Abstract
PurposeTo 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.MethodsWe 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.ResultsWe 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.ConclusionsWe 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.
Highlights
Intraocular scattering may severely degrade the retinal image quality [1]
The objective scatter index (OSI) parameter was estimated from the DP images obtained for the 53 eyes included in the study
We calculated the average values of OSI in the patients following the LOCSIII classification
Summary
In eyes suffering early cataracts symptoms this can produce visual disturbances, even if visual acuity remains normal [2]. A first group of methods to evaluate cataract is composed by those based on the analysis of slit-lamp pictures of the patient’s crystalline lens. The slit-lamp images only provide information related to the back-scattered light, while is forward scatter, the responsible of the degradation of retinal image in cataract patients [5]. The relationship between the backward and the forward scatter produced in the crystalline lens depends on the type of cataract [6], which increases the difficulty of a direct interpretation of the slit-lamp images to evaluate the detrimental effect of the cataract on visual performance
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