FOVEAL SENSITIVITY AND FIXATION STABILITY BEFORE AND AFTER MACULAR TRANSLOCATION WITH 360-DEGREE RETINOTOMY

Clinical utilization of microperimetry in ophthalmic surgery: A narrative review

Microperimetry is an emerging technology that provides concurrent analysis of retinal structure and function by combining retinal sensitivity and fixation analysis with fundus imaging. We summarize the substantial evidence validating the evolving role of microperimetry as an adjunctive assessment of visual function in the perioperative setting. We show that microperimetry provides useful complementary information to other established imaging and functional modalities in the perioperative setting for a wide range of vitreoretinal surgical procedures, as well as in cataract and refractive surgeries. This includes preoperative uses such as prognostication of visual and anatomical outcomes, timing of surgical intervention, and assessment of patient suitability for surgery-as well as postoperative uses including quantification of visual recovery, investigation of unexplained postoperative vision loss, and informing expected long term functional outcomes.

Photoreceptor images of normal eyes and of eyes with macular dystrophy obtained in vivo with an adaptive optics fundus camera

PURPOSE

To report on images of the human photoreceptor mosaic acquired in vivo with a newly developed, compact adaptive optics (AO) fundus camera.

METHODS

The photoreceptors of two normal subjects and a patient with macular dystrophy were examined by using an AO fundus camera equipped with a liquid crystal phase modulator. In the eye with macular dystrophy, the fixation point in the AO images was identified using scanning laser ophthalmoscope (SLO) microperimetric image superimposed on a color fundus photograph.

RESULTS

Photoreceptor cells were detected as bright dots approximately 4 microm in diameter in normal subjects. In the eye with macular dystrophy, the fixation point was located within the bull's eye lesion and uniform small whitish spots with irregular patchiness were observed in the AO images of this area. The distance between the small spots was 3-4 microm. In other parts of the bull's eye retinal lesion, the whitish spots were larger and of different sizes.

CONCLUSIONS

The photoreceptor mosaic could be identified in photographs of eyes of normal subjects and an eye with macular dystrophy in vivo by an AO fundus camera. In the eye with macular dystrophy, a relatively uniform photoreceptor mosaic was observed around the fixation point, whereas presumed debris of photoreceptor degradation was observed in the other bull's eye retinal lesion.

New algorithm for assessing patient suitability for macular translocation surgery

PURPOSE

We propose a case selection algorithm to assess suitability for macular translocation for subfoveal neovascular membrane (CNV) secondary to age-related macular degeneration. The algorithm is based on preoperative assessment of residual foveal function, as assessed by a slit-lamp fixation task and duration of visual loss, in patients with poor acuity. We validate our slit-lamp fixation task against an objective analysis (Nidek MP-1 Microperimetry) and proceed to examine surgical outcomes as selected by the algorithm.

METHODS

A prospective series of 27 consecutive patients with CNV underwent translocation at Moorfields Eye Hospital, London between May 2003 and May 2006.

RESULTS

Validation of the slit-lamp fixation task revealed 100% concordance in classification of fixation between the slit-lamp task and the microperimeter. At an average follow up of 12.2 months, the mean Early Treatment of Diabetic Retinopathy Study distance acuity improved from logMAR 0.88 to 0.68 (P < 0.03). Sixty-six per cent of patients achieved an acuity of < or =logMAR 0.8 (6/30), 22% an acuity of < or =logMAR 0.3 (6/12) and 33% gained three lines of acuity. The mean MN Read reading acuity improved from logMAR 1.23 to 0.91 (P < 0.01). Forty-four per cent of patients achieved an acuity of > or =logMAR 0.7 (N10), 15% an acuity of > or =logMAR 0.4 (N5) and 44% gained three lines of acuity.

DISCUSSION

We have demonstrated a simple case selection algorithm that is based on residual foveal function and suggests good outcomes. The strongest indicators of foveal function are fixation characteristics and duration of visual loss. In contrast to previous studies, our algorithm suggests good outcomes independently of preoperative visual acuity and CNV characteristics.

RPE transplantation and its role in retinal disease

Retinal pigment epithelial (RPE) transplantation aims to restore the subretinal anatomy and re-establish the critical interaction between the RPE and the photoreceptor, which is fundamental to sight. The field has developed over the past 20 years with advances coming from a large body of animal work and more recently a considerable number of human trials. Enormous progress has been made with the potential for at least partial restoration of visual function in both animal and human clinical work. Diseases that have been treated with RPE transplantation demonstrating partial reversal of vision loss include primary RPE dystrophies such as the merTK dystrophy in the Royal College of Surgeons (RCS) rat and in humans, photoreceptor dystrophies as well as complex retinal diseases such as atrophic and neovascular age-related macular degeneration (AMD). Unfortunately, in the human trials the visual recovery has been limited at best and full visual recovery has not been demonstrated. Autologous full-thickness transplants have been used most commonly and effectively in human disease but the search for a cell source to replace autologous RPE such as embryonic stem cells, marrow-derived stem cells, umbilical cord-derived cells as well as immortalised cell lines continues. The combination of cell transplantation with other modalities of treatment such as gene transfer remains an exciting future prospect. RPE transplantation has already been shown to be capable of restoring the subretinal anatomy and improving photoreceptor function in a variety of retinal diseases. In the near future, refinements of current techniques are likely to allow RPE transplantation to enter the mainstream of retinal therapy at a time when the treatment of previously blinding retinal diseases is finally becoming a reality.

Surgical management of age-related macular degeneration

The development of increasingly refined vitreoretinal surgical techniques has resulted in a variety of surgical procedures for age-related macular degeneration (AMD). These have included submacular surgery with removal of choroidal neovascular membranes and subretinal blood, intraoperative lysis of feeder vessels, pneumatic displacement of subretinal blood and macular translocation surgery. The goals of these procedures have been to improve upon the poor natural history of exudative AMD and restore useful central vision. This article reviews the varied approaches, results and complications of the surgical management of AMD.