Medicine (Baltimore). 2016 Aug;95(35):e4234. doi: 10.1097/MD.0000000000004234.

Using optical coherence tomography to assess the role of age and region in corneal epithelium and palisades of vogt.

Lin HC, Tew TB, Hsieh YT, Lin SY, Chang HW, Hu FR, Chen WL.
Department of Ophthalmology, National Taiwan University Hospital, Taipei bDepartment of Ophthalmology, National Taiwan University Hospital, Hsinchu Branch, Hsinchu cDepartment of Ophthalmology, Cathay General Hospital dCenter of Corneal Tissue Engineering and Stem Cell Biology, National Taiwan University Hospital, Taipei, Taiwan.

 

Abstract
Using spectral-domain optical coherence tomography (OCT) to observe the morphology and epithelial thickness (ET) of the palisades of Vogt (POV), and to evaluate the role of age and region on these structures.One hundred twelve eyes of 112 healthy subjects were enrolled and divided into 4 groups: A (0-19), B (20-39), C (40-59), and D (≥60 years old). RTvue-100 OCT was applied on the cornea and the limbus. The morphology of the subepithelial stroma underneath the epithelium of POV was classified into typical and atypical types. Maximum ET of POV was measured manually from OCT images.The positive rate of typical POV in superior, nasal, temporal, and inferior limbus was: Group A: 100%, 69.2%, 65.4%, 100%; Group B: 100%, 73.5%, 61.8%, 94.1%; Group C: 95.8%, 41.7%, 37.5%, 83.3%; Group D: 67.9%, 0%, 3.6%, 25%, showing a significant decreasing tendency with age. The maximum ET of POV in superior, nasal, temporal, and inferior limbus was: Group A: 103.5 ± 10.1 um, 89.2 ± 9.7 um, 87.9 ± 13.6 um, 104.7 ± 14.1 um; Group B: 111.4 ± 15.8 um, 85.3 ± 9.9 um, 88.2 ± 8.6 um, 112.6 ± 19.7 um; Group C: 116.4 ± 16.4 um, 82.8 ± 11.6 um, 87.0 ± 11.6 um, 120.0 ± 25.6 um; Group D: 96.3 ± 17.9 um, 73.8 ± 15.9 um, 79.2 ± 16.7 um, 87.4 ± 18.5 um. Age-dependent change was observed. In general, the maximum ET of POV in superior/inferior quadrants was thicker than the other 2 quadrants.Spectral-domain OCT is a useful tool to observe the limbal microstructure and provide invaluable information. Aging and anatomic regions had significant effects on the microstructure of these areas.
PMID: 27583846

 

Supplement

The palisades of Vogt (POV) is a set of radially oriented fibrovascular ridges located in the area of the limbus (Fig. 1A). The POV provides a niche environment for limbal stem cells, which maintain corneal epithelial homeostasis and clarity. Understanding the morphology of the POV is important for the treatment of limbal damage and cell therapies targeting at restoring impaired functions of limbal stem cells.

 

 

Figure 1. Typical healthy POV in most young adults in this study.

(A)Anatomy of the cornea-sclera junction (CjE=the conjunctival epithelium, CjS=the conjunctival stroma, CnE=corneal epithelium layer, CnS=the corneal stroma, ES=the episclera, LS=the limbal stroma, POV=the epithelium of POV, Ves=the limbal vessels.)

(B) Typical pattern of PO

(C) Picture contrast increased. White arrows highlight the sharp tapering tip of subepithelial stroma pointing to the corneal-limbal junction.

 

Many factors influence the size, shape and configuration of POV over time. This study used optical coherence tomography (OCT) to investigate the effects of aging on the POV, and the differences in POV morphology and maximal epithelial thickness (ET) at 4 different limbal locations (“superior”, “inferior”, ”nasal” and “temporal” quadrants).

OCT is a noninvasive imaging device that can take pictures of the epithelial layer of the eye. Spectral domain OCT was chosen over regular time-domain OCT for it provides higher resolution observation of the epithelial layer on ocular surface with proven reliability. The spectral domain OCT used was equipped with a corneal-anterior module long lens adapter at low magnification to look at a sizable area of the limbus and observe POV morphology. POV patterns in 112 patients were evaluated by OCT and classified into typical and atypical types (Fig. 2). The typical type is defined as having the sharp tapering tip of the subepithelial stroma pointing to the corneal-limbal junction with the maximum POV epithelial thickness (ET) at least 1.5 times thicker than the corresponding central corneal epithelial thickness (CET) (Fig.1B-C). Percentage of typical POV observed in each region was used to calculate the positive rate of typical POV.

 

 

Figure 2. Typical (A) vs Atypical (B-D) POV patterns

1x=original images obtained from OCT, showing the almost full thickness of the corneo-scleral junctions. 2x= 2x enlargement of the original images, which clearly demonstrated the epithelial morphology of POV.

 

Our study showed that the superior and inferior quadrants have thicker maximum ET and higher positive rate of typical POV than the nasal and temporal quadrants in all age groups. In superior and inferior quadrants, maximum ET in patients increased from patients below 19 to patients between 20 and 59 years old, and decreased significantly in patients over the age of 60. On the other hand, in nasal and temporal quadrants, maximum ET decreased constantly with age. To better visualize the difference in POV morphology across age groups, 2 case presentations are illustrated below. Figure 3 shows representative images of POV in both eyes of a healthy adult aged 30 and Figure 4 shows representative images of a healthy adult aged 82. POV morphology (typical vs atypical patterns) and maximum ET were determined from OCT image, and described in detail.

 

 

Figure 3. Epithelium and POV pattern at 4 regions in healthy 30 year-old adult.

Maximum ET of superior and inferior POV is thicker than the nasal and temporal POV in both eyes (OD=left, OS=right). The typical sharp triangular shape of subepithelial stroma is found only in superior and inferior quadrants instead of nasal and temporal quadrants. C=cornea, S=sclera

 

 

Figure 4. Epithelium and POV pattern at 4 regions in healthy 82 year-old adult.

The typical pattern of POV was only found in the superior quadrant of the right eye. The epithelium was wavy in the superior quadrant in the left eye. There were pingueculae at the nasal limbus in both eyes, which made the maximum ET of POV even thinner than the peripheral cornea. In the temporal and inferior quadrants of both eyes, the POV lost the typical subepithelial stroma pattern.

 

The regional difference in age-related maximum ET patterns observed could be attributed to age-related decrease of melanocytes, which is more severe in nasal and temporal regions than the superior and inferior quadrants. Other possible factors contributing to the regional difference in POV include age-related tissue growth, varying amount of accumulated damage from eyelid blinking and sunlight exposure.

In conclusion, the microstructure of these limbal regions varies with age of subject and location of the eye.