May 19, 2011 - Clemens Alt

Optical Methods for Retinal Laser Therapy and Imaging

Lasers increasingly find their way into therapeutic and diagnostic devices in ophthalmology. Here, we discuss two research directions that we have been pursuing over the past years.

Selective laser targeting of the Retinal Pigment Epithelium (RPE) is a novel treatment modality for retinal diseases associated with an initial RPE dysfunction. The treatment limits the exposure time of RPE cells to a few microseconds in order to minimize heat diffusion into adjacent photoreceptors and avoid their thermal destruction. As a result, selective laser lesions are invisible in slit lamp examination, leaving the ophthalmologist without any feedback about the success of the laser irradiation. We developed an online feedback mechanism based on cavitation detection to ensure correct dosimetry for efficient irradiation while preventing over-treatment. The feasibility of identifying RPE cell death by detecting intracellular cavitation was demonstrated in rabbits with a laser scanner that monitors backscattering of the treatment laser beam during selective laser targeting.

One obstacle to developing treatments for retinal disease more efficiently is the fact that most current knowledge of retinal processes in health and disease has been gained from ex vivo examination. However, the retina is, due to the transparency of the ocular media, accessible to optical in vivo imaging. Therefore, we have developed a scanning laser ophthalmoscope (SLO) specifically for retinal imaging in the mouse eye. Using three laser wavelengths and a video-rate scanner, the instrument is able to acquire three-color images in real-time. That means that three distinct cell populations can be tracked simultaneously and repeatedly. The instrument is able to resolve retinal microstructure, such as retinal ganglion cells and microglia, the retinal neurons and immune cells, respectively. The effect of raised intra-ocular pressure (i.e. glaucoma) is investigated in retinal ganglion cells. We study the spatio-temporal response of microglia to retinal injury models of gamma irradiation and focal laser injury employing real-time and time-lapse imaging.



Clemens Alt

Clemens Alt received his B.S. from the University of Applied Sciences Lübeck, Germany and the Medical Laser Center Lübeck, Germany. For his work on developing a laser scanner for simultaneous RPE treatment and cavitation detection, he received his PhD from the department of Biomedical Engineering at Tufts University in 2008. After changing research direction towards retinal imaging during his postdoctoral training at the Wellman Center for Photomedicine, he is now an Instructor at Massachusetts General Hospital, Harvard Medical School.


DINNER reservations are required by 6 PM, May 15, 2011, the Sunday of the meeting. MEETING ONLY reservations are required by noon, May 17, 2011, the Tuesday before the meeting.

Please make reservations online. Reservations may also be left on the answering machine at 617.584.0266. We no longer have an email address for reservations due to SPAM. When making reservation requests, please provide the following information:

  • DINNER AND MEETING or meeting only
  • Name(s) and membership status
  • Daytime phone number where you can be reached (in case of change or cancellation)


Rebeccas Cafe (Located in back of the office complex)
275 Grove Street
Auburndale, MA 02466

(617) 969-3282

(Map to Rebecca's).

Networking—5:45 PM, Dinner—6:30, Meeting—7:30 PM.


Vegetarian option available on request

Dinner Prices:

  Register on/before
DINNER Reservation Date
Late Reservation or
at the door 
NES/OSA Members and their guests $25.00 each $30.00
Students $15.00 $15.00
Non-members $30.00 (See NOTE Below) $35.00





NOTE: The NES/OSA has not changed dinner prices in several years but has been facing higher costs. We will maintain the current dinner prices for those reserving dinner on the requested date but still try to accommodate late reservations.

General Information on NES/OSA Meetings

Cancellations and No-shows:

If the meeting must be canceled for any reason, we will try to call you at the phone number you leave with your reservation. Official notice of cancellation will be on our answering machine.

We have to pay for the dinners reserved as of the Tuesday before the meeting, so no-shows eat into our cash reserve. If you will not be able to attend, please let us know as early as possible. Otherwise, no-shows will be billed.

Membership Rates:

Regular members $15.00
Student members free




NOTE: The extra $5.00 of the non-member dinner fee can be used toward membership dues if the nonmember joins and pays dues for the current year at the meeting.