|Year : 2014 | Volume
| Issue : 2 | Page : 90-94
Exophthalmometric value and palpebral fissure dimension in an African population
Waheed A Ibraheem1, Anifat B Ibraheem2, Charles O Bekibele3
1 Department of Ophthalmology, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria
2 Department of Family Medicine, University College Hospital, Ibadan, Oyo State, Nigeria
3 Department of Ophthalmology, University College Hospital, Ibadan, Oyo State, Nigeria
|Date of Web Publication||13-Nov-2014|
Dr. Waheed A Ibraheem
Department of Ophthalmology, Ladoke Akintola University of Technology, Ogbomoso, Oyo state
Source of Support: None, Conflict of Interest: None
Background: Normative data for exophthalmometric values and palpebral fissure dimensions are important for earlier diagnosis of orbital and palpebral fissure pathologies. Objective: To describe the normal exophthalmometric values and palpebral fissure dimensions among healthy adults of Black race. Design: A cross-sectional descriptive study. Setting: Population based (general community). Method: Population-based multistage random sampling was used to recruit 1020 subjects who had no orbital or eye lid diseases and were free from systemic disease like thyroid eye disease that may affect orbital volume. These healthy adult subjects had their exophthalmometric values and palpebral fissure dimensions (horizontal and vertical palpebral fissure, lateral and medial canthal distances, inter-outer canthal distance, inter-inner canthal distance, margin reflex distance, and lid crease) measured with a Hertel's exophthalmometer and a plain non-stretchable plastic ruler, respectively. Results: A total of 1020 subjects (515 females and 505 males) of age range 16-85 years were studied. The mean ± SD exophthalmometric values were 15.27 ± 2.5 and 15.31 ± 2.4 mm for the right and left eyes, respectively. In the right eye, the mean palpebral fissure height was 8.3 mm, mean palpebral fissure width was 32.1 mm, mean upper eyelid crease was 7.1 mm, mean margin reflex height was 3.2 mm, mean lateral canthal distance was 12.9 mm, and the mean medial canthal distance was 10 mm at primary position of gaze. Conclusions: Exophthalmometric values and palpebral fissure dimensions were obtained among healthy adult Nigerians. Knowledge of these normal parameters is valuable in the management of eyelids and orbital diseases, as well as in manufacturing spectacles.
Keywords: Exophthalmometry, palpebral dimensions, Hertel′s exophthalmometer
|How to cite this article:|
Ibraheem WA, Ibraheem AB, Bekibele CO. Exophthalmometric value and palpebral fissure dimension in an African population. Afr J Med Health Sci 2014;13:90-4
|How to cite this URL:|
Ibraheem WA, Ibraheem AB, Bekibele CO. Exophthalmometric value and palpebral fissure dimension in an African population. Afr J Med Health Sci [serial online] 2014 [cited 2020 May 30];13:90-4. Available from: http://www.ajmhs.org/text.asp?2014/13/2/90/144569
| Introduction|| |
Exophthalmometry is the quantitative assessment of the position of the globe in the orbit.  It may be defined as the measurement of the distance between two parallel planes, one tangential to the apex of the cornea with the eye in the primary position and the other passing through the lateral orbital margin.  Although various techniques ranging from instrumental to radiological had been used to measure this value in different studies, the use of instrument, Hertel's exophthalmometer, is mostly favored. ,,,,
Across various continents, the normal upper limit of exophthalmometric value had been documented to be 21 mm. ,, However, this is not a clear-cut value because of difference in anthropometric values with different races and geographic locations, and upper limit for one race may not be absolutely the same for the others. ,,
The acceptable difference in the exophthalmometric values between the right and left eyes (relative exophthalmometric value) varied among earlier author. ,, While some authors , reported an acceptable upper value of 1 mm, others ,, suggested 2 mm. However, there is a general agreement that relative ocular protrusion is clinically significant when it exceeds 2 mm.  The clinical usefulness of exophthalmometry is in the management of proptosis which is an important clinical sign in the evaluation of orbital diseases. 
The normal morphologic and functional values of eyelids vary widely between race, sex, and age.  Therefore, the knowledge of the average facial and eyelid dimensions based on age, gender, and race is critical for eyelid surgeons to avert complications and achieve satisfactory outcomes. 
Gupta et al. reported a lower medial and lateral intercanthal distance among the Indian population compared with other races.  Price et al. opined that African American men have higher upper eyelid crease height when compared with that of their Caucasian counterparts.  In Nigeria, Oladipo et al. reported a higher canthal distance in Ijaws compared with Igbos and they posited that it is mandatory to have local data of facial parameters of every population. ,
| Materials and Methods|| |
Materials used included standard literate Snellen's chart, illiterate Snellen's E-chart, trial lens box, trial frame, pen torch, stadiometer, weighing scale, retinoscope, Hertel's exophthalmometer, questionnaire, cotton wool, methylated spirit, methylated soap, and 6-m tape measure.
This was a multistage population-based descriptive cross-sectional study. The subjects fulfilled the following criteria: persons of 16 years and above who voluntarily consented to participate, no history of previous eye/orbital trauma, no previous periocular or ocular surgery, no orbital or eyelid diseases that could affect either of the measurements, such as orbital cellulitis, blepharitis and eyelid tumors, and ocular infections, no history of thyroid eye disease, absence of high ametropia (>-6 myopia or >+7 hypermetropia), no facial asymmetry/abnormalities, and absence of anophthalmos.
Informed consent was obtained from the participants, while ethical clearance was obtained from the Ethical Research Committee of the hospital. The study was also conducted in line with the guidelines and principles outlined by the Helsinki's declaration on human research.
The exophthalmometry was done as described by Sodhi et al.  The subjects sat down with their faces at the same level as the examiner's (primary position of gaze). The lateral bony margin of the orbits was digitally palpated after which the footplates of the instrument were positioned gently at these points without exerting excessive pressure. Left footplate, which was fixed, was positioned on the right lateral orbital rim, and the other footplate was adjusted until both footplates rested on orbital rims symmetrically. The rest of the instrument was held parallel to the frontal plane of the patient in line with the pupils. It was also held horizontally with the parallax correcting device (red line) aligned with the gap on millimeter rule. The right eye of the investigator was used to read the subject's left exophthalmometry values (EV), while the left eye was used for the subject's right eye. The EV was taken to the nearest 1 mm of the measuring scale of Hertel's exophthalmometer coinciding with the apex of the cornea. Measurements were taken thrice using the same Hertel's base and the mean of the three readings were taken as the final value.
Palpebral fissure dimensions
The measurement of dimensions was done using the guidelines described by Oztürk et al.  The palpebral fissure dimensions were measured in primary position of gaze except upper eyelid crease which was done at down gaze [Appendices 1 and 2]. The subjects were seated comfortably in a chair opposite to and at eye level with the investigator. The subject was asked to look at the first letter on Snellen's chart at a distance of 6 m. The zero mark on the plastic ruler was aligned with the first reference point, while the measurement was read off from the interception of the second reference point with the meter rule. The two eyes were assessed sequentially, with the right eye done first.
The palpebral fissure dimensions measured are as follows: Palpebral fissure height was defined as the central vertical distance between the upper and lower lid margin, while palpebral fissure width was measured as the horizontal distance between the medial and lateral canthi. Medial canthal distance was taken as the horizontal distance between medial canthus and medial limbus, while lateral canthal distance was measured as the horizontal distance between lateral canthus and lateral limbus. The inter-inner canthal and inter-outer canthal distances were taken as the horizontal distance between right and left medial canthi and right and left lateral canthi, respectively. The margin reflex distance was taken as the vertical distance between the upper eyelid margin and cornea reflex.
| Results|| |
A total of 1020 participants were studied with an age range of 16-85 years (mean ± SD = 46 ± 14.4 years). The distribution of the EV of the right and left eyes is shown in [Figure 1] and [Figure 2], respectively. Fifteen millimeters is the most frequently occurring EV, while EV ranged from 10 to 22 mm in both eyes.
|Figure 1: Distribution of the exophthalmometric values for the right eye|
Click here to view
The mean EV for the right and left eyes are shown in [Table 1]. The mean values for the right and left eyes were 15.27 ± 2.5 mm and 15.31 ± 2.4 mm, respectively. There was no significant difference between the mean EV of the two eyes (t = 1.753, P = 0.08). The range of differences in exophthalmometric value between the left and right eyes was 0-2 mm.
The results of the palpebral dimensions were as shown in [Table 2]. The mean ± SD of right palpebral fissure height was 8.3± 1.6 while the left was 8.3 ± 1.7.
| Discussion|| |
In this study, the range of EV obtained was lower than the reported values in African Americans, , Chinese,  and Caucasians,  but higher than the obtained value in Sri Lankans,  Taiwaneese,  Turkish,  and Dutch.  It was, however, similar to the previously reported values among Nigerians by Majekodunmi and Oluwole.  These differences can be attributed to the differences in the bony orbital structure and the uniqueness of skeletal build-up of mankind over different regions of the earth.  The variation in genetic composition of human beings across different races could also be responsible for this.
Opinions vary on the effect of laterality on EV. While some authors , reported a higher value in the left eye, Kashkouli et al.  reported a higher value in the right eye while Migliori et al.  could not demonstrate any significant difference between the two eyes. In this study, the mean EV was higher in the left eye although it was not statistically significant (P = 0.080). This is in agreement with the findings of Majekodunmi and Oluwole  who attributed the higher EV in the left eye to the farther forward position of the right lateral rims. However, Kashkouli et al.  did not find any obvious reason to account for the difference in the EV between the two eyes and they attributed the difference to technical error (parallax).  In the studied population, the higher EV in the left eye could be due to subtle facial asymmetry that was probably missed due to non-availability of radiological instrument (orbital X-ray or computed tomography) which would have been more reliable to detect subtle facial asymmetry. Furthermore, this finding could actually indicate that laterality truly exists and had an effect on exophthalmometric value in the studied population.
The maximum relative exophthalmometric value obtained in this study was 2 mm in all age groups, which is similar to the documented values by some previous authors, , but contrary to the findings of Majekodunmi and Oluwole  who reported a maximum difference of 3 mm among Nigerian populace. This difference could be due to the different sample sizes and study design used in the two studies (population based vs. hospital based).
The medial and lateral intercanthal distances among the studied population were higher than those obtained in Turkey by Cem et al.  and in Nigeria among Ijaw tribe by Oladipo and co-workers.  They are, however, comparable to the values previously obtained among Yoruba by Anas.  This variation is not unusual as ethnic variations do exist in human anthropometry.  The differences in the values among the studied population compared with other races further reinforce the effect of race and tribe on palpebral dimensions.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]