Determining the Location of the Fovea Centralis Via En-Face SLO and Cross-Sectional OCT Imaging in Patients Without Retinal Pathology

Evaluation of post-operative foveal location and microstructural changes after pars plana vitrectomy for rhegmatogenous retinal detachment using enhanced-depth imaging optical coherence tomography

BACKGROUND

Patients who had successful rhegmatogenous retinal detachment (RRD) surgery often complained of metamorphopsia due to postoperative fovea displacement and alteration of the foveal microstructure. The papillo-foveal distance (PFD) is correlated bilaterally. Therefore, PFD from the fellow healthy eye could be used to determine the change of foveal position in eyes with successful RRD repair. Ultra-high-resolution optical coherence tomography (UHR-OCT) could explain incomplete visual recovery by demonstrating foveal misalignment and changes in foveal microstructure. The rationale of the study is to assess the changes in the foveal location and microstructural layers after successful retinal reattachment and correlate them with visual dysfunction.

PATIENTS AND METHODS

A prospective interventional cross-sectional controlled study included patients who had successful retinal reattachment and complained of defective vision or metamorphopsia. The primary outcome measure is to evaluate the post-operative foveal location. The secondary outcome measures are the assessment of metamorphopsia, the evaluation of the foveal microstructural changes, and the correlation between foveal shift, metamorphopsia, foveal microstructure, and visual function. We used a standard Amsler chart to detect subjective metamorphopsia and a modified Amsler chart to quantify metamorphopsia. We used the enhanced-depth imaging optical coherence tomography (EDI-OCT) to detect changes in PFD and the foveal microstructure. p < 0.05.

RESULTS

The study included 50 study eyes and 50 control eyes. The male gender constituted 70%. The mean age was 53 years. The mean baseline BCVA was 0.001. The incidence of foveal displacement was 70%. Disorganized retinal inner layers (DRIL) occurred in 56% of eyes, and disorganized retinal outer layers (DROL) occurred in 72% of eyes. The mean postoperative BCVA was 0.3. The subjective metamorphopsia was mild in 39%, moderate in 24%, severe in 33%, and very severe in 3% of eyes. The mean quantitative metamorphopsia was 587 mm. PVR correlated significantly with the foveal shift. DROL correlated significantly with subjective metamorphopsia. There was a statistically significant difference between subjective metamorphopsia and quantitative metamorphopsia.

CONCLUSION

Foveal displacement and metamorphopsia after successful retinal reattachment pose significant morbidity. UHR-OCT is pivotal in evaluating the anatomical outcome after successful retinal re-attachment surgery and its relation to visual function.

A New Vessel-Based Method to Estimate Automatically the Position of the Nonfunctional Fovea on Altered Retinography From Maculopathies

Purpose

The purpose of this study was to validate a new automated method to locate the fovea on normal and pathological fundus images. Compared to the normative anatomic measures (NAMs), our vessel-based fovea localization (VBFL) approach relies on the retina's vessel structure to make predictions.

Methods

The spatial relationship between the fovea location and vessel characteristics is learnt from healthy fundus images and then used to predict fovea location in new images. We evaluate the VBFL method on three categories of fundus images: healthy images acquired with different head orientations and fixation locations, healthy images with simulated macular lesions, and pathological images from age-related macular degeneration (AMD).

Results

For healthy images taken with the head tilted to the side, the NAM estimation error is significantly multiplied by 4, whereas VBFL yields no significant increase, representing a 73% reduction in prediction error. With simulated lesions, VBFL performance decreases significantly as lesion size increases and remains better than NAM until lesion size reaches 200 degrees2. For pathological images, average prediction error was 2.8 degrees, with 64% of the images yielding an error of 2.5 degrees or less. VBFL was not robust for images showing darker regions and/or incomplete representation of the optic disk.

Conclusions

The vascular structure provides enough information to precisely locate the fovea in fundus images in a way that is robust to head tilt, eccentric fixation location, missing vessels, and actual macular lesions.

Translational Relevance

The VBFL method should allow researchers and clinicians to assess automatically the eccentricity of a newly developed area of fixation in fundus images with macular lesions.