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Approaches to ROP screening

Advantages and disadvantages of the different approaches to ROP screening.
Screening for retinopathy of prematurity is different from screening for chronic diseases such as diabetic retinopathy, which happens at defined intervals. It’s also different from screening for metabolic disorders where a one-off test is required. For ROP the population at risk is defined by birth weight, gestational age and the neonatal care received. There is a very narrow time interval during which severe ROP develops, from three to 18 weeks after birth depending on gestational age. Additionally, there is no simple pass/fail test. Ideally, each preterm baby’s first ROP screening event is scheduled at a specific period after birth based on the baby’s postmenstrual age. Evidence has highlighted that the more preterm an infant is, the longer the time it takes to develop ROP.
This knowledge has been used to develop a screening schedule. For babies born at 27 weeks gestational age or more, the first ROP screening is recommended at four weeks after birth. Babies born with a gestational age of less than 27 weeks should be screened when they are at 31 weeks postmenstrual age. This means that a baby of 26 weeks gestational age will need to be screened 5 weeks after birth, whereas a baby born at 22 weeks gestational age should be screened 9 weeks after birth. These guidelines may change as new evidence emerges.
Some countries use the same time for the first examination regardless of the birth weight, particularly in settings where a high proportion of preterm infants have foetal growth restriction. In these settings the first screening is at 4 weeks, or 30 days
There are two main screening methods for ROP. Each involves a different cadre and requires different training. Binocular indirect ophthalmoscopy, known as BIO, Camera-based screening using a wide field imaging system
In BIO screening, an ophthalmologist examines the eye using an indirect ophthalmoscope … and a condensing lens of 20/28D with some scleral indentation to enable the peripheral retinal blood vessels to be seen. For BIO screening, the ophthalmologist needs to visit the unit on a set day and time each week, or even twice a week. This means that babies who are still inpatients can be screened as well as those who return for screening after discharge. The advantages of the BIO approach are” that it is regarded as the gold standard for ROP screening, it uses low cost equipment, and an immediate diagnosis and management decision can be made and documented.
BIO does have limitations as an approach: Ophthalmoscopic examination is more time consuming and can be stressful for the baby. To master ROP ophthalmoscopy an ophthalmologist needs to undergo proper training and gain enough experience and skills. Employing ophthalmologists as ROP screening experts can be expensive. Clinical findings are only written down, based on the observations of the screener. BIO is suitable for small programmes which screen a few babies every week. In camera-based screening, a trained technician or nurse captures retinal images using a paediatric digital wide field camera. These are transferred online to an expert ophthalmologist or a trained non-physician grader using special software.
The expert, who may be at a distance, then does the grading and the management decision and a report is sent back to the screening facility. This can happen in ‘real time’. although there can be delays.
There are many advantages to camera-based screening: A technician or nurse can be trained in a few weeks. Having a dedicated imaging technician allows for more flexibility in scheduling screening. The procedure takes only two to three minutes and is less stressful for babies than BIO screening. Typically, the camera is portable and can be used in multiple neonatal facilities. Camera-based screening is suitable for high volume ROP programmes where a larger number of babies need timely screening across a large number of units.
Digital photo documentation has an important advantage from a medicolegal point of view. Additionally, the images can serve as an excellent counselling and teaching tool. A high rate of compliance with follow up can be achieved if images are shown during parental counselling
The main limitations of camera-based screening are: The high cost of the equipment. The camera operators require training in the capture, storage and uploading of images to the telemedicine server, and to understand the infant eye and recognise the signs of ROP - zones, stages and plus disease. The ophthalmologists need training for grading and decision making at a distance. The images can be difficult to grade if not clear, and timely clinical input is essential but it can take a few hours to get a report from a remote grader
Several studies have shown that camera-based ROP screening can attain a sensitivity of 100% which means that no cases of sight-threatening ROP were missed by the grader. This is important because it shows that camera-based screening is a reliable testing method.
Screening for ROP can be either ophthalmology led or neonatology led. In an ophthalmology led ROP screening programme, the screening team is an external resource to the NICU and visits on a weekly basis. This can lead to challenges such as missing babies who were too sick to be screened on screening day or could not travel back for follow up screening after being discharged from the NICU. A neonatology led screening programme is where an internal NICU team is in charge. A trained nurse lists all the at-risk babies and performs camera-based screening. A trained image grader interprets the images and an ophthalmologist makes the required management decision. Screening is scheduled around the baby which reduces the number who miss out on ROP screening.
In some settings, for example India, neonatology led ROP screening is gaining attention because of the flexibility in scheduling screening and the improved cost effectiveness from involving the ophthalmologist only when severe ROP is detected However, to be implemented effectively, this approach requires a good understanding of professional boundaries. In each NICU, staff and consultants must carefully define who is responsible for the examination and follow-up of infants at risk for ROP. The neonatology and ophthalmology services must also consult with each other and agree specific criteria for the timing of the first ROP examination. Clear roles and responsibilities are required to ensure that all eligible babies are listed on the correct day for screening. A diary or electronic system can be used.
The list is used to check those who are not screened and why, and corrective action needs to be taken.
At each ROP screening examination, one of three key management decisions is made based on the findings
of the most advanced ROP in the worst affected eye: 1. Urgent treatment (within 24 to 48 hrs) is required in one eye or both eyes. This must be clearly documented. 2. Screen again in three to 14 days. 3. No further screening is required as the retinal vessels are are mature or ROP is regressing. Documentation includes the date of screening, findings in each eye (stage, zone and so on), management decision, including date of next screening if relevant, and the signature of the screener. The screener may also want to keep separate paper or electronic records. Even if babies are to be transferred or discharged, the management decision must be documented and clearly communicated to the neonatal team and parents or carers.
There is a critical time-period during which ROP treatment can be successful and timely follow-up examination is essential.
In summary: Screening for ROP is essential for early detection and prevention of blindness. The timing of the ROP screening is based on available evidence and guided by postmenstrual age. Systems need to be in place to ensure that all eligible babies have the first and all subsequent screening needed ROP screening can be undertaken using BIO or camera-based screening, depending on available resources. Camera-based screening has several advantages, in particular for neonatology led ROP screening, but training is essential. Successful detection of ROP requires trained personnel, accurate interpretation and immediate (cot side) management decisions. Decisions must include one of the three actions- to treat, to rescreen or no further rescreening. Services must be in place for timely treatment, if indicated

In this video we consider the advantages and disadvantages of the different approaches to ROP screening. As you watch, consider which approach is most suitable in your setting to ensure the best outcome for early detection of ROP.

The following excerpt is from Screening Examination of Premature Infants for Retinopathy of Prematurity published in the journal Pediatrics in December 2018.

‘Because of the usually predictable and sequential nature of ROP progression and the proven benefits of timely treatment in reducing the risk of visual loss, efficacious care now requires that infants who are at risk receive carefully timed retinal examinations to identify treatment-requiring ROP in time for that treatment to be effective. These examinations should be performed by an ophthalmologist who is experienced in the examination of preterm infants for ROP using a binocular indirect ophthalmoscope. The examinations should be scheduled according to the preterm infant’s gestational age at birth and subsequent disease presence and severity, with all pediatricians or other primary care providers who care for the at-risk preterm infant aware of this schedule. When implemented properly, telemedicine systems using wide-angle retinal images and clinical data may be used for preliminary ROP screening or as an adjunct to binocular indirect ophthalmoscopy for ROP screening.’

After watching the video, look at the PDF in the Downloads section below comparing the two screening approaches.

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Retinopathy of Prematurity: Practical Approaches to Prevent Blindness

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