Retinal Detachment

The retina is critical to your eyesight since it sends messages to the brain via the optic nerve. When the retina gets separated from the back wall of the eye, it leads to a condition of retinal detachment. Retinal detachment leads to loss of function of the retina due to loss of blood supply and nutrition. It is imperative that a condition of retinal detachment be attended to immediately to avoid permanent loss of vision. Some patients may suffer a condition where there is a tear in a small area of the retina. Rhegmatogenous detachment of the retina occurs when there is a tear in the retina. On the other hand, tractional retinal detachment is caused due to scar tissue on the retina. When retinal detachment occurs due to an inflammatory disease or injury, it is a case of exudative retinal detachment.

Retinal detachment can be caused due to advanced diabetes or an inflammatory disease. Trauma can also cause the retina to get detached. Any leakage of vitreous liquid accumulating under the retina can cause the retina to get detached. This can happen due to aging. Persons who suffer weak areas in the retinal periphery or have undergone severe eye injury are at risk for retinal detachment. Signs of retinal detachment include sudden flashes of light in the affected eye and blurred vision. Many floating debris might appear in the vision.

The size and location of the retinal detachment decides the kind of treatment that would be most suitable. Small retinal tears are treated with cryopexy or retinal cryotherapy that involves freezing of the area around the tear. Laser surgery is used to fuse the retina to the underlying tissue. Laser surgery can be done sans incision and the patient suffers minimal discomfort. More complex cases would require vitrectomy and scleral buckling procedures to seal the detached retina. Surgery is not always a guarantee of restored vision as it's success hinges on how much of the retina is detached and for how long.

Coloboma

Coloboma refers to a gap or defect in any of the structures of the eye such as iris, retina, ciliary body, lens, choroid and optic disc. It normally occurs at the lower quadrant of the eye and can involve one or both the eyes. It is a congenital defect and the condition occurs due to the improper development of the eyes during pregnancy. If the the child is born with coloboma, the eye pupil will be shaped like a key hole or a notch. Coloboma can occur in isolation or can occur along with other chromosomal abnormalities. Persons suffering coloboma also might have a condition called microphthalmia. Other eye abnormalities that might accompany coloboma are cataract, glaucoma, myopia, retinal detachment and nystagmus. When coloboma occurs by itself, it is described as nonsyndromic or isolated.

Normally the baby eyes in the womb will develop between 4 and 15 weeks. Before even the eye begins to form, optic fissure is formed to supply the required nourishment to the eye. Optic fissure closes by itself once the eyes are formed completely. Sometimes the optic fissure fails to seal thus leaving a gap, causing coloboma. Coloboma can also result from genetic syndrome, but not all the cases have a family history of coloboma, implying that it can occur even without genetic disorders.

Coloboma can affect different tissues of the eye. It is found in iris and ciliary body if the anterior portion of the optic fissure does not close properly. Iris coloboma is the most common defect that affects the lower part of the colored portion of the eye. Here the pupil of the eye appears like a keyhole and may also looks enlarged. Babies with iris coloboma develop 'cat eyes'. It can also appear as a split in the iris from the pupil to the edge of the iris. However the vision and the functioning of the eye are normally not affected with front eye coloboma. Children with iris coloboma may experience light sensitivity due to the large pupil. The condition may extend to the back of the eye if the posterior portion of the eye does not close properly. In such cases, the retina or the optic nerve that connects the eye to the brain may be affected. The child may have limited or no vision.

Diagnosis of Coloboma

Coloboma is often diagnosed by it's appearance as a notch or a keyhole shape of the pupil. If the coloboma is suspected, a detailed examination by the ophthalmologist is recommended to assess how much of the eye has been affected by coloboma. Diagnostic tests like visual acuity test, refraction test, and detailing of symptoms is done to aid the diagnosis.

Treatment of Coloboma

There is no effective treatment that can correct or fix the missing structure in coloboma. The condition can only be monitored from time to time and be managed effectively to enjoy the optimum possible function of the eye. In case of iris coloboma, children may be prescribed glasses or contact lenses for better vision and appearance. Sunglasses are recommended in case coloboma is causing sensitivity to light.

When the coloboma extends to deeper layers like choroid, retina and optic nerve, patients are at risk for developing retinal detachment. In such cases one has to consult a retinal specialist on a regular basis. Normally patients with retina, choroid and optic nerve colobomas are supported with low vision aids.

Electroretinography

Electroretinography or ERG is an eye test used to detect the abnormal function of the retina. The rods, cones and the ganglion cells of the eyes are examined during this test. An electrode is placed on the cornea to measure the electrical response to the light in the retina and the back of the eye. This test helps identify any defects in the retina and can help in identifying if retinal surgery is required.

ERG Procedure

Patient's eyes are dilated and anesthetic drops are placed on the eyes. Eyes are kept open using a speculum and an electrode is placed in the eye. Another electrode is placed on the skin. The patient is made to watch a standardized light stimulus or flash ERG. The signal received is measured according to its amplitude. The readings are taken when the room is normally lit and when the room is dark. If the tests are normal, it will display a normal A and B pattern for each flash.

Abnormal results can indicate:

• Congenital night blindness
  
• Cone Rod Dystrophy (CRD)
  
• Retinal detachment
  
• Vitamin A deficiency
  
• Trauma