Lower Nasal Quadrant Research Articles

Round and Oval Cones in Keratoconus

In advanced keratoconus, there are two cone types. The more common round or nipple shaped cone is limited in diameter but may reach any degree of conicity. The cone center lies mostly in the lower nasal quadrant. The oval or sagging cone, is often larger and lies more commonly in the inferotemporal quadrant close to the periphery. The oval cone is usually associated with more episodes of corneal hydrops, scarring and difficulty in fitting contact lenses. Histopathologic review of 23 cases (10 round, 13 oval), revealed that the oval group had more breaks in Bowman's membrane, 10.1 versus 5.0, (P < 0.01), and a tendency toward greater pannus formation with more ruptures in Descemet's membrane. We hope this clinicopathologic correlation may allow a more logical approach to patient care based on recognizing two different cone types in advanced keratoconus.

Die Darstellung des Kammerwasserabflusses normaler und glaukomkranker menschlicher Augen durch F�llung der Vorderkammer mit Fluorescein

After partially injecting the anterior chamber with a 0.2% fluorescein-Ringer solution we examined using a blue filter slitlamp normal eyes, eyes with open-angle glaucoma, and eyes following iridectomy, iridencleisis, Elliot's trephination, and trabeculectomy. In normal eyes at physiological intraocular pressure, 1--9 aqueous veins were found with a mean of 4.6. The distribution of these veins was usually irregular, being more numerous and of largest caliber in the lower nasal quadrant. With only a few exceptions the aqueous veins originated 1--2 1/2 mm peripheral from the limbus and joined the episcleral veins after a short course. The venae recipientes were characterized by a straight and deep course. In eyes with an open-angle glaucoma the average number of aqueous veins was found to be increased compared to the number found in healthy eyes. However, the caliber of these veins was smaller and distribution mor uniform. Eyes having undergone iridectomy do not differ from normal eyes in the mechanism of aqueous humor outflow. After iridencleisis and after trephination the transport of aqueous humor from the anterior chamber is achieved through a filtration bleb: (1) transconjunctival, (2) by bulk-flow through lymphatic vessels, (3) diffusely through lymphatic vessels or veins. In most cases the different transport mechanisms were combined and pure types were seldom found. There was a very definite relationship found between the size of the filtration bleb and the development of draining lymphatic vessels. After trabeculectomy the following drainage mechanisms of the aqueous humor were observed: 1. Subconjunctival outflow of aqueous humor. The further drainage in this case was achieved as in the old types of fistula building operations i.e., primarily through the lymphatic vessels. 2. Direct transport of aqueous humor into the surgical area through newly incorporated veins and lymphatic vessels. 3. Drainage of aqueous humor through still functioning aqueous veins.

Retinal detachments due to juxtapapillary microholes.

The characteristic features of an unusual apparently rare clinical entity represented by juxtapapillary retinal microholes, the accompanying retinal detachments, occurring mostly in high myopic eyes, are described in 6 cases. The genesis of these holes is related to the pull of a detached vitreous on retinovitreal adhesions in Martegiani's area. These tiny holes are closely adjacent to retinal blood vessels and situated predominantly in the lower nasal quadrant. The resulting retinal detachments are shallow, not undulating, mostly stationary or only slowly progressive, and with few exceptions involve the inferior nasal quadrant. Simple glaucoma was found in an unexpected high proportion.

Temperature gradients in the rabbit eye

Temperature measurements of the eyes of adult albino rabbits showed consistent gradients from the anterior surface of the retina to the outer surface of the cornea. Average difference between temperature at the retina and at the outer surface of the cornea was 5.01°C. Between rectal temperature and temperature at the outer surface of the cornea, average difference was 5.84°C. Temperature readings at points on the surfaces of ocular structures showed a consistent tendency to be highest in the lower nasal quadrant and lowest in the upper distal quadrant.