Nobuhisa Nao-i

Resorption of subretinal fluid by transepithelial flow of the retinal pigment epithelium

The efficiency of flow through the retinal pigment epithelium (RPE) was calculated by studying the postoperative course of the subretinal fluid after nondrainage surgery of rhegmatogenous retinal detachment. In ten eyes of ten patients the preoperative volume of the subretinal fluid, area of the RPE participating in resorption of the fluid, elapsed time until resorption of the fluid, and efficiency of the flow were studied using B-scan ultrasonography. The flow through the RPE was 261 μl/cm2 per day and could drain more than 50% of the vitreous volume to the choroidal circulation. These data coincide well with early reattachment of neural retina in nondrainage surgery. No statistically significant difference in this flow was seen between young and old patients.

Toxic Effect of Fluorouracil on the Rabbit Retina

We conducted electrophysiologic tests of the toxic effects of fluorouracil on 26 albino rabbit eyes. Fluorouracil concentrations of 10 -7 g/ml, 10 -6 g/ml, and 10 -5 g/ml produced no significant changes in the b-wave amplitudes of the electroretinogram. A concentration of 10 -4 g/ml, however, reduced the b-wave amplitude to 62% ± 7.3% of the original value after 60 minutes. A concentration of 10 -3 g/ml decreased the value even further, to 41% ± 12% of the original value. At this concentration the a-wave appeared to be enhanced, probably because the ascending phase of the b-wave was delayed. A concentration of 5 x 10 -3 g/ml resulted in disappearance of the b-wave within approximately three minutes, but removal of the test solution and replacement with a fluorouracil-free medium produced recovery of the b-wave amplitude to 89% ± 9.9% of the original value within 55 minutes.

Outcome of white pump shunt surgery for neovascular glaucoma in Asians

We compared the effect of seton (White pump shunt) surgery (16 eyes) with that of trabeculectomy and 5-fluorouracil (31 eyes) in treating 38 Asian patients with medically uncontrollable neovascular glaucoma. We found the probability of long-term success (intraocular pressure < or = 26 > or = 5 mm Hg) of seton surgery (53.0% at 3 years) to be similar to that obtained following trabeculectomy with adjunctive 5-fluorouracil (45.4% at 3 years). However, 3 years postoperatively, the probability of the preservation of visual acuity was significantly greater following trabeculectomy than seton surgery (67.1% vs 23.1%; P < .05). In addition, the prevalence of postoperative complications was higher with the seton procedure (P < .001). The loss of endothelial cells 6 months postoperatively was more marked with seton surgery than with trabeculectomy, whether the shunt device touched the cornea (P < .000001) or not (P < .0005). In conclusion, Whites pump shunt was effective in lowering the IOP of eyes with neovascular glaucoma. However, care must be taken to prevent postoperative complications, the incidence of which exceeded those observed following trabeculectomy with adjunctive 5-fluorouracil.

New disposable ERG electrode made of anomalous polyvinyl alcohol gel

We developed a disposable electrode for the electroretinogram made of anomalous polyvinyl alcohol gel. This new hydrogel is a rubber-like elastic with water content 80–90 wt%, but insoluble in water. The elastic electrode plate is approximately 0.3–1.0mm thick, sterile, flexible, and easily cut to the desired shape. Its low cost permits it to be discarded after use.

Paradoxical enhancement of the ERG c-wave by a small dose of sodium iodate

Abstract The early effects of sodium iodate (NaIC3) on the ERG c‐ and b‐waves were studied in rabbits. When 30 rag NaIO3/kg body weight was administered intravenously, the c‐wave amplitude decreased and was replaced by a potential of opposite polarity. However, the administration of 20 mg/kg of NaIO3 enhanced the c‐wave remarkably. Twenty min after administration, the mean c‐wave amplitude significantly increased (P<0.001) to 211±6.2% of the pre‐administration amplitude, whereas that of the control was 108± 13.0%. The b‐wave amplitude showed no significant changes. When 10 mg/kg of NaIO3 was administered, the enhancement of the c‐wave was not remarkable. These effects were similar in both pigmented and albino rabbits. A lower blood concentration of NaIO3applied to the basal side of the retinal pigment epithelium (RPE) may initially affect only the basal membrane of the RPE resulting in the decrease in the basal membrane resistance (Rba). This would explain the transient increase in the c‐wave amplitude with 20 mg NaIO3/kg.

Effect of glucose added to intraocular irrigating solutions on the rabbit electroretinogram in vitro

The most adequate concentration of glucose in intraocular irrigating solution for the retina was studied electrophysiologically in the pigmented rabbit in vitro. Comparison of b-wave amplitudes demonstrated that glucose at a concentration of 20 m M/l yielded the highest values. A 40 mM/l glucose solution also increased the b-waves but to a lesser extent than did a solution of 20 mM/l. This result might be due to the detrimental effects of osmolarity. However, under hypoxic conditions the amplitudes of the b-wave obtained with 40 mM/l glucose solution was greater than those with 20 mM/l. It thus appears that slight hyperglycemic concentrations might have favorable effects on the ischemic retina.

Topographical distribution of electroretinographic potentials monitored by skin-electrodes

Electroretinographic recordings were made from 20 different skin points by skin-electrodes when the eye was fixed in a straight forward, lateral and nasal gaze. Three dimensional distributions of the percent amplitude of the b-wave were made using a microcomputer. The best recordings were obtained upon lateral gaze from skin points on the lower eye lid or near the lateral canthus. The skin-electrode ERG recording from these skin points upon lateral gaze may provide a useful diagnostic tool, especially in young children.

The normal c-wave amplitude in rabbits.

We examined some of the problems arising when c-waves are employed in pharmacological experiments with pigmented rabbits. The cyclic variations of the c-wave are smaller in rabbit than in other species. Under our experimental conditions the c-wave amplitudes in some rabbits reached an equilibrium under intermittent stimuli, while in others they increased with time and did not reach a constant level within 3 h. The c-wave amplitude varied with the standing potential during dark adaptation. However interindividual variations made it difficult to standardize the c-waves by this change. Since the c-wave amplitudes of the right and left eyes were similar, the contralateral eye should be used as a control when drugs are administered topically. Interindividual variations of the c-wave amplitude were smaller under dim light. This method is useful in chronic pharmacological experiments when drugs are administered systemically.

Some problems involved in employing the ERG c‐wave in pharmacological experiments: conditioning in pigmented rabbits

Abstract. The large inter‐ and intra‐individual variations in ERG c‐waves have prevented the application of the component in pharmacological experiments on the retinal pigment epithelial function. We examined some of the problems involved in employing the c‐wave in pharmacological experiments using rabbit retinas.