Congenital nystagmus (CN) is a disorder of the ocular motility characterized by oscillatory eye movements preventing the correct fixation of a target. Many typical waveforms of eye position recordings have been recognized and classified in the literature: in jerk CN a slow phase eye movement is followed by a fast phase, giving rise to a typical saw-tooth waveform, while in pendular CN the eyes exhibit a periodic motion, giving rise to an approximately sinusoidal waveform. Dual jerk waveforms seemed to show small, rapid oscillations superimposed on a jerk-like wave-form, thus being originally classified as a mixture of jerk and pendular CN. On the contrary, a theoretical model of CN has appeared recently, which suggests a possible interpretation of the small amplitude oscillations in dual jerk waveforms as consecutive pieces of growing and decaying exponentials. By spectral analysis of dual jerk waveforms in a number of patients with CN, we show that the oscillations are truly sinusoidal in nature, thus suggesting the possibility of a different explanation of dual jerk waveforms in CN.

We measured the frequency distribution of the time interval between quick phases of nystagmic eye movements in 8 patients with congenital nystagmus. For each patient we recorded a 3- to 4-second long electro-oculographic (EOG) signal, repeating each session 22 times. The period of the nystagmic cycles was computed for each record, by evaluating the peak frequency of the nystagmic oscillations via spectral analysis of the EOGs. This period is a measure of the time interval between quick phases. Its distribution ranged between 100 and 600 ms and peaked at about 240 ± 50 ms, with a gaussian shape for values less than about 300 ms. Our measurements were considered as providing the distribution of intersaccadic latencies in normal humans.

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912 patients affected by microfollicular conjunctivitis were submitted to a scraping conjunctival cytology before taking specimens for direct immunofluorescence. 264 patients proved to be positive to the direct immunofluorescence test for Chlamydia trachomatis (CT). In all cases the infection turned out to be bilateral with different degrees of positivity between one eye and the other. In 43 patients out of the 264 positive ones, the cytological examination showed the presence of eosinophils in both eyes. The presence of eosinophils poses the problem of a certain allergizing power of Chlamydia and of the possibility that the CT infection might easily develop in subjects with a preexistent allergic conjunctivitis.

We analyzed quantitatively electronystagmographic recordings of pendular waveforms via spectral analysis methods. We found (1) symmetrical pendular oscillations in orbital positions spanning a range as wide as 40°, with frequencies between 2 and 8 Hz; (2) stable and small pendular oscillations in patients without a null zone and unstable and large pendular oscillations in patients with a neutral zone; (3) a non-decreasing relationship between the amplitude and the frequency of the eye oscillations, and (4) pendular components in orbital positions at the two sides of a neutral zone. It is argued that pendular nystagmus can be generated independently of normal (jerk) nystagmus in the same orbital position.