Patients who attended our clinic had undergone cataract surgery at least 1 year before Nd:YAG laser treatment. Photographs from 85 pseudophakic eyes with pronounced regeneratory PCO (pearl type) of 77 patients from three continuous studies were included for this study. Mean age of the patients was 72 years (range, 28–93 years). In all (85) cases, retroillumination images were taken on day 0, in 65 cases on day 2, in 59 cases on day 7, and in 77 cases on day 14.
Altogether, 6309 pearls were marked, ranging from 21 to 151 pearls per eye. An example is shown in
Figure 2. On average four pearls were found per square millimeter (range, 0.2–9.7/mm
2; coefficient of variation [CV], 49.5%). The 25% of eyes (lower quartile) with the lowest pearl density showed a higher number of appearing pearls (12 appearing pearls per eye [range, 0–29 pearls]) and a lower number of disappearing pearls (9 disappearing pearls per eye [range, 2–16 pearls]) during 2 weeks compared with eyes with a high pearl density (4 appearing pearls per eye [range, 0–12 pearls] and 13 disappearing pearls per eye [range, 2–40 pearls];
P = 0.0001).
The mean cumulative area of all marked pearls per eye and follow-up was 0.66 mm
2 (range, 0.03–2.18 mm
2; CV, 66.7%). Over the follow-up period, the mean cumulative area of all marked pearls changed from 0.66 mm
2 at day 0 (range, 0.03–2.20 mm
2; CV, 66.7%) to 0.60 mm
2 (range, 0.03–1.88 mm
2; CV, 073.3%), 0.68 mm
2 (range, 0.06–1.95 mm
2; CV, 100%), and 0.62 mm
2 (range, 0.09–1.82 mm
2; CV, 66.1%) at days 2, 7, and 14, respectively (
Fig. 3, top).
Concerning pearl size change within 1 week, 36.3% (CV, 5.5%) of all pearls increased in size, 7.0% (CV, 8.6%) did not change in size, and 34.9% (CV, 6.7%) decreased in size. Furthermore, 10.5% (CV, 6.3%) of all pearls had newly appeared, and 11.3% (CV, 5.7%) of all pearls had disappeared during 1 week (
Fig. 4). On average, 27 pearls per eye (range, 0–76 pearls; CV, 8.9%) decreased, 6 pearls (range, 0–24 pearls, CV, 10.0%) did not change in size, and 29 pearls per eye (range, 0–68 pearls, CV, 6.9%) increased in size during 1 week. Furthermore, 7 pearls (range, 1–23 pearls, CV, 10.0%) per eye appeared, and 7 pearls (range, 0–20 pearls, CV, 8.6%) per eye disappeared during 1 week.
Table 1 summarizes the changes in all pearls and the dependence on pearl size during 1 week.
Mean pearl size changed from 9630 μm
2 at day 0 (range, 2390–33745 μm
2; CV, 61.0%) to 10306 μm
2 (range, 2223–32568 μm
2; CV, 61.3%), 10972 μm
2 (range, 1332–30717 μm
2; CV, 59.3%), and 10069 μm
2 (range, 2871–33466 μm
2; CV, 63.4%) on days 2, 7, and 14, respectively (
Fig. 3, bottom).
The solidity of pearls decreased slightly from 0.85 (0.40–0.98; CV, 11.8%) at baseline to 0.83 (0.41–0.98; CV, 13.3%) at the 1 week follow-up (
Fig. 5). The roundness decrease was constant, with 0.06 (0.03–0.07; CV, 0.17%) at baseline and at the 1 week follow-up. The upper quartile of all eyes with the highest pearl density showed a higher solidity (mean, 0.8; range, 0.7–0.9) and a higher roundness (mean, 0.07; range, 0.06–0.07) than the eyes in the lower pearl density quartile (mean, 0.7; range, 0.5–0.8; mean, 0.06; range, 0.03–0.07, respectively).
At baseline and on days 3 and 7, mean pearl sizes of 2720 μm2, 5300 μm2, and 6150 μm2, respectively, were found for newly appearing pearls. The solidity of 0.977, 0.980, and 0.976 and the roundness of 0.0727, 0.0733, and 0.0721 were higher than those of pearls that showed no or little change. At baseline and on days 3 and 7, mean pearl sizes of 8100 μm2, 8500 μm2, and 7400 μm2, respectively, were found for disappearing pearls. The solidity of 0.974, 0.974, and 0.972 and the roundness of 0.0726, 0.0726, and 0.0719 were also higher than those of pearls that showed no or little change.
Mean change in the size of a pearl per day was 583 μm
2 (175–1631μm
2; CV, 55.4%). There was no correlation between the pearl density and the daily change in pearl size (
r = 0.10;
P = 0.00). However, daily change in pearl size correlated with solidity (
r = 0.52;
P = 0.00) and roundness (
r = 0.49;
P = 0.00;
Fig. 6).
Both the appearance and the disappearance of pearls during the period of follow-up occurred in a linear fashion (
Fig. 7). The probability that a pearl disappeared during a time period of 1 week was 11.3% (CV, 5.3%) and that a new pearl appeared was 10.5% (CV, 6.7%). Extrapolating from this linear relationship, all pearls that were present at baseline would have disappeared after 8.9 weeks, and it would have taken 9.5 weeks for a completely new set of pearls to be formed. The calculated mean lifespan of a pearl would be on the order of 19 weeks. Pearls with a lifespan of less than 2 weeks were observed in only 1% of all pearls. The largest size these short-lived pearls attained was 9255 μm
2 on average. All other observed pearls existed longer than 2 weeks. Taking into account the rapid morphologic changes found, we decided to focus on the size and shape changes of Elschnig pearls during the shorter time range of 1 week instead of 2 weeks.
To create a representative simulation of the size and shape characteristics of a pearl during its lifetime, mean values for size and shape were calculated, and representative pearls from the dataset were selected for illustration (
Fig. 8). On the first day the pearl's appearance is small, solid, and round. During the next days the pearl increases in size but stays round and solid. Then the pearl's solidity and roundness decrease, and several morphologic changes are possible. In the schematic illustration (
Fig. 8), a questionable separating, or dividing, pearl is shown that was thought to be seen in several instances in the dataset. In the weeks and days before disappearing, the pearl can undergo two different morphologic changes. Some pearls increase in size within this time period before disappearing, whereas other pearls decrease in their last days before they disappear. Whether they increase or decrease in size, usually their solidity and roundness increase again before they disappear.
Neither IOL material nor age or sex (r 2 < 0.4 in all cases) had any significant influence on the behavior of pearls, whether concerning change in size or morphology.