Two-Photon Microperimetry with controlled media opacity- Quantifying retinal sensitivity using infrared pulsed laser stimulation

Abstract

Purpose : Retinal function has traditionally been assessed by ophthalmic devices that employ visible light (400-720 nm). However, near infra-red (IR 700 to 1100 nm) light is attenuated less by human tissues than visible light, especially in disease states. Disease states like cataract and corneal opacity attenuate visible light requiring surgery to rehabilitate vision. Therefore, we hypothesize that two-photon microperimetry (2PM) using IR light will be less affected by transmission media/filters compared to other conventional visual function tests, such as Cone Contrast Test (CCT) and Microperimtetry-3 (MP3).

Methods : A total of 6 subjects were recruited for this study. All underwent the following tests: CCT, MP3, and 2PM. Each test was performed 9 separate times using best corrected visual acuity (BCVA) under the following conditions: best correction/naked eyes without dilation, best correction/naked eyes with dilation, red filter, green filter, blue filter, light brown filter, dark brown filter, polarized filter (0-degree rotation), and polarized filter (90-degree rotation). The optical spectral transmission was then determined for each filter condition. Results from 2PM were translated into decibels for analysis.
We calculated the mean sensitivity (decibels) for each test: 2PM-IR, 2PM-Vis, MP3. Standard deviation around each mean for each test was also calculated with the intent of identifying the amount of variability in test results depending on the media opacity (filter condition). A paired sample t test has been performed to test whether mydriasis will affect 2PM data.

Results : 2PM-IR with demonstrated variability ranges depending on media opacity of -62.58--56.57 dB, which was much less variable compared to 2PM-Vis and MP3, ranging from 4.88-26.19 dB and 12.83-28.17 dB respectively. CCT, although not scored on dB scale and not a perimetry assay, demonstrated higher variability compared to visible perimetry (2PM-Vis, and MP3) and IR perimetry.
Mydriasis has a nominally positive effect on retinal sensitivity, however, a statistically insignificant effect on Infrared (p=0.06) and visible (p=0.29) stimulation.

Conclusions : 2PM-IR microperimetry is a retinal sensitivity assay that is nearly impervious to media opacity. Mydriasis does not statistically affect retinal sensitivity while performing 2PM tests.

This is a 2020 ARVO Annual Meeting abstract.