Preferential Suppression of the On Pathway by r-Aminobutyric Acid in the Catfish Retina

The effects of r-aminobutyric acid(GABA) agonsits and antagonists were explored by the intracellular recording method to discern the preferential suppression of the ON component by GABA on the ON-OFF transient cell in the catfish (Ictalurus punctatus) retina. Experiments were performed in the superfused eyecup preparation. The animals were decapitated and pited before the eye, and the surrounding tissue was removed from the skull. The retina was exposed by excising the cornea, iris, and vitreous. This preparation rested on a wad of Ringer`s soaked cotton in contact with an Ag/Agcl reference electrode. Solutions were delivered through a manifold system that was connected to a pipette located near the absorbent wick. Electro-physiological recordings were made using standard intracellular electrodes filled with 2 M potassium acetate. The electrical signal was recorded with an amplifierand a penwriter, viewed on an oscilloscope, and stored on a data recorder. The light sources were red light-emitting-diode (LED) and the stimuli were full field illumination covering the cntire retina. GABA preferentially reduced ON light responses in ON-OFF transient cell. and GABA hyperpolarized bipolar cells, but the effects on ON bipolar cells were more sensitive than OFF bipolar cells. CACA and TACA, GABAc receptor agonist, did not act on bipolar cells. CACA and TACA, GABAc receptor agonists, hyperpolarized bipolar cells but the sensitivity deferences between ON and OFF bipolar cell were not observed. These results suggest that the preferential suppression of the ON component of the ON-OFF transient cell by GABA was resulted from the presynaptic mechanism that reduced bipolar cell input.

The Risk Factors for Diabetic Retinopathy

It is very important to identify the risk factors in retinopathy because diabetic retinopathy is a major problem for the diabetic patients and it also represents the common cause of acquired blindness in adults. We reviewed 269 diabetic patients who visited the department of internal medical and were referred to the department of ophthalmology from January 1993 to December 1994. Clinical characteristics and the laboratory findings of patients with diabetic retinopathy such as age, sex, type of diabetes, duration of diabetes, systolic and diastolic blood pressure, total cholesterol, triglyceride, HbAlc, BUN, creatinine, protenuria were compared with those of normal retinal findings. Prevalence of diabetic retinopathy among 269 patients was 29.4% representing non-proliferative changes of 20.4% and proliferative changes of 9.4% respectively. No difference in prevalence of retinopathy was present according to the types of diabetes mellitus and sex(p>0.05). Longer duration of diabetes, higher systolic blood pressure contributed significantly to increasing the prevalence of diabetic retinopathy. No difference in prevalence of retinopathy was present according to the HbAlc, total cholesterol, triglyceride, creatinine but the levels of BUN and proteinuria wer significantly higher in group with diabetic retinopathy.

Statistical Analysis of Benign and Malignant Tumors in Eye, Ocular Adnexa and Orbit during the Past 7 Years

The 51 cases of eye tumors were evaluated histologically from May 1980 to August 1987 at Department of Ophthalmology, Catholic University Medical College, Kangnam St. Mary's Hospital. The results were as follows: 1. The ratio of male to female among 51 cases was 1:1.04 and histologically benign tumors 25 cases(49%), malignant tumor 26 cases(51%) respectively. 2. Histopathologic type of the most common benign tumor is dermoid cyst(9 cases, 36%), the next nevi(4 cases, 16%) and the third mixed tumor(3 cases, 12%). Among malignant tumor, retinoblastoma(17 cases, 65.5%) was most common and malignant melanoma(5 cases, 19.3%) follows next. 3. In case of benign tumor, there was almost no occurring differences in each age group but in malignant tumor, it showed the high incidence prior to 9 years of age and after 40 years of age. 4. The locations of tumor in benign tumor were conjunctiva, eyelid, lacrimal apparatus in erder. The most common location in malignant tumor was retina. 5. Looking at histopathologic findings of retinoblastoma, there were endophytic types(13 cases, 76.5%) and exophytic types(4 cases, 23.5%). There were 10 cases(52.5%) of optic nerve invasion and 3 cases among total 4 cases of exophytic types. And also, only one case of optic nerve invasion occurred in cases of rosette formation.

A Case of Reconstruction of Orbital Floor Fracture by Grafting Parietal Bone

An orbital floor fracture is caused by a sudden increase in the intraorbital pressure, resulting from the application of a traumatic force to the soft tissues of the orbit. The fracture is complicated by diplopia or enophthalmos. Orbital floor fractures are caused by the automobile accident, human fist or the ball. Our hospital performed reconstruction of an orbital floor fracture by grafting parietal bone on the fractured orbital floor area of the patient who visited our hospital 4 months after the hit on his left eye by a fist. We now report this case with the review of various aspects of an orbital floor fracture.