The rat's visual field is represented on the cortex of each cerebral hemisphere within a primary visual area, visual field to the rat's right side upon the left hemisphere, and vice versa. The pattern of the representation has been determined electrophysiologically. The part of the visual field commanded by both eyes together, which is ahead of the animal, secures a larger representation upon the cortex in proportion to its size than the rest of the field, which is commanded by only one eye.There is evidence that a second smaller representation exists immediately lateral to the primary area.THE rat is a mammal with laterally directed eyes, widely used in laboratory studies involving visual discrimination. Where and how its visual field is projected upon the cerebral cortex was determined by Lashley [1934] who used anatomical methods to demonstrate the arrangement quadrant by quadrant. The present account describes an electrophysiological investigation of the same question. METHODSEighteen hooded rats weighing from 170 g. to 300 g. were used, and also some albino rats for comparison. The hooded rats were more satisfactory; their visual acuity, tested by their discrimination of gratings, is approximately two to four times better than that ofalbino rats [Lashley, 1930]; this difference occurs in part because the albino iris excludes light poorly. When the image on the back of the excised albino rat eye is photographed from behind the eye, the optimum exposure time varies less than 100 per cent when the pupil area is varied by a factor of 100, which suggests that a large amount of light is entering through the iris. It is impracticable to photograph the image on the back of the excised eye of a hooded rat, since the image is dispersed by the pigment present in the choroid.Anaesthesia was induced with ether and continued with a-chloralose (British Drug Houses), 140 mg./kg. given intraperitoneally. 160 mg. a-chloralose was dissolved in 20 ml. water at 100TC. and the required volume immediately cooled to 40TC. and injected. Further doses were given as required after about 5 hr. to maintain aniesthesia. In some preliminary experiments [Sefton and Swinburn, 1964], paraldehyde (1 ml./kg.) was injected intraperitoneally instead of chloralose. Satisfactory anaesthesia was obtained for 12-14 hr. with chloralose, and longer with paraldehyde.A polythene endotracheal cannula was inserted through an incision in the trachea and threaded up through the mouth and then down into the lower trachea; the neck incision could then be closed and a stable airway was available from mouth to trachea. Oxygen was administered by a fine tube within the cannula at about 3-5 ml./min., which exceeds the resting oxygen consumption of the rat [Simpson-Morgan, 1965].

Over a 12 month period, we used the anterior chamber maintainer (ACM) in cataract surgery in 258 patients; ages ranged from 15 to 95 years (mean 73 years). Surgery was performed using general or local anesthesia. The procedures were standard extracapsular cataract extraction (ECCE), mini-nuc ECCE, vectis extraction of the endonucleus, manual phacofragmentation, phacoemulsification, phacotrabeculectomy, repositioning the IOL, and anterior segment revision. We recorded our subjective assessment of the degree of anterior chamber (AC) maintenance and control of the position of the posterior capsule during surgery. We also kept clinical notes of the practical aspects of the procedures. The AC was well maintained in all patients throughout the surgery; posterior position of the posterior capsule was maintained during irrigation/aspiration. Five patients required the use of a viscoelastic agent at some stage. Our subjective assessment is that use of the ACM increased surgical control of the anterior chamber depth and position of the posterior capsule during surgery. Provided that it is used correctly, the ACM may offer increased safety during anterior segment surgery and require less use of viscoelastic agents.

Aims-To assess the eYcacy of extracapsular cataract surgery using the anterior chamber maintainer (ACM) without the use of viscoelastic. To compare the eVects of this surgical technique on non-diabetic and diabetic patients. Methods-A prospective single armed clinical trial of 46 eyes in 46 patients undergoing cataract surgery using the ACM without viscoelastic. Patients were assessed preoperatively and at 3 weeks, 3 months, and 12 months postoperatively. The main outcome variables included visual acuity, surgically induced astigmatic change (SIAC), changes in endothelial cell density (ECD), and morphology aVecting the central and superior regions of the cornea. Results-Postoperatively, 56% and 70% of patients had unaided visual acuities of 6/12 or better at 3 weeks and 3 months respectively. Even after excluding those patients with pre-existing maculopathy (including diabetic maculopathy), there remains a significant diVerence between the nondiabetic and diabetic groups in terms of the proportion of patients attaining an unaided visual acuity of 6/12 or better at both 3 weeks (p=0.003) and 3 months (p=0.001). Three months postoperatively, the SIAC based upon the keratometric and refractive data was 1.1 dioptres (D) and 1.3 D respectively. There was no statistically significant diVerence in the SIAC when the non-diabetic and diabetic groups were compared. The mean central and superior endothelial cell losses at 3 months postoperatively were 16% and 22% respectively and at 12 months postoperatively were 20% and 25% respectively. The diabetic group demonstrated greater endothelial cell losses and a more marked and protracted deviation of endothelial cell morphology from normality when compared with the non-diabetic group; however, the diVerences did not reach statistical significance. Conclusions-The eYcacy of small incision cataract surgery using the ACM in terms of visual outcome and induced astigmatism is comparable with the results obtained using other techniques that utilise a similar size of incision. However, in view of the magnitude and range of the endothelial cell losses associated with this technique the concurrent use of viscoelastic is suggested. There does not appear to be a statistically or clinically significant diVerence between non-diabetic and diabetic patients in terms of the magnitude of the endothelial cell losses or in the wound healing response in the 12 months after cataract surgery using the ACM. (Br J Ophthalmol 1999;83:71-75)

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Electro-oculography was performed on 120 normal subjects (240 eyes) between I0 and 69 years of age, with an even sex and age distribution. E. 0. G. ratio showed a significant sex difference (P < 0.01), with females having higher E. 0. G. ratios than males. There was a significant negative linear correlation between E. 0. G. ratio and age in females (P < 0.01), but none in males.Close correlation in E. 0. G. ratio was found between right and left eyes (P < 0.01), and 95 O/o of subjects showed a difference of 80 or less between right and left eyes. New normal limits of E. 0. G. ratio are proposed. These are 150 to 290for all males and for females of 50 or more years of age, and 170 to 342 for females below the age of 50 years.