Treatment Requiring ROP

 

Treatment Requiring ROP

 

           In the multicenter cryotherapy study for treatment

of acute ROP (ICROP), threshold, i.e.,

treatment requiring ROP, was defined as stage 3

plus disease in zone II or zone I with at least 5

continuous clock hours or at least 8 cumulative

clock hours of stage 3 disease, i.e., extraretinal

proliferations. Using this

criterion, a favorable functional outcome at

1 year was achieved in 73% of zone II disease

eyes, and in 12% of zone I disease eyes, compared

to 46% of zone II disease eyes that were

not treated, and 6% zone I disease eyes that

were not treated. Despite this considerable

success compared to the natural history, the

number of unfavorable outcomes was still high.

 

               This led, in the following years, to a redefinition

of treatment-requiring disease. The risk model

RM-ROP published by Hardy in 1997 consists

of five mathematical equations that provide

a relationship between risk factors observed

concerning the infant and the infant’s

retina as they correlate with structural outcome.

The program is based on data from 4,099

infants who weighed less than 1,251 g at birth

who composed the natural history cohort of the

Multicenter Trial for Cryotherapy for Retinopathy

of Prematurity. This risk model has

recently been further developed and replaced

by the risk model RM-ROP2 [25], which evaluates

the risk of prethreshold ROP to progress to

threshold ROP and to an unfavorable outcome

(Table 5.3). For eyes with a risk of 0.15–1.0, 36%

had an unfavorable structural outcome at

3months compared to 5% for eyes with a risk of

less than 0.15. There is now an internet address

that makes it possible to directly calculate the risk

             The same calculation was

used in the Early Treatment of ROP Study

Group ETROP used this calculation. ETROP defines

treatment-requiring ROP as type 1 ROP,

whereas they recommend a watch and wait policy

in type 2 ROP. The definition of the two

types is given in Table 5.4. For eyes designated

high risk, 63% progressed to the conventional

threshold ROP requiring treatment, and for eyes

designated low risk, 14% progressed to threshold.

ETROP claims that the new definition of

treatment-requiring ROP has the potential to

salvage more eyes from an unfavorable outcome,

and to generally improve the functional

outcome. With the conventional threshold,

44.4% of eyes had a visual acuity of 20/200 or

less at 10-year follow-up, and of the 55.6% with

a visual acuity of better than 20/200,only 45.4%

had a visual acuity of 20/40 or better, i.e., only

about 25% of all infants that were treated

reached a visual acuity of at least 20/40 [15].

Whether with the new definition of treatmentrequiring

ROP the functional outcome will be

indeed improved remains to be demonstrated.

This is important as on the other hand a significant

number, i.e., 37% of infants will be treated

unnecessarily.

 

 

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