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Average Vmtt Thickness of High Blood Pressure and Normal Blood Pressure Groups

Comments: The group of hypertensive patients had equal rates of macular edema in one eye and two eyes. The group of hypertensive patients had 60% macular edema in two eyes and 40% macular edema in one eye. The relationship between the number of eyes with macular lesions and the blood pressure of the patients was not statistically significant with p = 0.499 (>0.05).

Table 3.19: Average VMTT thickness of high blood pressure and normal blood pressure groups


Average VMTT thickness

(μm)

Number of eyes

n

%

High BP

436.05 ± 122.82

18

36

Normal BP

368.03 ± 115.03

32

64

Total

392.52 ± 120.32

50

100

p

0.054

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Average Vmtt Thickness of High Blood Pressure and Normal Blood Pressure Groups


Comment: The average VMTT thickness of the hypertensive patients group (436.05μm) was much higher than the average VMTT thickness of the normotensive patients group (368.03μm). Hypertension had an effect on the VMTT thickness of the patients with p = 0.054 (approximately 0.05).

Chapter 4: DISCUSSION

4.1. General characteristics of the study patient group

The study was conducted from January 2022 to May 2022 on 50 eyes of 32 patients with diabetic macular edema who came for examination and treatment at the Central Eye Hospital.

4.1.1. Patient distribution by age

In our study, the average age of patients was 57.3 ± 9.37 years old, of which the lowest age was 31; the highest was 74. The age group commonly affected by diabetic macular edema was 50 years old and above, with the lowest rate of 18.8% for those under 50 years old. The average age in our study was lower than that of Huynh Thanh Tung (2017) [6] on diabetic patients at Nguyen Tri Phuong Hospital, which was 63.9 ± 9.20. The results of Nguyen Dinh Ngan (2020) [29] at Military Hospital 103 showed that the average age of the study subjects was 74.35 ± 9.01. This is consistent with the characteristics of diabetes, in previous studies, it was shown that the older the age, the higher the incidence of diabetes and the highest increase was in the group aged 50 and above. In addition, people's awareness of diabetes and its eye complications is still low. Patients often discover the disease at a late stage, or accidentally go to see a doctor for other diseases or when doing routine tests and discover they have diabetes. Moreover, elderly patients often think that the cause is old age or cataracts when they see their vision decline. This leads to the discovery of diabetic macular edema at an advanced age.

4.1.2. Distribution of patients by gender

In our study, the number of female patients accounted for 56.2%, male patients accounted for 43.8%, the ratio of female/male patients was 18/14 ≈ 1.3/1 showing a higher proportion of female patients. Similar to our results, the gender distribution in the studies of Nguyen Phuoc Hai (2020) [26], Nguyen Tuan Thanh Hao (2019) both showed a higher proportion of female patients. In the study of Vu Tuan Anh [1], the ratio of female/male was 40/24; in the study of Huynh Thanh Tung [6], the ratio of female patients accounted for 61%, male patients

accounting for 39%. However, research by Nguyen Dinh Ngan (2020) [29] showed that 45.7% of patients were female, 54.3% were male; the female/male ratio was 0.84/1.

Table 4.1: Comparison of sex ratios between studies

Research by

Year

Female ratio

Male ratio

Vu Tuan Anh [1]

2015

62.5%

37.5%

Huynh Thanh Tung [6]

2017

61%

39%

Nguyen Dinh Ngan [29]

2020

45.7%

54.3%

Nguyen Phuoc Hai [26]

2020

54.1%

45.9%

The results of the studies showed that the difference between the sex ratio was not statistically significant. In fact, the cause of diabetic macular edema is due to fluid leakage from the microvasculature along with risk factors such as old age and cardiovascular disease. The incidence of these groups of diseases does not differ between men and women, therefore, the risk of diabetic macular edema occurring between men and women is the same.

4.1.3. Distribution of patients according to duration of diabetes

The incidence of diabetic macular edema is mainly related to the duration of the disease. In patients with early diabetes, the incidence of macular edema was 0% in the first 5 years, increasing to 3% after 10 years and up to 29% after 20 years. In patients with late diabetes, the incidence of macular edema was 3% after 5 years and 28% after 20 years. Also in this late diabetes group, the incidence of macular edema in the insulin-treated group was 15%, while the oral drug group was 4%.[9]

In our study, the group with diabetes duration of 10-20 years had the highest rate of 40.6%, the group with 5-10 years had 28.1%, the group with less than 5 years had 21.9% and the group with diabetes duration of more than 20 years had the lowest rate.

This characteristic is similar to the study of Nguyen Phuoc Hai (2020) [26] with the group of patients with diabetes for 10-20 years accounting for the highest rate of 32.8%.

4.1.4. Distribution of damaged eyes

Diabetic macular edema usually affects both eyes. In the study, the rate of bilateral macular edema was 56.25%, which is greater than

Macular edema rate in one eye (43.75%). In which the ratio of right and left eyes is equal.

In the study of Nguyen Phuoc Hai [26], the rate of macular edema in both eyes was 60.7%, quite similar to our study. In the study of Vu Tuan Anh [1] and Nguyen Dinh Ngan [29], the rate of macular edema in both eyes in the same patient was up to 70.3%. The rate of macular edema in both eyes in our study was lower than in other studies, which may be explained by the limited number of patients studied. Moreover, the visual acuity of our study group was higher than that of the above studies.

4.2. Clinical characteristics of patients with diabetic macular edema

4.2.1. Vision

The visual acuity of diabetic macular edema patients in the study group was mostly moderately impaired (20/200-20/60) accounting for 56% and there were no cases of normal vision. The group with severe visual acuity impairment (from DNT 3m to less than 20/200) accounted for 14%, the group with blind vision (from less than DNT 1m to less than DNT 3m) accounted for 30%. Previous studies also showed that most patients had visual impairment.

The research results of Vu Tuan Anh[1] are similar to our research, it can be seen that most eyes are in the low vision group below 20/60; high vision 20/25 is very rare (2 eyes). Research by Huynh Thanh Tung[6] showed that in 41 eyes with macular edema, most of the vision was 4/10-7/10 (51.2%); 8/10-10/10 (30.5%); there was 1 eye with vision below 1/10. Research by Nguyen Trong Khai (2018)[28] the rate of patients with vision 7/10 or higher was less than 20%.

According to the ETDRS study[9], the visual acuity of the group with macular edema and early diabetic retinopathy was higher, 43% of eyes had visual acuity 20/25, 41% of eyes had visual acuity between 20/50 - 20/25, only 16% of eyes had visual acuity below 20/50. This can be explained by the ability to detect the disease early in studies in the US compared to conditions in Vietnam. Diabetic patients in Vietnam often come late, people do not have

awareness of regular eye monitoring and examination, failure to detect early signs of blurred vision and failure to receive timely examination and treatment by ophthalmologists.

4.2.2. Functional symptoms

With diabetic macular edema, patients may not notice changes in vision at first. However, over time, vision will gradually decrease and lead to vision loss.

Blurred vision is the first reason why patients come to see a doctor and get treatment, often occurring relatively quickly, affecting the patient's daily life. The cause is due to fluid accumulation in the macular area directly affecting the function of the receptor cells. Distortion, central scotoma, and color disorders are manifestations of macular syndrome, reflecting structural changes in this area caused by edema.

In our study, all patients had blurred vision (100%), while scotomas were found in only 36% of patients. The rate in our study was lower than that of Nguyen Dinh Ngan [29] with 36/54 eyes (66.6%) having scotomas, 31/54 eyes (57%) having distortions, and some other studies, possibly because the patient group in our study had lower average visual acuity than other studies.

4.2.3. Physical signs

In our study, there were 31 eyes with grade I, II cataracts (62%), 13 eyes with clear cataracts (26%), and 6 eyes that had cataract surgery and artificial lens implantation (12%). This result is similar to the research results of Nguyen Phuoc Hai (2020) [26] and Vu Tuan Anh (2015) [1].

The results of the study showed that in a total of 50 eyes, signs of hard exudation accounted for 72%, soft exudation accounted for 38%, hemorrhage accounted for 64%, microaneurysm accounted for 30% and retinal neovascularization accounted for 10%. In the study of Nguyen Dinh Ngan [29], hard exudation accounted for the highest proportion (43/54 eyes), other physical symptoms appeared with lower frequency. Thus, it can be seen that the basic signs of damage

Diabetic macular edema occurs in most patients but is mainly a hard exudation.

Vitreous opacity accounted for 66%; clear vitreous accounted for 32%; the least common was mild hemorrhage in one eye, accounting for 2%.

4.2.4. Macular edema on OCT

Optical Coherence Tomography (OCT) is a modern, non-invasive and safe imaging diagnostic method for patients. In Vietnam, OCT is increasingly used in retinal research, including research on diabetic macular edema.

According to the ETDRS diagnostic criteria for macular edema morphology, in our study, cystoid macular edema and localized macular edema accounted for equal proportions (36%), mixed edema 28%.

Our results are different from the study of Nguyen Phuoc Hai (2020) [26] with localized edema being the most common at 44.9%, cystic edema at 3.6% and mixed edema at 23.5%.

4.3. Relationship between diabetic macular edema and other factors

4.3.1. Relationship between macular edema and characteristics of the study group

For diabetic patients, educational level has an impact and is closely related to the quality of medical services, the ability to regulate blood sugar, the ability to comply with treatment and prevent complications.

Table 3.9 shows that the group of patients who did not graduate from high school had 61.1% macular edema in both eyes and 38.9% macular edema in one eye. The group of patients who graduated from high school had 60% macular edema in both eyes and 40% macular edema in one eye. The group of patients who graduated from University/College had 44.4% macular edema in both eyes and 55.6% macular edema in one eye. The relationship between the number of eyes with macular edema and education level was not statistically significant with p = 0.722 (>0.05).

Table 3.10 shows that the group of patients who did not graduate from high school had the highest average VMTT thickness of 420.10μm. The group of high school graduates

3 had an average VMTT thickness of 372.25μm. The group with the lowest average VMTT thickness was the group of patients who graduated from University/College (343.46μm). The relationship between the patient's VMTT thickness and educational level was not statistically significant, with p = 0.142 (>0.05).

4.3.2. Association between macular edema and duration of diabetes

Duration of diabetes is an important factor in detecting macular edema. The results of previous studies show that in patients with early type I diabetes (before age 30), macular edema almost does not occur in the first years. On the contrary, it is necessary to examine and detect macular edema in patients with late diabetes. Duration of diabetes is also a factor predicting treatment results. Strengthening the management, monitoring and treatment of blood sugar for patients to minimize complications due to diabetes, including eye complications. The longer the duration of the disease, the higher the overall incidence of diabetic retinopathy, thus requiring quality control, adjustment and treatment for diabetic patients, to limit the impact of this leading risk factor.

Table 3.11 shows that the group of patients with diabetes for less than 5 years had 100% macular edema in both eyes; the group of patients with diabetes for 5-10 years had 44.4% macular edema in both eyes and 55.6% macular edema in one eye; the group of patients with diabetes for 10-20 years had 38.5% macular edema in both eyes and 61.5% macular edema in one eye; the group of patients with diabetes for more than 20 years had 66.7% macular edema in both eyes and 33.3% macular edema in one eye. The relationship between the number of eyes with macular edema and the duration of the disease was statistically significant with p = 0.048 (<0.05).

According to Table 3.12, in the 4 groups of patients, the group with diabetes for less than 5 years had an average intimal thickness of 419.53μm; the group with diabetes for 5-10 years had an average intimal thickness of 414.15μm; the group with diabetes for 10-20 years had an average intimal thickness of 352.22μm and the group with diabetes for more than 20 years had an average intimal thickness of 321.8μm. The relationship between the intimal thickness of the patients tended to be related to the duration of diabetes with p = 0.057 (approximately 0.05).

Nguyen Dinh Ngan's study [29] evaluated 54 eyes with macular edema in 35 patients and showed that the progression time of diabetes had not established a statistically significant relationship with macular thickness.

The difference in our study may be due to the fact that patients with diabetes for many years do not remember the exact time of their illness, especially due to the characteristics of diabetic patients in Vietnam who do not have the habit of regular medical check-ups, timely detection and treatment of the disease. In addition, the group of patients with short duration of diabetes but high blood sugar levels (in the group of patients with diabetes for less than 5 years, 71.4% of patients had blood sugar levels above 7mmol/l) may be the cause of macular edema earlier than the group with long duration of diabetes but good blood sugar control.

4.3.3. Relationship between macular edema and blood sugar levels

The best-known risk factor for diabetic macular edema is chronic hyperglycemia. Prolonged hyperglycemia directly damages vascular endothelial cells and compromises the blood-retinal barrier, leading to vascular extravasation and macular edema due to fluid inflow exceeding fluid outflow.

In our study, the group of patients with blood sugar levels below 7 mmol/l had 72.7% macular edema in both eyes and 27.3% macular edema in one eye. The group of patients with blood sugar levels above 7 mmol/l had 52.4% macular edema in both eyes and 47.6% macular edema in one eye. The number of eyes with macular edema depended on the patient's blood sugar level with p = 0.035 (< 0.05).

When analyzing the relationship between blood sugar level and VMTT thickness, we found that: the group of patients with blood sugar below 7 mmol/l had a lower average VMTT thickness (385.89μm) than the group of patients with blood sugar above 7 mmol/l (396.58μm). The relationship between the average VMTT thickness of the patients and blood sugar level was not statistically significant with p = 0.281 (>0.05).

Similar to our study, Seema KS [24] studied 212 diabetic patients and Zaman Huri [12] studied 104 type 2 diabetic patients both showed that blood sugar levels tend to affect macular edema, however, a significant relationship has not been established.

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