What is the grading and treatment approach for retinopathy of prematurity (ROP) in a premature infant with low birth weight?

Retinopathy of Prematurity Grading and Treatment

ROP is classified by location (zone I-III), stage (1-5), extent (clock hours), and presence of plus disease, with treatment indicated for type 1 ROP using laser photocoagulation as the gold standard, particularly for zone II disease. 1, 2

ROP Classification System

Anatomic Zones

• Zone I: Central retina around the optic disc—highest risk area for severe disease 1
• Zone II: Extends from zone I to the nasal ora serrata—most common location for treatable ROP 2
• Zone III: Residual temporal crescent—lowest risk, rarely requires treatment 1, 2

Disease Stages

• Stage 1: Demarcation line separating vascular from avascular retina 3
• Stage 2: Ridge formation with height and width 3
• Stage 3: Extraretinal fibrovascular proliferation on the ridge 3
• Stage 4: Partial retinal detachment 4
• Stage 5: Total retinal detachment 4

Plus Disease

Plus disease indicates vascular dilation and tortuosity in the posterior pole, signifying increased severity and need for closer monitoring or treatment 3, 4

Treatment Thresholds

Type 1 ROP (Treatment Required)

Immediate treatment is indicated for type 1 ROP to prevent blindness: 2, 5

• Zone I: Any stage with plus disease
• Zone I: Stage 3 without plus disease
• Zone II: Stage 2 or 3 with plus disease

Type 2 ROP (Close Observation)

These infants require ophthalmology visits every 1-2 weeks but do not require immediate treatment: 1, 2

• Zone I: Stage 1 or 2 without plus disease
• Zone II: Stage 3 without plus disease

Treatment Modalities

Primary Treatment: Laser Photocoagulation

Peripheral laser ablation remains the gold standard treatment, particularly for zone II disease, as it has proven effective in reducing blindness from ROP. 6, 2, 7

Alternative/Adjunctive: Anti-VEGF Therapy

Anti-VEGF agents (bevacizumab, ranibizumab) may be used as monotherapy or combined with laser, especially for zone I disease 7. However, laser photocoagulation should be prioritized as the established standard 7.

Surgical Intervention

Surgery is reserved for advanced stages (stage 4-5) with retinal detachment 3, 7

Critical Management Considerations

Oxygen Management

• Target oxygen saturation of 96-99% does not increase ROP progression risk in infants with pre-threshold disease 6, 1
• Once past the age of oxygen-induced retinopathy risk, target saturation of 95% or higher is recommended 2
• Avoid sustained hyperoxemia in infants with peripheral avascular retina 6

Follow-up Protocol

For infants with zone I or II disease: 1, 2

• Schedule ophthalmology visits every 1-2 weeks depending on severity
• Missing follow-up appointments can result in preventable blindness 6, 2

Screening can be discontinued when: 1, 2

• ROP is regressing with vessels passed into zone III on at least two sequential examinations
• Complete retinal vascularization is achieved
• Stage 0 zone III disease is present

Special Populations

Infants with chronic lung disease require heightened vigilance: 1, 2

• Screen even if between 29-37 weeks gestation
• Careful coordination of follow-up appointments is crucial when discharged home
• Parents cannot usually provide close oxygen control without extensive support 6

Screening Guidelines

Who to Screen

Screen all infants with: 1

• Less than 32 weeks gestational age at birth (conservative approach)
• Birth weight less than 1251 g (98.1% of type 1 or 2 ROP occurs in this group) 5
• 29-37 weeks gestation with unstable course requiring supplemental oxygen 1

Timing of First Examination

Perform initial screening at the later of: 1

• 31-33 weeks postmenstrual age, OR
• 4 weeks chronological age

Examination Requirements

The examination must be conducted by an ophthalmologist experienced in evaluating ROP in premature infants using indirect ophthalmoscopy with adequate dilation. 1 Telemedicine approaches with wide-field digital retinal imaging are acceptable when coupled with timely referral pathways 1.

Common Pitfalls to Avoid

• Never discharge infants with zone I or II disease without confirmed follow-up appointments—this is the greatest risk for preventable blindness 6, 1
• Do not assume medically stable infants between 29-37 weeks are safe from ROP if they have chronic lung disease 1
• Avoid restricting oxygen excessively in infants with pre-threshold ROP, as saturations of 96-99% are safe 6
• Only about 49.4% of eyes are vascularized into zone III by 37 weeks postmenstrual age, so do not discontinue screening prematurely 5