Is 2% hydroxypropylmethylcellulose a safe solution for intraoperative clinical applications?

Comparison of the effect of Healon, Healon GV, Healon 5, Viscoat, and Ocucoat on platelet aggregation under in vitro conditions

PURPOSE

To study the effect of Healon, Healon GV, Healon 5, Viscoat, and OcuCoat on platelet aggregation under in vitro conditions.

METHODS

Ocular viscoelastic devices including Healon, Healon GV, Healon 5, Viscoat, and OcuCoat were studied to investigate the effect of these agents on platelet aggregation under in vitro conditions. The experiments were performed by using platelet-rich plasma with an aggregometer. Aggregation was induced with three different agonists including 5''-adeno-sinediphosphate (ADP), epinephrine (EPI), and collagen (Col ). The results were obtained as a percentage of maximal aggregation and compared with controls using one-way analysis of variance (ANOVA) test.

RESULTS

The tests with ADP as aggregating agent revealed that the percentages of maximal aggregation were a mean of 75 +/- 4.35% for ADP only, 67 +/- 4.35% for Healon, 59.33 +/- 3.51% for Healon GV, 70 +/- 3% for Healon 5, 58 +/- 3.46% for Viscoat, and 64 +/- 2% for OcuCoat. Kruskal-Wallis one-way ANOVA test revealed no significant decrease in the percentage of maximal aggregation for all tested substances. With EPI, aggregation was induced in all control samples with a mean of 80.66 +/- 2.08%. The mean percentage of maximal aggregation was 67 +/- 3% for Healon, 77.66 +/- 4.04% for Healon GV, 77 +/- 4% for Healon 5, 80.6 +/- 4.04% for Viscoat, and 65 +/- 5% for OcuCoat. Statistical analysis showed no significant difference. With collagen, maximum aggregation was 74 +/- 5.29% for controls, 65 +/- 4.35% for Healon, 54 +/- 2% for Healon GV, 51 +/- 2.64% for Healon 5, 59 +/- 2% for Viscoat, and 72.66 +/- 1.52% for OcuCoat. Kruskal -Wallis one-way ANOVA test revealed no significant change in the percentage of maximal aggregation for all tested substances in the experiments.

CONCLUSIONS

Ophthalmic viscosurgical devices like Healon, Healon GV, Healon 5, and Viscoat that contain glycosaminoglycans and OcuCoat that contains hydroxypropyl methylcellulose have inhibitory effects on platelet aggregation but the effect is not statistically significant and there is no difference among the ocular viscoelastic devices in regard to inhibitory effect on platelet aggregation.

New generation hydroxypropyl methylcellulose (HPMC-Ophtal H) for intraocular surgery: a confocal laser scanning microscopy study

PURPOSE

To determine the abundance and variety of particulate debris in new generation hydroxypropyl methylcellulose (HPMC) samples.

METHOD

Three samples of sterile HPMC-Ophtal H were examined using a confocal laser scanning microscope, scanning electron microscope and mass spectrometry.

RESULTS

Confocal laser scanning microscopy of the samples showed that particulate matter in HPMC was less than 30 microns in size and at a density of less than 1000 particles per millilitre. No discernible details were seen by the scanning electron microscope, and mass spectrometry did not identify and bands.

CONCLUSION

Improved methods of preparation including filtration may be responsible for decreased particulate debris in new generation HPMC.

Corneal endothelial protection by different viscoelastics during phacoemulsification

PURPOSE

To evaluate corneal endothelium morphology and function after phacoemulsification using different viscoelastics.

SETTING

Eye Clinic, University of Trieste, Italy.

METHODS

This prospective, randomized study included results of preoperative and postoperative (7, 30, and 90 days) examinations of 66 patients scheduled for phacoemulsification without ocular pathology; 8 patients were excluded. Patients were randomly assigned to one of four groups based on type of viscoelastic used: 1% sodium hyaluronate (Healon); 1.4% sodium hyaluronate (Healon GV); 4% sodium chondroitin sulfate-3% sodium hyaluronate (Viscoat); 2% hydroxypropyl methylcellulose (Hymecel). Mean cell density and cell size variation coefficient were determined by specular microscopy; central corneal thickness, by ultrasonic pachymetry; and endothelial permeability coefficient and active pump function, by anterior segment fluorophotometry.

RESULTS

There were no significant differences in postoperative mean cell loss among the groups. The cell size variation coefficient was altered in all groups 7 days after surgery and was still impaired at 30 days in the Hymecel group. A significant increase in mean corneal thickness, endothelial permeability, and active pump function occurred in the Healon and Hymecel groups 7 days after surgery. These parameters were still altered 30 days after surgery in the Hymecel group. Endothelial functional alterations did not occur in the Healon GV or Viscoat group.

CONCLUSION

Viscoat and Healon GV are effective in minimizing functional damage of endothelial structure in the early medium-term postoperative period.

Pupil size and reactivity following hydroxypropyl methylcellulose and sodium hyaluronate

AIMS

A prospective randomised clinical trial was set up to compare the effect of hydroxypropyl methylcellulose (Ocucoat) and sodium hyaluronate (Healonid) on pupil size and reactivity following their use in cataract surgery.

METHODS

Pupil measurements were recorded before and 6 weeks after surgery.

RESULTS

There was no significant difference between the two groups with respect to pupil size (p = 0.69, Mann-Whitney U test) nor with respect to reactivity (p = 0.99, Fischer's exact test). Ninety six per cent of the surgery was performed using phacoemulsification.

CONCLUSION

This trial suggests that both viscoelastic materials have similar effects on the pupil after their use in cataract surgery.

The fixed dilated pupil after cataract surgery--is it related to intraocular use of hypromellose?

Hypromellose can be used as a viscoelastic substance during cataract surgery. Two groups of patients, one group operated on using hypromellose, the other using sodium hyaluronate as a viscoelastic substance were followed up 2-6 months postoperatively. A total of 16.7% of the eyes operated on using hypromellose developed a non-reactive semidilated pupil whereas none of the eyes from the control group developed this phenomenon. It was concluded that there is a probable link between the intraocular use of hypromellose and abnormal pupils after cataract surgery.

Long-term results of extracapsular cataract extraction with posterior chamber lens implantation: sodium hyaluronate 1% vs hydroxypropyl methylcellulose 2%

We investigated the frequency of surgical complications and the long-term outcome in terms of visual acuity, intraocular pressure and post-operative complications in 206 extracapsular cataract extraction procedures with posterior chamber lens implantation using either sodium hyaluronate 1% (Healon) or hydroxypropyl-methylcellulose 2% over a follow-up period of 12 months. We found no significant difference in the results of using either of the two viscoelastic agents.

Light and electron microscopic analysis of intraocular 2% hydroxypropylmethylcellulose

Twenty samples of 2% hydroxypropylmethylcellulose for intraocular surgery, obtained from two Brazilian laboratories, were studied to determine the presence and type of impurities in the solutions. These were compared with ten samples of balanced salt solution (control group). Using light and scanning electron microscopy, five types of particles were identified: cellulose fibers, vegetable flakes, crystals, glass fragments, and other impurities. At least one of these contaminants was present in each sample of 2% hydroxypropylmethylcellulose. The vegetable matter was also seen in a sample of the raw material from which the clinical material had been prepared. Control solutions (i.e., balanced salt solution) were free of vegetable matter and of crystals, but glass fragments and other impurities were present. The average number of foreign particles in the solutions of hydroxypropylmethylcellulose (91.2 and 96.7 particles per milliliter for each of the two groups) was statistically greater than in the balanced salt solutions (13.7 particles per milliliter).

Viscoelastic substances in ophthalmology

The desirable properties of a viscoelastic substance for ophthalmologic applications are intimately tied to its chemical and rheologic properties. This report describes the relevant rheologic properties (e.g., viscosity, viscoelasticity, pseudoplasticity, cohesiveness, and coatability) of the available viscoelastic substances and presents the general principles of their use as well as some specific technical aspects. In addition, the various uses of viscoelastic substances in ophthalmic surgery are outlined. There is no single ideal substance for all circumstances. With a knowledge of the rheologic properties of each substance, the ophthalmologist will be able to choose among the different ones as necessary to suit each clinical situation.

Hydroxypropyl methylcellulose in extracapsular cataract surgery with intraocular lens implantation: intraocular pressure and inflammatory response

We studied prospectively the effects of 2% hydroxypropylmethylcellulose (HPMC), instilled in to the anterior chamber during extracapsular cataract extraction with posterior chamber intraocular lens implantation in 122 patients. Significant pressure rise was noted at 12 and 24 hours post-operatively when HPMC was not removed at the end of surgery. This was prevented by washing HPMC from the anterior chamber at the end of surgery, or by using either acetazolamide or a combination of oxyphenbutazone and vitamin C without washing HPMC. There was no difference in intraocular inflammation between controls and the HPMC groups. The group receiving combined oxyphenbutazone and vitamin C had the least, the differences between these two groups being sufficient.

Comparison of hydroxypropyl methylcellulose 2% (Adatocel) and hyaluronic acid 1% (Healon)

Hydroxypropyl methylcellulose solutions (2% HPMC) were examined for impurities. There was no evidence of any particulate matter in two solutions from different sources: one prepared by a hospital pharmacy, the other industrially prepared (Adatocel). In a controlled clinical study, Adatocel was compared with Healon (1% hyaluronic acid solution). The postoperative irritation (cellular response) in the anterior chamber was the same in both groups.

Air, methylcellulose, sodium hyaluronate and the corneal endothelium. Endothelial protective agents

In a randomised trial the endothelial protective agent used during extracapsular cataract extraction and intraocular lens insertion was air in 19 eyes (group 1), methylcellulose in 25 eyes (group 2) and sodium hyaluronate in 22 (group 3). The cell population densities of each eye were estimated immediately before and three months after the operations to determine the degree of cell loss. Eyes showing mechanical (touch) damage on the second postoperative day were eliminated. The numbers of eyes in each group which showed a statistically significant cell loss were compared, and the mean cell losses in each group were tested for significant differences. It appears that air actually damages the endothelium while methylcellulose and Na-hyaluronate are not harmful, and afford a high, essentially equal degree of endothelial protection.