Ocular Pathology

Anatomy and pathology of the human eye. Use it to review eye pathology for Ophthalmology Board Review or OKAP.

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Sunday, July 01, 2007

Nuclear Sclerosis Cataract

Definition: An opacity in the nucleus of the lens, for which the key histologic criterion is melding or homogenization of lens fiber cells.
Incidence/Prevalence: It is the most common form of cataract and is especially common in older individuals. Subject prevalence for nuclear lens changes is about 3 fold higher than for posterior subcapsular opacities (Reference 1).
Etiology: There are many associations with nuclear cataract. The biochemical changes involve aggregation of lens crystallins as a predominant feature.
Clinical Findings: Symptoms include decreased vision and glare. The patients may experience progressive myopia as the refractive power of the lens accompanies the increased size of the cataractous lens. As the yellow color of the lens increases the patients may notice a subjective difference in their evaluation of colors (this is often referred to as the blue period for artists). Presumably photo-oxidation and the chromophore content accounts for the yellow to brown pigmentation.
Gross: The opacity may appear yellow to brown and loses transparency. In the photograph of a yellow to brunescent nuclear cataract one can appreciate the well defined nature of the nucleus (delimited by the arrows 1). The color varies but the brown pigment near the upper arrow is quite evident. The lens becomes more rigid and difficult to remove surgically as was the case for this lens.
Histopathology: Sections usually show a subtle melding of nuclear fiber cells that gives a homogenous eosinophilic appearance. The lens cells lose their concentric laminations. In the photomicrograph the lens fibers appear to be one mass of pink (arrow 2). The cleft (arrow 3) is an artifact of histologic sectioning. The cells generally do not undergo lysis and the lens cell membranes are generally preserved. The changes are often missed by the uniformed microscopist.
Treatment: Surgical removal of the cataract generally restores vision.

Ophthalmic Epidemiol. 1997;4;195-206.

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