Objective To observe the incidence of retinopathy of prematurity (ROP) at different altitudes in Yunnan Province. MethodsA retrospective case-control study. From July 1, 2010 to June 30, 2019, 1 352 premature infants (Kunming group) and 579 premature (Dehong group) infants who received ROP screening in the Neonatology Department of Kunming Maternal and Child Health Hospital and the Neonatology Department of Dehong Dai and Jingpo Autonomous Prefecture People's Hospital were included in the study. A wide field digital retinal imaging system combined with binocular indirect ophthalmoscope and scleral oppressor was used for fundus examination. Inspection results were recorded according to the international ROP classification. The incidence of ROP in recent 10 years was retrospectively analyzed. Independent sample t test was used for comparison between groups. ResultsAmong the 1 352 preterm infants in Kunming group, 716 were males and 636 were females. The birth weight was (1 765.75±357.64) g; gestational age of birth were (32.51±2.07) weeks. The altitude of the residence was (1 920±30) m. Among 579 premature infants in Dehong group, 302 were males and 277 were females. The birth weight was (1 762.54±401.73) g; gestational age of birth were (32.10±2.36) weeks. The altitude of the residence was (920±80) m. There was no significant difference in sex composition ratio (χ2=0.10, P=0.75) and birth weight (t=0.17, P=0.87) between the two groups (P≥0.05). Gestational age and elevation of residence were compared, and the difference was statistically significant (t=3.82, 35.15; P＜0.01). ROP was detected in 72 cases 144 eyes (5.32%, 72/1 352) in Kunming group and 55 cases 110 eyes (9.5%, 55/579) in Dehong group. Both cases were binocular. There was significant difference in the detection rate of ROP between the two groups (χ2=11.49, P＜0.01). ROP stages 1 to 3 in Kunming and Dehong groups were 128 (88.89%, 128/144), 6 (4.17%, 6/144), 6 (4.17%, 6/144) eyes and 18 (16.36%, 18/110), 66 (60.00%, 66/110), 22 (20.00%, 22/110) eyes. The acute ROP (A-ROP) was 4 (2.78, 4/144) and 4 (3.63%, 4/110) eyes in Kunming and Dehong groups, respectively. There were significant differences in the detection rates of ROP in stages 1 to 3 between the two groups (χ2=11.26, 66.48, 15.86, 0.76; P＜0.05). There was no significant difference in the detection rate of A-ROP (χ2=0.76, P＞0.05). ConclusionThe detection rate of ROP in high altitude area of Yunnan Province is significantly lower than that in low altitude area.