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Khan A.O.,King Khaled Eye Specialist Hospital | Khan A.O.,King Faisal Specialist Hospital And Research Center
Current Opinion in Ophthalmology | Year: 2013

PURPOSE OF REVIEW: Centered on the Arabian Peninsula, the Middle East encompasses Northern Africa to Western Asia. Primarily Arab and historically tribal, populations from this region often practice customary intrafamilial marriage (consanguinity), intratribal marriage (endogamy), and a preference for many offspring. These social factors increase the frequency of homozygosity, including homozygosity for gene mutation and thus for recessive ocular disease. This review highlights recent studies of ocular genetic disease in the Middle East. RECENT FINDINGS: Among modern molecular genomic/genetic strategies, homozygosity mapping as a method to guide candidate gene analysis has been a powerful technique for the Middle East. Studies from the region have enhanced our understanding of ocular genetic conditions that are more common worldwide (such as pediatric glaucoma, pediatric cataract, and retinal dystrophy/dysfunction), rare worldwide (such as cornea plana, brittle cornea syndrome, and posterior microphthalmos), and currently only reported on the Arabian Peninsula (such as microcornea with myopic chorioretinal degeneration and telecanthus, familial retinal arterial macroaneurysms, and spherophakia with short stature). For some patients diagnosed with non-syndromic cataract or retinal dystrophy, genomic/genetic analysis uncovered recessive mutation in a syndrome gene and phenotypic reassessment confirmed the presence of the undiagnosed syndrome in the tested patients. SUMMARY: Recent studies from the Middle East, many of which employed homozygosity mapping, have improved phenotype-genotype correlations for common and rare ocular genetic disease. In some instances genetic diagnosis revealed an undiagnosed syndrome. Reports of ocular genetic conditions thus far unique to the region have suggested novel ocular developmental pathways. © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins.


Al-Saikhan F.I.,Salman bin Abdulaziz University | Al-Saikhan F.I.,King Khaled Eye Specialist Hospital
Saudi Journal of Ophthalmology | Year: 2013

The advances in gene therapy hold significant promise for the treatment of ophthalmic conditions. Several studies using animal models have been published. Animal models on retinitis pigmentosa, Leber's Congenital Amaurosis (LCA), and Stargardt disease have involved the use of adeno-associated virus (AAV) to deliver functional genes into mice and canines. Mice models have been used to show that a mutation in cGMP phosphodiesterase that results in retinitis pigmentosa can be corrected using rAAV vectors. Additionally, rAAV vectors have been successfully used to deliver ribozyme into mice with a subsequent improvement in autosomal dominant retinitis pigmentosa. By using dog models, researchers have made progress in studying X-linked retinitis pigmentosa which results from a RPGR gene mutation. Mouse and canine models have also been used in the study of LCA. The widely studied form of LCA is LCA2, resulting from a mutation in the gene RPE65. Mice and canines that were injected with normal copies of RPE65 gene showed signs such as improved retinal pigment epithelium transduction, visual acuity, and functional recovery. Studies on Stargardt disease have shown that mutations in the ABCA4 gene can be corrected with AAV vectors, or nanoparticles. Gene therapy for the treatment of red-green color blindness was successful in squirrel monkeys. Plans are at an advanced stage to begin clinical trials. Researchers have also proved that CD59 can be used with AMD. Gene therapy is also able to treat primary open angle glaucoma (POAG) in animal models, and studies show it is economically viable. © 2013 Saudi Ophthalmological Society, King Saud University.


Rashaed S.A.,King Khaled Eye Specialist Hospital
Clinical Ophthalmology | Year: 2013

The purpose of this paper is to report an unusual case of accumulation of residual subretinal fluid after surgery for acute rhegmatogenous retinal detachment, sparing the fovea. A 28-year-old male presented with a four-day history of acute visual loss in his right eye secondary to bulbous rhegmatogenous retinal detachment, sparing the fovea. The patient underwent an uneventful pars plana vitrectomy and scleral buckling procedure. At four weeks postoperatively (after complete gas resorption), the visual acuity was 20/40. However, the patient complained of blurred vision. A dilated fundus examination showed a flat retina and the presence of multiple yellowish subretinal deposits resembling vitelliform lesions in the macula. Some lesions were encroaching on the fovea, and were connected via a tract to a previous horseshoe tear with evidence of a thin layer of subretinal fluid. The patient symptoms persisted for one year postoperatively. However, the retina remained flat with evidence of retinal pigment epithelium mottling and faint scars corresponding to previous lesions. Persistent subretinal fluid with thick subretinal precipitate can occur even after successful surgery for acute retinal detachment sparing the fovea and cause visual dysfunction. © 2013 Al Rashaed, publisher and licensee Dove Medical Press Ltd.


Khan A.O.,King Khaled Eye Specialist Hospital
Ophthalmic Genetics | Year: 2011

Primary congenital glaucoma (isolated goniodysgenesis) has classic phenotypic features such as increased measured intraocular pressure, globe enlargement (buphthalmos) with associated myopia, Descemet membrane tears, corneal haze/scarring with associated astigmatism, iris atrophy, and optic nerve cupping. These signs also occur in developmental glaucoma (anterior segment dysgeneses) with infantile onset. However, similar findings can occur in other pediatric conditions which are sometimes are mistaken as early childhood glaucoma. © 2011 Informa Healthcare USA, Inc.


Purpose: To explore the relationships among cycloplegic refraction, keratometry, and axial length in children with refractive accommodative esotropia and to evaluate the feasibility of axial length estimation from the other 2 parameters. Methods: This is a prospective case series of children ages 4-12 years who were diagnosed with refractive accommodative esotropia, cooperative for keratometry and optical biometry by the IOLMaster, and without amblyopia in the right eye. The right eyes of the first group of patients were used to generate a linear regression formula from cycloplegic refraction, keratometry, and axial length. This formula was used in the second group of patients to estimate axial length from cycloplegic refraction and keratometry. Results: A total of 100 children were enrolled. Cycloplegic refraction ranged from +2.25 D to +8.25 D, keratometry ranged from 38.34 D to 48.37 D, and measured axial length ranged from 19.34 mm to 23.66 mm. Estimated and measured axial lengths were strongly correlated (Pearson coefficient = 0.9; 95% CI, 0.83-0.94) with the former values having a greater mean by the paired t test (2-sided P < 0.0001; difference between means, 0.27 mm). Estimated and measured values differed by <0.5 mm for most eyes (33/50, 66%) and were within 1 mm for all eyes. Conclusions: In children with refractive accommodative esotropia, there exists a constant mathematical relationship among cycloplegic refraction, keratometry, and axial length. This relationship allows reasonable estimation of axial length from the other 2 parameters. © 2011 by the American Association for Pediatric Ophthalmology and Strabismus.


Khan A.O.,King Khaled Eye Specialist Hospital
Open Ophthalmology Journal | Year: 2015

Glaucoma in children differs from adult-onset disease and typically requires surgical intervention. However, affected children exhibit a spectrum of disease severity and prospective data guiding the choice of operation are lacking. This article reviews common procedures and a surgical approach to pediatric glaucoma. © Arif O. Khan; Licensee Bentham Open.


Arevalo J.F.,Wilmer Eye Institute | Arevalo J.F.,King Khaled Eye Specialist Hospital
Current Opinion in Ophthalmology | Year: 2014

Purpose of review To review the current management and recent changes in treatment paradigm for diabetic macular edema (DME). Recent findings During the review period (1 year), several prospective studies analyzed the beneficial effect of anti-vascular endothelial growth factor agents in the management of DME. An exploratory analysis concluded that intravitreal ranibizumab appears to be associated with a reduced risk of diabetic retinopathy worsening. A randomized, controlled, multicenter, double-masked, parallel-group, 12-month trial to evaluate a dexamethasone intravitreal implant (DEX implant) combined with laser photocoagulation compared with laser alone for treatment of DME concluded that there was no significant between-group difference at month 12. A multicenter, prospective, observational study found that in eyes with diabetic retinopathy without concurrent central-involved DME, presence of noncentral-involved DME immediately prior to cataract surgery or history of DME treatment may increase the risk of developing central-involved macular edema after cataract extraction. Another randomized trial to evaluate whether intravitreal ranibizumab injection at cataract surgery prevents postoperative DME concluded that intravitreal ranibizumab injection at cataract surgery may prevent the postoperative worsening of macular edema. Summary The results of clinical trials have shown the superiority of some of these anti-vascular endothelial growth factor agents to laser therapy. However, with the availability of several of these newer agents, it may be difficult to individualize treatment options, especially if DME patients respond differently to various therapies. © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins.


Khan A.O.,King Khaled Eye Specialist Hospital
Journal of AAPOS | Year: 2012

Background: In nonamblyopic eyes of hyperopic children, axial length has a consistent mathematical relationship to cycloplegic refraction and keratometry such that estimated axial length = ([-0.04 × refraction] + 2.98) × (corneal radius)]. The purpose of this study is to determine whether the pathophysiology of amblyopia affects this relationship. Methods: This a prospective case series of children 5 to 16 years of age diagnosed with esotropia related to uncorrected hyperopia who underwent keratometry and optical biometry by the IOLMaster in addition to cycloplegic refraction. The equation was assessed in affected eyes of consecutive children with unilateral amblyopia (at least 2 lines interocular difference with refractive correction). Results: Of the 23 identified children (16 males, 7 females, 5-14 years of age), all had a cycloplegic spherical equivalent of ≥+2.75 D in at least one eye, 14 were anisometropic (by >1.00 D), and none had myopia. Estimated and measured axial lengths of amblyopic eyes were strongly correlated (Pearson coefficient 0.9; 95% confidence interval, 0.79-0.96) and did not differ significantly by the 2-sided paired t test (P = 0.3; difference between means, 0.1). The two values differed by ≤0.5 mm for most eyes (20/23) and were within 0.9 mm for all eyes, similar to what has been described for nonamblyopic eyes. Conclusions: The intraocular relationship of axial length to cycloplegic refraction and keratometry in hyperopic nonamblyopic eyes is maintained in hyperopic amblyopic eyes. Thus, the pathophysiology of amblyopia in this setting does not involve a mismatch among these biometric variables. © 2012 by the American Association for Pediatric Ophthalmology and Strabismus.


Khan A.O.,King Khaled Eye Specialist Hospital
Current Opinion in Ophthalmology | Year: 2011

PURPOSE OF REVIEW: To provide an overview of the genetics of the primary open-angle glaucomas with particular attention to congenital, infantile, and juvenile forms. RECENT FINDINGS: Mutations in CYP1B1, in addition to being the most common identifiable cause of autosomal recessive primary congenital/infantile glaucoma, can infrequently underlie juvenile and even primary adult-onset open-angle glaucoma, particularly in certain consanguineous populations. In 2009, patients diagnosed with congenital/infantile glaucoma were found to have recessive mutations in a second gene, LTBP2, with a phenotypic spectrum that includes primary megalocornea, spherophakia with ectopia lentis, and lens-related glaucoma. The most common identifiable cause of primary juvenile open-angle glaucoma across most populations remains heterozygous (autosomal dominant) MYOC mutation, underlying up to one-third of cases and possibly sometimes involved in earlier and later onset glaucomas Although primary adult-onset open-angle glaucoma usually does not follow simple Mendelian genetics and is etiologically complex, genome-wide association studies are uncovering genetic susceptibility factors. In some cases, primary adult-onset open-angle glaucoma can be caused by heterozygous mutation in MYOC, OPTN, or WDR36. In addition, in 2009, heterozygous NTF4 mutation was associated with the phenotype in a small percentage of patients from a German cohort. SUMMARY: Seemingly unaffected siblings of children with CYP1B1-related primary congenital/infantile glaucoma should undergo genetic testing because of variable expressivity for the phenotype; such testing should also be considered for other asymptomatic relatives, especially in consanguineous families. In western populations, dominant MYOC mutation remains a common cause of primary open-angle juvenile glaucoma and infrequently can be implicated in congenital/infantile or adult-onset forms; identified families should undergo genetic counseling. Primary adult-onset open-angle glaucoma rarely follows simple Mendelian genetics, but genomic studies in different populations are revealing potential genetic risk factors for the phenotype. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.


Nowilaty S.R.,King Khaled Eye Specialist Hospital | Mousa A.,King Saud University | Ghazi N.G.,King Khaled Eye Specialist Hospital
Ophthalmology | Year: 2013

Purpose: To report and analyze the spectral-domain optical coherence tomography (SD-OCT) features of the posterior pole and papillomacular fold (PMF) in posterior microphthalmos (PM) in relation to axial length of the globe and corneal power. Design: Comparative case series. Participants: Forty eyes of 20 PM patients and 70 eyes of 35 age-matched controls. Methods: All PM and control eyes underwent a full biometric evaluation, including axial length and corneal power measurements, and macular SD-OCT. In addition, a novel SD-OCT marker of the posterior pole curvature, termed the posterior pole curvature index (PPCI), was measured along both the vertical and horizontal meridians. The OCT characteristics of the PMF were analyzed and the PPCIs were compared and correlated with the axial length and corneal power in both groups of eyes, and with the PMF severity in PM eyes. Main Outcome Measures: We considered the SD-OCT features of the PMF, the PPCI in PM eyes and controls, and the correlations between PPCI and PMF severity and axial length. Results: All PMFs were predominantly horizontal and partial thickness, sparing the outer retina except the outer plexiform layer. The PPCI in PM eyes (mean ± standard deviation, 145±40.3 microns; median, 144) was significantly larger than that of controls (14±12.8 microns; median, 14; P<0.0001). In addition, the vertical PPCI in PM eyes, but not in controls, was notably larger than the horizontal PPCI (mean difference, 55±30.4 microns; P<0.0001). In PM eyes, the PPCI strongly correlated with PMF height (R = 0.68; P<0.0001), inverse axial length (R = -0.71; P<0.0001), and corneal power (R = 0.49; P = 0.002), and the PMF height correlated strongly and inversely with the axial length (R = -0.62; P<0.0001). Conclusions: The PMF in PM eyes has characteristic morphologic SD-OCT features. The increased posterior pole curvature in PM and its significant correlation with the axial length, the PMF severity and keratometry established in this study suggest that PM eyes are not only shorter than normal, but seem to be abnormally shaped posteriorly, particularly along the vertical meridian. This factor may play a role in the pathogenesis and morphology of the PMF. © 2013 by the American Academy of Ophthalmology Published by Elsevier Inc.

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