According to researchers in Iran, the Orbscan II, compared to the Pentacam, yielded larger posterior elevation values before and after surgery and significant postoperative changes in posterior central elevation and posterior maximum elevation.

In this prospective, observational case-series study, 23 consecutive myopic patients having laser refractive surgery were examined with the Orbscan II and Pentacam preoperatively and six weeks postoperatively. Readings of anterior chamber depth (ACD), anterior (A-) and posterior (P-) best-fit sphere (BFS) size, central elevation (CE), maximum elevation (ME), axial power in the 3-mm (AX3) and 5-mm zones (AX5) and tangential power in these zones (TG3 and TG5, respectively) were collected and used in the analyses.

Forty-six eyes were examined at the pre- and postop visits. Mean patient age was 28 years (range, 21 to 41 years), and 74 percent were women. The mean spherical equivalent refraction was -4.3 D (range, -9.13 to -2.13 D) preop and 0.1 D (range, -0.63 to 1 D) six weeks postop. Thirty eyes had LASIK, 10 had PRK and six had PRK plus mitomycin-C.

The pre- and postop ACD readings differed significantly between the Orbscan II and Pentacam. At both examinations, the Pentacam gave higher readings overall. After surgery, there was a mean decrease in ACD readings of 0.02 ±0.06 mm with the Orbscan (p=0.002) and 0.06 ±0.05 mm with the Pentacam (p<0.001). In preop corneas, the devices generated statistically significantly different readings in measurements of all anterior corneal parameters. In operated eyes, there was a statistically significant difference for measurements of A-AX3 and A-AX5. The two devices showed a similar amount of postop change in anterior curvature parameters, but the postop changes in elevation values were significantly different.

Measurements were statistically significantly different in cases of all posterior corneal parameters in pre- and postop eyes except for preop P-TG3 (p=0.014). Pre- and postop Orbscan measurements showed statistically significant differences except for P-AX5 (p=0.004) and P-TG5 (p=0.034), while with the Pentacam, there was no significant postop change in any corneal variable. Compared with Pentacam values, the postop changes with the Orbscan were significantly greater for all posterior corneal parameters except P-AX5 (p=0.045) and P-TG5 (p=0.062).

The researchers admit the Orbscan's limitations and possible sources of error, as well as the relatively small sample size, limit their findings. They suggest further studies to investigate the occurrence of significant posterior corneal changes with the Pentacam and possibly other advanced systems, and to determine the role of factors like ablation depth, intraocular pressure, residual stromal thickness and corneal curvature.

(J Cataract Refract Surg 2007;33:841-847)

Hashemi H, Mehravaran S.


Postop Complications in DLEK


In a recent study, researchers in Canada and Israel found that nonadhesion of the disc and elevated intraocular pressure were the most common complications after deep lamellar endothelial keratoplasty.

They reviewed the charts of 44 patients who underwent DLEK, all by one surgeon on one eye of each patient. Preop examination included Snellen chart, a full slit-lamp examination of the anterior segment and of the posterior pole, measurement of intraocular pressure, ultrasonic corneal pachymetry and endothelial cell count measured by specular microscope. The same examinations were performed after surgery. Specular microscopy was performed on all donor corneas in the eye bank. All complications occurring between one day and eight weeks after surgery were identified and recorded. Follow-up was six weeks to 26 months.

The mean age of the 44 patients was 73.4 ±10.6 years. Thirty-one were women, 13 men. Sixteen patients (36.4 percent) had Fuchs' endothelial dystrophy. Phacoemulsification with the insertion of a foldable intraocular lens in the bag was performed as the first stage of surgery in 15 of these 16 patients. Twenty-eight patients (63.6 percent) had pseudophakic or aphakic bullous keratopathy. Three of the pseudophakic patients had an anterior chamber IOL, which was replaced with a posterior chamber lens during DLEK. In one of the 24 patients with a posterior chamber IOL, the lens was malpositioned and replaced during DLEK. An IOL was inserted into the posterior chamber at the time of surgery in the aphakic patient. Ten  patients (22.7 percent) had open-angle glaucoma before surgery, controlled medically in nine, and in one by trabeculectomy, before DLEK.

In 23 patients (52.3 percent), there was complete adhesion of the corneal disc the day after surgery. In six patients (13.6 percent), the disc was floating freely in the anterior chamber on the first postop day. The disc was repositioned using a 30-ga. needle. In eight patients (18.2 percent), fluid was present between the disc and cornea; in six of them, the fluid was absorbed spontaneously. In two patients, the fluid was aspirated one month after surgery, but fibrosis developed in the interface. Two patients (4.5 percent) had persistent corneal edema after surgery. In one patient, the edema resolved, but the other needed penetrating keratoplasty. One patient (2.3 percent) developed endothelial graft rejection seven weeks after surgery when steroid treatment was discontinued because of exacerbation of preexisting glaucoma. The graft did not recover, and PKP was eventually performed. Thirteen patients (29.5 percent) had elevated IOP postop, including the 10 with glaucoma preop. IOP was controlled in seven of these 10 patients with topical medication. Three patients (6.8 percent) without glaucoma preop developed elevated IOP postop, which was controlled with topical medication.

The researchers state their series is difficult to compare with similar reports because they operated only on patients with Fuchs' dystrophy and bullous keratopathy whereas previous reports of PKP included eyes with keratoconus and corneal scars. The researchers believe the incidence of complications may be influenced by the technical learning curve and by the tissue available from the eye bank. The mechanical preparation of a thinner donor disc may enhance adhesion and more experience may lead to fewer postop complications and better management when they occur.

(Cornea 2007;26:650-653)

Hyams M, Segev F, Yepes N, Slomovic AR, Rootman DS.