**2. Normal conjunctiva**

The conjunctiva is composed of two layers: the epithelium and stroma. The epithelium consists of well-organized cell layers in both stratified squamous and columnar types. The stroma is a connective tissue of fibrous and vascular elements in a less organized disposition.

All these anatomy concepts have found a great correspondence in the OCT imaging, so that the aspect of the conjunctiva in the OCT image presents typical features as shown in several reports [5–10]. The use of ASOCT on the normal conjunctiva is a complete and useful tool since the OCT imaging already provides a detailed representation of healthy limbus, sclera and conjunctiva. These studies were mainly focused on evaluating the qualitative (the complete visualization of the anatomy) and quantitative (the thickness of the different stratus) aspects of this layer. The normal OCT appearance is shown in **Figure 1**, where it is possible to recognize a small hyporeflective zone (epithelium) on the top resting on a greater hyperreflective area (stroma and Tenon capsule). Differentiating among the various layers is easy thanks to the different brightness OCT features. The epithelium, consisting of well-aligned cell layers, results as hyporeflective part, because of the less scattering of the incident light from OCT.

The OCT image of the stroma is characterized by an higher brightness signal because of its different composition up above described: so this part of the tissue highly scatters the OCT incident light, thus it appears hyperreflective and clearly visible beneath the conjunctival epithelium.

The conjunctival stromal OCT characteristic is quite different from the corneal stroma, as reported in previous studies [9]: the superficial and deeper layers of the stroma are composed by an adenoid layer containing lymphocytes and mast cells laying on a fibrous layer which produces an increase in reflectivity.

#### **Figure 1.**

*Conjunctival OCT in a normal subject: the multistratified cylinder epithelium appears as a hyporeflective area, laid on a dense, hyperreflective connective layer. The lower reflective Tenon capsule is separated by a visible demarcation.*

**51**

*OCT Applications in Conjunctival Disease DOI: http://dx.doi.org/10.5772/intechopen.87162*

health (edematous or thinning pathologies).

published by Read et al. [9].

249 ± 59 μm) (*p* < 0.001).

**3. The use of oct in glaucoma**

or the wall thickness [15, 16].

validated use of the anterior OCT [6, 8, 13].

about the wall and the internal architecture of the bleb.

epithelial thickness was 44.9 ± 3.4 μm in 13 healthy subjects.

The author demonstrated some interesting features:

thickness (mean 364 ± 122 μm) at the 4 mm location.

be about 240 (ranging from 140 to 304) in a report of 2013 [12].

The underlying Tenon capsule has a high reflectivity similar to the conjunctival stroma in the OCT image. The distinction of these two layers is not always recognizable, possibly depending on the relationship between the stroma and the tenon: a clingy apposition near the limbus, for instance, makes the differentiation hard [7]. Thickness has been the most quantitative feature which has been studied: a detection of its variation could be an important sign of conjunctival

In their study, [7] Feng and Simpson reported the mean bulbar conjunctiva

Another study reported the epithelial thickness being 42.0 ± 7.5 with a slight reduction in the group with a higher age [11], while also the stroma was measured to

A key concept is that significant variations in thickness may be found, mainly depending on the measurement locations (nasal, inferior, temporal or superior conjunctiva). These findings are consistent with the conjunctiva's anatomical characteristics: it is known that the stroma thickens in the fornix and thins at the limbus, but also differences in the different meridian have been shown in one report

• On average, the conjunctiva was significantly thicker in the nasal meridian (270 ± 90 μm) compared to the temporal meridian (mean thickness

• The conjunctiva exhibited its minimum thickness at the scleral spur location (0 mm) for both the temporal (mean 218 ± 55 μm) and nasal meridians (mean 223 ± 40 μm); however, the pattern of change in thickness away from the scleral spur differed between the two meridians. For the temporal meridian, the conjunctiva increased to its maximum thickness at the 1 mm location (mean 267 ± 59 μm), whereas the nasal meridian exhibited its maximum

• The conjunctival thickness measures also showed some significant changes with age, reducing in thickness from childhood into early adulthood. These changes are reasonable if we consider histological studies demonstrating that

The evaluation of the postoperative effectiveness of glaucoma surgery is a well

Reports in literature show that there are a lot of aspects of the OCT conjunctival appearance which can be used to assess the functionality of the blebs: the internal aspect (diffuse or flat) [14], the internal bleb reflectivity (low reflectivity or high)

The anterior OCT allows a detailed representation of the bleb architecture, giving information of the shape and functionality of a postsurgical bleb. Moreover, with ASOCT it is possible to observe if a bleb is functioning well and to know details

There is also another interesting use described in literature, described by Mastropasqua et al.: the authors stated that the application of ASOCT for studying bleb modifications before and after bulbar massage is useful as it is possible to observe an increase of the bleb-wall thickness, intraepithelial microcysts, and the

the mucous layer (goblet cell density) reduces in early adulthood.

#### *OCT Applications in Conjunctival Disease DOI: http://dx.doi.org/10.5772/intechopen.87162*

*A Practical Guide to Clinical Application of OCT in Ophthalmology*

The conjunctiva is composed of two layers: the epithelium and stroma. The epithelium consists of well-organized cell layers in both stratified squamous and columnar types. The stroma is a connective tissue of fibrous and vascular elements

All these anatomy concepts have found a great correspondence in the OCT imaging, so that the aspect of the conjunctiva in the OCT image presents typical features as shown in several reports [5–10]. The use of ASOCT on the normal conjunctiva is a complete and useful tool since the OCT imaging already provides a detailed representation of healthy limbus, sclera and conjunctiva. These studies were mainly focused on evaluating the qualitative (the complete visualization of the anatomy) and quantitative (the thickness of the different stratus) aspects of this layer. The normal OCT appearance is shown in **Figure 1**, where it is possible to recognize a small hyporeflective zone (epithelium) on the top resting on a greater hyperreflective area (stroma and Tenon capsule). Differentiating among the various layers is easy thanks to the different brightness OCT features. The epithelium, consisting of well-aligned cell layers, results as hyporeflective part, because of the less scattering of the incident light from OCT. The OCT image of the stroma is characterized by an higher brightness signal because of its different composition up above described: so this part of the tissue highly scatters the OCT incident light, thus it appears hyperreflective and clearly

The conjunctival stromal OCT characteristic is quite different from the corneal stroma, as reported in previous studies [9]: the superficial and deeper layers of the stroma are composed by an adenoid layer containing lymphocytes and mast cells

*Conjunctival OCT in a normal subject: the multistratified cylinder epithelium appears as a hyporeflective area, laid on a dense, hyperreflective connective layer. The lower reflective Tenon capsule is separated by a* 

laying on a fibrous layer which produces an increase in reflectivity.

**2. Normal conjunctiva**

in a less organized disposition.

visible beneath the conjunctival epithelium.

**50**

**Figure 1.**

*visible demarcation.*

The underlying Tenon capsule has a high reflectivity similar to the conjunctival stroma in the OCT image. The distinction of these two layers is not always recognizable, possibly depending on the relationship between the stroma and the tenon: a clingy apposition near the limbus, for instance, makes the differentiation hard [7]. Thickness has been the most quantitative feature which has been studied: a detection of its variation could be an important sign of conjunctival health (edematous or thinning pathologies).

In their study, [7] Feng and Simpson reported the mean bulbar conjunctiva epithelial thickness was 44.9 ± 3.4 μm in 13 healthy subjects.

Another study reported the epithelial thickness being 42.0 ± 7.5 with a slight reduction in the group with a higher age [11], while also the stroma was measured to be about 240 (ranging from 140 to 304) in a report of 2013 [12].

A key concept is that significant variations in thickness may be found, mainly depending on the measurement locations (nasal, inferior, temporal or superior conjunctiva). These findings are consistent with the conjunctiva's anatomical characteristics: it is known that the stroma thickens in the fornix and thins at the limbus, but also differences in the different meridian have been shown in one report published by Read et al. [9].

The author demonstrated some interesting features:

