Use of collagen shields in cataract surgery

Collagen shield delivery of ofloxacin to the human eye

PURPOSE

To determine the ocular penetration of ofloxacin into the anterior chamber of the human eye when delivered by a presoaked collagen shield.

SETTING

University of Colorado School of Medicine, Denver, Colorado.

METHODS

This prospective randomized clinical study comprised 31 patients having cataract surgery. Patients were divided into 2 groups: the first received 3 preoperative drops of commercially available topical ofloxacin 0.3% given 10 minutes apart; the second had a collagen shield soaked in the same medication applied to the eye before surgery. Aqueous humor was extracted immediately before surgery for analysis.

RESULTS

Mean aqueous concentration was 287 ng/mL +/- 69 (SEM) (range 40 to 1141 ng/mL) in the drops group and 957 +/- 189 ng/mL (range 214 to 2437 ng/mL) in the shield group. The difference was statistically significant (P < .005). The minimum inhibitory concentration (MIC) for selected ocular pathogens is between 500 and 4000 ng/mL.

CONCLUSIONS

A collagen shield presoaked in commercially available topical ofloxacin and applied before surgery appears safe. The MICs for many common ocular pathogens were reached or exceeded. Further study is recommended to determine whether this method of infection prophylaxis is an acceptable substitute for subconjunctival injections of antibiotics.

Converting to topical anesthesia in cataract surgery

PURPOSE

To evaluate the complications and difficulties encountered by surgeons converting from paraocular to topical anesthesia in cataract surgery and to evaluate patient pain and satisfaction with each procedure.

SETTING

Department of Ophthalmology, Helsinki University Central Hospital, Helsinki, Finland.

METHODS

Three hundred eyes of 245 consecutive patients were prospectively assigned by permuted block-restricted randomization to receive topical (bupivacaine 0.75%) (Group 1; n = 136) or paraocular (Group 2; n = 163) anesthesia. The intraoperative conditions were judged by the surgeon. A numerical scale (0 to 10) was used to assess the degree of pain during administration of anesthesia, during surgery, and 1 and 24 hours postoperatively. Outcome measures were the number of complications and adverse events registered perioperatively and 4 months postoperatively as well as Snellen visual acuity and surgically induced astigmatism (SIA) measured 1 week and 4 months after surgery.

RESULTS

The success of posterior chamber intraocular lens (IOL) implantation through a self-sealing clear corneal incision was very high (99.3% and 96.9% in Groups 1 and 2, respectively). One case (0.7%) in the topical group required vitrectomy and implantation of an anterior chamber IOL. Anesthesia-related difficulties were reported in about 40% of patients in Group 1 and 4% in Group 2 (P < .001). Supplemental paraocular anesthesia was required in 4 cases (2.9%) in the topical group. Sedative/analgesic medication given perioperatively was required significantly more often in Group 1 (13.2%) than in Group 2 (2.4%) (P < .01). Significantly more pain during surgery (P < .001) and 1 hour after surgery (P < .001) was reported in the topical group. In Group 1 69.9% and in Group 2 93.3% reported no pain during surgery (P < .001). Chemosis (1.8%), subconjunctival hemorrhage (1.2%), and periorbital hematoma (1.2%) were seen only in the paraocular group. Perioperatively, no severe complications occurred in Group 1 and the number of adverse events was less than in Group 2. Postoperatively, 2 cases of endophthalmitis developed in the topical group and none in the paraocular group. There was no between-group difference in outcome measures; a visual acuity of 20/40 or better was found in 87.8% of eyes in Group 1 and 84.9% in Group 2 4 months postoperatively, and the percentages of eyes with SIAs within 1.0 diopter of preoperative values were similar (78.6% and 73.3%, respectively). Patient preference for topical anesthesia appeared to be higher than for paraocular anesthesia.

CONCLUSION

Paraocular anesthesia gave better analgesia than topical, but topical anesthesia provided acceptable analgesia during surgery and showed that intraocular procedures can be performed without akinesia. The surgeon converting to topical anesthesia may expect slight difficulty in 40% of cases and more severe difficulty in 7%. Surgically related complications were similar with both methods.

Outcomes of small incision cataract surgery

PURPOSE

To compare cataract surgery outcome measures 4 months postoperatively and determine their association with changes in the eye's functional state.

SETTING

Department of Ophthalmology, Helsinki University Central Hospital, Finland.

METHODS

This longitudinal study comprised 219 consecutive patients having first-eye or second-eye cataract surgery by one surgeon. In most patients, the technique consisted of small-incision cataract surgery with in-the-bag intraocular lens implantation. Patients were interviewed and clinical data obtained preoperatively and 4 months postoperatively. Adverse events occurring within 24 hours and 4 months postoperatively were compared with changes in global measures of vision. Surgical success in terms of surgically induced astigmatism (SIA) was measured at 4 months using vector analysis of the changes in astigmatism and defining the extent to which the surgical goal was achieved. The association between the surgical astigmatism goals and global measures of vision was analyzed.

RESULTS

The percentage of patients showing improvement 4 months after first-eye cataract surgery varied by outcome measure: Snellen visual acuity (95.0%), VF-14 score (89.4%), satisfaction with vision (80.1%), self-reported trouble with vision (75.8%), and cataract symptoms (75.1%). Changes in Snellen acuity after second-eye cataract surgery were similar but VF-14 changes were significantly less than after first-eye surgery. Changes in global measures of vision were also better after first-eye surgery. The correlation between the change in VF-14 score and global measures of vision was stronger than between the change in Snellen acuity and the same general outcome measures. A good correlation was also seen between the changes in VF-14 scores and cataract symptoms. Mean SIA in all eyes was 0.2 diopter (D) +/- 0.7 (SD); 91.2% were within +/- 1.0 D of preoperative values. Failure to achieve surgical astigmatism goals was not associated with patients in whom global measures of vision did not improve, nor was there a correlation between adverse events occurring within 24 hours or 4 months postoperatively and global measures of vision. The only association was between ocular comorbidity or potential risk factors of phacoemulsification and adverse events seen within 24 hours and at 4 months.

CONCLUSION

Estimates of the proportion of patients benefiting from cataract surgery varied with the outcome measure used to determine benefit. The change in the VF-14 score was a better measure than Snellen acuity of the benefit of cataract surgery.

Compatibility of corticosteroids and antibiotics in combination

PURPOSE

To study the compatibility of combinations of antibiotics and steroids commonly used in anterior segment surgery.

SETTING

Research Laboratory, Helsinki University, Finland.

METHODS

Aggregate production in vitro and in vivo was studied for three injectable antibiotics (cefotaxime sodium, tobramycin sulfate, and gentamicin) and four corticosteroids (triamcinolone acetonide, methylprednisolone sodium succinate, methylprednisolone acetate, and dexamethasone sodium phosphate) using conventional and dark-field microscopy. Aggregate formation on collagen shields and subconjunctival aggregate formation of tobramycin sulfate in combination with methylprednisolone acetate or dexamethasone sodium phosphate was also studied.

RESULTS

Dexamethasone sodium phosphate (4 mg/mL) did not form aggregates with any of the three antibiotics tested. Cefotaxime sodium did not cause aggregates when 24 mg/mL of dexamethasone sodium phosphate was used both in vitro and in vivo or in association with collagen shields.

CONCLUSIONS

To avoid undesired side effects, such as epithelial sloughing and corneal edema after collagen shield application, antibiotics and steroids must be carefully selected.

Prevention of high risk corneal graft rejection using cyclosporine A (CsA) incorporated into a collagen matrix

The aim of this work was to compare the efficacy of cyclosporine (CsA) collagen shields and fragments in suppressing experimental allograft rejection in an animal model for high risk keratoplasty. Altogether 23 experimental animals were treated either with plain collagen shields, oral cyclosporine, collagen CsA shields, or with CsA collagen fragments after corneal transplantation (PKP) in previously vascularized corneas. The study medications were started immediately following PKP. For these animals slit lamp examinations were performed twice a week for the duration of the experiment and the signs of corneal rejection were observed. The animals were followed until an irreversible rejection or until the end of the experiment (14-149 days). The inflammation of the graft was also evaluated histologically when animals were sacrificed. The grafts treated with plain collagen shields all were rejected within 36 days, and the mean graft survival time for these corneas was 25 days. Five transplants that were treated with oral CsA had better survival, and two of five grafts stayed clear until postoperative day 119, when the treatment was stopped. The best graft survival was seen in grafts treated with CsA collagen fragments and all these stayed clear up to 77 days postoperatively. The treatment of the grafts with CsA collagen shields was almost as effective as with CsA fragments, and first signs of rejection appeared as late as nine weeks postoperatively in two of seven grafts. The other of these rejected corneas were later treated with CsA collagen fragments and showed a dramatic improvement in transparency of the cornea and disappearance of inflammation of the graft. The discontinuation of study medication caused an irreversible rejection to appear in a previously clear graft that had been treated successfully with any study medication. We conclude that topical CsA in shields or in fragments will provide a significant advance over systemic CsA alone, and that CsA fragments appear to be as effective as shields in preventing corneal allograft rejection.

Effect of collagen cross-linking in collagen corneal shields on ocular drug delivery

It is well known that some ocular diseases can be treated more effectively with a collagen shield containing drug. The influence of collagen cross-linking on drug delivery is not known. We determined if collagen cross-linking affects ofloxacin bioavailability at three different collagen shield dissolution times. In this study, the collagen shields were not impregnated in drug but an eye drop was simply instilled after application of collagen shield. A non-cross-linked collagen shield, with a dissolution time of 12 h, disappeared more rapidly from the rabbits' eyes due to proteolysis after application in vivo. On the other hand, the cross-linked collagen shields, with dissolution times of 24 and 72 h, served as an ofloxacin depot and enhanced topical ofloxacin penetration into the cornea and the aqueous humor. As the dissolution times for the cross-linked collagen shield are longer than those of the non-cross-linked type, they serve as drug reservoirs. Therefore, cross-linked collagen shields might be useful ocular drug delivery devices because they can allow drug concentrations to achieve higher levels in the cornea and aqueous humor.