Complement activation in the aqueous humor of pseudophakic bullous keratopathy patients

BACKGROUND/AIMS

According to some studies, inflammation is a potential etiological factor in pseudophakic bullous keratopathy (PBK). Our aim was to obtain information on the activation of the complement system in the aqueous humor in this disorder.

METHODS

Aqueous humor samples were collected during keratoplasty of 12 PBK patients, as well as during phacoemulsification surgery of 18 control patients. The concentrations of the protein-protein complexes generated during complement activation (C1rC1sC1inh and C3bBbP) through the classical and alternative pathways, respectively, as well as of the C3 cleavage product C3a, were measured with ELISA methods. The correlation among the complement factors and between the duration of the edema, the stage of the disease, and the level of the complement activation products was examined.

RESULTS

The concentration of C1rC1sC1inh, C3bBbP complex and C3a was significantly higher in the PBK group (p < 0.001) compared to the control group. In PBK patients, a correlation was found between the levels of the C1rC1sC1inh complex and C3a only.

CONCLUSION

Our new findings indicate that in PBK the complement system is activated - via the classical pathway - in the aqueous humor. The activated complement may play a role in increased endothelial cell loss.

Both freshly prepared and frozen-stored amniotic membrane cells express the complement inhibitor CD59

Amniotic membrane proved to be very effective tool in the treatment of a number of ocular surface diseases. The amniotic membrane, however, has to be stored before its transplantation onto the ocular surface followed by mandatory serologic control in order to exclude the transmission of certain viruses. Therefore it is most important to study if cryopreservation of the membrane affects cell surface expression of the molecules. We measured cell surface expression of CD59, a membrane-bound complement inhibitor on the cells of freshly prepared and cryopreserved amniotic membrane. Cells of amniotic membrane were separated mechanically. Epithelial and mesenchymal cells were identified by the intracellular expression of nanog and the cell surface ICAM1 positivity, respectively. Multicolor flow cytometric immunophenotyping was used for determination of the CD59 expression. CellQuest-Pro software program (Becton Dickinson) was used both for measurements and analysis. CD59-positive cells could be detected in all investigated samples and in all investigated cell types, although the expression level of CD59 differed. CD59 was expressed both on freshly prepared and frozen-stored samples. Higher level of CD59 was detected on ICAM1+ mesenchymal cells than on nanog+ epithelial cells. Our findings indicate that amniotic membranes maintain their complement inhibiting capacity after cryopreservation.

Changes in tear protein pattern after photorefractive keratectomy

PURPOSE

Changes in tear protein composition of patients who underwent photorefractive keratectomy (PRK) were analyzed.

METHODS

Tear samples were obtained from 23 eyes of 23 patients immediately before PRK and on the fourth postoperative day with glass capillaries. Tear proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Digital image analysis and evaluation of the densitometric data of the electrophoretic separations were done with BioDoc-Analyze.

RESULTS

Analysis of discriminance found a significant difference in the protein patterns (p < 0.001). This type of analysis of the electrophoretic densitographs uses all peak information simultaneously. A significant decrease (p < 0.005) in three of the main protein peaks--lactoferrin, immunoglobulin A heavy chain, and lysozyme--was also found after PRK.

CONCLUSIONS

Excimer laser ablation of the cornea has an acute effect on lacrimal gland protein secretion. Changes in tear composition may lead to feelings of dryness and to a decrease in tear film stability postoperatively.

C1r-C1s-C1inhibitor (C1rs-C1inh) complex measurements in tears of patients before and after penetrating keratoplasty

PURPOSE

The aim of this pilot study was to determine the presence of complement activation products in tears from pre- and postkeratoplasty eyes and the fellow eyes in order to investigate the activation of the classical and alternative pathways of the complement system in the early postkeratoplasty period.

METHODS

Tear samples from both eyes of 19 prekeratoplasty patients were tested. From 10 patients, samples were taken before operation, one week and 3 weeks after penetrating keratoplasty. Only baseline and 1 weak samples, and baseline and 3 week samples were available from 5 and 2 patients, respectively, while only baseline tear samples were collected from 2 patients. Tear concentration of two complement activation products, C1rs-C1inh and C3bBbP were determined by enzyme-linked immunosorbent assay.

RESULTS

There was no difference (p = 0.339) between baseline samples of the eyes waiting for operation (0.93 +/- 0.51 AU/ml, mean +/- SEM) and the fellow eyes (0.33 +/- 0.33 AU/ml) in respect of mean C1rs-C1inh complex concentration. The one-week samples of the operated eyes revealed significantly (p = 0.006) elevated levels of C1rs-C1inh complexes (18.8. +/- 6.37 AU/ml), compared to their baseline samples (1.18 +/- 0.64 AU/ml), whereas the one-week values of the fellow eyes did not differ from the baseline values. Compared to the increased one-week values, the three-week values decreased to the baseline values in the operated eyes. C3bBbP could be detected in 3/68 tear samples.

CONCLUSIONS

In our study we demonstrated the increased concentration of C1rs-C1inh complex in several tear samples taken early after human penetrating keratoplasty. These findings provide direct evidence that the classical pathway of complement may be activated in the early postoperative period after penetrating keratoplasty.

Photorefractive Keratectomy for Hyperopia in 800 Eyes With the Meditec MEL 60 Laser

PURPOSE

To evaluate the refractive results of 800 hyperopic eyes undergoing PRK treatment.

METHODS

Eight hundred hyperopic eyes were treated with PRK. An Aesculap-Meditec MEL 60 scanning ArF excimer laser used. Treatment Group 1 consisted of eyes with a preoperative refractive error of +3.50 D or less (n = 482) and Group 2, of +3.75 D or more (n = 318).

RESULTS

Preoperatively, Group 1 required an average correction of +2.88+/-1.34 D and Group 2 required +5.64+/-2.96 D. One year after PRK, average residual correction was +1.26+/-1.24 D in Group 1, and in Group 2, +2.46+/-1.84 D. In Group 1, uncorrected visual acuity (UCVA) was 20/40 or better in 88.4% (426/482); 20/20 or better in 75.7% (365); 2.1% (10/482) of eyes lost 2 lines, 2.1% (10/482) gained 2 lines; 3.1% (15/482) gained 2 or more lines of BSCVA; 74.4% (359/482) of eyes were within +/-0.50 D of target correction and 84.8% (408/482) were within +/-1.00 D. In Group 2, 47.5% (151/318) had UCVA of 20/40 or better; 34.2% (109/318) saw 20/20 or better uncorrected; 19.1% (61/318) lost 2 lines; 11.6% (37/318) lost 3 lines; none of the eyes gained 2 or more lines of BSCVA; 22.3% (71/318) were within +/-0.50 D and 46.8% (149/318) were within +/-1.00 D of target correction. Refractive stability was achieved after 6 months; a slight regression after 6 months was still observed. In Group 1, 10.5% (42/482) and in Group 2, 21.6% (69/318) complained of problems with daytime vision (glare and ghost image); during night-driving in Group 1, 17.6% (85/482) and in Group 2, 40.5% (129/318) had problems.

CONCLUSION

PRK with the Aesculap-Meditec MEL 60 scanning ArF excimer laser offered the best long-term results with +3.50 D or less preoperative refractive error. With higher corrections, regression, decrease in BSCVA, and daytime visual problems were encountered.

[Results of photorefractive keratectomy after treatment of 2053 eyes]

To evaluate the 12 months refractive results of photorefractive excimer keratectomy (PRK) in high number of eyes with different type of refractive error. Between October 1992 and December 1996. 2053 eyes of 1098 patients were treated with the Aesculap Meditec MEL 60 argon-fluoride excimer laser. Refractive results were concluded at the 12th post-PRK month. The following patient groups were used during the study: Group 1.: Eyes between -1.0 D and -6.0 D (n = 651); Group 2.: -6.0 és -9.0 D (n = 216); Group 3.: Eyes with refractive error above -9.0 D (n = 163); Group 4.: Hypermetrop eyes (n = 160); Group 5.: Eyes with myopic astigmatism (n = 746); Group 6.: Eyes with hypermetropic astigmatism; Group 7.: Pure astigmatism (n = 13). In Group 1. The preoperative average -3.94 +/- 1.3 D refractive error decreased during the 1-year follow-up period to -0.47 +/- 0.54 Dpt; in Group 2. The preoperative -7.65 +/- 1.07 D to -1.16 +/- 1.86 D; in Group 3. The preoperative average -13.58 +/- 3.51 D to -3.11 +/- 2.75 D; in Group 4. The preoperative +4.04 +/- 1.77 D to +1.02 +/- 1.16 D in Group 5. The preoperative -6.06 +/- 2.78 D spherical component decreased to -0.95 +/- 1.33 D-ra, whereas the preoperative cylindrical component from -1.5 +/- 1.08 D to -0.13 +/- 0.58 D; in Group 5. The preoperative +4.57 +/- 1.78 spherical component to +1.13 +/- 1.38 D; whereas the preoperative cylindrical component from +1.57 +/- 0.96 D to +0.38 +/- 0.77 D; in Group 7. The preoperative a -3.98 +/- 1.2 D cylinder decreased to -0.62 +/- 0.75 D cylinder. PRK decreased effectively the preoperative correction need in every treatment group. The results are the better, the smaller the preoperative correction need is.

Excimer laser treatment of hyperopia

PURPOSE

The aim of this study was to analyse the clinical results of hyperopic photorefractive keratectomy treatments and to compare the results achieved with the usage of different masks.

METHOD

20 eyes of 16 hyperopic patients were treated, using the Aesculap-Meditec MEL60 193nm ArF excimer laser. The mean duration of follow-up was 9.9+/-3.4 months. Statistical comparison of the results with the two masks was made using the unpaired Student t-test.

RESULTS

Preoperative mean spherical equivalent was +4.23+/-1.18D, which changed to +0.20+/-0.78D at one month and regressed to +1.23+/-1.27D at the last control examination. After 6 months 60% (12 eyes) had spherical equivalent within +/-1.0D of the attempted correction. The statistical analysis showed no significant difference between the results with the two masks.

CONCLUSION

Good preparation for the treatment is of equal importance for the results of the photorefractive keratectomy as compared to the technical circumstances.

[Phototherapeutic use of excimer laser]

The photorefractive excimer laser is not only able to alter the refractive power of the corneas but also suitable to treat superficial corneal pathologies. Authors performed phototherapeutic keratectomies (PTK) in 80 eyes of 77 patients. The age was on average (+/- S.D.) 49.4 +/- 22.03 years. The follow-up time varied between 3-24 months. All treatments were performed with the Aesculap Meditec MEL 60 ArF excimer laser, working in the 193 nm extreme ultraviolet-C range. Authors conclude that the best postoperative results can be achieved with PTK in cases of recurrent corneal erosions and superficial corneal opacities. Favourable outcome could be expected in treatment of infectious corneal ulcers. In cases of bullous keratopathy the subjective complaints decreased and it was successful to postpone the time of perforating keratoplasty. The PTK is not recommended in case of corneal Bowen disease and recurrent pterygia. A hyperopic shifts was observed in 2 eyes. Besides, the traditional surgical methods the phototherapeutic keratectomy is an important progress in treatment of superficial corneal pathologies. Applying the method, the recurrent erosions healed quicker, in most of the cases the transparency of the cornea could be reestablished in the pupillary area and the need for perforating keratoplasty could be postponed or avoided.

[Experience with excimer laser photorefractive keratectomy]

The correction of refractive errors based on superficial ablation of the cornea has a couple of years long history. Authors performed photorefractive laser surgery with the Aesculap Meditec MEL 60 ArF excimer laser in 221 eyes of 147 patients. The follow-up time varied between 2-24 months, average 8 months. They have treated the following groups: 1. group: 0-6.0 D; 2. group: -6.5-9.0 D; 3. group: eyes with refractive error above -9.5 D; 4. group: hypermetropic eyes; 5. group: eyes with astigmatism.

RESULTS

In the 1. group the average -4.58 +/- 1.25 D refractive error decreased to -0.19 +/- 0.53 D in the follow-up time; 2. group: from -7.46 +/- 1.22 D to -0.45 +/- 0.83 D; 3. group: -13.76 +/- 5.46 D to -1.52 +/- 1.74; 4. group: +428 +/- 1.6 D to +0.91 +/- 2.41 D; 5. group; from -6.74 +/- 2.81 D sph -2.3 +/- 1.54 cyl to -0.51 +/- 1.3 D sph -0.54 +/- 1.06 D cyl. According to their experiences they conclude: the best results have been achieved in the first two groups and in eyes with astigmatism (1., 2., 5. groups). In severe myopia cases postoperative correction is usually needed, which is significantly smaller than the preoperative spherical correction. The method is able to change the refractive power of the cornea and provides an efficient alternative to the spectacles and contact lenses.

Experiences with photorefractive excimer laser treatment in compound myopic astigmatism

The invention of excimer lasers and different masks in order to treat refractive failures has opened a new era in refractive surgery. The refractive grading, the ablation effect, which can be controlled within one micrometer, and the design of a special mask made possible so-called "corneal sculpting" in compound astigmatism. The authors evaluated their experiences on 27 myopic compound astigmatic eyes. The average age of the patients was 28.67 +/- 9.78 years and the average preoperative uncorrected visual acuity was 0.06 +/- 0.04. The spherical component averaged -6.74 +/- 2.81 D and the cylindrical component averaged -2.3 +/- 1.54 D (the preoperative correction needed to obtain the best corrected visual acuity). Postoperatively, the uncorrected visual acuity improved to 0.65 +/- 0.26. To obtain the best corrected postoperative visual acuity an average -0.51 +/- 1.06 D sph and an average -0.54 +/- 1.06 D cyl component was needed. The authors conclude that ArF excimer laser treatment is able to alter both of the spherical and cylindrical components of the eye toward emmetropia. The lower the degree of preoperative compound myopic astigmatism, the better are the chances of postoperative emmetropia. No serious complications were met during the follow-up period.

Refractive results after photorefractive excimer laser treatment in mild myopic and in mild hyperopic eyes

Evaluation of 12-month results of photorefractive keratectomies (PRK) performed in low myopic (0 to -6.0 D) and low hyperopic (0 to +6.0 D) eyes. Myopic and hyperopic PRK treatments with the Aesculap Meditec MEL 60 ArF excimer laser. Prospective study, 30 eyes per group. The change in best corrected visual acuity (VA), refraction required, uncorrected VA and the postoperative haze were compared at the 12th postoperative month. The average preoperative correction in the low myopic eyes (Group I) was -4.65 +/- 1.24 D, which decreased to -0.17 +/- 0.56 D during the follow-up. In mild hyperopic eyes (Group II) the preoperative refraction was +3.9 +/- 0.93 D and decreased to +1.23 +/- 1.59 D post-PRK. Comparing the pre- and postoperative average best corrected VA values, there was no statistical change in either group. In the low myopic group all eyes had a 20/40 or better uncorrected VA, in hyperopic eyes 11 had a VA of 20/40 or better, four had a worse uncorrected VA. In Group I, 86.6% of the eyes were within +/-1.0 D of the intended refraction at 12 months postoperatively. In Group II, 46.7% of the eyes were within +/-1.0 D of final refraction. There were no intergroup differences in subjective complaints, reepithelization and average postoperative haze. Both methods are able to alter the refractive power of the cornea toward emmetropia. The predictability of the method was to be found higher in cases of mild myopia than in mild hyperopia. The upper limit of myopia is above -6.0 D, but in hyperopia, with the present technical facilities, good postoperative results can be obtained only as far as +4.25 D of preoperative refractive error.

Retinoscopy after excimer laser photorefractive treatments

Photorefractive keratectomy (PRK) is capable of changing the refractive power of the human cornea. Retinoscopy is an objective method of measuring the refractive power of the eye. The authors performed PRK in 28 myopic eyes with the Aesculap Meditec MEL 60 ArF excimer laser. During a prospective study, the subjective and objective refractive power of the eyes were assessed and compared 6 months after PRK. The average preoperative refractive error was: -5.11 +/- 2.51 D and -5.08 +/- 2.20 D on the right side (n = 16) and on the left side (n = 12), respectively. In order to obtain the best corrected visual acuity 6 months after PRK, the right and left eyes needed an average of -0.09 +/- 0.26 D and -0.33 +/- 0.64 D postoperative correction, respectively. The postoperative refractive change could be verified with the retinoscopy at +/-0.5 D accuracy. The authors describe a double refractive corneal ring after PRK, which may disturb retinoscopy. The post-PRK refractive change can be verified by retinoscopy. Postoperative funduscopy, fundus photography and possible future retinal procedures were not disturbed by the double corneal refractive rings in myopic eyes.

Plume emission, shock wave and surface wave formation during excimer laser ablation of the cornea

Excimer lasers are now used for corneal surgery; however, the physical processes occurring during photoablation of the cornea are incompletely understood. High speed laser-based photographic arrangement was constructed. The temporal resolution was better than 1 ns. The setup could work as a Schlieren arrangement, which is sensitive to the refractive index change caused by the shock wave propagating in the air above the eye. With minor changes the setup was converted into a shadowgraph, which could detect the ablation plume and the waves propagating on the surface of the eye. Due to the impact of the excimer laser pulse onto the surface of the cornea, a shock wave was generated in the air. The shadowgraph clearly showed the ejection of the ablated cornea. The ejection velocity of the plume was found to be over 600 m/s. It was shown for the first time that the recoil forces of the plume are generating a wave on the surface of the eye. The laser-based high speed photographic arrangement is a powerful arrangement in the study of physical effects occurring during photoablation of the cornea.