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

https://doi.org/10.1016/j.jaapos.2008.03.015Get rights and content

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 5Δ, 10Δ, 15Δ, 20Δ, and 25Δ 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.

Section snippets

Materials and Methods

This was a prospective case-controlled study. Participants with amblyopia were recruited from those patients with a history of unilateral amblyopia, attending an orthoptic clinic at one location (Altnagelvin Area Hospital, Londonderry, UK) and were tested by one investigator (DW). This study received ethical approval from the Office for Research Ethics Committees Northern Ireland and from the National Health Service Trust, where the research was conducted. All participants read an informational

Results

Ten individuals with amblyopia (5 male, 5 female subjects; mean age, 22.6 years; range, 11-33 years) and 9 controls (3 male, 6 female subjects; mean age, 26.2 years; range, 21-45 years) participated. Of the 10 participants with amblyopia, 5 had strabismic amblyopia, 4 had mixed strabismic and anisometropic amblyopia, and 1 had anisometropic amblyopia. Of the amblyopia group, 6 wore glasses. The spherical equivalent of refractive correction for the amblyopic eyes ranged from −0.50 D to + 6.00 D.

Visual Acuity

This study showed that visual acuity with Fresnel prisms decreases with increasing prism power in control eyes and in both the amblyopic and the sound eyes of amblyopic participants (Figure 1). The effect on visual acuity in the control eyes and sound eyes of amblyopic participants was similar. Baseline visual acuity in amblyopic eyes was lower than in the other groups, and the amount of decrease in visual acuity with prism was less than the decrease found for both control eyes and sound eyes.

References (14)

There are more references available in the full text version of this article.

Cited by (15)

  • Diagnosis of amblyopia

    2021, Journal de Pediatrie et de Puericulture
  • Achromatic refractive–diffractive double-relief microprisms

    2020, Optics and Lasers in Engineering
    Citation Excerpt :

    However, the application of prisms generally involves chromaticity problems due to the dispersion of white light at the microrelief. Many studies have reported the deterioration of the formed optical images and patient's visual acuity during ophthalmological diagnostics using microprisms [5‒8]. Recent studies have reported the influence of microprisms on the contrast and resolution of test images using a new electronic method [9,10].

  • Light filters influence on the chromaticity for Fresnel microprisms

    2020, Optik
    Citation Excerpt :

    In the last years, flexible Fresnel microprisms have been widely used in ophthalmology all over the world for diagnostics and treatment strabismus [3–8]. The application of Fresnel microprisms always reduces the resolution of the formed optical images [9–14] due to the decrease of their contrast. The main reason for reducing the contrast and for worsening the resolution of optical images when using prisms is the white light chromaticity which occurs when the light rays of different wavelengths are refracting on the prism surfaces.

  • Treatment for Central-Peripheral Rivalry-Type Diplopia (“Dragged-Fovea Diplopia Syndrome”)

    2019, American Journal of Ophthalmology
    Citation Excerpt :

    In the study by Iacobucci and associates11 Fresnel prism was applied in combination with a Bangerter filter (to create a central scotoma). Hypothetically Fresnel prism alone may be successful because it not only prevents peripheral motor fusion but simultaneously reduces visual acuity18–20 and contrast sensitivity,18,21 which may be sufficient to eliminate the diplopic image. The authors recommend that patients with CPR-type diplopia undergo at least an in-office trial of Fresnel prism, because for some this form of treatment may result in relief of diplopia.

  • Role of botulinum toxin A in treatment of intractable diplopia

    2017, Journal of AAPOS
    Citation Excerpt :

    A successful outcome was also reported with BTXA injection in a single case with acquired loss of fusion related to head trauma.9 Previous studies have demonstrated the negative effect of prisms on quality of vision that is more profound with Fresnel prisms compared to conventional prisms.10,11 The patient who wears 20Δ of prisms is expected to have 4 lines decrease in logMAR visual acuity with Fresnel prisms and 2 lines of decrease with conventional prisms.10

View all citing articles on Scopus

Study conducted at Altnagelvin Area Hospital, Londonderry, UK.

View full text