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March 2011

Journal Highlights
New Findings from Ophthalmology, AJO and Archives
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March’s Ophthalmology:

March’s American Journal of Ophthalmology:

January’s Archives of Ophthalmology:

Roundup of Other Journals:



Comparison of Ahmed Glaucoma Valve and Baerveldt Glaucoma Implant
March’s Ophthalmology

Budenz et al. implemented a five-year study comparing efficacy and complications of the Ahmed glaucoma valve (AGV) with the Baerveldt glaucoma implant (BGI) model 101-350.

The randomized clinical trial involved 143 patients with refractory glaucoma in the AGV group and 133 in the BGI group. At one year of follow-up, the researchers found that while IOP reduction was greater with the BGI, fewer early and serious complications were reported with the AGV. IOP was reduced from 31.2 ± 11.2 mmHg to 15.4 ± 5.5 mmHg in the AGV group and from 31.8 ± 12.5 mmHg to 13.2 ± 6.8 mmHg in the BGI group. Serious postoperative complications occurred in 20 percent of AGV patients and in 34 percent of BGI patients.

The authors conclude that IOP reduction with these devices must be weighed against adverse events. Consequently, the study at one year does not demonstrate clear superiority of one implant over the other. The researchers will follow these patients up to five years.

Cataract Surgery With Trabecular Micro-Bypass Stent for Glaucoma Patients
March’s Ophthalmology

Samuelson et al. conducted a multicenter study comparing cataract surgery with a glaucoma drainage device vs. cataract surgery alone in patients with mild to moderate open-angle glaucoma.

The investigators found that the cataract surgery patients who received the device demonstrated clinical and statistically significant improvement in IOP reduction and used less medication than those who underwent cataract surgery alone.

The investigators randomized 240 eyes into two groups: a treatment group that underwent cataract surgery with trabecular micro-bypass stent implantation and a control group that underwent cataract surgery only. At one year, 66 percent of treatment eyes (vs. 48 percent of control eyes) achieved greater than 20 percent IOP reduction without medication. Incidence of adverse events was similar in both groups.

The researchers assert that the stent is a positive benefit-risk intervention in patients with mild to moderate glaucoma undergoing cataract surgery. This novel therapeutic approach is intended to avoid the lifelong risk of complications that can be associated with filtering blebs.

Vision Loss in Ranibizumab Trials
March’s Ophthalmology

Reports of visual acuity loss in the MARINA and ANCHOR trials prompted a retrospective study by Rosenfeld et al. to identify possible risk factors and causes.

The researchers compared differences in lesion characteristics between patients who lost more than 15 letters of visual acuity from baseline to two years (9 percent in MARINA and 10 percent in ANCHOR) vs. patients who gained more than 15 letters (30 percent in MARINA and 38 percent in ANCHOR).

The authors found that the lesion characteristics most closely associated with visual acuity loss included pigmentary abnormalities, atrophic scar and choroidal neovascularization in the absence of leakage—all of which are associated with suppressed choroidal neovascularization.

The authors conclude that, in the future, patients undergoing anti-VEGF therapy might benefit from additional therapies now being developed that involve preservation of photoreceptor and retinal pigment epithelium function.

American Journal of Ophthalmology

Economic Evaluation of DALK and Penetrating Keratoplasty
March’s AJO

Van den Biggelaar et al. evaluated the cost effectiveness of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK).

Fifty-three patients with corneal stromal pathologic features not affecting the endothelium were included in the study: 28 patients in the DALK group and 25 in the PK group. Quality of life was measured before surgery and three, six and 12 months after surgery. The main outcome measures were incremental cost-effectiveness ratios per clinically improved patient on the 25-item National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25) and cost-effectiveness ratios per patient with endothelial cell loss of no more than 20 percent within the first year.

The authors’ analysis demonstrated that DALK was more costly than PK—mean total bootstrapped costs per patient were $10,498 in the DALK group and $9,042 in the PK group. However, change scores on the NEI VFQ-25 composite score were higher in the DALK group, resulting in an incremental cost-effectiveness ratio of $13,768 per clinically improved patient on the NEI VFQ-25.

Endothelial cell loss was lower in DALK patients as compared with PK patients, resulting in a ratio of $9,522 per patient with an endothelial cell loss of no more than 20 percent within the first year. In DALK patients without perforation of Descemet’s membrane, the authors found a ratio of $10,925 per clinically improved patient on the NEI VFQ-25 and a ratio of $7,245 per patient with an endothelial cell loss of no more than 20 percent. Visual outcomes were comparable between DALK and PK patients.

The authors conclude that DALK is more costly and more effective than PK. Self-reported results from the NEI VFQ-25 were in favor of DALK, and endothelial cell loss in DALK patients remained stable after six months, whereas cell loss in PK patients continued. DALK procedures performed without perforation of the Descemet’s membrane were even more effective.

Evaluation of IOL Tilt With Anterior Segment OCT
March’s AJO

Kumar et al. evaluated the ability of anterior segment OCT to detect IOL tilt in relation to the limbus.

The IOL position in 123 eyes of 92 patients was examined with anterior segment OCT. All eyes underwent uneventful phacoemulsification with the IOL in the bag. Images were obtained in four axes (180 to 0 degrees, 225 to 45 degrees, 315 to 135 degrees and 270 to 90 degrees).

The authors analyzed the OCT images and determined the distance between the iris margin and the anterior surface of IOL, the slope ratio between IOL and limbus, and the slope angle (or the position of IOL with reference to the limbus). They then correlated these with the astigmatism and vision.

The mean slope of the limbus and the IOL in all axes was 0.003 and –0.002, respectively. The average slope ratio was 1.1, and the slope angle was 1.52 degrees. The mean ocular residual astigmatism was 0.2379 D. There was no significant correlation of ocular residual astigmatism with slope ratio and slope angle. There was significant correlation of ocular residual astigmatism with total astigmatism. The mean distances between the iris margin and the anterior surface of IOL were 0.80 mm and 0.83 mm, respectively.

Wound Architecture of Clear Corneal Incision With or Without Stromal Hydration
March’s AJO

Using 3-D OCT of the cornea and anterior segment, Fukuda et al. evaluated wound architectures of a clear corneal incision and the duration of stromal edema caused by intentional hydration in cataract surgery.

Cataract surgery was performed through a clear corneal incision created with a 2.4-mm blade in 30 eyes of 23 patients. After confirming the watertightness of the clear corneal incision at the end of surgery, 15 randomly selected eyes received stromal hydration—the remaining 15 eyes did not. Using OCT, wound architecture was assessed at one day, one week and two weeks after surgery.

In eyes with stromal hydration, corneal thickness at the clear corneal incision was 1020.5 ± 98 µm, 908.9 ± 54.4 µm and 795.7 ± 57.6 µm at one day, one week and two weeks after surgery, respectively. In eyes without stromal hydration, corneal thickness at the clear corneal incision was 880.3 ± 79.6 µm, 840.3 ± 92 µm and 799.3 ± 93.6 µm at one day, one week and two weeks after surgery, respectively. A statistically significant difference was noted between the two groups at one day and one week after surgery. There was no significant difference between the two groups at two weeks after surgery.

Eyes that received stromal hydration tended to show greater incidence of gaping at the endothelial and epithelial side, misalignment of the incision roof and floor, and local detachment of Descemet’s membrane.

Archives of Ophthalmology

“No-Touch” Isolated Descemet’s Membrane Endothelial Keratoplasty
January’s Archives

Dapena et al. described a standardized technique for “no-touch” isolated Descemet’s membrane endothelial keratoplasty (DMEK), including preoperative patient preparation, descemetorhexis “under air,” graft implantation, appositioning and fixation.

In the management of Fuchs endothelial dystrophy, the “no-touch” DMEK technique may provide a BCVA of greater than or equal to 20/25 in about 75 percent of cases and an endothelial cell density of about 1,800 to 2,000 cells/mm2 at six months after surgery. The incidence of major complications after endothelial keratoplasty—graft detachment from the recipient posterior stroma—may be reduced by taking some pre-, intra- and postoperative precautions.

The authors conclude that this DMEK technique may be a safe and effective procedure for treatment of corneal endothelial disorders. They also report that it may make endothelial keratoplasty accessible to most cornea surgeons without requiring major investments and provide an unprecedented visual rehabilitation rate and outcome.

AMD Prevalence in NHANES
January’s Archives

Klein et al. examined the prevalence of age-related macular degeneration in Caucasians, African-Americans, Mexican-Americans and other racial/ethnic groups in a representative sample of the noninstitutionalized U.S. population 40 years of age or older participating in the 2005-to-2008 National Health and Nutrition Examination Survey (NHANES).

AMD was determined by the grading of 45-degree digital images from both eyes using a standardized protocol. The estimated prevalence of any AMD in the U.S. population aged 40 years and older was 6.5 percent, and 0.8 percent had late AMD. African-Americans 60 years of age and older had statistically significant lower prevalence of any AMD than Caucasians. Overall, the prevalence of any AMD in NHANES was lower than the 9.4 percent reported in the 1988-to-1994 NHANES study. These estimates are consistent with a falling incidence of AMD found in the Beaver Dam Eye Study.

The reason for the decline in the prevalence of AMD is not known. While it might be explained by possible methodological differences in the surveys done at different time periods, it may reflect changes over time in smoking, physical activity, blood pressure, diet and other factors associated with AMD in the population.

Retinal Venular Diameter and Diabetic Retinopathy
January’s Archives

Roy et al. examined the relationship between retinal arteriolar and venular diameter and the six-year progression of diabetic retinopathy (DR) in African-Americans with type 1 diabetes mellitus.

The researchers included 468 African- Americans with type 1 diabetes who participated in the New Jersey 725 study and had undergone a six-year follow-up exam. Seven standard field retinal photographs were obtained at baseline and at the follow-up exam. Computer-assisted grading of digitized baseline retinal photographs was conducted to determine the average diameter of retinal arterioles—central retinal arteriolar equivalent (CRAE)—and venules—central retinal venular equivalent (CRVE). Retinal vessel diameter was examined in relation to the six-year incidence and/or progression of DR.

For right and left eyes, mean CRAE was 168.8 µm and mean CRVE was 254.2 µm at six-year follow-up. Both CRAE and CRVE were correlated between eyes. Multivariate analysis with generalized estimating equations showed that larger CRVE in either the right or left eye was significantly associated with six-year progression to either proliferative DR or proliferative DR with high-risk characteristics after adjusting for baseline clinical risk factors.

Notably, a significant association between baseline CRVE and progression to proliferative DR was present for eyes with low-to-moderate nonproliferative DR. The same association was also found between baseline CRVE and progression to proliferative DR with high-risk characteristics for eyes with either no or nonproliferative DR.

Ophthalmology summaries are written by Lori Baker Schena, PhD, and edited by John Kerrison, MD. American Journal of Ophthalmology summaries are edited by Thomas J. Liesegang, MD. Archives of Ophthalmology summaries are written by the lead authors.

Roundup of Other Journals

Collagen Genes May Influence Central Corneal Thickness
Human Molecular Genetics
Published online Nov. 23, 2010

Given that central corneal thickness (CCT) is a risk factor for glaucoma, Vithana et al. conducted two genome-wide association studies in an attempt to identify the genetic determinants affecting CCT.

The study involved members of two ethnic populations in Singapore: 2,538 Indian individuals and 2,542 Malay individuals. The investigators identified two novel genetic loci associated with CCT—1p34.3 near COL8A2 and 9q34 at the interval between RXRA and COL5A1. In addition, they confirmed an association with CCT at a previously identified ZNF469 locus.

Results from this research prompted the authors to conclude that the collagen-related genes expressed within the cornea represent novel candidates with which to study the cause of primary open-angle glaucoma. They further hypothesize that a true biological link could exist between CCT and primary open-angle glaucoma through corneal collagen-related genes that not only modulate CCT but perhaps, also, influence the pathological changes that occur in ocular tissues in patients with glaucoma.

Topical Anesthetics Are Effective for Intravitreal Injections
Published online Nov. 22, 2010

Blaha et al. found that four commonly used topical anesthetic methods for intravitreal injection are equally effective in limiting the pain associated with this procedure.

The study involved 24 patients who each received four intravitreal injections after being administered each of four different types of anesthesia: proparacaine, tetracaine, a lidocaine pledget and a subconjunctival injection of lidocaine. Each patient scored the four different anesthetics and intravitreal injections on a pain scale of 0 to 10 in a randomized block design.

Results indicated that the combined pain scores for the anesthesia method and intravitreal injection were not statistically different. The patients gave a 4.4 average pain score for the lidocaine pledget, 3.5 for the topical proparacaine, 3.8 for the subconjunctival lidocaine injection and 4.1 for the topical tetracaine. The subconjunctival lidocaine had the most side effects, with 54 percent of eyes developing a subconjunctival hemorrhage.

Handheld OCT for Office Settings
IEEE Transactions on Biomechanical Engineering
Published online Dec. 3, 2010

Jung et al. reported on their creation of a handheld OCT scanner that has the potential to be used in the primary care office setting. The handheld OCT features a pair of computer-controlled galvanometer-mounted mirrors, interchangeable lens mounts and a miniaturized video camera.

To test the performance of this new device, the authors imaged the anterior chamber of a rat eye and an in vivo human retina, cornea and tympanic membrane. To image both the anterior and posterior chambers of the eye, a soft eyecup was attached to the lens mount. This proved comfortable for the patient and matched the focal length of the eye while offering flexibility for angular positioning. The device was able to provide fast 2-D imaging without motion artifacts as well as high-resolution 3-D imaging. Currently, however, the imaging speed of the device cannot provide full 3-D imaging in the clinic, but the authors are working toward this capability.

Roundup of Other Journals is written by Lori Baker Schena, PhD, and edited by Deepak P. Edward, MD.

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