Myopia affects up to one-third of the population in the United States today. It is a leading cause of low vision in Asian countries secondary to the increased risk of retinal detachments and glaucoma. Genetics, as well as environmental factors and nearwork have been hypothesized to play a role in myopia development. Current techniques to control its progression target these etiologies. Methods of myopia control that have been explored include: vision and behavioral therapy, contact lenses, multifocal lenses, and pharmaceutical agents. In the realm of vision and behavioral therapy, prior non-controlled studies are encouraging. Bifocal contact lenses appear to have high potential in reducing myopia. Atropine, pirenzepine, biofeedback, and progressive lenses have shown promising results, predominantly in young esophoric myopes. Many of the current studies, particularly those involving vision therapy, atropine, pirenzepine, and orthokeratology lenses, should be repeated to quantify the influence on myopia progression. Myopia control continues to be an area of active research.
Monocular Estimate Method Retinoscopy was used twice to measure the accommodative posture of 211 pre-presbyopic subjects. It was first measured with their farpoint lenses in place, and second, with the farpoint lenses and nearpoint plus lens additions (PLA) in place. The PLAs utilized for the second MEM were based on the binocular cross cylinder findings. The findings from the MEM-twice procedure were used to calculate the change in accommodative response that occurred from the plus lenses. The predominant change was a reduction of accommodation by an amount less than the dioptric power of the PLA, and the mean change was negative accommodation equal to 62% of the PLA. This tendency for incomplete negative accommodation to occur in response to a PLA shifted accommodative posture to less lag or more lead for over 3/4 of the subjects. The changes in accommodative response and posture that are revealed by the MEM-twice procedure are consistent with previous studies of how accommodation changes in response to a nearpoint plus lens. The MEM-twice method is a procedure to determine whether a PLA is indicated or contraindicated for the particular patient.
Many experiments conducted by behavioral scientists involve brief presentation of visual stimuli. These experiments frequently utilize subjects with only self-reported normal vision. It has been observed, however, that at least some of these subjects possess visual deficits that affect the processing of visual stimuli under normal viewing conditions. Experiment 1 examined whether participants with only self-reported normal vision process briefly presented visual stimuli as accurately as those with verified normal vision. Results indicate that a group with only self-reported normal vision actually possess a number of deficits at both near- and farpoint. Further, this group processed briefly presented visual stimuli significantly less effectively as compared to a group with verified normal vision. The most prevalent visual deficits observed in experiment 1 were nearpoint binocular deficits as determined by the Keystone Visual Skills Series. Experiment 2 therefore, examined the effects of specific nearpoint binocular deficits on brief stimulus processing. Results indicate that both underconvergence and overconvergence binocular deficits at near point have a significant negative effect on the processing of briefly presented visual stimuli. Overall results are discussed in terms of reducing extraneous variance factors by carefully assessing vision capabilities, particularly nearpoint binocular deficits, in experiments utilizing briefly presented visual stimuli. Implications of the findings for optometric researchers and clinicians are discussed.
There is widespread recognition of progressive addition lenses (PALs) as a tool for the correction of presbyopia condition. The selective spatial effects of different PAL designs may prove useful in more specific optometric therapies. The potential to make such applications depends on an understanding of the underlying principles and consequences of PAL design. Those principles are dealt with qualitatively, affording the practitioner the opportunity to intelligently select and apply progressive addition lenses. Less heralded is their utilization when the need for an addition is not based on this.