterior and posterior sagittal thickness, anterior and posterior curvatures, and shape factors were obtained from thes...

PURPOSE To characterize changes in the sagittal dimensions of the human crystalline lens and anterior segment as a function of accommodation, to determine the potential age dependence of these changes, and to evaluate these changes in relation to the development of presbyopia. METHODS Scheimpflug slit-lamp photography, as well as a variety of standard ophthalmologic methods, was used to colle...

To investigate the etiology of contact lens-induced transient endothelial changes (blebs) in the human cornea, the effects of five different stimuli on corneal thickness and the appearance of the corneal endothelium were assessed. The stimuli included: (1) a silicone contact lens; (2) a silicone contact lens in combination with anoxia; (3) anoxia alone; (4) a thick hydroxyethyl methacrylate (HE...

Consecutive patients undergoing intracapsular cataract surgery with and without lens implantation were included in one of three groups of fifteen patients for postoperative corneal thickness measurement. One group underwent cataract extraction alone, another group had cataract extraction and lens implantation using iris supported posterior chamber implants, and another group underwent lens impl...

PURPOSE To demonstrate the feasibility of indirectly measuring the precorneal tear film thickness and pre- and postlens tear film (PLTF) thickness using optical coherence tomography (OCT). METHODS Central corneal thickness (C(1)) which includes the tear film (T) of both eyes of 40 non-contact lens wearers was measured using OCT after calibration. The mean age of the 40 subjects was 31.2 +/- 9...

The search for environmental factors associated with cataract has produced conflicting evidence and one possible reason may be that environmental influences are initiating events occurring perhaps for short periods many years before loss of sight from cataract. It is important, therefore, to be able to detect the earliest changes of cataract formation so that epidemiological studies have a bett...

PURPOSE To study the relationships between the refractive power of the crystalline lens, overall refractive error of the eye, and degree of nuclear cataract. METHODS All phakic participants of the population-based Central India Eye and Medical Study with an age of 50+ years were included. Calculation of the refractive lens power was based on distance noncycloplegic refractive error, corneal r...

PURPOSE To evaluate anterior chamber depth, central crystalline lens thickness and lens curvature during accommodation. SETTING California Retina Associates, El Centro, CA, USA. DESIGN Healthy volunteer, prospective, clinical research swept-source optical coherence biometric image registration study of accommodation. METHODS Ten subjects (4 females and 6 males) with an average age of 22.5...

UNLABELLED PURPOSE. To compare the accuracy of different methods of calculating human lens power when lens thickness is not available. METHODS. Lens power was calculated by four METHODS Three methods were used with previously published biometry and refraction data of 184 emmetropic and myopic eyes of 184 subjects (age range, 18-63 years; spherical equivalent range, -12.38 to +0.75 D). These t...