Volume 5, Number 7
Monday, February 21, 2005



In this issue: (click heading to view article)
Longitudinal Observation of Severe ROP and Screening Implications
Computerized Corneal Topography in a Pediatric Population with Down Syndrome
Results of Excimer Laser Photorefractive Surgery After Three Epithelial Removal Techniques
Scanning Laser Tomography of Full-thickness Idiopathic Macular Holes
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Longitudinal Observation of Severe ROP and Screening Implications

Researchers at Canada’s University of Calgary, Alberta, recently conducted a retrospective longitudinal cohort study to test the effectiveness of the Canadian retinopathy of prematurity (ROP) screening guidelines as applied to high-risk premature infants.

Data from weekly ROP screening examination results were collected from a geographical area and analyzed. A total of 969 infants were examined longitudinally between 1991 and 2000; 46 of the infants screened were treated for severe ROP.

The average incidence of severe ROP requiring treatment in the population of premature infants eligible for screening was 48.3 per 1,000. In all, 46 infants were treated in the cohort. The mean gestational age (GA) was 25.5 weeks and the mean birth weight was 750 g (1.65 lbs.). The mean chronological age (CA) and postmenstrual age (PMA) at the time of first screening was 36 days and 30.7 weeks, respectively. The first identification of any ROP in this group was at a mean CA of 60 days and PMA of 34.1 weeks. The mean CA and PMA of the first observation of Stage 3 were 74 days and 36.3 weeks. The mean CA and PMA at the time of treatment were 86 days and 37.7 weeks.
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The authors believe that their observations and analysis suggest the following ROP screening recommendations: infants of 28 weeks of GA or less and infants with a GA between 28 weeks and 30 weeks should have a single "spot examination" at approximately 37 weeks of PMA (or prior to discharge from hospital) to include possible outliers. For infants with a birth weight of 1250 g (2.75 lbs.) or less, initial screening examination should be at 31 weeks of PMA or four weeks of CA, whichever is later; in the presence of any active ROP, the infant should be followed every one to two weeks; and Stage 3 should be followed at least every seven days.

SOURCE: Ells A, Hicks M, Fielden M, Ingram A. Severe retinopathy of prematurity: longitudinal observation of disease and screening implications. Eye 2005;19(2):138-44.
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Computerized Corneal Topography in a Pediatric Population with Down Syndrome

Canada’s Hospital for Sick Children (Toronto) conducted a prospective, non-randomized clinical trial of 21 children with Down syndrome and their parents to characterize abnormal corneal topographic changes using corneal computerized videokeratography (CVK).

The children with Down syndrome (mean age 6.9 years) were recruited from the Hospital for Sick Children; the study also included 18 of their parents and a pediatric control group of 60 otherwise well children (mean age 9 years). All underwent complete ocular examination and CVK using the EyeSys system. Corneal topographic maps were assessed subjectively, and investigators analyzed three objective parameters: central corneal power (CP), difference in central corneal power between the two eyes (DCP) and inferior-superior steepening asymmetry (I-S).

Corneal curvature in children with Down syndrome was significantly steeper than in the pediatric control population (CP 46.66 vs. 42.60 D), but changes with age paralleled that of the control population. DCP and I-S values were also significantly different from the control population. Thirty-nine percent of the parents of children with Down syndrome had at least one abnormal parameter.

The authors believe that the study results show CVK as a useful tool in the ocular assessment of patients with Down syndrome. The findings suggest that this patient population has abnormalities of corneal shape even in the absence of clinical evidence of keratoconus. A greater than expected incidence of abnormal topographic changes was observed in the parents of these patients.

SOURCE: Vincent AL, Weiser BA, Cupryn M, et al. Computerized corneal topography in a paediatric population with Down syndrome. Clin Experiment Ophthalmol 2005;33(1):47-52.
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Results of Excimer Laser Photorefractive Surgery After Three Epithelial Removal Techniques

Investigators at the Institute of Vision Research in Seoul, Korea, evaluated epithelial healing, postoperative pain and visual and refractive outcomes after photorefractive keratectomy (PRK) using three epithelial removal techniques, in a prospective, nonrandomized, comparative trial.

For the PRK procedure, the corneal epithelium was removed in one of three ways: mechanically (conventional PRK [PRK]) in 88 eyes of 44 patients; using excimer laser (transepithelial PRK [tPRK]) in 106 eyes of 53 patients; or using 20 percent diluted alcohol, laser-assisted subepithelial keratomileusis (LASEK) in 106 eyes of 53 patients. Main outcome measures included epithelial healing, postoperative pain, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA) and remaining refractive error.

The mean postoperative pain scores were 4.84 +/- 1.45 for PRK, 4.71 +/- 1.62 for tPRK and 4.63 +/- 1.52 for LASEK. Mean epithelial healing rates were 12.3 +/- 4.6 for PRK, 15.2 +/- 4.9 for tPRK and 18.1 +/- 5.2 mm2/day for LASEK. The postoperative six-month remaining mean spherical equivalents (diopters) were -0.46 +/- 1.01 for PRK, 0.18 +/- 0.91 for tPRK and -0.82 +/- 1.18 for LASEK. The LASEK group showed less favorable UCVA than other groups. No significant difference in BSCVA was evident between the groups. A faster epithelial healing rate did not result in better visual or refractive outcomes. Using the same nomogram, tPRK resulted in a slight overcorrection, and LASEK resulted in a slight undercorrection.

SOURCE: Lee HK, Lee KS, Kim JK, et al. Epithelial healing and clinical outcomes in excimer laser photorefractive surgery following three epithelial removal techniques: mechanical, alcohol, and excimer laser. Am J Ophthalmol 2005;139(1):56-63.
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Scanning Laser Tomography of Full-thickness Idiopathic Macular Holes

A British study using the Heidelberg retina tomograph to acquire a three-dimensional tomographic image of the macula in patients with full-thickness macular holes suggests that antero-posterior traction forces are the primary cause of the holes. The study also suggests that these forces persist in Stages 3 and 4 macular holes, while tangential forces serve to enlarge the hole at this later stage.

The study included 21 consecutive patients with full-thickness macular hole. Investigators acquired tomographic images of the macula in each eye of each patient. The surface profile showed an elevated rim around the 24 macular holes imaged, with a gently sloping outside edge and a steeply sloping inside edge. In addition, they observed a ring of elevated tissue around the edge of the hole in all the holes and also in two of the fellow "normal" eyes. They presumed that this ring of elevated tissue represented a ring of persistent vitreo-retinal traction around the fovea in the presence of a perifoveal posterior vitreous detachment. This is consistent with antero-posterior traction persisting in Stages 3 and 4 full-thickness macular holes. The mean ring diameter was 480 µm when present in the fellow eye but was 950 µm in the presence of a macular hole. The investigators believe this suggests centrifugal displacement of retinal tissue on the formation of a Stage 3 macular hole and provides evidence for tangential traction.

SOURCE: Bishop F, Walters G, Geall M, Woon H. Scanning laser tomography of full thickness idiopathic macular holes. Eye 2005;19(2):123-8.
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BRIEFLY
  • NOVARTIS LICENSES INVESTIGATIONAL DRY EYE TREATMENT. Novartis has in-licensed rebamipide, an investigational treatment for dry eye, from Japan-based Otsuka Pharmaceutical Company, Ltd. Rebamipide is currently being tested in two Phase III studies in the United States and is expected to demonstrate a novel mechanism of action to enhance tear secretion and increase the levels of mucin covering the conjunctiva and cornea. Under the agreement, Novartis will obtain an exclusive license with the right to sub-license the compound globally, excluding Japan and selected Asian countries. Novartis will pay an upfront fee and annual royalties. The terms of the agreement were not disclosed.
  • PEDIAMED AND ALLERGAN FORM CO-PROMOTION AGREEMENT FOR ZYMAR. PediaMed Pharmaceuticals, a company that identifies, develops and markets branded prescription pharmaceuticals for children, has entered into a co-promotion agreement with Allergan, Inc. in the United States pediatric market for Allergan"s Zymar ophthalmic solution, a treatment for bacterial conjunctivitis. The agreement marks the second transaction between Allergan and PediaMed in the last year; in August 2004, Allergan and PediaMed agreed to co-promote Allergan"s Tazorac product in the United States. PediaMed will be responsible for Zymar commercialization in the United States pediatric market, with Allergan continuing to promote to ophthalmologists, optometrists and other eyecare professionals. For more information, go to www.pediamedpharma.com.
  • ALIMERA AND CONTROL DELIVERY SYSTEMS COLLABORATE ON PHARMACOLOGIC TREATMENT FOR DME. Alimera Sciences Inc., and Control Delivery Systems, Inc. (CDS) have forged a worldwide agreement to co-develop and market a new pharmacologic treatment for treatment of diabetic macular edema (DME), a major cause of vision loss in people suffering from diabetic retinopathy. Alimera Sciences also has the option to develop three additional products using CDS" drug delivery technology. The companies are in discussions with the FDA to initiate clinical trials to determine the effectiveness of injecting an implantable form of CDS" technology into the vitreous of the eye to treat DME. The implant is small enough to be injected into the eye via a 25-gauge needle and is expected to provide delivery of drug to the back of the eye for up to three years. Currently, the only approved method of treating DME involves laser photocoagulation therapy, which can leave irreversible blind spots. Many systemic compounds will not produce a therapeutic effect in the back of the eye. The compounds being studied to treat DME must be injected repeatedly because of a lack of true long-term release characteristics. For more information, go to www.alimerasciences.com or www.controldelivery.com.

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