the first task of public health scholars was to clarify the definition of health system . in the 1990s , the notion of the  district health system was seen as pivotal for health sector reform and the  modernization of the state , which started in the 1980s .
this decentralization strategy consisted of a transfer of responsibilities and decision - making power from central to district authorities within the various functions of health service management ( i.e. , finance , service organization , human resources , and general governance ) to a well defined population in a delineated administrative zone .
the main objective was to increase the capacities of district managers to respond to populations needs and bring decision - making services closer to populations .
in the world health report 2000 , world health organization ( who ) complemented the definition of the district health system with the concept of  health system. who defined a health system as  all organizations , people and actions whose primary intent is to promote , restore or maintain health. however , this definition reflected neither the interactions between actors nor the ongoing adaptations within systems in response to the changing environment [ fig . 1 ] . upon examination of the applications generated by this definition , it becomes apparent that the definition was a clear response to both the increasing demand from international donors for better accountability , as well as the need for appropriate health system performance assessment tools and methods .
the health system : actors , functions , and objectives ( adapted from who and islam ) defining a health system has become more challenging in a globalized world , due to the multiplicity of actors intervening on different scales and the increasing interactions between global health policies and local health systems .
every country has a unique health system characterized by the role of the government in the health system ( e.g. , liberal , socialist ) , the values of the health system ( i.e. , more or less equitable ) , the model of financing ( e.g. , taxes or private insurances ) , and its history .
eye care has traditionally been established as an entity separate from the rest of health care , although the vision 2020 strategy has extensively promoted the integration of eye care services .
this is because the majority of eye care services do not require the input of any other health services ( e.g. , an anesthetist is not required for adult cataract surgery whereas they might be required for an orthopedic surgery ) .
this has led to the existence of eye hospitals and eye clinics which stand alone from the rest of the health care structure .
this history has meant that eye care has been late in realizing the importance of health systems as an enabling factor [ fig . 2 ] .
the different foundations of the health system vision 2020 : the right to sight aims to eliminate avoidable blindness by the year 2020 . this aim will not be achieved by 2020 by eye care services acting in isolation .
eye care staff need to engage with the wider health system , identify ways to interact with their peers , influence decision makers , and advocate for change . increasing magnitude of blindness due to noncommunicable eye diseases such as glaucoma and diabetic retinopathy
are dependant prevention following on early detection , and raise the urgency to shift from vertical to more horizontally integrated programs .
this change is far more likely to occur , be effective , and sustainable if a health systems strengthening approach is taken .
the ministry of health has the responsibility of improving the health status of the populations , ensuring equal access to health services for every socio - economic group of society , ensuring that the resources are distributed so that health services can respond the needs to the population and providing general guidance to the actors of the health sector .
the government can use several tools to influence the governance of the health system : elaboration of policies , allocation of budget , elaboration of quality standards and regulations , and introduction of incentives . in the table below [ table 1 ] ,
examples of governance tools used by governments and their potential impact of the eye health system
health services can be organized in various ways , hence the diversity of health systems in the world .
eye care services can be delivered through the private sector , the not - for profit sector or the public sector , in facilities or in outreach , by eye care professionals or eye care volunteers , through a vertical or horizontal program.[1319 ] the main issue in eye care is access and demand .
access to services and coverage of needs is influenced by the model of service delivery adopted by the country .
this encompasses , for example , the degree of decentralization of the health system ( i.e. , at which level of the health system are decision made ? ) , the geographical distance between health facilities and residents ( e.g. , how many facilities are available per population ? ) , the range of services offered at different levels of the health system ( e.g. , what services are offered by community eye care workers ?
should we train cataract surgeons?),[2124 ] the level of quality of care offered by facilities .
the function of service delivery is under the general responsibility of the ministry of health although service providers , donors and nongovernment organizations ( ngos ) have a key role to play .
the following table [ table 2 ] illustrates the types of decisions that can be taken and their potential impact on the health system .
financing is a key element of the health system and is an issue of how much money should be invested into eye care but also where to allocate the funds to obtain the best value for money .
thus , efficiency and equity are the two objectives of health financing . understanding the financing system of an eye health system consists of identifying the various sources of funding of the health system ( i.e. , taxes , health insurance , user fees , international aid ) and where this money is spent ( i.e. , types of expenses covered ( equipment , maintenance , running costs , consumables , medicine , salaries ) , types of activities covered ( facility - based , eye camps , outreach ) , and type of facility funded ( primary , secondary or tertiary levels ) ) .
understanding how money is allocated by government and which sources of funding are used can be of great interest for organizations on health rights to advocate for better equity in the allocation of resources .
this is also an excellent way of comparing the volume of public spending in eye care compared with other areas of the health sector ( e.g. , hiv aids , malaria ) .
the financing system is governed by all the actors of the eye health system : the users who pay user fees or their insurance premium , the government who collect taxes and redistribute them within the health system , the health providers who collect user fees and receive money from the government and donors and ngos who contribute to the financing of the health system [ table 3 ] .
input management concerns the procurement and supply of medicine , the investment and maintenance of equipment and facilities and the recruitment , training , and deployment of human resources .
the shortage of drugs has been a key factor for under utilization of health services .
this is then essential to ensure that the supply chain of drugs is not interrupted and the quality of medicine is guaranteed ( e.g. , respect of cold chain , monitoring of expiry dates ) . in terms of management of human resources , the areas that need to be considered : the number of eye care professionals and the profile needed in relation to the needs of the population and the country , the volume of the active workforce and its distribution in the country , and the number and profile of eye care professionals leaving the system ( retirement or emigration ) . in the table below , a few examples of strategies are listed to understand how they can have an impact on the health system [ table 4 ] .
strengthening health systems requires a wide range of skills not only to be able to table issues in various areas ( e.g. , governance , management , finance ) but also to be able to collaborate with diverse actors that have different agendas and priorities .
health system strengthening is a complex intervention that requires a good understanding of how the eye health system functions and how the eye health system is connected with the general health system . in 2012 ,
innovations were introduced in eye care with the elaboration of the eye health system assessment guidelines to help policy makers evaluate the capacities of the eye health system and the level of integration of eye care into the general health system .
however , further efforts and investments are needed to explore the structure of eye health systems and generate evidence on the impact of diverse health system strengthening interventions . in a global effort , academics need to continue to inform policy makers and program managers on evidence available and guide them on how to document their results .
in contrast , national eye health authorities and international actors need to experiment and test various interventions and feed academics with data .
 understanding health systems have now become the priority focus of researchers and policy makers , who have progressively moved away from a project - centred perspectives . 
 the new tendency is to facilitate a convergence between health system developers and disease - specific programme managers in terms of both thinking and action , and to reconcile both approaches : one focusing on integrated health systems and improving the health status of the population and the other aiming at improving access to health care . 
 eye care interventions particularly in developing countries have generally been vertically implemented ( e.g. trachoma , cataract surgeries ) often with parallel organizational structures or specialised disease specific services . with the emergence of health system strengthening in health strategies and in the service delivery of interventions 
 there is a need to clarify and examine inputs in terms governance , financing and management . 
 this present paper aims to clarify key concepts in health system strengthening and describe the various components of the framework as applied in eye care interventions . 
What is a Health System?
Examining Eye Care Programs in the Context of Health Systems
Governance
Service Delivery
Financing
Input Management
Health System Strengthening: A Paradigm Shift