contact lens management

Correct Corneal Irregularities

Specialty lens for post-LASIK patients

Mile Brujic, O.D.

A 49-year-old white female presented complaining of “fuzzy vision,” which she said she had since undergoing LASIK 10 years ago. She said her vision was worse at night than during the day.

Exam findings

Her refractive error was OD -0.25-1.00 x 094 20/20 and OS plano 20/20. Although the patient saw 20/20 OU, her visual quality was poor. Keratometry readings were OD 40.00/39.75@070/160 and OS 39.12/39.50@047/137. Topography revealed a classic post-LASIK corneal pattern (see Figure 1, below). Anterior segment exam was remarkable for a circular scar around the treatment zone OU. All other ocular findings were normal.

Figure 1. Topography images of the patients' right and left corneas. Small central flattened zones are evident in the topographies.

I diagnosed this patient with post-LASIK-induced corneal irregularities.

Discussion

Those with an unsuccessful refractive surgery outcome experience a decreased best-corrected visual acuity, unstable refractive errors and un-resolving glare under dim conditions.^1,2,3

Glare may be one of the most common complaints of these patients. When the pupils dilate under dim illumination, areas of the cornea not usually contributing to the visual image quality entering the pupil now affect it. This is due to the large pupil exposing now irregular areas of the cornea. The result: possible increased aberrations.

The good news: Three treatments exist to correct the aforementioned vision problems:

(1) Custom free-form ophthalmic lenses (i.Scription-Zeiss, iZon-Ophthonix, Inc. and Encepsion-VMax). These are created from wavefront spectacle systems that correct to a higher level than standard phoropters and ophthalmic lenses. (See “End Aberration Aggravation,” page 37 of the June 2012 issue.)

(2) Brimonidine tartrate. This alpha 2 adrenergic agonist molecule, available in 0.1%, 0.15%, and 0.2% solutions, acts on the presynaptic terminal of the adrenergic synapse of the iris dilator muscle, inhibiting the release of norepinephrine, which minimizes pupil dilation.^4,5 (Pilocarpine and Dapiprazole drops constrict the pupil, though their side effects, such as stimulating accommodation and the potential for ocular hyperemia, respectively, often limit their use.

(3) A reverse geometry design contact lens. This lens is flatter in the center than in the periphery, allowing it to follow the architecture of the post-refractive surgery cornea and, thus, correct poor-visioncausing corneal irregularities.

If you note lid attachment and significant movement upon fitting, the reverse geometry lens is likely loose. If you see little movement and the lens fits low on the cornea, it is likely too tight, and a flatter base curve is required. The ideal lens fit: When the lens beyond the reverse curve is tangential to the cornea on which it rests. The ideal fluorescein pattern under the reverse geometry lens mimics that of an aligned fit of a traditional RGP lens on a regular cornea. You'll usually see a light fluorescein pattern where the reverse curve is located on the lens' posterior surface, but it won't be as prominent as the pooling pattern seen when fitting orthokeratology lenses. This is completely normal.

Management

After prescribing free-form ophthalmic lenses and then brimonidine tartrate 0.15% with no success, I fit the patient in reverse geometry lenses (e.g. OD 8.20 central /7.50 peripheral/-4.00/10.0 diameter, OS 8.2 central /7.50 peripheral/-4.25/10.0 diameter).

Practice benefits

One of the best strategies to optimizing practice success is successfully meeting our patients' visual needs. By understanding reverse geometry lenses and how they can improve a patients' visual quality, you'll be certain to exceed patient expectations. This will inherently lead to a loyal patient base that results in a more profitable practice.

Outcome

The patient's vision with the lenses is OD 20/20, OS 20/20. At her last followup appointment, she said the lenses have continued to provide her with the clearest vision she has had in years. OM

1. Marinho A, Pinto MC, Pinto R, et al. LASIK for high myopia: one year experience. Ophthalmic Surg Lasers. 1996 May;27(5 Suppl):S517-20.
2. Helena MC, Meisler D, Wilson SE. Epithelial growth within the lamellar interface after laser in situ keratomileusis (LASIK). Cornea. 1997 May;16(3):300-5.
3. Buratto L, Ferrari M. Indications, techniques, results, limits, and complications of laser in situ keratomileusis. Curr Opin Ophthalmol. 1997 Aug;8(4):59-66.
4. McDonald JE 2nd, El-Moatassem Kotb AM, Decker BB. Effect of brimonidine tartrate ophthalmic solution 0.2% on pupil size in normal eyes under different luminance conditions. J Cataract Refract Surg. 2001 Apr;27(4):560-4.
5) Kesler A, Shemesh G, Rothkoff L, Lazar M. Effect of brimonidine tartrate 0.2% ophthalmic solution on pupil size. J Cataract Refract Surg. 2004 Aug;30(8):1707-10.