Vision is very important for primates in their physical and social lives. The present investigation was conducted to clarify characteristics of behavioral development of a cynomolgus monkey (Macaca fascicularis) infant with congenital cataracts and to study the infant's interactions with its mother and other cage mates. Subjects were five pairs of mothers and infants, includung a pair in which the infant had congenital cataracts. Observations were made once or twice a week for 15 minutes each. Observations were made of interactions between the congenital cataract infant and its mother for the infant's first 18 weeks of life. At eight months the infant was separated from its mother and placed with a peer until it was two and a half years old. It was then housed with a youger infant.

The infant with congenital cataracts showed slight retardation in behavioral development, but, on the whole, its locomotion and filial behavior developed normally. The infant did not develop any stereotyped behaviors which might have been caused by social isolation. However, the animal did show maladjustment in interaction with a peer. It appears that a severe visual defect does not produce problems in the simple mother-infant situation. On the other hand, it may have an important negative effect in more complex peer interactions.

We invented a method for observing the ocular fundus of fishes with ophthalmoscopes for human beings or with a portable fundus camera for small laboratory animals. Almost all fishes have two characteristic ocular features which make observation of the fundus difficult: the extremely refractive lense (Ca. 145 D in carp, Ca. 523 D in crucian carp), and the other streamlined surface of the cornea, which causes astigmatism in air. However, the fish eye is not astigmatic when in water, because the refractive index of the fish cornea approximately equals that of water, so that little refraction occurs at the corneal surface. Difficulties caused by these features in air observation were eliminated by covering the cornea with a contact lens, and by filling the space between the contact lens and cornea with distilled water.

Prior to ophthalmoscopy, the fish (carp) was anesthetized in well aerated 220 ppm MS222 (tricaine methanesulfonate) solution. Anesthesia was maintained during ophthalmoscopy with well aerated 100 ppm MS222 solution by which the gill surfaces of the fish were irrigated through the mouth.