Corneal Collagen Cross Linking (CXL) in treatment of Pseudophakic Bullous Keratopathy

Use of corneal cross-linking beyond keratoconus: a systemic literature review

PURPOSE

The success of corneal collagen cross-linking in altering keratoconus' clinical course has driven a search for further uses of this procedure. This literature review aims to analyze the scientific evidence available for the benefit of cross-linking in the management of ophthalmic diseases other than progressive keratoconus or ectasia induced by corneal refractive procedures.

METHODS

A systemic literature review.

RESULTS

We reviewed 97 studies. We found that collagen cross-linking can limit the progression of several other corneal ectasias, thus reducing and limiting the need for keratoplasty. Collagen cross-linking also can reduce the refractive power of the cornea and can be considered for a moderate degree of bacterial keratitis or when the organism is unidentified, which is refractive to antibiotics alone. However, the comparative rarity of these procedures has limited the extent of evidence. In fungal, Acanthamoeba, and herpes virus keratitis, the evidence is inconclusive of the safety and efficacy of cross-linking.

CONCLUSION

Current clinical data is limited, and laboratory data has not fully correlated with published clinical data.

Therapeutic non-ectasia applications of cornea cross-linking

Corneal cross-linking is a photopolymerization technique traditionally used to strengthen corneal tissue. Corneal cross-linking utilizes riboflavin (vitamin B2) as a photosensitizer and ultraviolet-A light (UVA) to create strong covalent bonds within the corneal stroma, increasing tissue stiffness. Multiple studies have demonstrated corneal cross-linking's effectiveness in treating corneal ectasia, a progressive, degenerative, and non-inflammatory thinning disorder, as quantified by key tomographic, refractive, and visual parameters. Since its introduction two decades ago, corneal cross-linking has surpassed its original application in halting corneal ectatic disease and its application has expanded into several other areas. Corneal cross-linking also possesses antibacterial, antienzymolytic and antioedematous properties, and has since become a tool in treating microbial keratitis, correcting refractive error, preventing iatrogenic ectasia, stabilising bullous keratopathy and controlling post keratoplasty ametropia. This review provides an overview of the current evidence base for the therapeutic non-ectasia applications of cornea cross-linking and looks at future developments in the field.

Regular and irregular astigmatism of bullous keratopathy using Fourier harmonic analysis with anterior segment optical coherence tomography

Bullous keratopathy (BK) is known to present with corneal edema and Descemet's folds, which can cause corneal astigmatism. However, no report quantitatively evaluated BK astigmatism by separating it into regular and irregular astigmatism. This study investigated the regular and irregular astigmatism of the anterior and posterior corneal surface with Fourier harmonic analysis and anterior segment optical coherence tomography. Preoperative data from 43 eyes of 41 BK patients who received corneal endothelial transplantation were compared with the data from 43 eyes of 43 subjects without corneal disease. Anterior and posterior cylinder power, central corneal thickness (CCT) and thinnest corneal thickness were significantly greater in BK. With Fourier harmonic analysis, BK eyes were found to have significantly larger anterior and posterior regular astigmatism, asymmetry component and higher-order irregularity. Asymmetry component and higher-order irregularity that accounted for the posterior irregular astigmatism increased as CCT increased in BK. Higher-order irregularity in the posterior cornea also positively correlated with worsening best corrected visual acuity. Subgroup analysis found significant correlations between CCT and posterior higher-order irregularity for intraocular surgery and laser iridotomy, but not Fuchs endothelial corneal dystrophy. This study has significance in that it revealed the characteristics of the corneal posterior irregular astigmatism of BK.

A prospective, randomized clinical study comparing accelerated corneal collagen crosslinking with 5% NaCl hypertonic saline for bullous keratopathy in Asian eyes

BACKGROUND

We compared the clinical outcomes of accelerated corneal collagen crosslinking (CXL) and 5% NaCl hypertonic saline (HS) for the treatment of symptomatic bullous keratopathy (BK).

METHODS

A randomized controlled trial was held at Department of Ophthalmology, Tokyo Dental College Ichikawa General Hospital, Chiba, Japan. Twenty-three eyes of 23 consecutive patients with symptomatic BK were enrolled. The etiology of BK included pseudophakic BK, previous keratoplasty, previous endotheliitis, previous glaucoma surgery, trauma, herpes infection, as well as unknown causes. Eleven eyes received epi-off accelerated CXL (with epithelial abrasion and 18 mW/cm ultraviolet A irradiation for 5 minutes) and 12 eyes received HS instillation. In addition to the usual ophthalmic examination, the best-corrected visual acuity (BCVA) and central corneal thickness (CCT) were determined. The CCT was measured using anterior segment optical coherence tomography before and up to 6 months after treatments. Subjective symptoms of pain, blurred vision, photophobia, and irritation were also recorded.

RESULTS

The follow-up was completed for all patients in the CXL group. However, 6 patients in the HS group requested CXL treatments after 3 months. The BCVA was not significantly changed during the study periods in both groups. The CCT was significantly thinner in the CXL group compared to the HS group at 1 and 6 months (P = .015 and 0.144, respectively). Among the subjective symptoms recorded, irritation was significantly lower in the CXL group at 1 month (P = .013).

CONCLUSIONS

Accelerated CXL may produce transient improvement in pain and corneal edema in patients with BK.

Patient selection for corneal collagen cross-linking: an updated review

Corneal cross-linking (CXL) is an option that in the last decade has demonstrated its efficacy and safety in halting the progression of keratoconus (KCN) and other corneal ectasias. Its indication has been extended beyond the classic definition that required evidence of KCN progression, especially in the presence of some risk factors for a possible progression (particularly the younger age). However, the results can be still somewhat variable today. There are several protocols, each with its own advantages and disadvantages. Some predictors of CXL outcome have been identified. We will review the current knowledge on patient selection for CXL, its indications, and options in special cases (such as thin corneas).

Pseudophakic bullous keratopathy

Pseudophakic bullous keratopathy is characterized by corneal stromal edema with epithelial and subepithelial bullae due to cell loss and endothelial decompensation through trauma during cataract surgery. Patients present decreased vision, tearing, and pain caused by ruptured epithelial bullae. Cataract affects approximately 20 million people worldwide, and this complication can occur in 1 to 2% of the cataract surgeries. This study reviewed the bullous keratopathy etiopathogenesis and the clinical and surgical treatment available for this corneal disease.