How to manage calcific deposits in the corneal stroma?

Management of Calcific Deposits in the Corneal Stroma

For calcific deposits in the corneal stroma, treatment should be reserved for symptomatic cases causing visual impairment, glare, or pain, with EDTA chelation (3-4% disodium EDTA) after epithelial debridement being the first-line intervention for band keratopathy, while deeper stromal calcifications require phototherapeutic keratectomy (PTK) with masking agents or anterior lamellar keratectomy depending on depth. 1

Initial Assessment and Treatment Indications

Observation is appropriate for asymptomatic calcific deposits. 1 Treatment is indicated only when patients experience:

• Visual disability or glare affecting quality of life 1
• Pain from epithelial disruption overlying calcium deposits 1
• Functional impairment in daily activities 1

Treatment Algorithm Based on Deposit Location and Depth

Superficial Deposits (Band Keratopathy - Bowman's Layer)

EDTA chelation is the gold standard for superficial calcific band keratopathy. 1

Mechanical removal first for thick plaques:

• Extract thick flake-like or plaque excrescences directly with forceps and scraping 1
• This reduces the burden before chemical chelation 1

EDTA chelation technique:

• Remove overlying epithelium by debridement 1
• Apply 3-4% disodium EDTA solution using cellulose sponge or sterile cotton applicator 1
• Rub against residual calcium until dissolution occurs 1
• Alternative methods include direct EDTA drops, EDTA-filled well, or EDTA-soaked disc application 1
• Treatment time varies with calcium density (typically several minutes to 20+ minutes) 1
• Can be performed at slit-lamp in clinic setting 1

Critical post-procedure considerations:

• Expect delayed healing: 5-7 days versus 2-3 days for standard corneal abrasions 1
• Minimize limbal exposure to EDTA to achieve faster re-epithelialization 1
• Slower healing increases risk of stromal scarring and infection 1

Adjunctive measures for high-risk cases:

• Use amniotic membrane grafting for patients with limbal stem cell deficiency, neurotrophic keratopathy, or severe dry eye 1, 2
• Consider temporary tarsorrhaphy to facilitate re-epithelialization 1
• If ocular surface disease is severe, the risks may outweigh benefits—avoid keratectomy 1

Anterior to Mid-Stromal Deposits

Phototherapeutic keratectomy (PTK) is the preferred treatment for stromal calcific deposits, particularly when limited to anterior 10-15% of stromal thickness. 1, 3, 2

PTK technique for calcium deposits:

• Calcific deposits ablate more quickly than surrounding tissue, creating crevices and irregularities 1
• Mandatory use of masking agents (methylcellulose or sodium hyaluronate) to fill depressions adjacent to calcium deposits 1, 3
• This prevents surrounding depression formation as calcium requires more energy for ablation than normal tissue 1
• Masking fills valleys so peaks ablate first, creating smooth post-ablation surface 1, 3

PTK outcomes:

• Best-corrected visual acuity (BCVA) significantly improves at 2,6, and 12 months 1, 4
• Uncorrected visual acuity typically does not improve significantly at 6 months 1
• Visual improvement correlates with corneal transparency, regularity, and optical quality 1

Mitigation of hyperopic shift:

• Treat along outer edge of ablation zone with small spot ablations 1
• Use refractive setting to reduce flattening effect 1

Mitomycin-C (MMC) application:

• Apply 0.02% MMC on circular sponge to corneal stroma after laser treatment for high-risk cases 1, 4, 3
• Reduces recurrent scar tissue and stromal deposits 1, 3
• Copious irrigation with saline or balanced salt solution is mandatory after MMC to prevent stromal melt, ocular surface toxicity, and endothelial toxicity 1, 3

Deeper Stromal Deposits

Anterior lamellar keratectomy is indicated for calcific deposits extending beyond anterior stroma into mid-stroma. 1, 4, 3

Surgical approach selection:

• Freehand lamellar keratectomy (microblade, lamellar dissector, spatula) requires minimal equipment but produces irregular surface 1, 4
• Microkeratome or femtosecond laser-assisted keratectomy provides superior refractive surface and improved visual acuity 1, 4, 3
• Combined mechanical/femtosecond flaps with PTK show significant BCVA improvement at 2,6, and 12 months 1, 4

Depth guidance:

• Use anterior segment OCT, ultrasound biomicroscopy (UBM), or confocal microscopy to guide dissection depth and diameter 1, 3

Critical Complications and Prevention

Corneal ectasia risk:

• Avoid ablation exceeding anterior third of corneal stroma 1
• Ensure residual stromal bed is at least 250 μm 1

Infectious keratitis:

• Any epithelial disruption increases infection risk 1
• Consider herpes simplex virus reactivation from excimer laser exposure, corticosteroid use, and corneal trauma 1
• Provide perioperative antiviral prophylaxis for any history of herpetic eye disease 1

Delayed epithelial healing:

• Use autologous serum tears to promote corneal nerve regeneration 1, 4
• Apply amniotic membrane (self-retained, glued, or sutured) to facilitate healing 1, 2

Recurrence:

• PTK may be repeated for recurrent disease 1
• PTK can defer eventual deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PK) in some cases 1

Special Considerations

Identify and address underlying causes:

• Systemic hypercalcemia requires medical workup 1
• Chronic ocular inflammation needs concurrent treatment 1, 2
• Discontinue phosphate-buffered medications in chronic corneal disease to prevent further calcification 5
• Cenegermin (recombinant human nerve growth factor) can cause acute calcific band keratopathy—monitor closely during treatment 6

When keratoplasty is necessary:

• Reserved for extensive stromal involvement unresponsive to above measures 1, 6
• Endothelial keratoplasty preferred over penetrating keratoplasty when endothelium is compromised 4