Peripheral cone dystrophy: a variant of cone dystrophy with predominant dysfunction in the peripheral cone system.
OBJECTIVE
To determine the phenotype of 3 patients from 2 pedigrees with an unusual form of cone dystrophy in which the peripheral cone system is more affected than the central cone system, and whose rod system is relatively normal.


METHODS
Three observational case reports with electrophysiologic and psychophysical studies.


METHODS
Three patients underwent fundus photography, fluorescein angiography, color vision testing, Goldmann visual field testing, full-field electroretinograms (ERGs), focal macular cone ERGs, and rod-cone perimetry, in addition to routine ophthalmologic examinations. Multifocal ERGs also were recorded from 2 patients.


RESULTS
The fundus examination and fluorescein angiogram results essentially were normal except for a mild temporal pallor of the optic disc in 2 patients. The corrected visual acuity ranged from 20/16 to 20/100. Color vision was normal in 1 patient, but was abnormal in 2 patients. A relative paracentral scotoma was detected in 2 patients. Full-field ERG cone responses were reduced significantly, but rod responses were normal in all patients, as in patients with typical cone dystrophy. However, the focal macular cone ERGs were well preserved in all patients. Psychophysical rod-cone perimetry demonstrated that the peripheral cone system was impaired, whereas the rod sensitivity was completely normal. The results of the multifocal ERG in 2 patients supported the findings made by the full-field and focal macular ERGs.


CONCLUSIONS
These findings demonstrate that there is a subgroup of patients with cone dystrophy where the peripheral cone system is more affected than the central cone system.
Kondo
Mineo
M
Department of Ophthalmology, Nagoya University School of Medicine, 65 Tsuruma-cho, Showa-ku, Nagoya 466-8550, Japan. kondomi@med.nagoya-u.ac.jp
Miyake
Yozo
Y
Kondo
Nagako
N
Ueno
Shinji
S
Takakuwa
Hideo
H
Terasaki
Hiroko
H
D000328:Adult; D003119:Color Perception Tests; D004596:Electroretinography; D005260:Female; D005451:Fluorescein Angiography; D006801:Humans; D008297:Male; D010375:Pedigree; D010641:Phenotype; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D012162:Retinal Degeneration / Q000175:diagnosis / Q000503:physiopathology*; D058609:Visual Field Tests; D014794:Visual Fields