Eyeworld

EW CATARACT 38 December 2016 by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer Brazilian surgeons apply a novel formula to calculate biometry P ediatric cataract patients can be difficult to manage, requiring special consider- ations with regard to the accuracy of IOL power. When choosing an IOL with a fixed strength for implantation into an eye that is still growing, the surgeon needs to account for the long term, as well. Biometry and IOL calcula- tions are complicated in children due to short eyes and steeply curved, often irregular corneas, but also because of the need to anticipate the changes in axial length and keratometry that come with a child's future eye growth. Formulas for the calculation of IOL power are widely used, however, they need to reflect ocular growth, according to a Brazilian research team who reported their observa- tions using a novel IOL power calcu- lation formula that they specifically developed for use in pediatric cases, along with their first case series, at the 2016 European Society of Cata- ract & Refractive Surgeons (ESCRS) annual meeting. Pediatric IOL power estimation In his presentation, Virgilio Figueiredo Silva, MD, head of the pediatric cataract surgery service, Sadalla Amin Ghanem Eye Hospital, Joinville, Brazil, demonstrated how the use of a simple formula could reliably predict dioptric power in children with pediatric cataract. Lacking a manual keratometer, the formula was of particular service in calculating IOL power in his very young patients, at once solving the hospital's dilemma of not being able to afford a manual keratometer and providing excellent refractive outcomes. "Biometric calculation of a growing eye is challenging, and IOLs implanted for emmetropia will produce additional refractive error due to myopic shift and axial growth. Surgeons should never aim for emmetropia in pediatric patients. Usually, cataract surgeons use age tables in normal eyes to select IOL power. These characteristics may differ, however, in the presence of cataract," Dr. Silva said. Dr. Silva and his team, headed by Antonio Carlos Lotelli Rodriguez, MD, PhD, conducted two studies at Botucatu Medical School, São Paulo State University, Brazil. The first was a retrospective observational study that investigated axial length (AL) and keratometry (K). The study demonstrated significant changes in these values with increasing patient age, especially in the first 6 months of life, and also established a linear functional relationship between AL and K using an age logarithm. 1 The study evaluated AL and K in Brazilian children with congen- ital/developmental cataract using a manual keratometer to measure biometry and assessed the differ- ences and evolution of AL and K according to age. The analysis included 44 eyes with cataract, of which 15 eyes had unilateral cata- ract and 29 eyes were the left eyes of children with bilateral cataract. The mean age was 27.3 months. The mean AL was 20.63±2.11 mm (P=0.990) and ranged from 17.27 mm to 24.96 mm, and the mean K was 44.94±2.44 D (P=0.629), ranging from 40.00 D to 53.00 D. Dr. Silva and his team found that the relationship between AL and K was statistically significant, with the mean AL value increasing with age and the mean K value decreasing with age (P<0.001). Separating these observations into groups for children under and over 12 months of age revealed homoge- neity in the response between the two age groups in terms of relative variability. The study revealed no significant differences between eyes with unilateral and bilateral cataract or between unilateral cataract eyes and their corresponding healthy eyes (P>0.05). "AL and K change markedly with increase in age. The highest rates of ocular axial growth and cor- neal flattening are observed in the first 6 months of life. We published our results on the development of this formula in January of this year," he said. Implementing the formula Next, with these observations in place, Dr. Silva went on to imple- ment the formula—K-52.91 x 0.035 AL (mm)—to calculate his patients' IOL dioptric power, within the context of a second study that was presented as a case series of 12 eyes with congenital cataract. The mean patient age at surgery was 34.5 months, ranging between 1.5 and 8 years old. Ten eyes had Simple solutions that work in pediatric cataract surgery Postoperative late view; fibrosis peripheral ring Source: Virgilio Figueiredo Silva, MD Postoperative view; intraocular lens between anterior and posterior capsulotomy continued on page 40 Presentation spotlight

• Cover