Year : 1983 | Volume
: 31 | Issue : 3 | Page : 143--148
A new look at some macular lesions
Department of Ophthalmology, University of Toronto, Canada
P K Basu
Department of Ophthalmology, University of Toronto 1 Spadina Crescent Toronto, Ontario M5S 2J5
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Basu P K. A new look at some macular lesions.Indian J Ophthalmol 1983;31:143-148
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Basu P K. A new look at some macular lesions. Indian J Ophthalmol [serial online] 1983 [cited 2013 Jun 19 ];31:143-148
Available from: http://www.ijo.in/text.asp?1983/31/3/143/29770
The observation of the retinal surface plays an important role in the study of the retinal pathology. Ophthalmologists are accustomed to survey the retinal surface with an ophthal moscope Ophthalmic pathologists can examine the retinal surface at a higher magnification using a dissecting microscope. However, the retinal surface can be visualised at a much higher magnification by the Scanning Electron Microscope (SEM). The SEM can reveal details of the tissue surface changes that cannot be so readily studied by any other methods. The use of light microscopy and transmission electron, microscopy for studying the topograpy of a tissue is cumbersome and time consuming as it requires an examination of a very large number of serial sections.
Very little work has been done for studying the ultrastructural features of the surfaces of the diseased human retina using the SEM. , The purpose of this report is to illustrate the usefulness of the SEM for topographical studies on pathological retinas.
Methods and Materials
The right eye of a 9 year old boy suspected of having toxoplasmosis, and right eye of a 70 year old woman having a definite history of retinitis pigmentosa were obtained through the courtesy of the Eye Bank of Canada (Ontario Division).
The boy (Case No. 1) had a history of myocarditis and died of cardiorespiratory failure apparently due to a brain-stern lesion (communicating hydrocephalus). Immediately prior to death no ophthalmoscopic examination was done. However, ophthalmoscopic examination done one year before death gave an anatomical diagnosis of "Chorioretinitis possible due to toxoplasmosis" in the left eye. Apparently, the right eye was found to be free from any ocular lesions. (Dr. C. Dyson, Personal Communication). The woman (Case No. 2) who had advanced dominant type of retinitis pigmentosa in both eyes (Dr. H.R. Sniderman, Personal Communication) died of heart failure.
Both donor eyes were processed for the SEM within 8 hours of death. After opening each eye by a saggital section through the ora serrata the lens and as much of the vitreous humour as possible were removed by cutting with scissors. The remaining vitreous humour was removed by a thorough washing with phosphate buffered saline (PBS).
Under a sterioscopic dissecting microscope, no gross pathological changes were discernable in the retina of the first case. In the second case, the retina was bespecked with pigmented areas both centrally and peripherally.
Pieces (about 1 cm') of the retina together with the underlying choroid and sclera were then cut from various areas of the eye. The tissue samples were processed for the SEM by the methods described previously. ,
For observing the posterior surface of the neural retina the tissue samples were placed with its inner surface down on a cover slip. For visualizing the retinal pigment epithelium (RPE), the piece of the neural retin was removed, thus exposing the RPE. The Bruch's membrane was observed through the spontaneous break in the RPE and no manipulation was done to expose this layer.
Case No. 1
The SEM showed the presence of severa "holes" in the central retina (F.g. 1). Opening., of some of these holes were funnel shaped [Figure 1]b and some were tubular [Figure 1]c. All holes had clear-cut rims without any signs of break of laceration. Some holes had the feature similar to that observed by Gettinger (1977) in retinas with cystoid degeneration of the peripheral retina. Cable-like strands of tissues traversed some holes [Figure 1]b,c. These strands might be fine blood vessels, fibres of collagenous tissue and/or stretched neural processes. Sorne holes appeared to be supported by columnet structures [Figure 1]c. A few red blood cells were observed in association with some of the holes [Figure 1]c. At the bottom of one hole, the mosaic pattern of the retinal pigment epithelium (RPE) could be seen. This was evidently a hole penetrating the full-thickness of the neural retina.
Concentric to the margin of a funnel-shaped hole [Figure 1] a, d, peculiar crystalline deposits were seen. The nature and significance of these deposits are unknown at present.
Case No. 2
In this retina, extensive areas of "erosion" of the retinal surface were seen not only in the peripheral retina but also in the macular area. This resulted in the exposure of the deeper layers of the tissue. [Figure 2], b-c. Pigment granules were heaped up at many places [Figure 2] a, d. As shown in [Figure 2] e, in some places, epiretinal membrane formations were seen. Broken cells loaded with pigment granular (probably macrophages) were seen on the retinal surface [Figure 2] f. Rods and cones were severely damaged leaving large areas devoid of these structures [Figure 3]. There were also changes in the retinal pigment epithelial cells in terms of their shape, size and microvilli [Figure 4] a-d. Areas of the Bruch's membrane contained free pigment granules which lay at different levels of the collagenous fibres of the lamina elastica [Figure 5].
In order to visualize the inner surface of the retina by the SEM, it is important to remove as much of the vitreous humour as possible from the surface. This was achieved by a thorough rinsing of the retina with PBS.
Surface abnormalities that were invisible by the dissecting microscope (Case No. 1) were seen with the use of the SEM. The SEM showed the depths and contents of the partial and full thickness retinal lesions in three dimensions. The morphology and distribution of peculiar crystalline depsoits on localized areas of the central retinal surface were intriguing. One wonders whether the deposit could be related to a local vitreous abnormality.
The novelty of the present work lies in the fact that the SEM study of the retina is a new speciality. This study showed certain details of retinal lesions in patients with toxoplasn osis and retinitis pigmentosa which do not appear to have been reported before.
In order to visualize the surfaces of pathological human retinas, scanning electron microscopy (SEM) was used. One retina came from a boy of 9 having toxoplasmosis and another retina came from a woman of 70 having retinitis pigmentosa. The SEM demonstrated in three dimensions various structural changes that occurred in these retinas, which could not have been detected so convincingly by any other methods.
This work was supported by grants from the Medical Research Council of Canada and the Lions' International District A-16 Ophthalmologica! Research Foundation. Mr. K. Schultes, Department of Microbiology and Parasitology, Mr. P. Lea, Electronmicroscopy Unit, Faculty of Medicine and Mr. E. Lin, Department of Zoology, University of Toronto gave technical assistance.
I am thankful to the Canadian Retinitis Pigmentosa Foundation and the Eye Bank of Canada (Ontario Division) for their interest in this work.
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