Bone augmentation of the osteo-odonto alveolar lamina in MOOKP—will it delay laminar resorption?

Artificial Cornea: Past, Current, and Future Directions

Corneal diseases are a leading cause of blindness with an estimated 10 million patients diagnosed with bilateral corneal blindness worldwide. Corneal transplantation is highly successful in low-risk patients with corneal blindness but often fails those with high-risk indications such as recurrent or chronic inflammatory disorders, history of glaucoma and herpetic infections, and those with neovascularisation of the host bed. Moreover, the need for donor corneas greatly exceeds the supply, especially in disadvantaged countries. Therefore, artificial and bio-mimetic corneas have been investigated for patients with indications that result in keratoplasty failure. Two long-lasting keratoprostheses with different indications, the Boston type-1 keratoprostheses and osteo-odonto-keratoprostheses have been adapted to minimise complications that have arisen over time. However, both utilise either autologous tissue or an allograft cornea to increase biointegration. To step away from the need for donor material, synthetic keratoprostheses with soft skirts have been introduced to increase biointegration between the device and native tissue. The AlphaCor™, a synthetic polymer (PHEMA) hydrogel, addressed certain complications of the previous versions of keratoprostheses but resulted in stromal melting and optic deposition. Efforts are being made towards creating synthetic keratoprostheses that emulate native corneas by the inclusion of biomolecules that support enhanced biointegration of the implant while reducing stromal melting and optic deposition. The field continues to shift towards more advanced bioengineering approaches to form replacement corneas. Certain biomolecules such as collagen are being investigated to create corneal substitutes, which can be used as the basis for bio-inks in 3D corneal bioprinting. Alternatively, decellularised corneas from mammalian sources have shown potential in replicating both the corneal composition and fibril architecture. This review will discuss the limitations of keratoplasty, milestones in the history of artificial corneal development, advancements in current artificial corneas, and future possibilities in this field.

Endophthalmitis in Eyes with Osteo-odonto Keratoprosthesis

Aim: To analyze the incidence, microbiological profile, risk factors, and outcomes in eyes with osteo-odonto keratoprosthesis (OOKP) developing endophthalmitis.Methods & material: Retrospective review of medical records of patients presenting between 2003 and 2013 with OOKP and endophthalmitis was undertaken after obtaining IRB approval. Patient demographics, clinical features, microbiological evaluation, treatment details, and outcomes were analyzed.Results: Of 92 eyes with OOKP, 8 (9%) had endophthalmitis. Indications for OOKP included Steven-Johnson syndrome (SJS; n = 6; 75%) and chemical injuries (n = 2; 25%). The mean duration from OOKP surgery to endophthalmitis was 49.4 ± 32.3 months. Seven of eight eyes had associated laminar resorption. Endophthalmitis resolved with conservative management in three eyes. Lamina removal was required in three eyes; one eye underwent evisceration. At presentation, mean BCVA was 2.76 ± 0.24 logMAR that improved to 2.48 ± 1.0 logMAR after intervention. Mean follow-up was 12.6 ± 13.2 months.Conclusion: Endophthalmitis portends a grave prognosis for eyes with OOKP. The most important risk factors are SJS (75%) and lamina resorption (88%).

Osteokeratoprosthesis Using Tibial Bone: Surgical Technique and Outcomes

PURPOSE

To analyze the anatomical and functional results of keratoprosthesis using tibial bone autograft.

METHODS

We reviewed 113 charts of patients who underwent tibial bone osteokeratoprothesis implantation at the Centro de Oftalmologia Barraquer. Kaplan-Meier survival curves with 95% confidence interval were calculated for functional success, defined as best corrected visual acuity (BCVA) ≥0.05 on the decimal scale, and for anatomical success, defined as retention of the keratoprosthesis lamina. Multivariate analysis was used to test the impact of clinical factors on anatomical and functional survival rates.

RESULTS

Based on Kaplan-Meier analyses, tibial bone keratoprosthesis 5-year and 10-year anatomical survival rates were 69.5% and 53.5%, respectively. Functional survival rate at 5 years was 33% and at 10 years was 19.2%. Considering primary diagnosis, chemical burn had better anatomical and functional survival rates than autoimmune or infectious diseases. Patient age did not have a significant effect on keratoprosthesis survival rates. About 48.7% of the patients who underwent surgery had complications: keratoprosthesis extrusion, glaucoma, retinal detachment and buccal mucosa necrosis were the most frequent ones.

CONCLUSION

Half of the patients with tibial bone KPro had retained the keratoprosthesis after 10 years post-surgery and one-fifth of them had visual acuity of 0.05 or better at the same period. Considering that these patients have no other way to recover their vision either because they have no canine tooth or their buccal or dental conditions are not adequate for OOKP, this modified surgery is their only hope.