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   Table of Contents      
ORIGINAL ARTICLE
Year : 2017  |  Volume : 4  |  Issue : 1  |  Page : 8-17

Ophthalmology national normative database series (2): Gonioscopic character of the normal anterior chamber angle in sudanese adults


1 Department of Glaucoma, Makkah Eye Complex, Khartoum, BIF, Sudan
2 Department of Ophthalmology, Faculty of Medicine, Al-Neelain University, Khartoum, Sudan

Date of Web Publication8-May-2017

Correspondence Address:
Manal Fadlallah
Department of Ophthalmology, Faculty of Medicine, Al-Neelain University, P. O. Box. 10139, Khartoum 11111
Sudan
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DOI: 10.4103/1858-6538.205804

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  Abstract 

Background: The anterior chamber angle (ACA) is the anatomical angle bounded by the iris root and the peripheral corneal vault that comprises the aqueous outflow drains, namely the trabecular meshwork (TM) and the Schlemm's canal. The assessment of the ACA is used to classify glaucoma into open or narrow angle glaucoma's.
Objective: The aim of this study is to determine the normal range values of the gonioscopic character of the ACA in adult Sudanese population and to define the effects of age, gender, and tribal ethnicity on these values.
Materials and Methods: Three hundred ninety-eight eyes (n = 396); of 198 adults volunteers Sudanese healthy workers, from two factories in Khartoum, North district, were enrolled in this study; over a period of 3 months from January 1, 2009 to March 30, 2009. One hundred and sixty males 38 were females; aged ranged from 18 to 50 years. All participants underwent systematic static and dynamic gonioscopy by Posner Gonio lens in conjunction with Haag- Streit slit lamp. Then, the ACAs were graded according to Shaffer grading and classification system. The effect of age, gender and tribal ethnicity on ACA was analyzed. Then, the overall grading and TM Pigmentation analysis were done with special grading criteria specifically designed for this study (Manal–Saleem ACA Overall Grading System and Saleem-Manal TM Pigmentation Grading System).
Results: In total, 198 (n = 198) Sudanese adults were recruited for the study with the mean age of the study group was 43 ± 16 years (range: 18–50 years). About 80.8% of males and 19.2% of females. 77.8% have open ACA and 19.2% narrow ACA, 0.5% closed ACA, and 2.5% with Creeping ACA. Open ACA is more in males (81.3%) than female (63.2%) while narrow ACA is more in female (34.2%) than male (15.6%). Closed and creeping ACA are similar in the two sexes. The effects of tribal ethnicity was not so profound as both the Arabs (84.1%) and Africans (87.5%) origin groups were showing minor differences in the high rate of open-angle (3.4% more in the African's) and narrow ACA (2.9% more in Arab's) apart from the Bejja groups, who recorded 100% narrow ACA while the Nubian groups of Far North recorded a lower percentage of the open ACA (78.6%) and higher of narrow ACA (17.9%). Narrow ACA was proved to be more with older age (25% as compared 10–12.5%). The TM Pigmentation in the younger age groups was found to be of lightly pigmented in 66.7% and heavily pigmented in 33.3%. A result which was affected by tribal ethnicity; 54.9% of Arab origin groups have lightly pigmented TM while 92.0% of African origin groups presented with heavily pigmented TM. In general, pigmentation was shown to be more heavily in the inferior quadrant rather than superior and horizontal quadrants.
Conclusion: There is a higher rate of open ACA (77.8%) in Sudanese Adults with low rate (19.2%) of narrow ACA, followed by an even more lower rate of creeping ACA 2.5% and scarcely closed ACAs (0.5%). The average Sudanese ACA TM pigmentation is 35.4% being of light pigmentation and 64.6% of heavy pigmentation with highly significant tribal, age, and Quadrantic variations (P = 0.000).

Keywords: Anterior chamber angle, aqueous, iris root, peripheral corneal vault, quadrantic, Schlemm's canal, trabecular meshwork


How to cite this article:
Fadlallah M, Saleem M. Ophthalmology national normative database series (2): Gonioscopic character of the normal anterior chamber angle in sudanese adults. Albasar Int J Ophthalmol 2017;4:8-17

How to cite this URL:
Fadlallah M, Saleem M. Ophthalmology national normative database series (2): Gonioscopic character of the normal anterior chamber angle in sudanese adults. Albasar Int J Ophthalmol [serial online] 2017 [cited 2017 Aug 21];4:8-17. Available from: http://www.bijojournal.org/text.asp?2017/4/1/8/205804


  Introduction Top


The anterior chamber angle (ACA) is the anatomical angle bounded by the iris root and the peripheral corneal vault that comprises the aqueous outflow drains, namely, the trabecular meshwork (TM) and the Schlemm's canal. The assessment of the ACA is used to classify glaucoma into open- or narrow-angle glaucomas. The current standard technique to evaluate the configuration of the angle is by direct and indirect Gonioscopy;[1] a procedure by which we able study the anatomical and pathological [2] description of the ACA by the use of goniolens and slit lamp or operating microscopes.[3] Instead, other alternative sophisticated Gonioscopic techniques are available for nonconventional situations; such as noncontact optical coherence tomography [4] rotating Scheimpflug imaging (multiple points' wide angle photography)[5] and ultrasound biomicroscopy,[4] EyeCam, goniophotography,[6],[7] Van Herick angle depth Estimation technique [8] is simple, rough, non-accurate, and quick method with a lot of limitations, which can be used in busy quick screening circumstances.

The criteria of assessing normal Gonioscopic ACA character can be carried in regard to some anatomical and physiological factors to estimate the angle width regarding the seeing ACA landmarks (Pupil, Iris root and insertion, Ciliary body, Scleral spur, TM, Canal of Schlemm, Schwalbe's line, and corneal wedge). Apart from careful grading of the TM pigment cells clumping with regard to the degree of TM pigmentation. Individuals with a greater amount of pigmentation due to excessive pigment release; tend to have darker TM appearance resulting in a gonioscopic finding referred to as a chocolate line. Some of the pigments cells may aggregate onto and anterior to Schwalbe's line to give what is called clinically “samples's line.”[9]

Glaucoma proves to be a great public problem in these days due to the marked human age longevity.[10] It is the second leading cause of preventable [11],[12] reported by the World Health Organization (WHO).[13] This problem is really great in some Asian countries such as China, Mongolia, and Singapore;[14] where chronic primary angle closure glaucoma (PACG) behave much like primary open angle glaucoma leading to missing diagnosis and presentation to health care. It is estimated that China itself has half of the world's cases of PACG.[12],[15] Africans are more susceptible to chronic simple glaucoma (CSG) which it is an open angle type of glaucoma. This silent painfulness and nonsymptomatic blinding disease need to be given high priority of health budget and care in Africa, especially Sub-Saharan countries;[16] Sudan is not an exceptional.

The genetic role in the transmission of CSG obligates health authorities to carry pan-countries' Genetic and genome-wide association studies to early pick up high-risk CSG groups.

During early glaucomatous conditions or natural aging progresses; there are many variable anatomical and physiological configurations to the width and TM pigmentations of the ACA by mechanical, genetics, and environmental oxidative stresses situations by exposure to aqueous humor free radicals. This disrupts TM color and function.[17],[18] Normally, these disruptive processes can be opposed by the body antioxidant defense mechanism which is mediated; by an extensive genetic umbrella.[17] Moreover, antioxidant ascorbic acid (Vitamin C)[18] hyaluronic acid synthesis.[19]

Sudan is diverse Afro-Arabs,[20] multi-ethnic nation; with different racial origins; African that is of partial Arab descend; is a rich, yet virgin land for ophthalmic researches. This unique tribal, ethnic composition can be grouped into 5 main groups:[21],[22],[23],[24],[25],[26],[27],[28],[29],[30]

  1. The Arab origin groups: (Ga'alin Groups, Guhayna, and others)
  2. The African origin groups: (The non-Arab races of Darfur,[22] Nubian tribes in Southern Kordufan, Mapan tribes in Southern Blue Nile, Angassana tribes in Southern Blue Nile, Southern Nilotic tribes, and Western African group)
  3. The Nubian groups in the far North
  4. The Bejja groups
  5. Immigrants origin groups.


This diversion makes our knowledge about the ACA in Sudanese population an instantly questionable issue, the answer of which highlights our susceptibility to different types of glaucoma.


  Materials and Methods Top


This is cross-sectional descriptive community-based study, carried out over 3 months from January 1, 2009 to 30th of March 2009; in Khartoum North Power Station and the factory of “Hanaa Industry for Biscuits;” both in the district of Khartoum North, Sudan. Three hundred and ninety-six eyes (n = 396) from 198 adults volunteers Sudanese workers from the above two factories were enrolled in the study. The age of the subjects ranged from 18 to 50-year-old. The data were collected by joining the visiting teams of the Occupational Medicine Department under the guidance of the Ministry of Health, after receiving an ethical approval from the Khartoum State Ministry of Health, Occupational Medicine Heath team in each factory and verbal consent from each participant who accepted to be enrolled in the study. 160 (80.8%) males from both factories and 38 (19.2%) were females; all of them from “Hanaa Industry for Biscuits” [Figure 1].
Figure 1: Sex distribution

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Any candidate with any ocular morbidity which affects the normal anatomical character or the visualization of the ACA (Glaucoma, Uveitis, Trauma, Diabetes or any vascular diseases, marked errors of refraction, intraocular tumors, ocular surgery, corneal opacity, and congenital abnormalities of the ACA) was excluded from the study.

All participants after documented their detailed bio-data underwent routine ophthalmic examination and systematic static (in 364 eyes, 92%) and dynamic Gonioscopy (in 32 eyes, 8%) by Posner Gonio lens (Ocular Posner Diagnostic and Surgical Gonioprism with Ergonomic Handle, Ref: OMP6289; Ocular; Posner Gonio Lens; from Ocular Instruments Inc., Washington 98004-3039 USA); in conjunction with Haag- Streit slit Lamp (Haag-Streit AG; Gartenstadtstrasse 10; 3098, Koeniz; Switzerland). The effect of age, gender and tribal ethnicity on ACA was analyzed by IBM SPSS Inc. PASW Statistics for Windows, Version 18.0; 2009. Chicago: SPSS Inc.; Software Group's Business Analytics Portfolio).

The whole candidates were grouped in 3 age groups as follows: (1) 18–25 years; (2) 26–40 years; (3) 40–50 years. The Sudan Tribes were classified in this study into different 5 ethnic and racial groups and subgroups; according to “The Current Sudan Tribal composition” as follows:[21],[22],[23],[24],[25],[26],[27],[28],[29],[30]

(1) The Arab origin groups, (2) the African origin groups, (3) the Nubian groups in the far North groups, (4) the Bejja groups, and (5) immigrants origin groups. The 4 quadrants of ACA were checked in the order of superior, inferior nasal and temporal quadrants, and then graded according to Shaffer grading and classification system,[31],[32] which is based on an estimate of the angular width between the peripheral iris plane and the corneoscleral wall in the vicinity of the TM; forming 5 grades of the following angle grading and classifications: (1) 35°–45°; grade IV wide open angle, (2) 25°–34°; Grade III moderately open angle, (3) 20°; Grade II moderately narrow angle, (4) 10°0; Grade I extremely narrow angle, and (5) 0°; Grade 0 closed angle.

Manal–Saleem anterior chamber angle overall grading system

Then, the overall grading is done after finishing the examination as homework, according to the following criteria which were adopted specifically for this study under the umbrella of the above Shaffer grading system and named “Manal–Saleem” ACA overall grading system:

  • If more than 50% of the angle (more than 2 quadrants) is of Grade III or IV, this angle is considered to be an open angle
  • If 50% or more than 50% of the angle is of Grade II, this angle is considered to be a narrow-angle
  • If more than 50% of the angle is of Grade I or 0, this angle is considered to be a closed angle
  • Whenever, the angle grading is a mixture of all grades, so this angle is considered to be a creeping angle.


Manal–Saleem trabecular meshwork Pigmentation Grading System

The pigmentation of the TM was graded according to the following system which was adopted specifically for this study under the name of “Manal–Saleem” TM Pigmentation Grading System:

  • If more than 2 quadrants (50%) of TM with light pigmentation; this angle is considered to be of “lightly pigmented TM”
  • If more than 2 quadrants (50%) of TM with heavy pigmentation; this angle is considered to be of “heavily pigmented TM”
  • To determine light or heavy pigmentation, we depend on the depth of the brown color which stated
  • Dark brown for heavy TM pigmentation
  • Light brown for light TM pigmentation.


The criteria of assessing the gonioscopic character adopted in this study were limited to the main two important components of ACA regarding the angle width and the angle degree of TM pigmentation only.


  Results Top


In total, 198 (n. of eyes = 396) Sudanese adults with diverse tribal origins were examined. The mean age of the study group was 43 ± 16 years (range: 18–50 years). Male were markedly predominant as the whole Khartoum North Power Station labors are males due to the nature of the heavy job requirements; so 160 (n = 160; 80.8%) males from both factories and 38 (n = 38; 19.2%) were females [Figure 1]; all of females were from “Hanaa Industry for Biscuits.”

The age distribution of the subjects recruited was ranging from 18 to 50 years. Subjects in the age group (18–25) years were found to be 15 (n = 15; 7.6%). Subjects in the age group (26–39) years were 79 (n = 79; 39.9%) while the subjects in the 3rd age group (40–50) years, forming the majority, were 104 (n = 104; 52.5%) of the study population [Figure 2].
Figure 2: Age groups distribution in years

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In the tribal distribution [Figure 3] and [Table 1]; tribes were classified into 5 main groups and subgroups. The Arab origin groups were 136 candidates (n = 136, 68.7%); Ga'alin (85 subjects; n = 85; 42.9%); and Guhayna group (51 subjects; n = 51; 25.8%). The Nubian groups in the far North were 28 (n = 28; 14.2%). African origin groups were 31 (n = 31; 15.7%), constituting the Western African group as 6 (n = 4; 3.0%) and the “non-Western African groups” as 25 (n = 25; 12.6%). The least were the Bijja groups who were only 3 subjects (n = 3; 1.5%). No candidates from 5th Immigrants origin groups [Figure 3].
Figure 3: Tribal groups distribution

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Table 1: Tribal groups distribution

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The ACA characters in each age group were computed to be as follows [Table 2]: The 1st age group “18–25 years” constituted 15 (7.6% of the total population); 13 (86.7%, 6.6%) of them; they showed open ACAs while 2 (13.3%, 1%) subjects showed narrow ACAs. No closed or creeping angles were seen in this age group. While the 2nd age group “26–40 years” constituted 79 (39.9%) subjects; 66 (83.5%, 33.3%) of them they showed open ACAs, 10 (12.7%) subjects showed narrow ACAs and 3 (3.8%, 1.5%) subjects showed creeping angles. No closed angles were seen in this age group. The 3rd age group “40–50 years” constituted 104 (52.5%) subjects; 75 (72.1%, 37.9%) were open ACAs while 26 (25%, 13.2%) were narrow ACAs; but only 1 (1.0%, 0.5%) participant proved to have closed angle and 2 (1.9%, 1.0%) presented with creeping angles.
Table 2: Overall anterior chamber angle grading and age groups distribution

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The effects of gender or sex on the Character of the Sudanese adults ACA can be presented by the fact that; the rate of open ACA between the Sudanese Adult males population was 81.3%; 130 males out of the 160 total males (with an overall rate of 65.7% from the whole males-females studied population). While the rate of this open ACA came to be 63.2% (24 females out of the 38 total female populations) between the Sudanese adult female's population, (with overall rate of 12.1% from the whole males-females studied population). However, narrow angle grading was found in 15.6% (12.6%) of males and 34.2% (6.6%) of the females, and creeping angle was found in 2.5% (02.0%) males and 2.6 (0.5%) females [Table 3].
Table 3: Overall grading in relation to both sexes

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[Table 4]a and [Table 4]b presented the effects of tribal ethnicity on the ACA values of the Sudanese adults in different Sudanese tribes: Open ACA was found to be 78.5% between the Arab origin groups which is 53.5% of the whole studied Sudanese population (32.8% in the Ga'alin group and 20.7% in the Guhayna group). The Nubian groups in the far North reported a rate of 78.6% within their community; which almost similar to that of Arabs origin groups, although the real overall rate was only 11.1%. The rate of open ACA in African origin groups reported to be 13.1%. All the Bejja groups repotted 100.0% of narrow ACA type. In the meantime, narrow ACA grading was found in 21.2% of the Ga'alin group, 17.6% of the Guhayna group, 17.9% of The Nubian groups in the far North, 8.0% of African group, and 16.7% of Western African group and. Closed angle grading was found only in 3.6% of the Nubian group. Creeping angle grading was recorded in 2.4% of Ga'alin group, 2.0% of Guhayna group, 4.0 of the African group, 16.7% of Western African group; however, this Creeping angle is not recorded at all in the Nubian and Bejja groups.
Table 4:

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In summary [Table 4]a and [Table 4]b and [Figure 4]; the overall rate of open ACA between Sudanese can be estimated up to 77.8% of the ACAs. Narrow ACA reported a rate of 19.2% in Sudanese; Creeping angles were 2.5%, and least was the closed ACA, which was reported only in the far North Nubians in a rate of only 0.5%.
Figure 4: Anterior chamber angle overall grading

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The gonioscopic quadrantic grading of the ACA revealed that the superior ACA was the narrowest quadrant in 9.4% in the overall grading, with slight difference between the right and left eyes in a ratio of 1:1.5 (11.1%: 7.6%) in favor of the right eye. While the inferior quadrant reflecting the widest in 52.3% of cases; with no big difference between the right and left eyes.

Trabecular meshwork pigmentation anterior chamber angle grading [Table 5]{{Table 4} 5}

The overall light TM Pigmentation of ACA was found to be 35.4% while the overall heavy TM Pigmentation Grading was reported to be 64.6%. However, these results differ according to different age and tribal ethnic groups [Figure 5].
Figure 5: Average Sudanese trabecular meshwork pigmentation

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The effect deferent age groups [Table 6] reviled that Pigmentation of the TM in the 1st age group “18–25 years” was found to be of “lightly pigmented TM grade” in 66.7% (10 out of 15 adults in this group) and 33.3% (5 out of 15 adults) shown heavily pigmented TM. In the 2nd age group, “26–40 years,” 75.9% have light pigmented TM and 24.1% shown heavily pigmentation of the TM. While in the 3rd age group “40–50 years” which constituted 104 subjects; the light pigmented TM was found in only 33.7% (n = 35) of this age group and 66.3% (n = 69) shown to have heavy pigmented TM.
Table 6: Percentage of grading trabecular meshwork pigmentation and age groups distribution

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The effects of tribal ethnicity on the ACA TM Pigmentation Grading System can be presented by the following ACA TM Pigmentation resulted in different Sudanese tribes [Table 5]. The light pigmented TM in the overall Arab origin groups was 54.9% (66.7% for Ga'alin and 43.1% for Guhayna) while the heavy pigmented, TM was 45.1% (33.3% for Ga'alin and 56.9% for Guhayna). The light pigmented TM in the overall African origin groups was 8.0% (0% for Western African group and 16.0% for the “non-Western African groups”) while their heavy pigmented TM record was 92.0% (100% for Western African group and 84.0% for the “non-Western African groups”). The light pigmented TM in the Nubian groups in the far North was 78.6% and their heavy TM pigmented was 21.4%. The Bejja groups shown 100.0% heavy pigmented TM ACA [Figure 6].
Figure 6: Percentage of tribal trabecular meshwork pigmentation

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Generally; TM Pigmentation was shown to be more heavily in the inferior quadrant rather than superior and horizontal quadrants [Table 7].
Table 7: Percentage of Trabecular Meshwork pigmentation in different quadrants

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  Discussion Top


Although this study is not focused on the investigation of glaucoma; still the evaluation of ACA is a challenge for identification of those patients susceptible for one or another type of glaucomas.[33] Assessment of ACA has an important role in primary ophthalmic health care in identifying people who would be at risk of deferent types of the disease as they will benefit from further investigations and treatments. Matter which it helps in the future planning of the use of medical resources, according to the predicted National burden of the glaucoma disease.[34]

Sudanese people being half cast community; with unique and diverse multi-racial population; predominantly of Africans and Arabs origins; ACA assessment in Sudanese adult by Gonioscopy to provide quality information is capable of filling the gaps in the shortage of knowledge about the features of the normal ACA in Sudanese adults and to help in determining the common type of glaucoma in Sudan. A country where the crude prevalence of glaucoma between blind populations may exceed 19.3%.[35],[36],[37],[38] This valuable knowledge will help in the planning of proper national glaucoma blindness prevention program.

Actually, due to the relative scarcity and limitation of published data in population-based studies about normal ACA character in deferent communities as such; we compelled to use in our discussion dialog, another comparative data from other anterior chamber (AC) “Ocular Novel Biometric Parameters”,[39] and epidemiological glaucoma studies. That may carry evolutionary perspective values [40] which indicate the type of the ACA character.[41] These Biometric Parameters include Lens vault, anterior vault (which are defined as the maximum distances between the horizontal lines connecting the two Scleral Spurs and the posterior corneal surface and anterior lens surface, respectively),[42] and AC depth (ACD).[43],[44]

In this study; the investigators detected an overwhelming predominance of overall open ACAs in adult Sudanese individuals (77.8%) as compared to the overall low rate of narrow ACA (19.2%) and the scarcity of the closed ACA (0.5%) (P = 0.070). These observational results were reconciled with the clinical experience and other data in the literature. As African origin groups usually constitute up to 6 times high-open angle glaucoma [45] therefore anatomically open ACAs. On contrary to the low rate of open ACA in anther nations and ethnic groups: Eskimos [46] and East Asian (open ACA = 35% narrow ACA = 65%)[47],[48] populationssuch as Chinese,[49] Singaporeans,[50] South Indian (Chennai Glaucoma Study in urban South Indians [48] Mongolians,[14] and Myanmarese (Casson; 2007, the Meiktila Eye Study).[41] New Zealanders was significantly shallower than all above racial groups. The deepest ACD found in Saudi Arabia and Brazil.[51] Nwosu SN and Apakama AI in Nigeria (2012) repotted a low rate of open ACA of 37%[2] Which was far less than our Sudanese open ACA of 77.8% although both of them are Africans whom always report high rate of Open-angle ACA, which manifested by the known high-rate open-angle glaucoma. While the same report showed 27.2% of narrow ACA and 1.4% of closed ACA, both results were higher than our results in which the of narrow ACA was 19,2%, and the closed ACA was only 0.5%. The possible explanation for these big variations between the two African groups is that the Nigerians study subjects were older; up to 85 years compared to the 50 years population of the current study as the ACAs tend to be shallower with aging.[52],[53],[54] This study clearly highlighted well the so clear effect of racial differences on the Sudanese Adults ACA Character [Table 3] and [Table 4] which is in accord with clinical experience and previous studies in literature.[50],[52],[55],[56],[57]

Furthermore, gender differences were very clear in this study [Table 3], which are in accord with other studies such as Takusagawa and Mansberger [58] and Friedman et al.[57] Women (34.2%) were found to have narrower angles than men (15.6%) [Table 3],[57],[58] and older persons had more narrow angles.[57] Narrower angle among women seems to be associated simply with smaller overall ocular and general body size.

The current work demonstrated Gonioscopic Quadrantic ACAs variations across the vertical and horizontal meridians (Superior and Inferior, Nasal and temporal ACAs) in elderly subjects; where the superior quadrant was significantly narrower than the widest inferior quadrant (P = 0.011). The variations in the width of the examined quadrants were counted up to 19.5% in both eyes. These results were in agreement with Professor He et al. results in “the Liwan Eye Study”[49] Chinese community although with higher rate of occurrence (37.9%). Professor He et al. postulated that this Quadrantic variations, happening due to gravitational forces in the sitting position and indentation of the superior cornea by the upper lid; however, these postulations need further studies.[59]

Chen et al.[60] did notice no Quadrantic differences in younger subjects while there was more nasal quadrant narrowing in elderly females; eventually high incidence of angle closure glaucoma. The same observation in young's adults was noticed by Koç et al.[59] in individuals above 40s. Pettersson and Källmark from Stockholm confirmed the narrowing of nasal ACA in young age group with exophoria.[61] Few researchers demonstrated even higher incidences of narrowing in the superior quadrants [62] and more widening in the inferior quadrants than ours. Although we reported an average of 9.4% more superior quadrant AC angle narrowing than He et al.[49] and some others (the superior angles being the narrowest AC angles). While the inferior quadrants show widely opened AC angles in 52.5% of both eye (the widest AC quadrant angle). These quadrantic angles results in accord with Sakata et al. Furthermore, Singaporean's studies by Kunimatsu et al.[63] supported the superior quadrant angle as being the narrowest ACA while the inferior ACA being the widest angle.[63]

There are few TM Pigmentation Grading Systems such as the 5 steps grading system: From 0 which denote no pigmentation up to 4, which denote heavy pigmentation. This grading is confusing as it depends on a big range of colors and color hues scale; all from the black main color.[64] Another sophisticated grading systems that depend on a computerized program (ImageJ software),[65] which cannot be easy in some areas, especially in the rural areas. Hence, we adopted above-mentioned “Manal–Saleem TM Pigmentation Grading System” as a simple grading system, light brown color for light TM pigmentation, and dark brown color for heavily TM pigmentation.

This study demonstrated that the TM pigmentation has a significant racial, gender, and age variations (P = 0.000) as Arab origin groups and the Nubian groups in the far North reported light TM pigmentation of 54.9% in Arabs groups and 78.6% in the Nubians (average 66.8%). This was in contrary with the heavy TM pigmentation of our African origin and Bejja groups [Table 5] and [Figure 6] (92.0% and 100% consecutively; average 96%). The above result is concurred with Pary-Van Ginderdeuren et al.,[66] who noted a high percentage of TM pigmentation in African's Congolese (79%) as compared with their Belgian Europeans inhabitants (35%).

Quadrantic TM pigment distribution [Table 7] revealed the highest TM heavy Pigmentation in the Inferior Angle (that means the maximum heavily pigmented), which increases with age [Table 6] in agreement with Kinori et al.,[67] which can be explained by the gravitational setting of the pigments inferiorly. The least in the heavy pigmentation distribution was the superior Angle followed by nasal and temporal angles, respectively. While the maximum lightest pigmentation in the superior Angle. However, the highest TM heavy Pigmentation was in the Inferior Angle, which increases with age, pseudoexfoliation, pigmentary glaucoma, and corticosteroid-induced glaucomas.[67] while the least in the heavy pigmentation distribution was the superior angle (that means the maximum lightly pigmented) followed by nasal and temporal angles, respectively. These findings need more studies to be proved or deny.

Because of shortage in the literature concerning the degree and grading of TM pigmentation, we considered in our discussion; the available epidemiological data's of Pseudoexfoliation syndrome (XFS), Pigment Dispersion Syndrome (PDS), and Pigmentary Glaucoma prevalences. As there is an increased TM pigmentation in these types of glaucoma's,[68] which are so common in some European's rather than African's countries for example, Scandinavian's have a high rate of XFS; up to 20% in northern Sweden.[69],[70] The above-mentioned types of glaucoma's (especially PDSs) are thought to be rare in blacks, with exceptions to some extends; of Black South Africans (6.9%).[71] The prevalence's of ACA pigmentation is low in some nations such as Chinese is 3.4%,[72] South Indians 3.8–6% (4.8%),[73] Japanese 3.4%,[74] Upper Eygptians 4.1%,[75] and Nil n Eskimos.[76] All these races still shown lower rate of heavy pigmentation than ours.


  Conclusion Top


This study which as far as we know is the first ACA Gonioscopic assessment in Sudan to provide National normative data about the ACA character; regarding size and degree of TM pigmentation. To conclude that the there is a higher rate of open ACA (77.8%) in Sudanese adults with low rate (19.2%) of narrow ACA followed by an even more lower rate of Creeping ACA 2.5% and scarcely closed ACAs (0.5%). The average Sudanese AC TM pigmentation is 35.4% being of light pigmentation and 64.6% of heavy pigmentation with highly significant tribal, age, and Quadrantic variations (P = 0.000). These observations put the studied multi-ethnic Sudanese nation mainly toward their mixed African and Arabs ancestors. However, this issue needs further wide national population-based studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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