Blur adaptation: clinical and refractive considerations

The human visual system is amenable to a number of adaptive processes; one such process, or collection of processes, is the adaptation to blur. Blur adaptation can be observed as an improvement in vision under degraded conditions, and these changes occur relatively rapidly following exposure to blur. The potential important future directions of this research area and the clinical implications of blur adaptation are discussed.     

Computerized tomographic analysis of orbital hypertelorism repair: spatial relationship of the globe and the bony orbit

Computerized tomographic scans provide a new means of evaluating the spatial and geometric relationships between the movement of the bony orbit and its soft tissue contents (the globe and extraocular muscles) [1, 12]. Preoperative and postoperative computerized tomographic scans were analyzed in four patients to explore these relationships. Measurement of the changes in distance between the globes correlated most closely with the change in the distance between the lateral orbital walls; resection of medial (inter-orbital) bone provides space into which the globe is translocated. The medial rectus muscle may be bowed across the medial wall osteotomy line, creating a functional shortening of the muscle; this finding may explain the esotropia that is commonly seen after this procedure [2, 3]. These observations should have a direct impact on the understanding and planning of orbital hypertelorism correction.     

Serum ionic fluoride levels in haemodialysis and continuous ambulatory peritoneal dialysis patients

High serum fluoride (F-) in patients with chronic renal failure (CRF) and end-stage renal disease (ESRD) is associated with risk of renal osteodystrophy and other bone changes. This study was done to determine F- in normal healthy controls and patients with ESRD on haemodialysis (HD) or peritoneal dialysis (PD). Seventeen healthy controls (12 males, 5 females) and 39 ESRD patients on dialysis (17 males, 22 females) were recruited in the study in a community with 47.4 +/- 3.28 microM/l (range 44-51 microM/l) of F- content in drinking water. Control subjects showed a mean serum F- concentration of 1.08 +/- 0.350 microM/l. Males in control group showed slightly higher F- levels (1.15 +/- 0.334, range 0.55-1.9 microM/l) than females (0.92 +/- 0.370, range 0.6-1.5 microM/l). Mean serum F- concentration did not correlate significantly with age and sex among control subjects, whereas such correlation was observed in patients with ESRD on dialysis. Mean serum F- concentration was significantly higher in patients on dialysis (2.67 +/- 1.09, range 0.8-5.2 microM/l) than normal controls. When grouped according to sex, the mean serum F- concentration in males (3.05 +/- 1.04, range 1.8-5.2 microM/l) was significantly higher than females (2.38 +/- 1.08, range 0.8-5.2 microM/l). When patients were grouped according to age, it was observed that F- concentration was significantly higher in patients with age groups 21-70 (2.86 +/- 1.05) than those with age group 13-20 years (1.42 +/- 0.531). Thus F- concentration correlated with age and sex, being higher in males and above 20 years. Despite appreciable clearance of F- (39-90%) across the peritoneum, patients on CAPD showed higher serum F- concentration than those on HD (3.1 +/- 1.97 vs 2.5 +/- 1.137 microM/l). Of the total 39 patients on dialysis 39% had their serum F- concentration above 3.0 microM/l, posing the risk of renal osteodystrophy.      

The timing of surgical intervention in craniofacial anomalies

When treating an infant or younger child with severe craniofacial synostosis, the burden is placed on the surgeon in making a decision regarding not only the design of the osteomy but also the timing of the surgical intervention. This article reviews the current treatment protocols for craniofacial anomalies.     

Radiographical documentation of direct injury of the intracanalicular segment of the optic nerve in the orbital apex syndrome

In the radiographical evaluation of the orbital apex syndrome, standard radiographs, tomograms, and computed tomographic scans have proved useful in the demonstration of the bony pathology, especially for optic canal fractures. The limitation of these methods, however, remains in their inability to provide accurate delineation of the associated soft tissue pathology, including the presence of optic nerve sheath hematoma. Recent developments in computer technology and graphic imaging are now available to provide an accurate three-dimensional radiographical analysis of the extent of skeletal and soft tissue injury in the orbital apex syndrome. The physician, in essence, can perform a radiographical "living autopsy". The technique was used to evaluate a patient with bilateral apex syndrome. It clearly showed that a severe direct injury to the intracanalicular portion of the optic nerve was responsible for the development of blindness in this patient. The progression of optic nerve injury, from perineural sheath hematoma to the ultimate development of optic nerve atrophy and fibrosis, was radiographically documented.