The macular pigment optical density spatial profile and increasing age

Deep learning-based correction of cataract-induced influence on macular pigment optical density measurement by autofluorescence spectroscopy

PURPOSE

Measurements of macular pigment optical density (MPOD) using the autofluorescence spectroscopy yield underestimations of actual values in eyes with cataracts. Previously, we proposed a correction method for this error using deep learning (DL); however, the correction performance was validated through internal cross-validation. This cross-sectional study aimed to validate this approach using an external validation dataset.

METHODS

MPODs at 0.25°, 0.5°, 1°, and 2° eccentricities and macular pigment optical volume (MPOV) within 9° eccentricity were measured using SPECTRALIS (Heidelberg Engineering, Heidelberg, Germany) in 197 (training dataset inherited from our previous study) and 157 eyes (validating dataset) before and after cataract surgery. A DL model was trained to predict the corrected value from the pre-operative value using the training dataset, and we measured the discrepancy between the corrected value and the actual postoperative value. Subsequently, the prediction performance was validated using a validation dataset.

RESULTS

Using the validation dataset, the mean absolute values of errors for MPOD and MPOV corrected using DL ranged from 8.2 to 12.4%, which were lower than values with no correction (P < 0.001, linear mixed model with Tukey's test). The error depended on the autofluorescence image quality used to calculate MPOD. The mean errors in high and moderate quality images ranged from 6.0 to 11.4%, which were lower than those of poor quality images.

CONCLUSION

The usefulness of the DL correction method was validated. Deep learning reduced the error for a relatively good autofluorescence image quality. Poor-quality images were not corrected.

Correction for the Influence of Cataract on Macular Pigment Measurement by Autofluorescence Technique Using Deep Learning

Purpose

Measurements of macular pigment optical density (MPOD) by the autofluorescence technique yield underestimations of actual values in eyes with cataract. We applied deep learning (DL) to correct this error.

Subjects and Methods

MPOD was measured by SPECTRALIS (Heidelberg Engineering, Heidelberg, Germany) in 197 eyes before and after cataract surgery. The nominal MPOD values (= preoperative value) were corrected by three methods: the regression equation (RE) method, subjective classification (SC) method (described in our previous study), and DL method. The errors between the corrected and true values (= postoperative value) were calculated for local MPODs at 0.25°, 0.5°, 1°, and 2° eccentricities and macular pigment optical volume (MPOV) within 9° eccentricity.

Results

The mean error for MPODs at four eccentricities was 32% without any correction, 15% with correction by RE, 16% with correction by SC, and 14% with correction by DL. The mean error for MPOV was 21% without correction and 14%, 10%, and 10%, respectively, with correction by the same methods. The errors with any correction were significantly lower than those without correction (P < 0.001, linear mixed model with Tukey's test). The errors with DL correction were significantly lower than those with RE correction in MPOD at 1° eccentricity and MPOV (P < 0.001) and were equivalent to those with SC correction.

Conclusions

The objective method using DL was useful to correct MPOD values measured in aged people.

Translational Relevance

MPOD can be obtained with small errors in eyes with cataract using DL.

Macular Pigment and Visual Function in Patients With Glaucoma: The San Diego Macular Pigment Study

Purpose

Although recent studies have shown that macular pigment (MP) is significantly lower in glaucoma patients, this relationship merits further investigation.

Methods

This cross-sectional study included 85 glaucoma patients and 22 controls. All subjects had standard automated perimetry (SAP) and retinal nerve fiber layer (RNFL) thickness measurements. Intake of lutein (L) and zeaxanthin (Z) was estimated using a novel dietary screener. The Heidelberg Spectralis dual-wavelength autofluorescence (AF) technology was employed to study the relationship between MP and glaucoma. The association between MP volume and glaucoma was investigated using linear regression models accounting for potential confounding factors.

Results

Glaucoma patients had significantly worse SAP mean deviation (MD) and lower RNFL thickness in the study eye compared to control subjects (P < 0.001 for both). MP (volume) was comparable between groups (P = 0.436). In the univariable model, diagnosis of glaucoma was not associated with MP volume (R² = 1.22%; P = 0.257). Dietary intake of L and Z was positively and significantly related to MP in the univariable (P = 0.022) and multivariable (P = 0.020) models.

Conclusions

These results challenge previous studies that reported that glaucoma is associated with low MP. Dietary habits were found to be the main predictor of MP in this sample. Further research is merited to better understand the relationship between glaucoma, MP, and visual performance in these patients.

Haidinger's brushes elicited at varying degrees of polarization rapidly and easily assesses total macular pigmentation

Macular pigments (MPs), by absorbing potentially toxic short-wavelength (400-500 nm) visible light, provide protection against photo-chemical damage thought to be relevant in the pathogenesis of age-related macular degeneration (AMD). A method of screening for low levels of MPs could be part of a prevention strategy for helping people to delay the onset of AMD. We introduce a new method for assessing MP density that takes advantage of the polarization-dependent absorption of blue light by MPs, which results in the entoptic phenomenon called Haidinger's brushes (HB). Subjects were asked to identify the direction of rotation of HB when presented with a circular stimulus illuminated with an even intensity of polarized white light in which the electric field vector was rotating either clockwise or anti-clockwise. By reducing the degree of polarization of the stimulus light, a threshold for perceiving HB (degree of polarization threshold) was determined and correlated (r²=0.66) to macular pigment optical density assessed using dual-wavelength fundus autofluoresence. The speed and ease of measurement of degree of polarization threshold makes it well suited for large-scale screening of macular pigmentation.

Grade of Cataract and Its Influence on Measurement of Macular Pigment Optical Density Using Autofluorescence Imaging

Purpose

To evaluate the influence of cataracts on measuring macular pigment optical density (MPOD) using a dual-wavelength confocal scanning autofluorescence imaging technique and to establish methods to compensate for the influence of cataracts.

Methods

This prospective case series comprised 100 eyes that underwent cataract surgery. Cataracts were graded based on the World Health Organization classification. MPOD levels were measured with the MPOD module of the Spectralis MultiColor instrument (Spectralis-MP), pre- and postoperatively. We investigated the relationship between change in MPOD values and age, cataract grade, and quality of autofluorescence images. Local MPOD levels were evaluated for four strategically chosen eccentricities within the macular region, and the total MPOD volume was evaluated within 8.98° eccentricity from the center.

Results

MPOD levels could be obtained in 67 eyes before surgery. Local and volume MPOD levels were higher postoperatively relative to preoperatively in all eyes. The mean ratio of local MPOD levels after and before surgery (correction factor, CF) ranged from 1.42 to 1.77, with larger CFs required for eccentricities closer to the foveal center. The CF for the MPOD volume was 1.31. Age, grade of nuclear cataract (NUC), posterior subcapsular opacity, and image quality index (IQI) significantly contributed to CFs. For example, regression equation for CF at 0.23° = 0.17 + 0.16 × IQI + 0.29 × NUC grade + 0.01 × age (P < 0.001).

Conclusions

Cataracts affected MPOD measurements with the Spectralis-MP, but corrected MPOD results could be obtained via regression equations.

Investigation of the relationship between macular pigment levels and rod-mediated dark adaptation in intermediate age-related macular degeneration

BACKGROUND

It has been shown that rod-mediated dark adaptation is significantly delayed in ageing, a change which is exacerbated in age-related macular degeneration (AMD). Levels of lutein and zeaxanthin, the two main constituents of macular pigment have been found in rod outer segments, indicating that the macular pigment may have an influence on rod-mediated dark adaptation. The aim of this study was to determine if rod-mediated dark adaptation is associated with central macular pigment levels in individuals with intermediate stage AMD.

METHODS

A cross-sectional observational study included individuals with acuity better than 6/15 Snellen and intermediate stage AMD based on graded fundus photographs using an internationally accepted grading scale. Rod-mediated dark adaptation was assessed at five degrees eccentricity in the superior retina (inferior visual field) using the rod intercept time measure from the MacuLogix AdaptDx. Macular pigment optical density was measured at 0.5 degrees eccentricity using a heterochromatic flicker photometry-based method.

RESULTS

Twenty-seven individuals (mean age 76.7 years) with intermediate stage AMD and 23 age-matched normal controls (mean age 74.0 years) were recruited. Rod-mediated dark adaptation was significantly delayed in intermediate stage AMD compared with healthy controls (32.9 minutes versus 10.7 minutes, p < 0.01). There was no statistically significant correlation between the rod intercept time and the level of macular pigment in those with intermediate AMD (r = -0.04, p = 0.85).

CONCLUSION

The results did not support the hypothesis that higher macular pigment is associated with improved rod-mediated performance or that higher levels of macular pigment protect rod-mediated function in intermediate AMD.

Reliability of a commercially available heterochromatic flicker photometer, the MPS2, for measuring the macular pigment optical density of a Japanese population

PURPOSE

The macular pigment optical density (MPOD) of a Japanese population was measured using a commercially based heterochromatic flicker photometer, the Macular Pigment Screener (MPS2). The objective of the study was to evaluate the accuracy and test-retest reliability of the MPS2 in Asian pigmented eyes.

STUDY DESIGN

Experimental study to validate the medical instrument in humans.

METHODS

Twenty-four healthy Japanese participants with no systemic or eye diseases (men: 13, women: 11; mean [SD] age 38.6 [10.9 years]) were included. The concordance of the MPOD, obtained using the MPS2 and Macular Metrics II (MM2), and the test-retest reliability were examined.

RESULTS

Determination of the MPOD was unsuccessful in 1 participant; thus, the MPOD of 23 participants was analyzed. The mean (SD) MPOD measured with the detail-mode of the MPS2 was 0.63 (0.18) and with that of the MM2, it was 0.72 (0.23). The former was significantly lower than the latter (P = .003, paired t test). The MPOD measured with the MPS2 and the MM2 showed good concordance (r = 0.79, P < .001, Pearson product moment correlation). Bland-Altman analyses showed no systematic errors between the MPS2 and the MM2. The intraclass correlation coefficient over 5 measurement times with the detail-mode of the MPS2 was 0.80, and the mean coefficient of variation was 9.4%.

CONCLUSION

The high concordance with the MM2 and good test-retest reliability found by this study suggest that the MPS2 is acceptable for use in a Japanese population. However, the mean MPOD yielded by the MPS2 was significantly lower than that yielded by the MM2. Therefore, the MPS2 and MM2 are not interchangeable in a single study.

Lutein and Zeaxanthin Isomers in Eye Health and Disease

Current evidence suggests lutein and its isomers play important roles in ocular development in utero and throughout the life span, in vision performance in young and later adulthood, and in lowering risk for the development of common age-related eye diseases in older age. These xanthophyll (oxygen-containing) carotenoids are found in a wide variety of vegetables and fruits, and they are present in especially high concentrations in leafy green vegetables. Additionally, egg yolks and human milk appear to be bioavailable sources. The prevalence of lutein, zeaxanthin, and meso-zeaxanthin in supplements is increasing. Setting optimal and safe ranges of intake requires additional research, particularly in pregnant and lactating women. Accumulating evidence about variable interindividual response to dietary intake of these carotenoids, based on genetic or metabolic influences, suggests that there may be subgroups that benefit from higher levels of intake and/or alternate strategies to improve lutein and zeaxanthin status.