Metamorphopsia, Retinal Detachment
Conditions
Brief summary
Patients may experience metamorphopsia, or image distortion, after having vitrectomy to repair their rhegmatogenous retinal detachments especially those with a detached macula. Retinal displacement, as measured on autofluorescence photography, likely contributes to this distortion. It is thought that the retina slips inferiorly due to the residual subretinal fluid shifting as the patient transitions from the supine position intraoperatively to the sitting up position in the immediate postoperative period. By having the patient immediate position facedown or according to the retinal break, the risk of slippage is theoretically decreased.
Detailed description
Rhegmatogenous retinal detachments (RRD) are a sight-threatening condition with an incidence of approximately 10 per 100 000 people. RRDs can be broadly classified into those with the macula still attached, and those with the macula detached. Visual prognosis for RRDs with attached macula tend to be much better than those with detached macula. Pars plana vitrectomy (PPV) is one of the procedures used to treat RRD. PPV is carried out in the operating room under regional anesthestic, and often times sedation. The retina is reattached by either draining the subretinal fluid through a peripheral retinal break, by draining the subretinal fluid through a posterior retinotomy, or by using a heavier-than-water liquid such as perfluorocarbon to push out the subretinal fluid. At the end of the surgery, the vitreous cavity is filled with a substance that will tamponade the retina to the wall of the eye. Tamponade agents can be temporary, such as sulfur hexafluoride (SF6) and octafluoropropane (C3F8), or long term, such as silicone oil. After the surgery, patients are usually told to put their facedown allowing the tamponade agent to keep the macula attached while the remaining subretinal fluid is reabsorbed by the retinal pigment epithelium. Alternatively, some surgeons ask that their patients position according to the location of their retinal breaks with the aim for the buoyant gas bubble to cover the break or breaks. Patients may experience metamorphopsia, or image distortion, after having their RRD repaired especially those with a detached macula. Retinal displacement, as measured on autofluorescence photography, likely contributes to this distortion. Supine positioning in theory covers all break locations as usually breaks occur in the anterior part of the retina near the vitreous base. This position has the advantage of being more ergonomic than face down. Depending on the results, this study might provide evidence for the current standard of care, which is face down positioning for the first day after vitrectomy for retinal detachment. Or, if supine positioning demonstrates superiority in reducing the risk of retinal displacement, patients would be able to maintain a more comfortable position after surgery.
Interventions
BEHAVIORALFace down positioning
See description of the face down positioning group
BEHAVIORALSupine positioning
See description of the supine positioning group
Sponsors
Unity Health Toronto
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
SINGLE (Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* Age ≥ 18 * Diagnosis of primary rhegmatogenous retinal detachment needing pars plana vitrectomy with the detachment involving at least one of the temporal vascular arcades, which would allow retinal displacement to be detected on fundus autofluorescence photography
Exclusion criteria
* Rhegmatogenous retinal detachment with an attached macula * Proliferative retinopathy grade C or worst * Prior vitrectomy for retinal detachment. Patients having had pneumatic retinopexy that failed to completely reattach the retina and therefore now needing vitrectomy are allowed into the study * History of preoperative binocular diplopia * Tamponade with silicone oil instead of gas * Inability to maintain post operation head positioning * Mental incapacity
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Retinal displacement | 3 months | The presence of retinal vessels printing on fundus autofluorescence imaging. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Visual Distortion | 3 months | measured with M chart. |
| Aniseikonia | 3 months | Measured with aniseikonia testing. The aniseikonia test measures the ratio of image size difference between the 2 eyes |
| Optical coherence tomography (OCT) changes | 3 months | Changes seen on OCT |
| Optical coherence tomography angiography (OCTA) changes | 3 months | Changes seen on OCTA |
| Metamorphopsia | 3 months | Metamorphopsia is the image distortion experienced by the patient. It will be recorded in a data collection sheet as yes or no according to the patient subjective complain on metamorphopsia. |
| Best corrected Visual Acuity measured in Early Treatment of Diabetic Retinopathy Study letters | 3 months | Best corrected Visual Acuity measured in Early Treatment of Diabetic Retinopathy Study letters |
Countries
Canada
Outcome results
None listed