ORIGINAL ARTICLE Hierarchical Linear Modeling of Visual Acuity Change Over Time: Rate of Functional Recovery After Macular Hole Surgery WALTER WITTICH, MA, OLGA OVERBURY, PhD, MICHAEL A. KAPUSTA, MD, FRCSC, and DONALD H. WATANABE, MSc Department of Neurology and Neurosurgery-Neuroscience, McGill University, Montreal, Quebec, Canada (WW), Sir Mortimer B. Davis Jewish General Hospital, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada (WW, OO), Department of Ophthalmology, McGill University, Montreal, Quebec, Canada (OO, MAK), and Department of Psychology, Concordia University, Montreal, Quebec, Canada (DHW) ABSTRACT Purpose. To examine acuity recovery rate after Macular Hole (MH) surgery, using Hierarchical Linear Modeling (HLM) with linear and curvilinear regression analysis. Methods. Preoperative MH diameter (OCT) and acuity (ETDRS) were recorded in 20 eyes. Acuities were tested during follow-up (6 to 23 months), with three to eight measurements per eye. The resulting 95 acuities were analyzed using HLM. Variability at the level of the person was explained by change over time, using a natural logarithm conversion. Across patients, MH diameter was used to predict slopes and intercepts at the level of the individual. Results. MH diameter was able to account for significant amounts of variability in preoperative acuity (intercept) and significantly influenced rate of functional recovery (slope). A nonlinear approach to the data accounted for the largest amount of variance. Conclusions. Participants with larger MHs recovered relatively more acuity sooner while eyes with smaller MHs had better absolute acuity outcome. HLM provides important insight into the recovery process after MH surgery and is more flexible with follow-up data. In the context of MH treatment, most recuperation occurred during the initial 6 months. (Optom Vis Sci 2007;84:872–878) Key Words: visual acuity, Hierarchical Linear Modeling, growth curve analysis, rate of recovery, macular hole, visual acuity T he primary goal of Macular Hole (MH) surgery is to close the retinal defect by reattaching the edges of the macular tissue around the hole and to restore a continuous retinal layer. 1 As a result, visual acuity is likely to improve to a certain degree and this beneficial effect has been demonstrated across sev- eral studies. 2 Initially, MH stages proposed by Gass 3,4 greatly fa- cilitated how MHs were classified. Subsequently, the advent of Optical Coherence Tomography (OCT) provided more detailed information about the structural aspects of MHs. 5,6 What remains difficult is to predict functional outcome after anatomically suc- cessful treatment based on preoperative MH characteristics. One of the most frequently reported structural components of MHs is their size, commonly expressed as their central diameter. The association of preoperative acuity with MH size has not been consistent in the literature and has been reported as signifi- cant, 7–9 strong, 10,11 moderate 12–14 or not significant. 15,16 This inconsistency, however, may be due to small sample sizes, various acuity charts that were used, as well as variability in the accuracy of anatomical measurement techniques. Successful anatomical clo- sure of MHs has been associated with MH diameter and symptom duration. 13 In addition, other factors that are related to visual function after surgery have been identified, including preoperative acuity, 10 MH diameter, 9,12 duration of symptoms, 17 as well as compliance to face-down positioning. 18 It has been frequently re- ported that larger MHs are less likely to recover normal or near- normal acuity after treatment. 5,9,17,19 Few studies have evaluated the pattern with which vision con- tinues to improve beyond the initial 6 months after treatment. Previous work by Krasnik et al., 20 as well as Leonard et al., 21 has demonstrated that acuity improvement after MH surgery is a dy- 1040-5488/07/8409-0872/0 VOL. 84, NO. 9, PP. 872–878 OPTOMETRY AND VISION SCIENCE Copyright © 2007 American Academy of Optometry Optometry and Vision Science, Vol. 84, No. 9, September 2007