ARVO Highlights

We highlight six of the most interesting 2012 presentations.

By Jerry Helzner, Senior Editor

Each year, the annual ARVO meeting offers a treasure trove of new information, consisting of several thousand presentations focusing on numerous and varied areas of ophthalmic research. Having spent countless hours painstakingly sifting through the abstracts for many of these presentations, I have come up with six highly interesting and relevant presentations that we are highlighting here.

Rejection Risk of Several Corneal Transplant Techniques

Marianne and Francis Price, the corneal experts who oversee the highly respected and authoritative Cornea Research Foundation of America in Indianapolis, have conducted a fairly large-scale study of immunologic rejection risk with four transplant techniques for endothelial dysfunction.

The four techniques studied were penetrating keratoplasty (PK), Descemet's stripping endothelial keratoplasty (DSEK), Descemet's membrane endothelial keratoplasty (DMEK) and Descemet's membrane automated endothelial keratoplasty (DMAEK).

The researchers reported at ARVO that data was collected prospectively on 200 consecutive DMEK and 100 consecutive DMAEK cases. The rate and timing of rejection episodes was compared retrospectively with previously reported results in a series of 598 DSEK cases and 30 PK cases performed at the same center, using the same postoperative corticosteroid regimen and the same evaluation criteria for rejection episodes. The standard corticosteroid regimen consisted of prednisolone acetate 1% eye drops instilled four times daily for four months, tapered by one drop per month to once daily and continued indefinitely.

Overall, 89% of the grafts were performed to treat Fuchs' endothelial dystrophy, 62% of the graft recipients were female and 96% were Caucasian. These relative proportions were comparable in all four transplant groups. At two years, the Kaplan-Meier cumulative rejection-free survival rate was 99.4% for DMEK, 95% for DMAEK, 88% for DSEK and 82% for PK. The researchers found that relative risk of a rejection episode was substantially higher with PK than with any of the endothelial keratoplasty techniques. The relative risk of experiencing a rejection episode was six times lower with DMEK than DMAEK and 2.8 times lower with DMAEK than with DSEK.

A DSAEK procedure showing donor tissue being centered in the anterior chamber.

The researchers concluded that the relative risk of experiencing an immunologic rejection episode decreased as the amount of donor stromal tissue in the graft decreased, and the risk of rejection was lowest when donor stromal tissue was eliminated. They noted that this finding is consistent with studies showing that the corneal endothelium may be relatively immune-privileged.

As a result of these findings, a multicenter, prospective randomized study has been initiated to determine if corticosteroid strength can be reduced after DMEK to avoid steroid-associated side effects without unduly increasing the risk of graft rejection.

Relative Costs of Transplant Tissue

Staying in the area of corneal transplant, Michael Chen, MD, and Bennie Jeng, MD, of the University of California San Francisco ophthalmology department, conducted an interesting study comparing the costs of surgeon-cut donor corneal tissue versus eye bank-cut donor tissue for endothelial keratoplasty.

For this research, a model was constructed to compare the costs in a thorough and comprehensive manner. Cost analysis of surgeon-cut tissue was calculated using a “bottom-up” or “micro-costing” approach. Costs of equipment, consumable supplies, labor, building space and the risk of unsuccessful attempts resulting in damaged tissue were all considered. Costs of equipment and consumable supplies were based on the acquisition costs of the University of California San Francisco Medical Center. Cost of labor was based on the national wage estimates from the US Department of Labor Bureau of Labor Statistics. Cost of building space was estimated from the Building Owners and Managers Association Experience Exchange Report. Cost of risk of damaged tissue was estimated based on a local eye bank's rate of returned corneal tissue secondary to surgeon-induced damage, multiplied by the cost of an uncut donor cornea.

A technician at Heartland Lions Eye Bank in Kansas City, Mo., (left), processes tissue for use in corneal transplant procedures. At right is a close-up look, showing the precision nature of providing pre-cut tissue to ophthalmic surgeons.

The cost associated with an eye bank-cut donor cornea was based on the tissue processing fee of a local eye bank, which is a Medicare pass-through cost. All costs are reported in 2010 US dollars.

Assuming a five-year lifespan of the Moria Microkeratome (used to cut donor tissue), plus a team consisting of a surgeon, a registered nurse, a certified scrub technician and a sterilization technician; a time of 30 minutes to cut the cornea before the patient is brought into the operating room; a rate of 1% for returned corneal tissue secondary to surgeon-induced damage; and a 500-square-foot operating room, the cost per surgeon-cut donor cornea is $301.90, $376.90, $526.90, and $826.90 if the number of cases performed per year are 104, 52, 26, and 13, respectively. The processing fee of a local eye bank to cut the donor corneal tissue is approximately $750.

After factoring in all of the various cost elements, the researchers concluded that the cost per surgeon-cut donor corneal tissue decreases as the number of cases performed increases. Excluding other factors such as opportunity costs, the eye bank processing fee is equivalent to the cost associated with a surgeon-cut cornea if the surgeon were to perform 15 cases per year. The researchers noted that these calculations may influence the practice patterns of providers and may have implications for determining how third-party payer reimbursements are made.

Rates of Retinal Detachment in Resident-Performed Cataract Surgery

Moving to the area of cataract surgery, another group of researchers at the University of California San Francisco Ophthalmology Department tackled the issue of the rate of retinal detachment in resident-performed cataract surgery.

In this retrospective case-control study, 48 patients who developed retinal detachment (RD) after resident-performed cataract surgeries performed at San Francisco General Hospital and San Francisco Veterans Administration Medical Center between January 1, 1996 and December 20, 2009 were included as cases. One hundred and ninety two controls were randomly chosen from the list of all cataract surgery patients from this time period who did not develop RD in the ratio of four controls per one case without case-control matching.

Data was collected from medical records and analyzed using univariate analysis to compare the differences between two groups and using multivariate logistic regression analysis to identify variables that were associated with an increased risk of developing RD.

The researchers analyzed several major variables, including patient age, gender, axial length, vitreous loss and resident training year. Vitreous loss during cataract surgery and male patient gender were found to be statistically significant risk factors for developing RD. Conversely, increasing years of resident experience were associated with a reduction in the risk of RD. There was no statistically significant effect for patient age or axial length.

The researchers concluded that intraoperative vitreous loss and male patient gender were identified as risk factors for RD following resident-performed cataract surgery. The study also found evidence of a resident-year effect on RD development, with more years of training associated with less RD risk. The researchers noted that these findings may help direct future quality improvement efforts within resident surgical training programs and can serve as a basis for informed-consent discussions with patients considering cataract surgery with resident surgeons.

A Decade of LASEK Follow-up

Researchers from Vienna went back a decade to determine the long-term effectiveness, stability and safety of the LASEK procedure when performed with the Wavelight Allegretto laser.

In a retrospective study, researchers looked at 102 eyes of 63 patients with high myopia who underwent LASEK to correct their refractive error and received regular postoperative assesments for 10 years. Changes in uncorrected visual acuity (UCVA), manifest refraction, best spectacle-corrected visual acuity (BSCVA) and complications were evaluated.

Forty-two female and 21 male patients were enrolled. The mean age at time of surgery was 33.52 years (with a range from 20 to 56 years). The mean preoperative spherical equivalent (SE) was -7.71 D (with a range from -6.00 to -12.50 D). At 10-year follow-up, mean SE was -0.50 D (with a range from +0.75 to -2.75D).

UCVA (logMAR) improved from a mean preoperative 1.30 (range from 2.00 to 1.20) to 0.00 (range from -0.10 to 0.20) after surgery and revealed faint but significant decrease in the 10 years follow-up. No change in BSCVA was observed in any eye. The efficacy index (ratio between preop BSCVA and postop UCVA) was 83% at one month, 91% after one year and 89% after 10 years. No serious complications were observed.

The researchers concluded that LASEK surgery has been proven to be a safe and effective procedure to correct high myopia. They noted that the minimal myopic regression after 10 years is more pronounced in the younger patient group and may be attributable to naturally occurring myopic progression.

LASIK Retreatment After a Previously Aborted Procedure

Researchers in Mexico City conducted a study to compare the visual outcome of a second LASIK procedure one month after flap complications aborted the first LASIK attempt against outcomes reported in a second LASIK procedure after three- and six-month waiting periods.

The researchers retrospectively studied a series of 30 patients (30 eyes) who underwent a second LASIK after flap complications (irregular, thin, button-holed and incomplete flap). The second surgery was performed one month after the first refractive surgery attempt. UCVA and BCVA outcomes were studied.

In the 30 eyes studied, causes of aborted LASIK were identified as 18 incomplete flaps (60.0%), 10 irregular flaps (33.3%), and two buttonholed flaps (6.6%). The mean age for surgery was 28.1 years, with 25 right eyes (83.3%) and five left eyes (16.3%) included. The mean time for the second LASIK procedure was 49.03 days (range 29 to 70 days).

For the first procedure, a Moria microkeratome was used in 11 patients and the Hansatome microkeratome was used in 18 eyes. The second LASIK procedure was performed in all 30 eyes with a Hansatome microkeratome. Twenty seven of these eyes had a 180 µm final flap and three eyes had a 160µm final flap. The mean flap depth for the first LASIK was 140 µm and mean depth for second LASIK was 177µm.

Best spectacle-corrected visual acuity prior to first LASIK was 20 patients at 20/20, four patients at 20/15, three at 20/25) and three at 20/30. The final UCVA after the second LASIK was 17 patients at 20/20, nine at 20/25, two at 20/30, one at 20/15 and one at 20/40.

There was only one complication observed during the second LASIK, an irregular flap in one eye, but laser ablation was performed with a UCVA of 20/30.

The researchers concluded that a planned LASIK one month after flap complications resulted in satisfactory UCVA, comparable to procedures performed three or six months after the first LASIK.

Driving Patterns for Seniors

Researchers from Howard University and the Wilmer Eye Institute set out to document visual, cognitive and other factors among elderly drivers — differentiating among those who do and those who do not drive during nighttime hours.

The Salisbury Eye Evaluation and Driving Study is a longitudinal study of vision, cognition and driving behavior of older drivers living in or around Salisbury, Maryland. Subjects were recruited from a complete listing of all Maryland drivers ages 67 to 87 years.

The researchers reported on data from two visits, which both included real-time driving assessments using a driving monitor system installed in each participant's car for a five-day period and which monitored driving performance, including time of driving. All participants underwent a battery of cognitive and visual function testing. Night hours were defined according to seasonal variation.

Complete data was available for 990 of the 1080 participants attending both visits. Overall, 61% of participants maintained their driving patterns at both time points. They were either consistent in being night drivers or non-night drivers, while 39% changed their driving patterns between the visits. The researchers found that increasing age, female gender, poorer visual acuity and contrast sensitivity were significantly associated with not driving at night. Fewer miles driven and winter season of the participant's visit were also associated with not driving at night. The researchers found that self-restricting night driving is associated with multiple factors. OM