The pressure phosphene tonometer--a clinical evaluation.

AIMS: Pressure phosphene tonometry is said to assess intraocular pressure by inducing a pressure phosphene. This study compared the results of this relatively new technique with Goldmann applanation tonometry. METHODS: A total of 100 patients (196 readings) in a general ophthalmology clinic at Dunedin Hospital who consented to take part in this study were randomised to receive by different examiners either pressure phosphene tonometry by a Proview eye pressure monitor (Bausch & Lomb Inc., Tampa, FL, USA) or Goldmann tonometry first. There was no communication between the examiners regarding results. RESULTS: Of the 196 attempted readings, pressure phosphene tonometer readings were only able to be obtained for 136 eyes (69%) compared to all 196 (100%) eyes with the Goldmann tonometer. The mean IOPs were 18.5 mmHg using the pressure phosphene tonometer and 16.0 mmHg using the Goldmann tonometer. The mean difference was +2.43 mmHg (95% confidence interval: 10.37 mmHg below to 15.22 mmHg above Goldmann readings). CONCLUSION: This study found that 31% of patients could not perceive a pressure phosphene using the Proview eye pressure monitor. Data obtained from those who could perceive the phosphene indicated that large discrepancies between pressure phosphene tonometry and Goldmann tonometry were common.

Apparent accommodation and depth of field in pseudophakia.

PURPOSE: To assess depth of field in phakic and pseudophakic eyes to explain good distance and uncorrected near visual acuity in pseudophakic eyes. SETTING: Department of Ophthalmology, University of Otago Medical School, Dunedin, New Zealand. METHODS: Depth of field was measured in pseudophakic (n = 10) and phakic (n = 10) eyes for both near and distant targets. Test conditions included cycloplegia and a constant pupillary aperture using a soft contact lens with a central artificial pupil diameter of 2.5 mm. RESULTS: There was no statistically significant difference between phakic and pseudophakic eyes for any test. Depth of field for near visual acuity was +/-0.85 diopters (D), but amplitude of legibility was +/-1.94 D. Depth of field for distance visual acuity was between 0.25 and 0.50 D in 85% of eyes. CONCLUSION: In the absence of astigmatism and disease, a pseudophakic eye with -0.75 D of myopia can expect to achieve 20/30 uncorrected distance acuity and read N5 unaided if the pupil is approximately 2.5 mm.

Reliability of the Otago photoscreener. A study of a thousand cases.

The Otago photoscreener is a 35 mm single len 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.

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 behavioral 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.

Refractive error, IQ and reading ability: a longitudinal study from age seven to 11.

Children from a population sample whose cycloplegic refractive errors included myopia, pre-myopia and hypermetropia were compared on measures of IQ and reading with a group of children without significance refractive errors. At age 11 both those with myopia and with pre-myopia had increased verbal and performance IQ, while those with hypermetropia had slightly reduced verbal and performance IQ, in comparison with the children without refractive errors. The differences in verbal IQ were not attributable simply to earlier differences, but the differences in performance IQ were attributable to earlier differences. No significant differences in reading scores were found at either age. It is concluded that differing abilities of myopic and other children at age 11 are not fully explained by differences in family background or in pre-existing ability.

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.

Clinical experience with the Otago Photoscreener.

The Otago Photoscreener provides a sensitive indication of whether or not an infant is able to fix and focus binocularly on nearby objects. This instrument was designed for mass screening to identify infants with strabismus and/or amblyopia who do not fix and focus binocularly. This communication reports the authors' experience with the machine in the diagnosis and treatment of strabismus and amblyopia.

Bacteriological studies of contamination of hydrophilic contact lenses with Staphylococcus epidermitis.

An attempt was made to contaminate hydrophilic contact lens material with Staphylococcus epidermitis. This study was initiated as a result of some clinical investigations which had revealed the presence of coagulase-negative staphylococcal infection in eyes fitted with this type of contact lens. It was though particularly relevant in view of the known association of some strains of this organism with other plastic prostheses. In vitro cultures proved unsuccessful in demonstrating the ability of this bacterium to metabolize the lens material.