Pupillometric analysis for assessment of gene therapy in Leber Congenital Amaurosis patients.
BACKGROUND
Objective techniques to assess the amelioration of vision in patients with impaired visual function are needed to standardize efficacy assessment in gene therapy trials for ocular diseases. Pupillometry has been investigated in several diseases in order to provide objective information about the visual reflex pathway and has been adopted to quantify visual impairment in patients with Leber Congenital Amaurosis (LCA). In this paper, we describe detailed methods of pupillometric analysis and a case study on three Italian patients affected by Leber Congenital Amaurosis (LCA) involved in a gene therapy clinical trial at two follow-up time-points: 1 year and 3 years after therapy administration.


METHODS
Pupillary light reflexes (PLR) were measured in patients who had received a unilateral subretinal injection in a clinical gene therapy trial. Pupil images were recorded simultaneously in both eyes with a commercial pupillometer and related software. A program was generated with MATLAB software in order to enable enhanced pupil detection with revision of the acquired images (correcting aberrations due to the inability of these severely visually impaired patients to fixate), and computation of the pupillometric parameters for each stimulus. Pupil detection was performed through Hough Transform and a non-parametric paired statistical test was adopted for comparison.


RESULTS
The developed program provided correct pupil detection also for frames in which the pupil is not totally visible. Moreover, it provided an automatic computation of the pupillometric parameters for each stimulus and enabled semi-automatic revision of computerized detection, eliminating the need for the user to manually check frame by frame. With reference to the case study, the amplitude of pupillary constriction and the constriction velocity were increased in the right (treated eye) compared to the left (untreated) eye at both follow-up time-points, showing stability of the improved PLR in the treated eye.


CONCLUSIONS
Our method streamlined the pupillometric analyses and allowed rapid statistical analysis of a range of parameters associated with PLR. The results confirm that pupillometry is a useful objective measure for the assessment of therapeutic effect of gene therapy in patients with LCA.


BACKGROUND
ClinicalTrials.gov NCT00516477.
Department of Ophthalmology, Second University of Naples, Naples, Italy. paolo.melillo@unina2.it
Paolo
P
Melillo
Leandro
L
Pecchia
Francesco
F
Testa
Settimio
S
Rossi
Jean
J
Bennett
Francesca
F
Simonelli
D000328:Adult; D002986:Clinical Trials as Topic; D005260:Female; D015316:Genetic Therapy; D006801:Humans; D057130:Leber Congenital Amaurosis / Q000235:genetics / Q000503:physiopathology* / Q000628:therapy*; D008297:Male; D009460:Neurologic Examination / Q000379:methods*; D011680:Pupil / Q000502:physiology*; D012018:Reflex; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult