Glaucoma Diagnoses and Legal Blindness from Glaucoma among Bedouin Patients of Central Saudi Arabia: A Hospital-Based Study.

PURPOSE: The current study aims to know the glaucoma diagnoses and legal blindness from glaucoma among a tertiary referral center in Riyadh (King Abdulaziz Medical City [KAMC]-Riyadh patients).
METHODS: This is a retrospective cohort study on chart review, where all eligible glaucoma patients attending the ophthalmology clinic at KAMC-Riyadh, between 2018 and 2019; were included.
RESULTS: A total of 248 patients were included in the study; 142 patients (57.3%) were females and 106 (42.7%) were males. The mean age of the patients was 62.2 ± 18 years and most of them (93.5%) did not have a family history of glaucoma. Nearly one-quarter (26.6%; n = 66) of the included patients were legally blind, out of those, 36.4% had their right eye affected, 34.8% had their left eye affected, and 28.8% had both eyes affected. Legally, blind patients (LBGs) did not show a statistically significant reduction in the intraocular pressure (IOP) in the right eye (P = 0.103), on comparing the IOP in both visits. Nevertheless, there was a statistically significant reduction in the IOP of the left eye among the LBGs in both visits (P = 0.016). Regarding the nonblind group of patients, there were highly statistically significant reductions in both eyes (P < 0.001).
CONCLUSION: The present findings show a high prevalence rate of legal blindness among glaucoma patients, with IOP reduction, age, and glaucoma diagnoses being the most important predictors among the study population. Copyright:

Introduction

Glaucoma is a class of optic neuropathies that manifest as visual field defects, retinal nerve fiber layer thinning, and nonphysiological optic nerve head cupping. Pathological losses of the somas and axons of the retinal ganglion cells represent the main etiology of glaucoma optic neuropathies.[1] Glaucoma is the one of the most common causes of irreversible visual loss around the world.[2] Around 111.8 million people worldwide are estimated to have glaucoma by the year 2040; the majority of them will have primary open-angle glaucoma more than primary angle-closure glaucoma, with most of them being Asian and African.[3] The World Health Organization (WHO) reported that there were 38 million people in the world who were blind as well as another 110 million people who are at great risk of becoming blind. Cataract, trachoma, glaucoma, onchocerciasis, and xerophthalmia were the main factors associated with blindness and low vision. The global prevalence of blindness from other medical causes such as diabetic retinopathy and age-related macular degeneration still had insufficient data.[4]

Patient compliance with medication is important to maintain intraocular pressure (IOP) within the target range to reduce optic nerve axon damage. Patients' compliance with medication can be measured by recording timing, dosage, and frequency. Patients should continue to take prescribed medication according to medical team instructions to maintain the IOP within normal limits.[5] Blindness is the worst complication of glaucoma. According to the WHO criteria, blindness is defined as a presenting visual acuity of <3/60 or a corresponding visual field loss of <10° in the better eye with best possible correction.[6]

In 2009, a hospital-based study showed that glaucoma was prevalent in 18% of patients included from the Western region of Saudi Arabia, with a history of glaucoma in 54% of patients and legal blindness in another half.[7] In 2015, a study at the University Health Center in Al-Ahsa area, Kingdom of Saudi Arabia, showed that the primary open-angle glaucoma was the most common type of glaucoma (60%), followed by primary angle-closure glaucoma (21%).[8] Furthermore, although, a hospital-based study was done in Riyadh city demonstrated that primary angle-closure glaucoma was the most common type of glaucoma (47%), followed by primary angle closure (17%), the study was conducted in 2011.[9] Therefore, with the increasing evidence of the prevalence of glaucoma,[3] and the absence of updated information in this field, the current study aims to identify the glaucoma diagnoses and legal blindness from glaucoma among King Abdulaziz Medical City (KAMC)-Riyadh patients.

Methods

A retrospective analysis was conducted on all medical records of glaucoma patients attending KAMC-Riyadh between 2018 and 2019 to investigate the glaucoma diagnoses, the proportion of legally blind patients (LBGs), and to identify the attributable factors that give rise to legal blindness.

Study setting

KAMC is a tertiary referral center for all Saudi citizens in Riyadh and its surrounding areas (the central province of Saudi Arabia).

Study design and subjects

This is a retrospective cohort study based on chart review, where all eligible glaucoma patients attending the ophthalmology clinic at KAMC-Riyadh between 2018 and 2019 were included. The sample selection was started from October 2019 and continues retrospectively until the required number of patients is achieved.

Data collection

Medical records of the glaucoma patients were retrieved and reviewed using a structured data collection, form which included the following information: gender, glaucoma family history, medical history, number of glaucoma medications, glaucoma medications intolerance, legal blindness, and glaucoma diagnoses as categorical variables and age and IOP as numerical variables. The outcome variables were the common glaucoma diagnoses, risk factors associated with glaucoma, and the percentage of blindness due to glaucoma. Legal blindness will be identified in this study according to the WHO criteria (2018). The International Classification of Diseases 11 (2018) classifies legal blindness as, “a presenting visual acuity of <3/60.”[10]

In the current study, the compliance was defined as how well a patient takes prescribed medication according to the recommended dosing schedule.[1112] The compliance was assessed using the Glaucoma Treatment Compliance Assessment Tool.[13]

Statistical analysis

Mean and standard deviation were used to represent continuous variables, while we used frequencies and percentages to represent categorical variables. The skewness and Kurtosis tests were used for testing the normal distribution of continuous variables. Chi-square test (or Fisher's exact test, as appropriate) was used for categorical data, while the t-test was used for continuous variables normally distributed and the Mann–Whitney U-test was used for continuous variables not normally distributed.

To compare the changes in the IOP between first and last visit using the Wilcoxon signed–rank test, since the IOP data were not normally distributed. Furthermore, we used multivariable logistic regression to identify possible glaucoma-related risk factors for legal blindness. To find the best model, we started with all possible parameters then a forward elimination stepwise procedure was carried out in a way that the factor would be brought into the analysis if the corresponding P < 0.2. Regression results were expressed as odds ratios (ORs) and 95% confidence interval (95% CI). Data were analyzed using R software version 4.0.1 (Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA) using the packages (Rcmdr) and (glm2). The statistical significance was considered when the P < 0.05.

Results

Baseline characteristics of the included patients

A total of 248 patients were included in the study; 142 patients (57.3%) were females and 106 (42.7%) were males. The mean age of the patients was 62.2 ± 18 years and most of them 232 (93.5%) did not have a family history of glaucoma. Regarding different comorbidities, diabetes was the most common with 148 (59.7%), hypertension 131 (52.8%), dyslipidemia 75 (30.2%), ischemic heart disease (IHD) 38 (15.3%), and asthma 37 (14.9%). Meanwhile, other less common comorbidities included benign prostatic hyperplasia 4 (1.6%), stroke 4 (1.6%), end-stage renal disease 4 (1.6%), hepatitis C virus 2 (0.8%), and hypothyroidism 2 (0.8%) [Table 1].

Table 1

Comparison of clinical parameters between legally-blind and nonblind glaucoma patients

Variables	Legally blind			P
	No, n (%)	Yes, n (%)	Total, n (%)
Glaucoma medications compliance
Good	145 (79.7)	50 (75.8)	195 (78.6)	0.098
Poor	13 (7.1)	9 (13.6)	22 (8.9)
No compliance	1 (0.5)	2 (3.0)	3 (1.2)
Not applicable	23 (12.6)	5 (7.6)	28 (11.3)
Glaucoma medications intolerance
Yes	27 (14.8)	6 (9.1)	33 (13.3)	0.388
No	133 (73.1)	54 (81.8)	187 (75.4)
Not applicable	22 (12.1)	6 (9.1)	28 (11.3)
Right eye laser therapy
LPI	82 (45.1)	24 (36.4)	106 (42.7)	0.447
SLT	1 (0.5)	0	1 (0.4)
ALT	0	0	0
No laser done	99 (54.4)	42 (63.6)	141 (56.9)
Left eye laser therapy
LPI	80 (44.0)	27 (40.9)	107 (43.1)	0.820
SLT	2 (1.1)	0	2 (0.8)
ALT	0	0	0
No laser done	100 (54.9)	39 (59.1)	139 (56.0)
Patient glaucoma diagnoses
Primary open angle	41 (22.5)	8 (12.1)	49 (19.8)	0.003*
Primary angle closure	68 (37.4)	21 (31.8)	89 (35.9)
Secondary open angle	42 (23.1)	18 (27.3)	60 (24.2)
Secondary angle closure	18 (9.9)	3 (4.5)	21 (8.5)
Normal tension	5 (2.7)	7 (10.6)	12 (4.8)
Childhood glaucoma	3 (1.6)	7 (10.6)	10 (4.0)
Juvenile glaucoma	5 (2.7)	2 (3.0)	7 (2.8)
Secondary open angle
NVG	0	1 (6.6)	1 (1.8)	0.052
PEX glaucoma	37 (97.3)	13 (86.6)	50 (94.3)
Steroid-induced glaucoma	1 (2.6)	0	1 (1.8)
Traumatic glaucoma	0	1 (6.6)	1 (1.8)
Secondary angle-closure
Aphakic glaucoma	1 (20.0)	0	1 (11.1)	1.000
ICE syndrome	0	1 (2.5)	1 (11.1)
NVG	3 (60.0)	4 (80.0)	6 (66.7)
PEX glaucoma	1 (20.0)	0	1 (11.1)

*,Primary open angle glaucoma was associated with significantly lower risk of legal blindness (p= 0.05), ALT: Argon laser trabeculoplasty, SLT: Selective laser trabeculoplasty, LPI: Laser peripheral iridotomy, NVG: Neovascular glaucoma, PEX: Pseudoexfoliation, ICE: Iridocorneal endothelial syndrome

Baseline data of the LBGs and those with not LBGs (NLBGs) were compared. There was no statistically significant difference in age (P = 0.680) between the LBG and NLBG with 61.9 ± 16.8 and 63.1 ± 21.0 years, respectively. The two groups were also matched with other characteristics showing no significance and that included gender (P = 0.119), family history of glaucoma (P = 0.096), diabetes mellitus (P = 0.770), hypertension (P = 0.391), dyslipidemia (P = 0.639), IHD (P = 0.318), asthma (P = 0.315), and other comorbidities (P = 0.675) [Figure 1 and Table 1].

Figure 1

Baseline data of the legally blind patients and those who are not legally blind patients

Clinical parameters of the included patients

Nearly one-quarter of the included patients were legally blind 66 (26. 6%). The majority of both blind and nonblind patients had good compliance 195 (78.6%). Meanwhile, the majority of both LBG and NLBG were tolerant to glaucoma medication 187 (75.4%). Furthermore, the most common type of glaucoma was primary angle closure 89 (35.9%), followed by secondary open-angle 60 (24.2%) and primary open-angle 49 (19.8%), respectively. Laser therapy (laser peripheral iridotomy and selective laser trabeculoplasty) was performed in 107 (43.1%) of the right eye glaucoma and 109 (44%) of the left eye [Table 1].

Distribution of the affected eyes among legally blind patients (n = 66)

Among the 248 patients, glaucoma medication intolerance was not commonly reported as 54 (81.8%) LBG individual tolerated glaucoma medication and 133 (73.1%) NLBG patient reported no intolerance to glaucoma medication. Overall, LBG and NLBG medication intolerance was not significant (P = 0.388). Regarding medication compliance, 78.6% (n = 195) of the patients showed a good compliance, 22 (8.9%) showed a poor compliance, and 3 (1.2%) did not show any compliance at all. Similarly, 33 (13.3%) of the patients had an intolerance to the glaucoma medications. There was no statistically significant difference among LBG and NLBG in all clinical parameters, except for glaucoma diagnoses (P = 0.003) [Table 1].

The mean IOP in the right eye was 19.3 ± 7.6 at the first presentation and was 16.00 ± 4.9 at the last visit, where the change was statistically significant (P < 0.001). Moreover, the mean IOP in the left eye was 19.55 ± 6.58 at the first presentation and was 16.19 ± 4.81 at the last visit, where the change was statistically significant (P < 0.001). LBGs did not show a statistically significant reduction in the IOP in the right eye (P = 0.103), on comparing the IOP in both visits. Nevertheless, there was a statistically significant reduction in the IOP of the left eye among the LBGs in both visits (P = 0.016). Regarding the nonblind group of patients, there were highly statistically significant reductions in both eyes (P < 0.001) [Figure 2].

Figure 2

The mean intraocular pressure at the first presentation and at the last visit

Risk factors for legal blindness among glaucoma patients

Among different patients' demographics, age was found to be a significant predictor of legal blindness, where older patients were associated with higher risk (OR = 1.04; 95% CI = 1.01–1.06; P = 0.002). There was no statistically significant difference in the risk of legal blindness between males and females (OR = 0.83; 95% CI = 0.42–1.66; P = 0.599). Moreover, childhood glaucoma (OR = 131.46; 95% CI = 13.89–1243.91; P < 0.001) and normal-tension glaucoma (OR = 10.97; 95% CI = 2.18–55.28; P = 0.004) were associated with a significant higher risk of legal blindness, compared to primary open-angle glaucoma [Table 2].

Table 2

Multivariate logistic regression analysis for the risk factors for legal blindness among glaucoma patients

Predictor	Estimate	SE	Z	P	OR	95% CI (lower-upper)
Age	0.04	0.01	3.04	0.002*	1.04	1.01-1.06
Gender
Male	Reference
Female	−0.19	0.35	−0.53	0.599	0.83	0.42-1.66
Glaucoma family history
Negative	Reference
Positive	−1.27	1.24	−1.03	0.304	0.28	0.02-3.17
Patient glaucoma diagnoses
Primary open angle	Reference
Primary angle closure	0.45	0.53	0.85	0.394	1.57	0.56-4.39
Secondary open angle	0.75	0.53	1.43	0.154	2.12	0.75-5.99
Secondary angle closure	−0.12	0.81	−0.15	0.878	0.88	0.18-4.35
Normal tension	2.4	0.82	2.9	0.004*	10.97	2.18-55.28
Childhood glaucoma	4.88	1.15	4.25	<0.001*	131.46	13.89-1243.91
Juvenile glaucoma	1.28	1.02	1.25	0.212	3.59	0.48-26.72
Glaucoma medications compliance
Good	Reference
Poor	0.11	0.57	0.19	0.851	1.11	0.36-3.41
No compliance	2.98	1.75	1.7	0.089	19.73	0.63-613.34
Not applicable	−0.43	1.19	−0.36	0.719	0.65	0.06-6.76
Glaucoma medications intolerance
Yes	Reference
No	0.36	0.54	0.66	0.511	1.43	0.49-4.12
Not applicable	−0.25	1.13	−0.22	0.826	0.78	0.09-7.11
Number of glaucoma medications in last visit
One medication	Reference
Two medications	−0.07	0.95	−0.07	0.944	0.94	0.14-6.04
Three medications	−1.62	0.82	−1.98	0.047*	0.2	0.04-0.98
Four medications	−0.57	1.12	−0.51	0.609	0.56	0.06-5.09

*Statistically significant. SE: Standard error, OR: Odds ratio, CI: Confidence interval

In the same context, using three glaucoma medications was associated with a significant reduction in blindness risk compared to using only one medication (OR = 0.20; 95% CI = 0.04–0.98; P = 0.047). However, results did not show any significant association with glaucoma medications' compliance or glaucoma medications' intolerance as described by Olthoff et al. [Table 2].[14]

Discussion

In the current study, we analyzed the data of all glaucoma patients, meeting the inclusion criteria, who presented to KAMC at Riyadh between 2018 and 2019 to identify the glaucoma diagnoses and legal blindness due to glaucoma. LBG and NLBG patients had matching baseline characteristics, with one-quarter of glaucoma patients being legally blind.

Our results showed that the most common types of glaucoma were primary angle closure (35.9%), followed by secondary open angle (24.2%), and primary open angle (19.8%), respectively. Similarly, Al Obeidan et al. reported that primary angle-closure glaucoma represents the majority of glaucoma cases (46.6%) at a hospital referral center in the central region of Saudi Arabia followed by primary open-angle (12.8%), and secondary (13%) glaucoma.[9] On the other hand, Eid et al. showed that primary open-angle glaucoma recorded the highest prevalence rate (38.1%) followed by primary angle-closure glaucoma (24.7%) in the Western region.[7] Unlike Eid's population which is multiethnic due to the population of the Western province of Saudi Arabia, our data were from the Bedouin of Riyadh (Saudi central province), and this may explain the difference in the most common types of glaucoma. The difference in the prevalence rates between glaucoma subtypes is probably due to the difference between the primary and secondary centers in terms of providing highly qualified ophthalmologists for better detection and management of glaucoma. Moreover, the limited use of advanced equipment in secondary and tertiary centers might be another factor which leads to underestimation of the true numbers. The prevalence of pseudoexfoliative glaucoma in the study population was highest with secondary open-angle glaucoma (87.7%), while only one case (8.3%) occurred with secondary angle-closure glaucoma. Al-Saleh et al. reported a prevalence rate of 3.5% for pseudoexfoliative glaucoma in a primary care clinic in Riyadh, Saudi Arabia.[15] In India, the estimated rate was higher being 20% as reported by Rao et al.[16] Moreover, our results are consistent previous studies which found that primary angle-closure was higher in the Asian population with over 80% of the patients within Asia.[1718] A previous systematic review found that the overall prevalence of the primary angle closure was 0.75%, with a prevalence rate of 0.97% among Middle Eastern population, 0.66% in southeast Asians, 0.46% in Indians, 1.10% in Chinese individuals, and 1.19% in the Japanese population.[17] In the same context, primary open-angle glaucoma is expected to affect 79.76 million individuals by 2040.[3] Although Africa has the highest prevalence of primary open-angle glaucoma (4.5%), Asian cases represent about half of the cases due to its large population size.[19] Moreover, 74% of the global glaucoma sufferers have open-angle glaucoma and 80% of glaucoma patients in the United States are of open-angle glaucoma type.[20]

The current study also shows that mean IOP reduction in response to treatment was found to be a predictor of blindness, where patients with legal blindness showed less significant reductions. The previous literature supports the finding that IOP control is the most effective measure in preventing glaucoma progression.[2122] Our study demonstrated a 26.6% prevalence of legal blindness, which is higher than in previous studies. Studies showed that global glaucoma-induced blindness was increased from 4.4% to 6.6% between 1990 and 2010.[23] A previous Saudi study found a moderate visual impairment in 6.5% of glaucoma patients and 0.8% of them were bilaterally blind.[24] Another Saudi study found that about one-third of the patients were legally blind (unilateral) and 11.3% of them were bilaterally blind.[7] Consequently, bilateral legal blindness from glaucoma represents a substantially larger volume than was previously thought. A population-based survey for glaucoma in the Middle East is advocated to estimate the scale of the disease in this part of the world, and future large-scale prospective studies are needed to more accurately define the risk factors associated with disease progression to reduce the social and economic burden of legal blindness.

In addition, age, childhood glaucoma, and normal-tension glaucoma were all associated with a higher risk of blindness. Advanced age has been proven to be a risk factor for glaucoma and hence glaucoma-induced legal blindness.[25] A previous study of glaucoma in childhood found that 29% of the patients had mild visual impairment, 28% had moderate visual impairment, 15% had severe visual impairment, 11% had profound visual impairment, and 15% had near blindness.[26] Glaucoma found to be responsible for up to 5% of blindness among children, and normal-tension glaucoma was responsible for 9.9% unilateral blindness and 1.4% bilateral blindness.[2527] Besides, our analysis showed that 78.6% of the included patients showed good compliance to their treatment regimens. A previously published review reported that the rate of compliance ranged between 5% and 80% in their included studies.[14] The same study also reported that good compliance was significantly associated with the use of interventional approaches (as using medication alarm device; a memory aid in the form of the “C Cap Compliance Cap;” counseling and the “C Cap Compliance Cap;” and an education-and-tailoring program) aimed to increase the compliance.

The current study has its limitations, arising from its retrospective nature. First, there was no treatment protocol followed by the doctors in the ophthalmology department to determine the target IOP for each patient. Second, the study was hospital based which is a source of error in prevalence studies.

Conclusion

The present findings show a high prevalence of legal blindness among glaucoma patients, with IOP reduction, age, and glaucoma type being the most important predictors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.