Retinopathy of Prematurity

Linda MacKenna Ikuta, RN,MN,CCNS

The Eye

The Retina

Cut-away of the human eye showing its essential parts.

In front are the lenses (cornea and crystalline lens) that focus images on the retina.

The eye resembles a camera .The cornea and the crystalline lens act like a camera’s objective; they form an image on the retina, which is like the camera’s film. There the retina transforms the rays of light into nerve impulses that are carried by the optic nerve to the brain. It is in the brain that "seeing" occurs.

Definition

Retinopathy of Prematurity (ROP):1. disorder of the developing retinal vasculature

resulting from interruption of normal progression of newly forming retinal vessels.

2. Vasoconstriction and obliteration of the advancing capillary bed are followed in succession by neovascularization extending into the vitreous, retinal edema, retinal hemorrhages, fibrosis, and traction on, and eventual detachment of the retina.

3. In most cases, the process is reversed before firosis occurs.

Advanced stages may lead to blindness.

Definition

Retrolental fibroplasiaAs originally described, the condition was seen only in its most advanced form, after extensive fibrosis and scarring had already occurred behind the lens.

First described in 1942 by Terry. Name changed to ROP by international

committee established for the purpose of providing uniform classification for the disease.

Etiology

Vasoconstriction interrupts normal development migration of the retinal blood vessels from anatomically central optic nerve to the peripherally located ora serrata

Multiple proven as well as theoretical risk factors cause vasoconstriction of the developing retinal vasculature

Incidence

The overall incidence of ROP is 16-17% for all premature infants.

In infants with birth weight below 1251 grams, the incidence is 66%

Major risk factors include: decreased gestational age, decreased birth weight, and supplemental oxygen therapy. Associated risk factors include acidosis, apnea, patent Ductus arteriousus, septicemia, blood transfusions, and intraventricular hemorrhage

The Cause

From 16 weeks to birth, retinal blood vessels grow out from the optic nerve to reach the peripheral retina.  The last twelve weeks of a normal 40 week gestation are crucial in the development of fetal eyes.

In premature infants, the normal growth of blood vessels stops. It is theorized that the area without adequate blood supply emits a chemical trigger to stimulate growth of the abnormal vessels.

These vessels lead to a formation of a ring of scare tissue attached to both the retina and the vitreous gel that fills the center of our eyes. As the scar contracts, it may pull on the retinal creating a retinal detachment. Regardless of the gestation age at birth, ROP seems to occur at about 37 to 40 weeks.

The Cause

Our understanding of ROP is changing. Traditionally the view was that high oxygen exposure was the cause.

While it is certainly one of the major factors, studies now show that it is not just exposure to oxygen or other toxic agents after birth, but may also relate to actions that occur to the fetus prior to birth.

The Cause

Both chronic hypoxia (lack of oxygen) and intrauterine growth retardation may relate to ROP development.

As many as one third of ROP cases may be the result of prenatal conditions.

Light exposure has been suggested as another factor. To date, scientific studies have not confirmed light as a cause.

Classification

Doctors classify ROP by anatomical zones, clock dial like location within the eye and stages of severity. 

Zone 1 is the center of the retina while zone 3 is the far peripheral retina.

In 1984, an international classification system was developed. Stage 0 is the mildest form of ROP while Stage 5 is the most severe indicating total retinal detachment.  

International Classification System for ROP (ICROP) Zone I - Area centered on the optic disc and

extending from the disc to twice the distance between the disc and the macula.

Zone II - A ring, concentric to Zone I, which extends to the edge of the retina on the side of the eye toward the nose.

Zone III - The remaining crescent area of the retina toward the side and away from the nose.

Pediatrics 2006 Feb; 117:572-6.

Timing of Eye Exam

Pediatrics 2006 Feb; 117:572-6.

Who Gets ROP Screen?

ICROP

Classification System

Stage 1 ROP

Demarcation line -a flat, thin, whitish, clear-cut demarcation between vascularised and avascular retina (normal retina has a tenuous, non-linear, feathery border)

usually require nothing more than observation.

Stage 2 ROP

Elevated ridge - demarcation line now has "3" dimensions

The demarcation line extends anteriorly from the retinal plane as a ridge into the vitreous

usually require nothing more than observation.

Stage 3 ROP

Neovascularisation - extra-retinal, fibrovascular proliferate tissue

Extraretinal fibrovascular tissue begins to grow on the top of the ridge or posterior to the ridge and extends into the vitreous

Stage 3 ROP

Stage 3 ROP exists when these disturbing new blood vessels grow out from the ridge in the retina toward the center of the eye. If this blood vessel growth becomes severe and is accompanied by “plus” disease, the child may reach the point where treatment of the peripheral retina with laser (or rarely freezing) treatment is performed.

Stage 3 ROP

Plus Disease

Plus” disease is defined as enlarged and twisting blood vessels in the back part of the eye.

Plus Disease

Stage 4-5 ROP

The retina begins to detach from the posterior wall from traction exerted by the extraretinal fibrovascular tissue or from serious fluid developing behind it.

Peripheral retinal treatment can reduce, but not eliminate, the chance of the ROP progressing to the potentially blinding stages 4 and 5. When stage 4 or 5 ROP is reached, the retina is detached and other therapies can be perform

Stage 4-5 ROP

Surgical Procedures

Cryotherapy Laser photocoagulation Scleral Buckle Vitrectomy

Non-Surgical Treatment

Oxygen Light Vitamins DHEA Other Supplements

Prognosis

90 % of stage 1-2 regress spontaneously 50% of stage 3+ also regress spontaneously The other 50% stage 3+, the incidence of

severe visual impairment can be reduced by ~50% with treatment

Sequelae of regressed disease such as myopia, strabismus, amblyopia, glaucoma, and late detachment require regular follow-up

–Retinopathy of PrematurityRetinopathy of Prematurity

RetCamRetCam

–RetinoblastomaRetinoblastoma

–Shaken Baby SyndromeShaken Baby Syndrome

RetCam Exam

The RetCam II hand-held fiber optic camera can quickly and safely scan a premature infant’s eye in about five minutes.  It is used to diagnose retinopathy of prematurity.

Dr Moshfeghi Reviewing RetCam

Attached to the camera is the RetCam II wheeled console.  Darius Moshfeghi, MD, director of retinal surgery, demonstrates how this control panel, video monitor, and imaging system will be used by physicians and nurses at remotely-located neonatal intensive care units.

Images generated by the RetCam II Images generated by the

RetCam II can be referenced by Dr. Moshfeghi or one of his colleagues.  A recent study reported that users of the RetCam Digital Imaging System recommended medical intervention an average of two weeks earlier than did physicians performing bedside eye examinations.

SUNDROP

Stanford University Network for Diagnosis of Retinopathy of Prematurity (SUNDROP) at Packard Children’s Hospital allows Dr. Moshfeghi to receive computerized images of the retina of a child without having to travel to a child’s bedside.  What took hours out of his day before now takes minutes.

Coupling Gel

AlfonsoBarraquerSauer

Immature retina

Retinal vessels taper

Stage 1: Demarcation Line

Separates vascular from avascular retina

Stage 2: Ridge

Ridge occupies volume

Stage 3: Ridge + Epiretinal Fibrovascular Proliferation

Arborization of vessels into EFP lesion

avascular retina

shunt vessel

zone 1 zone 2

Aggressive Posterior ROP (AP-ROP)

regressed stage 3

Treated ROP with severe macular dragging

Lens sutures