Pre-Fitting - History

Transcription

1 Pre-Fitting History taking External exam Prescriptions Keratometry/Topography Lens Selection Soft and RGP Insert and Removal (I&R) Tools Stacy Campbell NCLE-AC, COA Eye Care Associates Previous Contact Lens Experience How long ago did they try? Why did they stop? Why do they want to try again? What are their expectations Pre-Fitting - History No Contact lens Experience Why do they want to wear contacts? What do they know about contact lenses? What are their expectations? Things that could affect contact lens wear Medications Oral Contraceptives Antihistamines/decongestants Accutane (acne medications) Eye drops Insulin Thyroid medications Diuretics Antidepressants Immunosuppressant's Allergies Seasonal Contact Allergies to materials Latex or Silicone Medical Conditions Diabetes Thyroid Pregnancy Menopause Epilepsy Abnormal Blood Pressure Psychiatric disorders External Exam Lids and lashes Check for signs of blepharitis (flip lids) Look at the elasticity of the lids (important in RGP fitting) Check Fissure openings (important in RGP fittings) TEARS Very important to contact lenses! TBUT (tear break up time) Instill FloGlo into the lower lid Allow a few minutes to spread across the eye Look at cornea, good time to check the surface of cornea for defects Instruct the patient to blink and then hold their eye open until you tell them to blink and count how long it takes before you see the stain disappear in spots. This is also a good time to look at the health of the cornea des/slide_14.jpg Lacrimal Lake The lacrimal lake it the thin layer of tears in the lower lid. There are three layer to the tear film! Mucous, Aqueous, and Lipid 1

2 Hands and Hygiene Prescription HVID - Horizontal Visual Iris Diameter This is measured in millimeters and can be done using any type of ruler. There are special tools you can use also. Hold the measuring devise up to the eye and measure (horizontally) the iris. This can be important when deciding base curves and diameter of both soft and RGP lenses. You can also get HVID from a topography. Hand hygiene is very important for patients who want to wear contact lenses. A good clue is to look at their fingernails. Also look at make-up use All contact lens fittings are done in Minus cylinder. If Rx is in plus cyl then you must transpose first. OD X = Change cyl to minus and change axis 90⁰ X 90 Vertexing (VT) high powered Rxs (anything over -/+ 4.00) MR OD sph VT = OS sph VT = Contact lenses only come in 0.25 steps and some brands in 0.50 steps after a certain power (-6.00 usually) the best option, if the lenses do not come in the vertex power according to the chart, try the power lower when working in minus and higher power when working with plus It is always best to under minus than over. MR sph VT = sph VT = The contact lens Rx you would try first would be: For the myopia: OD OS For the hyperopia: OD OS The formula for vertexing is the same for contacts and glasses Fc=F/(1-xF), Fc is the vertexed power, F is the original power, and x is the vertex distance in meters = F X = 12mm = Meters 1-XF (0.012 X-6.00 = ) = /1.072= Spherical Equivalent SPH equivalence is done with low cylindrical powers, under Transpose to minus cyl Divide the cyl in half and add it to the sph power Don t forget to vertex powers over / X (half) = Add & Sph E = X vt = turns into & =

3 Keratometery readings or Ks are the measurement of the cornea used to start a contact lens fitting. Key work is START The standard Keratometer range is: (flat) to (steep) is considered middle of the road 1. find reflection of circles on eye. a. look for black + and put in the middle of the right bottom circle/s-doubled b. focus the right bottom circle/s into one solid crisp circle c. align the + (white to the left of the circle you just focus) symbols into one + d. align the (above the bottom rt circle) Recording Ks Horizontal Axis 180 Vertical Axis 90 Topography A topography is another good way to get Ks It also helps in getting a visual of the surface of the eye, especially for irregularity's Both the Keratometer and Topographer will help with corneal cylinder Ks 44.00/45.00 = 1.00 D corneal cyl This is important when fitting toric and rgp lenses. This picture is with the rule corneal astigmatism, good choice for RGP If someone's Rx has 1.00 D cyl and no corneal cyl a soft toric lens is a better option How do we chose between soft and RPG? Ask the patient Have you worn contacts before? What kind of contacts have you thought about? What kind of activities will you be doing with your contacts on? What are your visual expectations? Lens Selection Soft vs RGP All contact lenses have: Base Curve = average for soft is , RGPs based on fitting technique and patients Ks Diameter = soft and RGPs varies (9.7 is my average) Optical Zone = varies Dk/t = Dk defines the ease with which oxygen passes through it and the t is the thickness of the lens 3

4 Advantages Soft Contact Lenses Very short adaptation period Comfortable Readily available, trials in office Available in a wide variety of Rxs Colors Wide variety of replacement schedules Great for active people & sports Some can be slept in Easy to clean Disadvantages Doesn t correct all vision problems, not as sharp as RGP Lenses have to be replace frequently Tears, rips, hard to keep clean, easy to lose. Sleeping in lenses increases risk of complications Difficult to handle More difficult to insert and remove than RGP There are several types of soft contact lenses. First you want to know, how often the patient wants to wear the contacts and much cleaning they are willing to do. Next, have a discussion with the patient of their options. Third, look at their Rx to see if they need a lens for an astigmatism, bifocal, or both. Soft Contact Lenses Fitting lens modality advantages disadvantages Single use healthy cost no cleaning needed plenty of extra lenses easy to travel with good for people with dry eyes and allergies come in SyHy takes up space not in multifocal toric Week healthy not available in SyHy easy replacement schedule cost Two week less cost cleaning comes in SyHy material not in multifocal toric needs to be cleaned people keep lenses longer not in multifocal toric Monthly less cost needs to be cleaned comes in SyHy material cleaning Fitting of a soft lens Once you ve decided on a modality it is now time to try on some lenses! First things, look at the size of the eyes bigger eyes = steeper eyes. Next, look at the Ks Medium K is around Steep is over Flat is under These measurements are just a starting. The best thing to do is try the lenses on and look at them! The two key things to look for are: 1. Centration easy replacement schedule comes in multifocal toric people keep lenses longer 2. Movement Centration The lens rides low 1. Usually it means the lens is too loose. Try a steeper lens or larger diameter. The lens rides high 1. Usually a sign the lens is too tight or diameter is off. Try flattening the base curve. A perfect centered lens will be at least 2mm outside the limbus 360 degrees. Have the patient look side to side to make sure the lens is centered in all gazes. *One thing you should do if you have a lens that is not centering is to Flip the Eye lids! It could be a sign of GPC (Giant Papillary Conjunctivitis) Movement of a soft lens Once you have a lens that is centered you ll need to look at the movement. Place patient in the slit lamp Use a narrow beam at about 45 degree angle and look at the edge of the lens as the patient blinks. Look at both temporal and nasal sides of the eye. Have the patient look up and watch for movement. The lens should move around 1-2 mm. Using a vein on the white of the eye as a guild to see if the lens moves. Excessive movement could lead to irritation. Make sure when the patient blinks the lens never hits the limbus. Sometimes it is difficult to see any movement. Another way to check is with the thumb push method. Too tight flatten base curve decrease Diameter 8.6 = = 13.8 Too Loose Steepen base curve Indrease Diameter 8.6 = = 14.2 Toric Check for Centration and movement One key thing with checking a toric is the hash marks on the lens they sit at 6 O clock or 3-9 O clock If they sit right or left of where the mfg. suggest you have to modify the axis- each clock is 30 degrees! X 180 Left ADD X 010 LARS Right subtract X 170 4

5 Multifocal Concentric Bifocal is the most common design lens for multifocal. This design is the near correction is located in a at the center of the lens and is surrounded by a larger circle that contains the distance correction. There is also the design where the distance is in the center and the near on the outer ring. Usually with that design one eye has a lens for with the near (N) in the center (non-dominate eye) and the other eye has the distance (D)in the center. Translating bifocals are also available, but only in RGPs. This design is similar to a lined bifocal in glasses. Presbyopia Fitting Monovision lenses: This style of fitting a presbyope will use your dominant eye for your distance vision and your nondominant for reading. This can be a good option but has it s limits. Once the patients add gets two high and the demand for intermediate vision increases the patient has to make a choice with having near vision or intermediate vision. This method of fitting can also affect depth perception. Since both eyes are working independently it is difficult for stereopsis I always recommend my monovision patients to get glasses for over the contacts for driving. Multifocals-always read the mfg. instructions they are very helpful Check for eye dominance! Use fogging method Ask the patient which eye they think is dominant. Do they fire a weapon? What eye to they aim with? Do they use a regular camera? Which eye do they look with? Have them wink at you. Most people will close their nondominant eye to wink. When all else fails, just start putting contact lenses on and play around! I&R (Insert and Removal) Wash hands no antibiotic, lotion, or scented soaps inside out/right side Taco Bowl Some lenses have markings Insert: YOUTUBE 1. Place contact lens on index finger 2. Check with taco test that it is not inside out 3. Place arm opposite of eye that will receive the lens on top of the lash area of lids. Keep firm grip of upper lid. 4. Use other hand to grasp of lower lid while keeping contact lens on index finger. 5. While keeping chin down, face the mirror and insert the contact onto the cornea until it touches 6. Look down and then straight to align contact onto cornea Removal: J method 1. Place front side of index finger onto colored part of eye 2. Tilt chin downwards. 3. Press index finger into eye and push into eye. 4. Pull contact down and roll finger outwards Removal: Pointer method 1. Clasp hands together 2. Point both index fingers upwards while still clasping hands 3. Open eyes wide while looking in the mirror chin down 4. Press index fingers onto eye while creating a gap between them (should be able to see self in the mirror though fingers) 5. Pinch index fingers together and pinch contact out. 5

6 Hands like you were putting in the lenses, one on top lid one on bottom Use index finger to slide lens down Pick out with thumb and index finger Pick out method Advantages Excellent Vision Corrects most vision problems Very easy to insert and remove Does not tear Easy to clean and store A pair can last up to two years (some people keep them longer) Available in tints (not for changing eye color) Excellent choice for a bifocal Available for Myopia control RGP Lenses Disadvantages Longer adaptation period Requires constant wear to stay accustom to the feel Can slip of center and even pop out Debris can get trapped under the lenses (painful) RGP Hard Lots of ways to fit RGP lenses First take a good look at where the eyelids interact with the cornea This will help decide what style of fit Lid attachment or Apical clearance Either way the best way to fit it to put lenses on and look at stain patterns. Look at the Ks are they with the rule or against! You can fit both but for a beginner stick with With! There are a few formulas again read the instructions on your trial kits!!!!!! They will walk you through a fit. Two types of RGP fittings Standard Fitting Guilds Empirically Fitting RGP Lid Attachment This is where the contact is tucked under the top lid Usually the ideal fit Apical Clearance This is where the lens floats in between the lids Pops out easier! Try lenses on! Start with lens at flat k or slightly steeper Try on until the lens centers well, moves with the blink, slide on cornea when patient looks sideto-side, and there is a nice tear exchange Once you have a lenses that sits well, over refract 1. Call lab and give Ks and Refraction (minus cyl) 2. Take ks and calculate corneal cyl 3. Determine diameter based on HVID- go smaller 4. The more corneal cyl the steeper from the flat K to determine the base curve. 5. The larger diameter you chose the flatter. 6. Always work off the flat K 7. Always work in cyl and pretty much ignore the cyl power Example Ks 44.00/44.50@90 RX X180 Corneal cyl = 0.50 HVID 11.2 Diam (on flat K) Power same Ks 47.00/49.00@90 Rx @180 Corneal cyl go slightly steeper than flat k try The lens ordered is 1 diopter steeper than flat K so you need to add to the cyl power 6

7 Problem solving RGP (call for help!) Lens rides low = too steep Lens rides high = too flat Lens rides temporal or nasal Probably against the rule cyl = try toric Remember SAMFAP Steep add MINUS/Flat add PLUS Example: base curve power Too much pool centrally = too steep Base curve flatten 0.50 = New power would be because it was flattened No stain centrally = too flat steepen 0.50 = Changing the Diameter RGP Changing the diameter of an RGP (or soft) will affect the fitting. If you make the Diameter larger, it will make the lens tighter (soft or RGP). In an RGP it will also make the lens steeper. If you make the Diameter smaller, it will make the lens looser. In the case of an RGP it will make the lens flatter. When changing the diameter of an RGP it will affect the was the base curve fits. For every 0.3mm you change the diameter, the base will fit 0.25diopters differently. Changing Diameter of RPG Original lens is dia 9.8 You want to make the lens 10.5 (.6mm larger) it will make BC relation to the cornea 0.50 steeper. If you want a steeper lens that is fine, but if you wanted to keep the original BC you would need to flatten the lens by = (don t forget SAMFAP) You flattened the BC, change the power -1.50! Making the lens Smaller (RGP) If you make the lens small, you change the relationship of the BC to cornea to flatter. Change the dia to 9.2 You will need to steepen the lens and don t for get SAMFAP Dia change to 9.2 =0.60mm Making lens smaller, need to steepen the BC 0.25 Diopters for every 0.3mm BC = Steepened the lens, need to add more minus = -2.50???????????????????????????????????????? 7

8 Example of how the diameter changes the BC relationship. All three of these images is the exact same BC of This also illustrates how the HVID affects the fitting of a contact. All three of these are corneas with K readings of Similar to soft insertion except the lens must be applied directly to the cornea. Sometimes easier not to use a mirror RGP Inserting RGP Removal Blink Method Place index finger along side of eye Open wide Pull lids tight with index finger Blink hard Catch in other hand RGP Removal 2finger or 2 hands RGP Removal Solutions Soft Lenses This method uses either two fingers of both hands to use the lids to pop the lenses out You pull open the lids to the outside of the lens and then try to push them under the lens to wedge it out Removing an RGP lens take can be tricky. I like to instruct on how to use the plunger and always give one to my patient. I make sure they can safely use it before I let them leave the office with one. Multipurpose Clean Rinse Soak with one solution. Easy and Safe Does not kill all bugs Tendency not to do correctly. Lenses should be rubbed or rinsed for 5 seconds.does that really happen Allergies to solution and preservatives in solution Not all solutions compatible with all contact lens material Hydrogen Peroxide Easy Safe Best cleaner No solution sensitivity Can be used with all contact lenses Painful if not done right! Or if accidentally put in eye! Requires more thought and soak time 8

9 Cleaning and Storing RGP Cleaner Conditioner Multipurpose No water on soft or RGP!!!!! Hydrogen Peroxide for RGP! Insert Wash & dry hands Check inside out (soft) Put lens in Wearing schedule, varies by type of lens, usually a build up period No water no swim no sleep If they have pain, take lenses out and call office Makeup is applied after insertion Insert and Removal instructions Removal Wash & dry hands Take lenses out Clean and store If you fit single use lenses this is a lot easier! Contact Lens Precautions No matter soft or RGP you need to advise the patient of proper handling and care, manufacturer's recommended wearing time and replacement schedule, and infection precautions. No overnight wear or swimming/water activities. A wearing schedule is recommended for all new wearers, a new soft lens wearer will adapt quickly, while a new RGP wearer could take 4-5 weeks to work up to full time. Follow up! After fitting lenses, the patient will need to be seen for a follow up appointment to make sure the lenses are fitting correctly and the patient has been following the instructions given Lenses 1st recheck 2nd recheck third single use soft 1 week only if changes made Annually/biannually two weeks disposables 1-2 weeks only if changes made Annually/biannually monthly disposables 3-4 weeks only if changes made Annually/biannually RGP 1-3 weeks monthly only if changes made Annually/biannually Cobalt Filter Blue pen light Tyler s Quarterly HVID Vertex chart Diopter to K conversion chart Tools of the Trade Radioscope The Radioscope measures in millimeters (mm) Keratometry readings are in Diopters mm to Diopter conversion factor 337.5/mm=Diopter 337.5/Diopter = mm K readings are /44.50 = 7.58 the reading in the radioscope Lens reads to 6.68 in the radioscope the Ks would be? 337.5/6.68= Extendended wear after 1st overnight One week of sleeping One month as needed/annually 9

10 Start with the machine up and find the star (look to the left and see a ruler). Place star in center of view by moving the tray. Move the devise down, see a spring, then another star. How to use the radioscope Place a few drops of saline in the well and place the dry contact on the saline Start with the machine up and find the star (look to the left and see a ruler) You will see a line by the ruler, once the second star is in focus, line it to zero Move back up, past the spring, to the star. Look at the # the line is on and that is your Base curve! The slide gauge is easy to use. You drop the contact lens into the top, hold at an angle, and let the lens slide down. Once it stops, don t push it, the number to the right is the diameter. This lens is a 10.1mm Diameter Gauge Don t be afraid of Contacts Advanced Stuff Questions? Hybrid lenses Scleral Keratoconus Transplants Scars Prosthetics Pediatrics Bandage Contact lenses can be life changing for some people You could really make the blind see with some contact lenses all you have to do is try them on! Minnesota Contact Lens Society Fall and Spring symposiums National Contact Lens Society of America Conference usually in fall, on-line learning 10