GP Lens Case Grand Rounds Troubleshooting Guide – 47

Post-Refractive Surgery (not-LASIK): Robert Maynard, OD

Background

This 35-year-old engineer originally presented to my office in 1996. He was a post-Radial Keratotomy patient who also had five enhancements. He had a total of 9 RK cuts per eye, as well as T-cuts 360 degrees in both eyes. The RK cuts extended into the pupillary zone. He is concerned about his vision, not only for his occupation, but due to the fact that he also plays serious amateur baseball.

Test Procedures, Fitting/Refitting, Design & Ordering

Visual Acuities (without Correction):

OD: 20/40-2 (slow response)
OS: 20/25-2 (slow response)

Manifest Refraction:

OD: +1.75 – 2.25 x 100 20/25+ (ghosts and shadows)
OS: +0.75 -1.25 x 095 20/20-2 (ghosts and shadows)

Keratometry:

OD: 35.75 @ 018; 34.12 @ 108
OS: 35.25 @ 017; 32.87 @ 107

We initially trial fit him with two pair of Contex OK 60 lenses from our diagnostic fitting sets.

Initial Fit:

Lens parameters:

Lens TypePower(D)BCR(mm)OAD(mm)

OD: Contex OK 5A -5.00 8.60 10.50
OS: Contex OK 5A -4.75 8.70 10.50

Over-Refraction/Visual Acuities:

OD: -0.50DS 20/30-1
OS: Plano 20/25

Slit Lamp Examination:

OD: The right lens positioned temporal with excessive movement, tending to drop down to the lower lid. With fluorescein, there was a small central bubble with scattered dimple veiling and excessive clearance around the outer one-third of the lens.

OS: The left lens decenters nasally and inferiorly and also rests on the lower lid. With fluorescein, there were small bubbles both superior and central with mild bearing at about 8:00 near the pupil. Excessive fluorescein was present around the outer one-third of the lens.

Two Week Follow-Up Visit:

At the two week follow-up visit, the patient complained that his vision was not “crisp” and he experienced much glare at night.

Visual Acuity:

OD: 20/25
OS: 20/25+2

Keratometry:

OD: 35.87 @ 140; 37.87 @ 050
OS: 35.62 @ 100; 37.25 @ 010

Slit Lamp Examination:

The slit lamp evaluation was very previous to the initial visit; however, dimple veiling accompanied by excessive clearance was present centrally OU. Both lenses were positioning temporally with the left lens exhibiting greater lateral decentration. Figure 1a shows the fitting relationship of the right lens; Figure 1b shows the left lens.


Figure 1a


Figure 1b

Second Fit:

Lens parameters:

Lens TypePower(D)BCR(mm)OAD(mm)

OD: Contex OK 604 -6.00 8.40 10.50
OS: Contex OK 605 -5.75 8.50 10.50

Visual Acuity:

OD: 20/25-1
OS: 20/20-2

Slit Lamp Evaluation:

OD: The right lens centered fairly well although slightly temporal and exhibited good movement. With fluorescein, apical clearance with a small bubble was present.

OS: The left lens decentered temporally and inferiorly with the blink. It also exhibited apical clearance and a small central bubble.

One Month Follow-Up Visit:

Over-Refraction/Visual Acuities:

OD: Plano 20/25
OS: Plano 20/30-1

Slit Lamp Evaluation:

OD: The right lens decentered inferiorly with some slight dimple veil in the central apical clearance area (Figure 2a).

OS: The left lens decentered inferiorly and contacted the lower lid. Apical clearance and excessive dimple veiling was present which changed to a large bubble when the lens was manually centered. Good movement was present with the blink (Figure 2b).


Figure 2a


Figure 2b

Third Fit:

Lens TypePower(D)BCR(mm)OAD(mm)

OD: Contex OK 603 -4.00 8.60 10.60
OS: Contex OK 603 -4.50 8.80 10.60

Over-Refraction/Visual Acuities:

OD: Plano 20/20 (slow)
OS: Plano 20/25 (slow)

Slit Lamp Evaluation:

OD: The right lens decentered slightly superiorly and overlapped the superior limbus. With fluorescein, very slight intermediate touch, good edge clearance and an absence of dimple veiling was noted (Figure 3a).

OS: The left lens exhibited good movement with the blink and decentered slightly superior. With fluorescein, it resulted in very mild central bearing, some inferior clearance and no dimple veiling (Figure 3b).


Figure 3a


Figure 3b

Follow-Up Care/Final Outcome

Although this patient was instructed to return in two weeks, he did not return for 18 months, despite repeated requests. He has a history of non-compliance, which makes fitting him even more challenging.

Final Fit:

We recently examined this patient and decided to change the lens parameters.

Manifest Refraction:

OD: +1.50 -2.00 x 126 20/25-1
OS: +1.00 -2.25 x 137 20/20-1

Keratometry:

OD: 36.50 @ 161; 40.00 @ 071
OS: 35.50 @ 148; 36.50 @ 058

Corneal Topography:


Figure 4

Power(D)BCR(mm)OAD/OZD(mm)Cap Size(mm)SCR/W(mm)PCR/W(mm)

OD: -4.00 8.54 11.50/9.10 8.90 8.75/.5 10.80/.5
OS: -4.50 8.44 11.50/9.10 8.90 8.75/.5 10.80/.5

Heavy Blend OU

Over-Refraction/Visual Acuities:

OD: Plano 20/25-1
OS: Plano 20/20

Slit Lamp Evaluation:

OD: The right lens decentered superiorly and slightly temporal over the superior limbus. With fluorescein, apical clearance and slight intermediate bearing was present. (Figure 5a)

OS: The left lens decentered superiorly to the limbus with greater temporal decentration than the right lens. Good tear exchange was present with the blink.(Figure 5b)


Figure 5a


Figure 5b

The patient has been released for the next six months. We explained why we could not make the OD see as well. The RK cuts impinge further into his pupillary zone than on his OS. Other than wishing he had a “crisp” 20/20 vision, he is relatively happy with the VA and comfort.

Discussion/Alternative Management Options

Post-refractive surgery patients, notably post-RK, can be extremely challenging. This case was made more complicated by the series of enhancements which extended into the pupillary zone. This patient, as with so many post-refractive surgery patients, has difficulty understanding why their uncorrected vision is not satisfactory and then achieving excellent corrected, if possible, can only occur with GP lenses and often after multiple refits. Patience is, therefore, quite a virtue for the contact lens practitioner fitting this type of patient.

Reverse geometry lenses, such as the SurgiLens from Con-Cise, are almost always indicated in these cases. Corneal topography information, however, is invaluable in determining the type of the design and the amount of secondary curve steepening relative to the base curve radius. This patient was successful in a reverse geometry lens design for several years prior to being refit into a more conventional design in the final fit.

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