The Dr. Bill Takeshita Foundation

Last Modified: Sat, 18 Aug 2007

View other Common Causes of Vision Impairment

Retinopathy of Prematurity (ROP) is one of the leading causes of vision impairment among newborn children. It is more prevalent among children born before 32 weeks of gestation or those who weigh less than 1500 grams. ROP is a condition where blood vessels of the retina do not develop normally and form scar tissue, which can obstruct vision or cause the retina to detach. Children with ROP may have a wide range of vision depending on the severity and location of the scar tissue. Visual acuity may range from 20/20 to total blindness. The early detection and monitoring of the retinas of premature children can prevent blindness of many premature infants.

The retina is the light-sensing tissue that receives light and sends information to the optic nerve to eventually be processed by the brain. In the growing fetus, blood vessels emerge from the central region of the retina and optic nerve at 16 weeks of gestation. The blood vessels grow and extend outward to supply blood to the peripheral and outer regions of the retina. However, the retinal blood vessels of premature children do not grow normally. They stop growing after the premature birth and consequently there are regions of the retina that do not receive normal blood supply and oxygen. Within days after birth, abnormal blood vessels develop and they tend to leak, forming scar tissue. The scar tissue can obstruct the manner that light enters the eye, causing blurred sight, distorted vision, and reduced peripheral vision. The scar tissue can also attach to the retina and tear or detach the retina, causing total blindness.

ROP is classified based on the severity and location of the abnormal blood vessels and scar tissue. Stages I and II are mild forms of ROP and the abnormal blood vessels may correct themselves. Vision can be as high as 20/20 and surgery is rarely necessary. Stage III ROP is a moderate form where the blood vessels can potentially develop into a more severe form of ROP. Laser and freezing treatments called cryotherapy are sometimes used to kill the retina so that it does not release factors that cause the formation of the abnormal leaky vessels. By sacrificing some of the retina, the formation of the abnormal vessels can be prevented. In Stage IV and V, the abnormal blood vessels leak factors that produce scar tissue. The scar tissue can proliferate and fill the entire eye or it can attach to the retina and pull the retina, causing a retinal tear or detachment. The detached retina can sometimes re-attach itself but frequently requires surgery in which a silicone belt called a sclearl buckle is wrapped around the eye to reattach the retina.

The location of the retinopathy, scar tissue, and detachment affects the level of vision. When the ROP occurs in the central region of the eye, (Zone 1), patients tend to have very poor central vision, blurred sight, reduced color vision, and reduced depth perception. When the abnormal blood vessel growth and scar tissue affect Zone 2, the clarity of sight may be preserved but patients may have problems seeing objects in their mid-peripheral vision. This can cause problems with finding things that they drop on the floor as well as difficulty with playing sports and walking up and down steps and curbs. ROP in Zone 3 tends to affect the extreme periphery and does not affect the central vision. Patients with ROP only in Zone 3 may have excellent clarity of sight but reduced peripheral vision.

The scar tissue from ROP can fill the entire eye, including the vitreous gel. The vitreous is the gel like substance that provides the eye with volume and prevents the eye from collapsing. In cases where the scar tissue extends from the retina and is entangled through the vitreous gel up to the crystalline lens, it is called Retrolental fibroplasias. This massive amount of scar tissue prevents light from entering the eye and striking the retina. The pupils of patients with retrolental fibroplasias are often white or cloudy rather than black. Surgeons will perform a lensectomy in which the crystalline lens is removed to provide access for surgeons to cut out the entangled scar tissue from the vitreous gel, a procedure called a vitrectomy. After a lensectomy and vitrectomy have been performed, glasses must be prescribed to assure that light focuses on the retina and sends information to the brain.

Children with ROP are often nearsighted (myopic) meaning that they are able to see near objects more clearly than distant objects. Glasses are required as early as possible to maximize the clarity of sight and to stimulate the visual centers of the brain. Bifocal spectacles may be helpful to provide children with higher levels of magnification as they learn to use their eyes and hands together. Students with nearsightedness may prefer to simply remove their glasses and hold their reading materials closer to their eyes and should be permitted to do so. It is very important that children have their eyes examined yearly because their glasses prescription often changes significantly and this can interfere with their ability to access information from the chalkboard and their books efficiently.

Strabismus is very common among children with ROP. Strabismus is the condition where the eyes are not aligned properly. Divergent strabismus is the term that describes eyes that turn outward while convergent strabismus is when the eyes cross. It is very important that children with strabismus and ROP are examined very carefully before having eye muscle surgery because the surgical alignment can cause double vision. In some cases of ROP, the scar tissue pulls the retina off of its normal position, causing the center of the retina to be located at the periphery of the eye. This condition is called a temporally dragged macula and causes children to appear to look “off to the side” rather than centrally when they look and reach for objects. The surgical correction of this condition can disrupt their functional vision significantly.

Children and adults with ROP generally are not blind and have functional vision. Approximately 75 percent of children who received surgery to treat ROP have vision that can be used to aid with walking and locating objects. In addition, a large percentage of these patients respond very well to low vision aids and are able to read print with the use of low vision devices, glasses, and assistive technology.

Recommendations

• Infants born prematurely must be followed by a pediatric ophthalmologist frequently after birth. ROP can develop within the first two to three days of life.
• Infants should be examined by the age of 6 months or younger. Glasses should be prescribed based on the visual developmental level of the children. For example, four-month-old infants should have their glasses prescribed to focus at their arms length rather than 20 feet.
• Infants will benefit from vision stimulation to maximally develop the visual cortex of the brain. For specific details, please see Developing Your Child’s Vision.
• Infants with nearsightedness may not require the use of glasses during their vision stimulation program. The glasses may provide improved distance sight and help children when they go for walks in their stroller. Glasses to correct for nearsightedness are also recommended during physical therapy when children learn to crawl and walk.
• A consultation by a low vision specialist and low vision aids are strongly recommended. s vision aids such as bioptic glasses, handheld telescopes, and video magnification systems can improve distance sight to 20/20 while specialized reading glasses, hand magnifiers, and closed circuit televisions can allow patients to read small print, read medication labels, and see photographs.
• Prescription filters and photochromic lenses may be very helpful for children with ROP who are sensitive to glare and bright light.
• Students will benefit from being positioned in the front portion of the class with their backs facing windows, doors, and glare sources. The use of a black chalkboard and bold architecture chalk are generally easier to see than dry erase boards due to the glare created by the white board. In the event that a dry erase board must be used, it is very helpful to only use bold black dry erase markers rather than colored markers.
• Students will benefit from having copies of material normally written on the board or presented on overhead transparencies. If PowerPoint presentations are used, a dark background with white letters typed in Arial or Tahoma fonts will improve readability for students with low vision.
• Students may have some difficulty seeing small objects such as a baseball while standing in the outfield. They may also have difficulty seeing in the direct sunlight and may prefer to wear their sunglasses and a hat. Students will benefit from additional time to adapt to the indoor lighting after entering the classroom from lunch or recess. Sports such as soccer, basketball, gymnastics, swimming, and golf may be easier to participate in rather than baseball or tennis.
• Computer users will benefit from changing the background of the display to a black or blue background with white letters. Enlargement of the font size will also increase readability. For information on how to modify the computer screen, see “Solutions to Help You Use Your Computer.
• Students may benefit from using specialized computer software and technology such as Zoom Text magnification software, scanning programs such as Open Book and Kurzweil, and Video Magnification systems. For more information, see Computer and Assistive Technology.
• Potential driving candidates with ROP who are interested in learning whether they have sufficient vision for driving should have a low vision examination by an optometrist who specializes in fitting bioptic driving glasses.
• Specific low vision aids that are often helpful to patients with ROP include:
  • 4x to 6x bioptic spectacles
  • 5x wide angle monocular telescope
  • Single vision reading glasses and high add bifocals
  • Prescription CPF, Transitions, Melanin, and NoIR filters
  • 3x to 8x illuminated hand and stand magnifiers
  • ZoomText magnification software and JAWS screen reading programs are very helpful for computer users.
• For more information, please see Low Vision Rehabilitation