Therapy for retinopathy of prematurity

Abstract

similar effects. In several reports of larger case series of laser therapy, comparison was against historical controls who had received cryotherapy. Such comparisons should be interpreted with caution because neonatal intensivecare techniques have changed. All the comparisons have shown that cryotherapy and laser therapy have a similar effect on the structure of the retina, except in the small subgroup of infants with posteriorly situated ROP. The structure was restored to normal after cryotherapy in only 20–30% of this group, compared with 50–80% of patients receiving diode-laser therapy. The two forms of therapy also have similar effects on visual acuity. In a small randomised comparison of cryotherapy and laser therapy, White and Repka found better visual acuity in laser-treated eyes, but follow-up was incomplete. Pearce and colleagues reported better visual acuity after laser therapy in a historical comparison with cryotherapy. However, some infants in the laser group were treated at a “prethreshold” level of severity and may have had less severe disease. Although cases of pigmentary maculopathy after cryotherapy have been reported, concern that cryotherapy directly damages visual acuity has not been substantiated. O’Keefe et al found no difference in visual acuity between laser-treated eyes and cryotherapy-treated eyes when the eyes with structural abnormalities of the macula or optic radiations, or amblyopia, were excluded. The most consistent and striking difference in effect between cryotherapy and laser therapy has been the incidence of myopia. Untreated ROP is associated with myopia. A high incidence of myopia following cryotherapy was found in the Cryo-ROP study. The incidence and degree of myopia in eyes treated with diode laser is very low. Perhaps cryotherapy damage to the sclera alters ocular growth. When asymmetrical, myopia leads to amblyopia. O’Keefe and colleagues found two cases of anisometropic amblyopia in their cryotherapy group, and no cases in the laser-treated group. Strabismic amblyopia also occurs in children with treated ROP, and insufficient attention has been given to role of amblyopia in most treatmentoutcome studies. In summary, diode-laser therapy seems to offer some advantages over cryotherapy. Laser therapy probably produces better structural outcomes in eyes with posterior ROP. Myopia is less common and of lesser degree after laser therapy. However, treatment failures and subsequent blindness continue to occur after either form of treatment. Protocols for screening examinations must be refined, as must the criteria used to determine the point at which treatment is given. Surveillance of ROP treatment outcomes such as that being done by the British Ophthalmic Surveillance Unit may identify factors associated with treatment failure.