Peer-reviewed Articles

Please use the archived list on the right to look at past peer-reviewed articles.

1998

Dengis,C. A., Simpson,T. L., Steinbach,M. J., Ono,H. The Cyclops effect in adults: Sighting without visual feedback. Vision research 1998;38,2:327-331. [ Show Abstract ]

When asked to look through a tube, younger children place it at the bridge of the nose, and not over one eye: the Cyclops effect. This is a natural response to a median plane egocenter. With maturity, the Cyclops effect disappears as we learn to overcame the consequences of an egocenter between the two eyes, and instead, to use the 'preferred' eye. We videotaped adults (n = 14) and children with normal vision (n = 30), children with comitant strabismus (n = 14), and adults and children (n = 14) with one eye enucleated as they attempted to look through a plastic tube. Immediately in front of the face was a liquid crystal window that could be either transparent or opaque. As the tube was raised, the window was made opaque-blocking sight of the target, their hands, and the tube. Most binocular observers placed the tube approximately at the bridge of the nose. This was significantly different from the response of the enucleated observers who put the tube 75% of the way to the remaining eye (P = 0.0001). All observers align, on average, with the measured location of their egocenter when asked to perform a monocular task without visual cues. Deprived of visual feedback, binocular observers show the Cyclops effect, regardless of age.

Elliott,D. B., Situ,P. Visual acuity versus letter contrast sensitivity in early cataract. Vision research 1998;38,13:2047-2052. [ Show Abstract ]

Large and small letter contrast sensitivity and visual acuity were assessed in 37 elderly eyes (mean VA -0.01 logMAR, Snellen 6/6) and their lens opacities were categorised and graded using the LOCS III system. Large letter contrast sensitivity was often not reduced in cataract from age-matched normal values and provided limited information. Small letter contrast sensitivity was shown to be a more sensitive measure of early cataract than visual acuity and large letter contrast sensitivity. Its usefulness may be limited by its strong correlation with visual acuity (r2 = 0.70), which is the standard and traditional measure of vision in cataract.

Elliott,M., Fandrich,H., Simpson,T., Fonn,D. Analysis of the repeatability of tear break-up time measurement techniques on asymptomatic subjects before, during and after contact lens wear. Contact Lens and Anterior Eye 1998;21,4:98-103. [ Show Abstract ]

This study assessed the repeatability of various methods of measuring tear break-up time (TBUT) with and without soft contact lenses (CLs).TBUT was measured on 22 subjects with the tearscope, videokeratoscope and slit-lamp before and after 30 min of soft CL wear, and immediately after CL removal. Slit-lamp corneal TBUT was measured with fluorescein and without fluorescein while wearing CLs. TBUT was measured three times on the right eye only, using each technique in randomised order. TBUT measurements on CLs were repeated a second day. TBUT measurements were highly variable under all conditions and our results indicated a lack of correlation between techniques. The videokeratoscope was the least repeatable; while the tearscope was the most repeatable technique.

Elliott,M., Simpson,T., Richter,D., Fonn,D. Repeatability and comparability of automated keratometry: The Nikon NRK-8000, the Nidek KM-800 and the Bausch and Lomb keratometer. Ophthalmic and Physiological Optics 1998;18,3:285-293. [ Show Abstract ]

This study assessed the repeatability of the Nikon NRK-8000, the Nidek KM-800 and the Bausch and Lomb keratometer. In addition, the comparability of the Nikon NRK-8000 and the Nidek KM-800 are evaluated relative to the Bausch and Lomb keratometer. Measurements were taken with all three techniques on two separate occasions with a test-retest separation of at least 24 hr. The right eyes of 30 normal subjects were used. Repeatability and comparability statistics and plots were generated using matrix representations of dioptric power. The Nidek KM-800 coefficient of repeatability values were found to be 0.345, 0.187, and 0.321 in the vertical, torsional, and horizontal meridians while the Nikon NRK-8000 values were 0.346, 0.232, and 0.276 respectively.

Pritchard,N., Fonn,D. Post-lens tear debris during extended wear of hydrogels. Canadian Journal of Optometry 1998;60,2:87-91. [ Show Abstract ]

Debris entrapment after overnight wear of hydrogel lenses has been implicated as a cause of adverse ocular responses. We conducted two short-term pilot studies to determine if post-lens debris is related to the duration of lens wear, lens binding after overnight wear, movement of the lens prior to sleep or lens type. Debris and lens movement patterns upon waking were examined after one night (1N), one day and one night (1D+N) and one week of extended wear (6N). Three lens types were used on 10 subjects for the 1N experiment, and one lens type was used on 6 different subjects for the 1D+N and 6N experiment. Debris did appear to increase with duration of wear and was observed in approximately 60% of subjects after 1N. The appearance of debris observed ranged from light grey streaks to small clumped patches. Acuvue was bound more frequently than Medalist and NewVue. Movement was re-established after approximately 4 minutes of eye opening; however, the lenses appeared more adherent after 6N of overnight wear than after 1N or 1D+N. Debris dissipated after approximately 15 minutes (range 9 to 24 minutes) following eye opening. No statistical association was made between debris, lens binding, movement and lens type in this small group of subjects. These experiments demonstrated that debris appears to increase with duration of wear, may be associated with lens binding in a larger group and is quite difficult to view and quantify.

Sorbara,L., Richter,D., Chong,T. Evaluation and comparison of videokeratoscopic simulated fluorescein programs. 1998;60,3:158-163. [ Show Abstract ]

Software for designing rigid gas permeable contact lenses has been developed for a number of corneal topography systems. There are some common and some unique features in the fitting programs of these instruments. Three currently available instruments are compared and contrasted to traditional contact lens fitting. These instruments are the EyeSys (EyeSys Technologies), the EyeMap (Alcon) and the TMS (Computed Anatomy, Tomey).