Purkinje imaging system to measure anterior segment scattering in the human eye

Abstract

We present an instrument based on Purkinje imaging that permits the objective measurement of the amount of scattering associated with the eye's anterior segment, avoiding the contribution from the retina. The experimental system records the fourth Purkinje image, and adequate processing is used to compute a parameter that quantifies the scattering. The method was first tested in an artificial eye and later in normal young eyes wearing customized contact lenses that induced different amounts of scatter. We were able to detect scattering increments, which indicates that this technique may be used as an objective tool to quantify the level of scattering in the anterior segment of the living human eye. The future use of this technique in clinical environments might help to estimate the level of corneal haze in eyes undergoing refractive surgery or/and scattering within the lens during cataract development.

The wide-angle point spread function of the human eye reconstructed by a new optical method

“…The CLs have no refractive power. Their scattering properties have been measured in a separate experiment both optically (Bueno et al, 2007) and psychophysically (by means of the commercially available instrument C-Quant) and were found to contribute with amounts of scatter consistent with normal or Figure 3. Dark-field photograph of the rigid gas-permeable contact lenses that were used to introduce additional light scattering.…”

“…Then, the measurement of the ocular light scattering based on the double-pass technique using a point source is particularly suitable for those cases in which the amount of scatter is relatively high, such as cataracts or dry eye patients, but is characterized by low signal-to-noise ratio and possible bias (due to retinal diffusion) in eyes with clear media. Alternative optical methods have been proposed based on the analysis of Purkinje images (Bueno, De Brouwere et al, 2007) or the dynamic light scatter measurements (Ansari & Datiles, 1999;Datiles, Ansari et al, 2008), but these methods analyze backscattered light rather than the visually relevant-forward scattered light.…”

Volumetric macro- and micro-scale assessment of crystalline lens opacities in cataract patients using long-depth-range swept source optical coherence tomography

“…The concept of straylight measurement is used in the commercial systems like C-Quant (Oculus GmbH, Germany) or Optical Quality Analysis System -High Definition Analyzer (Visiometrics SL, Spain) that have been introduced to clinical practice to assess intraocular scattering [17,[19][20][21]. The analysis of Purkinje images enables also determination of the corneal and lenticular contribution to intraocular scattering without any impact of the retina (as in the double-pass systems) [22]. The intensity of halo around the fourth Purkinje image (P IV ) increases with the amount of scattering.…”

From beach lifeguard to astronaut: occupational vision standards and the implications of refractive surgery

“…In addition to testing in the contrast domain, aberrometry43 44 and sophisticated measures of intraocular light scatter45 46 are evolving that could in future help determine the suitability of candidates for occupations with specific, task related demands on visual performance.…”