pigment granules in iris pigment epithelium of diabetics


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    Reykjavlk, Iceland, 20-24 June 1971

    From the Department of Anatomy (Head: I;. Bierring), University of Odense, Denmark and

    the Debartment of Obhthalmology (Heads: P. M . Mdler and E. Goldschmidt), Odense, Denmark




    The iris pigment epithelium of four diabetics has been studied with special reference to its fine structure. Some of the pigment granules were seen to have undergone changes, being apparently in a state of disintegration. Further, accumulation of glycogen was noticed in the cells and in the intercellular spaces.

    Keywords: iris - pigment epithelium - diabetes - glycogen - melanin granules.

    Diabetic iriopathy is a well-known phenomenon, described as early as the end of the nineteenth century (Kamocki 1887). Especially the pigment epi- thelium on the posterior surface of the iris displays characteristic changes e.g. lacy vacuolation. These changes can be observed clinically and light-micro- scopically. The iris pigment epithelium of four diabetics has been examined, and certain results of electron microscopy will be reported below.

    The composition of the series is shown in Table I, where the estimated dura- tion of the disease also is stated for the individual patient. Further, it is seen in the table that in two cases the specimen studied was from a biopsy of iris removed in connection with cataract extraction, while in the two others the iris specimen came from enucleated eyes.


  • Table I . ~

    Patient Duration of code Sex Age diabetes (years)

    Pigment granule Remarks concerning Clinical observations specimens in iris changes

    A male 25 7 enucleation owing to uveal melanoma

    B male 28 2 iris biopsy specimen excised at cataract operation

    C female 34 14 iris biopsy specimen excised at cataract operation

    intractable haemorrhagic glaucoma

    D female 52 24 enucleation owing to

    mild atrophy of pigment epithelium

    mild atrophy of pigment epithelium

    mild atrophy of pigment epithelium

    grave atrophy of pigment epithelium

    only scattered changes

    scattered changes

    fairly extensive changes

    extensive changes

  • J. Hvidberg-Hansen

    All the specimens obtained were immediately fixed in cacodylate-buffered 4 O/O glutaraldehyde. Then followed postfixation in osmium tetroxide and, after dehydration, embedding in araldite.

    From patient A iris tissue was taken for glycogen digestion, the glutaralde- hyde-fixed block having been incubated in amylase (2 mg/ml) for 15-30 minutes at 37' (Thornell 1969) prior to osmium fixation.

    Further, iris tissue from the same patient was subjected to ribonuclease digestion. Control specimens were in both cases incubated without addition of enzyme.

    A JEM T 7 electron microscope was used for electron microscopy. In ad- dition, semifine sections were subjected to light microscopy.

    In the present communication only fine-structural changes will be commented on, and even only in as far as such changes served to distinguish the pigment

    Fig. 1. Survey of pigment epithelium in diabetic patient. Intracellular glycogen accumulation is marked by asterisks and intercellular glycogen accumulation by arrows. PC: posterior chamber, N: nucleus in pigment epithelium, and D: nucleus in dilatator muscle cell.

    10 microns indicated.


  • Iris Pigment Epithelium in Diabetics

    epithelium of diabetics from that of 16 non-diabetic controls (J. Hvidberg- Hansen 1971).

    That which in the first place attracted attention was observathon of some changes in the pigment granules (Figs. 3 and 4). Such changes have not been noticed on examination of non-diabetics, though the pigment configuration displays certain variations. The changes, which might create the illusion of disintegration of the pigment granules, were noticed in all four diabetics, though in different degrees, cf. Table I. A fairly small proportion only of the pigment granules had changed. These often lay in groups typically situated close to the cell boundary bordering on the posterior chamber. Within the cir- cumference of the disintegrated granules the cytoplasm was found to contain electron-opaque particles, which seemed to correspond to the contents of the pigment granules. These particles remained uninfluenced by amylase and ribo- nuclease.

    Fig. 2. Section of pigment epithelium after amylase treatment. Large areas between the pig- ment granules and the intercellular spaces (F) are empty, unlike the conditions without amylase treatment. P marks an abnormal pigment granule and L a droplet of lipid.

    3 microns indicated.


  • J . Hvidberg-Hansen

    Fig. 3. Survey of pigment epithelium with abnormal pigment granules in a diabetic. A thickened basal membrane is seen towards the posterior chamber (PC). Nucleus in

    dilatator muscle marked D. 4 microns indicated.

    Note that under the membrane enclosing the normal corfigurated pigment granules we find particles resembling glycogen particles, which become de- composed by amylase, but not by ribonuclease (Fig. 5) . Such were also observed in non-diabetics, and there seems to be neither a quantitative nor a qualitative difference within this special field.

    A great number of glycogen-like granules was found in the pigment epithe- lium from the four diabetics. Be it mentioned that amylase-decomposable glycogen also is present in non-diabetics, though in smaller amounts than those observed in the diabetics.

    Similarly as in non-diabetics, the glycogen granules were located both intra- and intercellularly (Fig. 1). The results of the enzymatic study bore out the presumption of glycogen content in and between the epithelial cells (Figs. 2 and 5) .

    None of the diabetic patients presented any pronounced vacuolisation in the cells.


  • Iris Pigment Efiithelium in Diabetics

    Fig. 4. Abnormal pigment granules (segment of Fig. 3). Some granules (arrow) seem to be in a state of disintegration from within, while others give the impression of being in a state of erosion from without (asterisk). In the cytoplasm electrondense, irregular

    particles are visible, which seem to be pigment debris. (P). 1 micron indicated.

    Yanoff, Fine & Berkow (1970) subjected an autopsy material to an electron- microscopical study to disclose changes in the pigment epithelial cells on the posterior surface of the iris in relation to diabetes. Glycogen was found in ill- defined, nearly empty vacuoles in the cells, and, in addition, a non-identified material. The appearance of the pigment granules has not been described in detail. Hollenberg, Nayyar & Burt (1968) and Hollenberg & Burt (1969), who examined the retinal pigment epithelium of rats in the presence of diabetes, likewise made no mention of pigment granule changes.

    Feeny, Grieshaber & Hogan (1965) have studied human ocular pigment and described individual variations in appearance of the pigment granules of iris epithelium. They found, among other things, a fairly loose configuration in a single case. Similar variations were also noticed in normal series, but changes like those illustrated were not observed.


  • J . Hvidberg-Hansen

    Fig. 5. Pigmented epithelial cell section from diabetic. a without enzymatic treatment, showing glycogen-like granules at asterisk and in intercellular space (I). Glycogen-like particles are seen at the arrow. These are located under the membrane bounding the granule. b shows the conditions after amylase digestion. Glycogen granules are seen neither in the cytoplasm nor in relation to the pigment granules. c illustrates the conditions after ribonuclease treatment. The preserved glycogen granules are here situated as in a. Note especially at the arrow particles under the membrane bounding the pigment granule. R represents rough endoplasmatic reticulm deprived of ribosomes. Magnifica-

    tions equal in all three cases. 1.5 microns indicated.

    Glycogen is a normal constituent of the iris epithelial cells (Berkow & Fine 1970). A possible correlation between the vacuolisation and the increasing gly- cogen accumulation in diabetes should doubtless be considered.

    Translucency of the pigment epithelium is a characteristic clinical feature of diabetes. As shown in Fig. 1, a cell region displaying such a greatly reduced pigment content and at the same time accumulation of glycogen will' possibly render the pigment epithelium translucent.

    The series under review allows of no conclusions as to whether the changes in the pigment granules observed are specific of diabetes. I t is surprising, how- ever, that such changes were present in all the cases examined, though in dif- ferent degrees.

    The well-known operative pigment liberation in diabetics, which presumably is attributable to change of the pigment epithelium, possibly bears relation to the above findings.


  • Iris Pigment Epithelium in Diabetics


    Berkow, J. W. & Fine, B. S. (1970) Glycogen in normal human iris pigment epithelium. Amer. J . Ophthal. 69, 994-996.

    Feeny, L., Grieshaber, J. A. & Hogan, M. J. (1965) Studies on human ocular pigment. In: Rohen, J. W., ed. (1965). Eye Structure 11, pp. 535-548, Schattauer Verlag, Stutt- gart.

    Hollenberg, M. J. & Burt, W. L. (1969) The fine structure of Bruchs membrane in the human eye. Canad. J . Ophthal. 4 , 296-306.

    Hollenberg, M. S., Nayyar, R. P. & Burt, W. L. (1968) Histochemical and electron microscopic studies of the retinal pigment epithelium in the normal