Terriens Marginal Degeneration: Symptoms, Types, Causes and Treatment

Terriens Marginal Degeneration (TMD) is a rare, slowly progressive disease that affects the peripheral cornea, leading to thinning, vascularization, and visual distortion. Although it is not as widely recognized as other corneal disorders, its impact on vision and eye health can be significant. This article offers a comprehensive exploration of TMD, including its symptoms, types, underlying causes, and modern treatment strategies—supported by up-to-date research.

Symptoms of Terriens Marginal Degeneration

Terriens Marginal Degeneration often presents subtly, making early identification a challenge. Most patients notice changes in their vision over time, while some remain asymptomatic until the disease has progressed. Recognizing these symptoms is crucial for timely diagnosis and intervention.

Symptom	Description	Frequency/Severity	Source
Blurred vision	Reduced visual clarity	Common, especially with progression	1 2 3
Astigmatism	Irregular corneal shape	Often high, progressive	1 2 3
Ocular discomfort	Mild irritation, dryness	Sometimes present, generally mild	2
Decreased acuity	Lower visual sharpness	Varies, can range from mild to severe	1 2 3
No pain/inflammation	Lack of redness or acute pain	Typical distinguishing feature	2

Table 1: Key Symptoms of Terriens Marginal Degeneration

Blurred Vision and Astigmatism

The most frequent complaint among TMD patients is blurred vision, often caused by increasing corneal astigmatism. As the peripheral cornea thins and changes shape, the regular curvature of the eye is disrupted, leading to distortion and blurring that cannot be easily corrected with standard glasses alone. In many cases, astigmatism can progress by 0.41 diopters per year, and some patients experience astigmatism as high as 10 diopters 2 3.

Ocular Discomfort and Surface Symptoms

Unlike many other peripheral corneal diseases, TMD is typically not associated with pain or significant inflammation. Some patients, however, may report mild ocular surface symptoms such as dryness or irritation, which are generally not severe 2.

Decreased Visual Acuity

While many patients maintain relatively good visual acuity in the early stages (median best-corrected visual acuity: 20/25), this can decline as the disease advances, particularly if high astigmatism develops or if corneal perforation occurs 2 3.

Absence of Acute Inflammation

One of the hallmark features that help distinguish TMD from similar diseases is the absence of acute inflammatory signs. There is typically no redness, ulceration, or significant pain in the affected area, setting TMD apart from conditions like Mooren ulcer 2.

Types of Terriens Marginal Degeneration

TMD does not always present in the same way. Variability in its progression, laterality, and severity has led to different classifications, which can affect prognosis and management.

Type	Main Feature	Typical Presentation	Source
Classic	Slow, peripheral thinning	Bilateral, superior cornea	2 3
Unilateral	Affects one eye	Less common, younger patients	2
Severe/Advanced	Marked thinning, risk of perforation	Extensive astigmatism, cavitation	4 7
Asymptomatic	No symptoms, subtle changes	Detected during routine exam	3

Table 2: Clinical Types of Terriens Marginal Degeneration

Classic Bilateral TMD

The most common form of TMD is bilateral, usually affecting both eyes, and most often the superior peripheral cornea. This type is progressive, with patients typically developing high astigmatism and peripheral thinning over time 2 3.

Unilateral and Early-Onset Variants

Although TMD is most often bilateral, unilateral cases have been documented, sometimes in younger patients. These cases may progress differently and are occasionally mistaken for other peripheral corneal disorders 2.

Severe/Advanced Disease

In advanced stages, TMD may involve extensive areas of the cornea (sometimes more than a quarter of its circumference), marked thinning (often below 150 μm), cavitation, and a much higher risk of complications such as perforation 4 7. These cases require more aggressive management.

Asymptomatic Cases

Some patients may show the classic signs of TMD—thinning, neovascularization, and furrowing—without significant astigmatism or visual complaints. These cases are often identified incidentally during routine eye exams 3.

Causes of Terriens Marginal Degeneration

While the exact cause of TMD remains unknown, research has highlighted several contributing factors and pathological findings. Understanding these can help clinicians distinguish TMD from related conditions and guide treatment.

Factor	Description	Evidence/Implication	Source
Degenerative	Non-inflammatory tissue breakdown	Main hypothesis	1 2
Inflammatory	Mild, subclinical inflammation	Possible minor role	1 2
Age/Sex	Middle-aged males more affected	Epidemiological trend	1 2
Histopathology	Vacuoles in corneal stroma	Diagnostic marker	1

Table 3: Proposed Causes and Pathology of TMD

Degenerative Mechanisms

Most evidence suggests that TMD is a degenerative disorder, characterized by the slow breakdown of peripheral corneal tissue. Unlike conditions such as Mooren ulcer, overt inflammation is usually absent 1 2. Degenerative changes result in stromal thinning, and the loss of structural integrity leads to characteristic furrowing.

Mild Inflammatory Component

Although TMD is generally non-inflammatory, some researchers have proposed that subclinical inflammation may contribute to disease progression. However, the lack of pain, redness, or ulceration makes inflammation a less prominent feature 1 2.

Demographics: Age and Sex

TMD is most frequently diagnosed in middle-aged men, though cases have been reported from adolescence through old age (15–86 years). The bilateral nature of most cases further supports a non-infectious, systemic predisposition rather than a purely local trigger 1 2.

Histopathological Findings

Microscopic examination often reveals numerous intracellular and extracellular vacuoles in the affected corneal stroma—considered a hallmark of TMD. These findings can help differentiate TMD from other causes of peripheral corneal thinning 1.

Treatment of Terriens Marginal Degeneration

Managing TMD requires an individualized approach, balancing conservative measures with advanced surgical interventions in severe cases. Early identification and regular monitoring are crucial for preserving vision and preventing complications.

Treatment	Method/Approach	Indication/Outcome	Source
Spectacles	Glasses for refractive error	Mild cases, early astigmatism	1 3
Rigid contact lenses	Gas-permeable or scleral lenses	Moderate astigmatism, irregular cornea	1
Collagen Cross-linking	UVA/riboflavin CXL	Arrest progression, early/moderate TMD	6
Lamellar keratoplasty	Partial or total corneal graft	Severe thinning, perforation risk	4 5 7
Ring keratoplasty	Corneoscleral ring-shaped graft	Advanced, extensive TMD	4

Table 4: Therapeutic Approaches for TMD

Conservative Management

In mild or early cases of TMD, correcting refractive errors with spectacles can restore excellent visual acuity, especially if astigmatism is not severe 1 3. For patients with irregular corneal surfaces or higher levels of astigmatism, rigid gas-permeable or scleral contact lenses provide better vision by masking corneal irregularity 1.

Corneal Collagen Cross-Linking (CXL)

CXL is an emerging treatment option for TMD. In select cases, especially those with progressive thinning but no perforation, CXL can halt disease progression and even induce some thickening of the corneal stroma. Five-year follow-up data have demonstrated stabilization of keratometric values and improved visual acuity after the procedure 6.

Surgical Interventions

For advanced TMD with severe thinning (corneal thickness ≤150 μm), risk of perforation, or extensive involvement, surgical intervention becomes necessary.

• Lamellar Keratoplasty (LK): This procedure involves replacing the thinned corneal section with a donor graft. Partial LK is often preferred for localized disease, while total LK is reserved for more extensive cases. Both approaches have shown significant improvement in visual acuity and reduction in astigmatism, though partial LK tends to yield better outcomes 7.
• Ring-Shaped Corneoscleral Lamellar Keratoplasty: In cases of circumferential thinning, a ring-shaped graft guided by advanced imaging techniques (HD-OCT, Pentacam) can be used. This method significantly reduces intraoperative risks and postoperative complications while improving vision and corneal stability 4.
• Free-Hand Peripheral Grafting: In select cases, hand-crafted grafts are employed to reinforce thinned areas. This technique is technically challenging due to the peripheral location but can be effective when performed by experienced surgeons 5.

Complications and Postoperative Care

While surgical treatments are generally effective, complications can occur, including perforation during surgery, graft rejection, persistent epithelial defects, or recurrence of marginal degeneration. Close follow-up with advanced imaging is recommended to monitor graft health and disease stability 4 5 7.

Conclusion

Terriens Marginal Degeneration is a rare but impactful corneal disease that requires careful diagnosis and management. Its slow progression, non-inflammatory nature, and potential for severe visual distortion make it a unique challenge for patients and clinicians alike. Thanks to advances in imaging and surgical techniques, outcomes continue to improve for those affected.

Key Takeaways:

• TMD presents most commonly with progressive blurred vision and high astigmatism, but may be asymptomatic in early stages 1 2 3.
• The disease is most often bilateral, non-inflammatory, and affects middle-aged men, but can occur at any age 1 2.
• The exact cause is unknown, but degenerative changes and characteristic histopathologic findings are central features 1.
• Conservative management with glasses or contact lenses is often effective in early disease; advanced cases may require collagen cross-linking or surgical intervention such as lamellar keratoplasty 1 3 4 6 7.
• Newer surgical techniques guided by high-definition imaging are improving outcomes for patients with severe disease 4 7.
• Regular monitoring and individualized care remain the cornerstones of effective TMD management.

By staying vigilant to its subtle signs and evolving treatment options, both patients and eye care professionals can work together to protect sight and quality of life for those living with Terriens Marginal Degeneration.