Martin Davanger

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.

PSEUDO-EXFOLIATION MATERIAL ON THE ANTERIOR LENS SURFACE. DEMONSTRATION AND EXAMINATION OF AN INTERFIBRILLAR GROUND SUBSTANCE

Peroxidase did not penetrate into the capsule of cataractous lenses with or without pseudo‐exfoliation (PE). Neither did this tracer penetrate into the PE material itself, indicating that the PE fibrils are embedded in a ground substance which is impenetrable to peroxidase. Staining with alcian blue and ruthenium red showed that this ground substance is structurally heterogeneous. Acid mucopolysaccharides and/or glycoproteins are probably present. The fibrils are coated by a material with affinity to ruthenium red. This applies also to the fibrils of the amorphous layer. Their diameter is only about 1/3 of the fibrils of the PE material on the lens surface. Rounded membrane‐covered bodies are present, partly in groups, in the PE material. Morphologically, they resemble the mucopolysaccharide‐containing lysosomal vacuoles found in systemic mucopolysaccharidoses. Observations supporting the conception of similarities between PE material and amyloid are pointed out. The pathogenesis of the PE material is discussed.

The healing of rabbit corneal endothelium.

A circular 4 mm endothelial defect was induced by transcorneal freezing. The experimental damage and the healing took place in the living rabbit in 15 eyes, and in the isolated cornea in organ culture in further 20 eyes. The reparative process was studied by SEM, and proved to be the same in vivo and in vitro. The defect was covered with endothelial cells after 3 days. The normal hexagonal pattern was regained after 3 weeks. Both cell migration and cell division were involved in the reparative process. Only cells recruited from a zone close to the defect were active; the cells situated more than a few cell diameters from the original edge maintained their form and size unchanged. The first phase of cell division was the formation of a spherical cell with numerous blebs on its surface.

The probability of having glaucoma at different IOP levels

Abstract The probability of having glaucoma is indicated by the quotient (number of eyes with glaucoma)/(number of eyes in the total population). This quotient was calculated for each value of IOP. The number of eyes at each IOP value was taken from IOP frequency distribution curves for glaucomatous and normal eyes, calculated from values obtained by a population survey. By plotting the probability of having glaucoma vs IOP, a sigmoid curve was obtained. The curve indicates that while the glaucoma probability is near zero at IOP = 18 mmHg, it is 0.5 at 27–28 mmHg, and the probability approaches 1, i.e. certainty, at an IOP around 35 mmHg. The frequency distribution of the tolerance limit of IOP was calculated by derivation of this curve. The distribution of IOP tolerance limit was close to a normal distribution with average = 27.9 mmHg and standard deviation = 3.2 mmHg.

Risk factors for an inflammatory response after extracapsular cataract extraction and posterior chamber IOL

Abstract. Risk factors for developing an inflammatory response after extracapsular cataract extraction with implantation of posterior chamber IOL have been studied. Out of 1154 cases included in the study, an inflammatory response was encountered in 63 eyes (5.5%). The inflammatory response was defined as increased cellular flare and/or as a fibrinous reaction during a follow‐up of 4 months. Thirteen of the 63 eyes (20.6%) developed cellular precipitates, and posterior synechias were seen in 34 of these eyes (54.0%). Among 10 pre‐ and 10 peroperative putative risk factors analyzed in a logistic regression model, 5 variables had a statistically significant influence on the probability of developing postoperative inflammation; 1) Uveitis in history (p = 0.0001), 2) Pseudo‐exfoliation syndrome (p = 0.0224), 3) Inability to obtain adequate mydriasis at the start of surgery (p < 0.0001), 4) Problems with IOL implantation (p = 0.0111) and 5) Pigment effusion during surgery (p = 0.0258).

Pseudoexfoliation syndrome and extracapsular cataract extraction.

Abstract. Extracapsular cataract extraction (ECCE) in 139 eyes with pseudoexfoliation syndrome was compared to 762 eyes without pseudoexfoliation syndrome in a consecutive study. Preoperative findings, operative procedure and problems were registered, stored and analyzed in a computer program package. Of the patients with pseudoexfoliation syndrome 88.5% were 70 years or older, compared to 67.2% of the patients without pseudoexfoliation syndrome (p < 0.001). Glaucoma occurred in 48.9% of eyes with pseudoexfoliation syndrome and in 6.8% of eyes without pseudoexfoliation syndrome, respectively. Poorly dilated pupil was demonstrated in 46.8% and in 5.8% of eyes with and without pseudoexfoliation syndrome, respectively. Capsule/zonulae tears (without vitreous loss) occurred in 4.3% of the pseudoexfoliation syndrome eyes, compared to 1.3% in eyes without pseudoexfoliation syndrome (p < 0.05). The incidence of vitreous loss was similar in both groups. We found no correlation between the pupil size and capsule/zonulae tears or vitreous loss in either group. In conclusion, when appropriate care is undertaken, ECCE with posterior chamber IOL implantation is a safe procedure in pseudoexfoliation syndrome eyes.

Results and complications after extracapsular cataract extraction in eyes with pseudoexfoliation syndrome

Abstract. Postoperative results and complications in 136 eyes with pseudoexfoliation syndrome were compared to 744 eyes without pseudoexfoliation syndrome in a consecutive study. The patients were followed for 4 months postoperatively. Excluding cases with glaucoma, 81.4% of the pseudoexfoliation eyes and 83.0% of the eyes without pseudoexfoliation achieved a corrected visual acuity of 5/8.5 or better. IOL malposition was rare in both groups (1.5% in the pseudoexfoliation group and 1.6% in the group without pseudoexfoliation). IOP elevation the first day postoperatively occurred most often in the pseudoexfoliation eyes. In the pseudoexfoliation eyes, postoperative iritis and cellular precipitates were demonstrated in 16.2% and 11.0%, respectively, compared to 3.8% and 3.2% in the eyes without pseudoexfoliation (p < 0.001). The frequency of an inflammatory reaction was highly correlated to small pupil size during operation in both groups.

Changes in the rabbit corneal stroma caused by UV-radiation

Abstract. Three days after UV‐irradiation of the rabbit cornea, there was epithelial loss and stromal oedema, which was most prominent in the anterior 1/4. Many of the keratocytes in this region were killed. The inner 3/4 of the stroma showed a large number of round or oval cells with nuclear fragmentation and abnormal inclusions. These cells were taken to be seriously, though reversibly harmed keratocytes. The tissue structure was normalized within one week, and the UV‐induced changes seem to refer to the 290–350 nm interval.

On the molecular composition and physico-chemical properties of the pseudo-exfoliation material.

The protein tracer peroxidase has been found to be excluded from pseudo‐exfoliation (PE) material. But after the treatment of the PE material with cetylpyridinium‐chloride, peroxidase was found to penetrate into the material. This observation seems to support the concept that the PE material is a gel of proteoglycans, from which peroxidase is excluded by an excluded volume effect.