Malcolm L. Mazow

NGF prevents the changes induced by monocular deprivation during the critical period in rats

Photic evoked responses were recorded from the striate cortex of Long-Evans hooded intact, monocular visual deprivation (MD) and MD treated with NGF rats. The averaged visual evoked responses (AVER) were obtained from both hemispheres and provided comparison after binocular photic stimuli between the contralateral and the ipsilateral striate cortex with relation to the MD eye. One month of monocular visual deprivation at the critical period of development resulted in marked reduction of the amplitudes of AVER components as compared to the control recordings (P < 0.001). These changes of the AVER could be prevented by NGF infusion to lateral ventricle at the dosage of 2.0-2.4 micrograms/day for four weeks during the monocular deprivation. In conclusion, the change of AVER amplitudes induced by monocular visual deprivation during the critical period of development can be prevented by NGF infusion to lateral ventricle.

An Unusual Case of Ophthalmoplegic Migraine

A 33-year-old man complaining of headache and diplopia lasting one hour or less and occurring weekly was found to have ophthalmoplegic migraine. He was treated unsuccessfully with propranolol HCl, ergotamine tartrate, and methysergide maleate.

The Four-Step Test for Diagnosis of Paralytic and/or Restrictive Strabismus

By placing four diagnostic steps in a logical sequential manner, the diagnosis of a paralytic or restrictive deviation is made somewhat easier. Each time an incomitant strabismus is presented to an ophthalmologist, the four-step procedure should be used. Versions, ductions, and the cover test will reveal the eye to be investigated. Saccades, forced ductions, and/or forced generations will determine the problem and direct a surgical approach if needed.

Selection of patients and results of 25 years of topical anesthesia and adjustable suture surgery.

Background and Purpose The author has used adjustable suture techniques either in the operating room with topical anesthesia or at a later time after retrobulbar or general anesthesia for over 25 years. Careful selection of patients is essential to the success of this technique. It is the purpose of this paper to report the selection criteria used and to compare the results of the two methods utilized. Patients and Methods One hundred eighty-three patients were included in this study: 123 were operated upon with topical anesthesia. For comparison, sixty patients were included who had adjustment later in the day or the next day after having retrobulbar or general anesthesia. Both horizontal and vertical strabismus cases were included. Results Adjustable techniques done in the operating room or at a later time have both shown significant improvement in the strabismus angle following one operation in 86% of the cases. Diplopia was eliminated in 63% of patients with this complaint. (63% and 64.5% in the two groups, respectively). Seventeen of 123 patients having topical anesthesia (13.8%) required a second operation, and 8 of 60 (13.3%) of those having a later adjustment needed further surgery. Conclusion Careful selection of patients undergoing strabismus surgery allows successful topical muscle adjustment in the operating room with results similar to adjustments done following retrobulbar or general anesthesia at a later time.

Monocular visual deprivation at the critical period modulates photic evoked responses

Photic evoked responses were recorded from the striate cortex of Long-Evans hooded normal (control) rats and from monocular visual deprivation (MD) rats. The averaged visual evoked responses (AVER) were obtained from both hemispheres and provide comparison between the contralateral and the ipsilateral striate cortex with relation to the monocular deprived eye. The AVER recorded following binocular photic stimulation after 1 month of monocular deprivation demonstrated that the two visual cortexes responded differently. In the contralateral hemisphere of the visual cortex (related to the MD eye), all three components (P2, N2 and P3) of the AVER of the MD rats had significant increases in their peak amplitude as compared to the control recordings. In the ipsilateral cortex, the amplitude of component P2 and N2 was significantly reduced as a result of 1 month of MD. Comparing the AVER amplitudes of the two homotopic sites of the visual cortex obtained from the control group reveals no differences between the two hemispheres but markedly significant differences in P2, N2 and P3 components for the MD group. Based on the literature, the possibility that the monocular visual deprivation at the critical period in early developmental stage modulates the AVER as a result from the neurocytological alteration from altering of GABA and ACh within the striate cortex was discussed. In conclusion, the AVER is a reliable and practical method for studying the effects of monocular deprivation and neuroplasticity in the rat visual cortex.

Visual Deprivation at the Critical Period Modulates Photic Evoked Responses

Average visual evoked responses (AVER) were recorded from the striate cortex of normal (control) and monocular visually deprived Long-Evans hooded rats. One month of monocular visual deprivation (MD) at the critical period of development resulted in marked reduction of all the three AVER components (i.e., components P2, N2 and P3) as compared to the control recording (P < 0.001). In control animals, the AVER amplitudes of the two hemispheres were identical, while in MD rats, the P2 and N2 components of the AVER obtained from the hemisphere ipsilateral to the MD eye were markedly smaller than those of the AVER obtained from the contralateral hemisphere (P < 0.001). The latencies of the late components (N2 and P3) obtained from the hemisphere ipsilateral to the MD eyes were significantly delayed as compared to those from the contralateral hemisphere (P < 0.05 for N2, P < 0.01 for P3). The AVER following paired photic stimuli with various time intervals between the stimuli were used to study the neuronal recovery function of control animals compared to MD animals. The AVER to the second stimulus obtained from the MD rats exhibited greater attenuation in their amplitude responses than the AVER obtained from the control group, i.e., slower neuronal recovery. The neurophysiological changes observed in this study may relate to the neurocytological alteration occurring in the striate cortex following monocular visual deprivation at the critical period. In conclusion, AVER recorded from monocular visually deprived rats during the critical period is a simple and reliable electrophysiological animal model to study neuroplasticity during postnatal development.