Faculty Bibliography

PURPOSE/OBJECTIVE:To study the progression rate of keratoconus and assess the clinical outcome of corneal collagen cross-linking (CXL) with riboflavin and ultraviolet A light in children and adolescent patients up to 3 years after treatment. METHODS:Fifty-nine eyes from 42 children and adolescents (aged 9 to 19 years) with confirmed keratoconus were included in this retrospective interventional cohort study. Refraction, slit-lamp examination, Placido-based corneal topography, and Scheimpflug imaging were performed bilaterally in all patients preoperatively and at 6 and 12 months postoperatively. Maximal keratometry readings (Kmax), corrected distance visual acuity (CDVA), corneal thickness, and the keratoconus index (KI) were analyzed. Follow-up was up to 36 months (mean follow-up: 26.3 months [range: 12 to 36 months]). RESULTS:Fifty-two of the 59 eyes enrolled in this study showed progression, corresponding to a progression rate of 88%. Forty-six eyes were treated by CXL. Maximal keratometry, CDVA, and KI showed significant changes over the follow-up period. However, significant Kmax reduction observed up to 24 months after CXL lost significance at 36 months. CONCLUSIONS:Cross-linking seems to be safe in children and adolescents. Progression of keratoconus occurred in 88%. We propose that awaiting documentation of progression is not mandatory and CXL in children and adolescents should be performed as soon as the diagnosis has been made. However, the effect of arrest of disease progression might not be as long-lasting as in adults and longer follow-up is needed to verify this trend.

BACKGROUND:Diced cartilage is a valuable material that has recently been added to the graft options in rhinoplasty. Shaping, fixation, and resorption are the main concerns with this material. Perichondrially attached diced conchal cartilage may be a new possibility to solve some of these problems. OBJECTIVES/OBJECTIVE:The authors evaluate the outcome of perichondrially attached diced cartilage in a rabbit model and compare the results with injectable cartilage grafting. METHODS:Ear cartilage was removed from 1 auricle in each of the 16 rabbits included in this study; samples were divided in 2 pieces. After precise weighing, both segments were diced. The perichondrium was left attached to 1 of the pieces. Both segments were inserted in 2 separate pockets in the dorsum of the animal. After a 3-month period, both samples were removed and measured for growth/resorption. RESULTS:At the beginning of this study, the difference in weight between groups was statistically insignificant (P = .213), but 3 months after insertion, significant growth was observed in the perichondrial group (P = .019). CONCLUSIONS:The vascularization and significant growth in weight of the perichondrially attached diced cartilage samples are evidence of the viability of this material. The structural integrity and solid framework afforded by this option suggest that the material should be used more frequently in nasoskeletal augmentation.

PURPOSE/OBJECTIVE:We studied the capabilities of the Argus II retinal prosthesis for guiding fine hand movement, and demonstrated and quantified guidance improvement when using the device over when not using the device for progressively less predictable trajectories. METHODS:A total of 21 patients with retinitis pigmentosa (RP), remaining vision no more than bare light perception, and an implanted Argus II epiretinal prostheses used a touchscreen to trace white paths on black backgrounds. Sets of paths were divided into three categories: right-angle/single-turn, mixed-angle/single-turn, and mixed-angle/two-turn. Subjects trained on paths by using prosthetic vision and auditory feedback, and then were tested without auditory feedback, with and without prosthetic vision. Custom software recorded position and timing information for any contact that subjects made with the screen. The area between the correct path and the trace, and the elapsed time to trace a path were used to evaluate subject performance. RESULTS:For right-angle/single-turn sets, average tracing error was reduced by 63% and tracing time increased by 156% when using the prosthesis, relative to residual vision. With mixed-angle/single-turn sets, error was reduced by 53% and time to complete tracing increased by 184%. Prosthesis use decreased error by 38% and increased tracing time by 252% for paths that incorporated two turns. CONCLUSIONS:Use of an epiretinal visual prosthesis can allow RP patients with no more than bare light perception to guide fine hand movement visually. Further, prosthetic input tends to make subjects slower when performing tracing tasks, presumably reflecting greater effort. (ClinicalTrials.gov number, NCT01123928.)

PURPOSE/OBJECTIVE:To report a patient who developed a left paracentral stromal scar due to infectious keratitis that occurred after corneal collagen cross-linking (CXL) for progressive keratoconus. The flattening effect of the scar led to an increase in visual acuity. METHODS:The corneal scar and flattening effect on the anterior corneal curvature were assessed by slit-lamp photography, high-resolution Scheimpflug imaging, and corneal confocal microscopy. RESULTS:Three days after CXL, a corneal bacterial infection occurred in the left cornea and was treated with local antibiotics that led to a paracentral scar. Twenty-one days after CXL, a flattening of the anterior curvature of >11.00 diopters was observed. As a consequence, corrected distance visual acuity improved by five lines. CONCLUSIONS:Corneal remodeling may lead to a homogenization of the anterior corneal surface and an increase in visual acuity. Remodeling may not only occur spontaneously following CXL, but also following an event that results in focal corneal scarring, such as corneal infection. In a highly irregular keratoconic cornea, the benefit of the flattening effect of a scar may outweigh the increase in aberrations and light scatter.

PURPOSE/OBJECTIVE:To investigate the elementary temporal properties of electrically evoked percepts in blind patients chronically implanted with an epiretinal prosthesis. METHODS:Nine subjects were presented with isolated stimuli of variable duration and pulse rate. Stimulation amplitude was set to the upper comfortable level and a group of 2 × 2 adjacent electrodes was simultaneously activated. First, subjects were asked to verbally describe their visual perception paying particular attention to the time-course of brightness. Then, in subsequent trials, they described the brightness time dependence using a joystick while auditory feedback of joystick position was provided. RESULTS:All subjects described a bright, well-localized percept at stimulus onset. Only one subject reported such a bright, well-localized visual sensation during an entire 10-second stimulation trial. For the remaining eight subjects, it faded more or less rapidly (in four cases <0.5 second) and was often followed by a percept described as less bright, poorly localized, and having different color. Only initial percepts at stimulation onset seemed bright and localized enough to reconstruct a patterned image. Changing stimulation pulse rate influenced the time course of perception only in some cases but the effect was not systematic. CONCLUSIONS:Percepts differed considerably across subjects, probably because of the considerable variations in the progression and remodeling processes associated with the disease. Appropriate coding of a patterned image under such conditions appears challenging. Further research of the underlying mechanisms of visual perception upon electrical stimulation of the retina is required to optimize stimulation paradigms and to better establish patient selection criteria.