Study of Phacodepth Required for Safe and Effective Chop During Phacoemulsification for Cataract. (CALIBCHOP)

Evaluation of Phacodepth Required to Achieve Full Thickness Nuclear Crack in Various Grades of Cataract and to Determine the Correlation Between the Two.

There is a correlation between phacodepth required for full thickness nuclear crack and the various grades of cataract

Study Overview

• Status: Completed
• Conditions: Cataract

Detailed Description

BACKGROUND:- Phacochop techniques have been categorized as either horizontal or vertical. These approaches are thought to be among the best techniques for managing hard cataracts. In vertical chop technique proper placement of the phaco tip is crucial. It must be embedded deeply into the centre of the nucleus , pointing toward the optic nerve , with high vacuum and burst mode.Inadequate penetration of phacotip may result in partial thickness nuclear crack with residual posterior plate and overzealous penetration may result in posterior capsular rupture.This may be avoided if some estimate can be made preoperatively of the depth of penetration required to achieve full thickness crack. With this in mind the study intends to make a preoperative assessment of the depth required to reach the centre of the nuclei and observe the actual depth of penetration required for a safe and effective vertical chop.

MATHEMATICAL BASIS :- The cross section of a lens nucleus is ellipsoidal . A geometrical estimate of the radius of the ellipse (x )traversed by the phacotip to reach the centre can be made preoperatively.The calculation would depend largely on three parameters.

The major axis of the ellipse ( namely the lens diameter[b] ) The minor axis of the ellipse (namely lens thickness[a] ) The point of entry on the surface of the lens.This defines an angle Ø which this radius makes with the vertical axis and in turn can be approximated by the length of the arc from centre of lens surface to entry point[y].

Adult human crystalline lens varies in thickness from 4.2+/-0.5 mm and has a diameter of 9.6+/- 0.4mm. Assuming the lens diameter (b) to be from 9.2 mm to 10.0mm , the lens thickness ( a) varying from 3.7mm to 4.7mm and the point of entry of phacotip 2.0mm to 3.0mm from centre of anterior lens surface ( y ) , this distance (x) would vary from 2.59mm to 3.2mm.(using Online Wolfram calculator) in thinnest to thickest nuclei. This would be increased with increase in ( a ) as well as ( y ) .In cataractous lens the harder a nucleus the deeper it may be required to penetrate to achieve a full thickness crack.

If the investigators make a note of all three variables i.e lens thickness , nuclear hardness and point of entry at the time of surgery and correlate with the actual depth required at the time of surgery the investigators may be able to recommend an effective and safe phacodepth for achieving full thickness nuclear crack in various grades of hard cataract.

Till now it was not possible to measure the length of penetration of phacotip during surgery. The investigators have designed a calibrated phacotip with visible markings on 0.2mm scale from 2 to 3. 4mm to enable measurements and recordings.

Thus the investigators aim to identify a safe and effective phacodepth required in each grade of cataract {3.0 - 6.9 according to Lens Opacities Classification System( LOCS-III )}to achieve successful nuclear crack . At the same time any correlation between different nuclear grades and the effective phacodepth would be analysed to find any association between them.

• Study Type: Observational
• Enrollment (Actual): 200

Contacts and Locations

Study Locations

• India
  • Delhi
    • New Delhi, Delhi, India, 110001
      • Dr. R.M.L.Hospital,

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 40 years and older (ADULT, OLDER_ADULT)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

The study will be conducted at EYE DEPARTMENT, Post Graduate Institute of Medical Education and Research(PGIMER) , Dr R.M.L Hospital.

A consecutive sample of all eyes with cataract reporting to the eye OPD of Dr. R.M.L.Hospital and fulfilling the inclusion criteria, would be enrolled in the study starting a date following ethics committee approval till March 2011 ,after a written informed consent.

Description

Inclusion Criteria:

• Patients (> 40 years of age) with grade 3.0 to 6.9( according to LOCS-III) of senile cataract will be included in this study

Exclusion Criteria:

1. Subluxated and dislocated lens.
2. Central leukomatous corneal opacity preventing visualization of cataractous lens for grading and surgery.

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Phacodepth Required to Achieve Full Thickness Nuclear Crack	phacodepth is the term used to describe the depth penetrated by the phacotip into the substance of lens.A note of depth penetrated by the tip to achieve full thickness nuclear crack shall be made.	day 0 of surgery
Correlation Between Nuclear Colour and Phacodepth Required for a Safe and Effective Vertical Chop During Phacoemulsification	the nuclear colour grading as per LOCS III criteria for each case and the depth of penetration of phacotip required during a vertical chop was analysed to look for any correlation between the two.	day 0 of surgery
Correlation Between Nuclear Opalescence and Phacodepth	Pearson correlation coefficient would be calculated to look for any correlation between; nuclear opalescence as per LOCS III grading system for each cataract and; penetration of phacotip required to achieve a full thickness nuclear crack in vertical chop during phacoemulsification of the cataractous lens	day 0 of surgery
Correlation Between Lens Thickness and Phacodepth	Pearson correlation coefficient would be calculated to look for any correlation between; length thickness measurement using A scan biometer for each cataract and; penetration of phacotip required to achieve a full thickness nuclear crack in vertical chop during phacoemulsification of the cataractous lens	day 0 of surgery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Posterior Capsular Rupture	A note shall be made of any posterior capsular rupture attributable to the attempted vertical chop .	day 0 of surgery.

Collaborators and Investigators

• Sponsor: Dr. Ram Manohar Lohia Hospital
• Investigators: Principal Investigator: Praveen K Malik, MS, Dr. R.M.L.Hospital,New Delhi,India

Study record dates

Study Major Dates

• Study Start: November 1, 2010
• Primary Completion (ACTUAL): January 1, 2011
• Study Completion (ACTUAL): February 1, 2011

Study Registration Dates

• First Submitted: December 7, 2010
• First Submitted That Met QC Criteria: December 8, 2010
• First Posted (ESTIMATE): December 9, 2010

Study Record Updates

• Last Update Posted (ESTIMATE): August 16, 2012
• Last Update Submitted That Met QC Criteria: July 7, 2012
• Last Verified: July 1, 2012

More Information

Terms related to this study

• Keywords: phacoemulsification; cataract; phacochop; phacotip
• Additional Relevant MeSH Terms: Eye Diseases; Lens Diseases; Cataract
• Other Study ID Numbers: RMLH-001-EYE