Disability is a physical and mental impairment that hinders the performance of daily activities and interaction with others.¹⁾ Diverse types of disabilities have been noted depending on the area of the disorder, including physical, hearing, vision, brain lesion, and intellectual disabilities.²⁾ In 2021, the World Health Organization estimated that over 1 billion individuals live with some type of disability.³⁾ Based on a randomized telephone survey of non-institutionalized United States (U.S.) adults, Okoro et al. (2018) have reported that 25.7% of adults in the U.S. suffer from some type of disability.⁴⁾ Furthermore, the authors found that the prevalence of disability increased with age: 16.6% in those aged 18-44 years, 28.6% in those aged 45-64 years, and 41.7% in those aged ≤65 years.⁴⁾ According to the 2020 statistics from the Korean Ministry of Health and Welfare, 5.1% of the total Korean population was registered with disabilities. Among these, hearing impairment (HI) and visual impairment (VI) are the second and third most common types of disabilities, impacting 15.0 and 9.6% of individuals, respectively.⁵⁾

People with VI and HI reportedly struggle with cognition issues, such as difficulties in understanding and communicating, which is one of the assessment domains of the World Health Organization Disability Assessment Schedule (WHODAS) 2.0, a generic instrument for measuring health and disability.^6,7) People with VI experience difficulties in daily life owing to reduced vision and blindness, which impede walking and reading documents.⁸⁾ In addition, VI is associated with challenges in overall health task performance, such as recalling health information and complying with multidrug therapy.⁹⁾ Individuals with HI experience difficulties understanding other people’s speech and communicating their opinions due to hearing loss.¹⁰⁾ Importantly, communication problems with healthcare professionals can present barriers to safe and effective healthcare delivery.¹¹⁾ Thus, VI and HI can negatively affect the use of healthcare services and drug administration, decreasing medication adherence. Nonadherence is related with negative health outcomes. In patients with diabetes, those with low adherence was associated with difficulty in glycemic control, more hospitalization, and higher medication costs.¹²⁾ In another study, atherosclerotic cardiovascular disease patients that were nonadherent to statins had higher risk of all-cause mortality.¹³⁾

VI and HI are often associated with aging rather than congenital defects.^14-16) As the aging population increases, the prevalence of VI and HI is expected to grow. In Korea, along with the aging population, the proportion of individuals with disabilities aged 65 or older has increased from 37.1% in 2010 to 49.9% in 2020. Among the elderly with disabilities, the most common type is physical impairment (47.9%), followed by HI (23.5%), brain lesion impairment (10.8%), and VI (10.1%).¹⁷⁾ Aging is a major risk factor for most chronic diseases, increasing the need for pharmaceutical intervention.¹⁸⁾ Accordingly, individuals with VI or HI are more likely to take medication, often necessitating multidrug regimens. Thus, identifying the types of obstacles encountered by individuals with VI and HI during drug administration could improve the appropriateness of healthcare utilization and health outcomes.

This systematic literature review of previous studies summarized the available evidence on barriers to safe and effective medication encountered by individuals with VI and HI. Furthermore, it compared how barriers differed between the two types of sensory disorders and attempted to propose disability-specific strategies to alleviate barriers. The study results are anticipated to help improve the health outcomes of individuals with VI and HI by facilitating safe and effective drug use.

Search strategy

Two reviewers (JL and NK) searched studies up to December 31, 2022, in Ovid Medline, EMBASE, and Cochrane scientific databases. No limits were set on the year of publication, to retrieve all studies associated with the review’s question regardless of when they were conducted.

To avoid limited or irrelevant search results when using mapping terms, instead of MeSH terms and Emtree terms, combinations of the following keywords were used to search studies regarding barriers to safe and effective medication in patients with VI: (“blindness” OR “visually impair*” OR “visual impairment*” OR “vision loss” OR “vision disorder” OR “vision defect” OR “sight loss”) AND (“barrier*” OR “challenge*” OR “problem*” OR “difficult*” OR “limit*” OR “misuse*” OR “error*” OR “accident*” OR “safety” OR “side effect*” OR “adverse event*” OR “adverse effect*” OR “adverse drug reaction*” OR “ADR” OR “adherence” OR “compliance” OR “literacy”) AND (“medication*” OR “medicine*” OR “pharmac*” OR “drug*”).

The same search strategy was established for patients with HI as in those with VI, except for keywords indicating HI: “deaf*” OR “hearing impairment*” OR “hearing loss” OR “hearing disorder*.” The search results were pooled using bibliographic software (Endnote 20; Clarivate Analytics, Philadelphia, USA), and duplicates were eliminated.

Inclusion and exclusion criteria

A two-step study selection was performed according to predefined inclusion and exclusion criteria. After duplicate removal, the two reviewers (JL and NK) independently screened the titles and abstracts for eligibility criteria. Subsequently, the full manuscripts of studies that potentially met the inclusion criteria were evaluated to determine final inclusion. Any disagreements between reviewers were resolved by reaching a consensus through mutual discussion.

Criteria for inclusion and exclusion in the qualitative analysis were as follows:

• Studies examining barriers or difficulties in managing medication in individuals with VI or HI were included.

• The included studies reported safety outcome measures, such as medication and/or communication errors, in individuals with VI or HI.

• Studies dealing with the side effects of a study drug in individuals with VI or HI were excluded.

The study design was not limited to comprehensive qualitative synthesis, therefore included reviews, case reports, interviews, surveys, and case-control studies. Studies were excluded if both reviewers agreed that they did not meet eligibility criteria. In addition, studies were excluded if they were not specific to individuals with VI or HI. Duplicate studies and studies for which full-text articles were unavailable were excluded. The design and manuscript of this systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.¹⁹⁾

Qualitative synthesis

We conducted a qualitative synthesis for the included studies. From the findings from the included studies, each of the two reviewers (JL and NK) independently drew themes and concepts about types of barriers to safe and effective medication encountered by individuals with VI and HI. Then, a consensus was made between reviewers through mutual discussion.

Characteristics of Included Studies

Figures 1 and 2 present strategies used to identify relevant studies. After screening studies that met the inclusion and exclusion criteria, 20 and 17 studies were included in the qualitative analysis for individuals with VI and HI, respectively (Figs. 1-2). Table 1 summarizes the main characteristics of each study of individuals with VI. The articles were published between 2009 and 2022 (Table 1). Six studies were conducted in the U.S., three in Scotland, two in South Korea, and others in various countries, including the United Kingdom (UK), Iran, Thailand, Brazil, Columbia, Malaysia, Saudi Arabia, and Switzerland. Most studies (15/20) identified the difficulties in taking medication for patients with VI through interviews or questionnaire surveys (Table 1). Two were studies on application development for individuals with VI^25,28): one was a systematic review article,²⁷⁾ one was a casecontrol study,³²⁾ and one was a case report.³⁰⁾

Table 1

Characteristics of included studies

Authors (year of publication)	Country of the study conducted	Study population: No. subjects	Study methods
Studies regarding visual impairment
Nagarajan et al. (2022)20)	U.S.	Those with VI: 1,921	Survey
Madrigal-Cadavid et al. (2020)21)	Columbia	Those with VI: 48	Interview
Almukainzi et al. (2020)22)	Saudi Arabia	Those with VI: 215	Survey
Smith et al. (2019)23)	Scotland	Those with VI: 5 Those with VI or HI: 12	Interview
Lee et al. (2019)24)	South Korea	Those with VI: 114 Pharmacists: 36	Survey
Nedovic et al. (2019)25)	Switzerland	N/A	Application development planning
Alhusein et al. (2019)26)	Scotland	Pharmacists and pharmacy staffs: 17	Survey
Killick et al. (2018)27)	UK	Studies relevant to those with VI or HI	SR
Farhadyar et al. (2018)28)	Iran	N/A	Application development planning
Alhusein et al. (2018)29)	Scotland	Those with VI: 5 Pharmacists: 30	Survey
Zhi-Han et al. (2017)9)	Malaysia	Those with VI who have used 2 or more drugs within the last 2 weeks: 100	Interview
Gerstein et al. (2017)30)	USA	A 77-year-old man with VI	Case report
Koo et al. (2016)31)	South Korea	Those with VI living in Seoul: 7	Interview
McCann et al. (2012)32)	UK	Those with VI: 156 Those without VI (control): 158	Case-control study
Sansgiry et al. (2012)33)	U.S.	Those with VI: 6	Interview
Hennessy et al. (2011 )34)	U.S.	Those with sight loss (glaucoma, retina): 409	Survey
Hennessy et al. (2010)35)	U.S.	Patients with glaucoma: 204	Survey
Harrison et al. (2010) 36)	U.S.	Women with VI: 15	Interview
Pagliuca et al. (2009)37)	Brazil	Those with VI managing their children’s medicines: 2	Interview
Riewpaiboon et al. (2009)38)	Thailand	Those with VI: 86	Interview
Studies regarding hearing impairment
Garg et al. (2021)39)	India	Studies relevant to those with HI in COVID-19	SR
Dagnachew et al. (2021)40)	Ethiopia	Those with HI: 3, with VI: 6, with PI: 6	Interview
Jacob et al. (2021)41)	Malaysia	Deaf or HoH adults aged ≤ 18 years: 10	Focus group discussion
Gur et al. (2020)10)	Turkey	High school students with HI: 88	Survey
Smith et al. (2020)42)	Ireland	Primary care physicians: 172, secondary care providers: 100	Survey
Alhusein et al. (2019)26)	Scotland	Pharmacists and pharmacy staffs: 17	Survey
Smith et al. (2019)23)	Scotland	Those with HI: 5 Those with VI and HI: 12	Interview
Killick et al. (2018)27)	UK	Studies relevant to those with VI or HI	SR
Alhusein et al. (2018)29)	Scotland	Those with HI: 5 Pharmacists: 30	Interview, survey
Kim et al. (2017)43)	South Korea	Adults with HI: 6	Interview
Hyoguchi et al. (2016)44)	Japan	Those with HI: 20, HoH: 19, non-HI: 20	Survey
Ferguson et al. (2015)45)	USA	Deaf/HoH patients ≤18 years old using at least two long-term prescription medications and using ASL as a primary method of communication.: 20	FGI
Ferguson et al. (2015)45)	USA	Deaf/HoH patients ≤18 years old using at least two long-term prescription medications and using ASL as a primary method of communication.: 20	FGI
Sheppard et al. (2014)46)	USA	Those with HI aged 21 to 62 years: 9	Interview
Holmes et al. (2014)47)	UK	Hospital staffs: 20 Those with HI: 33	Survey
Reeves et al. (2005)48)	UK	Those with HI: 98	Interview
Iezzoni et al. (2004)49)	USA	Adults with deafness: 14 HoH adults: 12	Interview
Steinberg et al. (2002)50)	USA	Women with deafness: 45	Interview

ASL, American sign language; FGI, focus group interview; HI, hearing impairment or hearing impaired; HoH, hard-of-hearing; N/A, nothing applicable; PI, physical impairment; SR, systematic review; VI, visual impairment or visually impaired.

Fig. 1. Flow chart for identifying relevant studies examining individuals with visual impairment.

Fig. 2. Flow chart for identifying relevant studies examining individuals with hearing impairment.

Table 1 also summarizes the main characteristics of the included studies assessing individuals with HI. The articles were published between 2002 and 2022. Four studies were conducted in the U.S., three in Scotland, three in the UK, and one study each in Japan, Turkey, Ireland, Malaysia, Ethiopia, India and South Korea. Interviews and surveys were the most common study methods, performed in 15 out of 17 studies (Table 1). To explore various perspectives, we also included studies investigating parents with VI or HI managing their children’s medication, community pharmacists, and pharmacy staff.

Types of Medication Barriers for Individuals with VI

Based on the results of selected studies, the difficulties encountered by individuals with VI in taking their medications were classified into six categories: 1) drug identification, 2) medication management (opening, preparation, storage, and disposal), 3) pharmacy access, 4) medication instructions (dosage and timing), 5) drug information (labeling), and 6) communication.

Table 2

Types of barriers to medication among individuals with visual impairment

Types of barriers	Source	Severity/Congenital or acquired	Detailed problems
Drug identification	Almukainzi et al., 202022)	Blindness/Congenital	- They identify drugs by size, tactile (surface roughness), or smell. - They attach Braille or tactile markings to identify drugs.
	Lee et al., 201924)	-	Common methods of drug identification: separate storage in recognizable containers (46%), help from family or caregivers (26.5%), no other means (17.7%), recognizable markings (7.1%), and use of Braille (2.7%)
	Killick et al., 201827)	-	Most individuals with VI have trouble identifying drugs.
	Farhadyar et al., 201828)		When developing a medication management application for those with VI, functions that identify pills and organize a list of medications would be helpful.
	Koo et al., 201631)	1st grade, 2nd grade/congenital and acquired	- It is difficult to distinguish between breakfast and lunch pills unless distinct packages are employed. - If the pill package is extremely thin, those with VI sometimes accidentally tear more than one package simultaneously and overdose.
	Riewpaiboon et al., 200938)	-	- Common methods of drug identification: memorize the medicine package (51.2%), seek help from others (17.4%), keep medicines in different locations (11.6%), and label the package (5.8%). - Change in the brand or appearance of a previously prescribed drug can hinder identification for those with VI.
Medication management (opening, preparation, storage, and disposal)	Almukainzi et al., 202022)	-	Considering the identification of medicine expiration date, 90% of the survey participants depended on their caregivers, 8% did not know the expiration date, and 2% estimated it themselves.
	Nedovic et al., 201925)	-	When developing a medication management application for those with VI, text notification service and expiration date reminder function should be considered.
	Killick et al., 201827)	-	- Among the various dosage forms, liquid and ear/eye drops were rated the most difficult to use. - 75% of interviewees did not know the expiration date of their medication. - 58% were unable to name their medication. - 72% did not know how to store their medications appropriately.
	Zhi-Han et al., 20179)	Congenital and acquired	- The most difficult dosage forms to handle were eye/ear drops and liquid drugs, whereas pills and capsules were relatively easy to handle. - 13% of interviewees expressed difficulty opening the medicine container.
	Koo et al., 201631)	1st/2nd grade/congenital and acquired	- It can be difficult to handle tiny pills that stick to the hand, fall to the floor, and are lost.
	Pagliuca et al., 200937)	-	When parents with VI administer liquid medications to their children, they pour the medicine into a disposable cup and measure the appropriate amount by touching it with their hands.
Access to pharmacy	Nagarajan et al., 202220)	-	- Due to COVID-19 pandemic, 51% of the respondents were concerned that they would not be able to get to the pharmacy to get needed healthcare supplies/prescriptions. - 83% were concerned about touching objects in public such as elevator panels, self-serve kiosks, or restroom doors to check signage, while 63% were not sure how to maintain appropriate social distance (staying 6 feet apart from others) in public.
	Koo et al., 201631)	1st/2nd grade/congenital and acquired	- To procure prescription drugs, those with VI can only use a pharmacy with high accessibility, such as a pharmacy located immediately next to the hospital they visit. - It can be difficult to visit a pharmacy independently. - From the perspective of those with VI, it would be better to sell common OTC drugs at convenience stores.
Medication instructions (dosage, dosing interval)	Almukainzi et al., 202022)	Blindness/congenital	Regarding dose, time, diet, and drug interactions, 92% of the survey participants depended on others, 5% said it was impossible to collect information, and 2% depended on presumption.
	Lee et al., 201924)	-	- It is difficult to take the right dose of drugs at a set time. - It is difficult to obtain information on the side effects and expiration dates of medicines.
	Nedovic et al., 201925)	-	An application function or phone/text guidance is required to provide reminders regarding the time and dosage of medicines to those with VI.
	Killick et al., 201827)	-	Many of those with VI rely only on memory for medication instructions.
	Farhadyar et al., 201828)	-	When developing a medication guidance application for those with VI, it is necessary to include a dosing alarm and reminder function.
	Zhi-Han et al., 20179)	Congenital and acquired	Those taking multiple drugs simultaneously are unaware of the dosage of each drug.
	Riewpaiboon et al., 200938)	-	Most individuals with VI rely on memory for dosage and dosing intervals.
Drug information (labeling)	Madrigal-Cadavid et al., 202021)	-	It is difficult to access information on drug labels (e.g., dose, complex formulations)
	Nedovic et al., 201925)	-	- Braille and font size laws are needed for label recognition to assist those with VI. - A label is needed to help those with VI identify drug packages.
	Sansgiry et al., 201233)	-	- Labels for OTC drugs are difficult to read. - Most individuals with VI depend on family members or use assistive devices (e.g., Braille, voice recorders) to obtain information regarding medicines.
	Riewpaiboon et al., 200938)	-	64% of the interviewees expressed the need for a drug label in Braille.
Communication	Almukainzi et al., 202022)	Blindness/congenital	Although Braille was considered the most effective way to communicate drug information, 11% of participants could not read Braille.
	Lee et al., 201924)	-	Although pharmacists and doctors (61.6%) are the main drug information sources, only 22.2% of the pharmacists used Braille for medication guidance.
	Killick et al., 201827)	-	- Misunderstanding by pharmacy staffs that blind people can read drug labels Although most (91%) survey participants used Braille, only 18% received a Braille label with their medication.
	Koo et al., 201631)	1st/2nd grade/congenital and acquired	- Insufficient explanation regarding the side effects of the medication by pharmacists. - High demand for asking questions to pharmacists to acquire drug information. - Lack of trust in pharmacists
	Harrison et al., 201036)	Blindness	- Unable to read the document that must be filled to inform healthcare providers of their information. - Individuals had a negative experience, in which the response of medical providers was unkind. - Medical providers do not know how to dispense medical information to those with VI. - If personal information is read aloud, privacy is not secured.
	Riewpaiboon et al., 200938)	-	80.9% of the interviewees expressed the need for friendly services for those with VI.

OTC: over-the-counter, VI: visually impaired or visual impairment

Drug identification

Six studies reported that most patients with VI had difficulty identifying drugs^{22,24,27,28,31,38)} and distinguished drugs by checking the size or roughness of the drug surface using sensory perception, such as touch and smell. A study surveying patients with VI in South Korea investigated how individuals identified their medications. The most common response was to keep medicines in recognizable containers (46%), followed by assistance from family members or caregivers (26.5%), no other way (17.7%), attaching a palpable label (7.1%), and reading Braille (2.7%).²⁴⁾

According to a study assessing 86 participants with VI in Thailand, the most frequently used method for identifying medicines was self-management by memorizing the medicine package (51.2%), followed by seeking help from others with normal vision (17.4%), storing medicines in different locations (11.6%), and placing a mark on the packages (5.8%). Distinguishing drug appearance by tactile sense is an extremely common practice employed by individuals with VI to identify drugs. Hence, if a pharmaceutical company changes the appearance of existing pills or packages, it will be challenging for individuals with VI to identify drugs, raising concerns regarding safe drug administration.³⁸⁾

Medication management

Among the various dosage forms, liquids and ear/eye drops are the most difficult to administer for individuals with VI, as accurate dose measurement can be challenging.^9,27) A study from Brazil reported that when parents with VI manage their child’s liquid medication, they usually measure the dose by pouring it into a disposable cup, subsequently touching the measured drug.³⁷⁾

Two studies reported how individuals with VI manage drug expiration dates. A Malaysian study found that 75% of interviewees with VI (n=100) did not know the expiration date of their medications, while 58% were unable to name their medication. In addition, 72% of participants lacked knowledge of appropriately storing their medication.^9,27) According to a survey performed in Saudi Arabia, the majority (90%) of respondents (n=215) depended on caregivers for information regarding the drug expiration date, 8% did not know the expiration date, and the rest estimated the possible date.²²⁾

A study from Malaysia investigated the types of problems encountered by individuals with VI for self-management of medications. Of the 100 interviewees, 13% answered that they sometimes could not open the medicine container and 76% had stored unnecessary medications.⁹⁾

Pharmacy access

One qualitative interview study of seven patients with severe VI reported that they could fill a prescription independently if the pharmacy was located immediately next to or on the ground level of the hospital they visited. Otherwise, it would be extremely difficult for them to procure the drugs by themselves; hence, they suggested that it would be helpful to sell common over-thecounter drugs at convenience stores that are easily accessible.³¹⁾

A survey with American adults with vision loss was conducted to measure the concerns on healthcare access due to COIVD-19 pandemic in the U.S. Due to the pandemic, 51% of the respondents were concerned that they would not be able to get to the pharmacy for the needed healthcare supplies/prescriptions. Eighty-three% were concerned about touching objects in public such as elevator panels, self-serve kiosks, or restroom doors to check signage, while 63% were not sure how to maintain appropriate social distance (staying 6 feet apart from others) in public. ²⁰⁾

Medication instructions

Several individuals with VI solely relied on their memory of medication instructions and often forgot to take their drugs.²⁷⁾ It can be difficult to accurately determine the prescribed dose when self-medication is based on memory alone.^9,22) In another interview study regarding drug instructions such as time to take drugs, food requirements, and drug interactions, 92% of the participants depended on others to obtain this information, 5% were unable to recognize any information, and 2% relied on presumption.²²⁾ In an interview study in Thailand, 77.4% of the participants requested that pharmacists provide additional explanations regarding medication instructions for those with VI.³⁸⁾

Drug information: labeling

For individuals with VI, it can be difficult to access information on drug labels.²¹⁾ A study by Sansgiry et al. reported that most people with VI depended on family members or used assistive devices (e.g., Braille or voice recorders) to obtain drug information.³³⁾ Approximately 64% of interviewees with VI expressed the need for a drug label in Braille.³⁸⁾ A study in Switzerland insisted that it is necessary to enact legislation on Braille, font size, and color combinations for drug packages to help individuals with VI read drug labels.²⁵⁾ In addition, in two studies on developing a medication management application for individuals with VI, participants stated that the potential application should be able to assist in obtaining drug information to increase medication compliance.21,²⁵⁾

Communication

For individuals with VI, communication challenges can stem from them, as well as from healthcare professionals and healthcare systems. Unless assistive devices such as Braille are provided, individuals with VI will be unable to read a document that must be filled to inform healthcare providers regarding pertinent information. In addition, they cannot read referral information regarding healthcare providers to receive professional help.³⁶⁾ Although Braille has been considered the most effective communication method for drug information, a survey in Saudi Arabia revealed that 11% of respondents with VI could not read it.²²⁾ On examining the ability of individuals with VI to read Braille, it was found that only 5.1% of individuals with blindness were able to read Braille, while 93.4% were unable to read it.⁵¹⁾

Several studies have revealed that individuals with VI failed to obtain sufficient information and services from healthcare professionals. According to Lee et al. (2019), individuals with VI mainly obtain drug information from pharmacists and doctors (61.6%), the internet (17.9%), television or radio (10.7%), and family members (9.8%). Although healthcare providers are the main sources of drug information among individuals with VI, pharmacy staff have a low awareness of their pharmaceutical care needs.²⁴⁾ Based on an interview study, although 86.5% of the participants answered that using Braille was the most effective way to communicate drug information, only 18% of patients received medicines in Braille.²⁷⁾ Another study reported that 76% of participants had never received drugs with Braille markings.²²⁾

The lack of sufficient communication with healthcare providers can result in distrust of medical personnel and services. Especially in large pharmacies, as the service time per patient is limited, it is difficult to provide sufficient counseling to patients with VI. Several interviewees with VI shared experiences where the pharmacist seldom explained drug information sufficiently, necessitating repeated questioning for additional information.³¹⁾ Another study provided detailed examples of negative experiences and lack of trust in pharmacy services among individuals with VI; study participants stated that healthcare providers did not know how to provide medical information to individuals with VI. Moreover, they were concerned about the invasion of their privacy when healthcare providers would read aloud personal information such as treatment information.³⁶⁾

Types of Medication Barriers for Individuals with HI

Based on the selected studies, the types of difficulties encountered by individuals with HI when using medications were classified into three categories: 1) communication, 2) health literacy, and 3) negative experiences and emotions toward doctors/pharmacists.

Table 3

Types of barriers to medication for individuals with hearing impairment

Types of barriers	Source	Severity/Congenital or acquired	Detailed problems
Communication	Garg et al., 202139)	-	- Personal protective equipment (PPE) kits worn by health workers make communication between health workers and hearing impaired difficult in COVID-19 pandemic.
	Dagnachew et al., 2021 40)	Deaf	- HIs have never met a pharmacist at community pharmacy who can understand sign language, and there was no one around to interpret. - Local pharmacies lack brochures or posters to support communication with people who were not able to speak.
	Jacob et al., 202141)	Deaf, HoH	Approximately 70% of individuals with HI experienced errors in communication with pharmacists.
	Killick et al., 201827)	-	Relying only on written information can result in ineffective communication, as important information can be omitted, and the individuals with HI have difficulty understanding written material.
	Kim et al., 201743)	Deaf, HoH	- Purchasing OTC can be extremely inconvenient due to poor communication with pharmacists. - It is practically impossible to ask questions to pharmacists - It can be severely challenging to obtain desired information by telephoning the pharmacy. - There are no pharmacies with sign language interpreters for those with HI. - If instructions regarding medications are not written on paper, it can be difficult to take the medication.
	Ferguson et al., 201545)	Deaf, HoH	To avoid communicating with the pharmacy staff, individuals with HI order their medications online.
	Sheppard et al., 201446)	Deaf	- Doctors often surrender to providing sufficient information after failing to communicate adequately using writing notes. - Reading facial expressions to understand the other person's speech can be hindered by the “poker face” maintained by the medical professional.
	Reeves et al., 200548)	Deaf	When a physician does not face those with HI, covers his/her mouth while speaking, or speaks extremely fast, it is difficult to understand his/her language.
	Iezzoni et al., 200449)	Deaf, HoH	If physicians speak quickly, turn away, or wear a mask, individuals with HI have difficulty lip reading.
	Steinberg et al., 200250)	Deaf	- Owing to a poor understanding of the speech of healthcare providers, those with HI are often unaware of the kind of tests they underwent or what drugs they are prescribed.
Health literacy	Ferguson et al., 201545)	Deaf, HoH	- The contents in the written pamphlets are too lengthy and complicated to understand. - A patient with HI drove a car after taking a medicine that does not permit driving post-medication, as the patient had not been properly guided and informed.
	Reeves et al., 200548)	Deaf	Written drug information is too professional and lengthy to understand.
	Steinberg et al., 200250)	Deaf	- Lack of knowledge on healthcare and prescribed drug efficacy and side effects. - Although they had insurance, only 63% had received breast examination, Pap smear, or pelvic examination, and 47.4% had undergone mammography, owing to poor health literacy.
Negative experiences and emotions toward doctors/pharmacists	Jacob et al., 202141)	Deaf, HoH	Felt anxious when visiting the pharmacy alone.
	Killick et al., 201827)	-	- Pharmacists failed to provide any special information. - As the pharmacy staff calls the patient by their names, they have to wait for a long time.
	Kim et al., 201743)	Deaf, HoH	- They had low expectations regarding the pharmacist’s professionalism, as pharmacists dispensed medicines without even listening to the detailed symptoms. - Drug service requests tailored to patient characteristics were rejected.
	Sheppard et al., 201446)	Deaf	They missed their appointment slot when their name was called at hospitals and pharmacies.
	Reeves et al., 200548)	Deaf	- Doctors failed to explain the illness to patients properly and rushed through explanation, rendering it difficult to understand. - Given a lack of proper communication, individuals with HI worry that they will receive the wrong treatment.
	Iezzoni et al., 200449)	Deaf, HoH	- Healthcare professionals lack understanding and consideration for those with HI. - Poor explanation regarding the examination makes those with HI uncomfortable and anxious. - Patients with Hi are often called by name, resulting in missed appointment slots.

HI: hearing impaired, HoH: hard-of-hearing

Communication

Most difficulties encountered by individuals with HI are associated with communication problems. Several patients with HI communicate by reading lips or facial expressions. However, according to Sheppard et al. (2014), it can be difficult to read the facial expressions of medical staff, as they tend to maintain a “poker face”.⁴⁶⁾ In addition, according to Iezzoni et al. (2004), masks worn by healthcare providers hindered lip reading.⁴⁹⁾ If healthcare providers do not face individuals with HI, cover their mouths while speaking, or speak extremely rapidly, it can be difficult for those with HI to understand their speech.⁴⁸⁾

Although individuals with HI pursue thorough information regarding their health and medical services, healthcare providers often tend to quit providing more comprehensive information to patients with HI after attempting to communicate by writing notes.⁴⁶⁾ According to Killick et al. (2018), it is generally believed that handwritten notes are an effective strategy for communicating with patients with HI. However, in reality, when healthcare providers use handwritten notes for patients with HI, important information is possibly omitted owing to time constraints. Despite receiving printed information regarding their medication, it can be difficult for individuals with HI to comprehensively understand the stated information. Given these communication challenges, individuals with HI often lack knowledge regarding what examinations they receive or what kind of medicines they take.²⁷⁾ According to Jacob et al. (2021), 70% of individuals with HI experience medication errors because of a lack of appropriate communication with pharmacists.⁴¹⁾ Similarly, there was a lack of brochures or posters that would support communication with those who were not able to speak.⁴⁰⁾ Ferguson et al. (2015) reported cases in which individuals with HI ordered drugs online to avoid communicating with pharmacists.⁴⁵⁾ In particular, in the context of COVID-19, personal protective equipment (PPE) kits worn by health workers made communication between health workers and hearing impaired difficult.³⁹⁾

An interview study by Kim et al. (2017) reported that individuals with HI experienced inconvenience when purchasing over-thecounter medicines, given the barriers in communication. These individuals mentioned that it could be practically difficult to obtain the drug information they desired by calling the pharmacy. In addition, no pharmacies with sign language translators were available to individuals with HI. If only verbal instructions are provided to individuals with HI, it can be difficult to use the medication appropriately. Thus, an easy and detailed description of drug information is crucial for individuals with HI.⁴³⁾

Health literacy

Communication problems among individuals with HI can lead to low health literacy, which several studies have addressed. According to Reeves et al. (2005), despite providing drug information by text, patients with HI do not understand the drug efficacy and safety, as the words used are often extremely lengthy and comprise professional jargon.⁴⁸⁾ Similarly, Ferguson et al. (2015) reported that patients with HI tried to obtain information through written pamphlets, but the words used were remarkably lengthy and complicated.⁴⁵⁾

Based on a study by Steinburg et al. (2002), we learned that patients with HI lack healthcare knowledge and understanding of the efficacy and side effects of prescribed drugs. Moreover, they were unaware of the purpose and necessity of health checkups. Among individuals with HI who had health insurance, only 63% had undergone breast examination, Pap smear, or pelvic examination, and 47.4% had undergone mammographic examination.⁵⁰⁾

Negative experiences and emotions toward doctors and pharmacists

Individuals with HI often have negative experiences when using healthcare services. Announcing their names at hospitals and pharmacies to inform them of their appointment slot can be one of the most frustrating experiences. Despite providing prior notification regarding their condition, patients with HI experienced prolonged waiting times because they missed their appointment when called by name.^27,46,49)

According to Killick et al. (2018), patients with HI do not receive sufficient information regarding their medication from pharmacists and hence perceive pharmacists as people who simply dispense medicines.²⁷⁾ In addition, Iezzoni et al. (2004) reported that medical personnel lack understanding and consideration for individuals with HI. There were several instances where patients with HI felt discomfort and fear owing to a lack of explanation regarding the examination.⁴⁹⁾ Similarly, another opinion stated that doctors did not explain the illness to patients properly and rushed through the explanation, rendering it difficult to understand.⁴⁸⁾ Some individuals felt anxious that they would receive the wrong treatment owing to miscommunication.⁴¹⁾ According to Kim et al. (2017), patients with HI had low expectations for the pharmacist’s professionalism, as they dispensed medicines without listening to the detailed symptoms. These negative emotions may result in reduced medication effectiveness.⁴³⁾

The present systematic review derived evidence regarding difficulties and obstacles experienced by individuals with VI or HI during drug therapy. We identified 37 studies addressing this issue worldwide, including 20 and 17 studies on individuals with VI and HI, respectively. Qualitative analyses of selected studies indicate that patients with VI experience difficulties in the entire process of receiving drug therapy: receiving prescriptions from hospitals, filling prescriptions at pharmacies, and taking, storing, and disposing of medicines. However, patients with HI have difficulty communicating with healthcare providers at hospitals and pharmacies. Difficulties common to both disabilities include poor communication and a lack of drug information. The healthcare environment has changed rapidly. However, our study showed that obstacles related to the safe use of drugs by visually impaired and hearing impaired persons persistently appeared during the study period of almost two decades. For example, the development and enforcement of regulations on Braille markings on drug containers differ depending on the country surveyed; regardless, policies such as standardization of the contents of braille writing, inspection of contents, and provision of educational programs to improve Braille literacy for people with visual impairment still remain as an unmet demand.

The main problems encountered by patients with VI are pill identification and precise drug administration. Studies have suggested that Braille markings or speaking labels are essential for drug packages. In a cross-sectional study using a questionnaire, 91% of individuals with VI agreed that Braille labeling helped them overcome difficulties and improve the quality of therapy.²²⁾ In another study, after providing Braille prescriptions, which included information on dosage, instruction, expiry date, and adverse effects, the proportion of patients with VI who faced challenges in self-medication was significantly reduced from 73 to 17.5%. In addition, the proportion of those who had taken an incorrect dose decreased from 46.2 to 5%.⁵²⁾ Regarding solutions to improve medication use, individuals with VI stated the need for Braille labeling most frequently (91% of the respondents with VI), followed by Braille written drug use information pamphlets (81%) and packaging with touch differentiable markings (62%).⁵³⁾

However, legal enforcement regarding Braille use differs across countries. In Korea, 16 out of the top 58 over-the-counter drugs by sales (27.6%) had Braille labeling according to the status of Braille labeling surveyed by the Korea Consumer Agency.⁵⁴⁾ In Europe, Braille identification has been mandatory in all drug packaging since 2005, whereas it is not mandatory in the U.S..⁵⁵⁾ Poor Braille readability among individuals with VI can be a barrier to accurately understanding the purpose and efficacy of drug therapy.^24,31,36,51) Therefore, it is necessary to prepare not only a standard guideline for drug packages in Braille and provide Braille education but also establish an identification plan other than Braille for those who are unable to read Braille.

Physical accessibility of pharmacies is crucial for the receipt of medication among those with VI, as they can fill prescriptions independently only if the pharmacy is located near the hospital.³¹⁾ Corridor-type structures in pharmacies can make it difficult for individuals with VI to navigate the pharmacy.^23,26) In addition, the routes must be clear of possible obstacles, and color-contrast lines on the floor or guide rails would be useful for patients with VI to move around the pharmacy. Furthermore, assistance should be provided by pharmacists or staff while patients with VI wait for their prescriptions.⁵⁶⁾

Difficulties and obstacles encountered by patients with HI in terms of medication are mainly communication issues. Typically, written medical information can be an effective strategy for improving patient knowledge regarding drug therapy, such as precautions, side effects, or special directions.⁵⁷⁾ However, low literacy hinders written communication regarding drug information by increasing the risk of misinterpretation; therefore, understanding text data can often be complicated and technical for patients with HI.⁵⁸⁾ Education of individuals with HI on the safe use of medicines needs to be expanded and implemented according to their reading comprehension level, which would increase the chances of safe and effective drug therapy.⁴⁴⁾

Proper use of sign language could help individuals with HI to ensure safe and effective drug use. However, sign language is usually delivered with the help of an interpreter; thus, it can be an expensive endeavor. A study in South Africa revealed that the estimated costs of sign language interpreter service utilization represented 2.3-12.2% of the yearly budget for healthcare services in the Western Cape District.⁵⁹⁾ In the U.S., healthcare providers must provide sign language medical interpreters according to the Americans with Disabilities Act, but only 22% of physicians used sign language interpreters as the first line of communication.⁶⁰⁾ In Korea, 88.4% of individuals with HI wanted to communicate using sign language in hospitals; however, only 3 hospitals deployed medical sign language interpreters, necessitating the independent reservation of an interpreter by the patient.⁶¹⁾ Therefore, additional research is necessary to investigate the most economic and accessible healthcare institutions to deploy professional sign language interpreters.

New and advanced technology should be more actively monitored and introduced to ensure the effective communication of individuals with VI or HI with healthcare providers. Various studies are in progress for assisting drug identification among individuals with VI, such as using audio prescription labeling systems, mobile technology in healthcare delivery known as mHealth, radio frequency identification tags to help identify medications, and a mobile application that provides reminders regarding drug intake (MyPills), indicating that the functions of these technologies can be valuable to individuals with VI.^25,28,62) Mobile applications to aid individuals with HI, such as sign language translation, interpretation, and syntax recognition, will be useful in communicating with doctors and pharmacists.⁶³⁾ Using such technologies would not only help prevent safety issues but also prevent negative health outcomes and financial loss incurred by health insurance due to inappropriate medication use.

Healthcare professionals lack awareness regarding how patients with VI or HI acquire and manage medication instruction information, thereby preventing effective communication with the medical staff during treatment. The Agency for Healthcare Research and Quality (AHRQ) has distributed educational material to local pharmacists to manage individuals with disabilities and provide solutions for pharmacy staff to recognize and communicate with patients with limited health literacy.⁶⁴⁾ Medical textbooks cover the role of healthcare providers as educators, disability-specific communication strategies, and teaching plans.⁶⁵⁾ For the safe use of medications in patients with sensory impairment, systematic training must be provided to clinicians and pharmacists on how to treat patients with VI or HI to overcome communication barriers.^45,6668)

This study had several limitations. First, the selected studies were heterogeneous in several respects; the country where the study was conducted, selection criteria and age distribution of study subjects, the number of study subjects included, and data collection methods all differed across studies. As results of individual studies were drawn from diverse populations, caution should be exercised when generalizing the findings from each study to the entire population with VI or HI. Second, most studies did not distinguish the study subjects according to the time of disability appearance and severity. The types of barriers to medication may differ depending on the degree of disability or whether the disability is congenital or acquired. A subgroup analysis according to the type and severity of VI and HI will help better clarify challenges encountered by these individuals. Visual impairment and hearing impairment are both sensory impairments, and they share a common point of impairment that is closely related to aging as acquired disabilities. However, as we have shown in our results, the two disorders are actually very different in terms of the characteristics of the disorders and the factors that cause them, and the current status of actual drug safety use and related obstacles are also different. An important implication of this research is that we found these differences and, accordingly, raised the need for deriving customized policy improvements according to disability characteristics.

Several types of barriers can hinder the treatment of patients with sensory impairments. Individuals with VI experience difficulties in the entire process of drug therapy, including access to pharmacies and identifying, taking, storing, and disposing of medications. Individuals with HI encounter difficulties communicating with healthcare professionals and present poor health literacy. For the safe and effective medication of individuals with VI and HI, it is essential to understand the types of difficulties encountered by them and establish practical solutions in clinical settings, such as providing tablet identification tools for those with VI, deploying sign language interpreters at designated healthcare institutions and pharmacies for those with HI, utilizing new technologies such as audio prescription labeling systems or mobile applications, and providing education for both healthcare providers and individuals with disabilities to improve their partnership during drug therapy.

This study was funded by the Korea Ministry of Food and Drug Safety (MFDS, grant number: 21082-Gihoikyon704) and the National Research Foundation of Korea (grant number: 2022R1A2B5B0100125311).

The authors have no conflict of interest.