The diagnosis of a peripheral tapeto-retinal degeneration (retinitis pigmentosa) can usually be suspected from the ophthalmoscopic findings and can be confirmed by electroretinography. However, in the early stages of the disease, the fundus may be practically normal or show a picture which is entirely different from that of the same disease in its late stages.
In the two patients presented in this paper, the disease manifested itself primarily as a macular cyst or hole. The nature of the macular changes could be revealed in one patient by fluorescein studies, and the diagnosis could in both be confirmed by electroretinography.
Case No. 1: A 21-year-old woman complained of deterioration of vision during the last two years especially at night. Ocular examination revealed a visual acuity of 6/12 in each eye, and abnormal findings in the fundus. These consisted of a circumscribed, round, red patch about 1A disc diameter in size over each macular area (Fig. I). In the left eye a single "bonecorpuscle" pigmentary spot was seen at the equator in the upper nasal quadrant. The discs and blood vessels were normal. SUt lamp examination showed .the red patch over the macular area to be a macular eyst.
The patient was seen again six months later. The described fundal findings did not change, but, in addition, pigment in the form of a fine powder was seen in the upper temporal quadrants. Fluorescein studies showed increased and spotty fluorescence in the macular area which normally dues not stain. (Fig. 2). Color vision was normal.
The electroretinogram was very subnormal (Fig. 3). After 30 minutes in the dark, the negative wave showed an amplitude of about 50 microvolt, and the positive wave about 100 microvolt. With the methods used in this laboratory these findings are pathognomonic of a peripheral tapeto-retinal degeneration.
The electrooculogram showed a light rise of 127 per cent (minimal normal is 185 per cent). The visual evoked response was very subnormal when either eye was stimulated (Fig. 4). The psychophysical dark adaptation curve showed a severe affection of the scotopic mechanism and to a lesser extent of the photopic mechanism (Fig. 5).
The patient was an offspring of a consanguineous marriage, the parents being third degree cousins. No additional cases were reported in the family. Her parents and only sister were examined and found to be normal.
Conclusion: Tapeto-retinal degeneration (pigmentary retinal dystrophy) presenting itself initially as bilateral macular cystoid degeneration.
Case No. 2: A 7-year-old girl complained of progressive night blindness. On examination a visual acuity of 6/9 was found in each eye. Ophthalmoscopy revealed bilateral macular cysts. The left eye had also fine pigmentary stippling in the macular area. The electroretinogram was very subnormal (Fig. 6) and on this basis peripheral tapeto-retinal degeneration was diagnosed.
Fig. 1 A. Fundus of the right eye of Case I. The macular area has the typical appearance of a cyst or "hole. "
Fig. 1 B. Fundus of the left eye of Case I. The macular area has the typical appearance of a cyst or "hole. "
Fig. 2 A. Fluorescein angiography photographs of right eye of Case 1. In arterial phase, a few dots of fluorescence appear in the macular area.
Fig. 2 B. In the arteriovenous phase, the macular fluorescence increases.
Fig. 2 C. The macular fluorescence decreases again, together with the disappearance of the choroidal fluorescence in the recirculation phase. This picture was taken 7 minutes after first appearance of dye.
Fig. 3 ERG of right eye (upper curve) and left eye (lower curve) in Case 1, showing very subnormal negative and positive waves, typical of peripheral tapeto-retinal degeneration. (Calibration: horizontal, 20 msc, vertical, 100 microvolt; 28 minutes in dark).
Two years later ophthalmoscopy revealed a flat, elongated paramacular cyst in the left eye (Fig. 7) and a small, flat, barely visible foveal cyst in the right eye. In addition, pigment in the form of a fine powder and several "bone-corpuscles" were seen' in the midperiphery of both fundi.
Conclusion: Tapetoretinal degeneration (pigmentary retinal dystrophy) presenting itself initially as bilateral macular cystoid degeneration.
Peripheral tapeto-retinal degeneration (pigmentary retinal dystrophy; retinitis pigmentosa) may start initially as fine pigmentary changes in the macular areas with typical peripheral changes following later.2 Some macular pigmentation is seen in 60 per cent of patients with this disease.3 Other macular changes such as macular cysts or "holes" are relatively rare. Although it is mentioned in the literature4-6 that this can be the initial manifestation of a pigmentary retinal dystrophy, this fact is not widely known. Vogt, describing a 13-year-old boy with this finding, claimed that this is seen only in young patients.4 Stock7 and Ginsberg8 each reported a case of pigmentary retinal dystrophy in which histological examination revealed macular changes; the first found a macular "cyst," and the second a macular "hole."
Fig. 4 Visual evoked response in Case I. The is very subnormal. (70 stimuli and averaged on CA Calibration: horizontal, 25 msec: vertical, microvolt).
Fig. 5 Psychophysical dark adaptation curve of Case 1 showing subnormal scotopic and, to a lesser extent, subnormal photopic activity. (Monochromatic light of 500 nm after 5 min light adaptation).
In the two patients described in this paper, macular cysts were the initial findings, pigmentary changes in the retina appearing later. However, based on the electrophysiologic studies, the diagnosis of a peripheral tapetoretinal degeneration was made before the pigmentary changes appeared.
The fluorescein studies performed in Case 1 gave similar results to our findings in other established cases of macular cysts. The macular cysts are probably seen only in the initial stages of tapeto-retinal degeneration and disappear later or change as in Case 2.
Macular cysts can also be seen in young patients in cases of congenital macular degeneration (Best's disease). The differential diagnosis is not difficult when electrophysiologic studies are performed as the ERG can distinguish between those two conditions.
Two patients are described in whom macular cysts were the initial changes of a peripheral tapetoretinal degeneration. Later typical pigmentary changes appeared in the periphery of the fundus. The value of electrophysiologic studies for the differential diagnosis of macular cysts in young patients is discussed.
Acknowledgment: I wish to thank Prof. E. Auerbach, the head of the Vision Research Laboratory, and Mrs. H. Rowe for the electrophysiologic studies performed; Mr. M. Ivri for the fundus photographies; and Prof. I.C. Michaelson and Dr. Sonnies who referred the patients.
Fig. 6 ERG of Case 2 showing in right eye (upper curve) practically extinct electrical responses, and in ieft eye (lower curve) only a slight response. (Calibration: horizontal, 20 msec; vertical, 100 microvolt; 20 minutes in dark).
Fig. 7 Fundus of left eye of Case 2 showing a paramacular flat cyst 2 years after the first examination of the child and at the stage of regression. (The white patch beneath the cyst is an artefact due to the light reflex).
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