J Korean Ophthalmol Soc.  2008 May;49(5):763-770. 10.3341/jkos.2008.49.5.763.

Evaluation of Correlation Between OCT Findings and Delayed Visual Acuity Improvement After Macular Hole Surgery

• Kim JH
• Lee JE
• Oum BS

• KMID: 2211706
• DOI: http://doi.org/10.3341/jkos.2008.49.5.763

Abstract

PURPOSE: We evaluated the relationship between the delayed visual acuity (VA) improvement and retinal features, including in the photoreceptor layer, after a successful macular hole surgery using optical coherence tomography (OCT) images during long-term post-operative observation. The goal was to find the mechanism in delayed VA improvement.
METHODS
Postoperative OCT scans were analyzed in nine eyes of eight patients who underwent idiopathic macular hole surgery between June 2003 to June 2005. Horizontal and vertical OCT scans taken of the operated eyes immediately after absorption of intraocular gas and after VA improvement were exported to Adobe Photoshop 7.0. We measured changes in parameters of the central foveal thickness (central 1 mm area), photoreceptor layer thickness, relative reflectivity of photoreceptor to retinal pigment epithelium, and the defective area of photoreceptor layer.
RESULTS
The median visual acuity was determined to be 0.2 (range: 0.15~0.3) at the VA unimproved period and 0.5 (range: 0.3~1.0) at VA improved period. The mean central foveal thickness decreased from 221.3 micrometer (range: 155~265 micrometer) to 191.2 micrometer (range: 150~231 micrometer), as VA improved (p=0.007). The mean photoreceptor layer thickness increased from 15.2 micrometer (range: 4.2~27.6 micrometer) to 22.6 micrometer (range: 4.2~35.8 micrometer) as VA improved (p=0.032), and mean relative reflectivity of photoreceptor layer increased from 0.43 (range: 0.08~0.67) to 0.48 (range: 0.10~0.70), as VA improved (p=0.415). The defective area of photoreceptor layer decreased from 70% (range: 90~45%) to 27% (range: 8~5), as VA improved (p=0.001).
CONCLUSIONS
A decrease of the central foveal thickness and of photoreceptor layer defective signal, and an increase of photoreceptor layer thickness were observed on OCT during delayed vision improvement after a successful macular hole surgery. Improvement of macular edema and photoreceptor reorganization are suggested as important parts of the mechanism toward vision recovery.

Keyword

Delayed Gradual visual acuity (VA) improvement; Macular hole surgery; Optical Coherence Tomography (OCT)

MeSH Terms

Absorption
Eye
Humans
Macular Edema
Retinal Perforations
Retinal Pigment Epithelium
Retinaldehyde
Tomography, Optical Coherence
Vision, Ocular
Visual Acuity
Retinaldehyde

Figure

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  Figure 1. Central foveal thickness measurement. Automatically measured central foveal thickness in the OCT: Fast macular thickness map at the central 1000 µm area was regarded as central foveal thickness.

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  Figure 2. Processed images of an OCT raw file. (A) After the adjustment using a new scale, the full range of image brightness is used, minimizing information loss. (B) The junction between the photoreceptor layer and the retinal pigment epithelium is traced (green line). A 50 µm thick area above the junction is selected to measure reflectivity of the photoreceptor layer (between green and blue lines). A 50µm thick area bellow the junction is selected to measure reflectivity of the retinal pigment epithelium (between green and red lines). The average reflectivity of each area is obtained from the average brightness of the pixels in each area. The relative reflectivity of photoreceptor layer is calculated by dividing the reflectivity of photoreceptor layer by that of the retinal pigment epithelium. (C) The transition zone between inner and outer segments of the photoreceptors is enhanced as pure white pixels. An area including the transition zone and the low reflective pixels between the transition zone and the retinal pigment epithelium is selected. Average thickness of photoreceptor layer can be calculated by dividing the selected area by the width of the region of interest (1 mm). Defect of the photoreceptor layer is measured subjectively as a relative area of loss of the signal from the transition zone in the central 1 mm.

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  Figure 3. Case 1. Defect in the photoreceptor layer on optical coherence tomography decreased from 70% postoperative at 1 month (A) to 10% at postoperative 9 months after macular hole surgery (B). Visual acuity improved from 0.15 to 0.5. Although average thickness of the photoreceptor layer increased from 12.8 to 22.6 µm, actual thickening of the photoreceptor layer is not observed.

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  Figure 4. Case 6. (A) Two weeks after macular hole sugery, broad defect of the photoreceptor layer is noted on optical coherence tomography. Visual acuity was 0.25. (B) At postoperative 12 months, the defect is resolved and visual acuity improved to 1.0. Average thickness of the photoreceptor layer increased from 24.8 to 34.5 µm without actual thickening of the photoreceptor layer.

Reference

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