Scott K. McClatchey

A comparison of the rate of refractive growth in pediatric aphakic and pseudophakic eyes

OBJECTIVE To compare the rate of refractive growth in pseudophakic childrens eyes to that of aphakic eyes. DESIGN Multicenter, retrospective observational case series. PARTICIPANTS 83 patients with pseudophakic eyes (100 eyes) and 74 patients with aphakic eyes (106 eyes), with an age of surgery between 3 months and 10 years and a minimum follow-up time of 3 years or more, depending on the age at surgery. METHODS A logarithmic model was used to analyze the rate of refractive growth for each eye. MAIN OUTCOME MEASURES Age at surgery, intraocular lens power, intraocular lens A-constant, initial postoperative refraction, final refraction, and final age. RESULTS Overall, pseudophakic eyes showed a lesser rate of refractive growth than aphakic eyes (-4.6 diopter vs. -5.7 diopter, P = 0.03). This trend was also present but less significant when the eyes were grouped into those less than 6 months of age at surgery (-3.3 diopter vs. -4.6 diopter, P = 0.09) and older patients (-5.0 diopter vs. -6.1 diopter, P = 0.07). However, the mean quantity of myopic shift was greater in pseudophakic eyes than in aphakic eyes (-5.26 diopter vs. -4.54 diopter), despite shorter follow-up times in the pseudophakic eyes. This is due to the optical effects of a constant intraocular lens power in a growing eye. CONCLUSIONS Pediatric pseudophakic eyes have a slightly lesser rate of refractive growth than aphakic eyes. The new rate values should be used for predicting future refractions in these eyes.

Theoretic Refractive Changes after Lens Implantation in Childhood

OBJECTIVE Children with aphakia tend to have decreasing hyperopia as they grow older. No large study of the long-term refractive changes in children with pseudophakia has been published, although myopic shifts of greater than 10 diopters (D) have been reported. The authors used the refractions of children with aphakia and long follow-up to calculate the theoretic long-term refractive effects of pseudophakia. DESIGN The study design was a chart review of eyes that underwent cataract surgery before age 10 with documented refractions for more than 7 years. PARTICIPANTS Ninety-three eyes were studied. INTERVENTION The initial aphakic refractions of the study eyes were used to calculate the intraocular lens (IOL) powers that would have been required to give emmetropia at cataract removal. The aphakic refractions at last follow-up were used to calculate the final pseudophakic refractions, and these were compared with the predictions of a logarithmic model of myopic shift. RESULTS The mean follow-up time was 11 years. The median calculated pseudophakic refraction at last follow-up was -6.6 D with a range of -36.3 to +2.9 D. Children who underwent surgery in the first 2 years of life had a substantially greater myopic shift than older children (P < 0.001) and a larger variance in this myopic shift (P < 0.001). The logarithmic model accurately predicted the final refraction within 3 D in 24% of eyes undergoing surgery before 2 years of age and in 77% of eyes undergoing surgery after this age. CONCLUSIONS Pseudophakia in children is predicted to result in a large quantity of myopic shift, particularly in very young children. An IOL power chosen to leave a child initially hyperopic should lessen both the quantity of myopic shift and the extreme myopia that can result with growth. The surgeon who implants IOLs in young children must be prepared for a wide variation in long-term myopic shift.

Myopic Shift After Cataract Removal in Childhood

BACKGROUND Children who have had cataract removal tend to have decreasing hyperopia (myopic shift) as they grow older. We wondered if the rate of myopic shift could be determined by age at surgery, cataract type, glaucoma, or other factors. METHODS We studied 156 aphakic eyes of children who had cataract surgery before age 10 and documented refractions for more than 3 years. Refraction was corrected with contact lenses and spectacles; glaucoma was managed with medicine and surgery. Stepwise multiple regression was used to analyze differences in the rate of myopic shift between subgroups. RESULTS The average refraction tended to follow a logarithmic decline with age (P < 0.01, R2 = 0.97). The average rate of myopic shift (the slope of spectacle plane refraction vs log of age, where age is in years and log is base 10) was -5.5, with a standard deviation of 3.8. Age at surgery had a small but statistically significant effect on the rate (P < 0.01, R2 = 0.04). No other studied factor reached statistical significance. However, among the 86 eyes with cataract removal after age 6 months, age at surgery was not as significant (P = 0.21), and unilateral cataract eyes tended to have a greater rate than bilateral cataract eyes (-7.7 vs -5.7; P = 0.05, R2 = 0.05). CONCLUSIONS Aphakic refraction tends to follow a logarithmic decline with age. The rate of myopic shift is determined partly by age at surgery and whether the cataract was unilateral or bilateral, although the effects are small. A wide variation in the rate of myopic shift exists. The following factors made little difference in the rate: cataract type, glaucoma, sex, side, and best corrected visual acuity.

Dissociated Horizontal Deviation

Despite the emphasis placed on the vertical aspect of the deviation by its currently accepted clinical label, dissociated vertical deviation is well known to include movements in both the torsional and horizontal planes. When the horizontal component is very prominent, dissociated horizontal deviation is suggested as an appropriate label. We report the clinical characteristics and surgical treatment of six patients with a dissociated horizontal deviation that was marked enough to be the reason for seeking medical attention. All patients underwent lateral rectus recession unilaterally or bilaterally, alone or in combination with superior rectus recession. In addition, we report the use of the darkening wedge test to demonstrate the Bielschowsky phenomenon in the horizontal plane. This phenomenon, a dissociated exotropia spontaneously moving toward and crossing the midline to become an esotropia under cover when a progressively darkening filter is placed over the fixing eye, has not to our knowledge been previously reported.

Intraocular lens calculator for childhood cataract

Purpose: To evaluate a computer program to predict the pseudophakic refraction of a child at any age. Setting: A pediatric ophthalmology practice. Methods: A computer program was written for Windows 95 that calculates the initial postoperative pseudophakic refraction of a child using Holladay’s formula, give the axial length and keratometry readings. The logarithmic model was used to predict the ultimate refraction at age 20 years and chart the predicted curve of refractive error with standard deviations. Results: The program provided a graph of a child’s predicted pseudophakic refraction versus age that would allow the surgeon to dynamically view the effects of changing the intraocular lens (IOL) power. Conclusions: If pseudophakia and aphakia have the same effect on the growth of the eye, this program should accurately predict the myopic shift of a pseudophakic child. This could help guide the surgeon’s choice of IOL power.

Predictability of Intraocular Lens Calculation and Early Refractive Status: The Infant Aphakia Treatment Study

OBJECTIVE To report the accuracy of intraocular lens (IOL) power calculations and the early refractive status in pseudophakic eyes of infants in the Infant Aphakia Treatment Study. METHODS Eyes randomized to receive primary IOL implantation were targeted for a postoperative refraction of +8.0 diopters (D) for infants 28 to 48 days old at surgery and +6.0 D for those 49 days or older to younger than 7 months at surgery using the Holladay 1 formula. Refraction 1 month after surgery was converted to spherical equivalent, and prediction error (PE; defined as the calculated refraction minus the actual refraction) and absolute PE were calculated. Baseline eye and surgery characteristics and A-scan quality were analyzed to compare their effect on PE. MAIN OUTCOME MEASURES Prediction error. RESULTS Fifty-six eyes underwent primary IOL implantation; 7 were excluded for lack of postoperative refraction (n = 5) or incorrect technique in refraction (n = 1) or biometry (n = 1). Overall mean (SD) absolute PE was 1.8 (1.3) D and mean (SD) PE was +1.0 (2.0) D. Absolute PE was less than 1 D in 41% of eyes but greater than 2 D in 41% of eyes. Mean IOL power implanted was 29.9 D (range, 11.5-40.0 D); most eyes (88%) implanted with an IOL of 30.0 D or greater had less postoperative hyperopia than planned. Multivariate analysis revealed that only short axial length (<18 mm) was significant for higher PE. CONCLUSIONS Short axial length correlates with higher PE after IOL placement in infants. Less hyperopia than anticipated occurs with axial lengths of less than 18 mm or high-power IOLs. Application to Clinical Practice Quality A-scans are essential and higher PE is common, with a tendency for less hyperopia than expected. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00212134.

The Optics of Aphakic and Pseudophakic Eyes in Childhood

The growth of the eye results in a myopic shift in aphakic and pseudophakic eyes during childhood. Cataract surgery after the age of 6 months, with or without lens implantation, appears to have little effect on the rate of refractive growth. Most children with pseudophakia have a large amount of myopic shift. This myopic shift is greatest in children with surgery at younger ages. It is also greater in eyes with high-power intraocular lenses due to an optical phenomenon analogous to the effect of vertex distance. The amount of myopic shift and the variance in rate of refractive growth can be predicted using an empiric, logarithmic model. We describe a revision of this logarithmic model to extend it patients with surgery before 3 months of age. We also analyze the variance in the rate of refractive growth, based on data from pseudophakic children with the longest follow-up in proportion to age.

The association between myopic shift and visual acuity outcome in pediatric aphakia

PURPOSE The advent of intraocular lens implantation after pediatric cataract surgery necessitates an increased understanding of refractive development. The significant variation in rate and amount of refractive change among eyes, both aphakic and pseudophakic, is well recognized, although the causes of such variation remain unclear. The purpose of this study was to determine if a correlation exists between the rate of refractive growth (RRG) and visual acuity outcome in pediatric aphakia. METHODS Multicenter, retrospective observational case series. One hundred and twenty-five eyes of 85 patients with cataract surgery before 1 year of age and a minimum of 3 years of follow-up were analyzed. RRG was calculated for each eye using the logarithmic model of ocular growth and compared with final logMAR acuity using linear regression. RESULTS The correlation of RRG with final logMAR acuity was statistically significant (r(2) = 0.10; P <.01), ie, 10% of variance in RRG is related to acuity outcome. The correlation was higher in unilaterally aphakic patients (n = 44; r(2) = 0.19; P <.01) than in bilaterally aphakic patients (n = 81; r(2) = 0.08; P <.01). Eyes with visual acuity of 20/60 or better had a significantly lower RRG than those with poorer acuity (4.1 v 5.4 diopters (D); P <.01). CONCLUSIONS RRG in aphakia is correlated with visual acuity outcome. Eyes with poorer acuity have a greater RRG.

Rhabdomyosarcoma of the Ciliary Body

Rhabdomyosarcoma is the most common malignant orbital tumor of childhood. It has twice been reported to arise within the globe from the iris. In addition, teratoid medulloepithelioma, a tumor arising from the ciliary epithelium, can contain a rhabdomyoblastic component, often in combination with other heteroplastic elements. The authors report what may be the first recorded case of an embryonal rhabdomyosarcoma of the ciliary body, possibly representing a one-sided differentiation of a malignant teratoid medulloepithelioma.

Choosing IOL power in pediatric cataract surgery.

In the 2008 Int Ophthalmol Clin, Krishnamurthy and VanderVeen wrote an outstanding, comprehensive overview of infantile cataracts, from etiology to surgical techniques, including a section on the myopic shift in these eyes. In this article, I will discuss the growth of the eye in detail, and how this and other factors can be considered in the choice of intraocular lens (IOL) power for children. Other excellent discussions of this subject can be found in books and online. Just as a child’s body grows from birth through adolescence, so the children’s eyes grow from infancy until adult life. The whole eye grows in a proportional fashion, with the increase in axial length matched by an increased size of the lens and cornea. The larger crystalline lens and cornea have surfaces with greater radii of curvature, resulting in lesser optical power. Thus, the increasing axial length is matched by a decrease in the power of the crystalline lens and cornea, resulting in a refraction that remains at or near emmetropia throughout life. However, when an infant or child has a cataract removed and is left aphakic, the optics of the growing eye has a profound effect on the refraction, resulting in an ever-decreasing hyperopia. Implanting an IOL with a constant power further complicates the matter, causing an even greater shift toward myopia for optical reasons alone. Just as some children grow faster than others, some eyes grow faster than others. Although we can estimate how tall a child will be by looking at their parents, as of this writing there are no factors that clearly indicate which eyes will grow faster than others. This results in large variability in myopic shift, and difficulty in predicting future refractions for any given child. Fortunately, this predictability is well studied, and a surgeon can accurately forecast the most likely refractive trajectory and the range of potential variance.