Impact of photoreceptor density in a 3D simulation of panretinal laser photocoagulation

Background

During panretinal photocoagulation (PRP), the outer retina, especially the photoreceptors, are destroyed. During such procedures, the impact of the retinal photocoagulation, which is performed in the same photocoagulated area, may change if it is applied to different locations with different photoreceptor densities. Thus, we aimed to evaluate the influence of photoreceptor density on PRP.

Methods

We constructed a three-dimensional (3D) average distribution of photoreceptors with 3D computer-aided design (CAD) software using previously derived photoreceptor density data and calculated the number of photoreceptors destroyed by scatter PRP and full-scatter PRP (size 400-μm on the retina, spacing 1.0 spot) using a geometry-based simulation. To investigate the impact of photoreceptor density on PRP, we calculated the ratio of the number of photoreceptors destroyed to the total number of photoreceptors, termed the photoreceptor destruction index.

Results

In this 3D simulation, the total number of photoreceptors was 96,571,900. The total number of photoreceptors destroyed by scatter PRP and full-scatter PRP were 15,608,200 and 19,120,600, respectively, and the respective photoreceptor destruction indexes were 16.2 and 19.8%, respectively.

Conclusions

Scatter PRP is expected to have 4/5 of the number of photoreceptors destroyed by full-scatter PRP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01945-z.

[Ocular ischemic syndrome : An important differential diagnosis]

BACKGROUND

Ocular ischemic syndrome is a rare disease, which must be considered as a differential diagnosis in cases of painful loss of vision.

CASE REPORT

A 63-year-old male patient presented as an emergency in our consultation with hyphemia and decompensated intraocular pressure of the right eye. The right eye had been painful for 3 weeks. Apart from nicotine abuse, no relevant pre-existing medical conditions were known. With suspected iritis, the initial treatment was performed with eye drops containing a corticosteroid. After initial improvement in symptoms, an acute deterioration occurred with decrease in visual acuity and increased pain starting 2 days previously. Biomicroscopic examination revealed rubeosis iridis with hyphemia. Due to the hyphemia the view of the fundus was greatly reduced but there were no indications for retinal bleeding. In gonioscopy a chamber angle closure was evident. Fluorescence angiography showed a significantly longer arm-retina time, a delayed arteriovenous passage, peripheral vascular leaks and reduced fluorescence of the choroid. An ocular ischemic syndrome was suspected, therefore, duplex sonography of the carotid arteries and computed tomography angiography were performed and showed complete stenosis of the right internal carotid artery and moderate stenosis of the left internal carotid artery. An intravitreal administration of anti-VEGF and panretinal laser photocoagulation were carried out. Furthermore, an evaluation of the cardiovascular risk factors was initiated as part of the interdisciplinary investigation.