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Electrodiagnosis :

Case Studies

Introduction | Electrical Changes Recordable from the Eye | Electrical Changes Recordable from the Brain: The Visually Evoked Potential | Clinical Application of Electrodiagnosis Tests of the Visual System | Summary | Indications for Electrophysiologic Tests on the Eye | Case Studies

Case 11.1

A male infant was brought in following insignificant blunt injury to the left eye. Examination revealed inferior bone spicule pigmentation of both fundi. There was no history of night blindness and no known family history of eye disease. The eye exam-ination showed RV 6/6 and LV 6/6, both unassisted. The visual field exhibited upper-half defects in both eyes. There was selec-tive raising of the dark-adaptation threshold iin the upper-half field. The ERG showed markedly reduced amplitude in the left eye, Some of these results are presented in Figure 11.21. The diagnosis was sectorial retinifiti pigmentosa.

fig. 11.21

Figure 11.21. Clinical findings (A) and electroretinogram (B) from case 11.1.

Case 11.2

A 21-year-old male presented with len. side weakness and blurred vision. One year previously, he had suffered a right parietal intracerebral hemorrhage with no vascular abnormality. After a nearly complete recovery, he had a grand mal seizure about months later. At that time, he was started on phenytoin, 300 mg at night and in the morning. After returning to his job in Zanzibar, hu had contracted cerebral malaria and had been treated with "large doses" of quinln intravenously. He recovered gradually, but presented with his current symptoms after several months.

The eye examination revealed RV 6/18 and LV 6/5, both with glasses. The fundi appeared as pale discs with arteriolar attenuation. The intraocular pressure was 15 mm in both eyes, and the visual fields showed generalized constriction. The EOG and ERG for this patient are presented in Figure 11.22.

Discussion
The ERG shows a reduced `b'-wave amplitude, and the EOG shows an abnormal Arden index. These findings are more consistent with quinine poisoning than with optic atrophy following anemia or compression of the visual pathway.

fig. 11.22

Figure 11.22. The electroretinogram (A) and electro-oculogram (B) from case 11.2.

Case 11.3

A 70-year-old male presented with the complaint that for more than 9 years straight lines had looked bent to him. When he was seen 9 years earlier, a yellow cyst at the right macula and scar at the left macula had been noted. The patient's deceased father had been unable to read in later years. The eye examination showed RV 6/9 unassisted and LV 6/24 with glasses. The results of electro.

Discussion
The EOG shows a reduced light rise on the left side, whereas the ERG was within the normal range for both eyes. These findings together with the fundus appearance confirm a diagnosis of Best's disease.

fig. 11.23

Figure 11.23. The electroretinogram (A) and electro-oculogram (B) from case 11.3.

Case 11 .4

A 12-year-old boy, who had been using a hammer and chisel the previous day, was admitted with eye pain and irritation. An intraocular metallic foreign body was removed from the left eye with a magnet the same day. Postoperatively, the injured eye became painful with hypopyon. After treatment with systemic and local antibiotics, the eye initially improved, but the patient's vision remained poor. The ERG was normal on the right but absent on the left (Fig. 11.24). A left lensectomy and vitrectomy with silicone oil exchange was performed 12 days later. Massive preretinal exudate and total retinal detachment were observed during surgery. Follow-up examination about 6 weeks later Showed the retina in situ and LV 6/60.

Discussion
The diagnosis of posttraumatic endophthalmitis following removal of the foreign body is straightforward, as this condition most commonly is secondary to intraocular Surgery or penetrating trauma. The flat ERG from the left eye suggests retinal detachment, but this test should always be combined with a flash VEP and ultrasound examination to obtain maximum information about structure and function through Opaque media.

fig. 11.24

Figure 11.24. Electroretinogram from case 11.4.