Complex Case Of Toric Iols Calculation After Deep Corneal Thermocoagulation.

Introduction: Intraocular lens calculation is one of the most important stages of surgical preparation of patients for cataract surgery, as the quality of vision depends on the correctly selected lens.

Historical background: Deep thermocoagulation for hypermetropia correction involves the application of radial point coagulates around the periphery of the cornea. The temperature caused the collagen fibers of the cornea to contract at the site of influence, which led to a change in the shape of its anterior surface, that is, an increase in the radius of curvature at the periphery and a decrease in the radius of curvature at the center, resulting in an increase in its optical power.

Case report: Patient A. presented to our clinic on May 6, 2022, with complaints of low vision that had not been corrected by glasses for a year.  During biomicroscopy of the anterior segment of the eye, circular stromal opacities were identified in the paraoptic zone of the cornea (photo below).

The patient reported having undergone surgery in Moscow (Russia) in 1990 to get rid of glasses, but no supporting medical documentation was available. Since 2000, the patient has been using glasses again.

Materials and Methods:

Visual acuity: OD-6/75sph-1.25 cyl-2.5 ax6=6/30; OS-6/100n/с
The diagnosis was established as Age-related nuclear sclerotic cataract, myopic astigmatism, and a history of thermocoagulation of the cornea in both eyes.

The intraocular lens calculation was performed using:
Since we had no experience with such calculations, emphasis was placed on the parameters obtained from the Holladay EKR Detail Report in the 4.5 mm zone.

The calculation for the right eye was performed using the BARRETT TORIC CAL.: 16.0 S.E (Biconvex) SN6AT3 -0.08 S.E ax 87° - based on the IOL Master 500 data and 16.5 D SN6AT3 93° +0.16 D X 93° - based on the Holladay EKR Detail Report in the 4.5 mm zone. On the first postoperative day, we obtained a refraction of REF: sph+0.75 cyl -1.25 ax 160°.The lens was recalculated based on all available examinations. The Tot.Refr.Power was the most stable indicator and the most accurate approach for the refractive results of the right eye. Taking into account the previous calculation, the left eye was calculated based on Tot.Refr.Power.

The left eye calculation was 20.5 SN6AT4 -0.39 S.E. based on the Holladay EKR Detail Report and 20.5 SN6AT4 -0.13 S.E. based on Tot. Refr. Power.
Surgical technique: Uncomplicated small incision cataract surgery with toric IOLs implantation in both eyes was performed using the Stellaris phaco machine with standard settings and tunnel incisions in the steep meridians. The postoperative period was uneventful.

Results:
Visual acuity at the one-month follow-up:
Right eye - 6/8 REF: sph+0.25 cyl -1.25 ax 160° = 6/6
Left eye - 6/6

Conclusion:
The presented case demonstrates that successful treatment requires a comprehensive and balanced approach. The use of different methods and approaches to calculating IOL, taking into account individual characteristics and patient interaction, allowed for the expected outcome to be achieved. The proposed IOL calculation for similar patients provides, in our opinion, a more precise and effective surgical treatment.