The development of fixing and focusing behaviour in normal human infants as observed with the Otago photoscreener

The Otago photoscreener is an optical instrument which gives a very sensitive indication of the accuracy with which a subject's eyes are fixing and focusing. Early experience suggested that this instrument could be used effectively to screen for the presence of amblyogenic factors in pre-verbal infants. This communication describes the development of ocular fixation and focusing in 137 normal infants who were followed at regular intervals during the first year of life. Accurate fixation and focusing was found in 13% of three-month-old infants, in 68% of six-month-old infants and in 76% of one year olds. The levels of 'focusing' visual acuity obtained from the photoscreen data are considerably better than the levels of cortical acuity measured by the standard behavioural and electrophysiological methods. This suggests that human infants fix and focus accurately for a considerable period before they are able to perceive all the details obtained in their retinal images.     

A HOSPITAL RENTAL SYSTEM FOR LOW VISION AIDS

Costly low vision aids are rented to patients by the Otago Hospital Board Occupational therapists see the patients in the Low Vision Clinic and then as necessary in their homes As a consequence accurate follow-up and analysis of the help provided by these aids is available Patients with senile macular degeneration use telescopic reading aids for an average of 27 months after they are prescribed     

Reliability of the Otago photoscreener A study of a thousand cases

The Otago photoscreener is a 35 mm single lens reflex camera in which the flash light comes from a narrow ring around the outer margin of its lens. The margin is also the limiting aperture of the optic system and in the centre of the lens is a flickering fixation light. In a colour photograph taken at a distance of 66 cm from the face of the subject who is accurately focusing on and fixing the camera fixation light with both eyes, the fundus reflex in each pupil is very dark red and the corneal light reflexes are symmetrical. If either or both eyes are not appropriately focused or fixing, the fundus reflex is brighter and yellow or white. This article describes a prospective trial of the performance of the Otago photoscreener in a series of 1000 infants with actual or suspected amblyopia, refractive error or strabismus. In this study photoscreening showed a sensitivity of 94% and a specificity of 79%. Photoscreening also identified some cases of esotropia and of refractive error which were missed on clinical examination. In this series photoscreening passed as normal three children with mild to moderately severe amblyopia. This represents les than 1 % of the clinically abnormal children.     

Keratoconus: diagnosis and management

Keratoconus is a common condition whose clinical features represent a common effect on the cornea of a number of diverse processes. This review deals with the clinical signs and accompanying histological and biochemical changes within the cornea, evaluates the significance of associated ocular and systemic conditions and assesses the incidence and prevalence of the disorder.
The wider ophthalmic community shares in the treatment of keratoconus, so the general principles of contact lens fitting associated with this difficult condition are examined and the specific protocol used at the Flinders Medical Centre is presented. When contact lenses are not tolerated or an adequate improvement in visual acuity is not achieved, surgery is the next option, so a full assessment is made of the risks and benefits of penetrating keratoplasty. Older techniques, such as thermokeratoplasty and lamellar keratoplasty, are examined and the new technique of epikeratophakia is evaluated.