What is Ocular Genetics?

Of the approximately 5000 genetic diseases and syndromes known to affect humans, at least one-third involve the eye. Due to advances in molecular genetics and sequencing methods, there has been an exponential increase in the knowledge of genetic eye diseases and syndromes.

Prevalence

  • More than 60% of cases of blindness among infants are caused by inherited eye diseases such as congenital cataracts, congenital glaucoma, retinal degeneration, optic atrophy, and eye malformations
  • In adults, cataract, glaucoma and age-related macular degeneration are three of the leading causes of blindness, and all appear to be inherited in a large portion of cases
  • Up to 40% of patients with certain types of strabismus have a family history of the disease

What are the common Genetic Ophthalmic Disorders?

Ophthalmic disorders can be classified according to the type of genetic abnormality, some of which are:

Monogenic

  • Corneal dystrophies
  • Albinism
  • Norrie disease
  • Retinoschisis
  • Choroideremia
  • Inherited retinal degenerative diseases (non-syndromic and syndromic)
  • Inherited optic neuropathies
  • Colour vision deficiencies
  • Retinoblastoma

Developmental

  • Anterior segment dysgenesis
  • Aniridia
  • Anophthlamos/microphthalmos/nanophthalmos
  • Coloboma

Complex

  • Cataract
  • Keratoconus
  • Fuchs endothelial corneal dystrophy
  • Age-related macular degeneration
  • Glaucoma
  • Pseudoexfoliation syndrome
  • Diabetic retinopathy

Why do you need to test for Genetic Ophthalmic Disorders?

  • Evidence suggests that the most common vision problems among children and adults are genetically determined (Eg: strabismus, amblyopia, refractive errors such as myopia, hyperopia, and astigmatism)
  • Genetic ophthalmic disorders include a large number of ocular pathologies which have autosomal dominant, autosomal recessive, or X-linked inheritance patterns or are complex traits with polygenic and environmental components
  • The presence of a particular ocular sign of a specific systemic disease is often the deciding factor in confirming the diagnosis of that disease. For example:
    1. Dislocated eye lens confirms Marfan’s syndrome
    2. Characteristic red spot in the eye is associated with Tay-Sachs diseases
    3. Blue sclera suggests Osteogenesis Imperfecta
    4. Aniridia indicates WAGR syndrome
  • Additionally, most of the ocular genetic disorders like Coloboma, Retinitis Pigmentosa, and Glaucoma show systemic, as well as, non-systemic manifestation

When do you need to get tested for Genetic Ophthalmic Disorders?

Early diagnosis will aid medical management of the condition and change in the treatment regimen. Genetic testing, when prescribed early, can detect the exact underlying defect at a molecular level which can be used to plan the medical and family management. The rarer the disease, the likelier it is caused by single-gene variation. Therefore, it is appropriate to offer genetic testing to patients whose clinical features indicate a Mendelian disorder for which the causative gene is known.

Who needs to get tested?

  • Individuals presenting with the symptoms of an eye disorder
  • Individuals with a standard preliminary test showing the possibility of an eye disorder
  • Individuals with a positive family history
  • Individuals without a positive family history but if any individuals in the family with symptoms resembling a specific disease condition
  • Prenatal testing is recommended only in families with affected individuals

Why recommend Actia for patients with Genetic Ophthalmic Disorders?

Actia offers a broad range of pre-designed gene mutation panels which have been developed with an in-depth disease understanding of genetic disorders incorporating the latest research in that particular domain. New updated technologies, helpful customer service, and clear result interpretation along with counselling sessions with our expert genetic counsellors equip us to provide you the best available support for your patients or families with Genetic Ophthalmic Disorders. Actia offers the following Ophthalmic gene panel tests

  • Corneal Dystrophy Gene Panel
  • Bardet-Biedl Syndrome Gene Panel
  • Cataract Gene Panel (Congenital/Developmental)
  • Choroideremia - CHM gene - Deletion/Duplication
  • Congenital Stationary Night Blindness Gene Panel
  • Leber Congenital Amaurosis Gene Panel
  • Microphthalmia and Anophthalmia Gene Panel
  • Optic Atrophy Gene Panel
  • RB1 Gene Analysis
  • RB1 Gene Deletion/Duplication Analysis
  • Retinal Degeneration Gene Panel
  • Usher Syndrome (USH2A) Deletion/Duplication Analysis
  • Usher Syndrome Gene Panel

What are the test methodologies?

1. Next-generation Sequencing (NGS) Using genomic DNA extracted from blood, the coding regions of all the genes are captured and sequenced simultaneously by NGS technology on an Illumina platform. The sequence data that is generated is aligned and analyzed for sequence variants. 2. Multiplex Ligation-Dependent Probe Amplification (MLPA) Deletion and duplication analysis of genomic DNA is carried out by MLPA. This method allows for the amplification of multiple targets with only a single primer pair. 3. Fragment Analysis PCR for Repeat Expansion Analysis These rely on the detection of changes in the length of a specific DNA sequence to indicate the presence of repeat expansions.

Test sample requirements

Blood (3-5ml in EDTA tubes)

Required forms
  • Relevant clinical information including all the clinical presentations and symptoms
  • Test request form
Turn around time (TAT)
  • 21 Working Days for NGS
  • 14 Working Days for MLPA
  • 21 Working Days for Sanger Sequencing
  • 7-14 Working Days for Fragment Analysis
  • 8-15 Working Days for Karyotyping

Extracted DNA samples (1µg high-quality DNA)

FREE GENETIC COUNSELLING

Actia offers all your patients FREE pre and post-test genetic counselling with our expert and certified genetic counsellors. Actia provides the best available support for your patients or families with

  • Latest technologies
  • Helpful customer service
  • Clear result interpretation
  • Counselling sessions with our Genetic Counsellors

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