Infant's visual system, in contrast to other organs of the body has a significant degree of plasticity, with most of the increase from newborn to adult values occurring during the first 12 to 18 months of life (<xref ref-type="bibr" rid="bib001">1</xref>). During the rapid phase of growth compensatory changes in the eye maintain the vision close to emmetropia and any insult thereby either prenatal or postnatal is likely to have effect on the vision of the child. Advancements in medical knowledge and increased availability of expertise in the last two decades have cumulated to greatly improved survival rates among premature and low birth weight neonates. This has resulted in increased prevalence of the children with severe neurosensory disorders and high ocular morbidities. It is because of this reason that with improved preterm survival Retinopathy of Prematurity (ROP) has become amongst the most important cause of blindness in developed nations and fourth important cause in the developing countries after eye injuries, infections and vitamin A deficiency (<xref ref-type="bibr" rid="bib002">2</xref>). Retinal causes of visual loss present during infancy including retinal dystrophies and retinopathy of prematurity (ROP) account for 20-30% of the childhood blindness in south Asia, Latin America and Europe (<xref ref-type="bibr" rid="bib003">3</xref>). The literature to date suggests that between 24 to 57% of prematurely born children with ROP are myopic at 24 months post term. Refractive errors, strabismus, amblyopia and delayed visual maturation have been reported in association with premature and very low birth weight births even without ROP. Neonates who sustain severe birth asphyxia and develop cerebral palsy are also known to have high ocular morbidity to the extent of 50-75 %, due to optic atrophy, strabismus and refractive errors (<xref ref-type="bibr" rid="bib004">4</xref>).Since there are no effective preventive strategies for various causes of visual handicaps, the emphasis is currently on screening all high-risk babies likely to develop visual problems or handicaps and their timely intervention.<sec id="sec001"><title>High Risk Situations

JNNFI

Journal of Neonatology

0973-2179

National Neonatology Forum

jn-18-2-005

Symposium on Follow-up Care of NICU Graduates

Visual follow up of a high risk neonate

Chellani

Harish

Awasthy

Neeraj

Kumar

Harsh

Department of Pediatrics, Vardhman Mahavir Medical College and Safdarjung Hospital and Apollo hospital∗ Delhi 110029, India.

4-62004

1822838

Infant's visual system, in contrast to other organs of the body has a significant degree of plasticity, with most of the increase from newborn to adult values occurring during the first 12 to 18 months of life (<xref ref-type="bibr" rid="bib001">1</xref>). During the rapid phase of growth compensatory changes in the eye maintain the vision close to emmetropia and any insult thereby either prenatal or postnatal is likely to have effect on the vision of the child. Advancements in medical knowledge and increased availability of expertise in the last two decades have cumulated to greatly improved survival rates among premature and low birth weight neonates. This has resulted in increased prevalence of the children with severe neurosensory disorders and high ocular morbidities. It is because of this reason that with improved preterm survival Retinopathy of Prematurity (ROP) has become amongst the most important cause of blindness in developed nations and fourth important cause in the developing countries after eye injuries, infections and vitamin A deficiency (<xref ref-type="bibr" rid="bib002">2</xref>). Retinal causes of visual loss present during infancy including retinal dystrophies and retinopathy of prematurity (ROP) account for 20-30% of the childhood blindness in south Asia, Latin America and Europe (<xref ref-type="bibr" rid="bib003">3</xref>). The literature to date suggests that between 24 to 57% of prematurely born children with ROP are myopic at 24 months post term. Refractive errors, strabismus, amblyopia and delayed visual maturation have been reported in association with premature and very low birth weight births even without ROP. Neonates who sustain severe birth asphyxia and develop cerebral palsy are also known to have high ocular morbidity to the extent of 50-75 %, due to optic atrophy, strabismus and refractive errors (<xref ref-type="bibr" rid="bib004">4</xref>).Since there are no effective preventive strategies for various causes of visual handicaps, the emphasis is currently on screening all high-risk babies likely to develop visual problems or handicaps and their timely intervention.<sec id="sec001"><title>High Risk SituationsPrematurity and low birth weight

Prematurity is the single most important factor in the development of ROP. Its incidence and severity is inversely related to the gestational age or birth weight of the infant. The incidence of ROP in the developed nation is 38% to 52 % (5,6). The Indian experience on ROP incidence varies from 20-57% among babies less than 1500g and 73.3 % to 90% amongst <1000g babies (7-9). Furthermore, severe ROP (stage 3-5) is seen almost exclusively in infants of birth weight less than lOOOg. As perthe National Perinatal Database 10, the incidence of ROP was 0.1 % amongst 38592 intramural live born babies in the 16 centers of the country in 1995. Since most of the centers did not have any regular program for screening preterm babies, this is probably under estimation of the magnitude of the problem our hospital data which has started regular screening program for ROP and other eye problems for the last 4 years has shown ROP incidence of 44% among babies less than 1500 g.

Hypoxia and hyperoxia

It is evident that careful control-of oxygen administration will reduce the incidence of ROP, but it is difficult to define a safe level of oxygen. The American Academy of Pediatrics has recommended that arterial oxygen concentrations be kept in the region of 50-80mmHg during neonatal care and this view has gained general acceptance. In our center oxygen supplementation for more than 48 hours and requirement of Fio2 more than 40% for 24 hours emerged significant risk factors on univariate analysis. The fluctuation of oxygen saturation of more than 30% on transcutaneous monitoring or 40 mm Hg on ABG analysis in serial observational readings to be significantly associated with ROP a fact supported by other studies (5). It is recommended that oxygen saturation to be kept between 88-92%, to reduce and possibly prevent development of severe form of ROP.

Intrauterine infections

Babies with congenital infections are at risk for development of a variety of ocular lesions. In the study by Binquet et al, infants who were followed for a median period of 6 years, 24% had at least one retinochoroidal lesion. Bilateral impairment of visual activity was not observed in their series.

Interventricular/Peri ventricular hemorrhage (PVH)

Factors which regulate cerebral blood flow act in similar ways on the regulation of retinal circulation and several of these factors have been implicated in the etiology of PVH; notably hypercarbia, asphyxia and hypoxemia. Procianoy et al (11), reported an association between periventricular hemorrhage and ROP. In the study by Hungerford et al, this association was stronger than that between ROP and respiratory illness or treatment with oxygen. In our study 62.5% had ROP stage 2 or higher compared to 12.1 % with no interventricular/periventricular hemorrhage Birth asphyxia

Visual Screening Protocol

Standard of practice now demand carefully timed actual examinations of at-risk infants by an ophthalmologist experienced in the examination of such infants to minimize the risk of visual loss. The following table describes the recommendation for screening of neonates for eye diseases at birth: Table 1

Screening of neonates for eye diseases at birth.

Examination should be carried out with a torch to look for:

Buphthalmos

Opthalmia neonatorum

Obvious developmental abnormalities (such as micropthalmos and anopthalmos).

Nystagmus

Squint

Retinopathy of prematurity (examination with an indirect opthalmoscope), according to indications.

Screening Protocol for ROP

Because no early clinical signs or symptoms indicate developing ROP, early and regular retinal examination is necessary. The goal of an effective screening program is to identify few preterm infants who require treatment for ROP from among the much larger number born each year while minimizing the number of stressful examinations required for these small infants.

Whom to Screen

Each screening program guidelines designed to implement an evolving standard of care has some inherent defect, such as over referral or under referral and can not by its very nature duplicate the precision and rigor of a scientifically based clinical trials. Based on the information published so far American Association of Pediatrics (AAP) and American Association for Ophthalmologists (AAO) recommends infants with birth weight less than 1500 grams or gestational age less than 32 weeks as well as selected infants between 1500-2000g weight and unstable clinical course should be screened for the ocular anomalies viz. ROP Post concept ional age seems to be more important in the onset of ROP rather than the chronological age. Screening guidelines that are being followed at A.I.I.M.S (13) and Safdarjung Hospital are as follows:

All babies </ = 1500gram birth weight

All babies </ = 34 weeks of gestational age

All premature babies with oxygen exposure more than 3 days

All premature babies between 1500-2000 grams, which the neonatologist thinks, may be high risk for ROP because of: septicemia, multiple blood transfusions, multiple apneic spells, low pH, respiratory distress syndrome.

On the screening day, babies are to be decided and evaluated by the neonatologist in charge.

When to Screen

The timing of occurrence of ROP is related to the maturity of retinal vessels and thus postconceptional age. The median postconceptional age at the onset of stage 1 ROP, prethreshold disease and threshold disease are 34, 36 and 37 weeks respectively. It is therefore important to, screen babies:

first at 32 weeks of post conceptional age;

if born before 28 weeks of gestational age then first examination at 4 weeks after birth or 32 weeks post conceptional age which ever is earlier;

not to see child within first 2 weeks of birth (if born at 32 weeks see at 34 weeks, if at 31 weeks see at 33 weeks)

It is suggested that large nurseries that are unable to keep track of postconceptional age should get all babies examined at 4-5 weeks of postnatal age initially. Follow up after the first screening to be decided by the ophthalmologist and has to be carried out biweekly till the full retinal vascularization has occurred or prethreshold ROP is diagnosed. Once the infant has been determined on first examination to be at risk for ROP, the examination should be frequent. Infants reaching threshold disease (stage 3 ROP in zone I and II or more contiguous clock hours or 8 contiguous clockhours with plus disease i.e. posterior retinal dilatation and tor tuosity) should receive ablative therapy within 72 hours of diagnosis.

How to Screen

Place: The examination should be performed in nursery or temperature controlled room near nursery (preferably under radiant warmer) by an ophthalmologist with sufficient regular experience and knowledge in the examination of preterm infant for ROP to identify the location and sequential retinal changes in this disorder using monocular indirect opthalmoscopy. The findings should be recorded using the International Classification of Retinopathy of Prematurity (14).

Items to be kept ready for examination

Speculum (pediatric) : one for each baby to be examined

Scleral indentor/wire vectis : one per each baby, if feasible Both these to be made in 1 packet for each baby and sterilized by available means i.e. immersion in cidex for half-hour if these are not disposable. Auto calved instruments should be preferred where available. Rim of the indirect lens should be wiped with alcohol swab between examinations of each infant.

A trolley on which these items are to be put to carried to various parts of the nursery

An experienced neonatal nurse should be present to assist the doctor in holding the child

The neonatologist to be present to watch for vital signs and side effects of drugs and the procedure viz bradycardia, apnea.

Follow universal precautions throughout the procedure

Preparation and monitoring for retinal examination:

The neonatologist should assess the stability of the infant for eye examination.

Dilatation protocol:

One drop of tropicamide 1 % and one drop of phenyepherine 2.5% to be installed 4 times at 10 minutes interval starting 1 hour before examination. Alternatively pupils are dilated by instillation of the cyclomydril eye drops (0.2% cyclopentolate hydrochloride and 1% phenyepherine hydrochloride), 30 - 60 minutes before the examination, put 1 drop at a time only.

Excess of phenyepherine 2.5% should be avoided as it can cause hypertensive encephalopathy and peri ocular blanching. Wipe excess drops. Close the puncta by using swab stick pressure on medial cantus if necessary.

Tuberculin syringe may be used to decrease drop size

In case routine dosage is not dilating the pupil watch out for plus disease where pupils become rigid; this may result in excess drops and side effects.

Preparation of the patient:

Parents should be informed about the procedure

Last feed should be at least one hour before examination and delay feeding for ½2. - 2 hours after examination.

An experienced neonatal nurse should assist the ophthalmologist in the examination and monitor vital signs including apneas. Equipment for resuscitation including bag and mask, oxygen and i.v. atropine should be readily available. These infants tend to have bradycardia during and after the exams (up to 72 hours) because of the pressure on the eyeball especially after cryotherapy (oculocardiac reflex). The abdominal girth, blood pressures and breathing should be monitored following the exam.

A dedicated nurse or a health care professional should be in charge of keeping a log of all ‘at risk’ infants and their examinations results till they are mature. The log should include information such as gestational age, birth weight, date of birth, antenatal dexamethasone and presence and absence of risk factors, duration of ventilation, duration of oxygenation, parents address and telephone number etc. A preliminary exam date should be assigned to at risk infants at the time of admission and the parents should be informed about the nature of the eye exam and ROP, early on and periodically. If infants are discharged before the retina matures, a follow up appointment should be arranged and the importance of the eye examination should be explained to the parents.

Intrauterine Infection, Asphyxiated Babies

There are no definite guidelines available as for ROP, however screening for intrauterine infections such as Toxoplasmosis, Rubella, C.M.V and Herpes should be done to look for chorioretinitis and other ocular morbidities like cataract, glaucoma and corneal clouding at birth and every postnatal visit. In many cases clinical manifestations develop late during the postnatal follow up visits. The ‘at risk’ babies in our center are called on every Friday, the day for screening ROP. The timing of follow up varies with different ocular conditions and eye examination must be done at each follow up visit of such high risk neonates or as advised by ophthalmologist. All asphyxiated babies should be evaluated before discharge and subsequently detailed neurodevelopmental and ocular assessments should be made throughout the first 12 to 18 months of life to assess for problems like squint, strabismus, amblyopia, and optic atrophy which are commonly seen during this period.

Treatment

There are several disorders that cause substantial impairment of vision but are relatively asymptomatic in very small neonates and may thus be missed by the parents. Screening for these disorders which are “silent” in manifestation but for which timely intervention is effective should be specifically identified by screening programs. The approach to reduce childhood blindness is tailored to the predominant prevalent disorders. The focus and priorities vary from region to region. The conditions, which can not be prevented but diagnosed early by screening and can be treated in time at the tertiary level, include retinopathy of prematurity, cataract, glaucoma, and strabismus. The action which can be taken at the primary level include: prevention of opthalmianeonatorum by cleansing the eyes, immunization against measles and vaccination against rubella in all children at 9 months of age and pre-pubertal girl 10-12 years of age, are other effective measures.

Retmopathy of Prematurity

Management intervention for ROP can be placed broadly into three categories: prophylactic, interdictory, and corrective. Prophylaxis is designed to prevent any or, at least severe ROP from developing. Interdictory therapies are those that change the natural course of acute ROP before significant visual loss has occurred, with a choice between either cryotherapy or laser photocoagulation. Corrective therapies viz. viterctomy/lensectomy and scleral buckling, are designed to correct anatomic abnormalities, such as retinal detachment, after they occur and restore vision.

Preventive strategies

Infants who develop ROP often have other morbidities of the very preterm infants, as well as complicated hospital course. This makes clinical correlation between ROP and other clinical entities difficult to interpret. Nonetheless, the following strategies have been tried to prevent ROP:

Antenatal steroids

Antenatal steroids reduce the incidence and severity of respiratory distress syndrome and other morbidities such as patent ductus arteriosus, intraventricular hemorrhage and necrotizing enterocolitis hence could affect the incidence of ROP indirectly (15). In our center, the babies given antenatal dexamethasone only 11.1 % progressed to stage 2 and higher grades of ROP as compared to 26.6% in the control group. None of the babies in the steroid prophylaxis group developed threshold ROP or stage 4 requiring surgery. Antenatal dexamethsone was not found as independent protective factor after controlling for the confounding factors.

Oxygen

As per the consensus AAP/ACOG guidelines for perinatal care: Oxygen should be used as a drug, and should be used only if there is a specific indication. Monitoring of oxygenation of all infants less than 36 weeks should be done including blood gases and blood pressures if needing supplemental oxygen. Records of all gases and the ambient oxygen concentration should be maintained. Attempts to keep arterial oxygen between 50-80-mm hg should be made. Recent data has shown that the oxygen saturation between 88-92% decreases ROP significantly without increasing the cerebral palsy incidence.

Vitamin E

AAP states that the evidence for vitamin E supplementation for ROP may be controversial and that prophylactic administration to reach supra normal level is not recommended. Cochran metaanalysis systematic review does not support the routine use of vitamin E supplementation by intravenous route at high doses, or aiming at serum tocopherol levels greater than 3.5 mg/dl (16). Till date there are no preventive strategies of proven efficacy, so emphasis is on screening at risk neonates for early intervention.

Surgical management

It is now universally accepted that the treatment of the entire avasular retina is effective. The surgical intervention should be performed in the nursery or the operating room preferably the former. It should be carried out with minimal disturbance to the baby in the thermo neutral environment since most of the ROP babies are systemically compromised. A pediatrician or an anesthesiologist must be available to monitor the vital signs, watch for possibility of systemic problems like bradycardia, arrhythmia, and respiratory arrest, which may be precipitated during the procedure (17,18).

When to treat - Suggested guidelines

No case of stage 1 or 2 ROP require therapy, as they resolve spontaneously unless they progress to stage 3.

Most important guiding factor for therapy is the extent of extraretinal fibro vascular proliferation (EFP). If the EFP is present in more than 3 categories or 5 cumulative clock hours in zone 1 or 2 than one should treat.

All stage 4 requires treatment either by ablation alone when the detachment is small or in combination n with buckling procedure.

lf ROP is progressing rapidly (change of stages within days instead of weeks), plus disease is present, there is EFP in three contiguous or 5 cumulative clock hours in zone 1 or 2 then we should treat within 24 to 48 hours. Each eye should be assessed on its own merit.

Laser v/s Cryo

The results of the multicentric trial of Cryotherapy forRetinopathy of Prematurity Cooperative group indicated that treatment is associated with a 41% decrease in the occurrence of posterior retinal traction folds or detachment and a 19 % to 24% decrease in the incidence of blindness when evaluated 5 years later (19-21).

Currently, cryotherapy has been replaced for most applications by the use of lasers except in certain specific instances. These include presence of vitreal hemorrhage obscuring the view of the retinal vessels or if there is a significant remnant of the tunica vasculosa lentis obscuring the view through the lens. The primary disadvantages of cryotherapy include increased rates of bradycardia and apnea, large amounts of collateral tissue damage (eyelid, conjunctiva, sclera and choroids) and inability to precisely coagulate just anterior to the ridge, and high rates of exudative retinal detachment. The less serious disadvantages include high transient elevation of intraocular pressure related to indentation with the probe in the small orbit, greater pain requiring higher levels of anesthesia or analgesia, and severally swollen eye lids. Cryotherapy has important advantages, since it can be performed with small pupil, media opacity or retinal detachment and the length of treatment is generally shorter compared to photocoagulation. The major disadvantage of photocoagulation is the increased incidence of cataract and iris damage, and expensive basic unit.

Weather treating with laser or cryotherapy, the parents must be informed that, although the treatment will reduce the possibility of blindness, blindness may still result despite treatment. Too often parents assume that, with treatment blindness definitely will be avoided.

Ocular Sequelae in High Risk Neonate

Premature child is prone to certain ophthalmic conditions whether or not they develop ROP such as refractive errors (17%), strabismus and amblyopia (19%), optic atrophy (2.7%) and thus these babies also need regular follow up. 10% of the general populations develop myopia in childhood and this figure rises dramatically with increasing prematurity and severity of ROP with incidence of myopia being observed in upto 20% in very low birth weight babies in the first two years of life. Follow up of high risk neonate is very important who are screened for ocular problem either at birth or immediate postnatal period, since sequelae may appear at any till 3 years postnatal life.

Follow-up of ROP<sec id="sec023"><title>Follow up in ROP is critical for:

Detection of ROP at pre threshold

Follow up of regressed ROP at an appropriate time so as to be able to avoid amblyopia from high refractive errors.

Be able to detect any sequele of ROP.

The sequelae of ROP depend upon whether there was spontaneous regression, whether ROP regressed after treatment i.e. cryotherapy or laser or whether it progressed with or without treatment.

Spontaneous regression

A significant number of cases regress without reaching threshold disease. Even 50 % of the cases that reach prethreshold may regress without any sequelae. However, various unfavorable structural outcomes such as macular heterotropia disc drag, retinal and traction bands have been observed in some of these eyes. Sub optimal structural outcome such as these has been associated with sub optimal visual outcome.

Guidelines for regressed ROP

At 6 months of age for:

Strabismus

Refraction

Retinal periphery: Breaks/traction

Glaucoma

Cataract

Corneal changes

At 1 year

Same as above

Yearly till adolescence

Child to be informed by parents about his problems and possible complications

Strabismus and amblyopia

Myopia

Glaucoma

Late onset retinal detachment

The first retinoscopic examination should be done at six months of age with regular follow up till 2 to 2½ years of age as the degree of myopia does not significantly increase after 3 years of age weather or not the child has ROP.

Progressive ROP

Untreated threshold disease may progress to retinal detachment. In some cases spontaneous detachment of the posterior vitreous can relieve the traction and prevent the progression.

Sequelae of Regressed ROP

Refractive Errors

The incidence of refractive errors, especially myopia is seen to be greater in premature neonates that had ROP especially those with VLBW and with severe ROP. It was observe to be 10.6% at our center and varies from 8-20% in various studies (21). Some studies have also found a correlation between the use of cryotherapy for threshold disease and the degree of myopia. The more the premature and lower the birth weight, the more the chances of severe ROP, which has a higher incidence of myopia with or without cryotherapy.

Myopia

Cause of and timing of myopia

Although no exact cause of myopia in preterm babies especially with ROP has been determined, it is presumed that the disease somehow interferes with the normal growth of the eyeball causing myopia and astigmatism. Myopia appears or is detected at 6 months of age and thereafter may increase, remain steady or rarely decrease when it is known as the transient myopia of prematurity. When does the myopia stabilize?

The prevalence of high myopia was found to double between 3 months and 1 year examinations on follow up, but changed little between the 1-year and 2-year examinations. The incidence increased from 16% at 12 months to 38 % at 24 months of postnatal age. The refractive error stabilizes around 2 years of age, which is thus a good time to do cycloplegic refraction. Its incidence does not significantly increase after 3 years of age. This suggests that all preterm must have ophthalmic evaluation till at least 2 years of age.

Degree of myopia

The amount of myopia vary from mild, less than 3D to high myopia upto minus 15-20D which is related to the degree of the cicatrization in the eye. High myopia usually associated with severe form of ROP.

Astigmatism, anisometropia and amblyopia

The incidence of these disorders is seen in 17-20% of premature babies and has been seen to correlate with severe myopia in some studies. The presence of refractive errors and cicatricial sequelae all contribute to amblyopia in these cases. Incidence of astigmatism and anisometropia is reported to be 17% and 16 % respectively in ROP follow up cases, which highly correlated with incidence of severe myopia (22). We observed no case of astigmatism and squint in our babies till date.

Visual Acuity in ROP

The visual acuity in children who have ROP depends on the severity of the disease and the residual changes after regression. 50% of the untreated eyes with threshold ROP become blind while eyes with threshold ROP that do not become blind are at risk for significant impairment (24). The visual acuity of children with stage 5 retinopathy with or without surgery is universally poor which confirms the need for prevention of this stage of the disease. It was observed that the eye with ROP during the neonatal period has a good chance of developing visual acuity equivalent to that of an eye that never developed ROP, if ROP regresses leaving a relatively normal looking posterior retina. Visual acuity is assessed by grating and preferential looking methods at 12,18 and 24 months of age.

Strabismus and Motility Defect

Strabismus is detected in approximately 5% of the general population in early childhood with an incidence between 7-31% in preterm babies. The risk factors for strabismus in children less than 32 weeks gestation includes cicatricial ROP, a family history of strabismus, large refractive errors. Over 30% of infants who had threshold ROP in one or both the eyes had strabismus at 1 year follow up examination, whereas fewer than 15% of infants with stage 1 or stage 2 ROP in zone 3 had developed strabismus by the time of the 1 year examination (25,26). This highlights the importance of need of following even stage I; II ROP till 2 years of age.

Ocular Changes in ROP;Ocular Dimensions:

The subsequent development of eyes that have ROP differ from that of mature infant. There is tendency towards increased axial length and increased corneal curvature both contributing to myopia. Although decreased axial length and microcornea have also been reported. Many children develop an increased lens thickness predisposing to angle closure glaucoma.

Cataract and ROP

The association of cataract with ROP although quite uncommon may be on account of the a) stage 5 with total retinal detachment and complicated cataract b) as a result of photocoagulation. It is observed 1 week to three months after laser treatment in eyes having a predominant anterior tunica vasculosa. No other factor i.e. birth weight, gestational age, severity of ROP or number of burns correlate with these opacitie.

Anterior Segment Changes

In severe ROP pupilary rigidity, ectropion uveae and iris neovascularisation can lead to secondary uveitis and glaucoma. Later follow up should watch for corneal changes like band shaped keratopathy and keratoconus.

Retina and Vitreous

Most cases of ROP will regress without leaving much sequelae. At 5 years of age, the posterior segment features that may be seen, include poor vascularization along with pigmentation of the retinal periphery, lattice degeneration and occasionally epiretinal membrane formation. In more severe forms of ROP, macular ectopia, tractional bands, tractional retinoschisis and retinal folds may be seen. Vitreo-retinal interface changes and lattice may be seen in upto 20% of premature infants with ROP. Retinal detachment leading to hole formation may occur at a later date necessitating careful long-term follow up of these cases.

Visual Field Changes

In children treated with cryotherapy or even Xenon arc photocoagulation a peripheral field defect has been observed. The loss upto 10%, observed on long term follow up at around 5 years is a minor loss when compared to the extent of benefit in the form of prevention of blindness.

Follow-up of other ocular morbidities

Neonates with congenital infections need to be evaluated for congenital ocular morbidities viz chorioretinitis, cataract and glaucoma. These ocular manifestations may be present either at birth or develop subsequently

<sec id="sec040"><title>Cataract

The exact causes of cataract at the time of birth or in neonatal period is yet unknown. Maternal malnutrition and infection by viruses as in rubella are very well described associations. Other causes include deficient oxygenation owing to placental hemorrhage, hypocalcaemia, stage V induced ROP and other storage disorders. Galactosemia induced cataract occurs once milk feeds are started. Before planning treatment, a detailed history and careful clinical evaluation including laboratory testing to look for the underlying etiology are mandatory:

Laboratory Evaluation for Bilateral Cataract

Blood tests:

Serum calcium, phosphorus, blood glucose

Red blood cell transferases, and galactokinase levels

Serology of Toxoplasma, Rubella, CMV, Herpes (TORCH)

Urine tests:

Urine assay for reducing substances (Galactosemia)

Amino acids in urine (Lowe syndrome) Once you suspect conditions causing cataract, babies must be referred to ophthalmologists for further assessment.

Treatment is usually not indicated in a developmental or congenital cataract when vision is considerably impaired. The critical period for development of the fixation reflex is between 2 and 4 months of age. Any cataract dense enough to impair vision must be dealt with before this age. The exact timing of surgery, surgical technique, types of optical rehabilitation (aphakia glass, contact lens, or intraocular lens) are issues discussed with parents during follow up.

Glaucoma

Congenital glaucoma is one of the commonest preventable causes of blindness in infancy, with best result achieved by early intervention, thus emphasizing the need of early screening and regular follow of the high risk babies. It presents within the first few months of life with watering from the eyes and photophobia. On examination the eyes, are enlarged and cornea hazy due to edema. Screening can be carried out using hand held slit lamp and measurement of intraocular pressure.

Most cases are bilateral and occur in otherwise normal infants. However glaucoma may complicate other disorders such as congenital rubella syndrome, neurofibromatosis, aniridia, anterior segment cleavage syndrome, Surge Weber syndrome, Lowe syndrome and Rubstein Tyabi syndrome. A form of secondary angle closure glaucoma may also complicate severe ROP, retinal dysplasia and persistent hyperplasic primary vitreous. The management of the disorder is primarily surgical involving goniotomy or trabeculotomy. Medications are not very effective. Affected baby needs repeated examinations under anesthesia to allow measurement of the intraocular pressure and assessment of the ocular disc cupping and growth of the eye. Once control of the intraocular pressure is achieved and corneal clarity restored, management is concerned with treating the associated amblyopia, which is the major cause of visual morbidity in infants with this disorder.

Follow-up of Asphyxiated Babies

These babies need to be followed up for the assessment of visual loss particularly cortical blindness. Visual impairment in early infancy may be due to damage to the higher visual pathways on account of neurological insult such as perinatal hypoxia or in case of preterm infants PVL, but it is also seen in a variety of other disorders such as meningitis, encephalitis and hydrocephalus. These babies have poor visual responses, with absence of normal fixation and following and a normal fundus examination. Investigations reveal normal electrophysiological testing with abnormal visual evoked responses. CT/MRI may or may not show abnormalities. The visual prognosis is best in babies with normal scan. Infants with severe asphyxia may show visual improvement over a prolonged period, so parents should never be given a very pessimistic prognosis at diagnosis.

Conclusion

The high risk neonates are at considerable risk for ocular abnormalities, as well as for deficits in visual function during the immediate perinatal period extending up to childhood. It is therefore important to screen all such neonates with or without ROP and to keep them under follow up till at least 3 years of age. The treatment should be a team work involving dedicated nurse, pediatrician and ophthalmologists. The parents of such babies should be informed of the nature and the possible consequences of the disorder through out the infant's hospital stay beginning at the time of the first diagnosis and continuingon an ongoing basis with updates on its progression during hospitalization. The ocular condition associated with highrisk neonates must 12 be treated early to prevent the development of irreversible deficits in visual function.

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