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CHAPTER 4

Abnormalities of the Lens

The human lens has a limited response to a wide range of noxious stimuli. The common final end point is cataract, a lenticular opacity produced by degenerative changes in crystalline proteins, Cataracts may form in different parts of the lens depending on the stimulus. Although often distinctive clinically, they are not distinguishable cytologically because the cataractous lens is emulsified by ultrasound (phacoemulsification) or chopped by a vitrectomy cutting instrument. In this chapter, those lens abnormalities that can be diagnosed by cytologic examination are illustrated.

CONGENITAL CATARACTS

There are many clinical types of congenital cataracts, including anterior polar, posterior polar zonular, sutural, membranous, and filiform. The clinical classification is based on location and slit lamp appearance. These types of cataracts cannot be distinguished in most cytologic preparations because they are generally removed by emulsifying the lens with a cutting instrument (e.g., ocutome). Despite the distortion in anatomic organization, numerous nuclei are often apparent in lens fibers of congenital cataracts obtained by emulsification (Figure 4-1) [1]. Rubella produces numerous changes in the eyes of infants, including retinopathy, nongranulomatous uveitis, glaucoma, and congenital cataract (Figure 4-2). Rubella-induced cataracts have been reported to show characteristic retention of nuclei in lens fibers (Figures 4-3 and 4-4) [2, 3, 4, 5, 6]. This feature can be seen in other types of congenital cataract [7, 8].

ADULT CATARACTS

Most adult cataracts have opacities in multiple locations within the lens. Commonly, they are opaque in both the centrally located nucleus (nuclear sclerosis or nuclear cataract)(Figure 4-5) and the peripherally located cortex (cortical cataract). Less often, opacities are present immediately beneath the capsule (subcapsular cataract). Some subcapsular cataracts are associated with trauma. Histologically, nuclear sclerotic cataracts show degenerative melding of lenticular fibers (Figure 4-6). Severely degenerated cortical lens fibers manifest as round eosinophilic globules (globular or Morgagnian degeneration). In cytologic preparations, Morgagnian globules can be identified (Figure 4-7). Sections of anterior and posterior subcapsular cataracts show a plaque of fibrous tissue and, presumably, lens epithelial cell proliferation immediately beneath the capsule (Figure 4-8) [9]. These cataracts are not usually sampled by extracapsular cataract extraction techniques.
Longstanding cataracts may become calcified [10] (cataracta calcarea) presumably by a dystrophic process [11]. In cytologic specimens, calcification appears as basophilic crystals, variable in size and shape, that exhibit birefringence (Figure 4-9 and 4-10). These crystals have been identified as calcium oxylate by x-ray diffraction and electron diffraction.


References:


1.Boniuk M. Rubella and other intraocular viral diseases in infancy. Int Ophthalmol Clin 1972;12:1-37.
2. Yanoff M, Schaffer DB, Scheie HG. Rubella ocular syndrome-clinical significance of viral and pathologic studies. Trans Am Acad Ophthalmol 1968;72:896-902.
3. Boniuk M, Zimmerman LE. Ocular pathology in the rubella syndrome. Arch Ophthalmol 1967;77:455-473.
4. Wolter JR, Insel PA, Willey EN, Brittain HP. Eye pathology following maternal rubella: a study of four children. J Pediat Ophthalmol 1966;3:29-35.
5. Zimmerman LE. The histopathologic basis for the ocular manifestations of the congenital rubella syndrome. Pro Inst Med Chicago 1968;26:170-192
6. Zimmerman LE, Font RL. Congenital malformations of the eye: some recent advances in knowledge of the pathogenesis and histopathological characteristics. JAMA 1966;196:684-692.
7. Hara J, Fujimoto F, Ishibashi T, Seguchi T, Nashimura K,et al. Ocular manifestations of the 1976 rubella epidemic in Japan. Am K Ophthalmol 1979;87:642-645.
8. Boger WP III. Late ocular complications in congenital rubella syndrome. Ophthalmology 1980;87:1244-1252.
9. Yanoff M, Fine BS. Ocular pathology, text and atlas. Philadelphia: J.B. Lippincott, 1989.
10. Harding CV, Chylack LT Jr., Susan SR, Lo W-K, Bobrowski WF, et al. Calcium containing opacities in the human lens. Invest Ophthalmol Vis Sci 1983;24:1194-1202.
11. Zimmerman LE, Johnson FB. Calcium oxalate crystals within ocular tissue. Arch Ophthalmol 1958;60:372-382.

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