Oculocardiac Reflex During ROP Exams

Abstract

Purpose: Reducing physiologic stress including bradycardia during staging eye exams for retinopathy of prematurity (ROP) is desirable. We observed heart rate change during routine retinopathy of prematurity eye examinations and compared the response with our ongoing study of oculocardiac reflex (OCR) elicited by uniform EOM tension during strabismus surgery.

Patients and methods: Electrocardiograph was prospectively monitored during ROP exams featuring indirect ophthalmoscopy with Alfonso lid speculum and see-through scleral depressor without topical anesthesia. Clinical data were retrieved from ROP-Check software. OCR was defined as maximally changed heart rate (HR) as a percent of baseline. Strabismus surgery patients under general anesthesia served as controls.

Results: From 10/2017 to 9/2020, 281 infants had ROP exams, and the median OCR was 55.9% of baseline HR (IQR 41.4% to 72.6%), the kurtosis 0.93 and skewness 1.01 representing a drop from HR 169 ± 16 bpm to 102 ± 39 bpm. In comparison, 1493 adult and pediatric strabismus surgery patients had less OCR median bradycardia 87.8% (IQR 72-98%), kurtosis 1.60 and skewness -1.18. ROP %OCR correlated with birth gestational age (%OCR = 2.5 (GA) - 11, r(279)=0.33, p<0.01) and with birthweight (%OCR = 0.02 (BW) + 38, r(279) =0.35, p<0.01). The duration of bradycardia induced by ROP exam averaged 92 ± 34 seconds (range 34-240 seconds).

Conclusion: Bradycardia is common during eye exams in the smallest premature infants with greater degree, more rapid onset and longer duration than OCR during strabismus surgery.

Keywords: bradycardia; retinopathy of prematurity; strabismus.

Conflict of interest statement

Dr. Robert Arnold is President and board member of Glacier Medical Software that markets cloud-based NICU monitoring software ROP Check. He is also President and board member of PDI Check that markets autostereoscopic vision screening games for Nintendo 3DS. He coordinates the Alaska Blind Child Discovery that has received discounted vision screen technology from several vendors. He is the inventor of the Storz Arnold See-Through Scleral Depressor (sp7-38098) but receives no royalties and was an investigator and protocol developer for Pediatric Eye Disease Investigator Group, during the conduct of the study; and non-paid advisory board for GoCheck Kids, Adaptica and PlusoptiX, outside the submitted work; in addition, Dr Robert W Arnold has a patent pending for PDI Check to Robert Arnold and Alex Damarjian. The authors report no other potential conflicts of interest for this work.

© 2020 Schumacher et al.

Figures

Figure 1

Distribution of oculocardiac reflex (OCR) elicited by strabismus surgery (top) and ROP examination (bottom). OCR defined as maximally changed heart rate as a percent of stable baseline heart rate. The stimulus for strabismus surgery was 10-second, 200 gram, square wave tension on gently isolated extraocular rectus muscle without anticholinergic medication. Stimulus during retinopathy of prematurity exams was Alfonso lid speculum placement and scleral depressed indirect ophthalmoscopy of both eyes without topical anesthetic. Additional statistics include mean, standard deviation and standard error of the mean and median with interquartile range, and 95th percentiles.

Figure 2

Influence of gestational age on oculocardiac reflex during ROP exams: Patients who had at least six serials exams. Blue diamonds represent the stable pre-exam heart rate, orange triangles represent the maximally changed heart rate during lid speculum, scleral-depressed indirect ophthalmoscopy exam and green circles represent the OCR as a percent of stable pre-exam heart rate.

Figure 3

Influence of birthweight on oculocardiac reflex during ROP exams. The oculocardiac reflex defined as maximally changed heart rate during lid speculum, scleral depressed ophthalmoscopy as a percent of stable, pre-exam heart rate correlates with birthweight.