A Prediction Method of Visual Field Sensitivity Using Fundus Autofluorescence Images in Patients With Retinitis Pigmentosa

Abstract

Purpose: The purpose of this study was to investigate the association between fundus autofluorescence (FAF) and visual field (VF) sensitivities in eyes with retinitis pigmentosa (RP). We also investigated the model we developed to predict VF sensitivity using the FAF ring and its prediction accuracy.

Methods: The training dataset consisted of 51 eyes of 28 patients, and the testing dataset consisted of 42 eyes of 25 patients with RP. VF and FAF measurements were conducted using the Humphrey Field Analyzer (HFA) 10-2 test and Optos. The HFA 10-2 test was divided into three sectors according to the association with the FAF (IN, ON, and OUT). Moreover, concentric curves were drawn at 1-degree intervals outside the FAF ring and OUT was divided into six sectors (from OUT1 to OUT6 toward the periphery). Finally, the total deviation (TD) value was predicted using age and visual acuity (VA) in the whole field, and each of the eight sectors was compared.

Results: The TD value decreased significantly from IN, ON, and then toward OUT6. The absolute prediction error with the FAF ring (average, 7.6 dB) was significantly smaller than that without the FAF ring (average, 8.7 dB). The absolute prediction error with the FAF ring was significantly smaller in the central areas (IN, 4.4 dB and ON, 5.3 dB) than those in the peripheral areas (OUT1-6, 6.8-9.1 dB).

Conclusions: VF sensitivity decreases in association with the FAF ring. We developed a model to predict 10-2 VF sensitivity values using the FAF ring, which enabled us to predict 10-2 TD values.

Figure 1.

Sectorization of the HFA 10-2 test according to the FAF ring. (A) Each image output was automatically corrected for 3- to 2-dimensional projection errors. (B) The 10 × 10 degrees area was binarized using the Niblack's local thresholding technique. (C) Then, the HFA 10-2 test was superimposed and sectorized according to the FAF ring. FAF, fluorescence autofluorescence; HFA, Humphrey Field Analyzer; IN: inside the FAF ring (IN), ON: on the FAF ring (ON), OUT1: between the FAF outer ring and 1 degree outside the FAF outer ring, OUT2: between 1 and 2 degrees outside the FAF outer ring, OUT3: between 2 and 3 degrees outside the FAF outer ring, OUT4: between 3 and 4 degrees outside the FAF outer ring, OUT5: between 4 and 5 degrees outside the FAF outer ring, and OUT6: 5 degrees or more outside the FAF outer ring.

Figure 2.

Examples of discontinuous and irregular-shaped AF rings. A discontinuous FAF ring was observed in four eyes (A) and an irregular-shaped FAF ring was seen in 12 eyes (B). These eyes were excluded from the current analysis. BCVA, best corrected visual acuity; FAF, fluorescence autofluorescence.

Figure 3.

The relationship between VF sensitivity and the logMAR VA. There was a significant association between foveal sensitivity and the logMAR VA (A). A significant relationship was also observed between the MD value and the logMAR VA (B). VF, visual field; MD, mean deviation; VA, visual acuity.

Figure 4.

The comparison of the TD values in each sector. There was a significant difference in all the comparisons across the sectors (P < 0.05, Tukey's test and linear mixed model). FAF, fluorescence autofluorescence; IN, inside the FAF ring; ON, on the FAF ring; OUT1, between the FAF outer ring and 1 degree outside the FAF outer ring; OUT2, between 1 and 2 degrees outside the FAF outer ring; OUT3, between 2 and 3 degrees outside the FAF outer ring; OUT4, between 3 and 4 degrees outside the FAF outer ring; OUT5, between 4 and 5 degrees outside the FAF outer ring; OUT6, 5 degrees or more outside the FAF outer ring; TD, total deviation.

Figure 5.

The comparison between the absolute prediction error with (7.6 ± 5.6 dB) and without (8.7 ± 15.4 dB) the FAF ring. There was a significant difference between the two values. FAF, fluorescence autofluorescence.

Figure 6.

Absolute prediction error values with the FAF ring (binarization method) prediction across eight sectors. The IN and ON values were significantly smaller than those at all six OUT sectors. The values of OUT1 was significantly smaller than those of OUT2, OUT3, OUT4, and OUT5. FAF, fluorescence autofluorescence; IN, inside the FAF ring; ON, on the FAF ring; OUT1, between the FAF outer ring and 1 degree outside the FAF outer ring; OUT2, between 1 and 2 degrees outside the FAF outer ring; OUT3, between 2 and 3 degrees outside the FAF outer ring; OUT4, between 3 and 4 degrees outside the FAF outer ring; OUT5, between 4 and 5 degrees outside the FAF outer ring; OUT6, 5 degrees or more outside the FAF outer ring.

Figure 7.

Representative OCT image in case with large prediction errors. There were 30 test points where the absolute prediction error was larger than 20 dB. The accompanied OCT image (horizontal scan, left eye) suggested that the ellipsoid zone was disrupted in the IN area and remained in the OUT areas. The region between blue and yellow arrows is ON area, whereas that between blue arrows is IN area. FAF, fluorescence autofluorescence; IN, inside the FAF ring; OCT, optical coherence tomography; ON, on the FAF ring.