This document summarizes key information about hard contact lenses, including their advantages, disadvantages, indications for use, and fitting procedures. Hard contact lenses are made of PMMA or similar materials. They are durable, have a long lifespan, provide clear vision, and only require one fitting visit. However, they can be uncomfortable, fall out, break, or warp. Common uses are for astigmatism, aphakia, keratoconus, and during certain medications. The fitting process involves keratometry, trial lenses, adjusting for diameter, base curve, and power. Proper centration, lens movement, and hygiene are important to avoid problems.

1. Dr. Ankit Punjabi P.G., Dept of Ophthalmology K.I.M.S. Hospital, Bangalore Email: drankitalways@gmail.com

2. HARD CONTACT LENS PMMA or its congeners Advantage : Less cost Easy to handle Easy to clean, store & maintain

3. HARD CONTACT LENS Durable and long life span (15/20 yr.) Easy to fit, only one sitting (visit) necessary Better vision due to better optics of anterior refracting surface Do not absorbs significant amount of late

4. HARD CONTACT LENS Disadvantages : Longer period of adaptation Wind and dust bother the wearer May fall off spontaneously on lateral version May break under enough pressure May warp and go flat when exposed to excess heat Difficult to wear intermittently as they require period of adaptation

5. INDICATION Astigmatism Aphakia Progressive myopia Keratoconus Topical medications

6. FITTING PROCEDURE Keratometry Trial Set :- Diameter – 7 to 9 mm (.05 mm interval) Base curve – 7 to 8.4 mm Central thickness - .1 to .2 mm Power +/- 25 D

7. DIAMETER Corneal diameter & palpebral aperture 9 mm

8. BASE CURVE Mean of the two K reading Flatter K Flatter than K – spherical cornea

9. POWER L.P. – Lens power B.V.P. – Back vertex power .25 D for every .05 mm change in radius More – as radius is steepened

10. INSERTION & REMOVAL OF LENS

11. CENTRATION OF LENS

12. BLUE LIGHT SOURCE

13. FL STAIN

14. FLAT LENS STEEP LENS

15. TORIC CORNEA

16. IDEAL PATTERN FALSE PATTERN

17. HYGIENE Preservative & anti bacterial

18. PROBLEMS Tight fit : Little movement FL patterns Removal difficult Remedy : Flat Small Lens

19. LOOSE LENS Flat lens Too much movements FL pattern Remedy : Steep lens large, lens

20. LOW RIDING LENS Thick Heavy plus Remedy Large, flat, lenticular lens High riding lens Thin – lens

21. High riding lens Low riding lens

22. Side version

23. Hz. Displaced lens Astigmatism Remedy-Steeper lens

24. WARPAGE Rough Handling Excessive pressure during cleaning

25. Thank you