Physiologic correlates of the ERG hyperventilatory response in dogs.

Previous studies in man have shown that hyperventilation consistently enhances the amplitude of the electroretinogram (ERG) b-wave, but has little effect on the a-wave. The present study examined this phenomenon in the dog; central (centrifugal) and peripheral (sympathetic) neural effects and changes in arterial pO2 and blood pH were excluded as physiologic bases for the phenomenon. It was concluded, therefore, that the underlying mechanism must be decreased pCO2 (hypocapnia), although the specific site of action and the method by which the ERG b-wave is enhanced remain topics for future research.

Atypical vitelliform macular dystrophy in a 5-generation family.

Five generations of a family with autosomal dominant atypical vitelliform macular dystrophy (A-VMD) were studied. This dystrophy is similar to autosomal dominant Best's vitelliform dystrophy (B-VMD) but clinically more closely resembles sporadic pseudovitelliform macular degeneration (P-VMD). Of the family members who were 14 years or older 43 (24 females and 19 males) of the 101 at risk (43%) were affected. Vision varied from 20/20 to 20/200. Field defects and tritan colour defects were invariably present only when vision was less than or equal to 20/200, but these defects were sometimes present when vision was good. The electrooculographic studies (LP/DT ratios) in this family were found to be normal or reduced and did not correlate with visual acuity. Minimal retinal findings consisted of macular or extramacular punctate yellow lesions or both in the retinal pigment epithelium, which were hypofluorescent by angiography, and retinal pigment epithelial defects in the temporal nerve fibre bundle, which were hyperfluorescent by angiography. Fluorescein angiographic changes were invariably present when retinal lesions were noted, and this was the most reliable test in identifying genotypically affected family members with minimal phenotypic expression.

Oculocutaneous albinoidism as a manifestation of reduced neural crest derivatives in the Prader-Willi syndrome.

Nine patients with Prader-Willi syndrome (five female and four male; one Oriental and eight white), all of whom had interstitial deletions of the proximal long arm of one chromosome 15 (q11-q13) were found to have decreased tyrosinase activity in isolated hair bulbs. As infants, all patients had light hair and skin coloring, both of which darkened with age. Light and electron microscopic analysis of skin and hair bulbs disclosed a reduced number of melanocytes in the basal epidermis and hair bulbs. Each patient demonstrated decreased pigmentation of the iris stroma, which was accentuated peripherally and manifested clinically as iris translucency. There was no foveal hypoplasia, nystagmus, or photophobia, and ocular function was normal. Oculocutaneous albinoidism is thus a component of del(15q) Prader-Willi syndrome with reduction of melanocytes of neural crest origin (skin, hair, and iris stroma) and retention of normal retinal and iris pigment epithelia of neuroectodermal origin.

X-linked recessive congenital stationary night blindness, myopia, and tilted discs.

A family with X-linked recessive congenital stationary night blindness, myopia, and tilted discs has been identified. All affected members have decreased vision, nystagmus, strabismus with decreased binocular function, visual field defects, abnormal fundus appearance with typical fluorescein angiographic findings of tilted disc syndrome, abnormal electroretinograms, and abnormal visual evoked responses to patterned stimuli. Similar clinical evaluation of an obligate carrier revealed no ocular abnormalities.