Progression of type 2 to type 1 retinopathy of prematurity in the Early Treatment for Retinopathy of Prematurity Study.
OBJECTIVE
To examine the frequency and timing of progression from type 2 to type 1 retinopathy of prematurity (ROP) in the Early Treatment for Retinopathy of Prematurity Study.


METHODS
Infants with prethreshold ROP that was no worse than low risk in 1 or both eyes, based on the RM-ROP2 model, were examined every 2 to 4 days for at least 2 weeks. Using the Early Treatment for Retinopathy of Prematurity Study-defined classification of eyes as having type 1 or type 2 prethreshold ROP, we analyzed the time to conversion from type 2 to type 1. Data were analyzed for 1 randomly selected eye for each child.


RESULTS
Of 294 eyes at first diagnosis of type 2 ROP, 65 (22.1%) progressed to type 1 (mean [SD] interval, 9.0 [6.6] days; median, 7.0 days). Of 217 eyes with type 2 ROP that had an examination in less than 7 days, 25 (11.5%) were diagnosed with type 1 ROP in less than 7 days. Of 200 eyes that continued to have type 2 disease at the first follow-up examination and underwent a subsequent examination, 24 (15.7% of the 153 eyes that had an examination in <7 days) developed type 1 ROP in less than 7 days. The risk of progression from type 2 to type 1 in less than 7 days was greatest between 33 and 36 weeks' postmenstrual age, regardless of zone of retinopathy.


CONCLUSIONS
Type 1 ROP can be identified with weekly examinations in most eyes with initial diagnosis of type 2 ROP; a small subset progresses to type 1 in less than 7 days.


BACKGROUND
clinicaltrials.gov Identifier: NCT00027222.
Christiansen
Stephen P
SP
Department of Ophthalmology, University of Minnesota, Minneapolis, USA. spchris@bu.edu
Dobson
Velma
V
Quinn
Graham E
GE
Good
William V
WV
Tung
Betty
B
Hardy
Robert J
RJ
Baker
John D
JD
Hoffman
Robert O
RO
Reynolds
James D
JD
Rychwalski
Paul J
PJ
Shapiro
Michael J
MJ
D018450:Disease Progression; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D012178:Retinopathy of Prematurity / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology*; D013997:Time Factors; D015351:Vision Screening / Q000379:methods