Regeneration of epithelial defects in corneas previously treated with excimer laser. A study of cell kinetics in the rat corneal epithelium.

PURPOSE: The present study was to investigate, using cell kinetic methods, whether previous excimer laser treatment affected healing of later corneal epithelial erosions. METHODS: The right eyes of rats underwent central excimer corneal stromal-epithelial ablations (ArF 193 nm, 228 pulses, diameter 3,5 mm, 17,3 mJ per pulse, depth about one third of corneal thickness) and were allowed to heal for 15 weeks. Then central circular epithelial abrasions (diameter 3 mm), using N-Heptanol and mechanical debridement, were made on both corneas. The rats were killed 1,2,4 and 6 days after the last treatment. The central stromal thickness, the epithelial cell density, the labelling index (LI) and the mitotic rate (MR) of the peripheral, the midperipheral and the central areas of the corneal epithelium were calculated for each timepoint. RESULTS: The central stromal thickness increased equally in the two groups the first day after making the erosion, normalising in both groups during the following days. The corneal epithelium was restored at the same rate in both groups. The cell number per microscopic visual field, the LI and the MR were very similar for the two groups at all timepoints. CONCLUSION: Previous excimer laser treatment does not seem to interfere with healing of later epithelial erosions, when studied with cell kinetic methods.

Pseudo-exfoliation and mortality.

The hypothesis that ocular pseudo-exfoliation syndrome is part of a generalized disorder has been tested by suggesting that subjects having this syndrome would have increased mortality. However, no association was found between presence of ocular pseudo-exfoliation syndrome and mortality.

Epithelial wound healing of the rat cornea after excimer laser ablation.

Rats with excimer corneal ablations (ArF 193 nm, 228 pulses, diameter 3,5 mm, 17.3 mJ per pulse, depth about 1/2 of corneal thickness) in one eye were killed 1, 2, 4, 6 and 13 days after treatment. The other eye served as control. The cell number per microscopic vision field, the labelling index (LI) and the mitotic rate (MR) were calculated for the peripheral, midperipheral and central areas of the corneal epithelium. The cell number showed a uniform depression in the remaining corneal epithelium at Day 1, normalizing from the centre to the periphery. The LI was only significantly increased at Day 1, while the MR was statistically significantly increased peripherally at Day 2 and in all areas at Day 6. However, when the corneal epithelium was evaluated as a whole, the MR was significantly increased at days 1, 2 and 6. The proliferative response of the epithelium was very homogenous irregardless of the distance to the original lesion. Both the migratory and the proliferative phases of the healing process seemed to be delayed when compared to the healing of pure epithelial wounds. However, the initiation of an increase in DNA synthesis seems not to be delayed, indicating that it is primarily the G2 phase that has been prolonged with this ablation procedure. The stromal thickness was increased from about one half of the normal values immediately after the treatment to above normal values at Day 4, thereafter decreasing to normal values at Day 13. Thus, the regenerative ability of the stroma is more pronounced in rats than in humans, but also in humans regeneration of the stroma can possibly explain the regression of the myopic shift seen some time after excimer laser treatment.

The middle-Norway eye-screening study. III. The prevalence of capsular glaucoma is influenced by blood-group antigens.

The association between blood groups (ABO, Rh, Kell, Duffy) and pseudo-exfoliation syndrome, simple, and capsular glaucoma have been evaluated. The findings were: 1). No statistically significant abnormalities regarding blood group distribution in persons with pseudo-exfoliation syndrome. 2). In contrast to simple glaucoma, capsular glaucoma showed an abnormal distribution in the ABO- and the Kell-system. There was less glaucoma prevalence in the capsular A1-group compared to the O-group (p = 0.013), and less in the K1 negative group compared to the K1 positive one (p = 0.005). This trend was even escalated when combining the two systems: Among the K1 negative persons the glaucoma prevalence was lower in the A1-group compared to the O-group (p = 0.003). In the K1 negative group only 9 of 61 A1-persons developed glaucoma, in contrast to the K1 positive group where 4 of 4 A1-persons had glaucoma. This difference gave p < or = 0.00038, whereas the corresponding difference for the O-groups showed p = 0.65. It is concluded that once a person with blood group A1 has developed pseudo-exfoliation syndrome, the risk that capsular glaucoma will occur is about 7 times higher when that person is K1 positive compared to K1 negative. Perhaps this observation may be used as a prognostic factor for non-glaucomatous PE positive persons.

The frequency distribution of the glaucoma tolerance limit.

The probability of having glaucoma may be expressed by the quotient p = (number of eyes with glaucomatous damage)/(total number of eyes). p has been calculated for different IOP levels, within a total population and also within groups with and without pseudo-exfoliation (PE). The resulting quotients were plotted versus IOP. Random irregularities were reduced by regression analysis, using the equation for the logistic distribution. The resulting sigmoid curves demonstrated that the probability p of having glaucomatous damage at a certain IOP is highest in the PE group. In the total material, the glaucoma probability p was 0.5 at IOP = 27.1 mmHg, and at IOP = 25.3 and 28.0 mmHg in the groups with and without PE, respectively. The frequency distributions of the glaucoma tolerance limit have been computed from the glaucoma probability curves.

Frequency distribution of IOP. Analysis of a material using the gamma distribution.

The results of a population-based (age greater than or equal to 65 years) examination of the frequency distribution of IOP are reported. 3726 eyes in 1887 individuals were included in the examination. By consistent use of conventional, well-defined criteria, glaucoma was diagnosed in 6.4% of the individual eyes. In the total material, the average IOP was 18.0 mmHg. Average IOP was 28.7 mmHg in eyes with glaucomatous damage, vs 17.2 mmHg in the normal eyes. Variance of IOP was much higher in the glaucoma group as compared with the normal group. The IOP frequency distribution curve did not fit with a Gaussian curve; it was asymmetric, skewed to the right. The distribution curve obtained by plotting the recorded frequencies was disturbed by irrelevant irregularities, both random and systematic. The irregularities could be evened out by the application of regression analysis, using the equation for the gamma distribution. The IOP frequency distribution is well represented by a gamma distribution curve. The fit is improved by excluding eyes with extremely high and low IOP.

The probability of having glaucoma at different IOP levels.

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.

Pseudo-exfoliation, IOP and glaucoma.

On the basis of a glaucoma survey in a total population greater than or equal to 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 correspondence 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.

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

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.

The Middle-Norway eye-screening study. I. Epidemiology of the pseudo-exfoliation syndrome.

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.

Outpatient anterior chamber lens implantation.

100 outpatient and 143 inpatient intracapsular cataract extractions with anterior chamber lens implantation were examined 6 months post-operatively. 74 (74%) in the former and 107 (75%) in the latter achieved visual acuity greater than or equal to 0.5. Excluding non-surgical pathology, 93% in the outpatient group and 98% in the inpatient group had a visual acuity greater than or equal to 0.5 (P = 0.12). There were no significant differences in post-operative complications except for the incidence of cystoid macular edema. Six (6%) of the outpatient and 1 (0.7%) of the inpatient procedures had cystoid macular edema that resulted in a visual acuity below 0.5 (P = 0.02).

The penetration of ceftazidime into the inflamed rabbit eye.

Acute endophthalmitis was unilaterally induced in 8 rabbits by intravitreal injection of 5 micrograms Escherichia coli endotoxin. A reproducible increase in aqueous humour polymorphonuclear neutrophils and total protein content was observed after 24 h (mean +/- SD: 2400 +/- 274 X 10(6)/l and 3.7 +/- 0.4 g/l, respectively). In the opposite eye only minor changes occurred, making it suitable as a paired control. The intraocular penetration of ceftazidime was then studied in 30 rabbits after i.v. injection of 50 mg/kg body weight. The mean penetration into aqueous humour of the eyes with and without endophthalmitis was 64 and 10%, respectively. In the vitreous body the corresponding penetration was 5 and 1%. The concentration of ceftazidime achieved in the intraocular structures was sufficient to inhibit the growth of pathogens, i.e. Enterobacteriaceae, commonly responsible for intraocular infections.

The occurrence of simple and capsular glaucoma in Middle-Norway.

The records of all patients with simple and capsular glaucoma who visited our clinic in the period from 1.1.1972 to 31.12.1982, and who were alive at the 31.12.82, have been evaluated. In the population older than 49 years 0.54% had simple and 0.74% had capsular glaucoma, equally distributed on men and women. In average near 60% had capsular glaucoma, with great variation in different municipalities. Highest figures were found in a belt reaching from the coast into the inland. Both simple and capsular glaucoma showed increasing occurrence till 75-80 years, thereafter the curves decline.

The prevalence of pseudoexfoliation in three separate municipalities of Middle-Norway. A preliminary report.

An epidemiological eye study has been performed in three separate municipalities in the county of South-Trøndelag, Norway. The prevalence of pseudoexfoliation syndrome turned out to be 10.2%, 21.0%, and 19.6% in the respective areas, stating beyond doubt that there are considerable geographic variations in the distribution of this syndrome.

Senile cataract and ascorbic acid loading.

Serum, aqueous humour, and lens ascorbic acid levels were determined by high-performance liquid chromatography in cataract-, closed-angle glaucoma-, and aphakic patients. The total number of 108 patients were subdivided into different groups. In several groups the pre-operative serum and aqueous amounts were tested, whereafter patients in some groups were loaded with ascorbic acid orally. Finally, a second test was performed on samples taken during operation. It turned out that the ascorbic acid concentration mechanism in cataractous eyes needed more than 12 h for maximum reaction on the loading stimulus. The slow reaction is surprising compared to other species, and it may reflect an affection of the secretory process itself in this disease.

Ascorbic acid determination in serum and aqueous humour by high-performance liquid chromatography.

High-performance liquid chromatography on a Supelcosil LC-HN2 analytical column in weak anion exchange mode has allowed separation of ascorbic acid, in less than 5 min, from other interfering substances in serum and aqueous humour. UV monitoring at 254 nm enables ascorbic acid to be detected at 20 pmol level. A method for determination of ascorbic acid concentration in serum and aqueous humour is described, and values from 10 cataract patients are reported.

Penetration of ceftazidime into the normal rabbit and human eye.

The penetration of ceftazidime into the aqueous humour and the vitreous body of the rabbit eye, after intravenous (i.v.) bolus or subconjunctival injection, was investigated. A dose of 50 mg/kg body weight was administered. After i.v. administration the mean penetration into the aqueous humour was 13% of the plasma values. After subconjunctival injection into the left eye, mean levels of 14% and 25% of the plasma concentrations were found in the right and left eye, respectively. The concentrations in the vitreous body were in all cases below the ceftazidime detection limit (1 mg/l), i.e. less than 1% of the plasma levels. The mean penetration of ceftazidime into human aqueous humour (measured during cataract extraction) was 19% after 2 g i.v. bolus injection. Ceftazidime levels sufficient to inhibit the growth of most pathogens commonly responsible for intraocular infections, including Pseudomonas spp., were consistently found in the aqueous humour. However, inadequate concentrations were achieved in the vitreous body.

ABO-blood groups and D-antigen in simple and capsular glaucoma.

ABO-blood groups and Rh-factor (D-antigen) were determined in 236 patients with POAG, 104 simple and 132 capsular glaucoma. There was a statistical significant difference in the ABO-distribution between the two glaucoma subgroups, and also between the capsular-group and our control material. The simplex-group did not differ from the control material in this respect. For the Rh-group (D-antigen) no differences were found, neither between the two glaucoma subgroups nor between each of them and a reference material.