|Year : 1991 | Volume
| Issue : 1 | Page : 9-11
Benign ocular manifestations of sickle cell Anemia in Arabs
Faculty of Medicine, Jordan University of Science and Technology, Irbid, Jordan., Opthalmology Department, Ibn Sina Hospital, Kuwait
F.R.C.S.. P.O. Box 4955, Yarmouk University, Irbid, Jordan
Source of Support: None, Conflict of Interest: None
A complete ophthalmic examination was carried out for each of 54 adult patients with various forms of sickle cell disease. Mild and infrequent signs in the anterior and posterior segments were found, but there were no cases of proliferative sickle cell retinopathy detected. These findings were compared with the reported findings in the black Americans of African origin with the same disease. The probable explanations were the high prevalence of fetal haemoglobin in Arab sicklers, the rarity of sickle cell disease among the Arabs and the possible existence of a different gene.
Keywords: Sickle cell disease in Arabs, Ocular manifesta-tions of sickle cell disease.
|How to cite this article:|
Al-salem M. Benign ocular manifestations of sickle cell Anemia in Arabs. Indian J Ophthalmol 1991;39:9-11
| Introduction|| |
A high prevalence of sickle cell disease exist in the West Coast of the Arabian Gulf,  but it differs significantly in its natural course and complication rates from that of the African type. ,,,, The typical ocular manifestations of sickle cell disease were described in the black Americans and Jamaicans of African origin ,, but as far as we know, there are no reports on the ocular manifestations of the disease in the Arabs so far. Thus, the purpose of this paper is to report on the ocular manifestations of the disease in Arab sicklers, compare them with those of black Americans and discuss the possible explanation for the differences in morbidity in the two populations.
| MATERIAL AND METHODS:|| |
We examined and followed up the eyes of 54 adult patients with various forms of sickle cell disease over a period of 4 years (1985-1988). These patients were referred from the haematologic and internal medicine departments with the type of sickle cell disease indicated as well as the haemoglobin F level, haemoglobin concentration, reticuloyte count and mean corpuscular volume. Haemoglobin electrophoresis was performed using the cellulose acetate electrophoresis technique, followed up by densitometric quantitation of haemoglobin components.
For each patient the age, sex and ethnic origin were noted. A complete ophthalmic examination was carried out in each case including visual acuity, slit lamp biomicroscopy and fundus examination by direct and indirect ophthalmoscopy through dilated pupils. Fluorescein angiography was performed in 20 patients. The nature and the frequency of the ocular manifestations were compared with the reported manifestations of the disease in Americans of African origin.
| OBSERVATIONS:|| |
The age range was from 16-52 years with a mean of 27.2 years and a standard deviation of ± 7.446. Male to female (sex) ratio was 2.3 to 1. Thirty three patients were from Kuwait(61.1 %) and the rest (38.8°'0) were from various Arab countries including Saudi Arabia, United Arab Emirates Bahrain, Iraq, Jordan, Palestine and Lebanon. [Table - 1] lists the various haematologic indices of the group examined.
The visual acuity was 6/12 in the worst eye in 88.9% of the patients. Six patients had eyes with 6/18 or less vision due to immature cataract in 4 eyes, 2 eyes due to corneal opacities and one due to anisometropia and strabismic amblyopia. [Table - 2] shows the various ocular manifestations of sickle cell disease and their frequencies in the group examined.
A comma conjunctival sign was found in 8 out of 54 patients (14.8%). The sign was mild, transient and quickly disappeared after blood transfusion. Tortuous vessels in the anterior segment (conjunctival and episcleral) were found in 11.1 % of cases. Partial constriction of these blood vessels was achieved by the use of a drop of 10% phenylephrine.
On ophthalmoscopy, there were no signs of ischemia or areas of arteriovenous anastomosis detected and also, there were no areas of non-perfusion of the retina or areas of arterial occlusion found in the 20 patients who had fluorescein angiography and angioscopy performed on them. However, the retinal findings we found were sheathing of major blood vessels in 9 patients (16.6°0) and tortuous retinal blood vessels in 8 patients (14.8%). There was no vitreous haemorrhage, opacities or abnormalities detected of any kind. Two young females aged 19 and 23 respectively were referred with retinal venous occlusion in one eye during puerperium. They were found to have sickle cell trait.
| Discussion|| |
The prevalence of sickle cell trait among the Arabs of the Gulf region is as high as 20% , This high prevalence was attributed to: firstly, the selective natural immunity against malaria,  secondly, the mild from of the disease which is compatible with normal reproduction and long survival ,,, and lastly the frequent marriages among cousins which result in a high rate of consanguinity.
All the ocular complications of sickle cell disease can be attributed directly or indirectly to vaso-occlusions , The vaso-occlusions depends on the degree of blood viscosity which is proportional to the rate of sickling and haemoglobin concentration  The high haemoglobin concentration in Arab patients compared to that of the black American is probably due to the hot weather of the Sahara which would cause dehydration  This increase in blood viscosity is expected to aggravate vaso-occlusion in these patients, but contrary to the expected, this is not the case. Sickle cell disease runs a "benign" course in the Arabs ,,[4[,
The comparison of the frequencies and the nature of the ocular manifestations of the American patients from Jamaica ,,,, and those of the Arabs showed that the ocular manifestations in Arabs are infrequent and mild. For example, it is known that the severity of the comma conjunctival sign correlates well with the presence of irreversibly sickled cells in sicklers  and our finding of only a few cases with this sign in this population reflects the infrequency of irreversibly sickled cells in Arabs. Also, the prevalence of tortuous retinal blood vessels is much less frequently observed than that of the African type (10% vs 32-47%). However, this is not a pathognomonic sign of the disease and can be present in other systemic diseases as well or exists as a normal variant  The presence of tortuous blood vessels in the anterior segment was not stressed as an ocular sign of the disease in the African type, but this is probably a nonspecific sign without a reasonable explanation.
Of note, is the rarity of the retinal signs compared to the African type. We failed to find any areas of abnormalities such as patches of retinal ischemia or breaks in the retinal blood barriers in fluorescein angiograms performed in 20 patients. The macular area was examined carefully for early ischemia but none was detected in those patients  There were no cases that showed peripheral auto-infarction in our series compared to the African type with Sickle cell disease . Also there were no cases of iris atrophy detected in any of our patients examined.  Sickle cell trait may be complicated with retinal vascular occlusions but it was difficult to blame the sickle cell gene alone in either patients we saw during this study as they may have a vascular accident related to the child birth.
It is well known that the reported rates of sickle cell complications differ significantly between those of the black Americans and the Arabs, , and our findings are consistent with this. The explanation which was put forward was the high prevalence of fetal haemoglobin among the Arab sicklers, ,,, and we think it is a logical explanation for the rarity of ocular findings in these patients (fetal haemoglobin was higher than 12% in 77.6% of our cases).
There was only one case in ophthalmic literature with a unilateral black sunburst in a patient who had homozygous sickle cell anemia with high fetal haemoglobin. 15 Thus, fetal haemoglobin not only plays a favourable role in the natural course of the disease but also explains the scarcity of ophthalmic findings. Another reason for the absence of sickle cell retinopathy in this copulation is the rarity of sickle C disease in the Arabs , because of all sickle cell disease forms, sickle C disease carries the highest risk for retinopathy. ,
A recent and probably an important explanation came from molecular genetics studies. It has been shown that there are several sickle genes that differ in DNA haplotypes.  This may suggest that the Arab sickle gene may differ from that of the Africans or Americans and probably resulted from an independent mutations event.
Finally, we think that the infrequency of the ocular findings and their mild nature in the Arab sicklers are worth documenting from our point of view. We cannot say whether these patients are susceptible or not to proliferative sickle cell retinopathy, but future follow-up from this group and other patients is needed to answer this question. However we still recommend blood for sickling to be considered in the workup of each young patient with ocular vascular occlusion as well as periodic follow-up of patients, especially those with low fetal haemoglobin, till the situation is further clarified.
| Acknowledgement|| |
I would like to thank Dr. Aisha Al_Atar from the haematology department and Dr. Nael AI Shakhsheer from the internal medicine department for referring the patients.
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[Table - 1], [Table - 2]