Usher Syndrome

Usher Syndrome 

What is Usher syndrome?

is a relatively rare genetic disorder caused by a mutation in any one of 10 genes that affects both hearing and vision

Photograph of the retina of a patient with Usher syndrome (left) compared to a normal retina (right). The optic nerve (arrow) looks very pale, the vessels (stars) are very thin and there is characteristic pigment, called bone spicules (double arrows)

There are three clinical types of Usher syndrome:

type 1, type 2, and type 3. In the United States, types 1 and 2 are the most common types

type 1

Children with type 1 Usher syndrome are profoundly deaf at birth and have severe balance problems. 

Vision problems most often begin with difficulty seeing at night, but tend to progress rapidly until the person is completely blind.

Type 2

Children with type 2 Usher syndrome are born with moderate to severe hearing loss and normal balance.

The vision problems in

type 2 Usher syndrome tend to progress more slowly than those in type 1, with the onset of RP often not apparent until the teens.

Type 3

Children with type 3 Usher syndrome have normal hearing at birth. Although most children with the disorder have normal to near-normal balance, some may develop balance problems later on.

Night blindness usually begins sometime during puberty. Blind spots appear by the late teens to early adulthood, and, by mid-adulthood, the person is usually legally blind.

How is Usher syndrome treated?

Currently, there is no cure for Usher syndrome. The best treatment involves early identification so that educational programs can begin as soon as possible. The exact nature of these programs will depend on the severity of the hearing and vision loss as well as the age and abilities of the person. Typically, treatment will include hearing aids, assistive listening devices, cochlear implants, or other communication methods such as American Sign Language; orientation and mobility training; and communication services and independent-living training that may include Braille instruction, low-vision services, or auditory training.

Some ophthalmologists believe that a high dose of vitamin A palmitate may slow, but not halt, the progression of retinitis pigmentosa. This belief stems from the results of a long-term clinical trial supported by the National Eye Institute and the Foundation for Fighting Blindness. Based on these findings, the researchers recommend that most adult patients with the common forms of RP take a daily supplement of 15,000 IU (international units) of vitamin A in the palmitate form under the supervision of their eye care professional. (Because people with type 1 Usher syndrome did not take part in the study, high-dose vitamin A is not recommended for these patients.)

Asteroid hyalosis :

Asteroid hyalosis is a degenerative condition of the eye involving small white opacities in the vitreous humourClinically, these opacities are quite refractile, giving the appearance of stars (or asteroids) shining in the night sky—except that ocular asteroids are often quite mobile. Ocular asteroids must be distinguished from the more common typical vitreous floaters, which are usually fibrillar or cellular condensates. 

The cause of asteroid hyalosis is unknown, but it has been associated with diabetes mellitus, hypertension, hypercholesterolemia

asteroid hyalosis is considered to be an age related change.

 The asteroid bodies are made up of hydroxylapatite, which in turn consists of calcium and phosphates or phospholipids. While asteroid hyalosis does not usually severely affect vision, the floating opacities can be quite annoying, and may interfere significantly with visualization and testing of the retina. 

While treatment of asteroid hyalosis is usually unnecessary, vitrectomy may occasionally be indicated, for both diagnostic and therapeutic purposes.

CORNEAL NEOVASCULARIZATION

Corneal neovascularization is abnormal blood vessel growth in the cornea from the limbus.

A normal, healthy cornea has no blood vessel growth. Blood vessels normally circle the cornea at the limbus, the junction of the clear cornea and the white part of the eye.

WHAT CAUSES CORNEAL NEOVASCULARIZATION?

• The main underlying cause is lack of oxygen to the cornea. 

• Long-term use of contact lenses 

• toxic contamination from lenses or solution

•  trauma or infection

•  chemical burns

• lens deposit buildup can also be a cause.

 When contact lenses or some other condition interferes with the transport of oxygen to the cornea, the eye responds by growing extra blood vessels to help supply oxygen and nutrients to the oxygen-depleted tissues. The longer a lens is worn (more than 10 hours a day), the greater the risk of corneal hypoxia (lack of oxygen) and the chance of developing corneal neovascularization. When blood vessels extend beyond 2mm from the margin of the cornea, the condition needs to be treated, or permanent intolerance to contact lens or vision loss can occur.

• Corneal neovascularization may also be caused by 
• infections, trauma to the eye,
•  chemical burns, 
• immune system diseases and certain other eye conditions, such as uveitis, glaucoma 

HOW IS CORNEAL NEOVASCULARIZATION DIAGNOSED?

Actively engorged blood vessels can be seen in the white of the eye. Other symptoms include the following:

• Pain

• Redness around the cornea

• Tearing

• Light sensitivity

• Decreased vision or blurring when wearing contact lenses

• Intolerance to contact lens after wearing them for a short time

HOW IS CORNEAL NEOVASCULARIZATION TREATED?

• Treatment of corneal neovascularization depends on the severity of the condition and the cause. Corticosteroids may be prescribed to reduce vascularisation. 

• Surgical options include laser photocoagulation.

•  Reduction or temporary cessation of contact lens wear time may be necessary to allow the tissues to heal.

•  A contact lens refit with an oxygen permeable or high oxygen transmissible lens is an option that works for many people

 Once the condition has healed, contact lens wearers should pay close attention to adequate corneal lubrication.

PEDIATRIC PRESCRIPTION

Guidelines for spectacle prescribing in infants and children

Age group	Hypermetropia	Myopia	Astigmatism	Anisometropia
Infant --> 2yrs	>Up to +5D prescription +2D less than the error >For higher RE more than 2D can be subtracted but the pt should not be left mor than 4 hyp >Error less than 4D no need pre-scrip >Hyperopic children in this age group with more than .75D of astigmatism should have astigmatism correction >Pt with >2.5D of hyp should be FU yearly	>Up to -2 can be tolerated by pt in this age group >Higher amount of myopia should be correct less than 1 of the full correction >Astigmatism of .75D or more should be fully corrected	>1.5 D requires full correction >.5 less than full can be prescribed	>Hyperopia difference 1.5 should be pre scrip >Myopic 3D >Astigmatism of .75 or more in one eye full astigmatic correction >With astigmatism in ou the pt should be corrected so as leave more than .5D incorrect end in each eye
2---> 5 yrs In this age group if there is no significant refraction error and there is no symptoms myopia , hyperopia less than 3 and astigmatism less than .75 then there is no need for glasses	>Up to 4 with normal VA and no ocular symptoms no need for glasses >Greater than 4 and no ocular symptoms glasses are prescribed with 2 less than full and full astigmatism correction >FU	>These pt can tolerate RE of less than 1D >Large RE will require full correction with full astigmatism correction	>For astigmatism between 1 to 2 glasses are prescribed foe eye tasks only >For astigmatism >2 full correction and full time wear is recommended >When associated with hyp astigmatism as low as .75 should be prescribed	>Of 1.5 and no associated ocular symptoms glasses may not be prescribed but 6 month FU >If ocular symptoms are present , glasses are recommend to maintain fusion >For hyperopic pt glasses are prescribed 1.5 less than full equally in both eye so that equal accommodation in ou >For myopic pt full RE is given >For astigmatism any difference of .75D or more between the two eyes requires >For higher degrees of anisometropia (+5) CL are more useful to pt
5 yrs ---> and above Should bring VA to 20/20	>If pt shows symptoms RE of as low as +3D half the full correction is given with full astigmatic correction if needed >More than 3 glasses are prescribed with 2 less than full correction >FU	>Great than .75 the full correction is prescribed	>Pt with .5 to 1 complain because they are making constant efforts to keep their vision clear >With errors over .75 full correction should prescribed Care should be taken in prescribing for children with errors greater than 1.5D as they may not tolerate the glasses initially because of change in shape of objects the prescription should be worn constantly until the pt has adapted to their new perception of their surrounding.	>If error differ by 1.5Ds or 1Dc then amblyopia is likely to be present glasses and occlusion therapy are recommended.

Brown Syndrome

Brown Syndrome






What is Brown syndrome?
Brown syndrome is also known as Superior Oblique Tendon Sheath syndrome.
It is a mechanical problem in which the superior oblique muscle is unable to lengthen and therefore does not move freely. 
This makes looking up and in with the affected eye difficult Brown Syndrome may be present at birth (congenital) or begin later. It may be constant or intermittent.

What do the eyes of patients with Brown syndrome look like?

The eyes usually look normal except in side gaze positions. In side gaze (looking away from the affected side), one eye appears higher than the other, particularly when looking up. A vertical misalignment is sometimes noted when looking straight ahead.

Often the higher eye is mistakenly presumed to be the abnormal eye, but it is the lower eye that is affected. Brown syndrome causes the lower eye to have trouble looking upward and inwards towards the nose. Essentially the affected eye is “tethered” or held down by the tight superior oblique tendon.

What causes Brown syndrome?
The eyes usually look normal except in side gaze positions. In side gaze (looking away from the affected side), one eye appears higher than the other, particularly when looking up. A vertical misalignment is sometimes noted when looking straight ahead.

Often the higher eye is mistakenly presumed to be the abnormal eye, but it is the lower eye that is affected. Brown syndrome causes the lower eye to have trouble looking upward and inwards towards the nose. Essentially the affected eye is held down by the tight superior oblique tendon.

Is Brown syndrome hereditary?
Hereditary cases of Brown syndrome are rare. Most cases arise without a family history .

Can Brown syndrome be acquired?
Acquired Brown syndrome is uncommon but may be seen following surgery, after trauma or in association with inflammatory diseases. Trauma can cause a Brown Syndrome if a blunt object hits the eye socket in the upper inside corner near the nose. Surgery for the eyelid, frontal sinus, eyeball (retinal detachment) and teeth (dental extraction) have been linked to acquired Brown syndrome. Inflammation of the tendon-trochlea complex (from adult and juvenile rheumatoid arthritis, systemic lupus erythematosus and sinusitis) can be associated with development of the problem. Sometimes the cause is never identified.

How is Brown syndrome diagnosed?
The eyes are usually straight when looking directly ahead and down. The hallmark sign of Brown syndrome is decreased ability to look upward and inward. In some situations the eyes turn outward (exotropia) when looking up.

Brown syndrome can be associated with an abnormal head position (chin up, face turn, head tilt) for better eye cooperation. The affected eye can get “stuck” after looking up or down for long periods of time. When the eye becomes unstuck, a click is often heard and may be accompanied by pain or discomfort.

Brown syndrome may be more noticeable in children since they often look upward toward adults.

Does Brown syndrome affect one or both eyes?
Ninety percent of patients have only one affected eye, more commonly the right.

Does Brown syndrome cause eye problems besides abnormal eye movements?
Some children with Brown syndrome have poor binocular vision (which can result in poor depth perception), amblyopia or exotropia.

How is Brown syndrome treated?
Treatment recommendations for Brown syndrome vary according to the cause and severity of the movement disorder. Close observation alone is usually sufficient in mild cases. Visual acuity and the ability to use both eyes at the same time (binocular vision) should be monitored closely in young children. Nonsurgical treatment is often advised for recently acquired, traumatic and variable cases. Systemic and locally injected corticosteroids have been used to treat inflammatory cases of acquired Brown syndrome. Non-steroidal anti-inflammatory agents (like Ibuprofen) have also been used. Surgical treatment is usually recommended if any of the following are present: eye turns down when looking straight ahead, significant double vision, compromised binocular vision or pronounced abnormal head position. More than one surgery may be needed for optimal management.

Albinism and the Vision Problems

What is Albinism?

The word “albinism” refers to a group of inherited conditions. People with albinism have little or no pigment in their eyes, skin, or hair. They have inherited altered genes that do not make the usual amounts of a pigment called melanin. One person in 17,000 in the U.S.A. has some type of albinism. Albinism affects people from all races. Most children with albinism are born to parents who have normal hair and eye color for their ethnic backgrounds. Sometimes people do not recognize that they have albinism. A common myth is that people with albinism have red eyes. In fact there are different types of albinism and the amount of pigment in the eyes varies. Although some individuals with albinism have reddish or violet eyes, most have blue eyes. Some have hazel or brown eyes. However, all forms of albinism are associated with vision problems.

0. Vision Problems 

   
   
   
   
   
   People with albinism always have problems with vision (not correctable with eyeglasses) and many have low vision. The degree of vision impairment varies with the different types of albinism and many people with albinism are “legally blind,” but most use their vision for many tasks including reading and do not use Braille. Some people with albinism have sufficient vision to drive a car. Vision problems in albinism result from abnormal development of the retina and abnormal patterns of nerve connections between the eye and the brain. It is the presence of these eye problems that defines the diagnosis of albinism. Therefore the main test for albinism is simply an eye examination.
   

   Vision Rehabilitation

   Eye problems in albinism result from abnormal development of the eye because of lack of pigment and often include:
   

   • Nystagmus: regular horizontal back and forth movement of the eyes
   • Strabismus: muscle imbalance of the eyes, “crossed eyes” (esotropia), “lazy eye” or an eye that deviates out (exotropia)
   • Photophobia: sensitivity to bright light and glare
   • People with albinism may be either far-sighted or near-sighted and usually have astigmatism
   • Foveal hypoplasia: the retina, the surface inside the eye that receives light, does not develop normally before birth and in infancy
   • Optic nerve misrouting: the nerve signals from the retina to the brain do not follow the usual nerve routes
   • The iris, the colored area in the center of the eye, has little to no pigment to screen out stray light coming into the eye. (Light normally enters the eye only through the pupil, the dark opening in the center of the iris, but in albinism light can pass through the iris as well.)

   For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery to correct strabismus may improve the appearance of the eyes. However, since surgery will not correct the misrouting of nerves from the eyes to the brain, surgery will not improve eyesight or fine binocular vision. In the case of esotropia or “crossed eyes,” surgery may help vision by expanding the visual field (the area that the eyes can see while looking at one point).
   People with albinism are sensitive to glare, but they do not prefer to be in the dark, and they need light to see just like anyone else. Sunglasses or tinted contact lenses help outdoors. Indoors, it is important to place lights for reading or close work over a shoulder rather than in front.
   Various optical aids are helpful to people with albinism and the choice of an optical aid depends on how a person uses his or her eyes in jobs, hobbies, or other usual activities. Some people do well using bifocals which have a strong reading lens, prescription reading glasses, or contact lenses. Others use hand-held magnifiers or special small telescopes and some prefer to use screen magnification products on computers.
   Some people with albinism use bioptics, glasses which have small telescopes mounted on, in, or behind their regular lenses, so that one can look through either the regular lens or the telescope. Newer designs of bioptics use smaller light-weight lenses. Some states allow the use of bioptic telescopes for driving.
   Optometrists or ophthalmologists who are experienced in working with low vision patients can recommend various optical aids. Clinics should provide aids on trial loan and provide instruction in their use. The American Foundation for the Blind maintains a directory of low vision clinics. In Canada, support is available from the Canadian National Institute for the Blind.