The benefit of early iris transillumination detection: A message to refractive surgeons
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Long-term undiagnosed pigmentary dispersion syndrome can lead to visual disasters. Here, we hope to provide some guidelines for earlier diagnosis and treatment.
We believe that every LASIK patient should be evaluated with central high-intensity pupillary illumination to look for iris transillumination. This started when the senior author’s favorite mentor at Temple University department of ophthalmology was sued by an attorney who had lost significant vision in less than 6 months due to advanced pigmentary dispersion syndrome (PDS), the result of an acutely progressive pigmentary glaucoma (PG). This precipitated medical liability litigation and a lost lawsuit by his mentor. It was traumatic for the author and increased his sensitivity for this syndrome.
The senior author has had a lifelong concern about the early diagnosis of PG. He witnessed this firsthand with the litigating attorney who won his medical liability suit. The author had seen these impressive transillumination defects and hyperpigmented trabecular meshwork, which were burned into his memory. He was thus sensitized to carefully looking for iris transillumination ever since. He found it more frequently than it seemed to be reported. He came to realize that he saw large populations of younger patients presenting for LASIK who, in passing, he transilluminated. This hypervigilance led to earlier diagnoses of PDS and an interest in early treatment.
Recently, a patient in their early 20s came for a LASIK evaluation with the perfect findings that illustrate the early transillumination defects that are occasionally present in our LASIK population. There are just a few dots of transillumination (Figure 1). These are the type of defects that refractive surgeons and those caring for younger populations might screen for in the hopes of heading off possible PG. Our practice utilizes an anterior chamber OCT and gonioscopy when any transillumination is detected, from mild to severe (Figures 1 and 2); both are important for the detection and prevention of PDS and PG.
The early detection of PDS is important. Although there are no long-term definitive studies in the use of laser peripheral iridotomy (LPI) to treat PDS, the authors feel that early LPI may avoid the complications of elevated IOP and glaucoma damage in some patients.
Because of our earlier experiences, everyone in the practice has been trained to always look for iris transillumination. Early clues such as subtle peripheral inferior iris transillumination or pigment cells in the anterior chamber are indicators of this problem. Because of our younger population of high myopia, we recognized these subtle forms of PDS and found PDS more often and earlier.
PDS is defined as the dispersion of iris pigments from the iris pigment epithelium. It is hypothesized that the main mode of dispersion is a consequence of mechanical friction between the retropulsed iris pigment epithelium and the lens. The hypothesis was supported with scanning electron microscopy. Common risk factors such as moderate myopia and a deep chamber favor friction. PG can result when pigment blocks the proper drainage of the aqueous humor within the trabecular meshwork, thereby increasing IOP.
Anterior segment OCT has given us the opportunity to see high-resolution, cross-sectional tomographic imaging of the anatomical relationship between the iris and the lens. This provides precise cross-sectional anterior chamber measurement of the position of the iris in relation to the cornea and human lens. With the use of OCT, we can establish a baseline for the quantification of the anterior chamber angle anatomy.
There are reports of using LPI to treat PG. There are short-term studies of LPI and PG that possibly do not address the earliest diagnosis and long-term effects of PDS and the early treatment of LPI. Such studies examine patients with ocular hypertension and pigment dispersion already present, and the study only follows patients for a 3-year duration after LPI. We feel by gathering young patients at the earliest stages of PDS and doing a long-term analysis of LPI may lead to different results. We are calling upon our refractive surgeons to carefully look for transillumination defects for this reason. There is little research performed on the effects of LPI on PG and its abnormally retropulsed anterior chamber angle. Surgeons note that with angle-closure glaucoma, LPI causes a spontaneous flow of aqueous from the posterior anteriorly with a shower of pigment coming forward. When LPI is performed on PDS, the flow goes posteriorly, demonstrating an unusual aqueous dynamic. This is opposite of the usual dynamic in angle-closure glaucoma when the fluid comes anteriorly. We are considering a long-term registry to view the course of this disease over multiple decades to get more accurate clinical findings.
Initially being a cataract surgery practice, the average patient age decreased once LASIK became more prevalent, as correcting refractive error played a larger role in this patient population. As we continued to look for iris transillumination in these younger patients, we found PDS at a higher-than-expected rate and noted extreme forms that resulted in LPI with the resultant confirmatory aqueous flow characteristics of PDS. Refractive surgeons have the opportunity to avoid devasting effects of glaucoma, specifically PG, by discovering PDS early and treating it differently than we have in the past.
An analysis of the anterior chamber before LPI demonstrates a retroflexed iris (Figure 3). Two weeks after, a YAG LPI was performed, and the patient returned for additional OCT testing (Figure 4). This showed elimination of the retroflexed iris and a return to a normal position.
It seems that it is important to do an LPI before doing LASIK as the lens position affects the refractive power of the eye. Because the lens moves forward after LPI, the eye becomes myopic. In this case, we learned that lesson. Utilizing a WaveScan before and after LPI, our patient had a 76% change in the right eye’s spherical measurement (–0.71 D to –1.24 D). The left eye’s spherical measurement experienced an 18% change (–0.93 D to –1.1 D). It is important to note that the patient discussed increased blurriness and visual change after the LPI. This patient needed an enhancement correction following LPI.
With this in mind, we are interested in the experience of our colleagues as we alert them to this problem, which needs further study and evaluation. By alerting our fellow refractive surgeons to look for iris transillumination, we might better understand this disease and its progression as a side benefit to improving the vision of our patients.
This article is to help our refractive colleagues and general ophthalmologists to evaluate young patients more carefully for iris transillumination and PDS, which is felt to occur at a higher and earlier rate with myopic patients. Hopefully, we can go on to produce statistical evidence for our hypothesis with the aid of our colleagues.
- References:
- Peterson JR, et al. J Glaucoma. 2017;doi:10.1097/IJG.0000000000000731.
- Ritch R. Trans Am Ophthalmol Soc. 1996;94:381-405.
- Scott A, et al. Ophthalmology. 2011;doi:10.1016/j.ophtha.2010.07.026.
- Zeppieri M. J Clin Transl Res. 2022;doi:10.18053/jctres.08.202205.004.
- For more information:
- Blake Greenspan, research assistant and ophthalmic technician at Siepser Laser Eyecare in Wayne, Pennsylvania, can be reached at bgreenspan@siepservision.com.
- Steven B. Siepser, MD, of Siepser Laser Eyecare in Wayne, Pennsylvania, can be reached at ssiepser@siepservision.com.
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