Before surgery, the following tests should be performed:
- Full medical eye examination including: Slit lamp, IOP, cornea, iris, anterior chamber, lens, vitreous and retinal examinations.
- Distance visual acuity (performed in each eye separately): ETDRS acuity with best correction.
- Near visual acuity (performed in each eye separately): ETDRS acuity with best correction.
- Visual acuity with x2.5 external telescope – best corrected, distance and near on each eye (ETDRS). *
- Pupil diameter – Photopic and scotopic.
- Pupil centartion – if the pupil is not centered you may need to perform pupiloplasty.
- Cycloplegic refraction.
- Specular microscopy – Endothelial cell count.
- A-scan (anterior chamber depth).
- Keratometry (K reading) or corneal topography.
- Fundus and macular area photography.
- OCT or F.A.
*Important note for ophthalmologist/optometrist visual testing:
Most ophthalmologists do not have a x2.50 external telescope in their office, but it is essential for testing and making a decision if the patient can be considered for implantation and if the patient should be sent for further optometric evaluation.
Test one eye at a time while the fellow eye is covered.
For testing distance vision you can use an external telescope with x2.50 magnification. The patient should use it with best correcting glasses when reading from the vision chart (we recommend using ETDRS).
Explain to the patient that the telescope is used to demonstrate only magnification and not the visual field. S/he will enjoy a larger visual field compared to what s/he can see with the simulator telescope that gives only narrow visual field.
For testing near vision you can add a +10.00 Diopters lens in front of the best corrected near vision glasses and bring the reading material to 10 cm from the eye. This can simulate the size of letters that the patient will be able to see when a telescope of 2.50 Mag will be used.
Again, explain to the patient that s/he would be able to see the chart from a normal distance and this is only a simulation for the size of image that s/he may see after implantation.
If the patient sees 2 or 3 lines better on the ETDRS chart compared to the vision without the telescopic effect, when tested for distance (with the x2.50 telescope) or for near (with the +10.00 D lens), s/he can be considered as a reasonable candidate and should be referred to a more thorough optical evaluation by a low vision specialist before making the final decision.