Progressive multifocal lenses have been put into the market since 1959. After nearly half a century of continuous improvement and perfection, they have formed two design trends: soft and hard. The main difference between the two designs is the length of the progressive channel. Hard-designed progressive films have short progressive channels and relatively few peripheral aberrations. In order to ensure the field of view at all distances, they need smaller vertical dimensions. For example, the juvenile progressive film belongs to this kind of design, but because of its short progressive channel and too fast progressive process, this design is relatively difficult to adapt to the elderly. Soft-designed progressive films have relatively long gradient channels and large peripheral aberrations, but because of their long gradient channels and gentle gradient process, they are easy for the wearer to adapt and become the mainstream of progressive films in the market.

In recent years, with the continuous development of glasses technology and the improvement of people's living standards and quality, progressive multifocal lenses are increasingly welcomed by teenagers and middle-aged and elderly refractive customers. However, due to the limitation of optometry technology, people's understanding and popularization rate are still very low. This paper introduces the fitting of progressive multifocal lenses.

Design principle and characteristics of progressive multifocal lens

The design principle of progressive multifocal lenses is to produce continuous far, medium and near vision on one lens. The characteristic figure 1 shows that the upper part is far diopter, the lower part of the lens is near diopter, and the center of the lens is a diopter gradient area. The near-zone optical center of most progressive lenses is below the far-zone optical center 10- 16mm, and the nose is 2-2.5 mm. The two sides of the progressive zone are aberration zones. When the line of sight moves to this zone, the object will be deformed, and the degree of deformation is related to the design and addition of the progressive film.

Choose the right wearer

It is very important to choose customers who are suitable for wearing progressive lenses: ① people over 45 years old who want to see long-distance, medium-distance and short-distance continuous vision; Young students control and prevent myopia; ③ The refractive power is between 6.00 and 2.00 degrees; ④ For those who have just entered presbyopia, it is best to wear it for those with low diopter. But if: ① vertical anisometropia >; 2.00d ② Astigmatism >; 2.00 d ③ Those who need far, middle and near vision ④ Wear bifocal lenses and trifocal lenses. If you feel good, you should be more careful than when customers need to wear them.

Optometry of progressive multifocal lenses

The process of progressive multifocal optometry is not much different from ordinary lenses, and it is also divided into three stages. Let's briefly talk about the process:

3. 1 correction of hyperopia diopter

Initial stage ① Consultation ② General eye examination ③ Naked vision, diopter of old lenses, corrected vision examination ④ Computer optometry ⑤ Shadow examination.

Fine-tuning stage ① Two-color test ② astigmatism table and cross cylinder mirror inspection.

In the final stage, ① examination of dominant eyes ② binocular balance and equal vision function.

3.2 Near diopter examination

① Cross-grid method:

Put 0.50DC in front of your eyes, the negative axis of the cross cylindrical lens is 900, and the positive axis is 1800.

Or if it appears, it is not added.

Add add until the horizontal line is as clear as the vertical line.

② Empirical method: (age -30)×0. 1=ADD.

For teenagers, ADD is generally+1.50ds.

Selection of spectacle frame and measurement of pupil distance and pupil height

Select 4. 1 frame.

For the selection of spectacle frames, the point from the pupil center to the inner edge of the lower frame of spectacle frames is generally not less than 22mm. For the standard channel, 18mm.

Or the frame height of 19mm should be ≥34mm, and the frame height of 13.5 or 14mm with short slots should be ≥30mm. Also, avoid choosing a frame with a large oblique angle on the nose, because it is easy to "cut off" the reading area, and try not to choose a frameless frame, because it is easy to loosen and change various parameters. In addition, be sure to choose a frame with an adjustable nose pad.

4.2 Measurement of Pupil Distance

For pupillary distance, we need to measure the pupillary distance of the left and right eyes separately (because many people's noses are not necessarily located in the center of the eyes), and the pupillary distance should be accurate to 0.5 mm The measurement methods are: pupillary distance meter, pupillary distance ruler, marking with samples, and measuring with progressive lens measuring card, which is the same as ordinary glasses, so it is not introduced.

4.3 Measurement of Pupil Height

Pupil height refers to the vertical distance from the center of the pupil to the inner edge of the lower frame of the lens frame. There are two ways:

4.3. 1 sample marking method

Before measurement, the mirror frame must be adjusted and calibrated to achieve the best balance. General eye distance 12- 13mm, forward tilt angle 100- 120, and appropriate temple length.

(1) The invigilator and the examinee sit opposite each other and keep the same level of sight.

② The inspector holds a marker pen in his right hand, closes his right eye, opens his left eye, and puts a pen flashlight in his left hand under the lower eyelid of the left eye for the inspector to see his left eye. According to the reflection of the pupil center of the examinee, the pupil distance is marked on the glasses sample with a reticle, and the vertical distance from the intersection point of the reticle to the lower inner edge of the frame is the pupil height of the examinee's right eye.

③ The inspector holds a marker in his right hand, closes his left eye and opens his right eye, and puts a pen flashlight in his left hand under the lower eyelid of the right eye for the inspector to see the right eye. According to the reflection of the pupil center of the examinee, the pupil distance is marked on the glasses sample with a reticle, and the vertical distance from the intersection point of the reticle to the lower inner edge of the frame is the pupil height of the examinee's left eye.

Formula method

H=(a-34)/2+22 h= pupil height a= vertical height of spectacle frame.

Correction value: long channel H plus 1-2mm short channel H minus1mm.

More than 40mm plus1-2mm

Processing and Assembly of Progressive Multifocal Lens

5. 1 identification mark

① Horizontal reference line: temporary mark, installed as the horizontal line of the lens, to check whether the astigmatism axis position of the lens is correct.

② Invisible permanent marking: used to restore temporary marking, and the distance between two points is 34 mm..

③ Ranging area: detect the distance of the lens.

④ Near-use measurement area: detect the near-use luminosity and ADD of the lens.

⑤ Eyeglasses cross mark: corresponding to the pupil height of glasses. Generally 2mm above the prism reference point.

⑥ Add mark: the light added by the lens.

⑦ Prism datum point: 2/3 of ADD.

5.2 detection lens

① Eye classification and surface quality of lens.

② Distance and near power of the lens.

③ Add mark

(4) Check whether the horizontal datum line and the permanent invisible sign meet the requirements, and re-mark the ones that do not meet the requirements according to the invisible sign.

5.3 Processing and Assembly

Edge grinder with automatic scanner

① Scan the sample or frame directly to the machine.

② Input the pupil distance and pupil height directly on the machine to complete the automatic center shifting.

(3) Align the crosshair of the progressive film with the well-intentioned intersection on the screen and keep it horizontal.

(4) put it into a machine for edge grinding and assembly.

5.3.2 Edge grinding machine requiring template

(1) Displays the sample template.

② Measure the pupil height according to the scale line on the template and mark the pupil height line.

③ Fix the template on the locating hole of the central instrument.

(4) Cover the progressive membrane on the template, merge the reticle and pupil height line, and move horizontally.

⑤ Invisible marks must be on the same horizontal line.

⑥ Put it into the machine for edging and assembly.

Wear and guidance of progressive multifocal lenses

① Perform routine plastic surgery and adjustment for customers, so that the reticle is aligned with the center of the pupil.

(2) Check the near and far vision. If it is correct, wipe off the temporary mark with alcohol or acetone.

(3) When using the far zone, let the customer see the distant target, then slowly lift the chin eyeball after seeing it clearly, and don't shift the degree change it has experienced downward, which means that it is seen through the progressive zone.

(4) When using the near-use area, let him turn to look at the nearby words, keep his eyes still, and tell the customer that he can only read but not browse the articles (generally within the range of 3.5cm×5cm).

⑤ Look at the far, middle and near alternately, let them look at the far, middle and near through the rotation of their eyes, and practice looking for the far, gradual and near areas.

⑥ Let it look at the image deformation area through the left and right rotation of the eyeball, let it pay attention to the existence of the image deformation area, and tell customers to look at the left and right objects through the rotation of the head, not through the rotation of the eyeball.

⑦ Let him go, feel the deformation of the progressive film, and tell the customer to keep his head down when looking closely. Try to look ahead 1 meter.

⑧ Tell the customer that the progressive film has an adaptation period of 65,438+0 to 2 weeks, and the adaptation period should be practiced step by step according to the steps of "static before moving, internal before external".

7. Causes and treatment of discomfort of progressive multifocal lenses

For customers who still can't adapt after the adaptation period, we must first:

① According to the invisible permanent marks, use the progressive film measuring card to restore the temporary marks.

② Check the near and far diopter and additional power of the lens, and check the prescription.

③ Check the assembly quality.

④ Observe the effect of the wearer and find out the problem.

Generally speaking, the maladjustment is manifested as: the reading area is too narrow, the near and far vision is blurred, dizziness, shaking, distorted vision, and you need to turn your eyes or tilt your head to see the object clearly. For these discomforts, we have to ask the customer about the original diopter, original glasses and eye needs. We should mainly consider and analyze the diopter of the lenses we wear, the parameters of the glasses and the situation of the frames. Please refer to the following table:

Causes and treatment of discomfort in wearing

Possible causes of discomfort

job operation

Hyperopia blur ① If the glasses are too high, adjust the nose pad.

② Incorrect prescription: too many positive degrees; Too few negative degrees; Astigmatism is inaccurate

Refraction

Myopia blur ① The height of glasses is too small ② The distance between glasses and eyes is too large. Adjust the nose pad.

③ Incorrect prescription: Incorrect recent addition; The diopter of hyperopia is incorrect.

Refraction

(4) The pupillary distance is inaccurate.

⑤ The vertical inclination is not enough to adjust the nose pad or temples.

⑥ Adjust the radian of the mirror frame according to the radian of the mirror base.

Seeing far away makes me dizzy.

① The distance between mirror eyes is too large; 2 does not meet the face shape; ③ The vertical inclination is not enough; ④ The glasses are too high.

Nasal adjustment bracket or temple

⑤ If the distance between pupils and visual distance is not accurate, please reorder.

The reading area is too small (the head moves sideways excessively when reading) ① The height is too high.

Refraction

(2) The pupillary distance is inaccurate.

③ The height of glasses is too low; ④ The distance between glasses and eyes is too large; 5 does not conform to the face shape; ⑤ The vertical inclination is not enough.

Nasal adjustment bracket or temple

⑦ Adjust the radian of the mirror frame according to the radian of the mirror base.

From a distance, the prescription for tilting the back of the head is inaccurate: too many negative degrees or too few positive degrees.

Refraction

Head backward in fancy/close range ① The prescription is inaccurate: the positive degree is too little.

Refraction

② The height of glasses is too low: adjust the nose rest.

When the head leans forward, the glasses are too high: adjust the nose pad.

The prescription for leaning forward when watching closely is inaccurate: there are too many positive degrees.

Refraction

As can be seen from the above fitting process, fitting progressive addition lenses is actually not as difficult as we thought. As long as we follow the principles of material selection, quasi-high beam, near barefoot, precise measurement, fine processing and full accounting, I believe everyone can match a pair of qualified and comfortable progressive multifocal lenses.