Research on Influences of Transient High IOP during LASIK on Retinal Functions and Ultrastructure.

Objectives. To study the influences of transient high intraocular pressure(IOP) during LASIK on retinal functions and ultrastructure. Methods. Thirty-two New Zealand white rabbits were randomly divided into normal control, experimental control, negative suction 20 s and negative suction 3 min groups. The experimental control group was treated only by laser. Rabbit eyes received suction for different periods of time (20 s, 3 min) by negative pressure generator in different groups. The changes of neuro-optic and retinal ultrastructure were observed under electron and light microscopes; retinal neurofunctional changes were observed with flash-visual evoked potential (F-VEP) and flash-electroreinogram (F-ERG). Results. There was no obvious change in optic nerve, retina, ERG a-wave and b-wave in normal control and experimental control groups. There were slight changes in tissues of optic nerve and retina at various times of suction 20 s compared with control group, and a sharp change in suction 3 min group within 14d after operation, but these changes recovered at 28d . Amplitude of ERG b-wave observed at different time will decrease with suction periods prolonged. It can recover to normal level with the prolonged recovery periods. Amplitude and incubation period of ERG a-wave and VEP-P did not change significantly after different duration of suction. Conclusions. The transient high IOP during LASIK might have influence on retinal function and ultrastructure, but these changes were reversible.

Voltage-dependence of miniature inhibitory postsynaptic current frequency and amplitude in tectal neurons of Xenopus.

Experiments were performed to study the voltage-dependence of miniature inhibitory postsynaptic current (mIPSC) frequency and amplitude using patch-clamp technique with whole cell recording in optic tectal slices of Xenopus. The following results have been observed. (1) When the membrane potentials of a neuron were depolarized or hyperpolarized stepwise from a resting potential via recording pipette to inject a DC current, the frequency and/or amplitude of mIPSCs increased or decreased respectively. The frequency of mIPSCs increased gradually with depolarizing membrane potential and it attained to the maximum as the membrane potential was held at +10 mV. (2) The amplitude increased slightly as the neuron was depolarized. When the depolarization of membrane potential reached -30 or -40 mV, the amplitudes of mIPSCs were maximal. Further depolarization resulted in a decrease of amplitude. Meanwhile, the large mIPSCs appeared when the membrane potential depolarized to a range between -20 mV and +10 mV. (3) With Ca(2+)-free bath solution, the frequency and amplitude of mIPSCs also increased stepwise progressively on depolarization of membrane potential, but the increase was less marked as corresponding value in normal saline perfusion. (4) When the [K(+)](o) in bath solution increased, the frequency of mIPSCs decreased markedly and the amplitude of mIPSCs decreased slightly. If the external K(+) concentration increased further to higher than 20 mmol/L, the neuron produced a marked slow inward or outward membrane current. The possible mechanism underlying the voltage-dependence of mIPSC frequency and amplitude is discussed briefly.

[Analysis of anthropometry on head and eye for stipulating of children's spectacle frames].

OBJECTIVE: To investigate the normal value of six parameters of head and eye in Chinese children, including interorbit distance (IOD), interpupillary distance (IPD), superior otobasion-ectocochion distance (obs-ec), intersuperior otobasion distance (obs-obs), exophthalmos and nasal basis angle, for stipulating the sizes of children spectacle frames. METHODS: The value of these six parameters in 10 171 children ages 5 to 17 years old were measured with caliper in four cities and the results were analyzed. RESULTS: The IOD, IPD, obs-ec and obs-obs were increased and positively correlated with the age. The differences of these parameters among different ages were statistically significant (F = 0.97, P < 0.01), especially in IPD before 15, IOD before 13, obs-ec and obs-obs before 12 and exophthalmos before 12 years old. The fastest growth age in IPD, IOD, exophthalmos, obs-ec and obs-obs was 10, 11, 5, 7 and 11 years old, respectively. The growth period of IPD, IOD, exophthalmos, obs-ec and obs-obs was 5 - 15, 5 - 13, 5 - 8, 5 - 12 and 5 - 15 years old. The difference of these six parameters among children in 4 cities were statistically significant (t = 3.1, P < 0.01). CONCLUSIONS: The most active growth period of IPD, IOD, obs-obs, obs-ec and exophthalmos lies between 5-15 years old in Chinese children 5-17 years old. Although the differences of these six parameters between male and female and among children in four cities are statistically significant, practically they are not important for stipulating the sizes of children's spectacle frames.