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| July 2006 | Inside IOVS | Volume 47/7 |
Older African Americans' Attitudes about Vision and Eye Care
Previous research has suggested that African Americans are less likely to receive routine eye care than are whites, which may be responsible for the higher vision impairment and eye disease rates in this population. Owsley et al. (p. 2797) assembled focus groups of older African Americans in Alabama to identify their perceptions about barriers to receiving eye care and their attitudes about vision and eye care. Separate groups were also assembled of the ophthalmologists and optometrists serving their communities. Transportation problems were by far the most commonly cited barrier by both older African Americans and their eye care providers. Whereas older African Americans had generally positive attitudes toward the importance of eye care, eye care providers tended to view older African Americans' knowledge basis and attitudes in a negative light, implying a serious communication gap between these two populations.
Anti-glaucoma Drugs and Ocular Perfusion Pressure
Quaranta et al. (p. 2917) performed a randomized clinical trial on the short-term effects of timolol, brimonidine, dorzolamide, and latanoprost on intraocular pressure (IOP), blood pressure (BP), and diastolic ocular perfusion pressure (DOPP). Each drug decreased significantly the IOP at all time-points. The mean 24-hour IOP after latanoprost administration was significantly lower than that after timolol, brimonidine, or dorzolamide administration. Brimonidine induced a significant decrease in the mean 24-hour DOPP value, while dorzolamide and latanoprost induced a significant increase. The study suggests that some pharmacologic therapies for POAG affect systemic BP, and, despite their favorable action in reducing the IOP, do not significantly increase DOPP. However, the importance of drug-induced changes in DOPP in determining optic nerve head damage requires further investigation.
Can Accommodation Be Restored in Presbyopic Eyes?
Accommodation can possibly be restored to presbyopic human eyes by refilling the capsular bag with a soft polymer. Previous studies of this surgical procedure in a primate eye model reported postoperative inflammation and early capsular opacification, making measurements of refractive changes difficult. Koopmans et al. (p. 2976) refilled the capsular bag in adolescent rhesus monkey eyes, while a specific intra- and postoperative treatment protocol was used to minimize postoperative inflammation and to delay capsular opacification. A certain level of accommodation could be restored after lens refilling. During the follow-up period of 37 weeks, refraction measurements were possible in all five monkeys that underwent the treatment aimed at the prevention of inflammation and capsular opacification.
MALDI Tissue Imaging of a-Crystallin
Han and Schey (p. 2990) used a new technique, MALDI tissue imaging, to observe protein profiles across equatorial sections of bovine lenses. aA- and aB-crystallins were imaged along with their truncated and phosphorylated forms. Extensive truncation was observed in the nuclear region for aA-crystallin, and rings of phosphorylated forms were observed in the inner cortical region for both crystallins. This new imaging method allows many protein forms to be observed in a spatially resolved manner in a single experiment. Thus, regional differences in lens proteins and their modified forms can be recorded.
Classifying the Proliferative Populations in Lens Epithelium
Zhou et al (p. 2997), using a long-term labeling and chase strategy, have shown that a hierarchal organization of proliferation exists in the adult mouse lens epithelium with the slowest or rarely cycling cells located in the central region and the more actively proliferating cells detected in the peripheral or germinative zone. The rarely cycling cells are proposed to be putative stem cells that divide very infrequently during homeostasis; however, upon perturbation, these cells enter the proliferative pool and provide progeny (transit amplifying cells) that will supply the central and germinative zones with cells capable of further division capacity.
Intrinsic and Extrinsic Factors Contribute to Photoreceptor Development
The mechanisms underlying the acquisition of a photoreceptor identity during development are still ill-defined. Garelli et al. (p. 3017) show here that photoreceptor precursors switch off the expression of Pax6, an early eye determinant, and start expressing Crx to initiate their differentiation. However, Crx expression alone is not sufficient to achieve fully differentiated photoreceptors, which require the action of docosahexaenoic acid (DHA) to move forward in their differentiation pathway. This suggests that both intrinsic and extrinsic signals are indispensable in photoreceptor development. These requirements should be considered when planning cell replacement therapies for retina degenerative diseases.
Apolipoproteins in RPE: A Role in Drusen Formation?
A hypothesis for a plausible pathway in the biogenesis of drusen, the lipid-rich extracellular lesions of aging and age-related maculopathy, is that the retinal pigment epithelium (RPE) assembles and basolaterally secretes a large lipoprotein particle containing apolipoproteins B and E (apoB, apoE). Li et al. (p. 3119) evaluated this hypothesis by examining retinal expression of apolipoproteins that appear on similar large particles secreted by hepatocytes and enterocytes. These investigators found evidence of apoA-II, C-I, and C-II immunoreactivity in drusen, either distributed diffusely throughout the druse or confined to an external shell, and evidence for the corresponding mRNA transcripts in native human RPE. An RPE-secreted lipoprotein may carry apoC-I and apoC-II, major modulators of lipoprotein lipase activity.
IL-6 Reduces Pressure-Induced Death of Retinal Ganglion Cells
Glia in the optic nerve and retina may serve as sources of cytokines that can alter the survival of retinal ganglion cells (RGCs) in glaucoma. Sappington et al. (p. 2932) examine how pressure modulates the release of interleukin-6 (IL-6) from retinal astrocytes and microglia and the effect of this release on RGC survival under pressure. They find that IL-6 in microglia media is sufficient to reduce pressure-induced RGC death, while pro-apoptotic factors in astrocyte media override the benefits of IL-6. These data provide insight into the complex signals between RGCs, retinal astrocytes, and microglia and identify IL-6 as a potential neuroprotectant in glaucoma.
Artificially Pigmented RPE Cell System Shows Promise for Laser Bioeffects
To reduce experimental animal usage, Denton et al. (p. 3065) have developed a simple in vitro retinal pigment epithelial (RPE) model system to study retinal laser bioeffects. The short, three-day procedure yielded cell monolayers of excellent viability while controlling the degree of pigmentation. At laser parameters representative of photothermal laser damage, an in vitro damage threshold (ED50) showed agreement to published data from an animal study. The authors provided examples of using the cell system for studying comparative laser bioeffects in the photochemical regime as well. With refinement in environmental control during laser exposure, the RPE model has potential for use in metabolic and computer simulation studies of laser-tissue interactions.
Flavonoids Protect RPE Cells from Oxidative Stress
Hanneken et al. (p. 3164) have identified a select group of flavonoids that protect RPE cells from oxidative stress-induced death with a high degree of potency and low toxicity. Many of these flavonoids also induce the expression of phase 2 detoxification genes, which function to provide additional protection against oxidative stress. This select group of flavonoids and the foods which contain high levels of these compounds may have some clinical benefit for patients with retinal diseases associated with oxidative stress, including macular degeneration and diabetic retinopathy.
Metipranolol Prevents Zinc-Induced Retinal Cell Death
Osborne and Wood (p. 3178) have shown that zinc causes apoptotic death of both photoreceptors and RPE cells via an oxidative mechanism. They have further demonstrated that the b-blocker metipranolol can counteract such cell death. The implications of this study are twofold. First, oxidative injury to both RPE cells and photoreceptors in situ may be caused by elevated levels of zinc and this may be relevant to diseases such as age-related macular degeneration (AMD). Second, metipranolol is already used in the clinic and may therefore provide a readily-available and efficacious agent for treatment of cell loss in AMD.
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