GP Lens Case Grand Rounds Troubleshooting Guide – 52

Moderate Myopia (≥ 3.0D): Robert L. Davis, OD

Background

PJ is a 44-year-old policeman who has been wearing soft lenses since December 1980. Initially he wore CSI daily wear reusable lenses without complication although since March 1991 PJ was refit to disposable lenses because of comfort and the convenience of having new lenses applied every two weeks. PJ wears his lenses continuously for six days and nights routinely and removes them to disinfect with Optifree. PJ has experienced a visual and convenience advantage in his job wearing two week disposable lenses. At his last annual visit PJ commented that the disposable lenses have been the best investment I have made, and the only scenario that would improve my correction would not to wear any lens at all.

I explained to PJ that another correcting modality could satisfy his visual goal of not wearing any lens during the day although he would have to wear a lens while he was sleeping. The name of the procedure was orthokeratology. I explained that one of the reasons for his myopia was that his cornea shape was steep which creates a myopic prescription. I further explained if we flattened the cornea with a contact lens equal to the amount of his myopia we could neutralize his myopia and he would have no correction resulting in the same vision as his contact lens without wearing any lens during the day. These special designed lenses would have to be worn each night to flatten his cornea although during his waking hours no lens would have to be worn.

PJ was very interested in the procedure and wanted to have an examination to find out if he was a good candidate for the orthokeratology procedure. I gave him some background literature about reverse geometry lenses and a pamphlet explaining orthokeratology.

PJ was on no medications nor had any allergies. He had no significant ocular history or family ocular history. PJ reported he had no family history of diabetes, hypertension, glaucoma or macular degeneration. PJ commented that he has been waiting for the day that he could wake up and no longer require a correction for his nearsightedness. His last eye examination was one year ago and a progress check was done three months ago.

Entrance Visual Acuity with Current Spectacles at Distance:

OD: -3.25 -1.25 X 180 20/20
OS: -4.00 -0.50 X 180 20/20

Near Visual Acuity Without Correction:

OD: 20/20
OS: 20/20

Uncorrected Visual Acuity at Distance:

OD: 20/200
OS: 20/300
OU: 20/200

Pupillary responses were equal, round and reactive to light and accommodation with no afferent pupillary defect. In normal room illumination, pupil size was 3.6 mm OD and 3.4 OS. In dim illumination pupil size was 4.5 mm OD and 4.4 OS. As measure by the Neuroptic pupilometer. Versions were smooth and full OU.

Cover test with current spectacle correction was 2 exophoric at distance and 4 exophoric at near.

Automatic visual field testing showed full and complete fields without relative or absolute scotomas.

Manifest Refraction Was as Follows:

OD: -3.00 DS 20/15
OS: -1.50 DS 20/15

NRA and PRA findings were +2.50 and -2.75 respectively.

Slit lamp examination of both eyes revealed no abnormalities, no cornea or conjunctival fluorescein staining and no apparent tear film deficiency. Lids, lashes, bulbar and palpebral conjunctiva, cornea, iris, lens and anterior chamber were all normal for both eyes. Lid eversion illustrated smooth and satin tarsal conjunctiva.

Keratometry Readings:

OD: 45.75 @ 180, 47.75 @ 090 with no distortion
OS: 45.37 @ 180, 46.87 @ 090 with slight molding

Goldmann Applanation Tonometry Was as Follows:

OD: 11 mmHg
OS: 12 mmHg @ 6:30 PM

Specular Microscopy Was as Follows:

OD: 3226
OS: 3314
No evidence of polymegathism or pleomorphism

A dilated retinal fundus examination with 1gtt 1% Tropicamide was performed. For both the right and left eye the C:D was .3, the maculae were flat with a bright reflex, the retinal vessels had normal course and caliber and both periphery were flat and intact.

Test Procedures, Fitting/Refitting, Lens Design, Ordering, Patient Consultation and Education

At the conclusion of the eye examination it was explained to PJ that the two important factors that determine the candidacy for orthokeratology includes the curvature of the eye and the prescription. If the corneal curvature was too flat for the prescription then the procedure could not neutralize the total refractive error. If the prescription was too high in relationship to the corneal curvature then the procedure would not neutralize the total prescription. After evaluating both the corneal curvature and the prescription JP was told he would make a good candidate.

PJ asked how do we proceed and what are the scheduled follow-up appointments. It was explained that the lenses would be ordered and a dispensing visit would be scheduled in about one week. After the first night of wearing the lenses PJ would be expected to be seen in the office to monitor the first night progress of the Ortho-k procedure. Normally the appointment schedule would include dispensing, one night, one week, two weeks, one month, three months, six months and one year. If their was any adverse reaction of if the procedure did not go as expected then additional office visits would sort out the difficulties. At the one day visit if all the nearsightedness was not neutralized by the procedure then soft disposable lenses would be used to correct the remaining prescription.

The cost of the lenses and all the visits for one year was included in the global fee. If additional Ortho-K lenses would be needed in a modified design the existing lenses would be exchanged at no cost. The refund schedule was also explained to PJ. Our initial goal was to neutralize the total prescription so no lens would have to be worn during his waking hours. The bulk of the follow-up visits would attempt to configure the lenses so that lenses could be worn every other night. PJ understood all the information that was given to him. Also a newsletter was given to him explaining the procedure as well as a CRT pamphlet and a VST pamphlet. PJ was a good candidate for overnight orthokeratology based on his refractive error, corneal curvature, good corneal health, minimal corneal cylinder, average pupil size, and good motivation and adequate visual expectations.

Lens Dispensing:

PJ returned to the office for the orthokeratology dispensing visit a week later. Entrance visual acuity with current spectacles at distance was 20/20 OD and OS. PJ was wearing his glasses and was told after tonight the glasses would no longer perform adequately because the prescription would be too strong. The slit lamp examination was unremarkable.

Topography was performed on both eyes with simulated keratometry (SimK) values:
OD: 45.50 @ 180, 47.25 @ 090
OS: 45.25 @ 180, 46.75 @ 090

Slit lamp examination revealed no abnormalities, no cornea or conjunctival staining for both eyes. Lids, lashes, bulbar and palpebral conjunctiva, cornea, iris, lens and anterior chamber were all normal for both eyes.

The design of the treatment lenses were derived from the corneal curvature, refractive error, corneal eccentricity and sagittal height. The flat sim K value of OD 45.75 and OS 45.37 and the spherical component of the refraction -3.25 OD and OS -4.00 required a base curve selection of OD 8.08 and OS 8.31. The base curve is fit flatter than flat K in the amount to neutralize the patient’s prescription with an added 0.75 compression factor. As the contact lens compresses the tissue down centrally the reverse curve allows the corneal tissue to reform into the space created by the contact lens/corneal sagittal height. The reverse curve is determined by the neutralizing prescription, corneal eccentricity, horizontal visible iris diameter and corneal curvature. The flat contact lens base curve eventually will lift off the cornea requiring the reverse curve to help bring the contact lens back to the corneal surface to receive the alignment curve. The alignment curve centers the lens and prepares the cornea/contact lens relationship to position parallel onto the corneal surface. This alignment curve locks down the contact lens on to the cornea surface. The peripheral curve
is designed to receive tears to float the contact lens and for tear exchange. The lens diameter is usually between 10.0 and 11.0 for good lens centration and the optic zone is 6.0 mm.

OD:
Base Curve (BC) 8.08 mm
Reverse Curve 6.41/.6
Alignment Curve 745/1.0
Peripheral Curve 11.00/.4
Lens Thickness 0.19
Overall diameter (OAD) 10.0 mm
Optic zone diameter (OZD) 6.0 mm
Power +0.75
Boston XO Blue

OS:
Base Curve 8.31 mm
Reverse Curve 631/.6
Alignment Curve 744/1.0
Peripheral Curve 11.00/.4
Lens Thickness 0.19
OAD 10.0 mm
OZD 6.0 mm
Power +0.75
Boston XO Blue

The contact lenses were applied and allowed to settle. PJ was comfortable with the lenses so no anesthetic was instilled. The lenses centered well and fluorescein was instilled to view the tears underneath the lens. The lenses exhibited a donut shaped pattern with adequate central compression, good paracentral clearance, mid-peripheral alignment, and peripheral edge lift.

Visual acuity with the contact lens on the eye resulted in 20/20 OD and OS.

PJ demonstrated he could apply and removal the lenses. A sample of AMO Claris cleaning, disinfection and wetting solution was given and proper lens care and storage were discussed. I also advised a daily drop of SupraClens to ensure adequate protein removal and Miraflow surfactant for nightly lens cleaning. The patient was also instructed to fill to concave side with Refresh Liquigel.

PJ was instructed to wear the lenses overnight and return to the office in the morning for an appointment the next day. He was also educated on the use of rewetting drops. Prior to leaving the office PJ demonstrated the proper cleaning and disinfection of the lenses and went home wearing a fresh pair of disposable lenses.

Follow-Up Care/Final Outcome

One Day After Lens Dispensing:

PJ had removed the lenses prior to arriving to the office. He had worn the lenses seven hours during the night. PJ was amazed that his vision for the first time since he could remember was clear enough to drive comfortably to the office without wearing any visual correction. Current lens parameters:

OD:
Base Curve (BC) 8.08 mm
Reverse Curve 6.41/.6
Alignment Curve 745/1.0
Peripheral Curve 11.00/.4
Lens Thickness 0.19
Overall diameter (OAD) 10.0 mm
Optic zone diameter (OZD) 6.0 mm
Power +0.75
Boston XO Blue

OS:
Base Curve 8.31 mm
Reverse Curve 631/.6
Alignment Curve 744/1.0
Peripheral Curve 11.00/.4
Lens Thickness 0.19
OAD 10.0 mm
OZD 6.0 mm
Power +0.75
Boston XO Blue

Entrance visual acuity was 20/25 OD and 20/20 OS.

Topography was performed with simulated keratometry (SimK) values:

OD: 44.75 at 180, 46.50 at 090
OS: 44.12 at 180, 46.12 at 090

Refraction was -1.00 OD and -0.75 OS with 20/20 acuity.

Slit lamp examination of both eyes revealed grade 1 punctate staining and no conjunctival staining. No hyperemia was noted and PJ experienced slight drying of the eyes. Lids, lashes, bulbar and palpebral conjunctiva, cornea, iris, lens and anterior chamber were all normal for both eyes.

Lenses were applied and the fluorescein evaluation of the lenses revealed good centration, an adequate central zone of touch of about 4 mm, adequate paracentral clearance, good mid-peripheral alignment, and adequate peripheral edge lift OU.

Topography showed a central compression of the cornea with a slightly inferior displaced bulls eye pattern. The typical topographic pattern was starting to be defined and a clearing of the astigmatic bow tie configuration start to take on the typical bulls eye pattern. The paracentral area exhibited a sharp steepening zone flattening out to the periphery.

PJ was instructed to schedule a follow-up appointment in one week and to bring the lenses in at each appointment for modification or polishing if needed. He was advised to wear the lenses each night with morning removal and daily morning cleaning with Miraflow. PJ was dispensed a pair of disposable lenses in the resultant over correction lens power. OD -1.00 OS -0.75 JP was also instructed that the disposable lenses would only need to be worn for a day or two dependent on the acuity when the reverse geometry lenses were removed in the morning. He was also advised if the vision was inadequate during the next five days to schedule an appointment earlier than one week.

One Week After Lens Dispensing:

PJ returned for an office visit without wearing any visual correction. PJ explained that after the second day he no longer needed a visual correction with the soft lenses during the day. PJ did experience a slight blurring around 9:00 PM at night. PJ was on vacation the next few weeks and would be wearing the lenses approximately seven hours at night. During the day his vision was clear and experienced some halos at night while driving. He was amazed that he no longer needed a visual correction any more during the day without undergoing a risky surgical procedure. PJ explained that he worked the eleven to seven shift and hoped the halos and flare would be eliminated with increased wearing time. He was happy with the progress of the procedure.

Entrance visual acuity was 20/20-1 OD and 20/20-1 OS. The sphere-cylinder over-refraction was +0.50 OD and +0.50 with 20/20 acuity OD and OS.

Topography was performed with simulated keratometry (SimK) values:

OD: 43.25 @ 180, 44.50 @ 090
OS: 43.00 @ 180, 44.00 @ 090

Fluorescein evaluation of the lenses revealed good centration, 4.0 mm central zone of touch OD and 4.0 mm central zone of touch OS, good paracentral clearance OD without air bubbles, adequate paracentral clearance OS, good mid-peripheral alignment OU, and adequate peripheral edge lift OU. Both lenses decentered slightly temporal.

A one month appointment was scheduled. He was advised to wear the lenses every night until the next office visit.

One Month After Lens Dispensing:

PJ had no visual acuity complaints although did notice some flare and halos at night. We discussed the cause of the problem related to the pupils dilating at night larger than the treatment zone. Dependent on how much the flare and halos at night bothered him we could investigate some solutions to the problem. I could increase the treatment zone and reconfigure the lens to make it an 11.0mm diameter lens which would give us the ability to increase the central compression zone. We could also use one drop of Alphagan at dusk which would control the pupil dilation.

Entrance visual with no correction was 20/20 OU with a refraction of +0.50 DS OD and OS.

Slit lamp examination of both eyes revealed no abnormalities, no cornea or conjunctiva stain. Lids, lashes, bulbar and palpebral conjunctiva, cornea, iris, lens and anterior chamber were all normal for both eyes.

Topography revealed that the treatment zone was centered slightly temporal and full removal of the refractive prescription had occurred in both eyes from baseline. It was decided that PJ would wear his lenses during sleep due to the importance of the visual acuity during his job. PJ also decided that he would first try a drop of alphagan before going on duty at night to remove the flare and halos that he experienced. If the alphagan did not adequately remove the visual problems at night then he should call for a follow-up appointment in one week. If the alphagan satisfied his visual expectations then a return visit would be scheduled in 3 months.

Three Months After Lens Dispensing:

PJ had no complaints and the alphagan had removed all the visual distortions at night. PJ was happy with the visual outcome and during his next vacation he would attempt a larger lens so he would not have to instill the drops at night. At the present time PJ was comfortable with the procedure and did not want to take the chance of a new lens design while he was working.

Entrance visual with no correction was 20/20 OD and OS with a refraction of +0.50 OD and +0.50 OS.

Slit lamp examination of both eyes revealed no abnormalities, no cornea or conjunctiva staining. Lids, lashes, bulbar and palpebral conjunctiva, cornea, iris, lens and anterior chamber were normal.

Topography revealed the treatment zone was slightly decentered temporal. Difference maps comparing baseline to 3 months of treatment showed a power change of -3.50 D OD and -4.00 D OS.

Topography was performed with simulated keratometry (SimK) values:

OD: 43.00 @ 180, 44.50 @ 090
OS: 42.75 @ 180, 43.75 @ 090

Discussion/Alternative Management Options

This case illustrates the management of a patient wearing soft lens whose goal is to not wear contacts or glasses while on the job being a policeman. The most difficult part of fitting orthokeratology is having the confidence to match the patient’s expectations when you don’t exactly know how the cornea is going to respond from the flattening effects of the contact lens. The initial visit will determine the topography, sim K and the prescription to evaluate the level of expected success. A patient with limbal to limbal astigmatism is one criterion that must be evaluated that will hinder the level of success. Patients with large pupils can be expected to suffer from halos and glare at night.

Approaching a case predicting the patient’s problems prior to experiencing the adverse reaction creates patient confidence and strategy for remediation. Halos and glare can be managed by either increasing the treatment zone or reducing the dilation effects under reduced illumination. Alphagan is a selective alpha 2 agonist that has a significant effect on decreasing pupil size under scotopic conditions. McDonald (2001) investigated the effects of Alphagan and found a decrease in pupil size within thirty minutes that lasted at least four hours. This indicates that the preparation can decrease night-vision difficulties such as halos, star bursts, glare, and monocular diplopia. This partnership between the doctor and patient becomes solidified when the remediation results in meeting the patient’s expectations.

Management of the patient through the orthokeratology fitting is equally as important as the fitting itself. Making sure the patient is visually and physically comfortable through the adaptation period will assure the patient that the procedure is proceeding as expected. The option of using soft lenses after the first night until the prescription is neutralized gains confidence in the patient that his daily routines will not be compromised by the procedure. Discussing the problems created by the orthokeratology effects and offering solutions will maintain the confidence within the patients that the visual goals can be attained. Informing the patient every step through the process uncovers all the unexpected outcomes the patient might experience.

Orthokeratology represents a technique that temporarily removes the prescription during the patients active waking hours without the risk of refractive surgery. Patients experience the same excitement the first day after lens wear as the first post-op day after surgery. Fitting patient’s with the orthokeratology procedure is a technique that enhances life by alleviating the need of a visual device during waking hours.

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