Ординатура / Офтальмология / Английские материалы / Veterinary Ocular Pathology A Comparative Review_Dubielzig, Ketring, McLellan_2010

Williams, L.W., Gelatt, K.N., Gwin, R.M., 1981. Ophthalmic neoplasms in the cat. J. Am. Anim. Hosp. Assoc. 17, 999–1008.

Gwin, R.M., Gelatt, K.N., Williams, L.W., 1982. Ophthalmic neoplasms in the dog. J. Am. Anim. Hosp. Assoc. 18, 853–866.

Dubielzig, R.R., 1990. Ocular neoplasia in small animals. Vet. Clin. North Am. Small Anim. Pract. 20, 837–848.

Uveal melanocytic neoplasia

Mould, J.R.B., Petersen-Jones, S.M., Peruccio, C., et al., 2002. Uveal melanocytic tumors. In: Peiffer Jr., R.L., Simons, K.B. (Eds), Ocular tumors in humans and animals, 1st edn. Iowa State Press, Ames, Iowa, pp. 225–288.

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Bussanich, N.M., Dolman, P.J., Rootman, J.,

et al., 1987. Canine uveal melanomas: series and literature review. J. Am. Anim. Hosp. Assoc. 23, 415–422.

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Trucksa, R.C., 1983. Canine ocular melanocytic neoplasms. In: Peiffer Jr., R.L. (Ed.), Comparative ophthalmic pathology. Charles C. Thomas, Springfield, pp. 170–182.

Wilcock, B.P., Peiffer Jr., R.L., 1986. Morphology and behavior of primary ocular melanomas in 91 dogs. Vet. Pathol. 23, 418–424.

Dubielzig, R.R., Aguirre, G.D., Gross, S.L., et al., 1985. Choroidal melanomas in dogs. Vet. Pathol. 22, 582–585.

Collinson, P.N., Peiffer, R.L., 1993. Clinical presentation, morphology, and behavior of primary choroidal melanomas in eight dogs. Prog. Vet. Comp. Ophthalmol. 3, 158–164.

Aguirre, G.D., Brown, G., Shields, J.A., et al., 1984. Melanoma of the choroid in a dog. J. Am. Anim. Hosp. Assoc. 20, 471–476.

Schoster, J.V., Dubielzig, R.R., Sullivan, L., 1993. Choroidal melanoma in a dog. J. Am. Vet. Med. Assoc. 203, 89–91.

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canine survival with primary intraocular melanocytic neoplasia. Vet. Ophthalmol. 2, 185–190.

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Yi, N.Y., Park, S.A., Park, S.W., et al., 2006. Malignant ocular melanoma in a dog. J. Vet. Sci. 7, 89–90.

Kato, K., Nishimura, R., Sasaki, N., et al., 2005. Magnetic resonance imaging of a canine eye with melanoma. J. Vet. Med. Sci. 67, 179–182.

Feline diffuse iris melanoma

Patnaik, A.K., Mooney, S., 1988. Feline melanoma: a comparative study of ocular, oral and dermal neoplasms. Vet. Pathol. 25, 105–112.

Duncan, D.E., Peiffer, R.L., 1991. Morphology and prognostic indicators of anterior uveal melanomas in cats. Prog. Vet. Comp.

Ophthalmol. 1, 25–32.

Day, M.J., Lucke, V.M., 1995. Melanocytic neoplasia in the cat. J. Small Anim. Pract. 36, 207–213.

Bertoy, R.W., Brightman, A.L., Regan, K., 1988. Intraocular melanoma with multiple metastases in a cat. J. Am. Vet. Med. Assoc. 192, 87–89.

Bjerkas, E., Arnesen, K., Peiffer Jr., R.L., 1997. Diffuse amelanotic iris melanoma in a cat. Vet. Comp. Ophthalmol. 7, 190–191.

Kalishman, J.B., Chappell, R., Lisa Flood, L.A., et al., 1998. Matched observational study of survival in cats with enucleation due to diffuse iris melanoma. Vet. Ophthalmol. 1, 25–29.

Harris, B.P., Dubielzig, R.R., 1999. Atypical primary ocular melanoma in cats. Vet. Ophthalmol. 2, 121–124.

Stiles, J., Bienzle, D., Render, J.A., et al., 1999. Use of nested polymerase chain reaction (PCR) for detection of retroviruses from formalin-fixed, paraffin-embedded uveal melanomas in cats. Vet. Ophthalmol. 2, 113–116.

Equine uveal melanocytic neoplasms

Equine melanoma

Murphy, J., Young, S., 1979. Intraocular melanoma in a horse. Vet. Pathol. 16, 539–542.

Latimer, C.A., Wyman, M., 1983. Sector iridectomy in the management of iris melanoma in a horse. Equine Vet. J. Suppl. 2, 101–104.

Matthews, A.G., Barry, D.R., 1987. Bilateral melanoma of the iris in a horse. Equine Vet. J. 19, 358–360.

Barnett, K.C., Platt, H., 1990. Intraocular melanomata in the horse. Equine Vet. J. (Suppl. 10), 76–82.

Davidson, H.J., Blanchard, G.L., Wheeler, C.A., et al., 1991. Anterior uveal melanoma, with secondary keratitis, cataract, and glaucoma,

in a horse. J. Am. Vet. Med. Assoc. 199, 1049–1050.

Scotty, N.C., Barrie, K.B., Brooks, D.E., et al., 2008. Surgical management of a progressive iris melanocytoma in a Mustang. Vet. Ophthalmol. 11, 75–80.

Iris and ciliary body epithelial neoplasms

Peiffer Jr., R.L., 1983. Ciliary body epithelial tumours in the dog and cat; a report of thirteen cases. J. Small Anim. Pract. 24, 347–370.

Peiffer Jr., R.L., 1983. Ciliary body epithelial tumors. In: Peiffer Jr., R.L. (Ed.), Comparative ophthalmic pathology. Charles C. Thomas, Springfield, pp. 183–212.

Lavach, J.D., 1984. Iridociliary adenoma in a dog. J. Am. Anim. Hosp. Assoc. 20, 468–470.

Clerc, B., 1996. Surgery and chemotherapy for the treatment of adenocarcinoma of the iris and ciliary body in five dogs. Vet. Comp.

Ophthalmol. 6, 265–270.

Dubielzig, R.R., Steinberg, H., Garvin, H., et al., 1998. Iridociliary epithelial tumors in 100 dogs and 17 cats: a morphological study. Vet. Ophthalmol. 1, 223–231.

Zarfoss, M.K., Dubielzig, R.R., 2007. Metastatic Iridociliary Adenocarcinoma in a Labrador Retriever. Vet. Pathol. 44, 672–676.

Klosterman, E., Colitz, C.M., Chandler, H.L., et al., 2006. Immunohistochemical properties of ocular adenomas,

adenocarcinomas and medulloepitheliomas. Vet. Ophthalmol. 9, 387–394.

Hendrix, D.V., Donnell, R.L., 2007. Lenticular Invasion by a ciliary body adenocarcinoma in a dog. Vet. Pathol. 44, 540–542.

Langloss, J.M., Zimmerman, L.E., Krehibiel, J.D., 1976. Malignant intraocular teratoid medulloepithelioma in three dogs. Vet. Pathol. 13, 343–352.

Lahav, M., Albert, D.M., Kircher, C.H., et al., 1976. Malignant teratoid medulloepithelioma in a dog. Vet. Pathol. 13, 11–16.

Wilcock, B., Williams, M.M., 1980. Malignant intraocular medulloepithelioma in a dog. J. Am. Anim. Hosp. Assoc. 16, 617–619.

Jensen, O.A., Kaarsholm, S., Prause, J.U., et al., 2003. Neuroepithelial tumor of the retina in a dog. Vet. Ophthalmol. 6, 57–60.

Aleksandersen, M., Bjerkas, E., Heiene, R., et al., 2004. Malignant teratoid medulloepithelioma with brain and kidney involvement in a dog. Vet. Ophthalmol. 7, 407–411.

Bistner, S.I., 1974. Medullo-epithelioma of the iris and ciliary body in a horse. Cornell. Vet. 64, 588–595.

Eagle Jr., R.C., Font, R.L., Swerczek, T.W., 1978. Malignant medulloepithelioma of the optic nerve in a horse. Vet. Pathol. 15, 488–494.

Szymanski, C.M., 1987. Malignant teratoid medulloepithelioma in a horse. J. Am. Vet. Med. Assoc. 190, 301–302.

Riis, R.C., Scherlie, P.H., Rebhun WC, 1990. Intraocular medulloepithelioma in a horse. Equine Vet. J. Suppl. 10, 66–68.

Knottenbelt, D.C., Hetzel, U., Roberts, V., 2007. Primary intraocular primitive neuroectodermal tumor (retinoblastoma) causing unilateral blindness in a gelding. Vet. Ophthalmol. 10, 348–356.

Hendrix, D.V., Bochsler, P.N., Saladino, B., et al., 2000. Malignant teratoid

medulloepithelioma in a llama. Vet. Pathol. 37, 680–683.

Schmidt, R.E., Becker, L.L., McElroy, J.M., 1986. Malignant intraocular medulloepithelioma in two cockatiels. J. Am. Vet. Med. Assoc. 189, 1105–1106.

Bras, I.D., Gemensky-Metzler, A.J., Kusewitt, D.F., et al., 2005. Immunohistochemical characterization of a malignant intraocular teratoid medulloepithelioma in a cockatiel. Vet. Ophthalmol. 8, 59–65.

Shields, J.A., Eagle Jr., R.C., Shields, C.L., et al., 1996. Acquired neoplasms of the nonpigmented ciliary epithelium (adenoma and adenocarcinoma). Ophthalmology 103, 2007–2016.

Lymphoma and histiocytic neoplasia

Carlton, W.C., Hutchinson, A.K., Grossniklaus, H.E., 2002. Ocular lymphoid proliferations. In: Peiffer Jr., R.L., Simons, K.B. (Eds.), Ocular tumors in animals and humans,

1st edn. Iowa State Press, Ames, Iowa, pp. 379–413.

Corcoran, K.A., Peiffer Jr., R.L., Koch SA, 1995. Histopathologic features of feline ocular lymphosarcoma: 49 cases (1978–1992). Vet. Comp. Ophthalmol. 5, 35–41.

Nell, B., Suchy, A., 1998. ‘D-shaped’ and ‘reverse-D-shaped’ pupil in a cat with lymphosarcoma. Vet. Ophthalmol. 1, 53–56.

Dubielzig, R., Steinberg, H., Fischer, B., et al., 2000. Feline primary ocular lymphosarcoma: immunophenotyping of leukocytes, FeLV status and relationship to idiopathic lymphoplasmacytic uveitis. In: Proceedings of the 31st Annual Meeting of the American College of Veterinary Ophthalmology, Montreal, Canada, p. 46.

Couto, G.C., 2001. What is new on feline lymphoma? J. Feline Med. Surg. 3, 171–176.

Grahn, B.H., Peiffer, R.L., Cullen, C.L., et al., 2006. Classification of feline intraocular neoplasms based on morphology, histochemical staining, and immunohistochemical labeling. Vet. Ophthalmol. 9, 395–403.

Brightman, A.H. 2nd, Ogilvie, G.K., Tompkins, M., 1991. Ocular disease in FeLV-positive cats: 11 cases (1981–1986). J. Am. Vet. Med. Assoc. 198, 1049–1051.

Cello, R.M., Hutcherson, B., 1962. Ocular changes in malignant lymphoma of dogs. Cornell. Vet. 52, 492–523.

Krohne, S.G., Henderson, N.M., Richardson, R.C., et al., 1994. Prevalence of ocular involvement in dogs with multicentric lymphoma: prospective evaluation of 94

cases. Vet. Comp. Ophthalmol. 4, 127– 135.

Kilrain, C.G., Saik, J.E., Jeglum, K.A., 1994. Malignant angioendotheliomatosis with retinal detachments in a dog. J. Am. Vet. Med. Assoc. 204, 918–921.

Cullen, C.L., Caswell, J.L., Grahn, B.H., 2000. Intravascular lymphoma presenting as bilateral panophthalmitis and retinal detachment in a dog. J. Am. Anim. Hosp. Assoc. 36, 337–342.

Bush, W.W., Throop, J.L., McManus, P.M., et al., 2003. Intravascular lymphoma involving the central and peripheral nervous systems in a dog. J. Am. Anim. Hosp. Assoc. 39, 90–96.

McDonough, S.P., Van Winkle, T.J., Valentine, B.A., et al., 2002. Clinicopathological and immunophenotypical features of canine intravascular lymphoma (malignant angioendotheliomatosis). J. Comp. Pathol. 126, 277–288.

Affolter, V.K., Moore, P.F., 2002. Localized and disseminated histiocytic sarcoma of

dendritic cell origin in dogs. Vet. Pathol. 39, 74–83.

Naranjo, C., Dubielzig, R.R., Friedrichs, K.R., 2007. Canine ocular histiocytic sarcoma. Vet. Ophthalmol. 10, 179–185.

Moore, P.F., 1984. Systemic histiocytosis of Bernese mountain dogs. Vet. Pathol. 21, 554–563.

Moore, P.F., Rosin, A., 1986. Malignant histiocytosis of Bernese mountain dogs. Vet. Pathol. 23, 1–10.

Rosin, A., Moore, P., Dubielzig, R., 1986. Malignant histiocytosis in Bernese Mountain dogs. J. Am. Vet. Med. Assoc. 188, 1041–1045.

Brearley, M.J., Dunn, K.A., Smith, K.C., et al., 1994. Systemic histiocytosis in a Bernese mountain dog. J. Small Anim. Pract. 35, 271–274.

Paterson, S., Boydell, P., Pike, R., 1995. Systemic histiocytosis in the Bernese mountain dog. J. Small Anim. Pract. 36, 233–236.

Other ocular neoplasms

Sato, T., Yamamoto, A., Shibuya, H., et al., 2005. Intraocular peripheral nerve sheath tumor in a dog. Vet. Ophthalmol. 8, 283–286.

Zarfoss, M.K., Klauss, G., Newkirk, K., et al., 2007. Uveal Spindle Cell Tumor of Blue-Eyed Dogs: An Immunohistochemical Study. Vet. Pathol. 44, 276–284.

Feline post-traumatic ocular sarcoma

Woog, J., Albert, D.M., Gonder, J.R., et al., 1983. Osteosarcoma in a phthisical feline eye. Vet. Pathol. 20, 209–214.

Dubielzig, R.R., 1984. Ocular sarcoma following trauma in three cats. J. Am. Vet. Med. Assoc. 184, 578–581.

Dubielzig, R.R., Everitt, J., Shadduck, J.A., et al., 1990. Clinical and morphologic features of post-traumatic ocular sarcomas in cats. Vet.

Pathol. 27, 62–65.

Dubielzig, R.R., Hawkins, K.L., Toy, K.A., et al., 1994. Morphologic features of feline ocular sarcomas in 10 cats: light microscopy, ultrastructure, and immunohistochemistry. Vet. Comp. Ophthalmol. 4, 7–12.

Cullen, C.L., Haines, D.M., Jackson, M.L., et al., 1998. The use of immunohistochemistry and the polymerase chain reaction for detection of feline leukemia virus and feline sarcoma virus in six cases of feline ocular sarcoma. Vet. Ophthalmol. 1, 189–193.

Grossniklaus, H.E., Zimmerman, L.E., Kachmer, M.L., 1990. Pleomorphic adenocarcinoma of the ciliary body. Immunohistochemical

and electron microscopic features. Ophthalmology 97, 763–768.

Zeiss, C.J., Johnson, E.M., Dubielzig, R.R., 2003. Feline intraocular tumors may arise from transformation of lens epithelium. Vet. Pathol. 40, 355–362.

Carter, R.T., Giudice, C., Dubielzig, R.R., et al., 2005. Telomerase activity with concurrent loss of cell cycle regulation in feline post-traumatic ocular sarcomas. J. Comp. Pathol. 133, 235–245.

Neoplasia metastatic to the eye

Dubielzig, R.R., Grendahl, R.L., Orcutt, J.C., et al., 2002. Metastases. In: Peiffer Jr., R.L., Simons, K.B. (Eds), Ocular tumors in animals and humans. Iowa State Press, Ames, Iowa, pp. 337–378.

Ladds, P.W., Gelatt, K.N., Strafuss, A.C., et al., 1970. Canine ocular adenocarcinoma of mammary origin. J. Am. Vet. Med. Assoc. 156, 63–69.

Szymanski, C.M., 1972. Bilateral metastatic intraocular hemangiosarcoma in a dog. J. Am. Vet. Med. Assoc. 161, 803–805.

Bellhorn, R.W., 1972. Secondary ocular adenocarcinoma in three dogs and a cat. J. Am. Vet. Med. Assoc. 160, 302–307.

Carlton, W.W., 1983. Intraocular tumors. In: Peiffer Jr., R.L. (Ed.), Comparative

ophthalmic pathology. Charles C. Thomas, Springfield, pp. 289–298.

Render, J.A., Carlton, W.W., Vestre, W.A., et al., 1982. Osteosarcoma metastatic to the globes in a dog. Vet. Pathol. 19, 323–326.

Schmidt, R.E., 1981. Transitional cell carcinoma metastatic to the eye of a dog. Vet. Pathol. 18, 832–834.

Szymanski, C., Boyce, R., Wyman, M., 1984. Transitional cell carcinoma of the urethra metastatic to the eyes in a dog. J. Am. Vet. Med. Assoc. 185, 1003–1004.

Lavach, J.D., 1984. Disseminated neoplasia presenting with ocular signs: a report of two cases. J. Am. Anim. Hosp. Assoc. 20, 459–462.

HogenEsch, H., Whiteley, H.E., Vicini, D.S., et al., 1987. Seminoma with metastases in

the eyes and the brain in a dog. Vet. Pathol. 24, 278–280.

Nyska, A., Hermalin, A., Jacobson, B., et al., 1992. Intraocular vascular embolization of a malignant canine pheochromocytoma. Prog. Vet. Comp. Ophthalmol. 2, 129–132.

Habin, D.J., Else, R.W., 1995. Parotid salivary gland adenocarcinoma with bilateral ocular and osseous metastases in a dog. J. Small Anim. Pract. 36, 445–449.

Ferreira, A.J., Jaggy, A., Varejao, A.P.,

et al., 2000. Brain and ocular metastases from a transmissible venereal tumour in a dog. J. Small Anim. Pract. 41, 165– 168.

Pereira, J.S., Silva, A.B., Martins, A.L., et al., 2000. Immunohistochemical characterization of intraocular metastasis of a canine transmissible venereal tumor. Vet. Ophthalmol. 3, 43–47.

Esson, D., Fahrer, C.S., Zarfoss, M.K., et al., 2007. Suspected uveal metastasis of a nail

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bed melanoma in a dog. Vet. Ophthalmol. 10, 262–266.

Extraskeletal osteosarcoma and chondrosarcoma

Patnaik, A.K., 1990. Canine extraskeletal osteosarcoma and chondrosarcoma: a clinicopathologic study of 14 cases. Vet. Pathol. 27, 46–55.

Hayden, D.W., 1976. Squamous cell carcinoma in a cat with intraocular and orbital metastases. Vet. Pathol. 13, 332–336.

Murphy, C.J., Canton, D.C., Bellhorn, R.W.,

et al., 1989. Disseminated adenocarcinoma with ocular involvement in a cat. J. Am. Vet. Med. Assoc. 195, 488–491.

Hamilton, H.B., Severin, G.A., Nold, J., 1984. Pulmonary squamous cell carcinoma with intraocular metastasis in a cat. J. Am. Vet. Med. Assoc. 185, 307–309.

Cook, C.S., Peiffer Jr., R.L., Stine, P.E., 1984. Metastatic ocular squamous cell carcinoma in a cat. J. Am. Vet. Med. Assoc. 185, 1547–1549.

Gionfriddo, J.R., Fix, A.S., Niyo, Y., et al., 1990. Ocular manifestations of a metastatic pulmonary adenocarcinoma in a cat. J. Am. Vet. Med. Assoc. 197, 372–374.

Cassotis, N.J., Dubielzig, R.R., Gilger, B.C., et al., 1999. Angioinvasive pulmonary

carcinoma with posterior segment metastasis in four cats. Vet. Ophthalmol. 2, 125–131.

NORMAL ANATOMY (Fig. 10.1)

•The lens has only one cell type, the lens epithelial cell

•At all stages of lens development, except embryonic, normal lens epithelial cells are only present anteriorly, where they form a monolayer of cuboidal epithelium (Chapter 3 provides a more detailed discussion of lens development)

•At the lens equator, the lens epithelial cell elongates, rotates and is pushed inward. The cell then continues to elongate until the anterior and posterior tips of each lens fiber reach opposite poles of the lens. The fully differentiated lens fiber cells lose their nuclei and become compacted towards the center of the lens, as new fibers continue to form throughout life

•The lens is surrounded by a thick capsule which represents the basement membrane of the lens epithelium. Throughout life, the anterior lens capsule continues to thicken while the posterior capsule remains thin, since there are no lens epithelial cells at the posterior pole

•In mammals, the lens is held in place on the anterior vitreous face by a combination of the gentle pressure exerted from behind by the vitreous body, and the tension of zonular ligaments that suspend the lens circumferentially. These zonules are secreted by the ciliary epithelium and insert in a crossover pattern onto the equatorial lens capsule.

Comparative Comments

•The lens is a simple structure histologically and in the human generally conforms to the description given for the lens in other species

•The remarkable complexity of the lens is hidden at the molecular and functional levels.

CONGENITAL OR HEREDITARY CONDITIONS

(see Ch. 3)

Posterior lenticonus/lentiglobus (Fig. 10.2)

•Posterior lenticonus or lentiglobus is characterized by the localized axial elongation and increased curvature of the

posterior lens, leading to a conical or spherical protrusion of the posterior pole of the lens

•Stretching, thinning or discontinuity of the posterior capsule are frequent findings in posterior lenticonus/lentiglobus.

Aphakia, microphakia, lens coloboma (Fig. 10.3)

•Congenital absence of the lens, an abnormally small lens, or an irregular lens shape may result from developmental abnormalities affecting the orientation, induction and separation of the lens vesicle. Microphakia and irregularities of lens shape can be seen alone or, more often, as a part of a syndrome of developmental abnormalities involving the anterior segment of the globe

•Diffuse or focal lack of zonular tension at the lens equator may result in spherophakia or so-called lens coloboma respectively. These abnormalities in lens shape probably do not represent primary abnormalities in lens development, rather they are associated with anterior segment developmental abnormalities that affect the ciliary processes and zonular integrity.

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Congenital cataract (Figs 10.4, 10.5)

•Morphologic features which typify congenital cataract include:

■Cataractous changes in the lens nucleus characterized by an abnormal position of the nucleus or lysis of the nucleus

■Abnormal relationship between the epithelium and lens capsule such as duplication, wrinkling, or segmental changes

■Posterior migration of lens epithelial cells

■Vascular or pigmented structures adherent to the lens capsule might indicate a cataract associated with

abnormal development of the fetal vasculature (persistent pupillary membranes, persistent hyperplastic primary vitreous, or persistent hyperplastic tunica vasculosa lentis)

•Congenital cataract and associated ocular abnormalities, that may include microphthalmia syndromes and abnormalities in the fetal hyaloid vasculature, are described in detail in Chapter 3.

Comparative Comments

•In man, as in animals, in addition to the congenital and hereditary abnormalities, primary aphakia with complete failure of lens formation has been reported in rare instances. More commonly, a small or incompletely formed lens, giving the clinical impression of aphakia, has been observed

•Other congenital abnormalities that are also seen the human lens include conditions of imperfect or delayed lens-corneal separation, anterior lenticonus, and spherophakia. In the latter condition, the lens is relatively more rounded than normal and usually smaller (microphakic)

•An important congenital condition in humans is rubella cataract, which occurs in the fetus if the mother is exposed to rubella virus during the first or second trimester of pregnancy. Rubella virus may be cultured from surgically removed lenses

•Although tumors of the lens do not occur in humans, the lens anlage has been reported to develop aberrantly in the lower lid, in a condition known as phakomatous choristoma.

CATARACT

•Cataract is the pathological opacification of the lens including its capsule

•Cataract may be categorized according to extent of lens involvement, location within the lens, or etiopathogenesis.

Cataract categorized by the extent of disease (Figs 10.6–10.10)

•Incipient cataracts involve less than 15% of the lens

•Immature cataracts affect more than 15% of the lens but lens involvement is incomplete and they do not completely obscure the fundus reflection

•Mature cataracts affect the lens cortex circumferentially and completely obstruct visualization of the fundus reflection

•Hypermature cataracts show evidence of lens shrinkage, such as lens capsule wrinkling, associated with leakage and resorption of altered cortical lens proteins.

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Cortical cataract, the opacification of the lens fiber (Fig. 10.11)

•There is not a perfect correlation between the clinical observation of lens opacity and a histologically observable morphologic change in the lens cortex

■Many changes in the lens protein can represent either genuine pathology or artifact of processing. Therefore, it may be impossible to determine the significance of observed morphologic changes

■Reliable morphologic indicators of cortical cataract include:

–Bladder cells: swollen, rounded lens fibers that still contain a nucleus

–Morgagnian globules: swollen, rounded lens fibers with no nucleus

■Lens mineralization may occur in long-standing cataracts.

Subcapsular cataract, opacification and metaplasia of the lens epithelial cell (Fig. 10.12)

•Normal lens epithelial cells are positioned immediately adjacent to the lens capsule and their tropism for the lens capsule is seldom altered in disease states

•In subcapsular cataract the opacity is directly related to abnormalities of the lens epithelial cells

•Morphologic features of subcapsular cataract include:

■Proliferation of lens epithelial cells to form a localized aggregate

■Metaplasia, involving a change in the cells from an epithelial phenotype to a mesenchymal phenotype more characteristic of a myofibroblast

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■Secretion of collagen around the metaplastic lens epithelial cells

■Loss of the lens epithelial cells leaving behind cell-free collagen matrix

■Mineralization.

Inherited cataract in dogs

•Inherited cataract is very common in the purebred canine population. An inherited basis for cataract development is proven or suspected in over 100 canine breeds, of which many appear to demonstrate complex patterns of inheritance. In some canine breeds, a genetic basis for cataract development has been clearly established, e.g. mutations in the HSF4 gene are associated with early-onset cataract in several breeds, including the Staffordshire bull terrier and Boston Terrier

•Clinical phenotype is highly variable between and within affected breeds. This variability may result from the influence of multiple genes and other metabolic and environmental factors.

Age-related cataract

•Cataracts are a common feature of senescence in most species

•Senile cataracts should be distinguished, both clinically and histomorphologically, from the normal process of nuclear sclerosis which is not associated with true lens opacity

•In nuclear sclerosis, the density of the lens nucleus increases with age as older lens fibers are progressively tightly packed centrally and take on a more homogeneous in appearance, as new cortical fibers are formed more peripherally.

Secondary cataract

•Cataract may occur secondary to other intraocular disease; such as uveitis, glaucoma, neoplasia or advanced retinal degeneration; or as a result of trauma, electrocution, nutritional imbalance, exposure to toxins or metabolic disease, such as diabetes mellitus.

•Metabolic cataract is recognized in almost all diabetic dogs (Fig. 10.10)

■Diabetic dogs are far more likely to develop cortical cataract because of the conversion of glucose to sorbitol within the lens cells and the resulting influx of water

■Diabetic cataracts often develop rapidly and can lead to serious inflammatory changes if the lens capsule ruptures (see below) or to secondary glaucoma caused by lens swelling (intumescent cataract)

■The diabetic state can also contribute to complications following cataract surgery

–In general, however, substantial differences in postoperative outcomes are not apparent compared to non-diabetic dogs

■Although diabetic cataracts are usually cortical cataracts, there are no specific morphologic features which allow a diabetic

cataract to be distinguished from any other cortical cataract morphologically

■Although diabetes mellitus is fairly common in cats and humans, diabetic cataract is not common in these species

–The lower incidence of diabetic cataract in cats may relate to lower levels of activity of the enzyme aldose reductase in the lens of older cats, compared to dogs.

Comparative Comments

•The types of cataracts occurring in humans and other species appear to be extremely similar, although they have been further subdivided into a greater number of types in humans

•An extremely interesting entity is the exfoliation syndrome, also known as pseudoexfoliation, in which a fibrillary protein-like material is deposited on the anterior lens capsule

•The major systemic disorders associated with cataract development in humans are diabetes mellitus, galactosemia, hypercupremia, Fabry disease and Down syndrome

•Numerous drugs give rise to cataracts in humans, the most common being corticosteroids.

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