The impact of ocular blood flow in glaucoma.

Retinopathy of prematurity

The Cox regression model has been used extensively to analyze survival data. For data that consist of large numbers of small groups of correlated failure time observations, we show that the standard maximum partial likelihood estimate of the regression coefficient in the Cox model is still consistent and asymptotically normal. However, the corresponding standard variance-covariance estimate may no longer be valid due to the dependence among members in the groups. In this article, a correct variance-covariance estimate that takes account of the intra-group correlation is proposed. Power comparisons are performed to show the advantage of the new proposal. Examples are provided for illustration.

Cox-Type Regression Analysis for Large Numbers of Small Groups of Correlated Failure Time Observations

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)60198-6.pdf

The eye in hypertension.

We reviewed research on retinal oxygen (O2) distribution and use, focusing on O2 microelectrode studies in animals with circulatory patterns similar to those of humans. The inner and outer halves of the retina are different domains in terms of O2. Understanding their properties can suggest mechanisms of and therapies for retinal diseases. Inner retinal PO2 averages about 20 mm Hg. Effective O2 autoregulation of the retinal circulation ensures that inner retinal PO2 is relatively uninfluenced by systemic hypoxia and hyperoxia and increased intraocular pressure in healthy animals. Failures of the retinal circulation lead to tissue hypoxia that underlies the vasoproliferation in diabetic retinopathy and retinopathy of prematurity. Choroidal blood flow is not regulated metabolically, so systemic hypoxia and elevated intraocular pressure lead to decreases in choroidal PO2 and photoreceptor O2 consumption. The same lack of regulation allows choroidal PO2 to increase dramatically during hyperoxia, offering the potential for O2 to be used therapeutically in retinal vascular occlusive diseases and retinal detachment.

/pdf/retinal-oxygen-fundamental-and-clinical-aspects-k1txi4b80h.pdf

Retinal Oxygen: Fundamental and Clinical Aspects

High prevalence of glaucoma in patients with sleep apnea syndrome

Introduction: In normal-tension glaucoma, optic nerve damage occurs without elevated intraocular pressures, hence vascular and pathogenic mechanisms other than intraocular pressure

Normal-tension glaucoma is associated with sleep apnea syndrome.

Background and Purpose —Occlusion of the central retinal artery (CRAO) causes a sudden decrease of monocular vision. Because early restoration of blood flow may improve outcome, we attempted to treat CRAO with selective intra-arterial fibrinolysis.

Methods —Intra-arterial fibrinolysis was performed within 6 hours after symptom onset in 17 patients with thromboembolic CRAO. Symptoms were painless, acute and severe decrease of vision. Urokinase (100 000 to 900 000 IU) was given through a microcatheter into the ophthalmic artery over 10 to 90 minutes. For comparison, the history and visual outcome of 15 control patients who did not receive fibrinolytics were evaluated. In both groups some of the patients underwent paracentesis and/or received carboanhydrase inhibitors.

Results —Patients who underwent fibrinolysis fared better than control patients ( P =0.01). Three patients (17.6%) recovered completely after fibrinolysis and regained visual acuity of 20/20 (n=2) to 25/20 (n=1). Two additional patients (11.8%) showed a marked improvement to a visual acuity of 20/30. In 6 patients (35.3%) vision improved slightly. They were able to count fingers, detect hand movements, or perceive light. In 6 patients (35.3%), fibrinolytic treatment was without effect. Among control patients, 1 patient (6.7%) showed partial, 4 patients (26.7%) minimal, and 10 (66.7%) no improvement of vision.

Conclusions —A complete or marked improvement of visual acuity was achieved in one third of intra-arterial fibrinolysis patients but in none of the control patients. Intra-arterial fibrinolysis seems to have the potential to “lighten” the spontaneously poor outcome of CRAO.

Selective Intra-Arterial Fibrinolysis of Acute Central Retinal Artery Occlusion

Optic neuropathy associated with sleep apnea syndrome

Preliminary results of a controlled study on diabetic retinopathy are reported. Two hundred and fifteen patients with proliferative (PDR) and nonproliferative (NPDR) retinopathy were uniocularly treated by Xenon photocoagulation and followed for a minimum of 6 months–6 years. Intra- and epiretinal new vessel formations (RNF) decreased in treated but increased in untreated eyes at a high statistical significance. A transition of background retinopathy into the proliferative stage was significantly retarded after photocoagulation. An improvement of new vessel formations on the disc (DNF) was not evident after 3 years of follow-up. The progression of preretinal neovascularization (PRNF) was significantly reduced only for 1–2 years after treatment. The incidence of massive vitreous hemorrhages, however, which showed the highest quotient of contingency with PRNF was much lower in treated eyes also after 3 years. The difference was significant only in extensively photocoagulated eyes with more than 100 lesions on average. The effect of photocoagulation on diabetic maculopathy with preservation of a useful visual acuity was highly significant only in diabetics under 60 years of age, the effect increasing with time as the control eyes fared worse. By contrast, in patients over 60 years of age, the course of maculopathy was not influenced, and a linear decrease of visual acuity occurred in both treated and untreated eyes.

Fritz Koerner

Papers

High prevalence of glaucoma in patients with sleep apnea syndrome

Normal-tension glaucoma is associated with sleep apnea syndrome.

Selective Intra-Arterial Fibrinolysis of Acute Central Retinal Artery Occlusion

Optic neuropathy associated with sleep apnea syndrome

Diabetic retinopathy study