Corneal blindness in the developing world: The role of prevention strategies

Primordial prevention strategies

Enhancing ocular protection and hygiene:

Promoting eye safety practices such as wearing protective eyewear when engaging in activities that pose a risk of eye injury, such as sports and construction work, can prevent corneal injuries that may lead to blindness. Encouraging good hygiene practices such as regular handwashing, avoiding touching the eyes with dirty hands, and ensuring safe contact lens hygiene can help reduce the incidence of corneal infections. Social media platforms can effectively disseminate the message and reach a wide audience, amplifying the awareness and impact of these initiatives.

Dietary and nutritional aid:

Ensuring a well-balanced diet rich in essential nutrients, particularly vitamin A, can reduce the burden of vitamin A deficiency related corneal pathologies in children and young adults. This can be tackled by increasing awareness amongst healthcare workers who are in direct contact with preschool children and young women. These individuals can sensitize caregivers regarding the importance of a nutritious diet in preventing xerophthalmia. Additionally the use of fortified food can add to the daily intake of vitamin A.³⁰

Genetic screening:

Genetic screening for hereditary corneal dystrophies can identify individuals carrying recessive genes and help in premarital counselling. This will not only facilitate reducing the incidence of corneal blindness but also help identifying “at risk” groups who will benefit from screening of these diseases.

Epidemiological research:

Epidemiological research is one of the most significant gaps that requires immediate attention since this data will help improve our understanding of the risk factors, at-risk groups, and potential strategies to prevent corneal blindness. This is especially true with respect to establishing the true incidence and prevalence of corneal blindness which is currently calculated using surrogate measures such as indications of keratoplasty and hospital-based registries which are prone to their inherent biases. Identifying the most important factors responsible for these preventable causes of corneal blindness will allow concentrating efforts and resources on mitigating the same.

Policies and legislations:

With the data from large population-based studies, ophthalmic societies can propose and advocate legislations that promote eye safety and health. Examples include better packaging of edible lime which is an important cause of severe ocular burns in South Asia and ensuring standardised, appropriate protective eyewear for workers in factories and agrarian settings.³¹ Implementing these policies and regulations at the national or community level can have a significant impact on primordial prevention.

Improving health education and public awareness:

Promoting programs that educate people on lifestyle modifications and health practices can decrease the risk of corneal diseases. This starts with increasing awareness of diseases such as infectious keratitis, vitamin A deficiency and ocular burns in the context of their consequences and measures of prevention. This can also involve engaging communities such as school employees and factory workers in these promotion activities and creating opportunities for active participation which can foster a sense of ownership and responsibility for eye health. Improving health care seeking practice in the event of any ocular trauma or suspicion of infection should be advocated. Additionally, procuring over the counter medications and usage of traditional remedies should be discouraged.

Primary prevention

Promoting eye safety practices:

Promoting eye safety practices include wearing protective eyewear by workers in industries with a high-risk for ocular trauma, burns, and infections. Training should be provided to the workers to administer basic first aid at the work site. While there is some understanding of these predisposing factors and the individuals at risk, extensive research is required to comprehensively identify the exact risk factors associated with each condition and determine the populations most susceptible to it. This will also help advocate the necessary policy changes.

Curriculum based residency programs:

The implementation of well-defined guidelines for surgical training of residents and trainees will facilitate the evaluation of their performance and provide support whenever necessary. Adequate supervision and assistance based on each phase of the learning curve will help improve the outcomes of cataract surgery and decrease the prevalence of pseudophakic/aphakic bullous keratopathy.

Nutritional support and vaccinations:

Nutritional support and vaccinations that specifically target young children and pregnant women can help reduce the incidence of xerophthalmia related blindness which is an important and preventable cause of corneal blindness in low income countries. Current guidelines dictate that vitamin A prophylaxis is to be administered only to at-risk individuals. These doses are administered as per recommended protocols to pregnant women and children less than six years of age residing in areas which are endemic to vitamin A deficiency.²² Similarly ensuring children are appropriately vaccinated against measles can help reduce the incidence of xerophthalmia.³²

Secondary prevention

Health education:

Since the secondary prevention level is targeted at screening and early detection of the disease with prompt institution of treatment, specific measures will be unique to each disease. Furthermore, all measures will necessitate the presence of both trained personnel and ease of access to the same. The outcomes of ocular trauma, whether it be penetrating injuries or ocular burns, are significantly influenced by the promptness and effectiveness of the initial first aid/surgical interventions provided. Increased public awareness of these interventions will improve care seeking practice and permit setting up of first aid centres that can be manned by non-ophthalmic individuals.

Screening and early detection:

Screening programmes that target high-risk populations such as schools for vitamin A deficiency and predisposed groups for genetic corneal pathologies will help early detection of these diseases and enable timely interventions. Similarly setting up smaller units in villages with trained ophthalmic personnel can help screen and treat corneal epithelial defects and abrasions before they fulminate into infectious keratitis.^33,34

Medical and surgical therapy:

Ensuring the availability of medications targeting the microorganisms commonly involved in infectious keratitis in specific geographic regions is essential. Similarly setting up reliable and efficient labs that can detect these pathogens are also paramount to ensure an accurate microbiological diagnosis is being made.³⁵ Use of innovative techniques such as trypan blue for fungal filaments, that provide simple, rapid and reliable methods of examination will also enable early diagnosis of infectious keratitis.³⁶ Educating general ophthalmologists in triaging severity of infections and ocular trauma will enable appropriate and timely referrals to higher centres for the necessary care. Providing surgical training for fundamental procedures like corneal tear repairs, corneal foreign body removals, amniotic membrane grafts, and tarsorrhaphies, can not only ensure timely execution of these procedures but also alleviate the workload on advanced centres, thus, allowing them to concentrate on more complex cases.

Tertiary prevention

This tier focuses on addressing the sequelae of different corneal pathologies and ensuring visual rehabilitation to improve the quality of life. The majority of the clinical care currently provided falls within this level, and this section will discuss existing approaches and propose methods to improve upon them.

Corneal transplantation:

This is the main modality of treatment for several corneal pathologies and aims to replace the diseased cornea with a healthy one. However, there are several issues that prevent optimal implementation of this procedure in developing countries.

The demand for donor corneas is not met by the supply and this needs to be addressed by improving the infrastructure and human resources. Estimates show that nearly 13 million individuals currently await a corneal transplantation globally and one million new cases get added every year.^12,37 This discrepancy between the demand and supply is exacerbated in developing countries. For example, In India, 100,000 transplantations per year are necessary to reduce the burden of corneal blindness. However, the procurement rate is less than 25% of this burden--and only half the harvested corneas are utilized.^38–40 Hence, to meet the needs of corneal transplantation, nearly 200,000 corneas need to be harvested. Ensuring these numbers requires a multipronged approach which targets the donor tissue availability as well as its storage and preservation. A multitiered system with eye banks that cater to a predefined target population can effectively expand their reach and secure an ample supply of donor corneas. This infrastructure should support not only traditional corneal transplantation but also the newer lamellar techniques. Increased public awareness of eye donation programmes and the need for donor corneas will help close the supply gap. The establishment of centralized registries, documenting patient lists and prioritizing their needs, can facilitate the allocation of this valuable resource to individuals in greatest need on a priority basis.

Capacity building plays a crucial role in facilitating the optimal utilization of corneal tissues. This includes not only the training of corneal surgeons in the fundamental aspects of keratoplasty but also paraclinical staff to ensure the accurate collection of viable donor corneas. Eye bank technicians need to be trained in preparing lamellar endothelial grafts. Ensuring the presence of trained corneal surgeons in rural areas will not only enhance access to keratoplasty facilities but also facilitate improved adherence to postoperative follow-up and care.⁴¹ Providing training to corneal surgeons in lamellar keratoplasties and other emerging surgical modalities will aid in their widespread adoption and implementation. This will not only result in improved outcomes but also enable the utilization of multiple grafts from a single donor tissue, maximizing the potential benefits of each donated cornea.⁴² Finally, corneal surgeons should be versed not only in surgical skills but also in judicious case selection which will go a long way in optimizing the utilization of this scarce resource and improving the outcomes of these grafts.

Alternatives to corneal transplantation

The limitations of corneal transplantation have been discussed in the previous section which highlight how relying solely on keratoplasties is not a viable option for developing countries. Even for cases which have a good prognosis such as keratoconus or corneal opacifications without vascularization/anterior segment abnormalities, the postoperative course is subject to several issues which can affect the final visual outcome. This includes post-keratoplasty astigmatism, suture-related complications, graft infiltrates, and secondary glaucoma.^43–45 Moreover, the postoperative care demands rigorous adherence and relies heavily on the patient's diligent compliance, as well as the presence of a supportive socio-economic system. However, establishing such a system can often pose challenges, especially in developing countries. Hence, alternatives to keratoplasties that circumvent these issues and provide long-term effective and reliable outcomes are the need of the hour.

Contact lenses (CL):

Although CL have been around for several decades, it is with the advent of better lens materials and large scleral lenses with fluid reservoirs that they became game changers for corneal specialists.^46–48 They are indicated in a vast number of diseases that range from corneal scars and keratoconus to severe ocular surface diseases.^49–52 They not only improve the visual function by correcting the irregular astigmatism but also improve the overall health of the ocular surface. Enhancing awareness regarding the indications and benefits of these lenses will play a crucial role in promoting CL use. Training ophthalmologists and optometrists in dispensing these lenses will contribute to their broader distribution.

Ocular surface reconstruction and artificial corneas:

Very often patients with seemingly opaque corneas can experience complete visual rehabilitation through procedures such as limbal stem cell transplantation. Surgeries such as simple limbal epithelial transplantation can not only address the deficient limbal epithelial stem cells but also modulate the underlying corneal scar and decrease its density.^53–56 These procedures have stable long-term outcomes with good visual function, thus eliminating the need for keratoplasty in cases where corneal transplantation would not yield favourable outcomes.^55,57,58 Providing training to corneal surgeons in the indications, perioperative management, and surgical techniques related to these procedures will equip them with the necessary skills to effectively handle such cases. Dissemination of information on basic and complex ocular surface reconstruction procedures will allow continued medical education to occur.^59–63 Conducting periodic workshops will also help refresh these skills. Research endeavours are crucial to developing similar techniques that can circumvent the necessity for corneal grafting in these patients.

The use of prosthetic devices to replace the diseased cornea has been explored for several decades and recent advances have offered options that have good visual outcomes.^64–66 Furthermore, they do not require high grade corneal tissue, and thus help improve utilization rates. However, the retention and long-term efficacy of these devices remains a limitation.^64–66 With the advent of completely synthetic devices such as the CorNeat, corneal replacements can be carried out independent of donor corneal tissues.^67,68

Molecular therapy:

This is another appealing option that modulates scar formation during the process of corneal wound healing thus preventing the formation of the scar itself. Several interventions are being explored with respect to this and include bioactive molecules, exosomes, nanomedicine, recombinant viral vectors, and microRNAs.^69,70 However, these are still in the experimental phase and will require clinical validation prior to their adoption in routine clinical practice.

Bioengineered cornea:

Substitutes for the cornea are an attractive option aimed at addressing the issue of deficient donor tissue. These substitutes can be cell-based, which recreate individual layers of the epithelium, stroma and endothelium.⁷¹ The other approach to tissue engineering is the scaffold-based models which are primarily for stromal regeneration. These models can be natural or synthetic. The former has a better capacity for integrating with the surrounding host tissue, while the latter can be modulated to the desired requirements.^72,73 Natural polymers can also be obtained from human donor corneas which are deemed unsuitable for transplantation. As a result, this approach enables optimal utilization of tissue resources and allows for the acquisition of multiple grafts from a single tissue source.⁷² The use of 3D-printing technology to print an artificial cornea with raw materials such as collagen, alginate, and decellularized extracellular matrix is a promising solution to the problem of deficient donor corneas.⁷⁴

Other advances such as cultured endothelial cells which can be directly injected into the anterior chamber can not only be used as the primary treatment modality in pseudophakic bullous keratopathies but also for failed grafts.^75,76 This can provide a minimally invasive option to revive otherwise failed transplants. Other options include targeted gene therapy and anti-sense oligonucleotides.⁷⁶ Simple procedures such as removal of the diseased endothelium to pave the way for the surrounding endothelial cells in partial endothelial failure are also being explored.⁷⁶ These techniques that do not rely on donor tissue or specialized equipment are urgent requirements.

Supportive care and rehabilitation:

Persons with corneal blindness may suffer from a range of problems including but not limited to depression, economic and personal dependence, and mobility issues. Providing supportive care services and rehabilitation programs to these individuals to help them cope with the physical, emotional, and social aspects of their condition is a crucial aspect of tertiary care. This may involve physical therapy, occupational therapy, counselling, or support groups and helps them reintegrate into society. These services not only help maintain household independence but also financial independence to the greatest extent possible.

Universal eye health care:

The current standard of care can effectively treat a significant proportion of the causes of corneal blindness. However, there exist several barriers that prevent individuals afflicted with these diseases from accessing this care. In order to address these barriers, a comprehensive and collaborative approach is essential, involving various stakeholders including healthcare providers, policymakers, and both public and private financial aid organizations.⁷⁷ Incorporation of eye health into universal healthcare policies is imperative to ensure holistic care and this requires the necessary financial and human resource planning. By including eye care in these key areas, we can effectively address the diverse needs of individuals and communities and ensure accessible quality eye care services.