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Heparin-surface-modified IOLs reduce postop inflammation, study shows
Suitable candidates for the HSM IOL are those with diabetes, certain types of glaucoma and iritis and those who have been subjected to multiple prior surgeries.
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GALVESTON, Texas - Patients who are diabetic or have glaucoma can definitely benefit from a heparin-surface-modified (HSM) IOL compared to a non-HSM PMMA IOL, according to a multicenter study.
"Heparin surface modification results in reduced foreign-body reaction as measured by specular micrography and slit-lamp examination, especially in the early postoperative period," said Stefan D. Trocme, MD, an associate professor and vice chairman of the Department of Ophthalmology and Visual Sciences at the University of Texas Medical Branch at Galveston.
---An acute inflammatory reaction occurs in all patients during the first postoperative days.
Dr. Trocme was first author of the study, which was recently published in Ophthalmology. "This is an extremely well-published implant. It has been around for about 15 years," he said. "However, it was only approved in the United States a few years ago. I suspect the reasons for such a delay were primarily administrative, because there is a vast amount of literature from Europe and elsewhere that indicates this implant does reduce the inflammatory response."
At the American Society of Cataract and Refractive Surgery annual meeting, Dr. Trocme shared highlights of the study, which is the only sizable one to have used phacoemulsification in virtually all patients. It is also the first U.S. patient-population study to document that heparin surface modification reduces postoperative inflammatory responses. Moreover, the patient population was 12% African-American and 83% Caucasian.
Three patient groups
---An immobile standard PMMA surface does not prevent protein adsorption and cell adhesion.A total of 367 patients from eight U.S. medical centers participated. There were 220 routine patients, 58 with glaucoma and 89 with diabetes. "This is the largest study to date that simultaneously evaluated various risk factors," Dr. Trocme said. "Past studies of the lens have tended to concentrate on glaucoma alone or diabetes alone." The present study is also significant in that phacoemulsification was used in 96% of routine patients, 98% of glaucoma patients and 94% of diabetic patients.
All implants were performed between August 1994 and October 1996 using a specific PMMA lens, the Model 815HS (Pharmacia & Upjohn B.V.; Groningen, The Netherlands). At each center, eligible patients were randomized to receive either the HSM lens or a lens without heparin surface modification. Overall, 183 patients were randomized to receive an HSM IOL and 184 a non-HSM IOL.
Patients were observed for 1 year after phacoemulsification and lens implantation (at 1 week, 1 month, 2 months, 6 months and 12 months). Cross-sectional analyses showed that at all follow-up visits, consistently fewer routine patients with HSM lens implants had giant cells on their IOLs than those with non-HSM lens implants. For example, at 3 months, "about four to five times as many non-HSM lenses had the presence of giant cells compared to HSM lenses," Dr. Trocme said. A statistical significance (P<0.05) was="" observed="" at="" all="" visits="" except="" at="" 12="">
In the glaucoma group, there were also significantly fewer HSM lenses with giant cells on the lens surface at 3 months (P=0.0116). However, "at every postoperative visit, the percentage of HSM patients observed to have giant cells on the lens surface was less than half the percentage of non-HSM patients reported to have giant cells. This finding can be considered clinically important," Dr. Trocme said. Likewise, in the diabetes group, significantly fewer patients with HSM IOLs had giant cells on the surface at all follow-up visits compared to non-HSM IOLs.
Cellular deposits
---The mobile surface molecules constitute a steric hindrance for protein adsorption and cell adhesion.
A similar pattern was observed in cellular deposits. For routine and diabetic patients, this difference reached statistical significance at 3 months, and among glaucoma patients, it was statistically significant at 3 and 6 months. Furthermore, longitudinal data analysis for occurrence of both giant cells and cellular deposits in each of the patient populations revealed a statistically significant difference in favor of the HSM IOL, except for the occurrence of cellular deposits in diabetic patients.
On the other hand, "we found no visual acuity differences," Dr. Trocme said. Safety was also comparable. Topical dexamethasone (1 mg/ml four times daily for 2 weeks and twice daily for 4 weeks) was administered as standard postoperative treatment."Additional anti-inflammatory treatment was permitted if necessary," Dr. Trocme said. However, there was no difference in anti-inflammatory treatment between groups.
Dr. Trocme said suitable candidates for the HSM IOL are those with diabetes, certain types of glaucoma, iritis and patients who have been subjected to multiple previous ocular surgical procedures. For glaucoma, "we're looking in particular at patients who have received long-term miotic medications - the kind of drops that actually constrict your pupil. These drops become more inflammatory when you operate on these patients." Glaucoma patients with pseudoexfoliation are also candidates.
For Your Information:Reference:
- Stefan D. Trocme, MD, can be reached at Department of Ophthalmology and Visual Sciences, Clinical Sciences Bldg., 301 University Blvd., Galveston, TX 77555-0787; (409) 772-8104; fax: (409) 772-8106; drtroc@aol.com. Dr. Trocme has no direct financial interest in any products mentioned in this article. He is a paid consultant for Pharmacia.
- Trocme SD, Li H. Effect of heparin-surface-modified intraocular lenses on postoperative inflammation after phacoemulsification. Ophthalmology. 2000;107:1031-1037.