Scanning laser polarimetry in normal subjects and patients with myopia

AIMS—To examine the changes in the retinal nerve fibre layer (NFL) thickness with age and myopia in normal population.
METHODS—Retinal nerve fibre layer thickness was measured with a scanning laser polarimeter (NFA-I) in 180 normal subjects of varying age (range 7-83 years) and in 110 eyes of 85 patients with myopia of varying degrees (range −1.00 to −15.00D). They were all voluntary Anatolian people. Superior to nasal (S/N), inferior to nasal (I/N), and the superior to inferior (S/I) ratios were used for the assessment of retinal NFL thickness.
RESULTS—The mean superior NFL ratio was 2.96 and the mean inferior NFL ratio was 2.93 in normal subjects. There was a gradual decrease in NFL ratio with increasing age (simple regression analysis, p<0.05). The mean S/I ratio was 1.01 with a large variation. In patients with myopia, the mean superior NFL ratio was 2.60 and the mean inferior NFL ratio was 2.72. Superior and inferior NFL retardations, and S/I ratio in myopic patients were significantly (15.5%, 10.8%, and 4.9% respectively) lower than that of age matched normals (t test, p<0.05). There was also a gradual decrease in NFL thickness with increasing degree of myopia (simple regression analysis, p<0.05).
CONCLUSIONS—Nomograms we obtained for retinal NFL thickness may serve as reference points for the assessment of normal Anatolian people and myopic patients in future studies. NFL thicknesses gradually decreased with increasing age. Patients with myopia had significantly lower NFL thicknesses than normal subjects and, although weakened by wide age range of myopic group, there is a linear relation between severity of myopia and NFL thickness in myopic patients.


Acute corneal decompensation after silicone oil removal

Purpose: To assess acute corneal decompensation after silicone oil removal in some aphakic eyes with clear corneas whose anterior chambers were completely filled with silicone oil for a considerable period of time. Methods: Eight eyes of 8 patients who underwent vitrectomy and intraocular silicone oil injection were studied. All the eyes were aphakic and anterior chambers were completely filled with silicone oil. In all eyes, corneas were clear and no corneal finding indicating keratopathy was detected by slit-lamp microscopy before silicone oil removal. The mean silicone oil removal time was 4 months (range 2-7 months). A specular microscope was used for the evaluation of corneal endothelial changes and corneal pachometry was performed to observe corneal changes before and after the silicone oil removal in 5 eyes besides slit-lamp microscopy. The follow up period after silicone oil removal was 2-12 months (mean 6 months). Results: In all eyes severe corneal stromal edema and clouding was detected in the first day following silicone oil removal. Increased corneal thickness was seen in all eyes. Decreased (at or below critical levels) corneal cell density was detected by specular microscopy before and after silicone oil removal. No significant improvement was observed during the follow up period. Conclusion: Eyes whose anterior chambers completely filled with silicone oil could be evaluated as clear corneas by slit lamp microscopy despite severe endothelial damage. We recommend that eyes with silicone oil in the anterior chambers should be monitored by a combination of slit-lamp microscopic examination and specular microscopy to determine the relative corneal endothelial tolerance to the silicone oil and endothelial damage. Early removal of the silicone oil can be considered when the retinal adhesion allows

Spinal Cord Stimulation and Cerebral Hemodynamics: Updated Mechanism and Therapeutic Implications

The effects of spinal cord stimulation (SCS) on cerebral blood flow (CBF) are well known based on experimental investigations, and its vasodilator effect on peripheral arteries is widely used in clinical settings in the treatment of peripheral vascular disease. Since Hosobuchi's [Appl Neurophysiol 1985;48:372–376] first observations on the effects of SCS on CBF were published 22 years ago, many advances have been made in understanding SCS-mediated effects on CBF. This paper reviews the main laboratory observations and analyzes the most significant neurophysiological theories on the SCS-mediated effect on CBF. Most significant experimental data have been discussed, with specific reference to possible mechanisms such as 'functional reversible sympathectomy', cerebral infarction and related ischemic edema, hemodynamic deterioration in experimental combined ischemic-traumatic brain injury and cerebral vasospasm. The authors revised the published experiences in humans with hypoperfusion syndromes and 'adjuvant' locoregional CBF increase in chemotherapy of brain tumors. SCS represents a new perspective in challenging neurosurgical clinical fields such as cerebral ischemia and vasospasm, and seems promising as a new trend of functional neurosurgery in cerebrovascular diseases