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| March 2008 | Inside IOVS | Volume 49/3 |
Continuous Positive Airway Pressure Raises Intraocular Pressure in Sleep Apnea Patients
An association between obstructive sleep apnea (OSA) and glaucoma has been reported. More and more physicians are confronted with the burden of OSA and its dramatic improvement with continuous positive airway pressure (CPAP) therapy. Kiekens et al (p. 934) show that the ophthalmologic effects of CPAP therapy include an increase of the average 24 hour intraocular pressure (IOP) as well as an increase of the 24 hour IOP fluctuations. The significantly higher nocturnal IOP rise is paralleled by a decrease in ocular perfusion pressure. Therefore IOP, optic discs, and visual fields warrant attention in the clinical work up of OSA patients. Particularly for those individuals who may be at risk for glaucoma, CPAP poses a potentially greater risk than has been generally considered.
Pseudomonas aeruginosa Keratitis - How Lowering Cholesterol Helps
Ulcerative keratitis due to P. aeruginosa is a serious sight-threatening disease requiring prompt intervention to reduce bacterial numbers and pathology. Zaidi et al. (p. 1000) found that P. aeruginosa enters corneal cells via cholesterol-rich lipid raft membrane microdomains. Disrupting these rafts by the cholesterol-extracting drug b-cyclodextrin reduced bacterial levels inside cells and in infected eyes as well as the pathologic consequences of infection. Bacterial entry also depended on having corneal cells expressing wild-type cystic fibrosis transmembrane conductance regulator (CFTR), which is the cellular receptor for P. aeruginosa. Bacteria and CFTR were visualized to localize in the cell membrane where lipid rafts formed.
Cataract Surgery and Age-related Maculopathy
In a retrospective study, Baatz et al. (p. 1079) found that patients with age-related maculopathy (ARM) who had cataract surgery did not develop significantly more neovascular macular degeneration than controls without cataract surgery. The study aimed to detect the immediate effects of surgery that may be caused by mechanical stress through surgical trauma or an angiogenic stimulus by postoperative inflammation. The results indicate that cataract surgery in patients with ARM is a safe procedure.
Effects of Dorzolamide on Retinal Oxygen Tension in Retinal Ischemia
Noergaard et al. (p. 1136) show that a carbonic anhydrase inhibitor, dorzolamide, increases the oxygen tension in ischemic retinal areas in pigs. The retinal ischemia was induced by experimental branch retinal vein occlusion (BRVO). The increasing effect of dorzolamide was demonstrated both 3-4 hours as well as 1 week after BRVO. The results indicate that medical treatment of retinal ischemia might be a future alternative.
Retinal Functional Abnormalities in Stargardt Disease Carriers
It remains an open question whether one can detect retinal functional impairment in genetically susceptible individuals, without apparent structural evidence of disease. Stargardt macular dystrophy (STGD), accounts for 7% of all retinal dystrophies and affects about 1 in 10,000 people, with a typical onset during childhood and a predominantly autosomal recessive inheritance. Maia-Lopes et al. (p. 1191) have found evidence for widespread retinal dysfunction in patients with Stargardt disease and morphologically unaffected carrier relatives. These results shed new light on subtle genotype-phenotype relationships that can only be identified at a functional level.
Analysis of Human Retinal Nerve Fiber Layer Thickness
Damage to the retinal nerve fiber layer (RNFL) is the fundamental lesion in glaucoma. So far, little human histological validation exists for imaging techniques routinely used in diagnosing and following glaucoma. Cohen et al. (p. 941) describe the largest series to date of healthy human RNFL tissue assessment. Their results portray and quantify the normal pattern of RNFL thickness in humans. These data corroborate imaging findings of RNFL thickness patterns obtained using commercially available RNFL imaging devices. Future work may help improve non-invasive imaging modalities that are aimed at detecting ophthalmic disease and may facilitate a more accurate diagnosis and treatment.
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