ABSTRACT
INTRODUCTION: Optic canal is a bony canal situated in between the roots of lesser wings of sphenoid, lateral to body of sphenoid. It transmits optic nerve and ophthalmic artery, surrounded by meninges. Various authors have studied variations in skull foramina and correlated clinically, as variants in the body structures have been found to be associated with many inherited or acquired diseases. AIM: The present study aimed to examine morphologic and morphometric variations in cranial openings of optic canals. MATERIALS AND METHODS: The study was undertaken in total 150 dry adult human skulls. The variations in size, shape, presence or absence and duplication or multiplication if any, in optic canal were observed bilaterally. Unusual features such as recess, fissure and notch were also observed bilaterally. Student's t-test was applied to compare size of cranial openings of optic canal on both sides. Similarly, morphologic features related with the canal were studied by calculating frequency and proportions of various parameters. RESULTS: Optic canal was present in all 150 skulls studied bilaterally. The mean maximum dimension of the canal at cranial opening was 5.03±0.72 mm on right side and 5.02±0.76 mm on left side. The shape of the canal was ovoid at cranial opening in all the skulls studied. Duplication of optic canal was present in one skull on left side. Recess was found in 105(35%) sides of total skulls observed. Fissure was found in 20(6.67%) sides and notch was observed in 30(10%) sides of total skulls. CONCLUSION: The optic canal showed variability in various parameters. Knowledge regarding variations in size, shape and unusual features on cranial opening of optic canal can be helpful to clinicians while approaching optic canal for various invasive procedures such as optic nerve decompression.
ABSTRACT
INTRODUCTION: The foramen Vesalius is located within bony plate between the foramen ovale and the foramen rotundum in the floor of middle cranial fossa. This foramen allows passage of emissary veins which communicate cavernous sinus and pterygoid plexus of veins. AIM: To study the morphological and morphometric variations of foramen Vesalius in dry adult human skulls. MATERIALS AND METHODS: One hundred and fifty dry adult human skulls were studied for variations in size, shape, presence/absence and any duplication/multiplication of the foramen Vesalius. After collecting data, appropriate statistical analysis was done. RESULTS: The mean maximum dimension of foramen Vesalius was 0.98±0.67 mm on right side and 1.12±0.73 mm on left side. Foramen Vesalius was present in 90 (60%) skulls out of 150 observed. The incidence was 41(27.33%) on right side and 49 (32.67%) on left side. Foramen Vesalius was present unilaterally in 32 (35.56%) and bilaterally in 29 (32.23%) out of 90 skulls. Duplication of this foramen was observed in two skulls (one right side and one on left side). Foramen Vesalius was round in 72%, oval in 24% and irregular in 4% of total foramina present. CONCLUSION: Foramen Vesalius was present in 60% of total skulls studied. The foramen showed variations in incidence and shapes, while there was no statistically significant difference in the maximum dimension between foramen Vesalius on right and left side. There could be some developmental reasons to explain these variations. The findings of this study could be important to anatomists and also equally essential for clinicians who approach middle cranial cavity for various procedures.
ABSTRACT
Retinitis pigmentosa (RP) and age-related macular degeneration (AMD) are incurable diseases that result in profound vision loss due to degeneration of the light sensing photoreceptors. However, the discovery that direct electrical stimulation of the retinal neurons creates visual sensation has inspired prosthetic devices aimed to restore useful vision in RP/AMD patients. The approach to one such electronic visual prosthesis is described in this article. The prosthesis consists of an external unit and an internal unit. The communication link has three components--power and data transfer from the external to the internal unit, and data transfer from the internal to the external unit. A novel method of integrating power transfer and back telemetry is described here. The goal is to design a stimulator chip with a small area with low power consumption. This chip, capable of stimulating 60 dedicated electrodes, is fabricated using AMI 1.2 microm process technology and the results are presented. Improvements in the design to increase the number of outputs to 1,000 have been discussed. The new circuit is aimed at increasing the circuit density, reducing power per stimulus, and meeting the requirements more closely than the previous designs. The results of the designed chip are presented.
