Volume 5, Number 14
Monday, April 11, 2005



In this issue: (click heading to view article)
Editorial: A Technological Explosion
CCT and Thickness of the Lamina Cribrosa in Human Eyes
Macular and RNFL Analysis of Normal and Glaucomatous Eyes in Children Using OCT
Twin Study of Age-related Macular Degeneration: Genetic and Environmental Influences
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Editorial: A Technological Explosion

We in ophthalmology are witnessing a technological explosion. It seems that we can hardly make it through a day without hearing about yet another FDA approval of this device or that treatment. I will predict that as technology continues to make steady strides, we will continue to enjoy a steady stream of enhancements to our pharmacologic armamentaria and surgical devices.

Just stop and think about this for a moment. We can now attack the inflammatory basis of dry eye with topical Restasis and be assured that several pharmacologic agents that are in trials will further improve dry eye therapy. Additionally, we have better topical fluoroquinolone antibiotics than ever before--just as we began to witness a disturbing rise in bacterial resistance and rates of endophthalmitis.

Surgically speaking, we continue to make remarkable strides toward better visual quality and function for ever-expanding ranges of refractive errors, using wavefront-driven excimer ablations. Simultaneously, next-generation microkeratomes from several manufacturers are now available, while the IntraLase platform is achieving greater levels of sophistication and use.

Those among us who operate within the eye have enjoyed safer surgery with greater control during some of the most difficult cataract procedures, thanks to capsular tension rings. Retinal surgeons are benefiting their AMD patients via Macugen. Additionally, we are winning the war on the final frontier of presbyopia with the technology of Conductive Keratoplasty (CK), and we can now offer many patients broader ranges of visual restoration following lens removal surgery with the recent approvals of ReZoom and ReSTOR IOLs, in addition to the previously approved Crystalens technology.

These are exciting times--but they are also challenging times for all ophthalmologists. We must return to our days of training, when we were taught how to assess critical data and clinical studies to distill the facts and make the best, safest and most efficacious choices for our patients. Ophthalmologists must also share their experiences with these technologies, so that we as a community of ocular health care providers remain on the cutting edge of patient care.
Stephen E. Pascucci, MD
Medical Editor
[email protected]

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CCT and Thickness of the Lamina Cribrosa in Human Eyes

Since central corneal thickness (CCT) may inversely influence the amount and rate of progression of glaucomatous optic nerve damage, and because lamina cribrosa thickness may be of importance in susceptibility to glaucoma, investigators at Germany’s University of Heidelberg aimed to evaluate whether CCT is related to lamina cribrosa thickness.

The histomorphometric study included 111 enucleated nonglaucomatous eyes of 111 white subjects. On anterior-posterior histologic sections through the pupil and the central optic disc region, researchers measured the thickness of the cornea, lamina cribrosa and peripapillary sclera and the shortest distance between the intraocular space and the cerebrospinal fluid space. Axial length ranged between 20 and 32 mm.

Mean CCT (mean +/- SD: 616.6 +/- 108.3 µm) and mean central lamina cribrosa thickness (378.1 +/- 117.8 µm m) were statistically independent of each other. In a similar manner, lamina cribrosa thickness at the optic disc border was statistically independent of CCT and peripheral corneal thickness. In a parallel way, peripapillary scleral thickness and the shortest distance between the prelaminar space and cerebrospinal fluid space were statistically independent of CCT.

The authors of the study believe that histologic artifact and sectioning methods could partially account for the lack of an association. The study results may suggest clinically that an assumed relationship between CCT and susceptibility to glaucoma cannot be explained by an anatomic correspondence between corneal thickness and histomorphometry of the optic nerve head.

SOURCE: Jonas JB, Holbach L. Central corneal thickness and thickness of the lamina cribrosa in human eyes. Invest Ophthalmol Vis Sci 2005;46(4):1275-9.		 Table of Contents












Macular and RNFL Analysis of Normal and Glaucomatous Eyes in Children Using OCT

Researchers at Duke University Eye Center (Durham, NC), have found differences between normal and glaucomatous eyes in children--similar to that reported in adult studies--using optical coherence tomography (OCT). They believe that using OCT in children may prove valuable in the early diagnosis of glaucoma.

The observational, cross-sectional institutional study included 156 eyes of 79 patients. Fifty-two eyes (33.3 percent) met criteria for glaucoma and 104 (66.7 percent) were normal. Forty-four female (55.6 percent) and 35 male (44.3 percent) subjects ranging in age from three to 17 years old (mean 9.5 years, standard deviation 3.5 years, median 9 years) were studied. Investigators used the OCT-3 (Carl Zeiss Meditec, Dublin, CA) to obtain a fast macular thickness map and a fast RNFL map of each eye. They analyzed data from specific locations around the macula, as well as total macular volume. Similarly, the RNFL scan reports average NFL thickness from specific locations around the optic nerve. Data from the superior temporal and inferior temporal sections was analyzed.

Results showed a statistically significant difference in macular thickness and NFL thickness when normal eyes were compared against those with glaucoma, in all quadrants studied. Mean macular volume was 7.01 +/- 0.42 mm(3) vs. 6.57 +/- 0.85 mm(3) for normal vs. glaucomatous eyes, respectively. The authors suggest that further investigation of OCT testing in children be considered.

SOURCE: Hess DB, Asrani SG, Bhide MG, et al. Macular and retinal nerve fiber layer analysis of normal and glaucomatous eyes in children using optical coherence tomography. Am J Ophthalmol 2005;139(3):509-17. 		Table of Contents






Twin Study of Age-related Macular Degeneration: Genetic and Environmental Influences

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness among older individuals in many parts of the world. The relative importance of genes and environment in the etiology of this major public health problem is not well understood, however. Investigators at the Massachusetts Eye and Ear Infirmary at Harvard Medical School, Boston, recently conducted a study on living twins in the United states to determine the impact of genetic and environmental factors on AMD.

Participants included living twins in the National Academy of Sciences-National Research Council World War II Veteran Twin Registry born between 1917 and 1927. Twins were surveyed for the known presence of AMD. Enrolled twins underwent a standardized examination and fundus photography. Researchers completed AMD evaluation for 840 elderly male twins, 210 monozygotic and 181 dizygotic complete twin pairs, both concordant and discordant, for presence or absence of AMD, and 58 singletons. They employed a bivariate twin model incorporating initial screening ascertainment and age effects to partition variation in liability to AMD and signs of maculopathy into additive genetic, common environment and unique environment components.

Of the 840 twins, 331 had no signs of maculopathy and 241 had early signs, while 162 had intermediate AMD and 106 had advanced AMD. Heritability (additive genetic) estimates were significant for overall AMD grade (0.46) and for intermediate (0.67) and advanced (0.71) AMD. Significant unique environmental proportions of variance were also evident for these AMD variables (0.37, 0.19 and 0.24, respectively). Shared or common environmental contributions were not significant (0.05 to 0.17). For specific macular drusen and retinal pigment epithelial characteristics, significant genetic (0.26 to 0.71) and unique environmental (0.28 to 0.64) proportions of variance were detected.

Investigators concluded that genetic factors play a substantial role in the etiology of AMD and associated macular characteristics, explaining 46 to 71 percent of the variation in the overall severity of the disease. Environmental factors unique to each twin also contribute to the occurrence of this disease. The authors of the study believe that this quantification of relative genetic and environmental contributions to the development of AMD should guide future research on the disease.

SOURCE: Seddon JM, Cote J, Page WF, et al. The U.S. twin study of age-related macular degeneration: relative roles of genetic and environmental influences. Arch Ophthalmol 2005;123(3):321-7. 		Table of Contents





BRIEFLY
  • ISTA EARNS FDA APPROVAL FOR XIBROM. ISTA Pharmaceuticals, Inc., has received FDA approval for Xibrom (bromfenac ophthalmic solution 0.09%) for the treatment of ocular inflammation following cataract surgery. The company expects to launch the topical, twice-daily, non-steroidal anti-inflammatory solution during the second quarter of 2005, after securing commercial quantities of the product from its manufacturer and completing the further expansion of its sales force. Xibrom is the first twice-daily ophthalmic NSAID to be approved in the United States (other ophthalmic NSAIDs are dosed four times daily). Senju Pharmaceuticals Co., Ltd., is has marketed the product in Japan since 2000; ISTA acquired U.S. marketing rights for Xibrom in May 2002 under a license from Senju. The company completed two pivotal Phase III clinical studies of Xibrom in the United States involving 527 patients. In the studies, a statistically significant proportion of patients treated with Xibrom achieved treatment success (defined as the complete absence of ocular inflammation), compared to placebo patients. This effect was evident in the Xibrom group as early as Day 3 following initiation of treatment. ISTA filed its New Drug Application for Xibrom in May 2004. For more information, go to www.istavision.com.
  • AMO REZOOM MULTIFOCAL REFRACTIVE IOL EARNS FDA APPROVAL. Advanced Medical Optics, Inc. (AMO) has received approval from the FDA for its ReZoom multifocal refractive intraocular lens (IOL) for cataract patients. The ReZoom IOL is a newly designed three-piece multifocal IOL that incorporates optics which distribute light over five optical zones for enhanced restoration of visual function, providing distance, intermediate and near vision for reduced spectacle dependence. Both the ReZoom and AMO’s Tecnis Multifocal IOL have CE Mark approval in Europe for the treatment of presbyopia. For more information, go to www.amo-inc.com.
  • EPI-K APPROVED FOR SALE IN U.S., EUROPE, AND JAPAN. Moria has received FDA approval for marketing its Epi-K disposable epikeratome for Epi-LASIK in the United States. The device has also recently received a CE Mark that authorizes its sale in the European Community, and it has been approved for sale in Japan. The Epi-K is used to mechanically separate the epithelium from Bowman’s membrane. The epithelial flap is then folded back before laser ablation and is subsequently returned to its original position. The procedure preserves the structural integrity of the stroma and is expected to minimize discomfort, shorten the length of visual recovery and reduce the incidence of haze associated with other surface ablation procedures, such as PRK and LASEK. The device underwent clinical trials at 13 sites in nine countries on more than 500 eyes. All clinical investigators reported that the Epi-K produced very high-quality epithelial flaps and that postoperative pain and visual recovery compared favorably with other surface ablation procedures. Moria plans to begin filling orders for the Epi-K in late April 2005.
  • FDA APPROVES B&L PUREVISION TORIC CONTACT LENS. The FDA has approved the sale of Bausch & Lomb’s PureVision Toric (balafilcon A) visibility tinted contact lenses in the United States for vision correction in people with astigmatism. The lens is indicated for the correction of refractive ametropia and or hyperopia with astigmatism of up to 5.00D. It is designed for monthly replacement and has been approved for daily wear or up to 30 days of continuous wear. The company plans to introduce the PureVision Toric lens in the United States in the summer of 2005; it is currently available in markets around the world, including Europe, Canada and Australia.


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