Purpose
To evaluate anterior segment complication rates in eyes treated for prethreshold versus threshold retinopathy of prematurity (ROP) and look for potential risk factors.
Design
Retrospective, observational case series study.
Methods
All patients treated with diode laser for ROP between 1995 and 2007 were identified. A total of 259 eyes of 184 patients were studied, 120 eyes in the pretheshold group and 139 eyes in the threshold group. We compare baseline characteristics, treatment parameters, ocular complications, and structural outcomes after treatment. The main outcome measured was anterior segment complication rates in eyes treated for prethreshold versus threshold ROP and we looked for potential risk factors.
Results
Thirteen of 120 eyes treated at prethreshold had anterior segment complications versus 0 of 139 treated at threshold ( P < .01). All eyes developed post-laser hyphema, 3 with elevated intraocular pressure. Three eyes developed cataract (2 requiring cataract extraction); 1 required treatment for band keratopathy. The mean postmenstrual age at treatment was significantly different between the prethreshold and threshold groups (36.6 vs 37.9 weeks, P = .03); eyes with anterior segment complications were treated at mean postmenstrual age of 35.7 weeks. No difference was found based on gestationtal age at birth, birth weight, zone, stage, or number of laser spots for eyes with anterior segment complications. Most anterior segment complications (77%) resolved without long-term sequelae.
Conclusions
Younger postmenstrual age at laser treatment may be related to an increased risk of anterior segment complications, which should be recognized and managed appropriately.
Retinopathy of prematurity (ROP) remains a significant threat to the vision of premature infants, particularly those born at the earliest postmenstrual ages and with very low birth weight. Preventive therapies continue to be sought, and peripheral retinal ablative treatment with laser (or cryotherapy) is standard for more severe cases. Criteria for treatment have changed over the years, and laser treatment is now routinely performed for many eyes with prethreshold ROP.
Ocular complications of treatment have been previously described after ablative therapy for threshold ROP, and significant anterior segment complications include hyphema, glaucoma, cataract, band keratopathy, and anterior segment ischemia. In the Early Treatment for Retinopathy of Prematurity randomized trial, reduced rates of unfavorable visual and structural outcomes were found for eyes treated at high-risk prethreshold ROP compared to those treated at conventional threshold ROP, without an increase in the rate of intraoperative ocular complications. Systemic complications, including apnea, bradycardia, and need for reintubation, were seen more frequently with earlier treatment. In our neonatal intensive care units, an increased rate of hyphema was observed among eyes treated early. The purpose of this paper is to describe anterior segment complications seen among these patients and, by comparing anterior segment complication rates in eyes treated for prethreshold versus threshold ROP, to look for potential risk factors.
Methods
The ROP database and laser logs were reviewed to identify all infants who were treated for ROP in the years 1995 to 2007. These dates were chosen to span a period that encompassed both Cryotherapy for Retinopathy of Prematurity Cooperative Group and Early Treatment for Retinopathy of Prematurity recommendations for treatment consideration. The laser log, which is completed at the time of the procedure, includes a section for the treating ophthalmologist to record complications that occur during the procedure. Similarly, the database includes a section to record examination results, including complications at follow-up examinations. Baseline characteristics of each infant (postmenstrual age at birth, birth weight, gender, race), characteristics of each eye receiving treatment (postmenstrual age at treatment, zone and stage of ROP at treatment), parameters of treatment (number of laser spots applied, wavelength, power and duration of laser application, type of sedation or anesthesia), and complications during and/or after treatment were collected for analysis. Eyes were excluded if they were treated primarily with cryotherapy, if they were first treated for disease beyond threshold, or if the patient was transferred in solely for the laser treatment, in which case there was insufficient follow-up. Approval from the Institutional Review Board was obtained for this study.
All ROP examinations and treatments were performed by ophthalmologists experienced in ROP screening and treatment. All eyes received primary treatment with the indirect infrared diode (810-nm) laser. Eyes were sorted into those treated at threshold ROP, as defined by the International Classification of ROP and the Cryotherapy for Retinopathy of Prematurity Cooperative Group, and compared to eyes that were treated at any level of prethreshold ROP. Some infants in these neonatal intensive care units were participants in the Early Treatment for Retinopathy of Prematurity randomized trial. Therefore, the prethreshold group includes any eye treated at “near threshold” when the fellow eye was treated at threshold prior to Early Treatment for Retinopathy of Prematurity randomized trial, “high-risk” prethreshold eyes for infants who were participants in the Early Treatment for Retinopathy of Prematurity randomized trial, and eyes with “Type 1” prethreshold ROP after the Early Treatment for Retinopathy of Prematurity randomized trial. All eyes treated at “near threshold” retrospectively met type 1 prethreshold treatment criteria, with stage 3 ROP in zone 1 or 2, with plus disease. Complication rates were compared between the threshold- and prethreshold-treated groups.
A χ 2 analysis was used to compare the presence of anterior segment complications between prethreshold and threshold groups, and Yates correction was applied in order to provide a more conservative result given the small sample of the studied factor anterior segment complications. For analysis of baseline characteristics as well as comparison of the eyes at the moment of treatment, we also separated the prethreshold group into 2 subgroups of eyes, those with anterior segment complications and those without anterior segment complications. For categorical variables χ 2 was used, and for continuous variables Student t test for 2 independent variables was used. For all analyses, P < .05 was considered statistically significant.
Results
Two hundred fifty-nine eyes of 184 infants who had primary laser treatment for ROP were included for analysis. An additional 17 infants were excluded because they were treated primarily with cryotherapy, were beyond threshold at first treatment, or lacked post-laser follow-up data. One hundred twenty eyes were treated at any prethreshold ROP; 139 eyes were treated at threshold ROP. There were no differences between the threshold ROP and prethreshold ROP eye groups regarding baseline characteristics of the infants ( Table 1 ). Though the mean birth weight is less in the prethreshold anterior segment complication group compared to the prethreshold without anterior segment complication or threshold groups, this was not a statistically significant difference. All eyes received diode laser as the first treatment, and only first treatment applications were used for analysis.
| Group | Mean PMA (Weeks) | Mean BW (g) |
|---|---|---|
| Threshold (n=139) | 25.1 | 715.0 |
| All prethreshold (n=120) | 24.8 | 715.3 |
| Prethreshold no ASC (n=107) | 24.8 | 723.1 |
| Prethreshold ASC (n=13) | 24.5 | 642.6 |
Thirteen of 120 (10.8%) eyes treated at prethreshold were found to have an anterior segment complication after laser treatment compared to none of the eyes treated at threshold ROP ( P < .01). All 13 eyes had hyphema, in isolation or in combination with elevated intraocular pressure (n = 3), cataract (n = 3), or band keratopathy (n = 2). The hyphemas were discovered within the first week after laser treatment during routine follow-up examination. There were 2 eyes in the threshold ROP group with hyphema, but these were found prior to treatment and thus were attributed to ROP. No significant posterior segment complications were recorded other than those associated directly with ROP, including retinal detachments.
Table 2 shows mean characteristics at the time of treatment. The only statistically significant difference between the groups was the mean postmenstrual age at treatment between prethreshold and threshold groups (36.6 vs 37.9 weeks, P = .03). Eyes with anterior segment complications were treated even earlier, at mean postmenstrual age of 35.7 weeks, but this was not statistically significant owing to the small number of eyes in the anterior segment complications group for comparison. More eyes in the prethreshold group were treated in zone 1, but there were not more zone 1 eyes in the group that developed an anterior segment complication compared to the group that did not develop an anterior segment complication. By definition, all eyes treated in the threshold group had stage 3 ROP, but there was a similar rate of stage 3 ROP in the prethreshold groups. There were no significant differences in number of spots used for treatment.
| Mean PMA (Weeks) | Mean # Laser Spots | % Eyes Zone 1 | % Eyes Stage 3 | |
|---|---|---|---|---|
| Threshold | 37.9 | 1146 | 2.2 | 100 a |
| All prethreshold | 36.6 | 1152 | 15 | 80 |
| Prethreshold no ASC | 36.7 | 1159 | 16 | 80 |
| Prethreshold ASC | 35.7 | 1090 | 7.7 | 76.9 |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
