Three-Dimensional Optical Coherence Tomography Imaging For Glaucoma Associated With Boston Keratoprosthesis Type I and II

Optical Coherence Tomography Angiography in Patients With the Boston Keratoprosthesis Type 1

PURPOSE

To report on optical coherence tomography angiography (OCTA) in patients with a type 1 Boston keratoprosthesis (KPro) and determine its feasibility through assessment of imaging artifacts.

METHODS

KPro and non-KPro subjects were matched for age, gender, and glaucoma diagnosis. OCTA images of the peripapillary optic nerve were obtained, reviewed by 2 readers masked to the diagnosis for artifacts and usability, and used for microvascular measurements.

RESULTS

KPro subjects (n = 18) had worse visual acuity than non-KPro (n = 36) subjects (LogMAR mean ± standard deviation 0.36 ± 0.30 vs. 0.07 ± 0.11, P < 0.001) and a greater proportion were monocular (56% vs. 3%, P < 0.001). OCTA from KPro eyes had more artifacts per scan than images from non-KPro eyes (4 ± 2 vs. 2 ± 2, P < 0.001). About 33% of KPro images were useable based on having image quality score above 40 and artifact in less than 10% of the peripapillary region. Worse visual acuity (odds ratio [OR] 0.01, 95% confidence interval [CI] 2 x 10-4-0.30, P = 0.02) and KPro (OR 0.19, 95% CI 0.05-0.63, P = 0.008) were associated with lowered likelihood of usability. Useable OCTA from 3 KPro eyes with glaucoma demonstrated microvascular defects in the inferior peripapillary region and lower vessel density and flow compared with 3 KPro eyes without glaucoma.

CONCLUSIONS

This is the first study assessing OCTA in KPro patients and identified a higher incidence of artifacts that may be associated with the KPro optic. About 33% of KPro images were useable for microvascular measurements, supporting further OCTA research in this population to assess vascular pathology of glaucoma.

Clinical Outcomes and Early Postoperative Complications in Boston Type I Keratoprosthesis Implantation: A Retrospective Study

Background/Objectives: The purpose of this study is to evaluate clinical outcomes and early postoperative complications in patients undergoing Boston type I keratoprosthesis (BKPro) implantation, with a specific focus on the onset and nature of ocular surface disorders during the early postoperative period. Methods: This retrospective study included 77 eyes that underwent BKPro implantation between 2019 and March 2022. Patients were treated at the Saint Barbara Hospital, Trauma Centre, Sosnowiec, Poland, and District Railway Hospital, Katowice, Poland. Data were collected from medical records, including patient demographics, medical history, surgical outcomes, postoperative visual acuity, and complications. The analysis incorporated both detailed medical history and direct clinical examination results. Results: The most common early postoperative complication was glaucoma, affecting 32 eyes (42%). Retroprosthetic membrane formation occurred in 20 eyes (26%), while partial extrusion of the BKPro was observed in 10 eyes (13%). Severe corneal surface damage was noted in patients with underlying autoimmune diseases (36%) and after chemical burns (24%). Five patients suffered from transient hypotony resulting from keratoprosthesis extrusion. The results highlight the complex nature of managing ocular surface conditions and the frequent challenges associated with early postoperative complications. Conclusions: BKPro implantation is an effective solution for severe corneal diseases that are resistant to conventional treatments. However, it is associated with a significant risk of early complications, particularly glaucoma and retroprosthetic membrane formation. Early identification and management of these complications are crucial for improving outcomes and maintaining visual function. Further research into optimizing postoperative care is needed to minimize these risks and enhance patient outcomes.

Artifacts in OCT Retinal Nerve Fiber Layer Imaging in Patients with Boston Keratoprosthesis Type 1

PURPOSE

To determine the clinical utility of OCT retinal nerve fiber layer (OCT RNFL) imaging for glaucoma evaluation in patients with Boston keratoprosthesis type 1 (KPro) by investigating imaging artifacts.

DESIGN

Case-control study.

SUBJECTS

Patients with KPro and without KPro (controls) matched for age, gender, and glaucoma diagnosis.

METHODS

The most recent Cirrus OCT RNFL scan from 1 eye was categorized as having good signal strength (SS; ≥ 6 out of 10) or poor SS (< 6). Those with good SS were analyzed by 2 independent reviewers for artifacts. Images with good SS and no artifacts affecting the scanning circle were considered useful for glaucoma evaluation.

MAIN OUTCOME MEASURES

The incidence of poor SS and artifacts in OCT RNFL images; patient characteristics associated with useful scans.

RESULTS

Sixty-five patients with KPro and 75 controls were included; 89.2% of KPro patients and 89.3% of control subjects had glaucoma (P = 0.98). Forty percent of KPro patients and 5.3% of controls had poor SS (P < 0.001). The proportion of images with either poor SS or artifacts was similar in KPro (76.9%) vs. controls (72.0%, P = 0.51). The most common artifacts in both groups were missing data (43.6%, 53.2%, respectively, P = 0.32) and motion artifact (25.6%, 19.7%, respectively, P = 0.47). Images were useful for glaucoma evaluation in 43.1% of KPro patients and in 69.3% of controls (P = 0.002). In the KPro group, patients with useful OCT scans, compared with those without, had better visual acuity (0.4 ± 0.3 vs. 0.9 ± 0.7 logarithm of the minimum angle of resolution, P = 0.004), and did not have congenital corneal pathologies (0.0% vs. 24.3%, P = 0.008). A multivariate analysis showed that KPro patients with older age had higher odds of useful OCT images (odds ratio, 1.05; P = 0.03). Among KPro patients with useful OCT scans, retinal nerve fiber layer thickness correlated with observed cup-to-disc ratio (Pearson correlation: r = -0.42, P = 0.03).

CONCLUSIONS

The rate of OCT RNFL images with either poor signal strength or artifacts in the KPro and control population was comparable. In patients with KPro, where intraocular pressure measurements are difficult and glaucoma is highly prevalent and often severe, OCT RNFL imaging can be useful for glaucoma evaluation.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Glaucoma management in patients with penetrating keratoplasty or keratoprosthesis

PURPOSE OF REVIEW

Advances in surgical techniques and postoperative care have significantly improved rates of short-term complications following keratoplasty; however, glaucoma remains a highly prevalent long-term and potentially devastating complication for postkeratoplasty patients. In this review, we provide an overview of recent literature on glaucoma management in patients who have undergone penetrating keratoplasty or the Boston keratoprosthesis type I (KPro) implantation.

RECENT FINDINGS

New research suggests an inflammatory cause underlying glaucoma following KPro. Accurate IOP measurement is difficult in patients postkeratoplasty; study of objective techniques such as PDCT or Tono-Pen in penetrating keratoplasty eyes and trans-palpebral Diaton tonometry in KPro eyes have shown promising results. Early glaucoma surgical intervention should be considered for patients undergoing penetrating keratoplasty and KPro.

SUMMARY

Patients who have undergone penetrating keratoplasty or implantation of the Boston keratoprosthesis type I should be monitored frequently for elevated intraocular pressure and for other signs of glaucomatous optic nerve damage. Intraocular pressure elevation should be treated promptly either medically or surgically while minimizing risk to the corneal graft. Further research into inflammatory causes and other treatment modalities is promising for the long-term visual success in these patients.

Management of glaucoma with Boston type 1 keratoprosthesis

PURPOSE

To describe the frequency, clinical characteristics, complications, and management of glaucoma in eyes that underwent keratoprosthesis implantation.

METHODS

Patients who underwent keratoprosthesis surgery between June 2010 and January 2020 were retrospectively evaluated for glaucoma association and prognoses.

RESULTS

Among 17 patients who underwent keratoprosthesis surgery, 9 (52.9%) were associated with underlying or keratoprosthesis-induced glaucoma. Five eyes (29.4%) had underlying glaucoma and underwent a glaucoma drainage device implantation at least 6 months before keratoprosthesis surgery. One eye (5.9%) with normal intraocular pressure had glaucoma drainage device implantation at the same session with keratoprosthesis surgery due to high-risk characteristics of anterior segment structures. Four eyes with preexisting glaucoma showed progression after keratoprosthesis surgery. Additional antiglaucomatous treatment was commenced in two eyes whereas implantation of 2nd glaucoma drainage device was performed in two eyes. Postoperative complications in three eyes (100%) with glaucoma drainage device implanted 6 months before or at the same session with aphakic type keratoprosthesis surgery with partial vitrectomy included rhegmatogenous retinal detachment in two eyes and bacterial endophthalmitis in one eye. Migration of silicone oil through the tube to the subconjunctival area was seen after pars plana vitrectomy in one eye. None of the three eyes (0%) that underwent glaucoma drainage device implantation years before keratoprosthesis surgery experienced a posterior segment complication other than glaucomatous progression. Out of 11 eyes with no previous history of glaucoma, 3 (27.3%) showed high intraocular pressure and glaucomatous disc changes after keratoprosthesis surgery, which could be pharmacologically controlled.

CONCLUSIONS

In this cohort, eyes with preexisting glaucoma were more difficult to manage compared to eyes with de novo glaucoma after keratoprosthesis surgery. Retinal complications appeared more often when glaucoma drainage device implantation was performed no more than 6 months before aphakic type keratoprosthesis surgery with partial vitrectomy.

The Boston Keratoprosthesis-The First 50 Years: Some Reminiscences

Millions of people worldwide are bilaterally blind due to corneal diseases including infectious etiologies, trauma, and chemical injuries. While corneal transplantation can successfully restore sight in many, corneal graft survival decreases in eyes with chronic inflammation and corneal vascularization. Additionally, the availability of donor cornea material can be limited, especially in underdeveloped countries where corneal blindness may also be highly prevalent. Development of methods to create and implant an artificial cornea (keratoprosthesis)may be the only option for patients whose eye disease is not suitable for corneal transplantation or who live in regions where corneal transplantation is not possible. The Boston keratoprosthesis (B-KPro) is the most commonly implanted keratoprosthesis worldwide, having restored vision in thousands of patients. This article describes the initial design of the B-KPro and the modifications that have been made over many years. Additionally, some of the complications of surgical implantation and long-term care challenges, particularly complicating inflammation and glaucoma, are discussed. Expected final online publication date for the Annual Review of Vision Science, Volume 8 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Challenges of Glaucoma Management in Patients with Type I Boston Keratoprosthesis

Type I Boston keratoprosthesis is implanted in patients with severely diseased eyes who are considered poor candidates for traditional keratoplasty. Glaucoma is considered a major visual comorbidity following the implantation of type I Boston keratoprosthesis (KPro). Eyes that receive a Boston KPro are at high risk of progression of pre-existing glaucoma and the development of de novo glaucoma. Both complications can limit best-corrected visual acuity postoperatively. Diagnosis and surveillance for glaucoma in KPro eyes are fundamental to mitigate the risk of visual morbidity. However, managing these patients presents several challenges. The diagnosis of glaucoma after KPro implantation is usually hindered by inaccurate intraocular pressure (IOP) measurements and unreliable ophthalmic investigations such as visual field testing and optical coherence tomography (OCT) of the retinal nerve fiber layer (RNFL). In these eyes, medical management of glaucoma with topical medications is usually insufficient, and glaucoma surgery is usually warranted either prior to or during KPro implantation. Options for glaucoma surgery include glaucoma drainage device (GDD) and cyclodestructive procedures. The aim of this article is to highlight the incidence, pathophysiology, diagnosis, and management options of glaucoma in eyes that have undergone type I Boston keratoprosthesis.

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.

Boston Type 1 Keratoprosthesis: Updated Perspectives

The use of Boston type 1 keratoprosthesis (BKPro) has significantly increased worldwide. It is no longer considered a procedure of last resort but a reasonable option for patients with otherwise poor prognosis for a traditional penetrating keratoplasty. BKPro was approved by the Food and Drug Administration in 1992 for bilateral severe corneal blindness due to multiple corneal transplant failure. Over the years, indications have extended beyond recurrent immunologic rejection to include other conditions such as chemical injury and other causes of bilateral limbal stem cell deficiency, extensive corneal neovascularization, neurotrophic corneas and hypotony, among others. Numerous advances in the design of the BKPro, improvement of preoperative, intraoperative and postoperative management have resulted in favorable outcomes and a reduction in postoperative complications. Accordingly, many studies have shown that implantation of this device is highly effective in restoring vision with very good short-term outcomes. However, due to the lifetime risk of sight-threatening complications after BKPro implantation, a longer follow-up period should provide outcomes that are more realistic. In this review, the authors examined only the results of publications with an average of at least 2 years of follow-up. The overall intermediate to long-term visual outcomes and retention rate in BKPro seem to be favorable. However, autoimmune diseases and cicatrizing conditions continue to show a higher incidence of postoperative complications that require further management.