An objective scatter index based on double-pass retinal images of a point source to classify cataracts.

PURPOSE: To propose a new objective scatter index (OSI) based in the analysis of double-pass images of a point source to rank and classify cataract patients. This classification scheme is compared with a current subjective system. METHODS: We selected a population including a group of normal young eyes as control and patients diagnosed with cataract (grades NO2, NO3 and NO4) according to the Lens Opacities Classification System (LOCS III). For each eye, we recorded double-pass retinal images of a point source. In each patient, we determined an objective scatter index (OSI) as the ratio of the intensity at an eccentric location in the image and the central part. This index provides information on the relevant forward scatter affecting vision. Since the double-pass retinal images are affected by both ocular aberrations and intraocular scattering, an analysis was performed to show the ranges of contributions of aberrations to the OSI. RESULTS: We used the OSI values to classify each eye according to the degree of scatter. The young normal eyes of the control group had OSI values below 1, while the OSI for subjects in LOCS grade II were around 1 to 2. The use of the objective index showed some of the weakness of subjective classification schemes. In particular, several subjects initially classified independently as grade NO2 or NO3 had similar OSI values, and in some cases even higher than subjects classified as grade NO4. A new classification scheme based in OSI is proposed. CONCLUSIONS: We introduced an objective index based in the analysis of double-pass retinal images to classify cataract patients. The method is robust and fully based in objective measurements; i.e., not depending on subjective decisions. This procedure could be used in combination with standard current methods to improve cataract patient surgery scheduling.

Cause of monocular diplopia diagnosed by combining double-pass retinal image assessment and Hartmann-Shack aberrometry.

PURPOSE: To report an advanced optical procedure developed for the diagnosis of a particular case of diplopia. METHODS: This approach combined the quantification of the level of intraocular scattering by using an Objective Scatter Index provided by a double-pass instrument (Optical Quality Analysis System) with the analysis of higher order aberrations using a Hartmann-Shack wavefront sensor. RESULTS: The value of the Objective Scatter Index revealed increased intraocular scattering; the Hartmann-Shack images showed the existence of an optically differentiated area at the upper region of both crystalline lenses. Simulation of retinal images computed from the wavefront maps confirmed that, under low luminance conditions, this inhomogeneous region of the lens was included in the pupil, generating a secondary image and therefore the diplopia. CONCLUSIONS: This report demonstrates the potential of combining two objective optical methods to show the presence of minor lens opacities that may severely degrade quality of vision.