The effect of conventional CR39 and Fresnel prisms on high and low contrast acuity

Oblique multi-periscopic prism for field expansion of homonymous hemianopia

Oblique Fresnel peripheral prisms have been used for field expansion in homonymous hemianopia mobility such as walking and driving. However, limited field expansion, low image quality, and small eye scanning range limit their effectiveness. We developed a new oblique multi-periscopic prism using a cascade of rotated half-penta prisms, which provides 42° horizontal field expansion along with 18° vertical shift, high image quality, and wider eye scanning range. Feasibility and performance of a prototype using 3D-printed module are demonstrated by raytracing, photographic depiction, and Goldmann perimetry with patients with homonymous hemianopia.

Efficacy of binocular vision training and Fresnel press-on prism on children with esotropia and amblyopia

PURPOSE

In the process of clinical diagnosis and treatment of amblyopia, we have found that the treatment time of this disease was significantly different among different patients. The purpose of this study was to compare the efficacy of binocular vision training (BVT) and Fresnel press-on prism (FPP) on children with esotropia combined with amblyopia.

METHODS

From May 2015 to December 2018, a total of 101 children aged 3-9 years with esotropia and amblyopia who were in our hospital were enrolled in this randomized clinical trial. They were randomly divided into combined group (48 cases) and prism group (53 cases): the children in the prism group received FPP treatment, and those in the combined group received the combined treatment of BVT and FPP. The visual acuity, the binocular function and the strabismic therapeutic effects were compared between two groups.

RESULTS

After treatment, the visual acuity in both groups was both significantly improved compared with that before treatment (P = 0.0079). The binocular-monocular function, including synoptophore visual function and the Titmus stereopsis, in both groups was significantly improved compared with those before treatment (P < 0.05), and it was more significant in the combined group compared with the prism group (P < 0.05). The cure rate of strabismus was 87.50% (42/48) and 30.19% (16/53) in the combined group and the prism group, respectively, and there was significant difference between groups (P = 0.0036). The cure time was shortened with the lower of the degree of esotropia.

CONCLUSION

BVT combined with FPP can effectively promote the recovery of binocular vision in children with esotropia combined with amblyopia, and some children can achieve complete cure of strabismus.

Photographic Depiction of the Field of View with Spectacles-mounted Low Vision Aids

SIGNIFICANCE

Photographic depiction helps to illustrate the primary and secondary field of view effects of low vision devices along with their utility to clinicians, patients, and caretakers. This technique may also be helpful for designers and researchers in improving the design and fitting of low vision devices.

PURPOSE

The field of view through spectacles-mounted low vision devices has typically been evaluated using perimetry. However, the perimetric field diagram is different from the retinal image and often fails to represent the important aspects of the field of view and visual parameters. We developed a photographic depiction method to record and veridically show the field of view effects of these devices.

METHODS

We used a 3D-printed holder to place spectacles-mounted devices at the same distance from the empirically determined reference point of the field of view in a camera lens (f = 16 mm) as they would be from an eye, when in use. The field of view effects of a bioptic telescope, a minifier (reverse telescope), and peripheral prisms were captured using a conventional camera, representing retinal images. The human eye pupil size (adjusting the F number: f/2.8 to f/8 and f/22 in the camera lens) and fitting parameters (pantoscopic tilt and back vertex distance) varied.

RESULTS

Real-world indoor and outdoor walking and driving scenarios were depicted as retinal images illustrating the field of view through low vision devices, distinguishing optical and obscuration scotomas, and demonstrating secondary effects (spatial distortions, viewpoint changes, diplopia, spurious reflection, and multiplexing effects) not illustrated by perimetric field diagrams.

CONCLUSIONS

Photographic depiction illustrates the primary and secondary field of view effects of the low vision devices. These images highlight the benefit and possible trade-offs of the low vision devices and may be beneficial in education and training.

2017 Charles F. Prentice Award Lecture: Peripheral Prisms for Visual Field Expansion: A Translational Journey

On the occasion of being awarded the Prentice Medal, I was asked to summarize my translational journey. Here I describe the process of becoming a low-vision rehabilitation clinician and researcher, frustrated by the unavailability of effective treatments for some conditions. This led to decades of working to understand patients' needs and the complexities and subtleties of their visual systems and conditions. It was followed by many iterations of developing vision aids and the techniques needed to objectively evaluate their benefit. I specifically address one path: the invention and development of peripheral prisms to expand the visual fields of patients with homonymous hemianopia, leading to our latest multiperiscopic prism (mirror-based design) with its clear 45° field-of-view image shift.

Treatment for Central-Peripheral Rivalry-Type Diplopia ("Dragged-Fovea Diplopia Syndrome")

PURPOSE

To report the effectiveness of treatments for central-peripheral rivalry (CPR)-type diplopia due to retinal misregistration.

DESIGN

Retrospective, interventional case series.

METHODS

Fifty adults with retinal misregistration and CPR-type diplopia (minimum frequency of "sometimes" at distance and/or for reading) caused by epiretinal membrane (n = 44) or other retinal disorders (n = 6) were enrolled in this study, conducted at adult strabismus clinics, Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, a tertiary medical center. Treatments included Bangerter filter, adhesive tape, Fresnel prism, clear prism (incorporated into glasses or loose prism in the office), iseikonic manipulation (using iseikonic lenses or contact lenses), a MIN lens, or epiretinal membrane (ERM) peeling (alone or in any combination). Not all patients underwent all of these treatments.

RESULTS

Main outcome measurements were diplopia frequency, evaluated using the Diplopia Questionnaire. Success was defined as "never" or "rarely" diplopic for distance and reading, using the Diplopia Questionnaire, at an outcome examination as close as possible to 6 months. Overall, 17 of 50 patients (34%; 95% confidence interval [CI], 21%-49%) were classified as successful. Fresnel prism was successful in 4 of 7 patients (57%; 95% CI, 18%-90%); Bangerter filter in 4 of 28 patients (14%; 95% CI, 4%-33%); ERM peeling in 8 of 18 patients (44%; 95% CI, 22%-69%); and iseikonic manipulation in 1 of 23 patients (using a contact lens; 4%; 95% CI, 0%-22%).

CONCLUSIONS

CPR-type diplopia may be relieved in some patients using nonsurgical treatment options consisting of Fresnel prism or Bangerter filter. ERM peeling was surprisingly successful and should be considered.

Reading aids for adults with low vision

BACKGROUND

The purpose of low-vision rehabilitation is to allow people to resume or to continue to perform daily living tasks, with reading being one of the most important. This is achieved by providing appropriate optical devices and special training in the use of residual-vision and low-vision aids, which range from simple optical magnifiers to high-magnification video magnifiers.

OBJECTIVES

To assess the effects of different visual reading aids for adults with low vision.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 12); MEDLINE Ovid; Embase Ovid; BIREME LILACS, OpenGrey, the ISRCTN registry; ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). The date of the search was 17 January 2018.

SELECTION CRITERIA

This review includes randomised and quasi-randomised trials that compared any device or aid used for reading to another device or aid in people aged 16 or over with low vision as defined by the study investigators. We did not compare low-vision aids with no low-vision aid since it is obviously not possible to measure reading speed, our primary outcome, in people that cannot read ordinary print. We considered reading aids that maximise the person's visual reading capacity, for example by increasing image magnification (optical and electronic magnifiers), augmenting text contrast (coloured filters) or trying to optimise the viewing angle or gaze position (such as prisms). We have not included studies investigating reading aids that allow reading through hearing, such as talking books or screen readers, or through touch, such as Braille-based devices and we did not consider rehabilitation strategies or complex low-vision interventions.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane. At least two authors independently assessed trial quality and extracted data. The primary outcome of the review was reading speed in words per minute. Secondary outcomes included reading duration and acuity, ease and frequency of use, quality of life and adverse outcomes. We graded the certainty of the evidence using GRADE.

MAIN RESULTS

We included 11 small studies with a cross-over design (435 people overall), one study with two parallel arms (37 participants) and one study with three parallel arms (243 participants). These studies took place in the USA (7 studies), the UK (5 studies) and Canada (1 study). Age-related macular degeneration (AMD) was the most frequent cause of low vision, with 10 studies reporting 50% or more participants with the condition. Participants were aged 9 to 97 years in these studies, but most were older (the median average age across studies was 71 years). None of the studies were masked; otherwise we largely judged the studies to be at low risk of bias. All studies reported the primary outcome: results for reading speed. None of the studies measured or reported adverse outcomes.Reading speed may be higher with stand-mounted closed circuit television (CCTV) than with optical devices (stand or hand magnifiers) (low-certainty evidence, 2 studies, 92 participants). There was moderate-certainty evidence that reading duration was longer with the electronic devices and that they were easier to use. Similar results were seen for electronic devices with the camera mounted in a 'mouse'. Mixed results were seen for head-mounted devices with one study of 70 participants finding a mouse-based head-mounted device to be better than an optical device and another study of 20 participants finding optical devices better (low-certainty evidence). Low-certainty evidence from three studies (93 participants) suggested no important differences in reading speed, acuity or ease of use between stand-mounted and head-mounted electronic devices. Similarly, low-certainty evidence from one study of 100 participants suggested no important differences between a 9.7'' tablet computer and stand-mounted CCTV in reading speed, with imprecise estimates (other outcomes not reported).Low-certainty evidence showed little difference in reading speed in one study with 100 participants that added electronic portable devices to preferred optical devices. One parallel-arm study in 37 participants found low-certainty evidence of higher reading speed at one month if participants received a CCTV at the initial rehabilitation consultation instead of a standard low-vision aids prescription alone.A parallel-arm study including 243 participants with AMD found no important differences in reading speed, reading acuity and quality of life between prism spectacles and conventional spectacles. One study in 10 people with AMD found that reading speed with several overlay coloured filters was no better and possibly worse than with a clear filter (low-certainty evidence, other outcomes not reported).

AUTHORS' CONCLUSIONS

There is insufficient evidence supporting the use of a specific type of electronic or optical device for the most common profiles of low-vision aid users. However, there is some evidence that stand-mounted electronic devices may improve reading speeds compared with optical devices. There is less evidence to support the use of head-mounted or portable electronic devices; however, the technology of electronic devices may have improved since the studies included in this review took place, and modern portable electronic devices have desirable properties such as flexible use of magnification. There is no good evidence to support the use of filters or prism spectacles. Future research should focus on assessing sustained long-term use of each device and the effect of different training programmes on its use, combined with investigation of which patient characteristics predict performance with different devices, including some of the more costly electronic devices.

Reading aids for adults with low vision

BACKGROUND

The purpose of low-vision rehabilitation is to allow people to resume or to continue to perform daily living tasks, with reading being one of the most important. This is achieved by providing appropriate optical devices and special training in the use of residual-vision and low-vision aids, which range from simple optical magnifiers to high-magnification video magnifiers.

OBJECTIVES

To assess the effects of reading aids for adults with low vision.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 1), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE, (January 1950 to January 2013), EMBASE (January 1980 to January 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to January 2013), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov/) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 31 January 2013. We searched the reference lists of relevant articles and used the Science Citation Index to find articles that cited the included studies and contacted investigators and manufacturers of low-vision aids. We handsearched the British Journal of Visual Impairment from 1983 to 1999 and the Journal of Visual Impairment and Blindness from 1976 to 1991.

SELECTION CRITERIA

This review includes randomised and quasi-randomised trials in which any device or aid used for reading had been compared to another device or aid in people aged 16 or over with low vision as defined by the study investigators.

DATA COLLECTION AND ANALYSIS

At least two authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included nine small studies with a cross-over-like design (181 people overall) and one study with three parallel arms (243 participants) in the review. All studies reported the primary outcome, results for reading speed.Two studies including 92 participants found moderate- or low-quality evidence suggesting that reading speed is higher with stand-mounted electronic devices or electronic devices with the camera mounted in a 'mouse' than with optical magnifiers, which in these trials were generally stand-mounted or, less frequently, hand-held magnifiers or microscopic lenses. In another study of 20 participants there was moderate-quality evidence that optical devices are better than head-mounted electronic devices (four types).There was low-quality evidence from three studies (93 participants) that reading using head-mounted electronic devices is slower than with stand-based electronic devices. The technology of electronic devices may have changed and improved since these studies were conducted.One study suggested no difference between a diffractive spectacle-mounted magnifier and either refractive (15 participants) or aplanatic (15 participants) magnifiers.One study of 10 people suggested that several overlay coloured filters were no better and possibly worse than a clear filter.A parallel-arm study including 243 participants with age-related macular degeneration found that custom or standard prism spectacles were no different from conventional reading spectacles, although the data did not allow precise estimates of performance to be made.

AUTHORS' CONCLUSIONS

There is insufficient evidence on the effect of different types of low-vision aids on reading performance. It would be necessary to investigate which patient characteristics predict performance with different devices, including costly electronic devices. Better-quality research should also focus on assessing sustained long-term use of each device. Authors of studies testing several devices on the same person should consider design and reporting issues related to their sequential presentation and to the cross-over-like study design.

The prismatic effect on stereoacuity in intermittent exotropia

PURPOSE

To evaluate the effect of acrylic refractive prism and Fresnel membrane prism on stereoacuity in intermittent exotropia.

MATERIALS AND METHODS

Stereoacuities of fifty-two patients (mean age, 12.4 years; range 6 to 45 years) with intermittent exotropia were measured using the Titmus and TNO stereotests, while they wore prisms of varying power on nonfixating eye or evenly on each eye.

RESULTS

Stereoacuities were significantly reduced with increasing prism power for both prisms, ranging from 8 to 25 prism dipotres. The effects on stereoacuity in single acrylic prism and single Fresnel prism were similar, whereas spilt Fresnel prisms reduced stereoacuity more than spilt acrylic prisms. Spilt prisms were found to have much less effect on stereoacuity than single prisms for both acrylic and Fresnel prisms.

CONCLUSION

The use of acrylic refractive prism shared evenly on each eye would be optimal method to minimize the reduction of stereoacuity during the prismatic therapy for intermittent exotropia.

Comparison of the visual effects of Fresnel prisms in normal and amblyopic eyes

PURPOSE

To assess the effects of Fresnel prisms on visual acuity and peak contrast sensitivity in the amblyopic and sound eyes of participants with amblyopia and to determine whether these functions were affected by Fresnel prisms to a different degree than those of controls.

METHODS

The LogMAR visual acuity and peak contrast sensitivity of 10 unilateral amblyopic participants (mean age, 22.6 years) and 9 controls (mean age, 26.2 years) were tested with Fresnel prisms of powers 5(Delta), 10(Delta), 15(Delta), 20(Delta), and 25(Delta) and without a Fresnel prism.

RESULTS

A statistically significant reduction in visual acuity with increasing prism power was found for all 3 groups, with the visual acuity of the amblyopic eyes being the least affected by the prisms. No statistically significant differences were found between the control and the sound eyes. No statistically significant differences in the effects of the prisms on peak contrast sensitivity could be detected between the 3 groups. Fresnel prisms were found to have a smaller effect on those amblyopic eyes with a poorer baseline visual acuity, indicating that these eyes may tolerate strong prisms without substantially impairing their visual acuity.

CONCLUSIONS

Fresnel prisms have a lesser effect on the visual acuity of amblyopic eyes than on controls. In contrast, results for peak contrast sensitivity were very similar for each of the groups tested, and no significant differences were evident between the amblyopic, sound, and control eyes.

Visual acuity through fresnel, refractive, and hybrid diffractive/refractive prisms

BACKGROUND

This article compares the effect on visual acuity of the Fresnel and wedge-shaped refractive prisms with newly developed hybrid diffractive/refractive prisms (ComPrisms), which combine a wedge-shaped refractive prism with a diffractive component. The diffractive component of hybrid elements can be designed to correct the chromatic aberration of the refractive component.

METHODS

The monocular visual acuity of 21 subjects and binocular acuity of 20 subjects were measured with computer-generated logMAR charts. Visual acuity was measured without prisms (NP) and through ComPrisms, 3M Press-on Fresnel, and acrylic refractive prisms of 20delta, 30delta, and 40delta powers.

RESULTS

A repeated measures analysis of variance indicates a significant main effect of treatment (without prisms and through the three types of prisms) at each prism power, both monocularly and binocularly. Results of the Scheffé test for all possible comparisons between pairs of means of the treatments are provided.

CONCLUSIONS

Although all the prisms reduced visual acuity, the ComPrisms provide significantly better visual acuity than acrylic refractive or 3M Press-on Fresnel prisms of equivalent power

A case of paradoxical diplopia in large-angle consecutive exotropia

PURPOSE

To describe the investigation and subsequent management of paradoxical diplopia in unsightly exotropia. A 32-year-old lady requested surgical correction of a large manifest consecutive exotropia which, on initial correction with any base-in prism, was accompanied by paradoxical diplopia.

METHODS

Botulinum toxin to the right lateral rectus reduced the deviation to 30 delta over a one-week period. The residual deviation was corrected with base-in Fresnel prisms which the patient wore constantly for another two weeks. Although there was demonstrable diplopia initially, it disappeared after 3-4 days of prism wear. Surgery was carried out comprising right lateral rectus recession (6 mm) and right medial rectus advancement from 12 mm to 6 mm posterior to the limbus.

RESULTS

There was no diplopia following the surgery and the residual exodeviation measured 6 delta for near and 16 delta for distance (fixing OD). The patient remains symptom-free and cosmetically excellent.

CONCLUSION

A gradual progressive reduction in the deviation using a combination of Botulinum toxin and prisms allowed a more informative conclusion to be made regarding the potential post-operative sensory status in this patient, by allowing her to slowly adjust to an altered ocular alignment. In patients with non-functional strabismus who may be at risk from post-operative diplopia, a trial with prisms over a few weeks with or without the addition of Botulinum toxin is advocated.