Amund Ringvold

THE MIDDLE-NORWAY EYE-SCREENING STUDY. I. EPIDEMIOLOGY OF THE PSEUDO-EXFOLIATION SYNDROME

Abstract. This is the first population‐based PE prevalence study allowing comparison of observations from different geographical areas. The prevalence of the PE syndrome for persons above 64 years of age was found to be 10.2, 21.0 and 19.6% in three municipalities lying distinctly apart. Of 343 married couples the man was PE‐positive in 36, the woman in 34, and both in 12 cases. One of the 12 couples was excluded because the spouses were cousins. The observed number of 11 couples is significantly higher (P = 0.022) than expected assuming independent occurrence of PE syndrome. Two homozygote pairs of twins were found in this material, both of them discordant for the presence of PE syndrome. This fact along with the discrepancy between observed and expected numbers of PE positivity in both spouses may indicate environmental influence on the distribution of the syndrome.

The Middle-Norway eye-screening study: II. Prevalence of simple and capsular glaucoma

Abstract In this population‐based screening study, dealing with 1941 persons above 64 years of age from three different municipalities, the overall open‐angle glaucoma prevalence was found to be 8.3%. The prevalence in the separate areas (7.0%, 8.6%, and 9.5%) were not statistically different. Roughly 30% of the population with pseudo‐exfoliation syndrome had glaucoma, and 4.2% had ocular hypertension, whereas the corresponding figures for those without pseudo‐exfoliation were 4% and 0.8%, respectively. The high glaucoma rates are partly due to the high pseudo‐exfoliation prevalence in the area. The prevalence of the capsular glaucoma increased towards a maximum between 75 and 79 years of age, whereafter the curve declined. This may indicate reduced survival time of glaucomatous patients.

ON THE OCCURRENCE OF PSEUDO-EXFOLIATION MATERIAL IN EXTRABULBAR TISSUE FROM PATIENTS WITH PSEUDO-EXFOLIATION SYNDROME OF THE EYE

The present communication demonstrates pseudo‐exfoliation material in the palpebral conjunctiva of patients with pseudo‐exfoliation syndrome of the eye as determined by slit lamp examination. Biopsies of the skin or the oral mucous membrane of these patients did not reveal pseudo‐exfoliation material by electron microscopic investigation. Such material was also absent in conjunctival biopsies from patients without pseudo‐exfoliation syndrome of the eye. It is concluded that the pseudo‐exfoliation material in the mucous membrane of the eyelids is obviously not transported into this region from the intraocular space, and hence the occurrence of such material in this location indicates that pseudo‐exfoliation material is synthesized both in ocular and in extrabulbar tissue in patients with pseudo‐exfoliation syndrome of the eye.

Ascorbic acid concentration is reduced in the aqueous humor of patients with exfoliation syndrome

PURPOSE To investigate whether there is a role for ascorbic acid in the development of exfoliation syndrome (XFS). DESIGN A case-control study was undertaken that included consecutive patients with and without XFS in whom cataract surgery was indicated. Patients with ophthalmic conditions other than XFS and conditions that may influence ascorbic acid levels were excluded. METHODS A prospective institutional study was undertaken. A small volume of aqueous humor was aspirated at the beginning of phacoemulsification cataract surgery. Eighty aqueous samples, 40 samples from 40 eyes of 40 cataract patients with XFS and 40 samples from 40 eyes of 40 age matched cataract patients without XFS, were collected and analyzed. Ascorbic acid concentration was evaluated in the aqueous samples with a microplate assay method. RESULTS The mean +/- SD concentration of ascorbic acid in the aqueous from patients with XFS (0.86 +/- 0.43 mM; range, 0.12 to 1.7 mM) was significantly lower than the concentration of ascorbic acid found in the aqueous of age-matched control patients (1.15 +/- 0.50 mM; range 0.42 to 3.1 mM; P =.0068). Total mean protein concentration was found to be significantly higher in the XFS group (481.1 +/- 196.8 pg/dl versus 336.3 +/- 86.4 pg/dl in the controls; P <.0001). Nevertheless, no correlation could be established between ascorbic level and protein concentration. CONCLUSIONS A significantly reduced mean level of ascorbic acid was observed in the aqueous humor of patients with XFS. In view of the fact that ascorbic acid is a major protective factor against free radical action, a role for free radical action is possible in the pathobiology of XFS.

CHANGES OF THE CORNEA ENDOTHELIUM AFTER ULTRAVIOLET RADIATION

The rabbit cornea endothelium has been studied with specular and scanning electron microscopy after exposure with a commercially available ultraviolet lamp. The animals were plased 50 cm from the source, and most experiments were run with a 20 min exposure time. In the specular microscope, the endothelium revealed numerous circumscript reflex‐free areas, which were observed from 4 days up to 8 months after the irradiation. A wide varity of changes were found in the scanning electron microscope. One day after the exposure the cells showed indistinct outlines, and they were bulging into the anterior chamber. In some regions the pattern was dominated by marked grooves preferentially along the cell demarcations, whereas other regions showed rough surfaced cells because of cytoplasmic projections and grainy deposits. At the 3 days stage there was a marked pleomorphy, and some cells were on their way to being rejected. After one week the cobblestone appearance of the endothelium was about to decline. Partly rejected cells were still common. In addition, distinct, ringshaped local impressions occurred imitating the previous described grooves. This phenomenon along with some single endothelial cells studded with microvilli were the abnormal findings 8 months after the damage. It is concluded that although ultraviolet radiation is largely absorbed in the cornea, the threshold dose for damage of the endothelium is not beyond those used for practical purpose. The endothelium was surprisingly resistent towards repeated radiation damage.

Pseudo-exfoliation, IOP and glaucoma

Abstract On the basis of a glaucoma survey in a total population ≥ 65 years of age, the IOP in eyes with and without pseudo‐exfoliation (PE) has been compared. The average IOP was 22.2 mmHg in eyes with PE versus 17.4 in eyes without. The corresponding averages in eyes without glaucomatous damage were 18.6 and 17.1 mmHg, and in eyes with glaucoma 31.5 and 25.5 mmHg. The IOP elevation connected with the PE process was 4.8, 1.5, and 6.0 mmHg in the total, normal and glaucomatous population, respectively. The IOP frequency distribution curves of these 3 groups were compared. The right shift of the distribution curves of the PE groups was more pronounced at high pressure levels. The PE process seems to elevate the IOP particularly in eyes with a high IOP, which is in correspondance with hydrodynamical laws. At a certain IOP, the probability of having glaucomatous damage was higher in eyes with PE than in those without, indicating an increased vulnerability of PE eyes to an elevated IOP. PE may be a glaucoma risk factor also on its own, i.e. independent of the pressure elevation connected with this syndrome.

Electron microscopy of the limbal conjunctiva in eyes with pseudo-exfoliation syndrome (PE syndrome)

The limbal conjunctiva of five human eyes was studied. All eyes showed PE material in the anterior segment by slit-lamp examination. Additionally, electron microscopy of the limbal conjunctiva revealed aggregates of PE material in the connective tissue and within vessel walls. Furthermore, the basement membrane zone of vessels was often disorganized. The demonstration of PE material beyond the intraocular space perhaps indicates that the PE syndrome is of a more general nature than hitherto believed.

CORNEA AND ULTRAVIOLET RADIATION

The absorption of ultraviolet radiation in the cornea of rabbit, cat, guinea pig, and rat has been studied. It turned out that about 80% of incident radiation is absorbed at the 290 nm wavelength limit in rabbit and cat, whereas the absorption is considerably lower in guinea pig and rat. In a model experiment based on conditions in the rabbit cornea epithelium, it is shown that the ascorbic acid in these cells is roughly responsible for ultraviolet ray absorption of the same order as proteins and nucleic acids in the 250–290 nm spectral range. This implies that for radiation below 290 nm wavelength also the ascorbic acid should be regarded as a potential target substance which may mediate photophthalmic damage to the tissue. The low absorption of the ascorbic acid compared to the other two components above 290 nm, indicates that the ascorbic acid contributes less in photophthalmic development due to solar radiation.

Electron microscopy of the trabecular meshwork in eyes with exfoliation syndrome (pseudoexfoliation of the lens capsule)

The trabecular meshwork of three human eyes involved with the exfoliation syndrome were studied. The intraocular tension in the eyes represented successive stages. Exfoliation material was found in all three eyes: In Eye 1 (no glaucoma) only in intertrabecular spaces, in Eyes 2 and 3 also within trabecular beams and in the juxtacanalicular tissue. In addition, abnormal basement membranes were revealed. In Eye 3 (uncontrollable glaucoma), the disorganized trabecular meshwork contained increased amounts of connective tissue elements as well as small vessels. The concept is advanced that the accumulation of exfoliation material in the meshwork impedes aqueous outflow and thus is a pathogenetic factor of importance in glaucoma capsulare.

Ultrastructure of the wall of human iris vessels

Summary1.The walls of iris vessels in five human eyes were studied.2.No fenestrae are present in capillary endothelium.3.A several thousand Å thick basement membrane is found in practically all vessels. The basement membrane is often multi-layered and its external limit irregular.4.A distinct zone of thin collagen fibrils is present between the “inner” and “outer tube” in almost all vessels.5.Membrane-bounded, moderately dense bodies about 0.3 μ in diameter are concentrated among the extracellular components of vessel walls.6.Muscular tissue is scanty.7.No elastic fibres are found.