Doctors - Cortical Visual Impairment (CVI)

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Doctors Information Resource (ROP) - Current Perspectives by Anne Fulton, MD

The following preliminary Current Perspective on Cortical Visual Impairment (ROP) is presented for review by leading medical specialists in the field of ophthalmology. The purpose is to encourage an exchange of informed opinions contributing to a dynamic up-to-date resource on the major eye disorders. Thus, these descriptions are continuously under development and are not offered as final statements.

Retinopathy of Prematurity

The hallmark of retinopathy of prematurity (ROP) is abnormal retinal vasculature in preterm infants. Retinal hypoxia instigates the formation of the abnormal retinal vasculature, mediated by Vascular Endothelial Growth Factor (VEGF). Despite the administration of supplemental oxygen to manage systemic hypoxia due to immature lungs, the oxygenation of retinal tissue is not adequate. The onset of ROP is at 30 to 32 weeks gestation (1) . Coincidentally, the development of the oxygen greedy photoreceptors is in the most rapid phase, just at the age of onset of ROP. Resolution of ROP, that does not require treatment, is at approximately term (40 weeks) (2) .

Of the nearly 4 million births per year in the United States , those born before 32 weeks gestation and weighing less than 1,250 g are at risk for ROP. Advances in neonatology have made possible survival of infants born as early as 23 to 24 weeks gestation. The lower the gestational age at birth and the lower the birth weight, the more likely the infant is to develop ROP. Approximately 80% of infants weighing less than 1,000 g at birth develop ROP, and of all infants born before 32 weeks, approximately half will get some ROP. Fortunately, in almost all, the ROP resolves without requiring treatment. Nonetheless, as many as 1,500 infants each year have ROP so severe the treatment (below) is required. Despite treatment, approximately 500 infants become legally blind from ROP each year.

Current management and treatment are heavily influenced by the International Classification of Retinopathy of Prematurity (3, 4) and the MultiCenter treatment trials (5, 6) . Not only has intervention, such as laser treatment, been evaluated, but the methods and timing of examination necessary to detect and monitor ROP effectively have been defined.

Acute ROP is characterized according to the ICROP system (3, 4) . Severity is indicated by Stage (1-5); retinal location by Zone (1-3) and extent (clock hours). The Zones are as shown in Fig. 2. Dilated and tortuous posterior retinal vessels are termed "Plus" disease. A recent meeting of an international committee of ophthalmologists expert in ROP also recognized "aggressive posterior ROP", formerly called "Rush Disease", an uncommon, very severe form of ROP, which, if untreated, would progress to Stage 5 (retinal detachment) (7) .

The Multi-center CRYO-ROP study of infants born in 1986-1988 showed cryo- therapy of threshold ROP was effective. The Early Treatment of ROP multi center study has further advanced management of ROP (8) . In ETROP, eyes receiving earlier treatment , that is, of prethreshold ROP, with laser to the peripheral avascular retina had better structural and acuity outcomes that did eyes managed with what had become conventional treatment of threshold ROP.

Despite improved management, ROP ranks among the five most common causes of children's bilateral, permanent blindness. Visual loss from ROP is due to retinal detachment and dysfunction of the neural retina (9) . Among those ROP patients who retain vision, high refractive errors, particularly myopia are common (10) . Additionally, children with a history of being born early may have co-morbidities including cerebral palsy, periventricular leukomalacia, and post-hemorrhagic hydrocephalus, each of which may be the basis for deficits in visual performance, for visual field defects and other cerebral visual deficits

1. Palmer EA, Flynn JT, Hardy RJ, et al. Incidence and early course of retinopathy of prematurity. The Cryotherapy for Retinopathy of Prematurity Cooperative Group. Ophthalmology 1991;98(11):1628-40.

2. Repka MX, Palmer EA, Tung B. Involution of retinopathy of prematurity. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Arch Ophthalmol 2000;118(5):645-9.

3. Anonymous. An international classification of retinopathy of prematurity. The Committee for the Classification of Retinopathy of Prematurity. Arch Ophthalmol 1984;102(8):1130-4.

4. Anonymous. An international classification of retinopathy of prematurity. II. The classification of retinal detachment. The International Committee for the Classification of the Late Stages of Retinopathy of Prematurity.[erratum appears in Arch Ophthalmol 1987 Nov;105(11):1498]. Arch Ophthalmol 1987;105(7):906-12.

5. Anonymous. Multicenter trial of cryotherapy for retinopathy of prematurity. Three-month outcome. Cryotherapy for Retinopathy of Prematurity Cooperative Group.[see comment]. Arch Ophthalmol 1990;108(2):195-204.

6. Multicenter Trial of Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity (STOP ROP). Monitoring adherence to protocol certification procedures. In: Manual of Procedures: Multicenter Trial of Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity (STOP ROP); 1993:10-2.

7. Quinn GE. Retinopathy of prematurity (ROP): recent advances and future directions for research. In: ARVO (Special Interest Group Meetings); 2004 April 28, 2004; Orlando, FL; 2004.

8. Early Treatment For Retinopathy Of Prematurity Cooperative G. Revised indications for the treatment of retinopathy of prematurity: results of the early treatment for retinopathy of prematurity randomized trial.[see comment]. Arch Ophthalmol 2003;121(12):1684-94.

9. Fulton AB, Hansen RM, Petersen RA, Vanderveen DK. The rod photoreceptors in retinopathy of prematurity: an electroretinographic study. Arch Ophthalmol 2001;119(4):499-505.

10. Quinn GE, Dobson V, Kivlin J, et al. Prevalence of myopia between 3 months and 5 1/2 years in preterm infants with and without retinopathy of prematurity. Cryotherapy for Retinopathy of Prematurity Cooperative Group. Ophthalmology 1998;105(7):1292-300.

11. Mayer DL, Fulton AB. Visual fields. In: Hoyt C, Taylor D, eds. Pediatric ophthalmology & strabismus. London: Elsevier Science; 2004.

Medical advice is not given or provided in this document or on this web site. Such information, which may be medical in nature, is presented as information only. Users pursuing any treatment or course of action must consult a properly licensed medical practitioner. Nothing contained, expressly or implied, in this document or on this web site is intended or shall be construed as medical advice.

If you have a question or comment about this article, or would like to contribute your opinion to this resource, please e-mail us at advisor@childrens.harvard.edu or participate in our bulletin board discussion on CVI.

Glossary of terms

Avascular
Not associated with or supplied by blood vessels

Cryotherapy
The local or general use of low temperatures in medical therapy

Myopia
A visual defect in which distant objects appear blurred because their images are focused in front of the retina rather then on it

Neonatology
The branch of pediatrics that deals with the diseases and care of newborn infants

Periventricular Leukomalacia
Periventricular leukomalacia (PVL) is caused by a lack of oxygen or blood flow to the periventricular area of the brain, which results in the death or loss of brain tissue.

Photoreceptors
A nerve ending, cell, or group of cells specialized to to sense ro receive light

Retinal Hypoxia
Deficiency in the amount of oxygen reaching retinal tissues

Tortous
Having or marked by repeated turns or bends, winding or twisting

Vasculature
Arrangement of blood vessels in the body or in an organ or body part

Vascular Endothelial Growth Factor
A protein that is a major factor in promoting the growth of new blood vessels.