Peli’s Field Expansion Prisms.pptx

Peli's prism , Peli's Field Expansion Prism , Working of peli's prism, about peli's prism, Characteristics of peli's prism, Field of view expansion by peli's prism ,Fitting of peli's prism, Training with peli's prism, Adjusting to peli's peripheral prism , types of visual field , Definition of peli's prism , Success rate of peli's prism , How the expanded visual field appears , Homonymous hemianopia , some case studies

1. Peli’s Field Expansion Prisms By – Chandamita Das B Optom 2 nd Year

2. CONTENT Definition of Peli Prism Homonymous Hemianopia How the Expanded Visual Field Appears Normal vs Hemianopic vs Expanded Visual Fields Adapting to Peli Peripheral Prism Fitting of Peli Prism Training with Peli Prism Success rate with Peli Prism Some case studies

3. Peli’s Prism Peli prisms are Fresnel prisms for visual field expansion in homonymous hemianopia. Peli prisms are also known as peripheral prism , expansion prism or peli lens. It is also known as “EP” or Expansion Prism concept and was developed by Dr. Eli Peli of Schepens Eye Research Institute in  1999 .

4. May be ordered with one or two prism segments (double segment). The double segment has one prism at the upper part of the lens and one at the lower, with a distance of 12 mm between the segments.

5. Homonymous Hemianopia Homonymous hemianopsia (or hemianopia) is a field loss deficit in the same halves of the visual field of each eye, often resulting from cerebrovascular injury (stroke)or tumor. Normal Visual Field Hemianopic Visual Field

6. How the Expanded Visual Field Appears The goal of the Peli Lens is to help patients make the most use of their remaining vision. If the patient can appreciate any movement on the “blind” side or can relatively localize to some objects on the blind side , the patient may not find the peli prism very beneficial. The patient and the practitioner should set realistic expectations and goals before embarking on the Peli prism – fitting trial.

7. By placing peripheral prisms in the patient’s blind side, they can notice movement and contrast from their missing visual field. This often enables patients to significantly increase their awareness of their blind side

8. View from Above Below you’ll see a view from above of how a hemianopic patient’s visual looks normally and how the field looks while wearing the Peli Lens. Homonymous Hemianopia Visual Field Homonymous Hemianopia with the Peli Lens

9. Normal vs Hemianopic vs Expanded Visual Fields Here’s another way to visualize the difference between normal vision, hemianopic vision, and vision using the Peli Lens. Full Visual Field Hemianopia Visual Field Expanded field with superimposed image

10. Adapting to Peli Peripheral Prisms This superimposed field expansion described by Peli Lens wearers can take some getting used to. With training, patients are easily able to differentiate their regular field from the expanded field. The patient should be made aware that the real object is in the blind field , and that he/she needs to move his/her head to localize to the correct position. We recommend that a patient wear training prisms for 4-to-6 weeks and spend about 20 minutes a day performing self-training exercises to help with adaptation.

11. Fitting peli prisms for HH Preparing for fitting Observe patient’s normal head and walking posture when greeting the patient. Placing template Clean patient’s glasses. Put glasses on patient and apply template on front side of the lens on HH side. Center template dot over patient’s pupil. If black patches on template overlap frame rim, re-adjust frame and re-apply template to eliminate overlap as much as possible. Prisms are fit monocularly on the side of the hemianopsia: Right side for right hemianopsia Left side for left hemianopsia.

12. Placing occluder Add occluder to the other lens. If necessary , use smell tabs of scotch tape to temporarily secure template to lenses. Positioning template Have patient walk naturally back and forth infront of the examiner. Observe head posture while comparing to earlier stance and position observation. Ask patient if black template portions and obstructing vision at the top or the bottom. Re-adjust if necessary and repeat observation, making adjustments as needed.

13. Placing Prisms On rear surface of lens, place one clean Peli press on prism, pointed-end toward temporal, directly over one of the black portions of the template. Repeat with second Peli press-on and press both firmly in place. Verify separation of 12 mm and base direction (out). If prisms overlap the edge of the frame, the excess should be trimmed. Verifying Placement Put the glasses on the patient to re-verify placement. Remove occluder, template, and markings while leaving the prisms in place.

14. Overview of prism use Instruct patient not to look into the prisms . Peli prisms expand the peripheral vision which enables the patient to detect objects in the blind field. The patient should be taught that looking into the prisms will cause double vision. They should always look through the prism-free central portion of the lens.

15. Reach and Touch Training While the patient is fixating on the examiner’s nose, reach examiner hand into the patient blind side and have patient grab at the examiner’s hand as he/she detects it through the prisms . It may takes 3 times before he /she succeeds. This “game” should be practiced at home.

16. Training walk This is similar to patient adaptation to wearing bifocals for the first time. Again, observe patient’s head posture to detect possible need for adjustment of frames or prism placement. Lead patient from uncluttered areas such as a halfway to progressively cluttered areas such as a waiting room filled with chairs as potential obstacles. Constantly ask patient to report his/her observation .

17. Success Rates with the Peli Lens In the initial trial of the Peli Peripheral Prisms, 74% wished to continue wear after the 6-week assessment. At the end of the first year, 47% of patients continued to wear the prisms. 

18. Case study 1 A 69-year-old man with left homonymous hemianopia following a cerebral stroke wanted Peli prisms to improve his mobility and driving. He had 20/20 unaided visual acuity. The patient wanted the Peli prism over his safety goggles for driving. The patient appreciated the field expansion with the trial. The Peli prisms were fit over his safety goggles and dispensed. Patient was cautioned for driving. The field expansion experienced by this patient will be smaller due to the larger vertex distance of the safety goggles .

19. Case study 2 A Peli prism is prescribed for a 15-year-old boy with left homonymous hemianopia following surgery for pilocytic astrocytoma at the age of 5 years. Peli prism trial on children has not been reported before. The child had 20/20 visual acuity in both eyes. The child was able to appreciate the field expansion and was prescribed 40 temporary prism. In a subsequent visit 2 years later, the patient was keen to take the 57 peli oblique prism . The oblique prism base is oriented down and out in the upper segment and up and out in the lower segment. Such an orientation would facilitate detecting objects closer to the central visual field.

20. Case study 3 A 61-year-old female with right homonymous hemianopia was referred for Peli prism trial from the neuro-ophthalmology clinic. The patient had a history of ventriculoperitoneal shunt because of increased cerebrospinal fluid pressure. She had hypertensive retinopathy. Her best-corrected visual acuity was 20/30, N6 with her progressive addition lenses (PAL). We attempted fitting Peli prisms in this patient over her PAL, since she was not willing to change to bifocal spectacles. In case of bifocals, the Peli prism is mounted above the bifocal segment, so that it does not interfere with reading.

21. However, PAL pose two problems: there is no clear demarcation line for the near and intermediate addition power and PAL's peripheral aberrations can also be shifted with the prisms. The patient was able to appreciate the field expansion with the Peli prism and was given a home trial for 2 weeks. The patient returned to the clinic after 15 days and reported that she was uncomfortable and wanted to discontinue the Peli prism. The Peli prisms were removed and she was advised head scanning to manage her hemianopia.

22. Thank You