Electroretinographic Studies in the Experimental Retinal Degeneration

In order to investigate the changes in the scotopic and photopic ERG induced by the acJrninistrations of retino-toxic agents, 30mg/kg of body weight of sodium iodate and sodium iodoacetate were given in albino rabbits intravenously. Animals were anesthetized with intra venous urethane injection (1.5g/kg) and the pupils were dilated with atropine. The eye was stimulated with a single light flash (800 lux at the animals eye) of 200 msec duration. Prior to the recording of the scotopic ERG, animals were preadapted to light of 150 lux for 30 minutes. During dark adaptation, b-potential increased rapidly for the first 6-8 minutes followed by slow augmentation in normal eye. On the cessation of dark adaptation, b-potential dropped immediately, its decrease amounting up to 80% of the maximal potential attained during dark adaptation. By the administration of sodium iodate, c-wave disappeared immediately accompanied by apparent increase in the slow cornea-negative potential. No changes were noted in the b-potential during the first hour after iodate. Slow recovery phase during dark adaptation disappeared. Thereafter, b-potential diminished progressively with deepening of the slow negative wave. In some cases, b-wave almost extinguished 3 hours after iodate, and in another cases, some recovery of the b-wave was noted 48 hours after iodate administration. Iodoacetate produced immediate fall of b-potential with slow decrease of negative potential which progressed to the complete disappearance of the whole ERG responses. In some cases, b-wave reappeared 5 hours after iodoacetate, with prolongation of its duration. At 24-48 hours after the administration, no electrical response to light stimulus was elicited. From the obtained ERG findings, it can be deduced that the functions of the pigment epithelium could be disturbed secondary to the degenerations of visual cells. No correlation could be demonstrated between the ERG changes and the EOG changes after administration the toxic agents. Histological examinations of eyes at various intervals after administrations of retinotoxic agents revealed the degenerations of the pigment epithelium, sensory organelles of the visual cells and inflammatory changes in the choroid by iodate; and destruction of visual cells with preservations of the pigment epithelium by iodoacetate.

Comparative Studies of the Effects of Dfamox and Neptazane on the Intra-Ocular Pressure

The purpose of this paper is to collect the comparative data regarding the actions of Diamox and Neptazane in short-term and long-term administrations. This investigations were divided into three parts. (1) a single dose response in normal and glaucomatous eyes, (2) actions on aqueous flow and (3) long-term treatments in glaucomatous eyes. (I) A single dose response. Ten eyes from 10 normal subjects, ages ranging from 24 to 57 years, were chosen. They were given 500mg of Diamox or 100mg of Neptazane alternately and intra-ocular pressure was determined at regular intervals. In another series, 18 eyes from 18 glaucomatous patients were investigated in the same manner. The patients comprise 13 cases of chronic simple glaucoma and 5 cases of chronic narrow-angle glaucoma. No considerations were given as to their sex and age differences. Prior to administration of the drugs, the diurnal variations of intraocular pressure in each eye had been recorded during the daytime. The intra-ocular pressure was measured by Goldmann's applanation tonometer. (II) Actions on aqueous flow. Actions of Diamox (500mg) and Neptazane (100)mg on the aqueous flow were studied by the perilimbal suction cup method of Rosengren and Ericson in 8 normal eyes. The suction cup was applied 3 hours after Diamox and 6 hours after Neptazane administration. (III) Long-term treatments. Fifteen glaucomatous patients, 10 chronic simple glaucoma and 5 chronic narrow-angle glaucoma, were investigated. Their ages were from 43 to 61 years. The schedules of dosage were 250mg of Diamox, t.i.d. or 50mg of Neptazane, t.i.d. and followed up to 35 days. In some cases, treatment was discontinued or the doses were reduced to 250mg of Diamox, b.i.d. and 50mg of Neptazane, b.i.d., due to the side reactions. Results: (I) Results of measurements of intra-ocular pressure in normal eyes were shown in Table 1 and 2. (a) Diamox: The ocular tension begins to fall as early as 30 minutes, and maximal lowering occurred between 1~4 hours (average, 2.3 hours). Thereafter, tensions rose again and returned to the original level within 24 hours in all cases except in 2 cases. The maximal reduction was on the average 3.7mmHg. Side reactions were observed in 3 cases. (b) Neptazane: The tention begins to fall 0.5~1 hour and the maximal fan was obsered between 4~8 hours (average, 6.4 hours). The maximal degree of fall was 3.3 mmHg. The ocular pressure was still low after 24 hours in all cases except in 3 cases. No side reaction was encountered. (B) In glaucomatous eyes: Results were summarized in Table 3 and 4. (a) Diamox: Ocular tension begins to fall: 30 minutes and maximal fall was attained at 2.2 hours. The degree of maximal reduction was 13.7 mmHg. The lowered tension returned to the initial level within 24 hours in most cases. Side reactions were observed in 5 cases. (b) Neptazane: Ocular tension begins to fall 0.5~1 hour and maximum lowering was observed after 6 hours. The extent of maximal fall was 12.3 mmHg. The ocular tension was still low after 24 hours in most cases Side reactions were encountered in 3 cases. (II) Perilimbal suction cup studies revealed that both Diamox and Neptazane reduced the aqueous flow considerably as shown in table 5. (III) Results of long-term treatments were tabulated in table 6 and 7. (a) Diamox: The maximal degreess of fall in ocular tension were observed relatively early in the treatment and thereafter the tension fluctuates irregularly and showed tendencies to gradual rises. Sid effects were observed in 10 cases. Complete normalization of ocular tension, e.g., under 21 mmHg, was achieved in 8 cases. (b) Neptazane: The same tendency was observed in this group. Side reactions were encountered in 6 cases and milder than in Diamox treated group. As these results show, both Diamox and Neptazane showed a significant tension lowering effect. Neptazane is five times more powerful than Diamox in equal dosage basis. The ocular pressure falls more slowly and its duration was longer in Neptazane treated eyes. Sid reactions were observed more frequently in Diamox group and somewhat severe.

The Determination of the Rate of Aqueous Flow by the PeriIimbal Suction Cup

The perilimbal suction cup was utilized to measure the rate of aqueous flow according to the Ericson's method. Suction pressure of 50 mmHg for 15 minutes was applied and the rate of aqueous flow was calcula ted from the resultant increase of intraocular pressure, using the Friedenwald's table. Twenty eyes from 20 healthy normal individuals were investigated. The average rate of flow was found to be 0.66 cu.mm/min., ranging from 0.45 to 0.86 cu.mm./min. The increased intra-ocular pressure induced by the suction cup returned to original normal level within 15 minutes after the removal of the suction cup. This estimate of the rate of aqueous flow is less than that obtained by tonography, fluorescein and perfusion studies. The fatcors responsible for this low value, e.g., decreased aqueous formation due to elevated intraocular pressure, leakage of aqueous, etc., were discussed.

The Effect of Alpha-chymotrypsin, Trypsin and Hyaluronidase on the Viscosity of the Rabbit's Vitreous Humor

Alpha-chymotrypsin, trypsin and hyaluronidase were added to the rabbit's vitreous humor which was filtered through the glass filter. The viscosity was measured by Ostwald type viscosimeter with O.5mm capillary bore size. The relative viscosity of normal vitreons humor was 1.085. The relative viscosities of vitreous humor, to which 1mg and 2mg of alpha-chymotrypsin and 100 H.U.M. and 200 H.U.M. of trypsin were added, showed no significant changes. On the other hand, the vitreous humor which had been treated by 100 T.R.U. of hyaluronidase showed a marked reduction in the viscosity. The viscosity of normal vitreous humor, which had been preserved at 20 degrees for 3 hours, was significantly reduced.