The endothelial cell count had to be at least 2,500 cells/mm2 if the patient was over 45 years.
Heparin coating A distinctive feature of this IOL is that it is coated in heparin to reduce inflammation and infection in the eye. The haptics are flexible to minimize pupil ovalization and angle compression. The optics are 6 mm with anti-reflective coating that reduces glare. In addition, the edge of the optic is thinner, which increases clearance of corneal endothelium. The lens is implanted into the anterior chamber and it rests on the iris, explained Dr. Goldberg, who just began a Cornea-External Disease fellowship at The University of Texas Southwestern Medical Center in Dallas.
One hundred eyes were included in this study, but only 14 eyes of patients of Tom Clinch, MD, were reviewed. Patients were between 21 and 55 years with no ocular diseases and had a best-corrected visual acuity level of 20/40 or better. The preoperative myopic refractive errors ranged from -4 to -20 D with astigmatism not exceeding 3 D.
Dr. Goldberg explained that before the procedure was performed two peripheral iridotomies were performed by YAG laser in the event that one closed before the procedure. The corneal incision that was created centered on the steepest axis to minimize astigmatism. A superior or temporal approach was used. The lens was placed over a lens slide into the anterior chamber. Surgical time ranged from 15 to 40 minutes, with the longer time occurring during the initial procedures in this series of patients.
Patients received steroids and antibiotics four times daily and were re-examined 1 day, 1 week, 1 month, 6 months, and 1 year postoperatively. Fourteen patients were followed for 18 months (preoperative refraction of -7 to -14 D).
"At 1 month after surgery, the mean uncorrected visual acuity was about 20/30; the mean spherical equivalent was -0.3 and the mean astigmatism, which represents an astigmatic shift because of the corneal incision, was about 0.75 D. After 4 weeks, this decreased and the mean uncorrected visual acuity remained at the same level," Dr. Goldberg reported.
"Equally important in this study was the endothelial cell density, which was measured using specular microscopy preoperatively, at 1 day, and at 1, 3, 6, 12, and 18 months postoperatively. The preoperative endothelial cell count was a mean of 3,079 cells/mm2 [±568 cells/mm2]. At 3 months postoperatively, this decreased to 2,987 cells/mm2 [±429.3 cells/mm2], representing a 3% loss of endothelial cells. At 18 months postoperatively, the cell density dropped to 2,944 cells/mm2 [±625 cells/ mm2], which was about a 4.4% loss," Dr. Goldberg stated.
Cell density loss A primary focus of this study was cell density loss of 10% or greater. Three patients had an endothelial cell loss of that magnitude. Two of them demonstrated this loss in two of the three corneal locations analyzed, and one patient had this loss in all three locations, according to Dr. Goldberg.
He speculated that the length of the surgery may have been responsible for the endothelial cell loss in two of the three patients, because they were among the first to receive the Phakic 6 H2 IOL. He also noted that a small anterior depth may have been a culprit.